Overlaps in habitat use of fishes between a seagrass bed and adjacent coral and sand areas at Amitori Bay, Iriomote Island, Japan: Importance of the seagrass bed as juvenile habitat

ABSTRACT:   To clarify faunal overlap between a seagrass bed and adjacent coral and sand areas, and the number of reef fishes utilizing the seagrass bed as juvenile habitat, visual censuses were conducted at Amitori Bay, Iriomote Island, Japan. The numbers of species and individuals of fishes were significantly higher in the coral area than in the seagrass bed and sand area. Cluster and ordination analyses based on the number of individuals of each species demonstrated that the fish assemblage structure differed among the three habitats in each season, but with some overlaps. Approximately half the seagrass bed fishes occurred in the adjacent coral area (coral–seagrass species). Dominant species of coral–seagrass species utilized the seagrass bed as an important juvenile habitat. Thus, some overlaps in habitat use were present between the seagrass bed and adjacent coral area. Despite such overlaps, however, coral–seagrass species accounted for only approximately 15% of coral reef fishes overall, indicating that most of the latter hardly utilize the seagrass bed directly in the study area.     

Improved rapid and efficient method for Staphylococcus aureus DNA extraction from milk for identification of mastitis pathogens

A rapid and efficient DNA extraction method was developed for detecting mastitis pathogens in milk. The first critical step involved cell wall disruption by bead-beating, as physical disruption using beads was more effective for DNA extraction from Gram-positive bacteria, such as Staphylococcus aureus, than enzymatic disruption using proteinase K. The second critical step involves the use of acetic acid and ammonium sulfate in the purification process, as these reagents effectively and efficiently remove the lipids and proteins in milk. Using these methods, DNA suitable for loop-mediated isothermal amplification was obtained within 30 min. Also, the rapid and sensitive detection of S. aureus in milk was possible at levels as low as 200 cfu/ml.     

Production of Functional Gametes from Cryopreserved Primordial Germ Cells of the Japanese Quail

The Japanese quail (Coturnix japonica) is a valuable bird as both an experimental animal, for a wide range of scientific disciplines, and an agricultural animal, for the production of eggs and meat. Cryopreservation of PGCs would be a feasible strategy for the conservation of both male and female fertility cells in Japanese quail. However, the effects of freeze-thaw treatment on viability, migration ability and germline transmission ability of quail PGCs still remain unclear. In the present study, male and female PGCs were isolated from the blood of 2-day-old embryos, which were cooled by slow freezing and then cryopreserved at –196 C for 77–185 days, respectively. The average recovery rate of PGCs after freeze-thawing was 47.0%. The viability of PGCs in the frozen group was significantly lower than that of the control group (P<0.05) (85.5% vs. 95.1%). Both fresh and Frozen-thawed PGCs that were intravascularly transplanted into recipient embryos migrated toward and were incorporated into recipient gonads, although the number of PGCs settled in the gonads was 48.5% lower in the frozen group than in the unfrozen control group (P<0.05). Genetic cross analysis revealed that one female and two male recipients produced live progeny derived from the frozen-thawed PGCs. The frequency of donor-derived offspring was slightly lower than that of unfrozen controls, but the difference was not significant (4.0 vs. 14.0%). These results revealed that freeze-thaw treatment causes a decrease in viability, migration ability and germline transmission ability of PGCs in quail.     

Functional role of type VI collagen during early feather development of the chicken embryo in vitro

The regulatory function of type VI collagen during early feather development in embryonic chickens was investigated at the cellular and organ levels. Immunohistochemical studies of embryonic chicken skin showed that type VI collagen was distributed in spatial‐specific and temporal‐specific manners related to early feather development. To clarify the role of type VI collagen, we studied the feather development in intact, reconstituted and reconstituted gel skin cultures. When ethyl‐3,4‐dihydroxybenzoate (EDHB) was added to the medium of intact skin as an inhibitor of type VI collagen synthesis, the feather buds did not elongate and the number of neural cell adhesion molecule (NCAM)‐positive cells was reduced. However, the magnitudes of both suppressive effects of EDHB were reduced by the addition of liquid type VI collagen. Similar improvement was also observed in the reconstituted skin with liquid type VI collagen and in the reconstituted gel skin with solid type VI collagen at a low concentration. Moreover, type VI collagen promoted feather bud development in the absence of EDHB. However, a high concentration of solid type VI collagen in the reconstituted gel skin arrested the feather bud elongation, and antitype VI collagen antibodies caused feather buds to become longer and smaller in the reconstituted skin. At the cellular level, type VI collagen affected the proliferation, migration and NCAM expression of mesenchymal cells. These results suggest that type VI collagen regulates early feather development by controlling mesenchymal cell behavior.     

A study of delayed capture mortality syndrome in skipjack tuna, Katsuwonus pelamis (1).

Abstract. This study was initiated to determine the cause(s) of delayed mortality in newly captured skipjack tuna, Katsuwonus pelamis (L.), being held at the National Marine Fisheries Service Kewalo Research Facility. Sixty-four per cent of 244 skipjack tuna delivered to the facility died, usually on the second or third day after capture. The capture history, morphological data, serum chemistry (21 standard parameters), haematology, and histological samples of major organs, were obtained from 30 fish sampled at sea immediately after capture, or after approximately 4, 9, 24, 48 or 500+ h in captivity. The cause(s) of death in these fish could not be attributed to anoxia, disseminated intravascular coagulation, lactic acidosis, capture myopathy or infection. Post-capture haemodilution is hypothesized as a major factor of delayed capture mortality syndrome in skipjack tuna.     

The enhancement of Th1 immune response by anti-PD-L1 antibody in cattle infected with Mycobacterium avium subsp. paratuberculosis

Johne’s disease, caused by Mycobacterium avium subsp. paratuberculosis (MAP), is a chronic enteritis of ruminants. Previous studies have shown that programmed death-ligand 1 (PD-L1) is associated with the disease progression, and PD-L1 blockade activates MAP-specific Th1 responses in vitro. Here, we performed anti-PD-L1 antibody administration using 2 MAP-infected cattle at the late subclinical stage of infection. After administration, bacterial shedding was reduced or maintained at a low level. Additionally, MAP-specific Th1 cytokine production was upregulated, and CD69 expression was increased in T cells. Collectively, the treatment has a potential as a novel control method against Johne’s disease.