Search

Hypermastus tokunagai is a eulimid gastropod infecting the sand dollar Scaphechinus mirabilis. The eulimid is easily detached from the host and thus regarded as a temporary parasite. In this study, the growth and reproductive cycle of H. tokunagai were investigated using specimens collected from S. mirabilis in the western Seto Inland Sea, Japan. Newly recruited individuals of H. tokunagai appeared in early autumn and grew rapidly, while growth was retarded from mid-autumn to winter months. A second rapid growth occurred the following summer. Based on the growth pattern, the life span of H. tokunagai was estimated to be more than 20 months. This longer life span compared to other eulimids could be due to the accessibility and population stability of its host S. mirabilis. Maturation of H. tokunagai occurred within a short period in the summer, and was synchronized with the second growth phase. Hypermastus tokunagai showed size dimorphism between sexes and an investigation on change in shell shape with growth revealed that this characteristic can be attributed to the female's acquisition of a larger shell within a short time during its maturation period.

塩化ビニール製パイプの人工巣穴を敷設した 3 水槽で体重 89～217 g のハモ 8 個体ずつを流水下で飼育し，巣穴に対する出入行動の日周および季節変化を調べた。2009 年 8, 10, 12 月，2010 年 2, 4, 6 月の計 6 日，1 時間ごとに 24 時間，巣穴外および遊泳個体数を目視により計数した。ハモは照度が 0 lx となる日没から早朝に巣穴から出て遊泳し，昼間には巣穴内で沈静した。水温の上昇とともに巣穴外および遊泳個体数が増加し，水温の低下とともに減少した。これらの出入行動は漁獲の日周および季節変化と一致する。

北海道の青色型マナマコについて，体長 L と体幅 B から推定麻酔体長 Le (mm) を求める回帰関係を調べ，瀬戸内海［Le=2.32+2.02・(L・B)1/2］と比較した。その結果，明らかな差が認められたことから次の回帰式を提案した:北海道オホーツク海［Le=2.26・(L・B)1/2]；日本海［Le=2.17・(L・B)1/2]；噴火湾［Le=2.21・(L・B)1/2]；津軽海峡［Le=2.27・(L・B)1/2]；青森県陸奥湾［Le=5.82+2.02・(L・B)1/2]。また，マナマコの形態が北海道と本州で異なることを考慮し，次の共通式を提案した:北海道［Le=2.21・(L・B)1/2]；本州［Le=5.30+2.01・(L・B)1/2]。

In order to determine the population dynamics of juvenile Apostichopus japonicus, successive surveys were conducted in the stony intertidal zone of Hirao Bay, Seto Inland Sea. The juveniles of the green and black types of this species grew well from January to June. Before this high growing season, zero year old juveniles were too small to be readily detected by visual observations during field surveys. During the high water temperature season from August to November, juveniles over 1 year of age estivated underneath rocks. They awakened from their estivation in November, and it took another month before they could eat and discharge. The juveniles mainly migrated from the intertidal zone before they reached 3 years of age. In the present work, three patterns of juvenile growth were found. It is suggested that these differences in juvenile growth are mainly caused by differences in their start times for growth initiation when they are zero years old.

[Agricultural channels can be important habitats for aquatic species inhabiting agricultural areas. However, water supply in agricultural channels can vary substantially with types of agriculture and irrigation/drainage system, and thereby affect the viability of local populations of aquatic species. In this study, we focused on the amphidromous freshwater atyid shrimp Caridina leucosticta. To clarify whether C. leucosticta utilizes agricultural channels as a habitat in relation to fluctuations in the water supply, we conducted a series of field surveys on the distribution of this shrimp in a rice paddy drainage channel (spring-fed channel) around the Furu River, central Japan, during July and December 2008. Large numbers of C. leucosticta had migrated into that drainage channel. Water from the adjacent rice paddies had disappeared by October, because irrigation was stopped, but the water level in the drainage channel was maintained by a supply of spring water. By mid-November the supply of spring water had almost disappeared, then the channel nearly dried up, and many shrimps were concentrated in an isolated water pool in the channel. Thus, habitat fragmentation of C. leucosticta occurred in terms of water (dis-)continuity. This water pool dried up completely by mid-December. We found many dead individuals of C. leucosticta in the dried-up area of the channel. These results indicate that agricultural channels can be an important temporal habitat for amphidromous freshwater shrimps, but that the drying-up of the channels can lethally affect migrating atyid shrimps. Les canaux agricoles peuvent etre des habitats importants pour les especes aquatiques rurales. Cependant l'alimentation en eau des canaux agricoles peut varier substantiellement avec le type d'agriculture, les systemes d'irrigation/drainage et en consequence affectent la viabilite des populations locales des especes aquatiques. Cette etude est centree sur la crevette atyidee amphidrome d'eau douce Caridina leucosticta. Pour eclaicir si C. leucosticta utilise les canaux agricoles comme habitat en relation avec la fluctuation de l'apport en eau, nous avons conduit une serie de releves de terrain sur la distribution de cette crevette dans un canal de drainage de riziere (eau de source) pres de la riviere Furu, Japon central, durant Juillet et Decembre 2008. Un grand nombre de C. leucosticta ont migre dans ce canal de drainage. L'eau des rizieres adjacentes a disparu en Octobre, car l'irrigation a stoppe, mais le niveau de l'eau a ete maintenu par un apport d'eau de source. Mi-Novembre l'apport d'eau de source a presque disparu, ce qui a pratiquement asseche le canal, et de nombreuses crevettes etaient concentrees dans des flaques isolees du canal. Ainsi la fragmentation de l'habitat de C. leucosticta est due a la discontinuite en eau. Ces flaques d'eau ont seche completement mi-Decembre. De nombreux individus morts ont ete trouves dans parties assechees du canal. Ces resultats indiquent que les canaux agricoles peuvent etre un important habitat temporaire pour les crevettes d'eau douce amphidromes, mais que l'assechement de ces canaux peut affecter de facon letale les crevettes atyides migratrices., Agricultural channels can be important habitats for aquatic species inhabiting agricultural areas. However, water supply in agricultural channels can vary substantially with types of agriculture and irrigation/drainage system, and thereby affect the viability of local populations of aquatic species. In this study, we focused on the amphidromous freshwater atyid shrimp Caridina leucosticta. To clarify whether C. leucosticta utilizes agricultural channels as a habitat in relation to fluctuations in the water supply, we conducted a series of field surveys on the distribution of this shrimp in a rice paddy drainage channel (spring-fed channel) around the Furu River, central Japan, during July and December 2008. Large numbers of C. leucosticta had migrated into that drainage channel. Water from the adjacent rice paddies had disappeared by October, because irrigation was stopped, but the water level in the drainage channel was maintained by a supply of spring water. By mid-November the supply of spring water had almost disappeared, then the channel nearly dried up, and many shrimps were concentrated in an isolated water pool in the channel. Thus, habitat fragmentation of C. leucosticta occurred in terms of water (dis-)continuity. This water pool dried up completely by mid-December. We found many dead individuals of C. leucosticta in the dried-up area of the channel. These results indicate that agricultural channels can be an important temporal habitat for amphidromous freshwater shrimps, but that the drying-up of the channels can lethally affect migrating atyid shrimps. Les canaux agricoles peuvent etre des habitats importants pour les especes aquatiques rurales. Cependant l'alimentation en eau des canaux agricoles peut varier substantiellement avec le type d'agriculture, les systemes d'irrigation/drainage et en consequence affectent la viabilite des populations locales des especes aquatiques. Cette etude est centree sur la crevette atyidee amphidrome d'eau douce Caridina leucosticta. Pour eclaicir si C. leucosticta utilise les canaux agricoles comme habitat en relation avec la fluctuation de l'apport en eau, nous avons conduit une serie de releves de terrain sur la distribution de cette crevette dans un canal de drainage de riziere (eau de source) pres de la riviere Furu, Japon central, durant Juillet et Decembre 2008. Un grand nombre de C. leucosticta ont migre dans ce canal de drainage. L'eau des rizieres adjacentes a disparu en Octobre, car l'irrigation a stoppe, mais le niveau de l'eau a ete maintenu par un apport d'eau de source. Mi-Novembre l'apport d'eau de source a presque disparu, ce qui a pratiquement asseche le canal, et de nombreuses crevettes etaient concentrees dans des flaques isolees du canal. Ainsi la fragmentation de l'habitat de C. leucosticta est due a la discontinuite en eau. Ces flaques d'eau ont seche completement mi-Decembre. De nombreux individus morts ont ete trouves dans parties assechees du canal. Ces resultats indiquent que les canaux agricoles peuvent etre un important habitat temporaire pour les crevettes d'eau douce amphidromes, mais que l'assechement de ces canaux peut affecter de facon letale les crevettes atyides migratrices.]

In order to verify which factors affect habitat selection for aestivating and in the active adult Apostichopus japonicus, animals were tested for their selection of attachment site in an experimental device (1-m pipes) in which the perceived environmental stimuli (light intensity, degree of contact with a hard surface, geotaxis) varied depending on the attachment site. During the aestivating season, the animals showed a strong selection for attachment sites during the daytime and nighttime; they also showed positive stereotaxis (thigmotaxis), negative phototaxis, and negative geotaxis. The results suggest that (1) habitats are not suitable for the aestivating adult A. japonicus unless these three environmental requirements are satisfied.

To examine the distribution pattern of adult Apostichopus japonicus, approximately monthly surveys were conducted during a 2-year period in the subtidal zone of a harbor area in Yoshimi Bay, western Yamaguchi Prefecture. Results showed a clear seasonal change in distribution pattern: many animals were distributed on the seabed and the lower part of a jetty during winter to spring, whereas most animals occurred on the upper part of a jetty during summer to autumn, namely, the aestivation season. Such change is considered to be due to the migration of animals within the present study site.

It has been suggested that the Japanese sea cucumber, Apostichopus japonicus, has three color types (red, green, and black), although the qualitative difference between the color types, particularly between the green and black types, is unclear because of continuous color variation among color types. This study elucidated the color variation between green and black types using image processing (RGB, red–green–blue system) and multivariate analysis to demonstrate whether or not the black and green types can be quantitatively classified. Moreover, spatial variation of the RGB value among various local sites was clarified to estimate potential environmental factors that may affect the color variation. The series of analyses revealed that a quantitative boundary between green and black types could be provisionally established, and also that spatial variability in the intermediate (continuous) color trait between green and black types was significant. Potential environmental factors (depth and industrial activity index) were correlated with the color traits in both color types. These results suggest that the green and black types cannot be regarded as independent color traits and that the color variation between green and black types may be influenced by local environmental factors.

To specify the aestivation site of Apostichopus japonicus, an individual tracking survey was carried out in the jetty in Yoshimi Bay, western Yamaguchi Prefecture. Ten marked animals were released and continuously tracked for one summer. Their aestivation sites were not in the mud that was once considered as the main aestivating habitat of this species, but in the narrow space between shells on the steel sheet-pile wall in the bend of the jetty, and the undersurface of the overhang-structure in the quay. We conclude that underneath of the rock tracts and boulder stones are the natural aestivating habitats.

山口県馬島沿岸でのアマモとカシパン類の種間関係を明らかにするため，春期に分布調査を実施した。ハスノハカシパンはアマモが低密度の区画で 30 個体/m2 と高い密度で生息し，アマモが 200 株/m2 の区画では 4 個体/m2 であった。春～夏に水槽内同居実験を実施したところ，ハスノハカシパンとスカシカシパンはアマモを移植していない場所に多く出現した。また，アマモへの接触は認められたが，倒して枯死させることはなく，草体は順調に生育した。以上のことから，両種とアマモの分布域をめぐる種間関係は中立であると考えられた。

[Species composition and abundance of decapod crustaceans were studied in the waters off Geoje Island, located off the southeastern coast of Korea, using a shrimp beam trawl from November 2000 to October 2001. Water temperature above the sea bottom was lowest ( 25°C) in August. A total of 196,149 individuals of 41 species from 17 families and 3 suborders was observed. Shrimps (Macrura Natantia) accounted for 23 species, hermit crabs (Anomura) and crabs (Brachyura) for 7 and 11 species, respectively. Crangon hakodatei was the most abundant species both in terms of overall number and biomass. Total biomass showed three peaks during the study period. The first peak in January was due to C. hakodatei and Charybdis bimaculata. The second and third peak were due to C. hakodatei and Palaemon gravieri. Cluster analysis, based on monthly abundance data of the 12 dominant species, showed that the species could be separated into three different groups: resident, seasonal, and temporary. The decapod community structure in the study area was predominantly affected by the resident group. La composition specifique et l'abondance des Crustaces Decapodes ont ete etudiees dans les eaux de l'ile Geoje, situee pres de la cote sud-est de la Coree, a l'aide d'un chalut a crevette entre novembre 2000 et octobre 2001. La temperature de l'eau du fond a ete la plus basse en mars ( 25°C) en aout. Au total 196149 individus appartenant a 41 especes de 17 familles et 3 sous-ordres ont ete observes. Les crevettes (Macroures Natantes) sont representees par 23 especes, les Bernard l'Hermite (Anomoures) et les crabes (Brachyoures) par 7 et 11 especes respectivement. Crangon hakodatei a ete l'espece la plus abondante, a la fois en termes de nombre d'individus et de biomasse. La biomasse totale a montre trois pics durant la periode etudiee. Le premier pic, en janvier etait du a C. hakodatei et Charybdis bimaculata. Le second et le troisieme pics, etaient dus a C. hakodatei et Palaemon gravieri. L'analyse des groupements, basee sur les donnees d'abondances mensuelles des 12 especes dominantes a montre que les especes pouvaient etre separees en 3 groupes differents: les residentes, les saisonnieres et les temporaires. La structure de la communaute des Decapodes dans la zone etudiee est conditionnee de facon predominante par le groupe des especes residentes., Species composition and abundance of decapod crustaceans were studied in the waters off Geoje Island, located off the southeastern coast of Korea, using a shrimp beam trawl from November 2000 to October 2001. Water temperature above the sea bottom was lowest ( 25°C) in August. A total of 196,149 individuals of 41 species from 17 families and 3 suborders was observed. Shrimps (Macrura Natantia) accounted for 23 species, hermit crabs (Anomura) and crabs (Brachyura) for 7 and 11 species, respectively. Crangon hakodatei was the most abundant species both in terms of overall number and biomass. Total biomass showed three peaks during the study period. The first peak in January was due to C. hakodatei and Charybdis bimaculata. The second and third peak were due to C. hakodatei and Palaemon gravieri. Cluster analysis, based on monthly abundance data of the 12 dominant species, showed that the species could be separated into three different groups: resident, seasonal, and temporary. The decapod community structure in the study area was predominantly affected by the resident group. La composition specifique et l'abondance des Crustaces Decapodes ont ete etudiees dans les eaux de l'ile Geoje, situee pres de la cote sud-est de la Coree, a l'aide d'un chalut a crevette entre novembre 2000 et octobre 2001. La temperature de l'eau du fond a ete la plus basse en mars ( 25°C) en aout. Au total 196149 individus appartenant a 41 especes de 17 familles et 3 sous-ordres ont ete observes. Les crevettes (Macroures Natantes) sont representees par 23 especes, les Bernard l'Hermite (Anomoures) et les crabes (Brachyoures) par 7 et 11 especes respectivement. Crangon hakodatei a ete l'espece la plus abondante, a la fois en termes de nombre d'individus et de biomasse. La biomasse totale a montre trois pics durant la periode etudiee. Le premier pic, en janvier etait du a C. hakodatei et Charybdis bimaculata. Le second et le troisieme pics, etaient dus a C. hakodatei et Palaemon gravieri. L'analyse des groupements, basee sur les donnees d'abondances mensuelles des 12 especes dominantes a montre que les especes pouvaient etre separees en 3 groupes differents: les residentes, les saisonnieres et les temporaires. La structure de la communaute des Decapodes dans la zone etudiee est conditionnee de facon predominante par le groupe des especes residentes.]

Anesthetized body length (La), an accurate measurement of body size of Japanese sea cucumber Apostichopus japonicus, is measured by using /-methol anesthetizer but it is difficult to apply La in the field. An estimation method of La from only one simultaneous measurement of body length (L) and body breadth (B), regardless of the degree of contraction or extension of the body, is proposed. In simultaneous measurement of L and B for each of 150 animals of both the green and the black types of A. japonicus, there were significant negative correlations between L and B in all animals. Further, √(LxB) was approximately constant regardless of the animals’ body form (coefficient of variance: 0.01–0.06). Thus, the regression equations for Le, estimated La, were calculated: the green type, Le=2.32+2.02×√(L·B); and the black type, Le=1.34+2.12×√(L·B). The error values between Le from these equations and La were small. The variances of Le were approximately one-quarter of those of L and half of B. From these, the equations can be used for body size measurements taken in the field.

降河中のモクズガニが，堰堤から安全に落下できる条件を明らかにするために実験を行った。甲幅約 5 cm の個体がコンクリートに落下する場合，落差 1 m で歩脚が損傷する個体が出現したが，その後 15 日間の飼育で 10 個体すべて生残した。落差 2 m 以上では死亡する個体が現れ，落差 5 m 以上では全 80 個体が死亡した。落差 11 m から水深 60 cm のプールへ落下した個体は損傷を受けずすべて生残した。甲幅約 8 cm の大型個体も，水深が 50 cm 以上のプールがあれば，落差 10 m から落下しても安全であると結論した。

伸縮する成体マナマコの体長を正確に測定するために，麻酔方法を検討した。未変性エタノールの 10% 海水希釈液にメントールを飽和溶解させ，これを濾過して基準液を作成した。基準液の 40% 海水希釈液が，成体マナマコに対して効果的な麻酔剤であった。この麻酔液に浸漬したナマコは，体色型，体サイズ，水温に関係なく，体長変化が止み，口縁触手が弛緩して伸び，かつピンセットで体表を突付いても無反応な状態となった。麻酔時の体長は変動幅が小さく，新測定基準として有効と考える。

鹿児島湾の小型底曳網漁船に同乗して採集したヨツトゲシャコSquilloides leptosquilla を用いて, 産卵期および食性を調べた。生殖腺指数の解析結果より, 本種の雌の成熟サイズは頭胸甲長10mmで, 産卵期は5～9月, 産卵盛期は7～9月と推定できた。胃内容物の観察により, 本種は肉食性捕食者で主にエビ類を捕食することがわかった。特に, 鹿児島湾における水産上の有用種であるナミクダヒゲエビSolenocera melantho を捕食している個体の出現頻度が高かった。

The appropriate water velocity in artificial burrows for theJapanese crayfish species Cambaroides japonicus was studied.An experimental system of two artificial burrows (burrows A and B)of the same size was set in a large tank. The velocity of burrowA was 0 cm/s and that of burrow B was varied andset at 0 cm/s, 5 cm/s, 10 cm/s,20 cm/s and 30 cm/s. The selectionof these two burrows by C. japonicus was observed. No animalsselected burrow B significantly more than burrow A above 10 cm/s.At 20 cm/s, some crayfishes were swept away andcould not return to burrows because of the high water velocity.At 30 cm/s, most animals were swept away. We concludethat the appropriate water velocity for the suitability of artificialburrows and the immediate foraging area adjacent to the burrowsshould be as low as 5 cm/s.

Lethal limits of high temperature were studied to clarify the effects on the survival of the endangered Japanese crayfish species Cambaroides japonicus and the alien species Pacifastacus leniusculus. After the acclimation period for 2 weeks at 16°C, the temperature was raised at a rate of 1°C per week. As a result, the ultimate upper lethal temperatures of C. japonicus and P. leniusculus were 27.0 and 31.1°C, respectively, and the lethal temperature for P. leniusculus was significantly higher than for C. japonicus. The natural distributions of these two species are discussed in terms of the temperature tolerance.

SUMMARY: Preference for artificial burrows by the endangered Japanese crayfish species Cambaroides japonicus was studied to improve its cultivation. The occupation of artificial burrows, which were made from straight polyvinyl chloride pipes of different internal diameters (Y, mm), by crayfishes of different total lengths (X, mm) was significantly (P < 0.001, n = 56) described by a linear regression: Y = 0.49X + 3.42 (19.0 ≤X≤ 70.2). Among burrows of different lengths [crayfish total length (TL) × 1, × 2, × 3, and × 4], crayfishes significantly preferred burrows that were greater than TL × 3 (P < 0.001, n = 588).

西日本に分布する両側回遊性ヌマエビ類5種,ヒメヌマエビCaridina serratirostris,トゲナシヌマエビC.typus,ミゾレヌマエビC.leucosticta,ヤマトヌマエビC.japonica,およびヌマエビ(小卵型)paratya compressa compressaの第1・第2ゾエア期幼生について,腹部の色素胞の位置と形状を観察し,それらの出現傾向を記載した.さらにこれを利用して第1・2ゾエア期幼生の種を識別する方法を示し,検索表を作成した., The abdominal chromatophores of the first and second zoeae were examined in five amphidromous atyid shrimps, which are widely distributing in southwest Japan: Caridina serratirostris De Man, C. typus H. Milne Edwards, C. leucosticta Stimpson, C. japonica De Man, and Paratya compressa compressa (De Haan) (small egg type). Chromatophore distribution pattern of larvae was found to be an effective character to identify respective species., 甲殻類の研究=Crustacean research. 1995, 24, p.194-202

Examination of the stomach contents of the Japanese mantis shrimp Oratosguilla oratoria showed that this species is a very intensive predator on the Macrura which is a principal component of the benthic megalofaunal community. Thus, the mantis shrimp, by feeding largely on the Macrura, may have a major influence on this community structure in Hakata Bay. The shrimp was also revealed to be an intensive predator on the Pelecypoda despite underestimation of preda-tion intensity, based on the stomach contents, because of its shell-smashing behaviour. Further-more, this study showed that many Macrura were captured during September and November by the mantis shrimp and that female shrimp of reproductive sizes also consume many Pelecypoda, As a prey species, mantis shrimp themselves were found infrequently in the digestive tracts of other predators.

The Japanese mantis shrimp Oratosquilla oratoria usually lives in the mud bottom. This species excavates a U-shaped tunnel with a sarge and a small opening on a tidal flat; the length of burrow is proportional to occupant size. Artificial burrows of various diameters and lengths were made of polyvinyl chloride pipes and used to study this selective habit in large aquaria. The results showed that the species had a significant preference on the basis of diameter of pipe, but not for pipe length above a lower limit. These facts and behaviour in the artificial burrow suggest that a normal life-cycle is dependent upon habitation of a burrow of compatible size. An artificial burrow of favourable size permits feeding, spawning, etc. and increases survival of mantis shrimp reared in the laboratory.

Samplings of decapod crustaceans were conducted in the Yukinoura River to estimate the influence of a dam having no fishway on the distribution of these animals. Eight decapods were collected from freshwater area. Two of them, Geothelphusa dehaani and Neocaridina denticulata, were landlocked species, and the others were amphidromous or catadromous species. The present fauna can not be compared directly with the fauna before the dam construction because of the absence of comparable studies. Comparing the species composition from respective sampling stations, however, the influence of the dam on their distributions can be estimated as follows: (1) Caridina typus, Macrobrachium japonicum and Macrobrachium formosense could no longer get by the dam into their former habitats. (2) Eriocheir japonicus could reach the dam lake but stopped migrating upstream into its former habitat. (3) Caridina leucosticta had the upper part of its former habitat destroyed by the dam and dam lake. (4) N. denticulata had an expansion of distribution because of the still water environment in the dam lake. (5) G. dehaani was unaffected by the dam. At first glance, Caridina japonica, a resident in the uppermost stream, can be categorized in the fifth category, but its population density seems to have decreased after the completion of dam in 1976.

The spawning and egg mass nursing behaviour, together with the change in external appearance of the egg mass, of the mud-dwelling Japanese mantis shrimp Oratosquilla oratoria were studied using artificial burrows in aquaria. This species usually spawns in a supine posture in the burrow maintaining this posture with the back of abdomen and exopods of uropods against the wall of burrow for almost 3 h. The newly extruded egg mass is amorphous, but the female shrimp compacts it and then shapes it into a thick disc within 1 h and to a thin disc having a marginal turnup within 24 h of spawning. All maxillipeds excluding the raptorial claw are used for the nursing behaviour, i.e. spreading and folding the egg mass, so it is teased out and becomes a tuft shape after 3 days or so. The second gee laying occurred in 2 females about 40 days after the first spawning of each individual at 25°C, and this fact suggests that O. oratoria may spawn more than once in a spawning season in natural warm waters.