Common Surinam toad

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Common Surinam toad
Pipa pipa01.jpg
Scientific classification edit
Kingdom: Animalia
Phylum: Chordata
Class: Amphibia
Order: Anura
Family: Pipidae
Genus: Pipa
Species:
P. pipa
Binomial name
Pipa pipa
Suriname Toad Pipa pipa distribution map.png
Surinam toad range.[1]
Synonyms
  • Rana pipa Linnaeus, 1758
  • Pipa americana Laurenti, 1768

The common Surinam toad or star-fingered toad (Pipa pipa) is an aquatic species of frog in the family Pipidae with a widespread distribution in South America. The species is notable for hatching eggs in honeycombed chambers in the skin of the mother's back, releasing fully formed froglets after a period of 4-5 months.

Description[edit]

P. pipa is a strictly aquatic frog without a tongue.[2] The largest member of its genus, the species has an exceptionally depressed body, almost entirely flat and with a broad, flat, triangular head. The body is similar in appearance to a mottled brown leaf. The feet are broadly webbed with the front toes having small, star-like appendages. Males can grow up to 154 mm long, whereas females can reach up to 171 mm. Females can be distinguished not only by their length but also by their ring-shaped cloacas, visible when they are ready to breed.[3] The skin color is mostly light brown with some darker spots on the back, providing good camouflage[3][4] Nostrils are terminal, eyes very small, and the tympanum is missing. The limbs are in a laterally sprawled position in the plane of the body, and the fingertips are modified into four small lobes.[5] Absence of a tongue prevents the species from capturing prey with that organ like most other frogs, and instead suction capture is used.[6]

The skull is hyperossified and the cranial and postcranial bones are heavily modified compared to other anurans. While the eyes are relatively small and narrow, the species has a lateral line system and neuromast organs which are assumed to help it locate prey and predators.[2]

Museum specimen of a Pipa pipa

Habitat and Distribution[edit]

The species lives under submerged litter in slow flowing watercourses, stream backwaters, ponds, and pools from flooded forests.[7] It has the largest geographic distribution for its genus and is found in much of South America, including Brazil and Ecuador, particularly within the Amazonian rainforest.[7]It is so strongly adapted for an aquatic lifestyle that on land it is helpless and scarcely able to move.[8]

Diet[edit]

The species is an omnivorous ambush hunter. Its diet consists mostly of invertebrates, such as worms, insects, crustaceans and small fish.[3][9][10] Field caught Pipa pipa have been found with erythrinid fish species, other small Pipa pipa, catfish, arthropods and amphibian skin in their stomachs.[2] One study found that Cyclopoida made up 67%, Diptera larvae 7.3%, and Heteroptera 6.3% of prey. The skin fragments that were found in their stomach are an indication that these frogs commit cannibalism or eat their own skin which is common among amphibians. Based on these results, P. pipa is an opportunist that will eat anything that falls into the water or that the species may occasionally forage in land.[11]

Feeding Behavior[edit]

The Surinam toad can catch prey by entraining and ingesting large volumes of water and by limiting fish escape with its fingers. It uses a bidirectional suction mechanism where the amount of water ingested is influenced by the ability for the frog to actively increase its body volume. When it captures prey, its buccopharyngeal (the cavity connecting the mouth and the pharynx) is very distensible and can expand substantially. It has the ability to use its entire trunk to rapidly enlarge its buccopharyngeal cavity and expand into the lower end of the trunk. Additionally, its major organs such as the hyoid and larynx, heart, lungs, liver, esophagus, and stomach are arranged to move a third of the length of the body which gives space for expansion of the buccopharyngeal cavity. The fish that are captured are located in the middle of the body instead of the stomach. This modification allows for Pipa pipa’s unique inertial suction feeding.[2]

The species may be the only tetrapod vertebrate that can enlarge its entire trunk during suction feeding. Additionally, it has been found that P. pipa can modulate the timing of most elements of its prey capture process. For instance, it can asymmetrically or asynchronously move its jaw during the capture and manipulation of its prey.[2]

The forelimbs are used to grasp and shove the prey into the mouth. Prior to capture of its prey, the forelimbs are held in a forward-flexed position so that each hand is positioned in front of the head. During prey capture, the forelimbs are extended and drawn towards the mouth. If the prey item is encountered during this movement, it is grabbed and pushed into the mouth. Otherwise it is sucked into the mouth without any use of the limbs. These frogs have a high degree of dexterity compared to other pipid species.[2]

Reproduction[edit]

The mating period of these frogs is during the fall and winter seasons. These frogs call usually during the morning and mid-afternoon hours.[12] Males of this species do not attract females with croaks, instead producing a sharp clicking sound by snapping the hyoid bone in their throats.[13] The clicking sound resembles metallic noises. The average rate of these clicks is four clicks per second, consisting of blocks of 10 to 20 seconds per period. [12] Thereafter, the male will grab the front legs of the female in amplexus, causing the clochea and the skin of the female to swell.[14] The partners rise from the floor while in amplexus and flip through the water in arcs. The couple will swim around in the water until they have to swim to the surface to breathe. Afterwards, they will swim back down to the bottom of the water. There the male will lay on his back, with the female on top of him on her stomach.[15]

During the turnover behavior, the male and female cloacae are brought close together. Maintaining the horizontal position, the pair lays three to five eggs. During the amplexus, the female’s back is gradually swelled to a puffy condition. The lips of the female’s vent also enlarges because of engorged cloacal lymph spaces. The male and female cloacae are brought close together, and many eggs are laid while the pair is horizontal. On descent the male, with an arched back, while making inward thrusting movements, transfers the eggs anteriorly to the female's swollen dorsal epidermis. The eggs then become implanted into the female’s dorsal epidermis. During the first day the eggs on the female’s back will sink into the skin and by evening will be set into the back of the female. Two days later, the yolks of most of the eggs are beneath the skin level and only parts of the jelly and outer membranes of the eggs are visible on the backs above. The coverings over the eggs will remain in the wild until the brood emerges.[12] The embryos develop through to the tadpole stage inside these pockets but do not emerge as tadpoles, instead remaining in their chambers until complete development to toadlet stage. The young toads grow a tail during their growth, but these will only be temporary because they will need the tail for inhaling oxygen. After 12 to 20 weeks, the young toads will hatch as small toads, looking identical to their parents. It takes a while for them to grow bigger since they are only 25 mm long when they are born. Once they have emerged from their mother's back, the toads begin a largely solitary life. After giving birth to the new toads, the mother slowly sheds the thin layer of skin used for birth and can begin the cycle again.[3][5]

Parental Care[edit]

These eggs are observed to first be a pearly white. Larval development is direct meaning that there are no free-swimming tadpoles. The eggs are instead  incubated on the female’s dorsum (the back of the females). The eggs undergo development on the back of their mothers and are roughly 6.4 to 6.6 mm in diameter. The young then hatch around 77 to 136 days and crawl out of the eggs deposited on the mother’s backs.[12] The mother’s back interestingly is covered from vent to the head with eggs and after the young develop enough, the back’s skin which covers the eggs becomes akin to a lid which is then shed off. This allows for the small toadlets to peer out of the pockets. [8]

Because the Pipa pipa cannot discriminate in their natural habitats between prey and young, it has adapted to not birth fish-like young.[8] The mothers appear to be able to recognize their young visually in clear enough waters, however because of the murky waters of their natural habitats, young that are unfortunate enough to brush the mother’s hands or enter the feeding zone near her mouth would probably be eaten since the mother cannot see them.[12]

Mating competition[edit]

When two males encounter each other during the mating season, there is a possibility that the two males will fight. The toads nearly press their snout to the chest or throat of the other male. During the conflict, both males make single clicks to each other, which resembles the sound that they normally use during the breeding. If the toads have eye contact, they make a rapid series of these clicks. This process shows no visible movement of the vocal system. After some time, they will return to swimming, but will never lose contact with one another. One toad swims above the other very closely, touching his enemy with only the front limbs. The fight between males may be long-lasting. Eventually, one of the males bites the other male and this is supposed to be the end of their encounter, although they do not always give up the fight. It may happen that the male that loses the battle does not give up and disturbs the breeding pair itself, even during reproduction.[12]

Natural enemies[edit]

The Pipa pipa lacks dermal antimicrobial peptides which could make it slightly more susceptible to disease. This is because while the antimicrobial cationic α-helical peptides that are produced many many different species of frog do not have robust scientific evidence on how they aid in immune response in the wild, research proposes that these peptides offer definite evolutionary advantage to the species that they secrete these peptides but it is not necessary to survival. These peptides, in the correct potency, can offer powerful antimicrobial properties and inhibit diseases such as chytridiomycosis and families of viruses like Ranaviruses.[16]

Cryptic Coloration[edit]

The Pipa pipa uses cryptic camouflage to lie in wait for its prey as its brown coloration allows for it to blend in with its murky surroundings.[12]

Conservation[edit]

Although the species is classified as Least Concern by the IUCN, it is subject to habitat loss and habitat fragmentation caused by agricultural expansions.[1] Due to the deforestation and human encroachment on the Amazon rainforest, the species has been found in regions where it would not normally be encountered, such as terrestrial locations. This highlights the importance of preserving the endangered habitats that these frogs live in.[7][17]

Captivity[edit]

In the aquarium, the species prefers plants and rocks to hide behind. Low light conditions are required. Because the Surinam toad excretes high amounts of ammonia, water changes have to be frequent.[18]

Pipa pipa in captivity

Cultural significance[edit]

In a letter to Catherine Clarkson the poet Samuel Taylor Coleridge writes “I envy dear Southey's power of saying one thing at a time in short and close sentences, whereas my thoughts bustle along like a Surinam Toad, with little toads sprouting out of back, side, and belly, vegetating while it crawls”.[19]

The Surinam toad is commonly cited as an example of a trypophobia trigger.[20]

References[edit]

  1. ^ a b c IUCN SSC Amphibian Specialist Group (2015). "Pipa pipa". IUCN Red List of Threatened Species. 2015: e.T58163A61414791. doi:10.2305/IUCN.UK.2015-4.RLTS.T58163A61414791.en. Retrieved 18 November 2021.
  2. ^ a b c d e f Fernandez, Edward; Irish, Frances; Cundall, David (March 2017). "How a Frog, Pipa pipa, Succeeds or Fails in Catching Fish". Copeia. 105 (1): 108–119. doi:10.1643/CH-16-510. ISSN 0045-8511. S2CID 90903754.
  3. ^ a b c d Wandzel, Kathryn. "Pipa pipa". Animal Diversity Web. Archived from the original on 2016-04-05. Retrieved 2021-11-30.
  4. ^ "Surinam toads, facts and photos". National Geographic. 2020-09-28. Archived from the original on 2021-02-19. Retrieved 2021-11-30.
  5. ^ a b Trueb, Linda (10 January 2000). "Ontogeny of the Bizarre: An Osteological Description Of". Journal of Morphology. 243 (1): 75–104. doi:10.1002/(SICI)1097-4687(200001)243:1<75::AID-JMOR4>3.0.CO;2-L. PMID 10629097. S2CID 45830241.
  6. ^ Carreño, Carrie A.; Nishikawa, Kiisa C. (2010-06-15). "Aquatic feeding in pipid frogs: the use of suction for prey capture". Journal of Experimental Biology. 213 (12): 2001–2008. doi:10.1242/jeb.043380. ISSN 1477-9145. PMC 2878287. PMID 20511513.
  7. ^ a b c Vaz-Silva, Wilian; Andrade, Tiago (2009-01-09). "Amphibia, Anura, Pipidae, Pipa pipa: distribution extension, new state record and geographic distribution map". Check List. 5 (3): 507–509. doi:10.15560/5.3.507. ISSN 1809-127X.
  8. ^ a b c Buchacher, Christian O. (1993-01-01). "Field studies on the small Surinam toad, Pipa arrabali, near Manaus, Brazil". Amphibia-Reptilia. 14 (1): 59–69. doi:10.1163/156853893X00192. ISSN 1568-5381.
  9. ^ "Pipa Pipa (Suriname Toad)" (PDF). Sta.uwi.edu. Retrieved 9 April 2022.
  10. ^ "Pipa pipa". Animaldiversity.org. Retrieved 9 April 2022.
  11. ^ Alves-Pinto, Helena (2014). "Morphometric variation of Pipa Pipa (Linnaeus, 1758) (Anura: Pipidae) with notes on diet and gonad development". Herpetology Notes. 7: 347–353.
  12. ^ a b c d e f g Rabb, George B.; Snedigar, Robert (1960). "Observations on Breeding and Development of the Surinam Toad, Pipa pipa". Copeia. 1960 (1): 40–44. doi:10.2307/1439843. ISSN 0045-8511. JSTOR 1439843.
  13. ^ Piper, Ross (2007), Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals, Greenwood Press.
  14. ^ Whitefield, P. (1984). Encyclopedie van het dierenrijk - Alle gewervelde dieren in woord en beeld (in Dutch). Uitgeverij Areopagus. p. 472.
  15. ^ Preston-Mafham, Ken (1999). Frogs and Toads. Apple Identifier. p. 16.
  16. ^ Conlon, J. Michael (2011-01-01). "The contribution of skin antimicrobial peptides to the system of innate immunity in anurans". Cell and Tissue Research. 343 (1): 201–212. doi:10.1007/s00441-010-1014-4. ISSN 1432-0878.
  17. ^ Dantas, Silionamã Pereira; Tavares, Helane Dias; Pascoal, Wanieulli; Saviato, Mário Junior; Ávila, Robson Waldemar; Vasconcelos, Tiago Silveira; Oda, Fabrício Hiroiuki (2019-10-02). "New distribution records from the Brazilian Cerrado and species distribution modelling of Boana crepitans, Lithobates palmipes, Pipa pipa , and Micrurus h. hemprichii". Biodiversity. 20 (4): 149–160. doi:10.1080/14888386.2019.1664931. ISSN 1488-8386. S2CID 210782037.
  18. ^ Indiviglio, Frank (2009-04-03). "Surinam Toads (Pipa pipa) as Pets: Acclimating New Animals and Special Considerations - Part 2". That Reptile Blog. Archived from the original on 2009-04-21. Retrieved 2021-12-30.
  19. ^ Natali, Ilaria; Volpone, Annalisa (30 March 2016). Symptoms of Disorder: Reading Madness in British Literature, 1744-1845. ISBN 9781621967095.
  20. ^ "Do you have trypophobia? Unofficial phobia might make your skin crawl". Blog.seattlepi.com.

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