Dendrelaphis punctulatus

Abstract: Although the evolution of sexual dimorphism is most commonly ascribed to sexual selection, ecological divergence between the sexes may also be important. Significant differences between the sexes in head size relative to body length are common among snakes, and apparently are not attributable to sexual selection. If head-size dimorphism has evolved because it enables males and females to eat different prey sizes, then one might expect that: 1) heads of male and female snakes should differ in shape as well as size; 2) this difference should be greatest in feeding structures, especially those that constrain maximum ingestible prey size; and 3) such trophic structures should be disproportionately larger in the sex with the larger head. We examined relative proportions of different components of the head in cleared-and-stained skulls of four snake species showing sexual dimorphism: Acrochordus arafurae (Acrochordidae), Dendrelaphis punctulatus (Colubridae), Pseudechis porphyriacus (Elapidae), and Laticauda colubrina (Laticaudidae). Discriminant Function Analysis could distinguish >95% successfully between male and female heads in all four species. This dimorphism in head shape was primarily due to sex differences in trophic structures in three out of the four species. In each case, the sex with the larger head had disproportionately larger trophic structures, as predicted from the hypothesis that ecological divergence between the sexes has been important in the evolution of sexual dimorphism in snakes.

Abstract: Pentastomids are endoparasites of the respiratory system of vertebrates, maturing primarily in carnivorous reptiles. Adult and larval pentastomids can cause severe pathology resulting in the death of their intermediate and definitive hosts. The study of pentastomids is a neglected field, impaired by risk of zoonoses, difficulties in species identification, and life cycle complexities. We surveyed wild snakes in the tropics of Australia to clarify which host species possess these parasites, and then sought to identify these pentastomids using a combination of morphological and molecular techniques. We detected pentastomid infections in 59% of the 81 snakes surveyed. The ubiquity of pentastomid infections in snakes of the Australian tropics sampled in this study is alarmingly high considering the often-adverse consequences of infection and the recognized zoonotic potential of these parasites. The pentastomids were of the genera Raillietiella and Waddycephalus and infected a range of host taxa, encompassing seven snake species from three snake families. All seven snake species represent new host records for pentastomids of the genera Raillietiella and/or Waddycephalus. The arboreal colubrid Dendrelaphis punctulatus and the terrestrial elapid Demansia vestigiata had particularly high infection prevalences (79% and 100% infected, respectively). Raillietiella orientalis infected 38% of the snakes surveyed, especially frog-eating species, implying a frog intermediate host for this parasite. Raillietiella orientalis was previously known only from Asian snakes and has invaded Australia via an unknown pathway. Our molecular data indicated that five species of Waddycephalus infect 28% of snakes in the surveyed area. Our morphological data indicate that features of pentastomid anatomy previously utilised to identify species of the genus Waddycephalus are unreliable for distinguishing species, highlighting the need for additional taxonomic work on this genus.

Abstract: Ranaviruses have been isolated from many ectothermic vertebrates, and serological surveys of both amphibians and reptiles have shown the presence of ranaviral antibodies in a proportion of these populations. An enzyme-linked immunosorbent assay (ELISA) was developed to measure serum antibodies against ranavirus in Australian reptiles. The ELISA was validated with serum from challenge trials with Bohle iridovirus (BIV) in 6 reptilian species. A preliminary serosurvey of northern Queensland riparian reptile fauna (saw-shelled turtles Myuchelys latisternum, Krefft's river turtles Emydura macquarii krefftii, freshwater crocodiles Crocodylus johnstoni, as well as the snakes Boiga irregularis, Dendrelaphis punctulatus, Tropidonophis mairii, Morelia spilota, Liasis childreni and L. fuscus) revealed evidence of past exposure to Bohle iridoviral antigens in part of the population at several locations sampled. Furthermore, in Krefft's river turtles and freshwater crocodiles, a statistically significant trend was apparent for larger reptiles to be more likely to have BIV-reactive sera than smaller individuals. The use of adult tortoise populations as sentinels can assist in monitoring the presence of BIV in northern Australian freshwater streams, and thereby the potential dangers to native fauna from this agent.

Abstract: Common tree snakes, Dendrelaphis punctulatus, are medium to large colubrid snakes that are relatively common in the eastern and northern parts of tropical Australia. The only previous study on this species involved museum specimens from across the taxon’s range. During a seven-year period we collected data on 131 field-caught specimens from a melanotic population in the Townsville district of north Queensland. Dendrelaphis punctulatus was found to be primarily diurnal, with a peak in activity centred around the reproductive period during the transition from dry to wet seasons. Females were larger than males with respect to all measured parameters, including mass and head size. Reproduction in females was strongly seasonal and clutch size was related to maternal body size. Prey items consisted of frogs, lizards and locusts.