Stretchy nerves are an essential component of the extreme feeding mechanism of rorqual whales.
Rorqual whales (Balaenopteridae) are among the largest vertebrates that have ever lived and include blue (Balaenoptera musculus) and fin (Balaenoptera physalus) whales. Rorquals differ from other baleen whales (Mysticeti) in possessing longitudinal furrows or grooves in the ventral skin that extend from the mouth to the umbilicus. This ventral grooved blubber directly relates to their intermittent lunge feeding strategy, which is unique among vertebrates and was potentially an evolutionary innovation that led to gigantism in this lineage [1]. This strategy involves the rorqual whale rapidly engulfing a huge volume of prey-laden water and then concentrating the prey by more slowly expelling the water through baleen plates (Figure 1A). The volume of water engulfed during a lunge can exceed the volume of the whale itself [2]. During engulfment, the whale accelerates, opens its jaw until it is almost perpendicular to the rostrum, and then the highly compliant floor of the oral cavity is inflated by the incoming water [3]. The floor of the oral cavity expands by inversion of the tongue and ballooning of the adjacent floor of the mouth into the cavum ventrale, an immense fascial pocket between the body wall and overlying blubber layer that reaches as far back as the umbilicus. The ventral grooved blubber in fin whales expands by an estimated 162% in the circumferential direction and 38% longitudinally [4]. In fin whales, multiple lunges can occur during a single dive, and the average time between lunges is just over forty seconds [3]. Here, we show that nerves in the floor of the oral cavity of fin whales are highly extensible.
Department of Cellular and Physiological Sciences, Faculty of Medicine, University of British Columbia, Vancouver, B.C. Canada V6T 1Z3. Electronic address: vogl@mail.ubc.ca.
A Wayne
AW
Vogl
Department of Zoology, Faculty of Science, University of British Columbia, Vancouver, B.C. Canada V6T 1Z4.
Margo A
MA
Lillie
Department of Zoology, Faculty of Science, University of British Columbia, Vancouver, B.C. Canada V6T 1Z4.
Marina A
MA
Piscitelli
Hopkins Marine Station, Department of Biology, Stanford University, 120 Oceanview Boulevard, Pacific Grove, California 93950, USA.
Jeremy A
JA
Goldbogen
Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, 10th & Constitution NW Washington, DC 20560-0121, USA.
Nicholas D
ND
Pyenson
Department of Zoology, Faculty of Science, University of British Columbia, Vancouver, B.C. Canada V6T 1Z4.
Robert E
RE
Shadwick
D000818:Animals; D050616:Balaenoptera / Q000502:physiology*; D005247:Feeding Behavior / Q000502:physiology*; D014059:Tongue / Q000294:innervation*