Characterisation of sperm production and morphology in the male Philippine crocodile Crocodylus mindorensis via voluntary behavioural training.

Philippine crocodiles Crocodylus mindorensis are critically endangered due to agricultural and fishing threats that have severely fragmented their habitat and population in the Philippines. Captive management plans are important to safeguard against their extinction, but the current population in US zoos is small, and breeding is hampered by the slow growth of this species and the danger of introducing differently sized animals for breeding. There is little information regarding the sperm characteristics of crocodilians, and none for Philippine crocodiles. In this study, we sought to characterise sperm production in the male Philippine crocodile (n =1) by performing voluntary (without sedation or restraint) collections (n =181) over a 3.5-year period. Peak sperm production in this individual occurs from January to July, when the mean (±s.e.m.) total number of spermatozoa recovered was 10.2×106 ±3.8×106 (n =104), compared with 0.3×106 ±0.2×106 (n =71) for all other months of the year. Analysis of sperm morphology indicated that 15.9% of spermatozoa exhibited normal morphology. A bent tail was the most common abnormality (48.2%) observed. Understanding the basic reproductive biology of the male Philippine crocodile will facilitate the development of artificial reproductive technologies to improve captive propagation and genetic management of this species.

Ranavirus could facilitate local extinction of rare amphibian species.

There is growing evidence that pathogens play a role in population declines and species extinctions. For small populations, disease-induced extinction may be especially probable. We estimated the susceptibility of two amphibian species of conservation concern (the dusky gopher frog [Lithobates sevosus] and boreal toad [Anaxyrus boreas boreas]) to an emerging pathogen (ranavirus) using laboratory challenge experiments, and combined these data with published demographic parameter estimates to simulate the potential effects of ranavirus exposure on extinction risk. We included effects of life stage during pathogen exposure, pathogen exposure interval, hydroperiod of breeding habitat, population carrying capacity, and immigration in simulations. We found that both species were highly susceptible to ranavirus when exposed to the pathogen in water at environmentally relevant concentrations. Dusky gopher frogs experienced 100 % mortality in four of six life stages tested. Boreal toads experienced 100 % mortality when exposed as tadpoles or metamorphs, which were the only life stages tested. Simulations showed population declines, greater extinction probability, and faster times to extinction with ranavirus exposure. These effects were more evident with more frequent pathogen exposure intervals and lower carrying capacity. Immigration at natural rates did little to mitigate effects of ranavirus exposure unless immigration occurred every 2 years. Our results demonstrate that disease-induced extinction by emerging pathogens, such as ranavirus, is possible, and that threat may be especially high for species with small population sizes. For the species in this study, conservation organizations should incorporate ranavirus surveillance into monitoring programs and devise intervention strategies in the event that disease outbreaks occur.

Successful artificial insemination in the corn snake, Elaphe gutatta, using fresh and cooled semen.

The design and implementation of assisted reproductive technology to improve genetic diversity and augment captive populations is an important but rarely applied research field in reptiles. Using the corn snake (Elaphe gutatta) as a model, the Henry Doorly Zoo recently produced offspring born as a result of artificial insemination using both fresh, diluted semen, and diluted semen stored at refrigeration for 3 days. Semen was collected noninvasively from sexually mature male corn snakes using a gentle massaging technique, extended in medium then inseminated into the oviducts of adult females. Using molecular genetic techniques to confirm or refute the success of the insemination using primers developed for the black rat snake, Elaphe obsolete, all possible parents and offspring genotypes were evaluated. A paternity-by-exclusion analysis verified that the offspring were in fact a result of artificial insemination. Zoo Biol 26:363-369, 2007. (c) 2007 Wiley-Liss, Inc.