An Attempt at Captive Breeding of the Endangered Newt Echinotriton andersoni, from the Central Ryukyus in Japan

Abstract

Simple SummaryWe naturally bred the endangered Anderson’s crocodile newt (Echinotriton andersoni) and tested a laboratory farming technique using near-biotopic breeding cages with several male and female pairs collected from Okinawa, Amami, and Tokunoshima Islands. This is the first published report of successfully propagating an endangered species by using breeding cages in a laboratory setting for captive breeding. Our findings on the natural breeding and raising of larvae and adults are useful in breeding this endangered species, and can be applied to the preservation of other similarly wild and endangered species.AbstractAnderson’s crocodile newt (Echinotriton andersoni) is distributed in the Central Ryukyu Islands of southern Japan, but environmental degradation and illegal collection over the last several decades have devastated the local populations. It has therefore been listed as a class B1 endangered species in the IUCN Red List, indicating that it is at high risk of extinction in the wild. The species is also protected by law in both Okinawa and Kagoshima prefectures. An artificial insemination technique using hormonal injections could not be applied to the breeding of this species in the laboratory. In this study we naturally bred the species, and tested a laboratory farming technique using several male and female E. andersoni pairs collected from Okinawa, Amami, and Tokunoshima Islands and subsequently maintained in near-biotopic breeding cages. Among 378 eggs derived from 17 females, 319 (84.4%) became normal tailbud embryos, 274 (72.5%) hatched normally, 213 (56.3%) metamorphosed normally, and 141 (37.3%) became normal two-month-old newts; in addition, 77 one- to three-year-old Tokunoshima newts and 32 Amami larvae are currently still growing normally. Over the last five breeding seasons, eggs were laid in-cage on slopes near the waterfront. Larvae were raised in nets maintained in a temperature-controlled water bath at 20 °C and fed live Tubifex. Metamorphosed newts were transferred to plastic containers containing wet sponges kept in a temperature-controlled incubator at 22.5 °C and fed a cricket diet to promote healthy growth. This is the first published report of successfully propagating an endangered species by using breeding cages in a laboratory setting for captive breeding. Our findings on the natural breeding and raising of larvae and adults are useful in breeding this endangered species and can be applied to the preservation of other similarly wild and endangered species such as E. chinhaiensis.

Cranial shape evolution of extant and fossil crocodile newts and its relation to reproduction and ecology

“…Data on the general ecology are still scarce for crocodile newts (see also Kieren et al, 2018), although several studies deal with the reproductive ecology of Echinotriton (Utsunomiya et al, 1978; Xie et al, 2000; Sparreboom et al, 2001; Utsunomiya and Matsui, 2002; Igawa et al, 2013). Only little information is available for Tylototriton , often only from anecdotal observations (e.g.…”

“…Pleurodeline newts are polymorphic in their reproductive mode and mating strategy (Kieren et al, 2018), including terrestrial and aquatic mating, as well as the choice of oviposition sites (Kuzmin et al, 1994; Ziegler et al, 2008; Igawa et al, 2013; Bernardes et al, 2017). Whereas some species use a ventral amplexus similar to terrestrial salamandridae, others perform a circular mating dance comparable to European newts (Dasgupta, 1994; Roy and Mushahidunnabi, 2001; Fleck, 2010a; 2010b; Wang et al, 2017; Gong et al, 2018).…”

Amphibians and conservation breeding programmes: do all threatened amphibians belong on the ark?

“…Despite all of the potential issues, there have recently been several notable successes maintaining and breeding 'difficult' species (Gagliardo et al 2010;Gawor et al 2012;Igawa et al 2013) and species whose wild habitats are difficult to recreate in captivity (Preininger et al 2012). These successes are encouraging, but developing appropriate captive breeding protocols is not necessarily enough.…”

Clasp and dance: Mating mode promotes variable sexual size and shape dimorphism trajectories in crocodile newts (Caudata: Salamandridae)

“…For mating either a ventral amplexus or a circular mating dance is performed either taking place in aquatic or terrestrial habitats. Also, female crocodile newts deposit egg clutches either in water or on land (Igawa et al, 2013, Phimmachak et al, 2015b, Pasmans et al, 2017, Hernandez, 2016. These differences in terms of mating and reproductive ecology can even be observed within one genus Tylototriton comprising most crocodile newt species.…”