Studies on the biology of Benedenia seriolae, an ectoparasitic trematode on the yellowtail : I. on the growth and spawning of the fluke in summer

　ハマチの外部寄生吸虫Benedenia seriolae の生態について，その多数の寄生がみられた小割養殖場のハマチを用いて研究を行ない，これまでに次のような結果を得た. 1) 夏季(水温22°-26℃)においては虫体長は直線的に増加し，寄生初期0.5mm のものが寄生後20 日間で約5.8mm (成熟)に成長した. 2) 休形は成長lこ従って変化し，体幅の体長に対する割合は寄生初期は約40%で細長いが，体長4.8mmに達したものでは約60%となり成虫体形を示した. 3) 産卵は体長5.4mm 以上に達したものに多くみられ，その平均産卵数は5.8mm 前後のものでは170 ， 6.7 mm前後では245 であった. 4) 生育適温の高温限界は約29℃ であると認められた.The author has been carrying out some biological studies on Benedenia seriolae with the aim of finding effective method for controlling the fluke. Observation has been made on this ectoparasite infecting the yellowtail in the fish-culture farms in Shizuoka Prefecture. Following results have sofar been obtained with special emphasis on the growth and spawning of the fluke during the summer. 1) At water temperatures of 22-26°C, the fluke attaching to the skin of host fish appears to grow in body length almost linearly in relation to time, since it was observed that the young fluke which measured about 0.5mm shortly after attachment attained the body length of about 2.8, 4.7 and 5.8 mm respectively in 10, 15 and 20 days. 2) The shape of the fluke gradually changes with growth; for instance, the ratio of body breadth to body length was 0.4 in the young with body length of 0.5 mm, while it was 0.6 in the individuals measuring 4.8mm in body length and resembling the adult in body shape. 3) The spawning of the fluke was observed in the mature individuals 5.1-7.1 mm in body length which were separated from host fish and kept alive in glass vessels for a few days. Average number of the eggs laid by each individual was 170 in the group of smaller flukes (about 5.8 mm) and 245 in the group of larger flukes (about 6.7 mm). It was also inferred that the fluke continues to grow in body size after attainment of maturity and spawns several times. 4) The fluke infecting the skin of host fish is apparently inaffected by water temperatures upto 28°C, but the majority leaves the host to die when exposed to temperatures of 29-30°C for 24 to 41 hours. Therefore, it may be that detachment of the fluke is caused at water temperatures of about 29°C and above

Tigriopus japonicus(ハルパクチコイダ橈脚類)成体の休眠生態について

筆者らは，餌料生物としての利用におけるT. japonicusの培養，ならびに保存に関する基礎的研究を行なっているが，ここでは，後者に関連して行なった本種成体の休眠生態に関する二三の観察結果について報告する。 (1) 25℃で培養したものは4～8℃で，15～20℃で培養したものは-2～2℃でそれぞれ全個体が休眠状態となり1日後に元の水温に戻すとすべてが蘇生した。また，16℃で培養し0℃で休眠した個体をそのまま0℃で保存した場合，1か月後に80%(雌雄ともに)， 2か月後に55%(雌)，20%(雄)の蘇生率を示した。 (2) 飼育海水の濃縮による高塩分条件下では，濃縮速度(但し塩分約150‰へ20～100時間の範囲)と特に関係なく，いずれの場合も塩分130～150‰(水温23～26℃)程で全個体が休眠状態となり，それらを1～7℃に置いた場合，1か月後に60%(雌雄混在)の蘇生率が得られた。 (3) 休眠生起の条件としての塩分と温度の関係については断片的な検討にとどまったが，塩分濃度が高くなるにつれ，いわゆる冷休止帯よりさらに高い水温で休眠状態になることが認められた。 (4) 以上の実験を通じ，概して雌は雄より休眠状態に陥り難い一方，休眠からの蘇生率は若干良好であった。Experiments have been done on the salinities and temperatures causing dormancy in the adults of Tigriopus japonicus. The results are as follows; (1) The animals cultured in sea-water media (salinity, 32.5～34‰) at 25℃ and 20～15℃ wholly lie dormant in 8～4℃ and 2～-2℃, respectively. (2) These dormant animals of both sexes show a revival rate of 80% after being stored at 0℃ for a month. (3) When the sea water containing the animals is gradually concentrated by evaporation at 23～26℃, all the individuals fall into dormancy at salinities of 130～150‰. At these salinities the dormant animals survive for more than one month at 1～7℃. (4) The animals fall into dormancy at higher temperatures as the environmental salinity is higher. (5) Females are slightly more resistant to falling into dormancy than males, either at lower temperatures or at raised salinities.The expenses for this study were partially covered by a research grant from the Ministry of Education

Fundamental studies on techniques of mass-production of fry of the black porgy, Mylio macrocephalus : I. On the spawning induced by injection of a preparation of mammalian gonadotropic hormones

　鹹水養池で粗放的に養殖されたクロダイ雌魚，生殖腺刺激ホルモンとしてシナホリンを注射した. のち，雄魚とともに水槽に収容して，下記のような結果を得た. 1) 産卵期に入る前の未熟期から約1ヶ月聞にわたり， 4回の注射により全量62RUを投与した満4 年魚において良好な産卵結果が得られたほか，満3年魚においても産卵がみられた. 2) 産卵期における未完熟魚に１同(20RU) または2回(40RU) の注射により，満4年魚に産卵 個体が多くみられた.Using the adults of 3 or 4 years of age of black porgy which were cultured extensively in the brackish-water fishponds, some trials were made in the artificial inducement of spawning of the fish. Female fish were mated with males in small concrete tanks after intramuscular injections of saline solution of "Synahorin" (mammalian gonadotropin preparation), and the results obtained were as follows. 1) Development of the ovaries of every semimature female recipient fish was evidently hastened by injections prior to the spawning season or early in that. 2) Then, two out of three females of 4 years of age successfully spawned after 62 RU in total dosage was respectively given by means of injecting in four doses during about one month, while partial spawning occurred in only one out of four females of 3 years with the above and additional injections. 3) In the spawning season, as the results of injections of respective dosage of 20 RU (once) or 40 RU (twice) into many females which were ripening but had not yet spawned, some of them mostly in females of 4 years of age could be induced to spawn

Studies on the Usefulness of the Bluegill Sunfish，Lepomis macrochirus Rafinesque，as an Experimental Standard Animal : II. On the Developmental Stages and Growth from the Egg through One Year

Bluegill sunfishを実験動物として用いるための研究の一部として周年採卵を目的とした研究を行なっているが，その基礎資料として産卵習性に引続いて卵内発生，仔魚の成長及び0年魚の成長等について実験観察を行なった. (1) 卵は直径1.23mm前後の粘着卵で，卵黄には1個の大油球(約0.38mm)と多数の小油球がある. (2) 卵径は個体により，また同一個体でも産卵の度に変異があるが，親魚の年令，大きさ，産卵回数，産卵数等との間には一定の関係は見出されなかった. (3) 水温24.5±1.0℃での孵化期間は平均40時間(37～43時間)，28.5±1.0℃では28時間(27～29時間)，18.5±1.0℃では79時間(75～85時間)であった.18.5℃のものは46%もの奇形率を示した.なお上記の3段階の水温での卵内発生の経過はTable 2に示した. (4) 人工採卵によって得た卵の受精率，孵化率は自然産卵のものに比べてかなり低かった. (5) 孵化仔魚は全長3.23mmで1.13×0.9mm位の卵黄を残し，体のどの部分にも色素胞の出現は見られない. (6) ミジンコ類は最も適した初期餌料で，それによる成長はコペポーダ，輪虫によるものより速かであった.全長13mm位で鰭の棘，軟条の定数が現われ，14-15mmで鱗が出来，縞も認められる. (7) 稚魚の全長瀕度分布曲線の検討によってトビの現象は認められないことが判った. (8) 満1年で体長約5.3cm(3.0-8.3cm)に成長するが，雄は雌に比べて大きい.As part of research-work on the usefulness of the bluegill sunfish, Lepomis macrochirus Rafinesque, as an experimental standard animal in fisheries research, we have tried to find out a way of obtaining its fingerlings throughout the year-curriculum. In sequence to the previous study on the breeding habits, some examinations have been conducted mainly on the developmental stages and the growth from the egg till one year after the hatching, using spawned eggs by full three or four year old fish in rearing tanks. The results so far obtained are as follows: (1) The egg is adhesive and spherical in shape, measuring about 1.23 mm in diameter, with one large oil-globule (ea. 0.38 mm) and many minute ones. (2) The egg diameter varies in the individuals and also in the batches of the same fish. However, no certain relation was found between the egg diameter and the age, the size and the number of times of spawning of the mother fish nor with the number of eggs spawned. (3) The incubation period was about 40 hours (37-43 hours) at a temperature of 24.5°C, 28 hours (27-29 hours) at 28.5°C and 79 hours (75-85 hours) at 18.5°C, respectively. However, abnormal larvae appeared in a fairly high percentage (ea. 46%) at a temperature of 18.5°C, which is considered nearly out of the optimum spawning temperature. (4) A percentage of fertilization and hatching of the eggs taken by the artificial insemination was fairly lower than those of the natural spawning. (5) The newly hatched larva is about 3.23 mm in total length, with a yolk of 1.13×0.9 mm in size and no pigment in any part of the body. (6) Cladocera (Morina sp.) seems to be most adequate food in the early stages of the bluegill larva, those fed with them showed faster growth than those fed by rotifers or copepods. (7) The definite number of the spine and ray of each fin appeared at a total length of 13 mm, after that the lateral striped pattern appeared on the body side with the complete formation of the scale at a size of 14-15 mm in total length. (8) From the examination of the size-frequency of the reared fingerlings, it was recognized that the phenomenon of "shoot individual" does not occur. (9) The first year's growth of the bluegills is about 5.3 cm (3.0-8.3 cm). The average rate of growth of the female is below that of the male

An Ecological Study on the Swarming of the So-called Japanese Palolo in Ashida River

芦田川河口域にはイトメのほか5種類の多毛環虫類が分布しており,筆者らはそれらの生態について研究調査を行なっているが,そのうち,1968,69年にわたりイトメ(生殖型個体はバチまたは日本パロロと云われる)の生殖群泳に関する生態について行なった調査の結果,次のような知見を得た. 1) イトメは,河口(本学箕島実験所前,st15)より約6.6km上流のst.4の辺りを上限とし,河口より約1.9km上流のst.13付近を下限とする約4.7kmの区間にわたって分布する. 2) バチの生殖群泳は毎年旧暦10月および11月の3,4,5日即ち新月大潮の頃の各3日間に出現する. 3) 上記の出現時期には,満潮後30～50分頃から群泳が始まりやがて退潮に乗って流下するが,群泳は約2時間(第3日は1時間余)で終焉する.また,st.7(河口より約5.5km上流)におけるバチの採集量は第1日が最も多く,第2日は大幅に減り第3日は極めて少なかった. 4) 群泳時間の後半は退潮の流れが激しくなり,バチはすべて濡筋に収斂されるのでそこでは急激な増加がみられる反面,川の浅所では群泳個体は殆どみられなくなる. 5) 群泳の初期は雌の割合が著しく少ないが,次第に増加し終期には雄を上廻るようになった.1晩の全採集個体についてみた性比は,ほぼ雌1:雄2であった. 6) バチの大きさは,始めは雌雄とも小形のものが多いが,大形のものが漸次その数を増すようになり,特に終期にはその割合が著しく大きくなる. 7) バチの体色は游出後の時間経過に従って変化し,雌の場合は橙黄色から薄緑色になり,さらに青緑色になると放卵がみられ,雄は淡紅白色から乳白色に変り放精する.この変化は体壁が破れ易くなる変化とともに,群泳出現の第1日から第3日にかけ順次にその多くの個体にみられる現象でもあり,これらからバチの多くは游出後群泳を繰返し3日目に産卵するものと推定される. 8) 孕卵数は個体による変異が大きく,53.5×103～714.5×103を示した.As a part of the ecological studies on benthic animals in the estuary zone of the Ashida River, some researches on polychaete worms, especially on Tylorrhynchus heterochaetus, have been carried out since 1968. In those, we specialized on the swarming of epitocous individuals of the above mentioned species (viz., the so-called Japanese Palolo or "Bachi" in Japanese). The results of these researches can be summarized as follows: (1) Actocous individuals (viz., "home" in Japanese) were found in the area from st. 4 shown in Fig. 1 (about 6.6 km up from the river mouth) to st. 13 (about 1.9 km up from the river mouth), and they were densely distributed from st. 5 to st. 7. (2) The swarming of Japanese Palolo in this district took place in a definite period for three days following the new moon (that is from 3rd to 5th of October and November in the lunar calendar). (3) In each day of that period, the swarming began at the time of 30-50 minutes after high water and disappeared about two hours later when while they were swept downwards. The amount of the swarming individuals collected at st. 7 each day was the highest in the first day decreasing remarkably the next day and was very faint the last day. (4) As the downstream current became too swift in the latter half of the swarming time, the individuals were concentrated to a water-route, their number increased markedly there while they almost disappeared in the other areas. (5) In the early stage of the swarming time, the ratio of female amongst the collected individuals was very low (i.e. 17%) but increased gradually and exceeded one-half at the end. The sex ratio of female to male was about 1:2 for a whole group of individuals collected in one night. (6) In the early stage, individuals of small size were numerous in both sexes but later on large ones appeared more and more, until finally in the latest stage most of them were very large individuals. (7) The body color of the Japanese Palolo changes with the elapse of time in both sexes. Change of coloration of individual occurs from orange yellow to faint green, further to blue green in the females, and from orange white to milky white in the males. The discharge of ova and sperm was observed after the occurrence of such a change of coloration. This change as well as the fragility of body wall are the phenomena commonly observed in the majority of Palolo within three days of the swarming. Then, from the above mentioned facts, it can be presumed that the majority of Palolo in this district spawn in the third night after the repeated swarming in succeeding night. (8) The individual variation in egg number was not small, ranging between 53.5×103～714.5×103

淡水魚に寄生する橈脚類Neoergasilus japonicus (Ergasilidae)に関する研究 : II. コペポデイッド期の発育

前報に引き続き,寄生性橈脚類Neoergasilus japonicasのコペポディッド期の発育形態を記載した。ノープリウスの場合は飼育実験により得られた各期の虫体に基づいて記載したが,飼育実験ではコペポディッドII期までの虫体しか得られなかったため,本報では主として福山市の千塚池におけるネット採集により得られたコペポディッド期標本に基づき記載を行なった。 その結果,本種のコペポディッド期は6期から成ることが明らかとなった。Neoergasilus属の特徴である第1遊泳脚底節における歯状突起の発達は既にコペポディッドI期に認められ,同じく第1遊泳脚外肢第2節の発達した棘(遊泳板)は第III期に認められるようになる。 雌雄の分化は第III期に始まり,この期より雄は顎脚を備えるが,雌では終始顎脚は認められない。そして第VI期に至り,共に成熟し,交尾をする。その後雌は宿主をみつけて寄生し,産卵するが,雄は自由生活に終わるものと思われる

An Ecological Study on the So-called Mogai (Anadara subcrenata (LISCHKE)) cultured in Kasaoka Bay

笠岡湾大島におけるモガイ養殖場の環境条件と養殖モガイの成長,成長に伴う形態の変化等に関する調査並びにモガイの種苗生産を目的として生殖巣の成熟,産卵誘発,受精及び初期発生に及ぼす塩分濃度の影響等について実験,観察を行なって次のような結果を得た. (1) 笠岡湾大島養殖場は,その水質(図2)および底質調査結果(表2,3)からみてモガイ養殖に好適な条件を備えている. (2) 1年間(昭和45年5月～46年5月)のモガイの成長は,殼長についてみると,1年ものでは約0.8cmのものが3.4cm(増長分2.64cm)に達し,2年ものでは約2.7cmのものが4.8cm(増長分2.06cm)に成長した. (3) 養殖場での全採集個体の計測値から得られた殼長と全重量,殼高及び殼幅の関係は,それぞれ図5,6及び7に示した通りである. (4) 笠岡湾で1年養殖したもののうち,九州産種苗のものと大阪産種苗のものの形態について比較したところ,殼長と殼幅の関係における"位置"の差に有意性があり,同殼長の場合九州種は大阪種より殼幅の小さいことが認められたが,それは小型のものに顕著であった. (5) 肥満度(肉重量/全重量)は,その値の低い8～12月の期間と1～7月の高い期間の二段階に大別された.雌雄別にみた肥満度は,年間を通した値では差はなかった(t=0.542<tα0.05=1.96)が,概して産卵期前は雌の方が高く,産卵期の後期およびそれ以後暫くは雄の方が高い値を示した. (6) 笠岡湾養殖場におけるサルボウの生殖巣について,その発達過程を時期的に大別すると,1月から4月までは全体的に生殖細胞増殖期(生長前期,後期)に当り,5月から次第に成熟期に移る.6月から放出期個体の出現が見られ,7,8,9月は放出期に当るとともに,8月から放出後の濾胞期のものが増加し,それらは年末にかけて次第に次の生殖細胞増殖期に移行する. (7) 笠岡湾養殖場における産卵期は6月から12月までの長期間に及ぶが,産卵盛期は7月から9月まである. (8) 上記調査結果における生物学的最小形は雌雄とも殼長約1.5cm,重量約1.0gであり,また,産卵期間における性比は1:1であると認められた. (9) 本種の放卵放精の誘発は,温度,精子懸濁液(放卵のみに対し),NH40Hによる刺激は何れも有効なことが認められたが,NaOH,KNO3の場合は無効であった.これらの反応に対する塩分条件の関係をみたところ,Cl14.08～24.40‰においては特にその影響はみられなかったが,Cl8.16および26.00‰においては誘発反応は阻止される. (10) 殼長3～5cmの大きさのものの産卵数は大体500～1,000万個である.卵の大きさは直径51.38±3.78μである. (11) 未受精卵を各塩分段階中に置いた場合,その受精および発生の能力はCl16.6‰前後の場合に最も長時間(22℃において,約13時間)保有されると認められる. (12) 受精卵の発育に対する塩分条件は,D状ラーバに達するまでの歩留りからみるとCl15‰前後が最も適していると認められる.The so-called "Mogai", Anadara subcrenata (LISCHKE) (a kind of ark shell) is one of the most important bivalves in the Seto Inland Sea, but in recent years the area of its culturing grounds is gradually decreasing due to reclamation works and water pollution through the release of industrial wastes. This study was carried out mainly to clarify the environmental conditions of Mogai culturing grounds in Kasaoka Bay, Okayama Prefecture; the growth of Mogai as well as the maturation of gonad; the artificial inducing of spawning and the effect of chlorinity upon the fertilization and the early development. The results obtained are as follows: (1) Several items on the quality of water and bottom mud are shown in Fig. 2 and Table 2 & 3, signifying the fitness of the ground as to the culturing of this species. (2) The growth of shell length in one year period from May 1970 on was from 0.8 cm to 3.4 cm and from 2.7 cm to 4.8 cm in the one year old and two years old classes respectively. (3) The relations between shell length and total weight, shell height and also shell width which were calculated on the data obtained in 2,300 of cultured individuals are shown in Fig. 5, 6 and 7 respectively. (4) The shell width of Mogai derived from Kyushu was smaller than that from Osaka at the same size, particularly in their young stage. (5) The seasonal variation in fatness can be divided roughly into two periods, namely one from August to December when its evaluation is considerably low, and another from January to July. The difference of the evaluation of fatness between both sexes was not recognized. (6) Microscopic photographs of gonads of both sexes in each stages of development are shown in Fig. 12. (7) The spawning season seemed to happen from June to December. In the examined district, it was especially flourishing from July to September. (8) The biological minimum of this clam was about 1.5 cm in shell length and 1.0 g in weight in both sexes. Sex ratio observed in spawning season was 1:1. (9) The discharge of sexual products of this species was effectively induced by treatments of raising the water temperature, immersion in sperm suspended sea water (only to egg discharge) or suitable concentration of ammoniated sea water, but treatment by NaOH and KOH was not effective. In regard to the influence of chlorinity upon the discharge of sexual elements, no particular effect was observed in the range of Cl 14.08‰ to 24.40‰. However, discharge reactions were obstructed in chlorinity of 8.16‰ and 26.0‰. (10) Mogai of 3-5 cm in shell length discharged about five to ten millions eggs, the average diameter being 51.38±3.78µ. (11) On the treatment of unfertilized eggs in water of different grades of chlorinity, the eggs were safely kept the longest period (13 hours at 22℃) in chlorinity of about 16.6‰. (12) It was recognized that about 15‰ of chlorinity suits best the development of fertilized eggs of this species as can be judged by the survival rate up to the D-shaped larvae

Life Cycle of Alella macrotrachelus (Copepoda) Parasitic on Cultured Black Sea-bream

Recently, industrial farming of black sea-bream, Acanthopagrus schlegeli (Bleeker), has grown prosperous in the Inland Sea of Japan. This species is said to be fairly resistant to environmental water pollution and diseases as compared with yellow tail, Seriola quinqueradiata, a popular species in mariculture of our country. However, some ectoparasites are known to attack cultured black sea-bream. Among them, Alella macrotrachelus (Brian, 1906) (Copepoda: Lerneopodidae) with which we deal here seems to be the most harmful gill parasite. In this paper the development of this parasite is described, based on specimens from laboratory experiments. The female life cycle proved to consist of seven stages; one nauplius stage, one copepodid stage, four chalimus stages (attached by frontal filament), and the adult stage (attached by bulla). The life cycle of the male could not be revealed thoroughly, but it is clear that the male gets into the life of superinfection on the female at its second chalimus stage. Sexual dimorphism becomes distinct in the second chalimus stage

Pseudodiaptomus marinus(橈脚亜綱: カラヌス目)の各発育段階での天然懸濁粒子の摂食

Comparative grazing experiments of various developmental stages and sexes of the inshore marine copepod Pseudodiaptomus marinus on naturally occurring particles were carried out. The feeding behavior was similar between both sexes of the adult, but different between developmental stages. The adult females were capable of consuming almost all particles from 2.8 to 63.3 μm diameter, showing selectivity for larger particles (ca. 50 μm) where the peak of particle concentration occurred. The nauplii consumed mainly smaller particles (<30 μm). The consumption by copepodites was intermediate between that of the nauplii and adult females, since they fed upon both smaller and larger particles. Such intraspecific differences of grazing behavior may lead to the effective utilization of heterogeneous natural food resources. The ingestion rates of the adult females increased linearly with the increase of particle concentrations, without indications of the threshold nor saturation response. The amount of ingested carbon rarely met the requirement for potential egg production which was observed for the wild population. Thus, it was surmised that the adult females could ingest sufficient food deposited on the sea-bottom during a daytime epibenthic phase to attain predicted egg production

クロダイの血漿リポタンパク質に及ぼすアオサ粉末添加飼料の影響

クログイAcanthopagrus schlegeliの脂質代謝の改善に及ぼすアオサUlva pertusa粉末添加飼料の効果を、血漿リポタンパク質の挙動から調べた。1)電気泳動的に9成分のリポタンパク質を認め、これらを硫安塩析でアルブミンとグロブリンに分画した。全リポタンパク質の57%は分子量150,000のアルブミン牲リポタンパク質が占める。他の8成分は分子量70,000以上のグロブリン性であった。2)アオサ粉末の投与により、血漿リポタンパク質に影響がみられ、アルブミン性リポタンパク質の割合が増加した。アルブミン性リポタンパク質の脂質クラス組成はアオサ投与により変化はなかったが、グロブリン姓リポタンパク質の脂質クラスに大きな変化がみられ、Triglyceridesが減少しリン脂質が相対的に増加した。3)無給餌による越冬で両区のアルブミン性リポタンパク質が電気泳動的に変化したが、越冬後の泳動像は両区で差異は認められなかった。4)アオサの投与により生じた脂質代謝の改善は、血漿リポタンパク質の挙動にも影響を与えることを観察した。Effect of Ulva pertusa meal supplement to diet on improvement in lipid metabolism was determined in regard with plasma lipoprotein in black sea bream Acanthopagrus schlegeli, 1) At least 9 lipoproteins were electrophoretically detected. These lipoproteins were classified into albumin and globulin by salting-out. A lipoprotein classified as albumin having 150,000 in molecular weight was accounted for 57% in the total lipoproteins of control group. The Ulvu meal increased its proportion (67.6%). 2) Molecular weight of lipoproteins in globulin fraction was more than 700,000. While lipid class composition of albumin fraction did not changed, that of globulin fraction was highly variable under the influence of the dietary Ulva meal. 3) Wintering without feeding caused great changes in electrophoretic behavior of lipoprotein. However, no differences were found in lipoprotein composition between both groups after wintering. 4 The improvement of lipid metabolism by the Ulvu meal reflected on the plasma lipoprotein