Tylototriton vietnamensis, Böhme, Schöttler, Nguyen & Köhler, 2005

Bernardes, Marta, Rauhaus, Anna, Michel, Clara, Pham, Cuong The, Nguyen, Truong Quang, Le, Minh Duc, Pasmans, Frank, Bonkowski, Michael & Ziegler, Thomas, 2017, Larval development and breeding ecology of Ziegler’s Crocodile Newt, Tylototriton ziegleri Nishikawa, Matsui and Nguyen, 2013 (Caudata: Salamandridae), compared to other Tylototriton representatives, Amphibian & Reptile Conservation (e 138) 11 (1), pp. 72-87 : 79-80

Developmental biology of T. vietnamensis

Eggs: The record of one egg directly after deposition had a diameter of 11.97 mm and 0.73 g of weight, while one egg ready to hatch measured 10.10 mm and weighted 0.56 g. Measurements from random eggs in the field showed an egg diameter ranging between 6.06–13.58 mm (mean 9.73 ± 1.61 mm, n = 133) and weight ranging from 0.19–1.15 g (mean 0.48 ± 0.21 g, n = 133). Eggs were transparent and clear shortly after egg deposition and later changed to brownish transparent.

Body shape and size of hatched larvae: range of body length at hatching time was 15.59–17.85 mm (mean 17.04 ± 0.85 mm, n = 5). Dorsal fin well developed and higher than head, starting at the middle of trunk; ventral fin shorter than dorsal fin; body long and slender; snout short and flat; gills well developed. At stage 33 two fingers were visible in the forelimb and the hind limb bud was already visible. Toes, fingers, and joints were fully developed at stage 41. At stage 44 gills started to atrophy. Efts started to move to land at a size of 44.15 mm with 0.6 g of weight.

Coloration in life: ground color light yellowish ochre; dark pigmentation on dorsal flanks, tail and head; venter slightly transparent to creamy white with no pigmentation; yellow spots scattered on dorsal side of head, body and tail; fingers and toes transparent to yellowish; gills light orange; eyes golden with black pupils. Pigmentation got darker with age turning black shortly before metamorphosis; toes and finger tips remained yellow as well as ventral ridge of tail. However, during field work at the type locality of this species we came across slight phenotypic variations, where larvae were also totally white at older stages ( Fig. 7 ).

Comparison with T. ziegleri : The diameter of the gelatinous layer of the egg was bigger in T. vietnamensis , as well as sizes of hatchlings. However, the estimated size at metamorphosis is likely bigger in T. ziegleri . The

development and body shape of larvae of T. vietnamensis were very similar to T. ziegleri , with the exception that in T. vietnamensis the body is more slender and elongated and the gills more orange than reddish.

Comparisons between the development of T. ziegleri and its congeners. Tylototriton ziegleri showed terrestrial oviposition, while T. taliangensis and T. cf. shanjing showed aquatic oviposition and T. kweichowensis and T. himalayanus showed both. In T. podichthys and T. panhai eggs were laid adhered to vegetation, while in T. ziegleri eggs were oviposited on the ground. One exceptional clutch of T. ziegleri showed eggs in small aggregations, like in T. podichthys . T. ziegleri had similar clutch sizes compared with T. hainanensis , but they were smaller than clutch sizes of T. kweichowensis and T. taliangensis and bigger than those of T. vietnamensis , T asperrimus , T. wenxianensis , and T. himalayanus . Eggs of T. ziegleri were transparent in coloration when young and turned to yellowbrownish when older, like in T. vietnamensis , while in T. himalayanus eggs were greenish-yellow in color. The comparison between sizes of ovae showed larger diameters for T. ziegleri in relation to T. kweichowensis , T. asperrimus , and T. podichthys . In relation to the diameter of the gelatinous layer, T. ziegleri had similar diameters to those of T. liuyangensis and T. wenxianensis , which were bigger than those of T. taliangensis , T. kweichowensis , and T. podichthys , and smaller than those of T. asperrimus . T. vietnamensis , T. cf. shanjing , and T. himalayanus showed a wider range of egg diameter, both bigger and smaller than those of T. ziegleri . Furthermore egg size was related to clutch size, as species with smaller eggs had bigger clutches and vice-versa (y = -29.68 x + 313.64; F 1, 5 = 66.85, P <0.001; r 2 = 91.7%). At hatching time T. vietnamensis had the largest larvae, followed in size by larvae of T. ziegleri , T. kweichowensis , and lastly by T. himalayanus . Size at metamorphosis seemed the smallest for T. shanorum and T. vietnamensis , followed by T. cf. shanjing , T. kweichowensis , T. broadoridgus , and T. himalayanus , while in comparison T. uyenoi and T. taliangensis had the largest sizes at metamorphosis ( Table 4 ).

Generally, the larvae of T. ziegleri can be distinguished from the described larvae of the genus Tylototriton by having: 1) a broad head (longer in T. cf. shanjing ); 2) the interorbital distance wider than internostril distance (similar distances in T. cf. shanjing ); 3) a pointed tail tip (round in T. uyenoi , T. taliangensis , T. cf. shanjing , and T. liuyangensis ); 4) the absence of balancers (versus present in T. uyenoi and T. cf. shanjing ); 5) dorsal fin higher than ventral fin (almost identical height in T. liuyangensis ); 6) tail shorter than SVL (tail longer than SVL in T. himalayanus ); 7) reddish gills (versus orange in T. vietnamensis ); 8) advanced larval stages with dark ground color with the exception of yellow digits and ventral fin (versus orange digits and fin in T. broadoridgus ; yellow at head, parotids, vertebral ridge, rib nodules, limbs and tail in T. uyenoi and T. shanorum ; brighter coloration laterally in the rib area in T. cf. shanjing ); and 9) being less slender than larvae of T. vietnamensis .

Figures

Fig. 7. Dark and light phenotypic variations of Tylototriton vietnamensis found at the type locality. Photo M. Bernardes.