通気量と塩分勾配がオニオコゼ仔稚魚の生残と成長に与える影響

We examined the effects of a flow field in the rearing tank exhibited by different aeration rate and salinity gradient on the larviculture of the devil stinger Inimicus japonicus. Two different rearing experiments using 1 kl rearing tanks were conducted from hatching (day 0) to settlement. In the Experiment 1, fish were reared until day 21 in 5 different aeration rates (0-1200 ml/min). There was a significant and positive relationship between survival andaeration rate, and fish survival became stable at an aeration rate of more than 300 ml/min. In Experiment 2, the salinity gradient in a rearing tank was formed by pumping brackish water (22 ppt) from the surface and seawater (34 ppt) from the bottom at the same time. Control rearing tanks (34 ppt) were aerated at 300 ml/min and fish were reared until day 23. Growth and development was synchronized in the salinity gradient tanks with little standard deviation, although average survival at settlement in the salinity gradient tank (47.3 %) was lower than the aeration tank (68.2 %). The optimal aeration rate for devil stinger larviculture is stronger than 300 ml/min and introducing a salinity gradient can be a novel approach for enhancing performance of the fish.異なる通気量と塩分勾配がオニオコゼ仔魚飼育に与える影響を調べた。容量1klの円形水槽で2つの飼育実験を孵化仔魚（0日齢）より着底まで実施した。実験1では5つの異なる通気量（0-1200 ml/min）で21日齢までの飼育を行った。その結果，最終日の生残と通気量の間に有意な正の相関が検出され，300ml/min以上の通気量で生残が安定した。実験2では飼育水槽に水面から22pptの汽水，底面から34pptの海水をそれぞれ連続注入することで塩分勾配を形成させ，対照に34ppt海水に300ml/minの通気を施す水槽を設け，23日齢まで飼育した。その結果，塩分勾配水槽で飼育した魚の成長と着底が同調したが，飼育終了時の生残（47.3 %）は対照のそれ（68.2 %）より低い傾向があった。1kl規模でのオニオコゼの仔魚飼育には300ml/min以上の強い通気による水流が必要であることが明らかになり，さらに塩分勾配の飼育水槽への導入により種苗生産に新たな可能性を見いだした

通気量と塩分勾配がオニオコゼ仔稚魚の生残と成長に与える影響

We examined the effects of a flow field in the rearing tank exhibited by different aeration rate and salinity gradient on the larviculture of the devil stinger Inimicus japonicus. Two different rearing experiments using 1 kl rearing tanks were conducted from hatching (day 0) to settlement. In the Experiment 1, fish were reared until day 21 in 5 different aeration rates (0-1200 ml/min). There was a significant and positive relationship between survival and aeration rate, and fish survival became stable at an aeration rate of more than 300 ml/min. In Experiment 2, the salinity gradient in a rearing tank was formed by pumping brackish water (22 ppt) from the surface and seawater (34 ppt) from the bottom at the same time. Control rearing tanks (34 ppt) were aerated at 300 ml/min and fish were reared until day 23. Growth and development was synchronized in the salinity gradient tanks with little standard deviation, although average survival at settlement in the salinity gradient tank (47.3 %) was lower than the aeration tank (68.2 %). The optimal aeration rate for devil stinger larviculture is stronger than 300 ml/min and introducing a salinity gradient can be a novel approach for enhancing performance of the fish.異なる通気量と塩分勾配がオニオコゼ仔魚飼育に与える影響を調べた。容量1klの円形水槽で2つの飼育実験を孵化仔魚（0日齢）より着底まで実施した。実験1では5つの異なる通気量（0-1200 ml/min）で21日齢までの飼育を行った。その結果，最終日の生残と通気量の間に有意な正の相関が検出され，300ml/min以上の通気量で生残が安定した。実験2では飼育水槽に水面から22pptの汽水，底面から34pptの海水をそれぞれ連続注入することで塩分勾配を形成させ，対照に34ppt海水に300ml/minの通気を施す水槽を設け，23日齢まで飼育した。その結果，塩分勾配水槽で飼育した魚の成長と着底が同調したが，飼育終了時の生残（47.3 %）は対照のそれ（68.2 %）より低い傾向があった。1kl規模でのオニオコゼの仔魚飼育には300ml/min以上の強い通気による水流が必要であることが明らかになり，さらに塩分勾配の飼育水槽への導入により種苗生産に新たな可能性を見いだした

Data from: The genetic architecture of growth rate in juvenile Takifugu species.

Closely related species have often evolved dramatic differences in body size. Takifugu rubripes (fugu) is a large marine pufferfish whose genome has been sequenced, whereas T. niphobles is the smallest species among Takifugu. We show that, unsurprisingly, the juvenile growth rate of T. rubripes is higher than that of T. niphobles in a laboratory setting. We produced F2 progenies of their F1 hybrids and found one quantitative trait locus (QTL) significantly associated with variation in juvenile body size. This QTL region (3.5 Mb) contains no known genes directly related to growth phenotype (such as IGFs) except Fgf21, which inhibits growth hormone signaling in mouse. The QTL in Takifugu spp. is distinct from the region previously known to control body size variations in stickleback or tilapia. Our results suggest that in the fish tested herein, genomic regions underlying body size evolution might have different genetic origins. They also suggest that many diverse traits in Takifugu spp. are amenable to genetic mapping

A Genetic Linkage Map for the Tiger Pufferfish, Takifugu rubripes

The compact genome of the tiger pufferfish, Takifugu rubripes (fugu), has been sequenced to the “draft” level and annotated to identify all the genes. However, the assembly of the draft genome sequence is highly fragmented due to the lack of a genetic or a physical map. To determine the long-range linkage relationship of the sequences, we have constructed the first genetic linkage map for fugu. The maps for the male and female spanning 697.1 and 1213.5 cM, respectively, were arranged into 22 linkage groups by markers heterozygous in both parents. The resulting map consists of 200 microsatellite loci physically linked to genome sequences spanning ∼39 Mb in total. Comparisons of the genome maps of fugu, other teleosts, and mammals suggest that syntenic relationship is more conserved in the teleost lineage than in the mammalian lineage. Map comparisons also show a pufferfish lineage-specific rearrangement of the genome resulting in colocalization of two Hox gene clusters in one linkage group. This map provides a foundation for development of a complete physical map, a basis for comparison of long-range linkage of genes with other vertebrates, and a resource for mapping loci responsible for phenotypic differences among Takifugu species

Reproductive biology of spotted halibut, Verasper variegutus, in Tachibana Bay, Nagasaki Prefecture

The reproductive biology of female spotted halibut, Verasper variegutus, was examined from 19 specimens sampled in Tachibana Bay, Nagasaki Prefecture during 27 December 1997 to 30 January 1998. The maturity stages of the ovaries were categorized into three classes based on the histological characteristics and the size-frequency distribution of oocytcs; pre-spawning, spawning and post-spawning. The occurrence rates of the different maturity stages of ovaries during the collection period suggested that the spawning season of spotted halibut in Tachibana Bay extends from late December to early February. Developing oocyte in the course of vitellogenesis formed a single clutch separated from the pre-vitellogenic oocyte group, which resulted in showing two peaks isolated each other in the size-frequency distribution of oocytes. After the completion of vitellognesis in all oocytcs of the advanced clutch, final oocyte maturation and following ovulalion occurred in a part of oocytes of the clutch. The number of oocytes of the advanced clutch gradually decreased during the spawning season due to serially occurring ovulalion. The ovaries after spawning contained only pre-vitellogenic oocytes scattered among the degenerating postovulatory follicles. Total fecundity (TF) in five fish with the ovaries at the prc-spawning stage was related to total length (TL, mm) as TF=7.45・10-6TL4.08 (341≦TL≦488).長崎県橘湾で1997年12月～1998年1月に漁獲されたホシガレイの雌親魚19尾を用いて, 卵の発達動態を中心とした成熟生態について調査した. 組織学的特徴および卵径頻度分布こ基づき, 卵巣の成熟段階を産卵直前期, 産卵期および産卵終了期の3期に区分した. これらの卵巣の出現状況から, 橘湾における本種の産卵期は, 12月下旬から2月上旬であると推定された. 本種の卵の発達様式は, 周辺仁期の卵から一部の卵群が発達する卵群同期発達型に属し, 産卵様式は複数回に分けて成熟・排卵される分割産卵型であると考えられた. また, 総産卵数（TF）と全長（TL in mm) との関係は, TF=7.45・10-6TL408（341≦TL≦488）の式で表され, 平均全長427mmの個体における総産卵数ほ約45万粒であった