Seasonal and geographic variation in packed cell volume and selected serum chemistry of platypuses

Tahneal Hawke,Gilad Bino,Richard T Kingsford,Jana Stewart

doi:10.1038/s41598-021-95544-z

Abstract

Platypuses (Ornithorhynchus anatinus) inhabit the permanent rivers and creeks of eastern Australia, from north Queensland to Tasmania, but are experiencing multiple and synergistic anthropogenic threats. Baseline information of health is vital for effective monitoring of populations but is currently sparse for mainland platypuses. Focusing on seven hematology and serum chemistry metrics as indicators of health and nutrition (packed cell volume (PCV), total protein (TP), albumin, globulin, urea, creatinine, and triglycerides), we investigated their variation across the species’ range and across seasons. We analyzed 249 unique samples collected from platypuses in three river catchments in New South Wales and Victoria. Health metrics significantly varied across the populations’ range, with platypuses from the most northerly catchment, having lower PCV, and concentrations of albumin and triglycerides and higher levels of globulin, potentially reflecting geographic variation or thermal stress. The Snowy River showed significant seasonal patterns which varied between the sexes and coincided with differential reproductive stressors. Male creatinine and triglyceride levels were significantly lower than females, suggesting that reproduction is energetically more taxing on males. Age specific differences were also found, with juvenile PCV and TP levels significantly lower than adults. Additionally, the commonly used body condition index (tail volume index) was only negatively correlated with urea, and triglyceride levels. A meta-analysis of available literature revealed a significant latitudinal relationship with PCV, TP, albumin, and triglycerides but this was confounded by variation in sampling times and restraint methods. We expand understanding of mainland platypuses, providing reference intervals for PCV and six blood chemistry, while highlighting the importance of considering seasonal variation, to guide future assessments of individual and population condition.

Highlights

Platypuses (Ornithorhynchus anatinus) inhabit the permanent rivers and creeks of eastern Australia, from north Queensland to Tasmania, but are experiencing multiple and synergistic anthropogenic threats
We examined the association between hematology and serum chemistry analytes and Tail Volume Index (TVI)[85], the most commonly used field body condition metric for platypuses
We examined associations between seven dependent hematology and serum chemistry response variables (PCV, TP, albumin, globulin, urea, creatinine, and triglycerides) and six independent explanatory variables: month (Jan-May, continuous 1 to 5), catchment, elevation of sample, sex, age, and tail volume index

Summary

Introduction

Platypuses (Ornithorhynchus anatinus) inhabit the permanent rivers and creeks of eastern Australia, from north Queensland to Tasmania, but are experiencing multiple and synergistic anthropogenic threats. Focusing on seven hematology and serum chemistry metrics as indicators of health and nutrition (packed cell volume (PCV), total protein (TP), albumin, globulin, urea, creatinine, and triglycerides), we investigated their variation across the species’ range and across seasons. Hematology and serum chemistry analytes are useful to measure body condition and organ function[29,30], and can detect more subtle variations in health that morphological indices might not detect They are valuable for endangered and difficult to study species. Platypuses have four genetically distinct populations across their distribution in Australia: Tasmania, Victoria and New South Wales combined, Queensland, and King Island[59] They vary in morphology across their range including: body mass (610–1500 g in Queensland to 1200–3000 g in T asmania60) and body length (Tasmanian individuals 21–29% longer than on the m ainland[61]).

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