Allometric patterns of fetal head growth in mysticetes and odontocetes: Comparison of Balaena mysticetus and Stenella attenuata
Balaena mysticetus; bowhead whale; dolphins; Marine & Freshwater Biology; mechanism; pan-tropical spotted dolphin; prenatal growth; Stenella attenuata; whales; Zoology
Unlike other mammals, odontocetes and mysticetes have highly derived craniofacial bones. A growth process referred to as "telescoping" is partly responsible for this morphology. Here, we explore how changes in facial morphology during fetal growth relate to differences in telescoping between the adult odontocete Stenella attenuata and the mysticete Balaena mysticetus. We conclude that in both Stenella and Balaena head size increases allometrically. Similarly, odontocete nasal length and mysticete mouth size have strong positive allometry compared to total body length. However, the differences between odontocetes and mysticetes in telescoping are not directly associated with their fetal growth patterns. Our results suggest that cranial changes related to echolocation and feeding between odontocetes and mysticetes, respectively, begin during ontogeny before telescoping is initiated.
Armfield B A; George J C; Vinyard C J; Thewissen J G M
Marine Mammal Science
2011
2011-10
Journal Article or Conference Abstract Publication
<a href="http://doi.org/10.1111/j.1748-7692.2010.00445.x" target="_blank" rel="noreferrer noopener">10.1111/j.1748-7692.2010.00445.x</a>
Lateral mandibular wall thickness in Tursiops truncatus: Variation due to sex and age
age; bottlenose dolphin; hearing; intraspecific variation; lower jaw; mandible; Marine & Freshwater Biology; scaling; sensitivity; sex; thickness; Tursiops truncatus; Zoology
In odontocetes the mandibular bone serves two functions: to capture prey, and as a means of the reception and transmission of sound waves through a fat body in the mandibular canal, which opens posteriorly as the mandibular foramen. The posterior part of the lateral wall of the odontocete mandible is thin, and appears to represent a compromise between a strong mandible for prey capture and a thin vibrating plate for hearing. We studied the intraspecific variation of minimum thickness of the lateral mandibular wall along four transects (T1-T4) at the area of the mandibular foramen, in relation to the skull size and the mandibular size in different-aged bottlenose dolphins, Tursiops truncatus (18 females between 1 and 42 yr, 17 males between 1 and 32 yr). The minimum thickness was absolutely at its lowest at the most posterior transect T1, but did not vary significantly between the sexes or between the ages. The minimum thickness varied significantly at the two most anterior transects, T3 and T4, both between the sexes and among the ages. The thickness increased throughout life among males, whereas in females it first increased and then starts to decrease around the age of 20.
Nummela S; Kosove J E; Lancaster T E; Thewissen J G M
Marine Mammal Science
2004
2004-07
Journal Article
<a href="http://doi.org/10.1111/j.1748-7692.2004.tb01174.x" target="_blank" rel="noreferrer noopener">10.1111/j.1748-7692.2004.tb01174.x</a>
Age estimation in bowhead whales using tympanic bulla histology and baleen isotopes
Arctic; Balaena; Balaena mysticetus; bone; carbon; corpora; GLGs; growth; LAGs; layers; Marine & Freshwater Biology; minke whales; stable isotopes; tympanic bulla; Zoology
Tympanic bullae and baleen plates from bowhead whales of the Western Arctic population were examined. Growth layer groups (GLGs) in the involucrum of the tympanic bone were used to estimate age of the whales, and compared to stable isotope signatures along transects of baleen plates and the involucrum. The involucrum of the tympanic bone consists of three regions that form in utero, during nursing in the first year, and during the first decades of life, respectively. Life history events, such as annual migration, are recorded in the bowhead tympanic bulla. It is likely that bone growth in the bowhead tympanic occurs during periods of high food intake, while slow or arrested growth occurs during periods of low food intake. Comparisons between numbers of GLGs in the tympanic, number of isotopic oscillations in a baleen plate, length of the baleen plate, and total whale length show correlation coefficients as high as 0.97. The tympanic GLG method is particularly useful for estimating the age of whales up to 20 yr old.
Sensor J D; George J C; Clementz M T; Lovano D M; Waugh D A; Givens G H; Suydam R; Stimmelmayr R; Thewissen J G M
Marine Mammal Science
2018
2018-04
Journal Article
<a href="http://doi.org/10.1111/mms.12476" target="_blank" rel="noreferrer noopener">10.1111/mms.12476</a>
Olfaction and brain size in the bowhead whale (Balaena mysticetus)
anatomy; attraction; Balaena mysticetus; bowhead whale; brain; cetaceans; dimethyl sulfide; evolution; evolutionary dynamics; Marine & Freshwater Biology; olfaction; olfactory; primates; receptor gene repertoires; receptor genes; reduction; seabirds; subgenome; vertebrates; Zoology
P>Although there are several isolated references to the olfactory anatomy of mysticetes, it is usually thought that olfaction is rudimentary in this group. We investigated the olfactory anatomy of bowhead whales and found that these whales have a cribriform plate and small, but histologically complex olfactory bulb. The olfactory bulb makes up approximately 0.13% of brain weight, unlike odontocetes where this structure is absent. We also determined that 51% of olfactory receptor genes were intact, unlike odontocetes, where this number is less than 25%. This suggests that bowheads have a sense of smell, and we speculate that they may use this to find aggregations of krill on which they feed.
Thewissen J G M; George J; Rosa C; Kishida T
Marine Mammal Science
2011
2011-04
Journal Article
<a href="http://doi.org/10.1111/j.1748-7692.2010.00406.x" target="_blank" rel="noreferrer noopener">10.1111/j.1748-7692.2010.00406.x</a>