Darwin's frog: Difference between revisions
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Darwin’s frog (Rhinoderma darwinii), also called the '''southern Darwin's frog''',<ref name="SearsSoto-Azat2013">{{cite journal |last1=Soto-Azat |first1=Claudio |last2=Valenzuela-Sánchez |first2=Andrés |last3=Clarke |first3=Barry T. |last4=Busse |first4=Klaus |last5=Ortiz |first5=Juan Carlos |last6=Barrientos |first6=Carlos |last7=Cunningham |first7=Andrew A. |year=2013 |title=Is Chytridiomycosis Driving Darwin's Frogs to Extinction? |journal=PLOS One |volume=8 |issue=11 |pages=e79862 |doi=10.1371/journal.pone.0079862 |issn=1932-6203 |pmc=3835940 |pmid=24278196 |doi-access=free}}</ref> is a species of Chilean/Argentinian frog of the family [[Rhinodermatidae]]. It was discovered by [[Charles Darwin]] during his voyage on [[The Voyage of the Beagle|voyage on HMS ''Beagle'']].<ref name="Darwin1843">{{cite book |last=Bell |first=Thomas |url=https://books.google.com/books?id=Q3k3AQAAMAAJ |title=The Zoology of the Voyage of H.M.S. Beagle, Part V: Reptiles |publisher=Smith, Elder and Co. |year=1843 |editor=Charles Darwin |location=London |page=48 |authorlink=Thomas Bell (zoologist) |accessdate=1 December 2013}}</ref><ref name="Duméril1841">{{cite book |last1=Duméril |first1=A.M.C. |url=https://www.biodiversitylibrary.org/item/101245#page/679/mode/1up |title=Erpétologie Générale; ou, Histoire Naturelle Complète des Reptiles |last2=Bibron |first2=G. |date=1841 |publisher=Librairie Encyclopédique de Roret |volume=8 |location=Paris |pages=659 |authorlink1=André Marie Constant Duméril |authorlink2=Gabriel Bibron |accessdate=2 December 2013}}</ref><ref name="GratwickeSoto-Azat2013">{{cite journal |last1=Gratwicke |first1=Brian |last2=Soto-Azat |first2=Claudio |last3=Valenzuela-Sánchez |first3=Andrés |last4=Collen |first4=Ben |last5=Rowcliffe |first5=J. Marcus |last6=Veloso |first6=Alberto |last7=Cunningham |first7=Andrew A. |year=2013 |title=The Population Decline and Extinction of Darwin's Frogs |journal=PLOS One |volume=8 |issue=6 |pages=e66957 |doi=10.1371/journal.pone.0066957 |issn=1932-6203 |pmc=3680453 |pmid=23776705 |doi-access=free}}</ref> on a trip to Chile. In 1841, French zoologist [[André Marie Constant Duméril]] and his assistant [[Gabriel Bibron]] described and named Darwin's frog. The diet of R. ''darwinii'' consists mostly of herbivore invertebrates. |
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Darwin’s frog is most known for its unique method of brooding. The male will facilitate development of its [[tadpole]]s' inside its [[vocal sac]]. This male brooding makes Darwin’s frog distinct from all other frogs (as the only other frog that has this behavior is the R. ''rufum'' and it may be extinct). |
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The most striking feature of this frog is the [[tadpole]]s' development inside the [[vocal sac]] of the male. |
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== Characteristics == |
== Characteristics == |
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The upperparts of this species are variably colored in brown or green. Some brown individuals may have weakly defined V-shaped markings on the back, have central upperparts that are distinctly lighter brown than the flanks, or have whitish front limbs. Females are typically brown and tend to stay on substrates that match this color. Males are far more variable and occur on a wider range of substrates; especially brooding males often are partially or completely green above.<ref name=Bourke2011>{{cite journal | author1=Bourke, J. | author2=K. Busse | author3=T.C.M. Bakker | year=2011 | title=Sex differences in polymorphic body coloration and dorsal pattern in Darwin's frogs (Rhinoderma darwinii) | journal=Herpetological Journal | volume=21 | pages=227–234 }}</ref> The throat is brownish and the remaining underparts are black with large white blotches in a pattern that is unique to each individual.<ref name="GratwickeSoto-Azat2013"/><ref name=AmphibiaWeb/> |
The upperparts of this species are variably colored in brown or green. Some brown individuals may have weakly defined V-shaped markings on the back, have central upperparts that are distinctly lighter brown than the flanks, or have whitish front limbs. Females are typically brown and tend to stay on substrates that match this color. Males are far more variable and occur on a wider range of substrates; especially brooding males often are partially or completely green above.<ref name=Bourke2011>{{cite journal | author1=Bourke, J. | author2=K. Busse | author3=T.C.M. Bakker | year=2011 | title=Sex differences in polymorphic body coloration and dorsal pattern in Darwin's frogs (Rhinoderma darwinii) | journal=Herpetological Journal | volume=21 | pages=227–234 }}</ref> The throat is brownish and the remaining underparts are black with large white blotches in a pattern that is unique to each individual.<ref name="GratwickeSoto-Azat2013"/><ref name=AmphibiaWeb/> |
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In captivity, male R. Darwinii have been shown to change color. These frogs that were initially brown changed to green over a year. This change in color is believed to be due to the green color of the environment these frogs were kept in.<ref>{{Cite journal |last=Bourke |first=Johara |last2=Barrientos |first2=Carlos |last3=Ortiz |first3=Juan C. |last4=Busse |first4=Klaus |last5=Böhme |first5=Wolfgang |last6=Bakker |first6=Theo C. M. |date=2011-11-01 |title=Colour change in Darwin's frogs (Rhinoderma darwinii, Duméril and Bibron, 1841) (Anura: Rhinodermatidae) |url=https://doi.org/10.1080/00222933.2011.597885 |journal=Journal of Natural History |volume=45 |issue=43-44 |pages=2661–2668 |doi=10.1080/00222933.2011.597885 |issn=0022-2933}}</ref> |
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[[File:Ranita de Darwin (Rhinoderma darwinii).jpg|thumb|Most green individuals are brooding males<ref name=Bourke2011/>]] |
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== Distribution and habitat == |
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Darwin's frog feeds on insects and other [[arthropod]]s. It not only has to hunt, but also needs to hide from its [[predation|predators]]. It relies on [[camouflage]] to avoid predators, lying on the ground [[mimicry|looking like a dead leaf]] until the predator passes by. Another defensive position is turning on the back and exposing the [[warning coloration|boldly patterned]] ventral surface.<ref name=AmphibiaWeb/> |
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| ⚫ | Darwin's frog is found in [[Chile]] and [[Argentina]]. In Chile, its range extends from [[Concepción Province, Chile|Concepción Province]] to [[Palena Province]] and in Argentina from [[Neuquén Province]] and [[Río Negro Province]]. It is found in glades and forested areas at altitudes of up to about {{convert|1100|m|abbr=on}} above mean sea level.<ref name="iucn status 20 November 2021" /> It is also found in bogs and near slow-moving streams. It is found in a variety of vegetation types and it appears that a mixture of grassland, mossy areas, coarse woody debris, and young trees and bushes in a mature native forest provides its optimum habitat requirements. Short vegetation increases the retention of water while decreasing the temperature of the soil and provides concealment from predators. The population is fragmented and this frog has poor dispersal ability.<ref name="SearsSoto-Azat2013" /> |
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== Behavior == |
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R. ''darwinii'' exhibit rare behavior in terms of territoriality and parental care. In anuran species, parental care and territoriality are positively related. In R. ''darwinii'', there is high parental care due to the ingestion of tadpoles by fathers. However, there is low territoriality exhibited by these R. ''darwinii'' males. In fact, neither females nor males of R. ''darwinii'' have been observed guarding eggs. These observations of R. ''darwinii'' were used to further develop the relationship between territoriality and parental care by establishing the role of oviposition defense. These observations suggest that anurans will exhibit territoriality with parental care if they defend oviposition sites. <ref>{{Cite journal |last=Valenzuela‐Sánchez |first=A. |last2=Harding |first2=G. |last3=Cunningham |first3=A. A. |last4=Chirgwin |first4=C. |last5=Soto‐Azat |first5=C. |date=2014-12 |title=Home range and social analyses in a mouth brooding frog: testing the coexistence of paternal care and male territoriality |url=https://onlinelibrary.wiley.com/doi/10.1111/jzo.12165 |journal=Journal of Zoology |language=en |volume=294 |issue=4 |pages=215–223 |doi=10.1111/jzo.12165 |issn=0952-8369}}</ref> |
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== Diet == |
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Rhinoderma ''darwinii's'' diet consists of detritivore, herbivore, and carnivore invertebrates. It does not seem to have a preference regarding which type of invertebrate. It is observed to consume each type of invertebrate at a percentage consistent with their existence in the environment. The percentage at which carnivorous invertebrates are consumed is lower than herbivore or detritivore invertebrates. This difference can be explained because spiders are the predominant type of carnivore invertebrate prey that R. ''darwinii'' encounters. These spiders are able to evade the predation of R. ''darwinii'' effectively due to their evasion ability. |
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| ⚫ | Darwin's frog is found in [[Chile]] and [[Argentina]]. In Chile, its range extends from [[Concepción Province, Chile|Concepción Province]] to [[Palena Province]] and in Argentina from [[Neuquén Province]] and [[Río Negro Province]]. It is found in glades and forested areas at altitudes of up to about {{convert|1100|m|abbr=on}} above mean sea level.<ref name="iucn status 20 November 2021" /> It is also found in bogs and near slow-moving streams. It is found in a variety of vegetation types and it appears that a mixture of grassland, mossy areas, coarse woody debris, and young trees and bushes in a mature native forest provides its optimum habitat requirements. Short vegetation increases the retention of water while decreasing the temperature of the soil and provides concealment from predators. The population is fragmented and this frog has poor dispersal ability.<ref name="SearsSoto-Azat2013"/> |
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In the habitats where R. ''darwinii'' have been observed, there seem to be relatively high percentages of herbivore invertebrates. This could mean that R. ''darwinii'' seek environments with enriched herbivore invertebrates as a food source. <ref>{{Cite journal |last=Molina-Burgos |first=B. E. |last2=Valenzuela-Sánchez |first2=A. |last3=Alvarado-Rybak |first3=M. |last4=Klarian |first4=S. |last5=Soto-Azat |first5=C. |date=2018 |title=Trophic ecology of the Endangered Darwin’s frog inferred by stable isotopes |url=https://doaj.org/article/b49681e965e74ffd9e9f1f7e5cf9c4c8 |language=English}}</ref> |
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R. ''darwinii'' style of predation has been characterized as “sit and wait.” This method seems to conserve energy and allows R. ''darwinii'' to evade [[predation|predators]] effectively. |
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Male R. ''darwinii'' will call to attract females in an attempt to mate. It has even been shown that male R. darwinii will call even when brooding. However, no brooding males have been observed copulating with females. R. ''darwinii'' use non-linear vocal phenomena (NLP) in order to attract and communicate with mates. Darwin’s frog have been shown to have distinct mating patterns based on population and body size. More research needs to be conducted in order to further explore the mating of R. ''darwinii''.<ref>{{Cite journal |last=Serrano |first=José M. |last2=Penna |first2=Mario |last3=Soto-Azat |first3=Claudio |date=2020-09-02 |title=Individual and population variation of linear and non-linear components of the advertisement call of Darwin’s frog (Rhinoderma darwinii) |url=https://doi.org/10.1080/09524622.2019.1631214 |journal=Bioacoustics |volume=29 |issue=5 |pages=572–589 |doi=10.1080/09524622.2019.1631214 |issn=0952-4622}}</ref>[[File:Ranita de Darwin (Rhinoderma darwinii).jpg|thumb|Most green individuals are brooding males<ref name=Bourke2011/>]] |
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== Parental Care == |
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The female Darwin's frog lays up to forty [[Egg (biology)|eggs]] among the leaf litter. Females will generally lay 4-10 eggs. Males can brood 5-8 tadpoles at a time. |
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| ⚫ | The male, after about three to four weeks, notices the developing [[Embryo|embryos]] beginning to move, and then he ingests the eggs and holds them in his vocal sac. They hatch about three days later and he continues to carry the tadpoles around in his vocal sac where they feed off their egg yolks and secretions produced by the wall of the sac until [[metamorphosis]]. At this stage, about 6 weeks after being swallowed, while previous authors believed that during this period the adult male eats nothing, G B Howes, in 1888, dissected a brooding male and found its stomach full of beetles and flies and its large intestine clogged with "excreta like that of a normal individual." He concluded "that this extraordinary paternal instinct does not lead up to that self-abnegation". Following this, the small frogs hop out of the male's mouth and disperse. |
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In captivity, R. ''darwinii'' parents have been observed to leave the eggs unattended for around 3 weeks (some R. ''darwinii'' males will guard the eggs for these 3 weeks). Further, captive males have been shown to exhibit alloparental behavior. Foster males have been shown to take a defensive stance at the eggs (oviposition defense). They will go so far as to defend the eggs from the birth father of the eggs and will subsequently brood the kin of other males. In this specific experiment the foster father ingested 8 tadpoles, and after brooding had been completed, the foster father produced 2 frogs. This means that the metamorphosis process is not 100% efficient.This observation is consistent across studies and there exist some proposed explanations for the alloparental behavior. This alloparental behavior is especially rare among amphibians. |
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Two hypotheses for this behavior have been proposed: |
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# The first hypothesis is that foster fathers can improve upon their brooding skills by practicing. Improved brooding skills would result in males that can propagate more of their genes into the next generation. |
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# The second hypothesis is that foster fathers can exhibit that they have had past breeding success by brooding tadpoles that aren't theirs. This means that these foster fathers are hoping that future mates will see them brooding and be more likely to mate with them. |
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These hypotheses propose ideas in which there is some advantage for males who brood offspring that are not theirs. |
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The loss of some tadpoles in the metamorphosis from tadpole to frog is a unique feature of R. ''darwinii''. This observation is likely explained by these hypotheses: |
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# The tadpoles that didn’t survive were converted into nutrition for the foster male and he digested them. |
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# The tadpoles died in the vocal sac of the foster male. The nutrients from these dead tadpoles served as sustenance for the surviving tadpoles occupying the vocal sac of the foster male. This phenomenon of one embryo consuming another is termed adelphophagy. The vocal sac of R. ''darwinii'' does not seem to have the proper structure to facilitate adelphophagy and thus this proposal is unlikely to explain the incomplete metamorphosis observed. <ref>{{Cite web |title=X-MOL |url=https://en.x-mol.com/paper/article/1431001998362918912 |access-date=2022-10-12 |website=en.x-mol.com}}</ref> |
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== Enemies == |
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R. ''dawrinii'' have been shown to be highly susceptible to [[Batrachochytrium dendrobatidis]] infection.<ref>{{Cite journal |last=Valenzuela‐Sánchez |first=Andrés |last2=Azat |first2=Claudio |last3=Cunningham |first3=Andrew A. |last4=Delgado |first4=Soledad |last5=Bacigalupe |first5=Leonardo D. |last6=Beltrand |first6=Jaime |last7=Serrano |first7=José M. |last8=Sentenac |first8=Hugo |last9=Haddow |first9=Natashja |last10=Toledo |first10=Verónica |last11=Schmidt |first11=Benedikt R. |last12=Cayuela |first12=Hugo |date=2022-02 |title=Interpopulation differences in male reproductive effort drive the population dynamics of a host exposed to an emerging fungal pathogen |url=https://onlinelibrary.wiley.com/doi/10.1111/1365-2656.13603 |journal=Journal of Animal Ecology |language=en |volume=91 |issue=2 |pages=308–319 |doi=10.1111/1365-2656.13603 |issn=0021-8790}}</ref> The amphibian disease [[chytridiomycosis]], caused by [[Batrachochytrium dendrobatidis]] [[Mycosis|fungal infection]], is also a probable factor, "particularly from the northern part of their historical range". Populations on [[Chiloé Island]] were found to be considerably more abundant than on the mainland. |
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R. ''darwinii'' seems to be less affected by [[chytridiomycosis]] when compared to other amphibians. However, Chytridiomycosis can still infect and kill R. ''darwinii''. Previous studies have supported the idea that [[chytridiomycosis]] could be somewhat responsible for the decrease in R. ''darwinii'' population exhibited in Chile and Argentina. <ref>{{Cite journal |last=Soto-Azat |first=Claudio |last2=Valenzuela-Sánchez |first2=Andrés |last3=Clarke |first3=Barry T. |last4=Busse |first4=Klaus |last5=Ortiz |first5=Juan Carlos |last6=Barrientos |first6=Carlos |last7=Cunningham |first7=Andrew A. |date=2013-11-20 |title=Is Chytridiomycosis Driving Darwin’s Frogs to Extinction? |url=https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0079862 |journal=PLOS ONE |language=en |volume=8 |issue=11 |pages=e79862 |doi=10.1371/journal.pone.0079862 |issn=1932-6203 |pmc=PMC3835940 |pmid=24278196}}</ref> |
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In recent years, studies have shown that R. ''darwinii'' have shown variation in [[Batrachochytrium dendrobatidis]] infection across populations. In populations where there was high Bd infection rates, there are observed to be higher population growth rates. Similarly, in populations with low Bd infection rates, there are observed to be lower population growth rates. Populations with higher Bd infections rates seemed to have the highest reproductive rates. This means that even though many individuals are dying of Bd infection, there are more individuals being born. There exists a positive relationship between Bd infection rate and the number of juvenile individuals for R. ''darwinii''.<ref>{{Cite journal |last=Valenzuela-Sánchez |first=Andrés |last2=Azat |first2=Claudio |last3=Cunningham |first3=Andrew A. |last4=Delgado |first4=Soledad |last5=Bacigalupe |first5=Leonardo D. |last6=Beltrand |first6=Jaime |last7=Serrano |first7=José M. |last8=Sentenac |first8=Hugo |last9=Haddow |first9=Natashja |last10=Toledo |first10=Verónica |last11=Schmidt |first11=Benedikt R. |last12=Cayuela |first12=Hugo |date=2022-02 |title=Interpopulation differences in male reproductive effort drive the population dynamics of a host exposed to an emerging fungal pathogen |url=https://pubmed.ncbi.nlm.nih.gov/34704260/ |journal=The Journal of Animal Ecology |volume=91 |issue=2 |pages=308–319 |doi=10.1111/1365-2656.13603 |issn=1365-2656 |pmid=34704260}}</ref> |
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This odd feature of Bd infection and R. ''darwinii'' population growth prompted further investigation. The explanation for this observation is termed the “parasite-induced plasticity” hypothesis. This hypothesis says that individuals will devote more resources towards reproduction as opposed to survival. This increased devotion towards reproduction takes place over a single generation. This plasticity is beneficial to the infected individual because the infection will take over at some point so until that point the individual will try to have as many offspring as possible.<ref>{{Cite journal |last=Hardy |first=Bennett M. |last2=Muths |first2=Erin |last3=Koons |first3=David N. |date=2022-02 |title=Context‐dependent variation in persistence of host populations in the face of disease |url=https://onlinelibrary.wiley.com/doi/10.1111/1365-2656.13654 |journal=Journal of Animal Ecology |language=en |volume=91 |issue=2 |pages=282–286 |doi=10.1111/1365-2656.13654 |issn=0021-8790}}</ref> |
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== Population decline and conservation status == |
== Population decline and conservation status == |
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Darwin's frog has undergone significant population declines due to habitat loss and degradation, largely from conversion of native forests to [[Plantation|tree plantations]]. |
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Darwin's frog has undergone significant population declines due to habitat loss and degradation, largely from conversion of native forests to [[plantation|tree plantations]]. The amphibian disease [[chytridiomycosis]], caused by ''[[Batrachochytrium dendrobatidis]]'' [[mycosis|fungal infection]], is also a probable factor, "particularly from the northern part of their historical range". Populations on [[Chiloé Island]] were found to be considerably more abundant than on the mainland.<ref name="SearsSoto-Azat2013">{{cite journal|last1=Soto-Azat |first1=Claudio |last2=Valenzuela-Sánchez |first2=Andrés |last3=Clarke |first3=Barry T.|last4=Busse |first4=Klaus|last5=Ortiz |first5=Juan Carlos |last6=Barrientos |first6=Carlos |last7=Cunningham |first7=Andrew A.|title=Is Chytridiomycosis Driving Darwin's Frogs to Extinction?|journal=PLOS One |volume=8 |issue=11 |year=2013 |pages=e79862 |issn=1932-6203 |doi=10.1371/journal.pone.0079862 |pmid=24278196 |pmc=3835940|doi-access=free }}</ref> |
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| ⚫ | Since 2018, the species is classified as Endangered on the [[IUCN Red List]]. A 2013 study reported results of a population survey conducted from 2008–2012, which found the species at just 36 of 223 previously recorded habitat sites, with small populations at those sites. The recent change in its conservation category in IUCN from Vulnerable to Endangered, arose from the Chile's amphibian reevaluation workshop for the Red List (Soto-Azat et al., 2015). The justification for its current category is due to its limited occupation area (estimated at 264 km2), severe fragmentation of its populations and continued decline. |
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Due to its decline in the wild, captive colonies have been established as a precaution at two zoos in Chile, the [[Chilean National Zoo|National Zoo]] (working with the US [[Atlanta Botanical Garden]]) and [[Concepción Zoo]] (working with the [[University of Concepción]] and Germany's [[Leipzig Zoo]]). |
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The habitat of R. ''darwinii'' is known as the Valdivian temperate rainforest. The Valdivian is decreasing in the north due to pine and eucalyptus agriculture expansion. This is removing some of the habitat of R. ''darwinii'' and forcing them south. The south Valdivian is more protected and is suitable for R. ''darwinii'' habitance. |
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In 2017, the IUCN SSC Amphibian Specialist Group formed a Binational Conservation Strategy that brought together 30 different countries. The goal of this group is to study Rhinoderma ''darwinii'' in order to improve conservation efforts. The group details the unique characteristics (mouth brooding) as one justification for this increased conservation effort. The goal of the group is to understand key aspects of information related to Rhinoderma ''darwinii'' by the year 2028. |
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Dispersal-constrained species distribution models have shown a decrease of up to 40% in habitat for R. ''darwinii'' over the years 1970 to 2010. The habitat for R. ''darwinii'' is expected to increase in the coming years. However, this emerging habitat is not likely to be habited by R. ''darwinii'' due to its inability to translocate to these new habitats. |
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Climate change is also expected to play a role in the habitat availability of R. ''darwinii''. In the coming decades, R. ''darwinii'' is expected to have a reduced dispersion by up to 56%. This means that R. ''darwinii'' will be more localized to certain habitats in the future. R. ''darwinii'' populations are especially susceptible to damage due to wildfires. Using climate change models, wildfires are expected to increase at a dramatic rate which will negatively affect the R. ''darwinii'' habitat. <ref>{{Cite journal |last=Azat |first=Claudio |last2=Valenzuela-Sánchez |first2=Andrés |last3=Delgado |first3=Soledad |last4=Cunningham |first4=Andrew A. |last5=Alvarado-Rybak |first5=Mario |last6=Bourke |first6=Johara |last7=Briones |first7=Raúl |last8=Cabeza |first8=Osvaldo |last9=Castro-Carrasco |first9=Camila |last10=Charrier |first10=Andres |last11=Correa |first11=Claudio |last12=Crump |first12=Martha L. |last13=Cuevas |first13=César C. |last14=Maza |first14=Mariano de la |last15=Díaz-Vidal |first15=Sandra |date=2021-05 |title=A flagship for Austral temperate forest conservation: an action plan for Darwin's frogs brings key stakeholders together |url=https://www.cambridge.org/core/journals/oryx/article/flagship-for-austral-temperate-forest-conservation-an-action-plan-for-darwins-frogs-brings-key-stakeholders-together/040B38FFC544950B0110B8F8E65F046E |journal=Oryx |language=en |volume=55 |issue=3 |pages=356–363 |doi=10.1017/S0030605319001236 |issn=0030-6053}}</ref> |
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== Research == |
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| ⚫ | Since 2018, the species is classified as Endangered on the [[IUCN Red List]]. A 2013 study reported results of a population survey conducted from 2008–2012, which found the species at just 36 of 223 previously recorded habitat sites, with small populations at those sites. |
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R. ''darwinii'' have been used to study size variation in body size of ectotherms. Previous research supported the hypothesis that larger body sizes were tied to higher seasonality because of an idea termed starvation resistance. Starvation resistance is the idea that the larger the size of an ectotherm, the less likely it is to “starve,” as it can use its body’s mass for fuel. |
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However, work done on R. ''darwinii'' supports another hypothesis. The hypothesis being that greater seasonality leads to longer periods of time in the cold due to an idea termed the hibernation hypothesis. These animals in the cold are likely to hibernate and under hibernation will have a lower basal metabolic rate. This will lead to lower amounts of energy expended, and thus less of the ectotherm's body mass will be lost. This explanation offers an alternative to the starvation resistance |
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| ⚫ | Since October 2021, |
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R. ''darwinii'' seem to be chosen in this research due to their broad distribution in the habitats they reside in. This allows for researchers to study the same species in different climates, an important aspect in order to make claims about the relationship between body size and seasonality/climate. <ref>{{Cite journal |last=Valenzuela-Sánchez |first=Andrés |last2=Cunningham |first2=Andrew A. |last3=Soto-Azat |first3=Claudio |date=2015-12-23 |title=Geographic body size variation in ectotherms: effects of seasonality on an anuran from the southern temperate forest |url=https://doi.org/10.1186/s12983-015-0132-y |journal=Frontiers in Zoology |language=en |volume=12 |issue=1 |pages=37 |doi=10.1186/s12983-015-0132-y |issn=1742-9994 |pmc=PMC4690379 |pmid=26705403}}</ref> |
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Due to its decline in the wild, captive colonies have been established as a precaution at two zoos in Chile, the [[Chilean National Zoo|National Zoo]] (working with the US [[Atlanta Botanical Garden]]) and [[Concepción Zoo]] (working with the [[University of Concepción]] and Germany's [[Leipzig Zoo]]).<ref name=Fenolio2012>{{cite journal | author=Fenolio, D. | year=2012 | title=Conserving South Chile's Imperiled Amphibian Fauna | journal=FrogLog | volume=100 | pages=30–31 }}</ref><ref name=thisischile2010>{{cite web | title=Universidad de Concepción saves Darwin's frog from extinction | url=https://www.thisischile.cl/universidad-de-concepcion-saves-darwins-frog-from-extinction/?lang=en | date=26 April 2010 | publisher=thisischile.cl | accessdate=17 January 2020 }}</ref> |
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==See also== |
==See also== |
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Revision as of 06:02, 12 October 2022
| Darwin's frog | |
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Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Amphibia |
| Order: | Anura |
| Family: | Rhinodermatidae |
| Genus: | Rhinoderma |
| Species: | R. darwinii
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| Binomial name | |
| Rhinoderma darwinii | |
| |
| Range in Chile in red (also occurs in adjacent southwestern Argentina) | |
Darwin’s frog (Rhinoderma darwinii), also called the southern Darwin's frog,[2] is a species of Chilean/Argentinian frog of the family Rhinodermatidae. It was discovered by Charles Darwin during his voyage on voyage on HMS Beagle.[3][4][5] on a trip to Chile. In 1841, French zoologist André Marie Constant Duméril and his assistant Gabriel Bibron described and named Darwin's frog. The diet of R. darwinii consists mostly of herbivore invertebrates.
Darwin’s frog is most known for its unique method of brooding. The male will facilitate development of its tadpoles' inside its vocal sac. This male brooding makes Darwin’s frog distinct from all other frogs (as the only other frog that has this behavior is the R. rufum and it may be extinct).
Characteristics
Darwin's frog is a small species with a snout–to–vent length of 2.2 to 3.1 cm (0.9 to 1.2 in). The snout is elongated into a fleshy proboscis which gives the head a triangular shape. The limbs are relatively long and slender. The front feet are not webbed, but some of the toes on the back feet usually are.[6]
The upperparts of this species are variably colored in brown or green. Some brown individuals may have weakly defined V-shaped markings on the back, have central upperparts that are distinctly lighter brown than the flanks, or have whitish front limbs. Females are typically brown and tend to stay on substrates that match this color. Males are far more variable and occur on a wider range of substrates; especially brooding males often are partially or completely green above.[7] The throat is brownish and the remaining underparts are black with large white blotches in a pattern that is unique to each individual.[5][6]
In captivity, male R. Darwinii have been shown to change color. These frogs that were initially brown changed to green over a year. This change in color is believed to be due to the green color of the environment these frogs were kept in.[8]
Distribution and habitat
Darwin's frog is found in Chile and Argentina. In Chile, its range extends from Concepción Province to Palena Province and in Argentina from Neuquén Province and Río Negro Province. It is found in glades and forested areas at altitudes of up to about 1,100 m (3,600 ft) above mean sea level.[1] It is also found in bogs and near slow-moving streams. It is found in a variety of vegetation types and it appears that a mixture of grassland, mossy areas, coarse woody debris, and young trees and bushes in a mature native forest provides its optimum habitat requirements. Short vegetation increases the retention of water while decreasing the temperature of the soil and provides concealment from predators. The population is fragmented and this frog has poor dispersal ability.[2]
Behavior
R. darwinii exhibit rare behavior in terms of territoriality and parental care. In anuran species, parental care and territoriality are positively related. In R. darwinii, there is high parental care due to the ingestion of tadpoles by fathers. However, there is low territoriality exhibited by these R. darwinii males. In fact, neither females nor males of R. darwinii have been observed guarding eggs. These observations of R. darwinii were used to further develop the relationship between territoriality and parental care by establishing the role of oviposition defense. These observations suggest that anurans will exhibit territoriality with parental care if they defend oviposition sites. [9]
Diet
Rhinoderma darwinii's diet consists of detritivore, herbivore, and carnivore invertebrates. It does not seem to have a preference regarding which type of invertebrate. It is observed to consume each type of invertebrate at a percentage consistent with their existence in the environment. The percentage at which carnivorous invertebrates are consumed is lower than herbivore or detritivore invertebrates. This difference can be explained because spiders are the predominant type of carnivore invertebrate prey that R. darwinii encounters. These spiders are able to evade the predation of R. darwinii effectively due to their evasion ability.
In the habitats where R. darwinii have been observed, there seem to be relatively high percentages of herbivore invertebrates. This could mean that R. darwinii seek environments with enriched herbivore invertebrates as a food source. [10]
R. darwinii style of predation has been characterized as “sit and wait.” This method seems to conserve energy and allows R. darwinii to evade predators effectively.
Mating
Male R. darwinii will call to attract females in an attempt to mate. It has even been shown that male R. darwinii will call even when brooding. However, no brooding males have been observed copulating with females. R. darwinii use non-linear vocal phenomena (NLP) in order to attract and communicate with mates. Darwin’s frog have been shown to have distinct mating patterns based on population and body size. More research needs to be conducted in order to further explore the mating of R. darwinii.[11]
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Parental Care
The female Darwin's frog lays up to forty eggs among the leaf litter. Females will generally lay 4-10 eggs. Males can brood 5-8 tadpoles at a time.
The male, after about three to four weeks, notices the developing embryos beginning to move, and then he ingests the eggs and holds them in his vocal sac. They hatch about three days later and he continues to carry the tadpoles around in his vocal sac where they feed off their egg yolks and secretions produced by the wall of the sac until metamorphosis. At this stage, about 6 weeks after being swallowed, while previous authors believed that during this period the adult male eats nothing, G B Howes, in 1888, dissected a brooding male and found its stomach full of beetles and flies and its large intestine clogged with "excreta like that of a normal individual." He concluded "that this extraordinary paternal instinct does not lead up to that self-abnegation". Following this, the small frogs hop out of the male's mouth and disperse.
In captivity, R. darwinii parents have been observed to leave the eggs unattended for around 3 weeks (some R. darwinii males will guard the eggs for these 3 weeks). Further, captive males have been shown to exhibit alloparental behavior. Foster males have been shown to take a defensive stance at the eggs (oviposition defense). They will go so far as to defend the eggs from the birth father of the eggs and will subsequently brood the kin of other males. In this specific experiment the foster father ingested 8 tadpoles, and after brooding had been completed, the foster father produced 2 frogs. This means that the metamorphosis process is not 100% efficient.This observation is consistent across studies and there exist some proposed explanations for the alloparental behavior. This alloparental behavior is especially rare among amphibians.
Two hypotheses for this behavior have been proposed:
- The first hypothesis is that foster fathers can improve upon their brooding skills by practicing. Improved brooding skills would result in males that can propagate more of their genes into the next generation.
- The second hypothesis is that foster fathers can exhibit that they have had past breeding success by brooding tadpoles that aren't theirs. This means that these foster fathers are hoping that future mates will see them brooding and be more likely to mate with them.
These hypotheses propose ideas in which there is some advantage for males who brood offspring that are not theirs.
The loss of some tadpoles in the metamorphosis from tadpole to frog is a unique feature of R. darwinii. This observation is likely explained by these hypotheses:
- The tadpoles that didn’t survive were converted into nutrition for the foster male and he digested them.
- The tadpoles died in the vocal sac of the foster male. The nutrients from these dead tadpoles served as sustenance for the surviving tadpoles occupying the vocal sac of the foster male. This phenomenon of one embryo consuming another is termed adelphophagy. The vocal sac of R. darwinii does not seem to have the proper structure to facilitate adelphophagy and thus this proposal is unlikely to explain the incomplete metamorphosis observed. [12]
Enemies
R. dawrinii have been shown to be highly susceptible to Batrachochytrium dendrobatidis infection.[13] The amphibian disease chytridiomycosis, caused by Batrachochytrium dendrobatidis fungal infection, is also a probable factor, "particularly from the northern part of their historical range". Populations on Chiloé Island were found to be considerably more abundant than on the mainland.
R. darwinii seems to be less affected by chytridiomycosis when compared to other amphibians. However, Chytridiomycosis can still infect and kill R. darwinii. Previous studies have supported the idea that chytridiomycosis could be somewhat responsible for the decrease in R. darwinii population exhibited in Chile and Argentina. [14]
In recent years, studies have shown that R. darwinii have shown variation in Batrachochytrium dendrobatidis infection across populations. In populations where there was high Bd infection rates, there are observed to be higher population growth rates. Similarly, in populations with low Bd infection rates, there are observed to be lower population growth rates. Populations with higher Bd infections rates seemed to have the highest reproductive rates. This means that even though many individuals are dying of Bd infection, there are more individuals being born. There exists a positive relationship between Bd infection rate and the number of juvenile individuals for R. darwinii.[15]
This odd feature of Bd infection and R. darwinii population growth prompted further investigation. The explanation for this observation is termed the “parasite-induced plasticity” hypothesis. This hypothesis says that individuals will devote more resources towards reproduction as opposed to survival. This increased devotion towards reproduction takes place over a single generation. This plasticity is beneficial to the infected individual because the infection will take over at some point so until that point the individual will try to have as many offspring as possible.[16]
Population decline and conservation status
Darwin's frog has undergone significant population declines due to habitat loss and degradation, largely from conversion of native forests to tree plantations.
Since 2018, the species is classified as Endangered on the IUCN Red List. A 2013 study reported results of a population survey conducted from 2008–2012, which found the species at just 36 of 223 previously recorded habitat sites, with small populations at those sites. The recent change in its conservation category in IUCN from Vulnerable to Endangered, arose from the Chile's amphibian reevaluation workshop for the Red List (Soto-Azat et al., 2015). The justification for its current category is due to its limited occupation area (estimated at 264 km2), severe fragmentation of its populations and continued decline.
Since October 2021, R. darwinii has been classified as Critically Depleted by the IUCN. It was determined that the survival of the species is highly dependent on conservation activities and its recovery potential is high.
Due to its decline in the wild, captive colonies have been established as a precaution at two zoos in Chile, the National Zoo (working with the US Atlanta Botanical Garden) and Concepción Zoo (working with the University of Concepción and Germany's Leipzig Zoo).
The habitat of R. darwinii is known as the Valdivian temperate rainforest. The Valdivian is decreasing in the north due to pine and eucalyptus agriculture expansion. This is removing some of the habitat of R. darwinii and forcing them south. The south Valdivian is more protected and is suitable for R. darwinii habitance.
In 2017, the IUCN SSC Amphibian Specialist Group formed a Binational Conservation Strategy that brought together 30 different countries. The goal of this group is to study Rhinoderma darwinii in order to improve conservation efforts. The group details the unique characteristics (mouth brooding) as one justification for this increased conservation effort. The goal of the group is to understand key aspects of information related to Rhinoderma darwinii by the year 2028.
Dispersal-constrained species distribution models have shown a decrease of up to 40% in habitat for R. darwinii over the years 1970 to 2010. The habitat for R. darwinii is expected to increase in the coming years. However, this emerging habitat is not likely to be habited by R. darwinii due to its inability to translocate to these new habitats.
Climate change is also expected to play a role in the habitat availability of R. darwinii. In the coming decades, R. darwinii is expected to have a reduced dispersion by up to 56%. This means that R. darwinii will be more localized to certain habitats in the future. R. darwinii populations are especially susceptible to damage due to wildfires. Using climate change models, wildfires are expected to increase at a dramatic rate which will negatively affect the R. darwinii habitat. [17]
Research
R. darwinii have been used to study size variation in body size of ectotherms. Previous research supported the hypothesis that larger body sizes were tied to higher seasonality because of an idea termed starvation resistance. Starvation resistance is the idea that the larger the size of an ectotherm, the less likely it is to “starve,” as it can use its body’s mass for fuel.
However, work done on R. darwinii supports another hypothesis. The hypothesis being that greater seasonality leads to longer periods of time in the cold due to an idea termed the hibernation hypothesis. These animals in the cold are likely to hibernate and under hibernation will have a lower basal metabolic rate. This will lead to lower amounts of energy expended, and thus less of the ectotherm's body mass will be lost. This explanation offers an alternative to the starvation resistance
R. darwinii seem to be chosen in this research due to their broad distribution in the habitats they reside in. This allows for researchers to study the same species in different climates, an important aspect in order to make claims about the relationship between body size and seasonality/climate. [18]
See also
References
- ^ a b IUCN SSC Amphibian Specialist Group (2018). "Rhinoderma darwinii". IUCN Red List of Threatened Species. 2018: e.T19513A79809372. doi:10.2305/IUCN.UK.2018-1.RLTS.T19513A79809372.en. Retrieved 20 November 2021.
- ^ a b Soto-Azat, Claudio; Valenzuela-Sánchez, Andrés; Clarke, Barry T.; Busse, Klaus; Ortiz, Juan Carlos; Barrientos, Carlos; Cunningham, Andrew A. (2013). "Is Chytridiomycosis Driving Darwin's Frogs to Extinction?". PLOS One. 8 (11): e79862. doi:10.1371/journal.pone.0079862. ISSN 1932-6203. PMC 3835940. PMID 24278196.
- ^ Bell, Thomas (1843). Charles Darwin (ed.). The Zoology of the Voyage of H.M.S. Beagle, Part V: Reptiles. London: Smith, Elder and Co. p. 48. Retrieved 1 December 2013.
- ^ Duméril, A.M.C.; Bibron, G. (1841). Erpétologie Générale; ou, Histoire Naturelle Complète des Reptiles. Vol. 8. Paris: Librairie Encyclopédique de Roret. p. 659. Retrieved 2 December 2013.
- ^ a b Gratwicke, Brian; Soto-Azat, Claudio; Valenzuela-Sánchez, Andrés; Collen, Ben; Rowcliffe, J. Marcus; Veloso, Alberto; Cunningham, Andrew A. (2013). "The Population Decline and Extinction of Darwin's Frogs". PLOS One. 8 (6): e66957. doi:10.1371/journal.pone.0066957. ISSN 1932-6203. PMC 3680453. PMID 23776705.
- ^ a b Fran Sandmeier; Kellie Whittaker (8 September 2008). "Rhinoderma darwinii". AmphibiaWeb. Retrieved 6 December 2013.
- ^ a b Bourke, J.; K. Busse; T.C.M. Bakker (2011). "Sex differences in polymorphic body coloration and dorsal pattern in Darwin's frogs (Rhinoderma darwinii)". Herpetological Journal. 21: 227–234.
- ^ Bourke, Johara; Barrientos, Carlos; Ortiz, Juan C.; Busse, Klaus; Böhme, Wolfgang; Bakker, Theo C. M. (1 November 2011). "Colour change in Darwin's frogs (Rhinoderma darwinii, Duméril and Bibron, 1841) (Anura: Rhinodermatidae)". Journal of Natural History. 45 (43–44): 2661–2668. doi:10.1080/00222933.2011.597885. ISSN 0022-2933.
- ^ Valenzuela‐Sánchez, A.; Harding, G.; Cunningham, A. A.; Chirgwin, C.; Soto‐Azat, C. (2014-12). "Home range and social analyses in a mouth brooding frog: testing the coexistence of paternal care and male territoriality". Journal of Zoology. 294 (4): 215–223. doi:10.1111/jzo.12165. ISSN 0952-8369.
{{cite journal}}: Check date values in:|date=(help) - ^ Molina-Burgos, B. E.; Valenzuela-Sánchez, A.; Alvarado-Rybak, M.; Klarian, S.; Soto-Azat, C. (2018). "Trophic ecology of the Endangered Darwin's frog inferred by stable isotopes".
{{cite journal}}: Cite journal requires|journal=(help) - ^ Serrano, José M.; Penna, Mario; Soto-Azat, Claudio (2 September 2020). "Individual and population variation of linear and non-linear components of the advertisement call of Darwin's frog (Rhinoderma darwinii)". Bioacoustics. 29 (5): 572–589. doi:10.1080/09524622.2019.1631214. ISSN 0952-4622.
- ^ "X-MOL". en.x-mol.com. Retrieved 12 October 2022.
- ^ Valenzuela‐Sánchez, Andrés; Azat, Claudio; Cunningham, Andrew A.; Delgado, Soledad; Bacigalupe, Leonardo D.; Beltrand, Jaime; Serrano, José M.; Sentenac, Hugo; Haddow, Natashja; Toledo, Verónica; Schmidt, Benedikt R.; Cayuela, Hugo (2022-02). "Interpopulation differences in male reproductive effort drive the population dynamics of a host exposed to an emerging fungal pathogen". Journal of Animal Ecology. 91 (2): 308–319. doi:10.1111/1365-2656.13603. ISSN 0021-8790.
{{cite journal}}: Check date values in:|date=(help) - ^ Soto-Azat, Claudio; Valenzuela-Sánchez, Andrés; Clarke, Barry T.; Busse, Klaus; Ortiz, Juan Carlos; Barrientos, Carlos; Cunningham, Andrew A. (20 November 2013). "Is Chytridiomycosis Driving Darwin's Frogs to Extinction?". PLOS ONE. 8 (11): e79862. doi:10.1371/journal.pone.0079862. ISSN 1932-6203. PMC 3835940. PMID 24278196.
{{cite journal}}: CS1 maint: PMC format (link) CS1 maint: unflagged free DOI (link) - ^ Valenzuela-Sánchez, Andrés; Azat, Claudio; Cunningham, Andrew A.; Delgado, Soledad; Bacigalupe, Leonardo D.; Beltrand, Jaime; Serrano, José M.; Sentenac, Hugo; Haddow, Natashja; Toledo, Verónica; Schmidt, Benedikt R.; Cayuela, Hugo (2022-02). "Interpopulation differences in male reproductive effort drive the population dynamics of a host exposed to an emerging fungal pathogen". The Journal of Animal Ecology. 91 (2): 308–319. doi:10.1111/1365-2656.13603. ISSN 1365-2656. PMID 34704260.
{{cite journal}}: Check date values in:|date=(help) - ^ Hardy, Bennett M.; Muths, Erin; Koons, David N. (2022-02). "Context‐dependent variation in persistence of host populations in the face of disease". Journal of Animal Ecology. 91 (2): 282–286. doi:10.1111/1365-2656.13654. ISSN 0021-8790.
{{cite journal}}: Check date values in:|date=(help) - ^ Azat, Claudio; Valenzuela-Sánchez, Andrés; Delgado, Soledad; Cunningham, Andrew A.; Alvarado-Rybak, Mario; Bourke, Johara; Briones, Raúl; Cabeza, Osvaldo; Castro-Carrasco, Camila; Charrier, Andres; Correa, Claudio; Crump, Martha L.; Cuevas, César C.; Maza, Mariano de la; Díaz-Vidal, Sandra (2021-05). "A flagship for Austral temperate forest conservation: an action plan for Darwin's frogs brings key stakeholders together". Oryx. 55 (3): 356–363. doi:10.1017/S0030605319001236. ISSN 0030-6053.
{{cite journal}}: Check date values in:|date=(help) - ^ Valenzuela-Sánchez, Andrés; Cunningham, Andrew A.; Soto-Azat, Claudio (23 December 2015). "Geographic body size variation in ectotherms: effects of seasonality on an anuran from the southern temperate forest". Frontiers in Zoology. 12 (1): 37. doi:10.1186/s12983-015-0132-y. ISSN 1742-9994. PMC 4690379. PMID 26705403.
{{cite journal}}: CS1 maint: PMC format (link) CS1 maint: unflagged free DOI (link)
Sources
- Crump, M.L. (2003). Grzimek's Animal Life Encyclopedia, 2nd ed., Vol. 6 Amphibians, 175, Gale.
- Duellman, W.E., ed. (1999). Patterns of Distribution of Amphibians: A Global Perspective, 325, The Johns Hopkins University Press.
- Frost, D.R., ed. (1985). Amphibian Species of the World: A Taxonomic and Geographical Reference, 551, Allen Press, Inc. and the Association of Systematics Collections, Lawrence, Kansas.
External links
Data related to Rhinoderma darwinii at Wikispecies
Media related to Rhinoderma darwinii at Wikimedia Commons
