Initial collection, characterization, and storage of tuatara (Sphenodon punctatus) sperm offers insight into their unique reproductive system

Sarah K Lamar,Jennifer A Moore,Nicola J Nelson,Diane K Ormsby,Helen R Taylor,Susan N Keall,Stefan Schlatt

doi:10.1371/journal.pone.0253628

Abstract

Successful reproduction is critical to the persistence of at-risk species; however, reproductive characteristics are understudied in many wild species. New Zealand’s endemic tuatara (Sphenodon punctatus), the sole surviving member of the reptile order Rhynchocephalia, is restricted to 10% of its historic range. To complement ongoing conservation efforts, we collected and characterized mature sperm from male tuatara for the first time. Semen collected both during mating and from urine after courting contained motile sperm and had the potential for a very high percentage of viable sperm cells (98%). Scanning electron microscopy revealed a filiform sperm cell with distinct divisions: head, midpiece, tail, and reduced end piece. Finally, our initial curvilinear velocity estimates for tuatara sperm are 2–4 times faster than any previously studied reptile. Further work is needed to examine these trends at a larger scale; however, this research provides valuable information regarding reproduction in this basal reptile.

Highlights

The persistence of viable populations of at-risk species hinges on them reproducing successfully
Undiluted semen samples collected from mating pairs were small in volume, ranging from 15μL to 28μL
This study presents a strong foundation for future ART work and improved conservation of this ancient reptile

Summary

Introduction

The persistence of viable populations of at-risk species hinges on them reproducing successfully. Understanding the reproductive ecology and physiology of wild animals is essential for effective conservation. Often this basic information is limited or lacking for wild animals, with much of our understanding derived from domesticated species like cattle or laboratory species like mice [1, 2]. Limited investigations into the sperm characteristics of wild species have shown high variability, even between closely related species [3,4,5,6]. This reduces our ability to extrapolate inferences from domestic to non-domestic species and warrants considerable further research on the reproductive characteristics of wild animals.

Methods

Results

Discussion

Conclusion