Arctic | Mammals
The female reproductive tract of the bowhead whale: Taking a closer gross anatomical look Presenter: Raphaela Stimmelmayr , rafstimmel@gmail.com, North Slope Borough Rita Acker , rita.acker@north-slope.org, North Slope Borough, Department of Wildlife Management Olive Kanayurak , olive.kanayurak@north-slope.org, NSB DWM Reproductive tracts of female cetaceans have annular folds reminiscent of the cervical uteri (neck of the uterus) in bovidae. We provide a detailed gross description of the caudally directed annular folds and their morphometry in fresh tracts of the bowhead whale ( Balaena mysticetus ) and present some experimental data on the likelihood of cervical versus vaginal semen deposition. Multiple (4-7) annular folds (plicae circulares) of variable length arise perpendicular from the tubular wall of the reproductive tract posterior to the short uterine body. The length of the annular folds and the respective recesses (pockets) formed between adjacent annular folds increase with the size of the reproductive tract (immature to mature). For example in a mature pregnant (~30 cm fetus length) female (19B6; TBL1678.94 cm) maximum fold length was 44-45 cm and in an immature female (19B4: 830.58 cm TBL) 9 cm respectively. The openings of the annular folds do not readily align but are offset resulting in a sigmoid shaped inner pathway. This is most obvious in the mature tract. Anterior recesses (1-3) are filled with beige-green tinged thick mucus also present in a full term fetal tract. The mucosa of the annular folds is arranged in distinct longitudinal folds (plicae longitudinalis). Number of longitudinal folds varies between the annular folds ranging between 9 to 27 folds. The most caudal annular lip-like fold is covered by smooth epithelium (beige white) similar in appearance to the vaginal lining but bears a small longitudinally folded mucosa insert. Within its lumen the anterior laying annular fold can be visualized. The outer body and rim of the latter is lined by smooth beige epithelium which transitions (towards the luminal canal) to the reddish longitudinally folded mucosa characteristic of the remaining cranial annular folds. The previously described mucosal insert lies opposite the mucosal opening. The inner dimensions of the annular rings in an immature female (19B4) are comparable to the various diameters (0.7 - 3.1 cm) along the terminal cone of the penis (tip of the penis to preputial reflection) in an immature male whale (19B3; 911.86 cm TBL). For example two thirds (~`19 cm) of a~ 37 cm long terminal cone was physically advanced through the respective annular folds in a caudal to cranial fashion with the penis tip ultimately resting within the first recess. Thus cervical/intracervical semen deposition is anatomically possible in bowhead whales.
Alaska Marine Science Symposium 2023 287
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