Expression of a recombinant crustacean hyperglycemic hormone of the kuruma prawn Penaeus japonicus in methylotrophic yeast Pichia pastoris

ABSTRACT:   Until now, six crustacean hyperglycemic hormones (CHH) designated Pej-SGP-I, -II, -III, -V, -VI and -VII have been characterized in the kuruma prawn Penaeus japonicus . All CHH consist of 72 amino acid residues and have an amidated carboxyl (C)-terminus. In the present study, we expressed Pej-SGP-III in methylotrophic yeast Pichia pastoris in order to obtain a large quantity of recombinant CHH possessing biological activity. A cDNA encoding Pej-SGP-III that had been previously cloned was processed by polymerase chain reaction (PCR) and the resulting product was ligated into an expression vector. Pichia pastoris was transformed with this vector after which a recombinant Pej-SGP-III was expressed having an additional amino acid residue (glycine) at the C-terminus (rPej-SGP-III-Gly), a form considered to be a putative precursor of this hormone. rPej-SGP-III-Gly secreted into the culture medium was purified by reversed-phase HPLC, and amidated using a peptidylglycine alpha-amidating enzyme. The amidated rPej-SGP-III (rPej-SGP-III) showed hyperglycemic activity in in vivo bioassay almost comparable to that of the natural Pej-SGP-III. rPej-SGP-III thus obtained will be a useful tool not only for its physiological study but also for the determination of its 3-D structure.     

Evidence of a local spawning site of marine eels along northeastern Japan, based on the distribution of small leptocephali

Evidence of recent spawning by several species of marine eels of the families Congridae, Ophichthidae, and Nettastomatidae was found over the continental shelf along the coast of northeastern Japan in October 2003. Sixty‐three leptocephali of at least three taxa that ranged from 3.8 to 12.3 mm total length were collected in a relatively small area, just to the south of Cape Shioya, primarily over the 100‐and 200‐m‐depth contours. The leptocephali of Gnathophis nystromi nystromi were the most abundant, followed by those of G. nystromi ginanago. This spawning area is located in an area that appeared to include water originating from the Tsugaru Warm Current and is further south than the typical latitude of the cold water of the Oyashio First Intrusion. These findings suggest that some species of marine eels may not migrate past the slope to spawn, and that the oceanographic features of the region may provide favorable conditions for the growth and retention of leptocephali in the area to the south of Cape Shioya.     

Development and comparative test of squid liver artificial bait for tuna longline

ABSTRACT:   We have been developing an artificial bait for longline tuna fishing using the liver of the Japanese common squid Todarodes pacificus , a waste product of the squid fisheries industry, as the primary component. Three control test operations using the artificial bait and natural squid were conducted during January 1998, 1999 and 2000. During these operations, we compared the angling performance of the artificial bait with that of the natural squid. Some tuna was caught using the artificial bait; however, the hooking ratio for the artificial bait was less than that for the natural baits. Despite this, there was no significant difference between the hooking ratio by artificial bait and natural squid. In addition, species selectivity in the by-catch, a characteristic particular to this artificial bait, was observed. In the present paper, we discuss the hooking ratio and the reduction in by-catch of the artificial bait compared with natural bait.     

Onset and development of aggressive behavior in the early life stage of Japanese flounder

Onset and development, and diel rhythm of aggressive behavior were observed in the early life stages of Japanese flounder Paralichthys olivaceus . The frequency of nip was counted as an index of aggressive behavior. No aggressive behavior was observed during the larval stage until day 39 after hatching (when fish were 13.2 mm in standard length (SL)) in the experimental tanks. The onset of aggressive behavior was observed on day 39, coinciding with completion of metamorphosis from the larval to the juvenile stage, and it developed until day 46. During the metamorphosing stage, typical shivering behavior (Ohm (Ω)-posture) was observed, and it showed a peak on day 19 (SL 7.6 mm) and decreased thereafter. Ω-Posture disappeared in the juvenile stage. Aggressive behavior and Ω-posture were only observed in the daytime. Settlement was first observed from day 19 in less than 30% of larvae and all individuals settled from day 39. As Ω-posture was observed regardless of the presence or absence of food and the peak of frequency in Ω-posture was observed in a specific stage of metamorphosis, this behavior is not related to feeding behavior, and it is possibly a precursor to aggressive behavior in this species.