Lamar Sarah K, Ormsby Diane K, Nelson Nicola J
School of Biological Sciences, Level 2, Te Toki a Rata Building, Victoria University of Wellington, Wellington 6012, New Zealand.
Centre for Biodiversity and Restoration Ecology, Level 2, Te Toki a Rata Building, Victoria University of Wellington, Wellington 6012, New Zealand.
Curr Zool. 2024 Apr 3;70(6):786-794. doi: 10.1093/cz/zoae012. eCollection 2024 Dec.
The theoretical trade-off between immune and endocrine investment in mating animals has received mixed empirical support, particularly in reptiles. We investigated the relationship between male sexual characteristics, diet, and immune response to stress in an island population of tuatara () across two mating seasons. Tuatara are promiscuous, with a highly skewed mating system where males face significant competition for access to mates and postcopulatory competition for fertilization success. We found that tuatara sperm viability and swim speed were negatively associated with male body condition and the ratio of heterophils to lymphocytes. Additionally, sperm swim speed was negatively associated with spine area, mite load, and the total number of circulating white blood cells, but was positively associated with tick number. This is likely a function of social dynamics in this system where larger male size predicts greater spatial overlap with potential rivals and increased tick load. Because the production of sexual characteristics may be costly, we also investigated the effect of diet on sperm quality. We did not identify an association between diet and sperm viability. However, sperm swim speed was negatively associated with carbon-13 and positively associated with nitrogen-15. We suspect that these results reflect the influence of seabird-based nutrients in this island ecosystem, particularly polyunsaturated fatty acid, and antioxidant damage on tuatara sperm. In total, these results provide evidence of a trade-off between pre- and post-copulatory sexual characteristics and the immune and endocrine systems in male tuatara.
在有性繁殖动物中，免疫与内分泌投入之间的理论权衡得到了参差不齐的实证支持，尤其是在爬行动物中。我们在两个交配季节里，对一个岛屿上楔齿蜥种群的雄性性特征、饮食与应激免疫反应之间的关系进行了调查。楔齿蜥是滥交的，其交配系统高度倾斜，雄性在获取配偶方面面临激烈竞争，在交配后为了受精成功也存在竞争。我们发现，楔齿蜥的精子活力和游动速度与雄性身体状况以及嗜中性粒细胞与淋巴细胞的比例呈负相关。此外，精子游动速度与脊柱面积、螨虫负荷和循环白细胞总数呈负相关，但与蜱虫数量呈正相关。这可能是该系统中社会动态的一个作用，即较大的雄性体型预示着与潜在对手有更大的空间重叠以及蜱虫负荷增加。由于性特征的产生可能代价高昂，我们还研究了饮食对精子质量的影响。我们没有发现饮食与精子活力之间存在关联。然而，精子游动速度与碳-13呈负相关，与氮-15呈正相关。我们怀疑这些结果反映了该岛屿生态系统中以海鸟为基础的营养物质的影响，特别是多不饱和脂肪酸以及抗氧化损伤对楔齿蜥精子的影响。总的来说，这些结果为雄性楔齿蜥交配前和交配后的性特征与免疫和内分泌系统之间的权衡提供了证据。
