Gross and microscopic anatomy of the tongue and gastrointestinal tract of the bowhead whale (Balaena mysticetus)

Typescript (photocopy).The tongue, esophagus, gastrointestinal tract and anal canal were examined grossly and microscopically in the bowhead whale, Balaena mysticetus. The tongue was a prominent, spindle-shaped, muscular organ lined by a partially keratinized stratified squamous epithelium. The esophagus was a muscular tube whose mucosa consisted of a stratified squamous epithelium as well as mucoserous glands and lymphatic nodules. The stomach was comprised of four compartments: a nonglandular forestomach lined by a keratinized stratified squamous epithelium; a fundic chamber containing the proper gastric glands; a narrow tubular connecting channel containing mucosal mucous glands; and a larger tubular fourth compartment, the pyloric chamber, also lined by mucous glands. The pyloric sphincter separated this final gastric chamber from the small intestine which began as a dilated sac, the duodenal ampulla, lined by mucous glands and devoid of villi. The duodenum continued after the ampulla in a more typical, tubular fashion and was lined by villi and crypts. The hepatopancreatic duct joined the duodenum shortly following the termination of the ampulla, traveling intramurally before joining the duodenal lumen. The small intestine ended with the sudden dilatation of the colon in the absence of a cecum. The colon was lined by typical straight, unbranched tubular glands. The anal canal was lined by a partially keratinized stratified squamous epithelium and contained numerous crypt-associated clusters of lymphatic nodules within its wall

Gross and microscopic anatomy of the tongue and gastrointestinal tract of the bowhead whale (Balaena mysticetus)

Typescript (photocopy).The tongue, esophagus, gastrointestinal tract and anal canal were examined grossly and microscopically in the bowhead whale, Balaena mysticetus. The tongue was a prominent, spindle-shaped, muscular organ lined by a partially keratinized stratified squamous epithelium. The esophagus was a muscular tube whose mucosa consisted of a stratified squamous epithelium as well as mucoserous glands and lymphatic nodules. The stomach was comprised of four compartments: a nonglandular forestomach lined by a keratinized stratified squamous epithelium; a fundic chamber containing the proper gastric glands; a narrow tubular connecting channel containing mucosal mucous glands; and a larger tubular fourth compartment, the pyloric chamber, also lined by mucous glands. The pyloric sphincter separated this final gastric chamber from the small intestine which began as a dilated sac, the duodenal ampulla, lined by mucous glands and devoid of villi. The duodenum continued after the ampulla in a more typical, tubular fashion and was lined by villi and crypts. The hepatopancreatic duct joined the duodenum shortly following the termination of the ampulla, traveling intramurally before joining the duodenal lumen. The small intestine ended with the sudden dilatation of the colon in the absence of a cecum. The colon was lined by typical straight, unbranched tubular glands. The anal canal was lined by a partially keratinized stratified squamous epithelium and contained numerous crypt-associated clusters of lymphatic nodules within its wall

A note on the possibility of identifying Leydig and Sertoli cells by immunohistochemistry in bowhead whales (Balaena mysticetus)

Leydig cells have been found to be either unidentifiable or at apparent low numbers during routine histologic examination of bowhead whale testes. Therefore, formalin-fixed, paraffin-embedded testicular tissues from 14 bowhead whales were retrospectively examined to determine if immunohistochemical staining could aid in identification of Sertoli and Leydig cells. Multiple intratesticular samples were examined when available. Sertoli and Leydig cells were differentiated using inhibin and calretinin stains. Significant whale length and seasonal differences were not found; however, a trend toward increased staining intensity was noted for autumn harvested whales

Comparison of Dolphins' Body and Brain Measurements with Four Other Groups of Cetaceans Reveals Great Diversity

We compared mature dolphins with 4 other groupings of mature cetaceans. With a large data set, we found great brain diversity among 5 different taxonomic groupings. The dolphins in our data set ranged in body mass from about 40 to 6,750 kg and in brain mass from 0.4 to 9.3 kg. Dolphin body length ranged from 1.3 to 7.6 m. In our combined data set from the 4 other groups of cetaceans, body mass ranged from about 20 to 120,000 kg and brain mass from about 0.2 to 9.2 kg, while body length varied from 1.21 to 26.8 m. Not all cetaceans have large brains relative to their body size. A few dolphins near human body size have human-sized brains. On the other hand, the absolute brain mass of some other cetaceans is only one-sixth as large. We found that brain volume relative to body mass decreases from Delphinidae to a group of Phocoenidae and Monodontidae, to a group of other odontocetes, to Balaenopteroidea, and finally to Balaenidae. We also found the same general trend when we compared brain volume relative to body length, except that the Delphinidae and Phocoenidae-Monodontidae groups do not differ significantly. The Balaenidae have the smallest relative brain mass and the lowest cerebral cortex surface area. Brain parts also vary. Relative to body mass and to body length, dolphins also have the largest cerebellums. Cortex surface area is isometric with brain size when we exclude the Balaenidae. Our data show that the brains of Balaenidae are less convoluted than those of the other cetaceans measured. Large vascular networks inside the cranial vault may help to maintain brain temperature, and these nonbrain tissues increase in volume with body mass and with body length ranging from 8 to 65% of the endocranial volume. Because endocranial vascular networks and other adnexa, such as the tentorium cerebelli, vary so much in different species, brain size measures from endocasts of some extinct cetaceans may be overestimates. Our regression of body length on endocranial adnexa might be used for better estimates of brain volume from endocasts or from endocranial volume of living species or extinct cetaceans

Comparison of Dolphins' Body and Brain Measurements with Four Other Groups of Cetaceans Reveals Great Diversity

We compared mature dolphins with 4 other groupings of mature cetaceans. With a large data set, we found great brain diversity among 5 different taxonomic groupings. The dolphins in our data set ranged in body mass from about 40 to 6,750 kg and in brain mass from 0.4 to 9.3 kg. Dolphin body length ranged from 1.3 to 7.6 m. In our combined data set from the 4 other groups of cetaceans, body mass ranged from about 20 to 120,000 kg and brain mass from about 0.2 to 9.2 kg, while body length varied from 1.21 to 26.8 m. Not all cetaceans have large brains relative to their body size. A few dolphins near human body size have human-sized brains. On the other hand, the absolute brain mass of some other cetaceans is only one-sixth as large. We found that brain volume relative to body mass decreases from Delphinidae to a group of Phocoenidae and Monodontidae, to a group of other odontocetes, to Balaenopteroidea, and finally to Balaenidae. We also found the same general trend when we compared brain volume relative to body length, except that the Delphinidae and Phocoenidae-Monodontidae groups do not differ significantly. The Balaenidae have the smallest relative brain mass and the lowest cerebral cortex surface area. Brain parts also vary. Relative to body mass and to body length, dolphins also have the largest cerebellums. Cortex surface area is isometric with brain size when we exclude the Balaenidae. Our data show that the brains of Balaenidae are less convoluted than those of the other cetaceans measured. Large vascular networks inside the cranial vault may help to maintain brain temperature, and these nonbrain tissues increase in volume with body mass and with body length ranging from 8 to 65% of the endocranial volume. Because endocranial vascular networks and other adnexa, such as the tentorium cerebelli, vary so much in different species, brain size measures from endocasts of some extinct cetaceans may be overestimates. Our regression of body length on endocranial adnexa might be used for better estimates of brain volume from endocasts or from endocranial volume of living species or extinct cetaceans

Reproductive parameters of Bering‐Chukchi‐Beaufort Seas bowhead whales

Data from Bering-Chukchi-Beaufort Seas bowhead whales (Balaena mysticetus), harvested during 1973–2021 by aboriginal subsistence hunters, were used to estimate reproductive parameters: length at sexual maturity (LSM), age at sexual maturity (ASM), pregnancy rate (PR), and calving interval. Sexual maturity (N = 187 females) was determined from the presence/absence of corpora in the ovaries, or a fetus. Using sampling bias-corrected logistic regression, LSM was estimated at 13.5 m, 95% CI [13.0, 13.8]. There was a downward trend in LSM over time, statistically significant with one method but marginal with another. A growth model translated this estimate to an ASM estimate of 23.5 years, 95% CI [20.4, 26.7]. Pregnancy rate was determined from mature females (N = 125), and from a subset limited to certain autumn-caught whales (n = 37) to reduce bias. The PR was estimated at 0.46 globally, 95% CI [0.36, 0.55] and 0.38 for the autumn sample, 95% CI [0.20, 0.51]. Both estimated PRs are consistent with a 3-year calving interval, because the larger estimate includes two cohorts of pregnant whales harvested in spring, and bowhead whale gestation is longer than 12 months. These analyses represent the most conclusive empirical estimates of ASM, LSM, and PR for this bowhead whale stock from the largest available data sets to date