Characterization of alpha-fetoprotein levels in three dolphin species: development of sensitive immunoassays for analysis of the pregnancy-associated variations.

A single radial immunodiffusion (SRID) assay and a chemiluminescent immunoassay (CLIA) were initially developed for alpha-fetoprotein (AFP) of the striped dolphin. Utilizing these developed assays, we investigated pregnancy-associated changes in the levels of AFP in the sera of fetuses and pregnant females of three dolphin species; samples were either collected from captive individuals or obtained as fishery by-products. The concentrations of AFP in the fetal serum ranged from 419.0 to 2026.3 µg/ml in the striped dolphin, 12.6 to 1218.7 µg/ml (for an AFP equivalent; eqAFP) in the common bottlenose dolphin and 770.6 to 3129.1 µg eqAFP/ml in the Risso's dolphin. AFP levels decreased with increased fetal size in fetuses over 20 cm in length. The concentrations of AFP in sera of pregnant females ranged from 7.18 to 8068.7 ng/ml in the striped dolphin, 6.6 to 1241.1 ng eqAFP/ml in the common bottlenose dolphin and 3.4 to 2868.7 ng eqAFP/ml in the Risso's dolphin. The levels in most pregnant females were equal to or lower than those found in males and nonpregnant individuals, although a few pregnant females exhibited extremely high levels (in the range of hundreds to thousands of nanograms per milliliter). Such high levels of AFP were not observed during pseudopregnancy. To our knowledge, this is the first report on basal profiles for serum AFP levels in small odontocetes. The profiles indicated that AFP may play a significant role during embryonic development, although maternal levels do not appear to be a diagnostic biomarker for monitoring pregnancy.

Sleep behaviour: sleep in continuously active dolphins.

Sleep has been assumed to be necessary for development and to be a vital function in mammals and other animals. However, Lyamin et al. claim that in bottlenose dolphins (Tursiops truncatus) and killer whales (Orcinus orca), neonates and their mothers show almost no sleep behaviour for the first month after birth; this conclusion is based on their observation that the cetaceans keep swimming, avoid obstacles and rarely close their eyes for 24 hours a day throughout that period. Here we analyse the behaviour and eye closure of three neonate-mother pairs of bottlenose dolphins and find that, although the animals tend to open both eyes when surfacing to breathe, one or both eyes are closed during 'swim rest', an underwater sleeping behaviour that is associated with continuous activity. This observation calls into question the conclusions of Lyamin et al., who overlooked this type of sleep by analysing the animals' eye state only when they surfaced to breathe.

Growth, maturity, reproduction, and life expectancy in ex-situ pacific walruses (Odobenus rosmarus divergens).

BACKGROUND: Pacific walruses are found in Arctic regions of the Chukchi and Bering Sea where rapid changes in environmental conditions resulting in loss of sea ice are occurring. Therefore, accurate life history data are crucial for species management plans and longitudinal data collected over the lives of individual walruses housed in zoos and aquaria provide otherwise difficult to obtain biological information. RESULTS: While similar at birth, Gompertz regression curves indicated that males grew faster than females (p < 0.0001) in weight (99 kg vs 57.6 kg/y) and length (26.9 cm vs 26.3 cm/y) with physical differences being detected by age 3 for weight and age 7 for length. Males reached adult weight at 13.5 ± 3.3 y and females by age 12.3 ± 2.3 y. The mean age at first ovulation and at first conception occurred at 8.8 y and 9.6 y. Greater than 75% of all conceptions and calving occurred between February and March and from May to June, respectively. Mean gestation lasted 423 d and false pregnancies lasted at least 169 d with a decrease (p < 0.05) in serum progesterone concentration between false pregnancy and pregnancy occurring within 6 months after ovulation. Based on these results, we estimated embryonic diapause to last from 120 to 139 days, and fetal growth last ~ 284 days. All males older than 8 y had an increase in serum testosterone and body weight that was highest in February and lowest in July. Overall, no differences were observed between male and female survival, with a mean (± SEM) life expectancy of 19.5 ± 1.5 y, respectively. Currently, the oldest male and female captive walruses are 40 and 43 y, respectively. CONCLUSIONS: Data provided herein include details of life history characteristics of zoo and aquaria housed walruses that are useful for wild population recovery models. In particular, results on survivorship and the identification of the most vulnerable period for calf survival can help with model development and suggests that for recovery to occur birthing locations for this species must be protected.

Spontaneous establishing of cross-modal stimulus equivalence in a beluga whale.

Beluga whales use calls to convey various information to group members. Is this communication similar to humans? We addressed this question by using the framework of stimulus equivalence. Stimulus equivalence consists of three phases: if the animal is trained to match A to B and B to C, symmetry is demonstrated by matching BA and CB, transitivity by matching AC, and equivalence by matching CA. We tested the spontaneous establishment of cross-modal stimulus equivalence between visual and auditory symbols in a beluga whale nicknamed Nack. Nack could make symmetrical choices in novel objects untrained. Moreover, visual/auditory cross-modal transitivity was formed spontaneously. Nack succeeded in six tasks, including an untrained task concerning stimulus equivalence. We conclude that Nack spontaneously formed cross-modal stimulus equivalence between visual and auditory symbols. Cross-modal stimulus equivalence was considered to exist only in humans because of linguistic faculty; however, Nack exhibited the same understanding as humans.

Circulating gonadotropins and testicular hormones during sexual maturation and annual changes in male bottlenose dolphins (Tursiops truncatus).

To reveal the reproductive biology in male bottlenose dolphins (Tursiops truncatus), circulating gonadotropins (follicle stimulating hormone [FSH] and luteinizing hormone [LH]) and testicular hormones (testosterone and inhibin) were monitored for 8-12 years in 2 captive bottlenose dolphins (Mars and Regulus). During the study period, Mars was undergoing sexual maturation, whereas Regulus was already mature at the beginning of the study. Assuming that Mars had reached sexual maturity when the significant increase in circulating testosterone levels was observed, serum concentration of inhibin was higher in the sexually immature stage than in the mature stage, whereas the serum concentration of FSH was higher in the sexually mature stage than in the immature stage. No difference was observed in the LH levels between pre- and post-sexual maturation. There was a significant increase in serum concentration of testosterone during spring in both animals. These results suggest that the mechanism responsible for regulating FSH secretion by inhibin functions during the sexually immature stage in this species.

Circulating testosterone and inhibin levels at different ages in the male beluga (Delphinapterus leucas).

This study is the first report on circulating testosterone and inhibin levels in a species of whales, the beluga. Circulating testosterone and immunoreactive (ir-) inhibin levels in two captive male belugas ("Nack", originally from Canada and "Duke", from the Okhotsk Sea) were measured every month for 9 years between 1995 and 2003. Assuming that clearly increased testosterone levels in the circulation indicates that the belugas had reached sexual maturity, at the ages of 10 ("Nack") and 11 years old ("Duke"). Their testosterone levels before the significant increase (pre-pubertal) were 0.42 ± 0.07 ng/ml (n=18) and 0.35 ± 0.10 ng/ml (n=18) and, those of after the increase (maturity) were 1.65 ± 0.14 ng/m l (n=74) and 2.06 ± 0.14 ng/ml (n=74). Circulating ir-inhibin levels before sexual maturity were 0.78 ± 0.04 ng/ml (n=18) and 0.64 ± 0.04 ng/ml (n=15) and, after sexual maturity were 0.52 ± 0.02 ng/ml (n=56) and 0.43 ± 0.02 ng/ml (n=67). Seasonal changes were observed in the testosterone levels after sexual maturity and the levels increased during March and April in Canadian origin "Nack", and peaked in February in Okhotsk origin "Duke". Circulating ir-inhibin level gradually decreased as they aged. A negative correlation between the circulating testosterone and ir-inhibin was observed. No seasonal changes were observed in the ir-inhibin levels after sexual maturity. These data will surely correspond to clarification of endocrinology and the successful reproduction of the beluga.