Interchanges and movements of humpback whales in Japanese waters: Okinawa, Ogasawara, Amami, and Hokkaido, using an automated matching system.

Humpback whales in the western North Pacific are considered endangered due to their small population size and lack of information. Although previous studies have reported interchanges between regions within a population, the relationship between the geographic regions of a population in Japan is poorly understood. Using 3,532 fluke photo IDs of unique individuals obtained from four areas in Japan: Hokkaido, six IDs (2009-2019); Ogasawara, 1,477 IDs, from two organizations (1) Everlasting nature of Asia (1987-2020) and (2) Ogasawara Whale Watching Association, (1990-2020); Amami, 373 IDs (1992-1994, 2005-2016); Okinawa, 1,676 IDs (1990-2018), interchanges were analyzed. The ID matchings were conducted using an automated system with an 80.9% matching accuracy. Interchange and within-region return indices were also calculated. As a result, number of matches and interchange indices follow locations, Hokkaido-Okinawa (3, 0.31), Amami-Ogasawara (36, 0.06), Amami-Okinawa (222, 0.37), and Okinawa-Ogasawara (225, 0.08), respectively. Interchange indices among Japanese areas were much higher than the indices between Ogasawara/Okinawa and Hawaii (0.01) and Mexico (0.00) reported in previous studies, indicating that the Japanese regions are utilized by the same population. At the same time, the frequency of interchanges among the three breeding areas vary, and the high within-region return indices in respective breeding areas suggest the site fidelity of the whales in each area at some level. These results indicate the existence of several groups within the population which are possibly be divided into at least two groups based on geographical features: one tend to utilize Ogasawara and the Mariana Archipelago; the other utilize Amami, Okinawa, and the Philippines, migrating along the Ryukyu and Philippine Trench. The matching results also suggest that Hokkaido is possibly be utilized as a corridor between northern feeding areas and southern breeding areas at least by individuals migrating to Okinawa area.

Distribution and Local Movement of Humpback Whales in Okinawan Waters Depend on Sex and Reproductive Status.

The distribution and local movement patterns of humpback whales in waters off the west coast of Okinawa Island, southwest Japan, were investigated using line transect and photo-identification methodologies. Line transect surveys were conducted from 2011 to 2014 and photo-identification survey from 2006 to 2012. During the surveys, humpback whales aggregated in the areas around Ie and Kerama Islands, and tended to travel along the inshore coast of Okinawa Island when they move locally between those two sites. A total of 496 humpback whales of the known sex were photo-identified (322 males, 75 females and 99 females with a calf). Of these, 24.8% were confirmed moving locally between the sites of Ie and Kerama Islands within the same season. Frequency rates of the local movement for males, females and females with a calf were 41.9, 25.0, and 15.1%, respectively; the frequency of local movement for males was significantly higher than that for females and females with a calf. These results indicate that male humpback whales tend to move more actively between the local breeding sites as compared to females and females with a calf. We speculate that the males search for more opportunities to mate, whereas females with a calf tend to remain in the same areas to nurse their calves. These findings extend our knowledge of the habitat use and reproductive ecology of humpback whales in Okinawan waters, which remain poorly understood.

Live-bearing manta ray: how the embryo acquires oxygen without placenta and umbilical cord.

We conducted an ultrasonographic experiment on a pregnant manta ray, Manta alfredi (Chondrichthyes, Batoidea). This study showed how the embryo of the live-bearing elasmobranchs respires in the body of the female. In the embryonic stage, the manta ray embryo takes in uterine fluid by buccal-pumping. After birth, the manta ray shifts its respiratory mode from buccal-pumping to ram-ventilation. The rapid reduction of the spiracle size in the young manta ray may reflect this shift of respiratory mode. Unlike mammals or some carcharhinid sharks that acquire oxygen through a placenta and umbilical cord, the manta ray embryo does not have a direct connection with the mother. Thus, the manta ray embryo obtains oxygen by buccal-pumping of the uterine fluid, in the same way that the embryos of egg-laying species obtain oxygen from the water in the egg case. This finding extends our understanding of the diversity of embryonic respiratory systems in live-bearing vertebrates.

Candida albicans and C. tropicalis Isolates from the Expired Breathes of Captive Dolphins and Their Environments in an Aquarium.

Genotypes of Candida spp. isolated from exhalation of 20 dolphins, 11 water samples from captive pools, and 24 oral cavities of staff members in an aquarium using a combination of multiple drug resistance 1 gene (MDR1) and the internal transcribed spacer (ITS) 1 5.8s-ITS 2 regions of ribosomal RNA gene (ITS rDNA) sequences were studied. The holding ratios of the dolphins, captive pools, and staff members were 70, 90, and 29%, respectively. Isolated pathogenic yeast species common to the dolphins and environments were Candida albicans and C. tropicalis. Identical genotypes in both Candida spp. based on the combination of MDR1 and ITSrDNA were found in some dolphins, between a dolphin and a staff, among dolphins and environments, and among environments. The results indicated the diffusion and exchange of pathogenic yeasts at the aquarium among dolphins and environments. The isolates at the aquarium showed higher rates of resistance to azole antifungals compared to reference isolates.

Comparison of serum lipid compositions, lipid peroxide, alpha-tocopherol and lipoproteins in captive marine mammals (bottlenose dolphins, spotted seals and West Indian manatees) and terrestrial mammals.

Concentrations of serum lipid components, lipid peroxide (LPO) and alpha-tocopherol and electrophoretic patterns of lipoproteins in serum samples obtained from captive marine mammals and terrestrial mammals were compared. Serum concentrations of total cholesterol, free fatty acid, and phospholipid in fish-eating animals were significantly higher than those in manatees and cows. Serum LPO and alpha-tocopherol concentrations in the fish-eating animals were also significantly higher than those in manatees, cows and dogs. Different patterns of densitometric scans of low density lipoprotein (LDL) and a significantly lower percentage of LDL were demonstrated in the dolphins compared with the seals, cow and dogs. The concentration of LPO was significantly correlated with triglyceride and phospholipid concentrations in serum from the dolphins. These results suggest that triglyceride and phospholipid are susceptible to oxidative reaction in fish-eating animals. Evaluation of serum lipids, LPO and alpha-tocopherol concentrations is needed for nutritional husbandry for fish-eating animals.

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. In Indo-Pacific bottlenose dolphins, serum cortisol levels exhibited the same episodic fluctuations for 24 h as did diurnal terrestrial mammals: cortisol levels were lower at 18:00 h and higher in the early morning. In killer whales, cortisol concentrations continued to decrease until 18:00 h, after which they fluctuated, and then increased in the next morning. Annual changes in cortisol levels were investigated by collecting blood samples every two weeks from two male killer whales and a pregnant female one twice per day (during 09:00-10:00 and 16:00-17:00 h) throughout a one-year period. Regarding sera collected during 09:00-10:00 h from the female, cortisol concentrations showed cyclic changes having about 4-month intervals. In males, cortisol showed higher concentrations in winter and lower concentrations during the summer season. There was a negative correlation between cortisol and progesterone levels in the female and a negative correlation was also observed between cortisol and testosterone in male no. 2. In the female and male no. 1, cortisol levels during 09:00-10:00 h were significantly higher than those during 16:00-17:00 h, and their data are considered to support observations regarding diurnal changes in cortisol levels in the two cetacean species.