Taricha torosa was divided into two subspecies until 2007, when it was determined that the two represent "distinct evolutionary lineages". Taricha torosa sierrae is now identified as a distinct species, Taricha sierrae (Sierra newt). Taricha torosa torosa, formally referred to as the Coastal Range newt, is now referred to as Taricha torosa (California newt).
Range and habitat
California newts exist primarily on the California coastline and in southern Sierra Nevada, because they prefer less humid climates than the rough-skinned newts. Outside the breeding season, the newts are land-dwelling, preferring rock crevices and logs.
Reproduction occurs generally between December and early May. Typically, the adult newts will return to the pool in which they hatched. After a mating dance, the male mounts the female and rubs his chin on her nose. He then attaches a spermatophore to the substrate, which she will retrieve into her cloaca.
The egg mass released by the female contains between seven and 30 eggs, and is roughly the consistency of a thick gelatin dessert. Typically, the egg masses are attached to stream plant roots or to rocky crevices in small pools of slow-moving water, but they have also been known to be attached to underwater rocks or leaf debris. While shallow in a wide sense, these pools are rather deep relative to the average depth of a Southern California stream, varying in depth from about 1–2 metres (3.3–6.6 ft).
Adult newts will stay in the pools throughout the breeding season, and can be occasionally found well into the summer. Larvae hatch sometime in early to midsummer, depending on local water temperature. Larvae are difficult to find in streams, as they blend in well with the sandy bottom, to which they usually stay close.
Toxicity and predation
Like other genus Taricha members, the glands in the skin of Taricha torosa secrete the potent neurotoxin tetrodotoxin, which is hundreds of times more toxic than cyanide. This is the same toxin found in pufferfish and harlequin frogs. Researchers believe bacteria synthesize tetrodotoxin, and the animals that employ the neurotoxin acquire it through consumption of these bacteria. This neurotoxin is strong enough to kill most vertebrates, including humans. However, it is dangerous only if ingested.
Due to their toxicity, California newts have few natural predators. Garter snakes are the most common, and some species have developed a genetic resistance to tetrodotoxin. The mutations in the snake’s genes that conferred resistance to the toxin have resulted in a selective pressure that favors newts that produce more potent levels of toxin. Increases in newt toxicity then apply a selective pressure favoring snakes with mutations conferring even greater resistance. This evolutionary arms race has resulted in the newts producing levels of toxin far in excess of what is needed to kill any other conceivable predator.
Earthworms, snails, slugs, woodlice, bloodworms, mosquito larvae, crickets, and other invertebrates are among the California newt's prey. In the Sierra Nevada, the newt will also consume trout eggs. In an aquarium habitat, earthworms provide the newt with all necessary nutrients. Other natural prey items would benefit the captive newt. Pellets tend to be inappropriate for terrestrial caudates, and fish food should be avoided completely.
Taricha torosa, the California newt, is currently a California Special Concern species (DFG-CSC). Some populations have been greatly reduced in southern California coastal streams due to the introduction of non-native, invasive species and human habitation. The mosquitofish (Gambusia affinis) and red swamp crayfish (Procambarus clarkii) have caused the greatest reduction in newt populations.
Introduced as fish bait and stock pond prey, red swamp crayfish are an incredibly aggressive, prolific, and stalwart species that will prey upon newt larvae and egg masses. The crayfish will also disrupt newt breeding via competition for space during the summer mating season and physically antagonizing adults. Crayfish will typically maul the adult newts with their claws, and subsequent infection can lead to death. Taricha torosa that are present in streams with introduced crayfish often sport tails with several notches removed. They are amphibians and live in humid areas.
- Shawn R. Kuchta (2007). "Contact zones and species limits: hybridization between lineages of the California Newt, Taricha torosa, in the southern Sierra Nevada". Herpetologica (The Herpetologists’ League) 63 (3): 332–350. doi:10.1655/0018-0831(2007)63[332:CZASLH]2.0.CO;2.
- Feldman, C. R.; Brodie, E. D.; Brodie, E. D.; Pfrender, M. E. (2009). "The evolutionary origins of beneficial alleles during the repeated adaptation of garter snakes to deadly prey". Proceedings of the National Academy of Sciences 106 (32): 13415–13420. doi:10.1073/pnas.0901224106. PMC 2726340. PMID 19666534.
- Hanifin, Charles T. (2010). "The Chemical and Evolutionary Ecology of Tetrodotoxin (TTX) Toxicity in Terrestrial Vertebrates". Marine Drugs 8 (3): 577–593. doi:10.3390/md8030577. PMC 2857372. PMID 20411116.
- Feldman, C. R.; Brodie, E. D.; Brodie, E. D.; Pfrender, M. E. (2010). "Genetic architecture of a feeding adaptation: garter snake (Thamnophis) resistance to tetrodotoxin bearing prey". Proceedings of the Royal Society B: Biological Sciences 277 (1698): 3317–3325. doi:10.1098/rspb.2010.0748. PMC 2981930. PMID 20522513.
- Charles T Hanifin; Edmund D Brodie Jr.; Edmund D Brodie III (2008). "Phenotypic mismatches reveal escape from arms-race coevolution". PLoS Biology 6 (3): 60. doi:10.1371/journal.pbio.0060060.
- Seth C. Gamradt; Lee B. Kats (1996). "Effect of Introduced Crayfish and Mosquitofish on California Newts". Conservation Biology 10 (4): 1155–1162. doi:10.1046/j.1523-1739.1996.10041155.x.
- Hammerson (2008). "Taricha torosa". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 21 March 2014. Database entry includes a range map and justification for why this species is of least concern
- San Diego Natural History Museum
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- CaliforniaHerps.com: Taricha torosa - California Newt — California newt facts.
- Mister-toad.com: mating behavior of California newts — with video.
- Caudata.org: Culture of California newts (Taricha torosa) — guide to identifying species and keeping as a pet.