Abstract Land transformation reduced the habitat of Psammobates geometricus to small isolated fragments, rendering the species vulnerable to extinction. Field biologists often use erythrocyte metrics to assess wildlife health but need baseline values to distinguish normal variations from disease or chronic stress. Here we characterise erythrocyte types and features of P. geometricus and assess if age, sex and environmental fluctuations influence their frequencies and metrics. We collected blood from males, females and juveniles over four seasons to prepare smears for cytological evaluation. We treated the smears with May–Grünwald–Giemsa stains and used imaging software to measure size, shape and colour intensity of erythrocyte types. The blood of all groups contained immature, mature and senescent erythrocytes, and the appearance of each cell type corresponded to descriptions for other chelonians. Season had a strong effect on the occurrence of erythrocyte types and features with few group differences. The frequency of immature erythrocytes was high in winter and spring, the wet season, reflecting increased erythropoiesis. Mature erythrocytes dominated in summer and autumn, but frequencies of senescent cells, poikilocytosis, cytoplasmic inclusions and cytoplasmic vacuoles increased in autumn, indicating that water and food shortages caused physiological stress. The small size and elongated shape of summer and autumn erythrocytes would facilitate oxygen exchange when high temperatures increase metabolic needs of ectotherms. Lower temperatures and energy demands in the wet season counter the lower oxygen capacity of round, immature cells. Our results provide baseline information on erythrocyte physiology and metrics for health assessments of geometric tortoises.

中文翻译：

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极度濒危的几何龟 Psammobates geometryus 的红细胞形态：季节、性别和年龄的影响

摘要 土地改造使几何沙门菌的栖息地减少为孤立的小碎片，使该物种容易灭绝。野外生物学家经常使用红细胞指标来评估野生动物的健康，但需要基线值来区分疾病或慢性压力的正常变化。在这里，我们描述了几何形疟原虫的红细胞类型和特征，并评估了年龄、性别和环境波动是否会影响它们的频率和指标。我们收集了四个季节的雄性、雌性和幼鱼的血液，以制备用于细胞学评估的涂片。我们用 May-Grünwald-Giemsa 染色剂处理涂片，并使用成像软件测量红细胞类型的大小、形状和颜色强度。所有组的血液都含有未成熟、成熟和衰老的红细胞，并且每种细胞类型的外观对应于其他龟类的描述。季节对红细胞类型和特征的发生有很强的影响，几乎没有群体差异。未成熟红细胞的频率在冬春季节高湿季节，反映红细胞生成增加。成熟红细胞在夏秋季节占主导地位，但秋季衰老细胞、异形红细胞增多症、细胞质包涵体和细胞质空泡的频率增加，表明水和食物短缺引起了生理应激。当高温增加外温动物的代谢需求时，夏季和秋季红细胞的小尺寸和细长形状将促进氧气交换。雨季较低的温度和能量需求抵消了圆形、未成熟细胞较低的氧气容量。