Hidehiro Kato

Molecular evidence from retroposons that whales form a clade within even-toed ungulates

The origin of whales and their transition from terrestrial life to a fully aquatic existence has been studied in depth. Palaeontological,, morphological and molecular studies suggest that the order Cetacea (whales, dolphins and porpoises) is more closely related to the order Artiodactyla (even-toed ungulates, including cows, camels and pigs) than to other ungulate orders. The traditional view that the order Artiodactyla is monophyletic has been challenged by molecular analyses of variations in mitochondrial and nuclear DNA. We have characterized two families of short interspersed elements (SINEs) that were present exclusively in the genomes of whales, ruminants and hippopotamuses, but not in those of camels and pigs. We made an extensive survey of retropositional events that might have occurred during the divergence of whales and even-toed ungulates. We have characterized nine retropositional events of a SINE unit, each of which provides phylogenetic resolution of the relationships among whales, ruminants, hippopotamuses and pigs. Our data provide evidence that whales, ruminants and hippopotamuses form a monophyletic group.

Mitochondrial Phylogenetics and Evolution of Mysticete Whales

The phylogenetic relationships among baleen whales (Order: Cetacea) remain uncertain despite extensive research in cetacean molecular phylogenetics and a potential morphological sample size of over 2 million animals harvested. Questions remain regarding the number of species and the monophyly of genera, as well as higher order relationships. Here, we approach mysticete phylogeny with complete mitochondrial genome sequence analysis. We determined complete mtDNA sequences of 10 extant Mysticeti species, inferred their phylogenetic relationships, and estimated node divergence times. The mtDNA sequence analysis concurs with previous molecular studies in the ordering of the principal branches, with Balaenidae (right whales) as sister to all other mysticetes base, followed by Neobalaenidae (pygmy right whale), Eschrichtiidae (gray whale), and finally Balaenopteridae (rorquals + humpback whale). The mtDNA analysis further suggests that four lineages exist within the clade of Eschrichtiidae + Balaenopteridae, including a sister relationship between the humpback and fin whales, and a monophyletic group formed by the blue, sei, and Brydes whales, each of which represents a newly recognized phylogenetic relationship in Mysticeti. We also estimated the divergence times of all extant mysticete species, accounting for evolutionary rate heterogeneity among lineages. When the mtDNA divergence estimates are compared with the mysticete fossil record, several lineages have molecular divergence estimates strikingly older than indicated by paleontological data. We suggest this discrepancy reflects both a large amount of ancestral polymorphism and long generation times of ancestral baleen whale populations.

Persistent organochlorines in minke whale (Balaenoptera acutorostrata) and their prey species from the Antarctic and the North Pacific.

Persistent organochlorines such as polychlorinated biphenyls (PCBs), DDTs, chlordane compounds (CHLs), hexachlorocyclohexanes (HCHs) and hexachlorobenzene (HCB) were determined in the blubber of minke whale and its diet collected from the Antarctic and the North Pacific Oceans. Residue levels of these compounds (except HCB) in minke whale from the Antarctic were apparently lower than those from the North Pacific. This is due to the lower levels of these pollutants in the southern hemisphere than in the northern hemisphere and the specific feeding habit of the minke whale from the Antarctic which feeds on lower trophic organisms, primarily euphausiids. The north-south difference for HCB residue levels was small, reflecting its dispersible nature through long-range atmospheric transport. Compositions of DDT and CHL compounds in minke whale from the Antarctic were similar to those from the North Pacific. However, the composition of HCH isomers was different between the Antarctic and the North Pacific as was observed in their diet, suggesting a larger or on-going usage of lindane in the southern hemisphere countries. In minke whale from the Antarctic, the elevated level of PCBs residues was noted during a period of 1984 to 1993, implying a continuous discharge of PCBs in the southern hemisphere. A similar discharge was also suggested in the North Pacific, while a decreasing contamination by DDTs was apparent.

Heavy metal accumulations and their recent changes in southern minke whalesBalaenoptera acutorostrata

The concentrations of heavy metals in the livers of southern minke whales,B. acutorostrata, were determined by atomic absorption spectrophotometry, and their accumulation levels and variations were compared to food habit, and biological parameters. The concentration levels and bioconcentration factors of metals in the minke whale were relatively high for Fe and Cd and low for Hg, when compared to seals and small-toothed cetaceans from different waters. For most of the metals examined, the concentrations were log-normally distributed. The concentrations of Fe, Cd, and Hg were positively correlated with age, but a correlation was not observed for the other metals. While the hepatic Fe concentration linearly increased with age, the concentrations of Cd and Hg increased up to the age of about 20 years and thereafter decreased year by year. Such unusual age trends of Cd and Hg are considered to be due to recent changes of the amount of food intake by the minke whale, as a result of structural disturbances in the Antarctic marine ecosystem due to commercial whaling. Also, the hepatic concentrations of metals varied between sexes, and with reproductive status of the matured female; the concentration of Fe was lower in the females than the males, and Fe, Pb, Ni, and Co concentrations in the matured females decreased with progress of gestation.

Bryde's Whales: Balaenoptera edeni/brydei

Publisher Summary This chapter describes the Brydes whale, least known of the large baleen whales. Brydes whales are medium-sized balaenopterids. They were long confused with sei whales ( Balaenoptera borealis ) because of morphological similarities; this confusion lasted into the 1970s. Brydes whales were first described based on examination of a stranded balaenopterid on Thaybyoo Creek beach, Gulf of Marataban, Burma. Females are larger than males throughout life, by about 2 ft (0.5–0.6 m) at full maturity. It is believed they reach 15.5 m, but most are much smaller. As demonstrated for South African Brydes whales, animals from coastal stocks or stocks inhabiting rather areas are generally smaller than those from migratory pelagic stocks . Southern Hemisphere animals are also larger than Northern Hemisphere animals. In the South Africa and western North Pacific stocks, body length increases rapidly until 4–5 years, reaches about 90% of asymptotic length for both sexes at about 10 years, and ceases to increase at about 20–25 years. If mean lengths at physical maturity in the western North Pacific stock are substituted into the equation, weight estimates are 15.0 (at 13.0 m) and 16.6 (at 13.5 m) tons for males and females, respectively. Brydes whales do not gather into large groups. They are usually seen singly or in groups of 2–3 in the North Pacific, with a maximum group size of 12. Although Brydes whales have a life history similar to that of other balaenopterids, there are species-specific aspects due to the fact that they remain in tropical and temperate waters throughout the year.

Detection of heterogeneity and estimation of population characteristics from the field survey data: 1987/88 Japanese feasibility study of the southern hemisphere Minke whales

To get reliable information of the age structure of whale population, Japan conducted a feasibility study of scientific research in the Antarctic in 1987/88. Though the sample was not large enough, it was the first data free from the problem of selectivity and whaling ground bias. From the analysis, it was found that the biological characteristics are highly heterogeneous spatially or other ways. Considering this, we recognize that the survey should be designed to collect the sample from the whole research area uniformly to obtain unbiased estimates of population characteristics. However, in an actual biological field survey, it is difficult to keep the sampling fractions thecisely the same for each sampling units. Therefore, it is important to detect the heterogeneity in the sample, and poststratify the data corresponding to the heterogeneity. The methodology of the estimation and model evaluation presented here will be useful for the development of biological field survey in general.

A study on the improvement of age estimation in common minke whales using the method of gelatinized extraction of earplug

We attempted to settle the potential problems of bias caused by too soft earplugs and poor formation of the growth layers in age readings of common minke whales. Thus, we examined the feasibility of a new technique of incorporating gelatin in order to collect earplugs for age assessment. Frozen sectioning and histology of the earplug core were also used as methods to improve age estimation. Earplugs were collected by filling the space in the external auditory meatus with gelatin, hardening the gelatin, earplug and its fragments, by spraying with cooling gas, and removing the earplug embedded in gelatin. In 174 trials with common minke whales in the Western North Pacific of coastal waters of Japan in 2007–2009, it was revealed that embedding earplugs with gelatin minimized breakage and protected the neonatal line (NL). This method was particularly effective in younger animals. As a result, the readability was improved. We also examined the histological sections, which were sliced using the Kawamoto specialized frozen sectioning technique, and stained them separately with toluidine blue, haematoxylin and eosin, Sudan III, Sudan VII, and alizarin red S to display a clearer core surface image of the growth layers. The histological sections stained with alizarin red S provided the clearest images, in which we could easily identify both dark and pale laminations. This suggested a close relationship with the seasonal changes in calcium intake from feeding. Earlier age estimation methods focused on fat content in the growth layers; however, we found potential for an improvement in the readability of unclear growth layers when focusing on calcium.

Detection and characterization of whale signals using seafloor cabled seismic networks offshore Japan

Ocean ambient noises against seismic signals are well studied using archived waveforms recorded on three-component seismometers and hydrophones connected to a seafloor cabled seismic network off Kushiro, Hokkaido, Japan basically facing the Pacific Ocean. The system was deployed to install in late July 1999 by Japan Agency for Marine-Earth Science and Technology (JAMSTEC). Outstanding “noises” at frequency bands of 15-30 Hz are recorded on all components of both seismometers and hydrophones, which are directly recognized as fin whale calls in comparison with in-situ visual surveys carried in September to October 2009. It is extremely conspicuous that a seasonal variation of the fin whale calls has been revealed in ambient noise spectrograms of continuous longterm waveform records from 2009 to 2013. High-intensity signals associated with the fin whale calls appear commonly in the periods from September to February over cold winter at high latitudes. The remarkable seasonal pattern should be corresponded to their annual living behavior and might be related to climate changes in the Pacific Ocean.

The first record of a true albino common bottlenose dolphin Tursiops truncatus from Japan

The common bottlenose dolphin Tursiops truncatus is found worldwide in temperate and tropical waters (Jefferson et al. 2008). It has a dark coloration, and the color pattern varies from light gray to black on the back and sides, fading to white on the belly (Fig. 1a) (Wells and Scott 1999; Jefferson et al. 2008). In general, the external body color and color pattern of wild animals are important to provide camouflage for reduced visibility to predators or to enhance the ability to hunt prey (Searle 1968; Hearing and Tsukamoto 1991). Analyses of coloration in cetaceans proposed several functions such as communication with conspecifics in addition to acquisition of prey and protection from predators (Perrin 2009). Skin color is also important for protecting the skin from damage by short-wavelength radiation, particularly ultraviolet B, and maintaining thermoregulatory ability through increased heat absorption on the skin surface (Searle 1968; Hearing and Tsukamoto 1991). Coloration in mammals is almost entirely dependent on the presence of melanin pigment in the skin, hair, and eyes (Hearing and Tsukamoto 1991). Albinism is caused by lack of melanin, leading to a pale skin color and red or pink color of the eyes due to blood vessels that can be observed through colorless tissue (van Grouw 2006). However, if the production of melanin is reduced but not entirely blocked, it can result in leucism, in which the skin and hair are white, whereas the eyes are colored normally (reviewed in Fertl and Rosel 2009). Despite strong selection pressures against albino and leucistic animals, anomalously white animals have been recorded in many mammalian species, including cetaceans (Fertl and Rosel 2009). Fertl et al. (1999, 2004) reviewed at least 20 different cetacean species with anomalously white pigmentation. Among common bottlenose dolphins, 13 anomalously white dolphins including three true albino have been previously reported worldwide since the first report in 1962 (Table 1). These reports are almost always based on sighting records of animals at sea; therefore, live capture and rearing of these anomalously white cetaceans in aquaria are quite rare. Here, we report basic information of an anomalously white dolphin found and live-captured in Japan for identify true albino in common bottlenose dolphins.

Spatial and temporal variation of PCBs and organochlorine pesticides in the Antarctic minke whales, Balaenoptera bonaerensis, in the period 1987–2005

Concentrations of polychlorinated biphenyls (PCBs), dichlorodiphenyl trichloroethane and its metabolites (DDTs), hexachlorocyclohexane isomers (HCHs), hexachlorobenzene (HCB) and chlordane compounds (CHLs) were determined in the blubber of males (20-25 years old) of Antarctic minke whales, Balaenoptera bonaerensis, from the International Whaling Commission (IWC) management Areas IV (70°-130°E) and V (130°E-170°W), south 60°S. The ranges of concentrations (ng g(-1) lipid wt.) for each compound were, PCBs: 7.7-89; DDTs: 29-340; HCHs: 0.20-4.3; HCB: 75-430; CHLs: 10-120, which were much lower than those in common minke whales, Balaenoptera acutorostrata, from the northern hemisphere. The levels of PCBs, HCHs, HCB and CHLs in Area IV were significantly higher than those in Area V, while the levels of DDTs in both areas were similar. For comparing the fate among four pesticides in the Antarctic Ocean avoiding the effect of variance due to food intake, the ratios of the pesticides to PCBs, which has an extremely high chemical stability and environmental persistence, were examined. The HCHs/PCBs ratio decreased by a factor of about 20 in a span of 16 years in both Areas IV and V, while temporal trends of DDTs/PCBs, HCB/PCBs and CHLs/PCBs ratios were not observed. These results indicate that PCBs, DDTs, HCB and CHLs levels did not vary or slightly decreased in Areas IV and V during the study period. However HCHs levels clearly decreased. Spatial differences seems to be related to differences in food intake among whales, and temporal differences seems to be related to the length stay of OCs in the Antarctic Ocean.