Extreme biomineralization: the case of the hypermineralized ear bone of gray whale (Eschrichtius robustus)

Selected hypermineralized bones (rostrum and tympanic bullae) have yet to be characterized for diverse species of whales (Cetacea). Hypermineralization in these structures is an example of extreme biomineralization that, however, occurs at temperatures around 36 °C. In this study we present the results of analytical investigations of the specimen of tympanic bulla isolated from gray whale (Eschrichtius robustus) for the first time. Examination of the internal surface of the bone mechanically crushed under a press revealed the presence of a lipid-containing phase, which did not disappear even after complete demineralization of the bone material. Additionally, analytical investigations including CARS, ATR-FTIR, Raman and XRD confirmed the presence of carbonated bioapatite and a collagen- lipid complex as the main components of this up to 2.34 kg/cm3 dense bone. Our experimental results open the way for further research on understanding of the principles of hypermineralization in highly specialized whale bones.

Growth and development of North Pacific gray whales (Eschrichtius robustus)

Understanding variability in growth patterns of marine mammals provides insights into the health of individuals and status of populations. Body growth of gray whales (Eschrichtius robustus) has been described for particular life stages, but has not been quantified across all ages. We derived a comprehensive growth equation for gray whales by fitting a two-phased growth model to age-specific length data of eastern North Pacific gray whales that were captured, stranded, or harvested between 1926 and 1997. To predict mass-at-age, we used the allometric relationship between mass and length. We found that on average (± SD), calves were 4.6 ± 0.043 m and 972 ± 26 kg at birth, and reached 8.5 ± 0.095 m and 6,019 ± 196 kg by the end of their first year of life (n = 118). Thus, calves almost double (2×) in length and octuple (8×) in mass while nursing, and are effectively about two-thirds of their asymptotic adult length and one-third of their maximum mass when weaned. The large sample of aged individuals (n = 730) indicates that gray whales live up to ~48 years and have a life expectancy of < 30 years. Adult females attain a mean (± SD) asymptotic size of 13.1 ± 0.048 m and 20,758 ± 222 kg, while the smaller males average 12.6 ± 0.048 m and 19,938 ± 222 kg at ~40 years of age. Females are thereby ~4% longer and heavier than males. These age-specific estimates of body size can be used to estimate food requirements and assess nutritional status of individuals.