Influence of connectivity, habitat quality and invasive species on egg and larval distributions and local abundance of crucian carp in Japanese agricultural landscapes

The quality of habitat at and around a spawning site, and the availability of movement between spawning and nonspawning habitats are likely to be important determinants for population persistence in a degraded and fragmented landscape. We assessed the influence of habitat connectivity, habitat quality and invasive species for distributions and local abundance of eggs and larvae of crucian carp (Crassius auratus complex, which is listed as “data deficient” on the Japanese Red List) in agricultural landscapes surrounding Lake Mikata, Japan, where drainage ditches and paddy fields are extensively utilised for spawning (lake or river shores are also used). We investigated the presence and abundance of eggs and larvae of crucian carp and habitat components at 146 sites across a range of presumed spawning habitats. Egg presence was affected strongly by connectivity to the lake (watercourse distance from the lake), and egg abundance was significantly influenced by both connectivity and habitat quality. In contrast, larval presence was primarily related to habitat quality. Larval abundance was influenced by connectivity and habitat quality, but the effect of connectivity was relatively low. Furthermore, larval abundance was negatively related to the presence of the invasive species red swamp crayfish (Procambarus craki) and bullfrog (Rana catesbeiana). Our findings indicate that connectivity, habitat quality and the presences of invasive species are crucial in determining suitable spawning and nursery habitats, but their relative importance may vary depending on egg and larval life stages. We suggest that restoring connectivity, improving habitat quality and removal of invasive species could be effective conservation strategies for the declining populations of crucian carp in agricultural landscapes.     

Food habits of small fishes in seagrass habitats in Trang,southern Thailand

To clarify the feeding habits of seagrass fishes, we examined the gut contents from 42 fish species collected in seagrass habitats in Trang. Thirteen species showed ontogenetic and/or seasonal changes in food-use patterns. Smaller individuals generally preyed on small planktonic items (e.g., copepod larvae) or small benthic/epiphytic crustaceans (e.g., harpacticoid copepods), with subsequent changes to other prey items (e.g., shrimps, crabs, detritus and filamentous algae) with growth. The most important dietary items for the seagrass fish assemblages comprised benthic/epiphytic crustaceans, detritus, and planktonic copepods. Cluster analysis based on dietary overlaps showed that the seagrass fishes comprised eight feeding guilds (large benthic/epiphytic crustacean, detritus, planktonic animal, small benthic/epiphytic crustacean, mollusc, invertebrate egg, polychaete, and fish feeders). Of these, the first three guilds were the most abundantly represented, whereas the last three were each represented by only a single species.     

Habitat shift of ayu Plecoglossus altivelis altivelis in early stages from waters adjacent to the bank to the center of flow in the Shimanto Estuary

ABSTRACT: To clarify the habitats of the ayu in the early stages of development in the Shimanto Estuary, the size and hatching date of the larval and juvenile ayu were examined. Sizes of larvae and juveniles were larger in the center of the flow area than in the waters adjacent to the estuary's banks, which suggests that larvae shift habitat to the center of flow from the waters along the estuary's banks. This shift began at approximately 20 mm body length. However, the resident term in the waters adjacent to the estuary's banks changed with the hatching dates; that is, the early and late-hatched larvae became short and long-term residents, respectively. A similar phenomenon was found also in the juveniles collected in the freshwater section that were migrating upstream. The growth rates of larval ayu in the waters adjacent to the banks tended to decrease with hatching dates. The fluctuations in growth rate with hatching date appear to be a factor leading to the variation of resident term.     

Proliferating effect of extracts from woods and fungi on rat vibrissa dermal papilla cells

Hair growth is a highly regulated cyclical process. Three distinct phases have been defined for the mammalian cycle: anagen (growing phase), catagen (regression phase), and telogen (resting phase). Although little is known about the mechanism that regulates the hair cycle, it is believed that dermal papillae (DP) derived from mesenchymal cells play an essential role in controlling the established hair follicle and hair cycle. The purpose of this investigation was to find the components of woods and fungi that exert a proliferative activity on DP cells. Results show that the fungus YL161 (ethyl acetate extract, 1ppm),Agaricus blazei (ethyl acetate extract, 0.1 ppm), and the bark ofCamptotheca cuminata (methanol extract of bark, 0.1 ppm) exhibit higher growth-promoting activity than pentadecanoic acid. These components that have a proliferative effect on DP cells may be useful hair growth-stimulating materials and can be used to understand the mechanism of hair growth.     

Detection and identification of Flavobacterium psychrophilum from gill washings and benthic diatoms by PCR-based sequencing analysis

A nested polymerase chain reaction (PCR) amplification technique was used to detect Flavobacterium psychrophilum from washings of fish gill surfaces and benthic diatoms as environmental samples. Gill washing samples were prepared from kawamutsu, Zacco temminckii (Temminck & Schlegel) and oikawa, Z. platypus (Temminck & Schlegel). Benthic diatom samples were collected from stone surfaces. All samples were collected from rivers in Wakayama Prefecture, Japan from November 2003 to January 2004. Following simple DNA extraction using a chelating resin, nested PCR techniques targeting 16S-rDNA and gyrB regions were performed, and PCR products were cloned and sequenced. With nested PCR amplification for the 16S-rDNA gene, ambiguous PCR products were detected from two of six samples, and by cloning and sequencing analysis were found not to be DNA fragments amplified from F. psychrophilum. Using nested PCR for the gyrB gene, however, five of six samples were clearly positive for F. psychrophilum in agarose gel electrophoresis, and were found to be identical with nucleotide sequences of F. psychrophilumgyrB deposited in DNA databases by sequencing analysis. Results indicate that nested PCR for the gyrB region is a useful technique to detect low levels of F. psychrophilum from environmental samples contaminated with many other organisms.