Assisted breeding technology in the saltwater crocodile Crocodylus porosus: a review and look to the future

Characterization of sperm and implications for male fertility in the last of the Rhynchocephalians

Managing a species of conservation concern can be best achieved when there is information on the reproductive physiology of both sexes available; however, many species lack this critical, baseline information. One such species, the tuatara (Sphenodon punctatus), is the last surviving member of one of the four reptile orders (Rhynchocephalia) and is the only reptile known to lack a male intromittent organ. Culturally and evolutionarily significant, the conservation of this species is a global priority for the maintenance of biodiversity. In light of this, we characterized the morphology, viability and swim speed of mature tuatara sperm for the first time. We found that tuatara sperm are filiform and bear the remarkably conserved three-part sperm structure seen across the animal kingdom. Tuatara sperm are long (mean total length 166 μm), with an approximate head:midpiece:tail ratio of 15:1:17. While tuatara sperm are capable of high levels of within-mating viability (94.53%), the mean viability across all samples was 58.80%. Finally, tuatara sperm had a mean curvilinear velocity swim speed (μ × s - 1) of 82.28. At the population level, there were no differences in viability or mean swim speed between sperm collected from a male's first mating of a season and repeat matings; however, the maximum sperm swim speed increased in observed repeated matings relative to first matings. Interestingly, faster sperm samples had shorter midpieces, but had greater viability and longer head and tail sections. This work expands our understanding of male reproductive characteristics and their variation to a new order, provides wild references for the assessment of captive individuals, lays the groundwork for potential assisted reproductive techniques and highlights variation in male reproductive potential as an important factor for consideration in future conservation programs for this unique species.

Common goals, different stages: the state of the ARTs for reptile and amphibian conservation

Amphibians and reptiles are highly threatened vertebrate taxa with large numbers of species threatened with extinction. With so many species at risk, conservation requires the efficient and cost-effective application of all the tools available so that as many species as possible are assisted. Biobanking of genetic material in genetic resource banks (GRBs) in combination with assisted reproductive technologies (ARTs) to retrieve live animals from stored materials are two powerful, complementary tools in the conservation toolbox for arresting and reversing biodiversity decline for both amphibians and reptiles. However, the degree of development of the ARTs and cryopreservation technologies differ markedly between these two groups. These differences are explained in part by different perceptions of the taxa, but also to differing reproductive anatomy and biology between the amphibians and reptiles. Artificial fertilisation with cryopreserved sperm is becoming a more widely developed and utilised technology for amphibians. However, in contrast, artificial insemination with production of live progeny has been reported in few reptiles, and while sperm have been successfully cryopreserved, there are still no reports of the production of live offspring generated from cryopreserved sperm. In both amphibians and reptiles, a focus on sperm cryopreservation and artificial fertilisation or artificial insemination has been at the expense of the development and application of more advanced technologies such as cryopreservation of the female germline and embryonic genome, or the use of sophisticated stem cell/primordial germ cell cryopreservation and transplantation approaches. This review accompanies the publication of ten papers on amphibians and twelve papers on reptiles reporting advances in ARTs and biobanking for the herpetological taxa.

Reptile assisted reproductive technologies: can ART help conserve 300million years of evolution by preserving extant reptile biodiversity?

Biodiversity loss is the greatest environmental problem threatening ecosystem, animal, and human health. Anthropogenic induced changes to climate, habitat, disease, species distributions, poaching, and unsustainable trade have accelerated extinction rates in all vertebrates, including reptiles. Preventing reptile extinctions will require humans to acknowledge these losses and develop ex situ and in situ plans to preserve them. Assisted reproductive technologies (ART) are management tools used to protect numerous vertebrate taxa; however, progress in developing ART for reptiles has lagged. Creating functional and sustainable reptile ART will strengthen our conservation capacity by capturing genetic material from select individuals to overcome natural or manmade boundaries. Utilising short-term gamete storage and genome resource banking, in conjunction with timed artificial insemination (AI) or ex ovo incubation, could lead to profound advances in reptile conservation, mitigating the loss of reptile biodiversity. In this article, we review ART reptile research completed since the 1970s. Topics include AI, hormonal control of reproduction, gamete collection, gamete storage, and genome resource banking. Additionally, we review the potential application of advanced reproductive methodologies, including in vitro/ex ovo fertilisation, intracytoplasmic sperm injection, cloning (somatic cell nuclear transfer), and genetic editing.

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.