Arctic | Mammals
Sperm morphology in mature male bowhead whales: Preliminary findings Presenter: Raphaela Stimmelmayr , rafstimmel@gmail.com, North Slope Borough
Sperm morphology is correlated with fertility and is an important aspect of male breeding soundness evaluation for domestic livestock. Variations in abnormal versus normal sperm ratios along the breeding season have been documented in seasonally breeding species including other baleen whales. The objective of this study was to assess the proportion of abnormal sperm and characterize the type of sperm abnormalities observed in mature male bowhead whales ( Balaena mysticetus ). For the six whales included in this study, all taken near Utqiagvik, Alaska between April to August, total body length (m) ranged between 12.85 to 15.7. Air dried unstained and stained (Quick dip stain) impression smears made from fresh or previously frozen (-20o C) testes/epididymis were evaluated. For each slide sperm abundance was qualitatively evaluated (low; medium; high) and a total of 100 sperm were assessed by light microscopy at ×400 magnification for their morphology. Sperm abundance ranged between low to high among whales with low sperm abundance (n=1) observed in late August (08/30), medium abundance (n=3) observed in April (04/20 - 04/25) and June (06/03). High abundance (n=2) was observed during May (05/07- 05/23). Only one whale, the largest among the examined whales (05B16; TBL15.7 m) had a normal spermiogram (80%), for the remaining six whales sperm abnormalities (missing tails; bent tails; hooked tails etc.) ranged between 90 - 100 % irrespective of harvest months. High proportion of abnormal sperm (35 % and > 80 % (71.7-92.2) have been reported in Bryde’s whale (Balaenoptera edeni) and minke whale (Balanoptera acutarostrata) sampled outside the breeding season. For comparison in Atlantic bottlenose dolphins (Tursiops truncatus), a toothed whale species that likely breeds throughout the year, the proportion of abnormal sperm ranged between 4 -11%. Similarly, a low proportion of abnormal sperm (<5%) was observed in a male harbor porpoise stranded during the respective summer breeding season (Stimmelmayr unpubl.data). Though we cannot exclude that high sperm abnormality is typical for these latter whales, ranging in size between 12.85 to 13.89 m, we propose that the high abnormal sperm ratio likely indicates the end of the effective breeding season.
Alaska Marine Science Symposium 2023 288
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