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図書 |
図書
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鮫島翔太[著]
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論文（リポジトリ） |
論文（リポジトリ）
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Naruse, Tohru ; Maenosono, Tadafumi ; Uyeno, Daisuke ; Samejima, Shota ; Shirawakawa, Naoki ; 成瀬, 貫 ; 前之園, 唯史 ; 上野, 大輔 ; 鮫島, 翔太 ; 白川, 直樹
概要:
Six species of leucosioid crabs are reported from the Ryukyu Islands in this paper: Arcania sagamiensis Sakai, 1969, Eba
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lia stellaris Naruse & Ng, 2006, Ebaliopsis erosa (A. Milne- Edwards, 1873), Myra eudactylus (Bell, 1855), Urnalana elata (A. Milne-Edwards, 1874) (Leucosiidae); and Iphiculus spongiosus Adams & White, 1849 (Iphiculidae). Ebaliopsis erosa are recorded from Japanese waters for the first time; all but Ebalia stellaris and M. eudactylus are recorded from the Ryukyu Islands based on the specimens for the first time. Taxonomic notes are also provided for some selected species.
琉球列島より得られたコブシガニ上科6種 (サガミトゲコブシArcania sagamiensis, ホシズナエバリアEbalia stellaris, Ebaliopsis erosa, ノコバテナガコブシMyra eudactylus, サガミコブシUrnalana elata, ノコハコブシIphiculus spongiosus) の標本を記録した. それらのうち, Ebaliopsis erosaは日本より初めて, サガミトゲコブシ•サガミコブシ•ノコハコブシは琉球列島より初めて, それぞれ標本を基に報告された. また, Ebaliopsis erosaには新標準和名クルミコブシを与え, 和名の基準とする標本にRUMF-ZC-4279を指定した. さらに, 各種の近似種との識別形質や潜在的な分類学的問題点について概説した. 論文 続きを見る |
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図書 |
図書
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鮫島翔太著
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学位論文（リポジトリ） |
学位
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鮫島, 翔太 ; Samejima, Shota
概要:
ヒメジ科魚類は，世界中の温暖な海に生息しており，現在6属80種以上が報告されている．沖縄島周辺海域には，3属約20種が分布しており，電灯潜り漁，刺網漁，定置網漁等で漁獲され，重要な水産資源として利用されている．しかし，沖縄島周辺海域において
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，本科魚類の資源管理に重要な寿命や成熟サイズ等の生物学的基礎情報は欠落している．また，本科魚類は，下顎に一対の鬚を持つことが形態的特徴として挙げられる．この鬚には，味蕾に類似した感覚器が並んでおり，鬚を利用して餌生物を採餌することが知られている．しかし，鬚を使った特異な採餌生態を持つにも関らず，食性や採餌行動と鬚の形態の関係性については，ほとんど研究されていない．そこで本研究は，沖縄島で一般的な6種（ホウライヒメジ，コバンヒメジ，オジサン，アカヒメジ，モンツキアカヒメジ，ヨメヒメジ）の年齢，成長および繁殖特性の解明を試みた．さらに，ヒメジ科魚類15種の食性解析，12種の採餌行動の観察を行い，これらの採餌生態と鬚の形態との関係性について検討した．また，これらの採餌生態が，ヒメジ科と他魚種の種間関係構築にどのように作用しているかを検証した． 耳石を用いて年齢査定を行った結果，いずれの種も最高齢が6歳前後であり，他海域におけるヒメジ科魚類の報告と類似した．一方，最大体長には，種ごとに大きな差がみられ，本科魚類は，成長速度に大きな違いがあると考えられた．また，同年齢階級で比較すると，ウミヒゴイ属は雄が雌より大きいのに対し，アカヒメジ属とヒメジ属は雌が雄より大きかった．ウミヒゴイ属は，ペア産卵を行う種が多いことが知られており，繁殖に雄の体長が大きいことが有利に働く可能性がある．一方，アカヒメジ属の成熟した精巣は他の属に比べ大きいことから，アカヒメジ属はランダム配偶である可能性が高い．このような繁殖生態の違いが属ごとの成長パタンに影響していると考えられた． 食性解析と採餌行動の観察を行った結果，本科魚類は属に関係なく，種ごとに様々な食性，採餌行動を示した．さらに，日中に摂餌を行う種と夜間に摂餌を行う種がいることが示唆された．鬚の形態が類似した種同士では，食性と採餌行動および採餌基質の嗜好性が類似する傾向にあった．例えば，鬚が太い種は，胃から砂と共に多毛類や甲殻類が主な餌生物として出現した．さらに，これらの種は，砂地の中に吻を押し込み採餌していた．鬚が細い種は，砂地の表層や，ガラモ，サンゴ等の複雑な構造をした基質に対して採餌がみられ，甲殻類や魚類を捕食していた．つまり，鬚の形態は，採餌行動と採餌基質に影響し，それらが食性に反映されると考えられた．種ごとに食性，採餌基質，摂餌時間が異なったことから，餌資源の重複や競争を避けるために，“棲み分け”，“食い分け”，“時間分け”が行われている可能性が示唆された．ヒメジ科の採餌行動観察を進める中で，同種で群れを形成する種と他種と行動する種に分類できた．鬚が太く，砂中を採餌する種は，フエフキダイ科などと行動する傾向が強いことから，採餌生態が種間関係構築に影響を及ぼしていることが示唆された．一方，それ以外の種は，集団での狩りや，夜間に分散して採餌することで，同種間の餌の競合を少なくしていると考えられた． 食性，採餌行動および採餌基質は，形態に影響を受けるにも関らず，それらは属内で多様であったのに対し，成長の雌雄差と繁殖生態は，属内で類似した特徴を示すと考えられた．既存の分子系統解析結果に当てはめると，本科魚類の採餌生態は，種が分化した後に多様化した形質であることが示唆された．
Goatfishes (Mullidae) are widely distributed in warm marine water throughout the world and are a commercially important fish family. This fish family is comprised of more than 80 different species in 6 genera. About 20 mullid species can be found in Okinawa Island, Japan, where all species are exploited as a food resource. Fishes are captured by night spear-fishing, set net and gillnet. Despite their importance as a marine living resource, life-history traits of goatfishes have not been studied yet in detail in Okinawa Island. One of the morphological characteristics of goatfishes are their paired chin barbels containing taste buds. It is known that goatfishes are using those barbels for detecting hidden prey organisms. Thus, variation in the morphology of barbels among species might be associated with differences in their diet. However, few studies have so far been conducted on a possible relationship between species-specific diet and the morphology of barbels. In order to understand the feeding ecology of goatfishes, stomach contents of totally 15 species and foraging behavior of totally 12 species were investigated. Furthermore, basic biological information such as age, growth and reproductive biology of 6 common species of 3 genera (Parupeneus ciliates, P. indicus, P. multifasciatus, Mulloidichthys vanicolensis, M. flavolineatus, Upeneus tragula) were examined. To estimate age and growth of mullid species, sagittal otoliths were transversionally sectioned. Distinct opaque bands were assumed to represent growth rings and therefore counted. To validate the periodicity of growth ring formation, monthly changes in occurrence of opaque bands on the edge of each otolith were determined. Opaque rings appeared annually and were most frequent either during the spawning season or before it. Standard length and age data were fitted to the von Bertalanffy growth equation. The result of present study showed that the maximum age for all the species was ca. 6~8 years. This was similar to maximum ages observed from other fish studies in marine waters. However, high variation in maximum length between species was observed indicating that the growth rate differed interspecifically. In Parupeneus, males usually grew larger than females in the same age class, but males of two Mulloidichthys species and males of U. tragula were smaller than the females of the same age class. It is known that species in the genus Parupeneus perform pair spawning. Our findings suggest that the observed size differences between males and females might be related to the genus-specific spawning mode. Spawning season and maturation size were estimated according to histological observation of gonads. Main spawning season of 6 species was estimated to be in spring or summer. In the genus Parupeneus, 50% of mature females and males had similar size or the males were larger than thefemales. Contrary, maturation size of females in the genus Mulloidichthys and in U. tragula was larger than the maturation size of males. Histological observation of ovaries and frequency distribution of oocyte diameter indicated that two Mulloidichthys species had group-synchronous oocyte development, but species from the genera Parupeneu and Upeneus showed asynchronous oocyte development. In addition, estimated female fecundity in the genus Mulloidichthys was greater than in the other genera Parupeneus and Upeneus. These results indicate that reproductive biology is similar among the species of same genus, but differed among genera. An examination of totally 1,110 stomachs and totally 21 hours of foraging behavior observation were conducted. Regardless of the genus, a variety of feeding habits, foraging behavior and preferences of substrate were observed. In addition, some species were found to feed mainly at nighttime. Generally, species with similar barbell morphology exhibited similar feeding habits. For example, species with thick barbels were predominantly feeding on polychaetes or crustaceans and their stomachs usually contained high amount of sand, which was associated to their feeding behavior (plunging of the snout into the sediment while feeding). Species with short and thin barbels were observed to forage on sandy bottom, inside or on the surface of macroalgae stands and their diet was mainly comprised of crustaceans. On the other hand, P. cyclostomus was the species found to be piscivorous searching its prey in structurally more complex habitats such as coral colonies or rocky crevices. In summary, the morphology of barbels was strongly related with foraging behavior, associated substrate of feeding, which in turn reflected the feeding characteristics of each goatfish. The observed differences in feeding ecology might be the result of an interspecific diet competition, i.e. to avoid diet overlap among species. In the course of observing the foraging behavior of Mullidae, we were able to classify them into two groups: species that form groups with the same species and species that behave with other species. Species with thick barbels that forage in the sand tend to swim in small groups with Lethrinidae and Labridae. On the other hand, other species tended to cluster with their conspecifics, but they were thought to reduce competition for food among conspecifics by hunting in groups and foraging dispersedly at night. 続きを見る |
