Interspecific variation of prevalence by Scaphanocephalus (Platyhelminthes: Trematoda: Heterophyidae) metacercariae in parrotfishes (Labridae: Scarini) from an Okinawan coral reef.

Metacercarial cysts of the parasite Scaphanocephalus (Platyhelminthes: Trematoda: Heterophyidae) are frequently found on the pectoral fins and skin of parrotfishes (Labridae: Scarini) inhabiting Okinawan coral reefs in southern Japan. The prevalence of metacercarial cysts in 30 parrotfish species was investigated and compared through a market survey. Although parasite prevalence differed between parrotfishes, all species examined are considered to be suitable hosts. Prevalence was high in Scarus chameleon (38.5%, n = 13), S. rubroviolaceus (33.4%, 2797), S. ghobban (26.6%, 6441), and several other species that share, in part, common feeding habits. Conversely, prevalence was low in S. prasiognathos (0.4%, 1842), Bolbometopon muricatum (0.4%, 270), and Hipposcarus longiceps (0.1%, 8512) which have different feeding habits. Despite a few exceptions, feeding ecology and other indirect behaviors are considered to affect the prevalence of metacercarial cysts in parrotfishes. Taxonomic affiliation and nocturnal mucous cocoon usage are not considered to affect parasite prevalence.

Pristipomoides amoenus (Snyder 1911), a valid species of jobfish (Pisces, Lutjanidae), with comparisons to P. argyrogrammicus (Valenciennes 1832).

Platyinius amoenus Snyder 1911 has long been considered a junior synonym of Pristipomoides argyrogrammicus (Valenciennes 1832), however, the two are discernible as distinct species from color patterns and counts of gill rakers based on examination of their type materials and non-type specimens. Furthermore, genetic differences based on molecular analysis among the two species (mtDNA, COI gene) strongly support the validity of both species. Pristipomoides amoenus can be readily distinguished from P. argyrogrammicus in having no white margin to the dorsal, anal, and caudal fins, silvery blue spots continuing inside dorso-lateral yellow blotches, and presence of modally10 (vs. modally 12) lower gill rakers. Both species were collected sympatrically around Ishigaki Island, Okinawa, Japan.

Lipid and fatty acid dynamics by maternal Pacific bluefin tuna.

Lipid and fatty acid composition of female Pacific bluefin tuna (PBF, Thunnus orientalis) reproductive and somatic tissues in southwestern North Pacific and Sea of Japan spawning grounds are compared. Total lipid (TL) levels are higher in liver than white muscle tissues. An increased gonadosomatic index (GSI) during the early spawning season coincided with decreased TL. Levels of triacylglycerols (TAG) in PBF liver tissues from the Nansei Islands and Sea of Japan, and white muscle in fishes from the Sea of Japan, decreased during the spawning season, while TAG in ovary tissues did not. Concurrent reductions in TL and increases in GSI early in the spawning season suggest TAG depletion was caused by allocation from liver and white muscle tissues to oocytes, that the liver is one of the important lipid-storage organs in PBF, and this species mostly reliant on capital deposits as a mixed capital-income breeder. Differences of docosahexaenoic acid (DHA) levels between spawning grounds were lower in ovary than in muscle and liver tissues. However, eicosapentaenoic (EPA) and arachidonic acid (ARA) levels that influence egg development and embryo and larval growth are significantly higher in PBF tissues from the Sea of Japan than Nansei Islands, which coincided with larval quality. These suggest a maternal effect exists, with egg quality influencing offspring survival, and that the reproductive strategy of PBF varies according to local variation at each spawning ground.

Evidence of spawning by hermaphroditic skipjack tuna Katsuwonus pelamis.

Hermaphroditic gonads were collected from three skipjack tuna Katsuwonus pelamis in the western and central Pacific Ocean. Both ovarian and testicular tissues were found in the same gonad lobe for each of the three fish. Histological sections of the hermaphroditic gonad from one K. pelamis showed postovulatory follicles, which is evidence of spawning.