Bimodal distribution of inter-individual distance in free-ranging narrow-ridged finless porpoises.

Inter-individual distance (IID) is an important indicator of social organisation because solitary species are spatially intolerant towards conspecifics, whereas group-living species are usually gregarious with collective behaviour. Therefore, by examining the relationship between the distribution of IIDs and the active space of cues or signals, and behaviours, we can predict their social organisation. The narrow-ridged finless porpoises (NRFPs) have been described as a solitary species; however, recent studies described NRFPs tend to live in groups more than alone.

Comprehensive expression analysis of hormone-like substances in the subcutaneous adipose tissue of the common bottlenose dolphin Tursiops truncatus.

Marine mammals possess a specific subcutaneous fat layer called blubber that not only insulates and stores energy but also secretes bioactive substances. However, our understanding of its role as a secretory organ in cetaceans is incomplete. To exhaustively explore the hormone-like substances produced in dolphin subcutaneous adipose tissue, we performed seasonal blubber biopsies from captive female common bottlenose dolphins (Tursiops truncatus; N = 8, n = 32) and analyzed gene expression via transcriptomics.

Association of seasonal changes in circulating cortisol concentrations with the expression of cortisol biosynthetic enzymes and a glucocorticoid receptor in the blubber of common bottlenose dolphin.

Cortisol is secreted from the adrenal cortex in response to stress, and its circulating levels are used as robust physiological indicators of stress intensity in various animals. Cortisol is also produced locally in adipose tissue by the conversion of steroid hormones such as cortisone, which is related to fat accumulation. Circulating cortisol levels, probably induced by cold stress, increase in cetaceans under cold conditions.

Blubber biopsy in common bottlenose dolphins using a novel biopsy puncher: Evaluation of the impact on living individuals and possibility of applications in cetacean research.

Biopsy has recently become a preferred protocol for sampling the skin and blubber of many cetacean species, although it is desirable to collect as minimally invasive as possible. Here, the effect of biopsy sampling on the captive common bottlenose dolphins was evaluated by analyzing the process of wound healing and changes in hematological and blood biochemical parameters after biopsy using a puncher developed to collect up to the inner layer of the dolphin blubber. Results showed that the wounds caused by biopsy were closed in as early as 1 day and completely covered with the epidermis within 5-11 days.

Non-invasive age estimation based on faecal DNA using methylation-sensitive high-resolution melting for Indo-Pacific bottlenose dolphins.

Age is necessary information for the study of life history of wild animals. A general method to estimate the age of odontocetes is counting dental growth layer groups (GLGs). However, this method is highly invasive as it requires the capture and handling of individuals to collect their teeth.

Helicobacter delphinicola infection and the risk of gastric disease in common bottlenose dolphin.

Gastritis and gastric ulcers are well-recognized conditions in cetaceans; bacteria of the genus Helicobacter are considered the primary cause of these diseases. Dolphins have been shown to be susceptible to infection by at least 2 gastric species of Helicobacter, H. cetorum and H.

Yawn-like behavior in captive common bottlenose dolphins (Tursiops truncatus).

Yawning is an involuntary action that begins with a slow opening of the mouth with inhalation, followed by a maximum gaping phase, and ends with a short exhalation and the closing of the mouth. A wide variety of vertebrate species, including humans, yawn. Here, we report underwater yawn-like behavior in three captive common bottlenose dolphins, inferred from 119-h of observations.

Helicobacter delphinicola sp. nov., isolated from common bottlenose dolphins Tursiops truncatus with gastric diseases.

Gastritis and gastric ulcers are well-recognized symptoms in cetaceans, and the genus Helicobacter is considered as the main cause. In this study, we examined the gastric fluid of captive common bottlenose dolphins Tursiops truncatus with gastric diseases in order to isolate the organisms responsible for diagnosis and treatment. Four Gram-negative, rod-shaped isolates (TSBT, TSH1, TSZ, and TSH3) with tightly coiled spirals with 2-4 turns and 2-6 bipolar, sheathed flagella, were obtained from gastric fluids of common bottlenose dolphins with gastric diseases.

Development of an analytical method to exclude the effect of decomposition on carbon and nitrogen stable isotope ratios using muscle samples collected from stranded narrow-ridged finless porpoise (Neophocaena asiaeorientalis).

Unlabelled: Carbon and nitrogen stable isotope ratios (i.e., δ C and δ N values) in soft tissues of cetaceans are reported to change on decomposition.

Long-term monitoring of circulating progesterone and its relationship to peripheral white blood cells in female false killer whales Pseudorca crassidens.

Long-term monitoring of circulating progesterone levels in three captive female false killer whales, Pseudorca crassidens, was conducted to characterize their reproductive events and to reveal the relationship between their estrous cycles or pregnancies and peripheral white blood cell (WBC) counts. Blood samples were collected at 2-3-day intervals or on a weekly-to-monthly basis for up to 10 years, from 2006 to 2017. In two mature females (initial body lengths of 4.

Seasonal changes in circulating gonadal steroid levels and physiological evidence for the presence of intrinsic circannual reproductive cycles in captive finless porpoises Neophocaena asiaeorientalis from the western Inland Sea, Japan.

We monitored annual fluctuations of gonadal steroid levels in three sexually mature captive finless porpoises (Neophocaena asiaeorientalis; two males and one female) from two different facilities over 56-91 months. Two animals (one male and one female) were held in an indoor tank with a sunroof (facility A) and the other male was held in an indoor tank without a sunroof (facility B). Water temperatures in both facilities reflected seasonal changes during the study period with a minor difference in the fluctuation pattern.

Molecular identification of novel alpha- and gammaherpesviruses from cetaceans stranded on Japanese coasts.

Herpesviral infections have been documented in some cetaceans; however, they have not yet been identified in species in the western North Pacific. In the present study, 178 tissue samples from 76 stranded cetacean individuals were tested for the presence of herpesviruses. Herpesvirus genomic DNA fragments surrounding the DNA polymerase gene were amplified in samples from four individuals.

Temporal and spatial trends of organotin contamination in the livers of finless porpoises (Neophocaena phocaenoides) and their association with parasitic infection status.

Organotins (OTs) are globally ubiquitous contaminants. Contamination of OTs, particularly butyltins (BTs), has been suspected to cause immunosuppressive effects leading to subsequent infectious diseases or opportunistic infection by pathogens in marine mammals. In the present study, we collected individuals from five different populations of finless porpoises (Neophocaena phocaenoides) from coastal areas of Japan (Seto Inland Sea, Ise Bay, Omura Bay, and Pacific coast) and Hong Kong, and measured OT concentrations in their livers.

Natriuretic peptides in cetaceans: identification, molecular characterization and changes in plasma concentration after landing.

Dolphins are aquatic animals free from gravity, and this may have imposed significant changes in their cardiovascular status and its hormonal regulation compared with terrestrial animals. This study molecularly characterized two major cardiovascular hormones, atrial and B-type natriuretic peptides (ANP and BNP) and measured their changes in dolphin plasma concentrations in relation to the cardiovascular status of the animal. We initially identified ANP and BNP in three species of dolphins (Lagenorhynchus obliquidens, Phocoenoides dalli and Tursiops truncatus).

Bioaccumulation, temporal trend, and geographical distribution of synthetic musks in the marine environment.

Bioaccumulation of synthetic musks in a marine food chain was investigated by analyzing marine organisms at various trophic levels, including lugworm, clam, crustacean, fish, marine mammal, and bird samples collected from tidal flat and shallow water areas of the Ariake Sea, Japan. Two of the polycyclic musks, HHCB and AHTN, were the dominant compounds found in most of the samples analyzed, whereas nitro musks were not detected in any of the organisms, suggesting greater usage of polycyclic musks relative to the nitro musks in Japan. The highest concentrations of HHCB were detected in clams (258-2730 ng/g lipid wt.

Population differentiation in the Pacific white-sided dolphin Lagenorhynchus obliquidens inferred from mitochondrial DNA and microsatellite analyses.

We investigated genetic diversity and differentiation of the Pacific white-sided dolphin (Lagenorhynchus obliquidens) in Japanese coastal waters and offshore North Pacific by analyzing mitochondrial DNA and nuclear microsatellite variation. A total of 519 bp of the mitochondrial control region was sequenced and five microsatellite locus were genotyped for 59 individuals. A high level of haplotypic diversity (h=96.

Genetic structure of a Japanese allotetraploid loach of the genus Cobitis (Osteichthyes, Cobitidae).

The Japanese allotetraploid spined loach of the genus Cobitis "yamato complex" sensu SAITOH et al. (2000), distributed in Western Japan, originated from hybridization between C. biwae on the maternal side and C.

Diurnal and annual changes in serum cortisol concentrations in Indo-Pacific bottlenose dolphins Tursiops aduncus and killer whales Orcinus orca.

Until present, fundamental studies on cortisol secretory patterns have not been conducted in cetaceans. The objectives of this study were: (1) to examine diurnal changes in serum cortisol concentrations in Indo-Pacific bottlenose dolphins Tursiops aduncus and killer whales Orcinus orca, (2) to investigate annual cortisol changes in killer whales, and (3) to investigate the relationship between cortisol and sex steroids (testosterone and progesterone) concentrations in killer whales. Diurnal changes in serum cortisol concentrations were investigated at various intervals in the two species.