Intraretinal variability and specialization of cones in Japanese anchovy (Engraulis japonicus,Engraulidae)

The retina of anchovies is characterized by an unusual arrangement and ultrastructure of cones. In the retina of Japanese anchovies, Engraulis japonicus, three types of cones are distributed into rows. The nasal, central, temporal, and ventro‐temporal regions of the retina were occupied exclusively by the long and short cones. Triple cones, made up of two lateral components and one smaller central component, were found only in the dorsal and ventro‐nasal retinal regions. In the outer segments of all short and long cones from the ventro‐temporal region, the lamellae were oriented along the cell axis and were perpendicular to the lamellae in the long cones, providing a morphological basis for the detection of polarization. This lamellar orientation is unique to all vertebrates. The cones were examined with respect to regional differentiation in their size and spectral properties via light microscopy, transmission electron microscopy, and microspectrophotometry. Various dimensions of cones were measured in preparations of isolated cells. The cones from the ventro‐temporal region had different dimensions than cones of the same type located in other retinal regions. Triple cones from the dorsal region were significantly larger than triple cones from the ventro‐nasal region. The spectral absorbance of the lateral components of triple cones in the ventro‐nasal retina was identical to the absorbance of all long and short cones from the ventro‐temporal region. These are shifted to shorter wavelengths relative to the absorbance of the lateral components of the triple cones located in the dorsal retina. Thus, the retina of the Japanese anchovy shows some features of regional specialization common in other fishes that improves spatial resolution for the upwards and forwards visual axis and provides spectral tuning in downwelling light environment. That results from the differentiation of cone types by size and by different spectral sensitivity of various retinal areas. J. Morphol. 277:472–481, 2016. © 2016 Wiley Periodicals, Inc.     

A pre-leptocephalus larva ofConger myriaster (family Congridae) collected from Suruga Bay,Central Japan

One specimen of leptocephalus larva, measuring 16.0 mm in total length, was collected from the northern part of Suruga Bay (34°56′N, 138°39′E) by the T/V Bosei Maru II of Tokai University on November 7, 1982. This larva is identified asConger myriaster because of having melanophores under the eye, simple gut with melanophores, 142 total number of myomeres and the position of the last vertical blood vessel at the 52nd myomere. Judging from the body length, appearances of teeth and fins, and disposition of the anus, the present larva belongs to the preleptocephalus stage. The presence of this early larva in this area suggests that one of the spawning grounds ofC. myriaster exists in or near Suruga Bay in autumn.     

Larvae and Juveniles of Temperate Bass, <Emphasis Type="Italic">Lateolabrax latus</Emphasis>, Occurring in the Surf Zones of Tosa Bay,Japan

A total of 343 larval and juvenile Lateolabrax latus (9.2–27.0 mm TL) was collected with a small seine in surf zones of Tosa Bay. They are very similar in general morphology to those of the closely related L. japonicus, but can be distinguished from them by the distribution pattern of melanophores on the tail, head spination, proportion of head length to standard length and the 15 or 16 dorsal fin soft-rays. They occurred in surf zones of Tosa Bay from early January to middle May, being most abundant in middle April. Temperatures and salinities of waters where any number of them were collected ranged from 12.2 to 24.0°C and from 23.7 to 34.5%, respectively. Larval and juvenile L. latus have not been reported so far in coastal and shallow waters, and eelgrass beds of southern Japan. It may be possible that they have been confounded with those of L. japonicus. Their occurrence seems to be limited in extremely shallow waters such as surf zones.     

胶州湾近岸浅水区鱼类群落结构及多样性

根据2009年3月-2010年2月在胶州湾西北部近岸浅水区进行的鱼类逐月定置网调查数据,采用生态多样性指数和多元统计分析等方法研究了该海域的鱼类群落结构及多样性特征.结果表明:调查共鉴定出44种鱼类,其中海洋性27种,河口性鱼类17种.鱼类种类组成与底层水温和盐度有密切关系.胶州湾近岸浅水区鱼类群落Margalef种类丰富度指数(R)变化范围为0.33-3.50,Shannon-Wiener多样性指数(H’)为0.42-2.25,Pielou均匀度指数(J’)为0.23-0.93.聚类分析(CLUSTER)和多维标度排序(MDS)分析表明,不同鱼类种类组成的各月份样品可划分为3个组分:水温较低的冬季组G1(12月-翌年4月)、水温次高的春秋季组G2(5-6月、10-11月)和水温最高的夏季组G3(7-9月).其中G1的典型种主要为尖海龙(Syngnathus acus)、方氏云鳚(Enedrias fangi)和玉筋鱼(Ammodytes personatus)等冷温性常栖类群种类,G2的主要典型种为鳀鱼(Engraulis japonicus)和尖海龙,G3的主要典型种为鲐鱼(Scomber japonicus)、细条天竺鱼(Apogonichthys lineatus)和普氏缰虾虎鱼(Amoya pflaumi)等洄游性鱼类.单因子相似性分析(ANOSIM)表明,3个月份组间鱼类群落结构差异显著,不同月份组间两两差异均显著.生物-环境分析(BIOENV)表明,底层水温是影响胶州湾近岸浅水区鱼类群落结构时间变化的主要环境因子.在胶州湾内近岸浅水区发现40余种幼鱼,但占优势的主要为低值鱼类,表明胶州湾的产卵、肥育场功能有所下降,应加强胶州湾近岸水域生态环境和渔业资源的保护及修复.     

Development,metamorphosis, and natural history of the nudibranch Doridella obscura Verrill (Corambidae: Opisthobranchia)

The doridacean nudibranch Doridella obscura Verrill was raised through one complete generation in laboratory culture, and spawning behavior monitored for a year at monthly intervals in Barnegat Bay, New Jersey.The nudibranch deposited egg masses throughout the year in Barnegat Bay, and the larvae remained viable at temperatures ranging from 1.5 to 28 °C. At 25 °C the eggs hatch 4 days after oviposition, and the planktotrophic veliger larvae swim and feed for 9 days before they metamorphose. Settlement occurs specifically on the bryozoan Electro crustulenta (Pallas). The spirally coiled larval shell grows rapidly until the dorsal mantle fold is retracted from the aperture 5–6 days after hatching. Although starved larvae grow only slightly and do not metamorphose, they resume normal development on introduction of suitable food. Newly metamorphosed juveniles consume algae and debris on the surface of the bryozoan until they grow large enough to attack the living zooids of E. crustulenta.The life cycle of Doridella obscura is short (26 days at 25 °C), allowing the nudibranchs to take advantage of short-lived Electra crustulenta colonies in unstable habitats in bays and estuaries.     

A new species of the grenadier genus <Emphasis Type="Italic">Coelorinchus</Emphasis> (Actinopterygii: Gadiformes: Macrouridae) from the Timor Sea,Eastern Indian Ocean

Coelorinchus okamurai sp. nov. is described from five specimens collected in the Timor Sea at a depth of 610–690 m. The new species belongs to the Coelorinchus japonicus group (redefined in this study), and differs from all other congeners in having the following combination of features: snout moderately long, sharply pointed in lateral and dorsal views, length 39–42% of head length; lateral nasal ridge completely supported by nasal bone; light organ short, length less than 1/2 orbit diameter, its anterior margin falling far short of pelvic-fin bases; premaxillary teeth in short, uniformly wide band, with posterior end of the tooth band not reaching lateral corner of mouth; no teeth greatly enlarged; body scales covered with short, reclined, narrowly blade-like spinules in widely divergent rows; buttresses of body scale spinules scarcely developed; occipital scales between parietal ridges armed with divergent rows of long, erect, needle-like spinules; nasal fossa usually naked (a few small scales rarely present anteroventrally); patches of small scales sparsely distributed on ventral surface of head; scales on underside of head armed with 1–3 rows of short, erect, needle-like to knife-like spinules; interdorsal space longer than first dorsal-fin base length; subopercle terminating as a long, slender flap; body dark overall without prominent markings; fins uniformly blackish.     

Genetic analysis of the populations of Japanese anchovy Engraulis japonicus from the Yellow Sea and East China Sea based on mitochondrial cytochrome b sequence

Japanese anchovy Engraulis japonicus was not only a commercial species but also a key link in the marine food chain in the Yellow Sea and East China Sea. However, in recent years, E. japonicus experienced a deep recession caused by over fishing. Therefore, determination of population genetic structure is essential to underpin resource recovery and to aid delineating and monitoring populations for fishery management. In this study, sequence variation of a 402-bp fragment of mitochondrial cytochrome b (cyt b) gene from ten populations of E. japonicus in the Yellow Sea and East China Sea was determined, detecting 73 haplotypes. Haplotype diversities and nucleotide diversities for the ten populations ranged from 0.4706 ± 0.1177 (D) to 0.9935 ± 0.210 (WH), and from 0.0014 ± 0.0013 (D) to 0.0090 ± 0.0053 (WH), respectively. Analysis of molecular variance (AMOVA) showed no significant differences at all hierarchical levels, and almost all F_ST values were non-significant, indicating no significant population genetic structure in the Yellow Sea and East China Sea. Two indistinct clades with low support values were detected and the analysis of haplotype frequency distribution showed no significant geographic differences among populations. These results supported the null hypothesis that E. japonicus within the Yellow Sea and East China Sea constituted a panmictic mtDNA gene pool. Based on the present study, the existence of separate genetic stocks in the Yellow Sea and East China Sea were not detected. Strong dispersal capacity of planktonic larvae, and ocean current could be the reasons for genetic homogeneity in this species in the Yellow Sea and East China Sea.     

Development of eggs,larvae and juveniles of the puffer,Takifugu chrysops,reared in the laboratory

The artificial fertilization of the puffer,Takifugu chrysops (Hilgendorf), was carried out at Sajima in Yokosuka City on May 22, 1984. Hatched larvae were reared for a period of about 150 days. The spawning period seems to extend from mid to late May in the eastern part of Sagami Bay. The eggs were spherical, pale milky white and semitransparent, demersal and adhesive in nature, measuring 1.32±0.04 mm in diamter, and with a cluster of small oil-globules. The incubation period was about 162 hours at a water temperature of 17.4 to 21.8°C. During embryonic development, the only pigment cells that appeared on the embryo were the black chromatophores. The newly hatched larvae measured from 2.72 to 3.06 mm TL, averaging 2.87±0.1 mm TL, and 22–23 (9 + 13?14) myomeres. At yolk absorption, 4 days after hatching, the larvae attained 3.64–3.79 mm TL. On the 11th day, postlarvae averaged 4.69±0.24 mm TL. Larval finfolds disappeared and rudimental dorsal, anal and caudal fins were formed. There were two large clusters of melanophores, one on the back, exteding from the mid-base of the dorsal fin to the caudal peduncle region, the other along the anal fin base. The color of the body began to turn pale green to brownish-orange and spinelike scales appeared on the belly. Eighteen days after hatching (7.02±0.27 mm TL), the caudal notochord began to turn up and a “constriction” appeared on the posterior margin of the caudal fin membrane. This notch moved upwards as the notochord upturning advances. The larvae attained full fin ray counts and reached the juvenile stage at 9.1-9.5 mm TL, 24 days after hatching. Characteristic black blotches on the back and specific brownish orange body color appeared at the stage of 20 mm TL, 24 days after hatching. The growth during the larval stage and early juvenile stage (24 to 51 days after hatching) were expressed by the following equations, wherey is total length (mm) andx is days after hatching.y ₁=2.8424× 1.0509⁹ (0≦x≦24)y ₂ = 3.7872×1.0372^x (24≦x≦51)     

Effect of copper on the survival of prelarvae of the Japanese anchovy <Emphasis Type="Italic">Engraulis japonicus</Emphasis>

The effects of copper on the prelarvae of the Japanese anchovy, Engraulis japonicus inhabiting the Peter the Great Bay (Sea of Japan) were examined. The median lethal concentrations (LC₅₀) and maximal ineffective concentrations (LC₀) for a 72 hour exposure measured in 2006 and 2007 equaled 8.5 and 0.5 μg/l and 96.3 and 0.7 μg/l respectively. For a 96 hour exposure, LC₅₀ and LC₀ equaled 68 and 0.9 μg/l respectively. The ability of copper to exert negative effects on the survival rate of anchovy prelarvae in areas with intensive anthropogenic pollution was shown.     

Photoreceptor types and their relation to the spectral and polarization sensitivities of clupeid fishes

We used compound action potential recordings from the optic nerve of anesthetized live fish to study the spectral and polarization sensitivities of the northern anchovy and the Pacific herring. The photoreceptor structure and cone mosaic type of the (illuminated) central retina was studied by microscopy. Both species showed a single peak spectral photopic sensitivity function with λ_max= 500 nm for the northern anchovy and λ_max= 520 nm for the herring. However, only the northern anchovy exhibited polarization sensitivity; the response was 180° periodic with maximum sensitivity to horizontal polarization. Similar to the bay anchovy (Fineran and Nicol 1978), the central retina of the northern anchovy showed bifid cone units with cone lamellae parallel to the cones' lengths. The herring, on the other hand, had twin cones arranged in rows with the same orientation and tangentially arranged lamellae. Our results support the hypothesis that bifid cone units act as orthogonal dichroic filters rendering anchovies polarization sensitive. The lack of polarization sensitivity in the herring suggests that twin cones may not be used in polarization sensitivity or that one orientation of polarization receptors is insufficient for the animal to detect polarization direction. Accepted: 8 December 1997     

Effect of natural disturbance on migrations and population dynamics of a catadromous species, Eriocheir japonicus, along the Lo-Mei stream in northern Taiwan

Japanese mitten crab, Eriocheir japonicus (de Haan), migrates between stream and sea and breeds in shallow coastal areas, exhibiting a catadromous life cycle. This study investigated how the crabs adjust reproductive strategy and migratory behavior to climate fluctuation and what kind of life history strategy individual crabs adopt in a disturbed environment. We conducted a 14-year monitoring study from 1998 to 2011 in Lo-Mei Stream in northern Taiwan. Streamflow and flood timing are controlled by precipitation and typhoons. Abundance of crabs was lower after disturbances by several typhoons and by lower temperatures associated with cold winters in 2006 and 2007. Samples from 2003 showed a reversal in reproductive trends, with increasing size in the same pattern of oocytes, compared to reproductive biology from 1999 to 2005. The life history of E. japonicus can be divided into three stages: spawning migration, growth period, and upstream migration of juveniles to compensate for downstream migration of mature crabs. Reproductively, in E. japonicus the combination of semelparity and synchronous breeding can increase reproductive potential and increase survival in a less disturbed environment at the optimum time. Environmental cues play an important role as major triggers in the persistence of populations.     

Review of the <Emphasis Type="Italic">Ostichthys japonicus</Emphasis> complex (Beryciformes: Holocentridae: Myripristinae) in the northwestern Pacific Ocean,with description of a new species

A taxonomic review of the northwestern Pacific Ocean members of the Ostichthys japonicus complex (Holocentridae: Myripristinae), defined by 3.5 scale rows between the lateral line and spinous dorsal-fin base, recognized three valid species: Ostichthys alamai sp. nov., Ostichthys hypsipterygion Randall, Shimizu and Yamakawa 1982 and Ostichthys japonicus (Cuvier in Cuvier and Valenciennes 1829). Ostichthys alamai, based on 10 specimens (118–179 mm SL) from Panay Island, the Philippines and Sulawesi, Indonesia, is similar to O. hypsipterygion in having longitudinal rows of white spots laterally on the body, but has 17 or 18 (modally 17) pectoral-fin rays [vs. 15 or 16 (15) in the latter], the last dorsal-fin spine fused to the first dorsal-fin soft ray (vs. spine and ray separated), and no white blotch on the pectoral-fin base (vs. white blotch present). It differs from O. japonicus, also occurring in the Philippines, in having relatively longer dorsal- and anal-fin spines, a greater number of well-developed long spinules on the body scales, and rows of white spots laterally on the body (vs. generally absent). Detailed comparisons of O. alamai with other members of the complex are made, and revised diagnoses given for O. hypsipterygion and O. japonicus. Ostichthys sheni Chen, Shao and Mok 1990 and Holotrachys major Whitley 1950 are both regarded as junior synonyms of O. japonicus.     

Batch fecundity and spawning frequency of invasive Hemiculter leucisculus (Basilewsky, 1855) in Erhai Lake,China

Hemiculter leucisculus are multiple spawners with indeterminate fecundity, although previous fecundity estimates have assumed a determinate spawning pattern. Batch fecundity and spawning frequency of H. leucisculus were studied in Erhai Lake, China, in which the fish, as an exotic species, has become a successful colonizer. Spawning frequency was 16.05 %, as determined from the percent of females with postovulatory follicles 12 to 36 h old during the peak reproductive period (from May 27 to August 8). The average interval between spawning was 6.2 days and there were more than 16 total spawning batches during the peak reproductive period. The average batch fecundity (mean ± SD) was 11,934?±?5,921 hydrated oocytes in 40 females (standard length or SL: 9.1–14.4 cm), while relative batch fecundity was 560?±?137 eggs g^?1 wet weight. The total potential annual fecundity was approximately 190,944 oocytes over the whole spawning season and was much higher than the estimated standing stock (31,585 oocytes) of yolked oocytes (36 females, SL: 9.5–16.2 cm) at the beginning of the spawning season in April 2010. This high annual fecundity is likely to have contributed to successful invasion of Erhai Lake by H. leucisculus.     

The Use of the Mortality Rate of Marine Fish Prelarvae for the Estimation of Zinc and Lead Toxicity

The effect of zinc on the prelarvae of the Japanese anchovy Engraulis japonicus and on the sand flounder Limanda punctatissima punctatissima and of lead on the prelarvae of the Japanese anchovy was investigated. The median lethal concentrations and maximum ineffective concentrations for a 96-h exposure were calculated. The maximum ineffective concentrations of metals did not exceed their background levels in Peter the Great Bay (Sea of Japan) but were markedly lower than the maximum permissible concentrations (MPC) set for waters of the seas of the Russian Federation. The prelarvae of the Japanese anchovy and the sand flounder can be useful for evaluation and comparison of the toxicity of pollutants and for the estimation of regional MPC levels for pollutants of marine waters.     

The role of mobile consumers in lake nutrient cycles: a brief review

Spawning habitats of anchovy Engraulis encrasicolus and sardinella Sardinella aurita were investigated in the Gulf of Gabès by means of two surveys carried out during the summer of 2005 and 2009. The spatial patterns of early developmental stages were analyzed through Lloyd’s patchiness index, single quotient analyses, and principal component analyses. The results showed that Gulf of Gabès is an important area for anchovy and sardinella spawning. Within this area, anchovy and sardinella showed preference for the warmest waters to spawn. The main spawning areas for anchovy were located in the inner parts of the Gulf, and a secondary spawning area was observed offshore. Contrastingly, the main spawning ground of sardinella was found in the center of the Gulf. In both years, early larvae of anchovy showed a greater degree of aggregation than that of sardinella. The developmental stages of both species showed low spatial overlap, indicating that the spawning habitats of these species are spatially differentiated in the Gulf of Gabès.     

The first data on the biology and distribution of the Japanese fringed sculpin <Emphasis Type="Italic">Porocottus japonicus</Emphasis> Schmidt, 1935 (Scorpaeniformes: Cottidae) in the northwestern Sea of Japan

The Japanese fringed sculpin Porocottus japonicus Schmidt has been found in the Rynda (44°48′03″ N, 136°23′24″ E) and Vladimira (43°52′36″ N, 135°29′30″ E) (Sea of Japan, Primorskii krai) bays for the first time. This species was formerly known only from the northern Tatar Strait and Aniva Bay. In Primorskii krai, P. japonicus inhabits macrophyte beds in shallow sublittoral waters. It reaches a length of 112 mm during its lifespan of approximately 4 years. Spawning occurs in the winter. The species preys predominantly on polychaetes (82.3% of the food weight).     

Influence of environmental variables on the larval stages of anchovy, <Emphasis Type="Italic">Engraulis encrasicolus</Emphasis>, and sardine, <Emphasis Type="Italic">Sardinops sagax</Emphasis>, in Algoa Bay,South Africa

We investigated the environmental drivers of larval abundance of anchovy Engraulis encrasicolus and sardine Sardinops sagax in Algoa Bay, Eastern Cape (South Africa). This study comprised a pre-drought post-drought time period, comparing the responses of the fish larvae to different factors before and after the drought. The current study presents, for the first time, which environmental variables are affecting the anchovy and sardine larvae populations in the region. Easterly wind speed and zooplankton density were the only environmental variables that presented a significant change between the pre- and post-drought periods, increasing after the drought. Generalized additive models (GAMs) were used in order to explore the effects that environmental factors might have in the abundance of anchovy and sardine larvae in Algoa Bay. Specifically, the GAM that best explained the deviance of the anchovy larvae dynamics included the covariates rainfall, easterly wind speed, Chl a concentration, sardine larvae abundance and the interactions SST*Chla and sard*SST. The GAM best explaining sardine larvae abundance included only the easterly wind speed as a covariate. This model showed that there was a positive relationship between the higher values of wind speed and sardine larvae abundance.     

Pelagic eggs and larvae of Coryphaenoides marginatus (Gadiformes: Macrouridae) collected from Suruga Bay, Japan

The pelagic eggs, yolk-sac and pelagic larvae of the macrourid fish, Coryphaenoides marginatus, from Suruga Bay in southern Japan, are described. The identification of the pelagic eggs based on 16S rRNA gene nucleotide sequences agreed with that obtained from morphological analyses. The spherical eggs, 1.14–1.30 mm in diameter, contained a single oil globule 0.30–0.38 mm in diameter, and had hexagonally patterned ornamentation on the chorion, 0.025–0.033 mm in width. Many melanophores were present on the anterodorsal region of the embryo after the caudal end had detached from the yolk. Within a day after hatching, each of the yolk-sac larvae had a body axis that was bent slightly at the anterior trunk region, many dorsal and lateral melanophores on the trunk plus several on the gut, and small irregular wrinkles on the dorsal and anal fin membranes. The pelagic larvae had a short caudal region in comparison to other known congeners (length 2.0–3.2+ times head length vs. 4–7, respectively), a short stalked pectoral fin base, and no elongate first dorsal and pelvic fin rays. They were further characterized by the presence of numerous very dense melanophores from just behind the eye to the anterior part of the caudal region at 5.1 mm head length (25.8+ mm total length). The significant difference in vertical distribution between the pelagic eggs and larvae (dominant depths ca. 200–350 m vs. ca. 10–100 m, respectively), with no subsequent collection of pelagic larvae with greater than 6 mm head length, indicate two stages (rising and falling) of ontogenic vertical migration.     

Diet and prey selection in larval and juvenile Japanese anchovy Engraulisjaponicus in Ariake Bay, Japan

We studied the diet of larval and juvenile Japanese anchovy Engraulis japonicus in the upper Ariake Bay, Japan. Diet was analyzed by examining the digestive tracts; feeding intensity, proportion of empty guts, and prey selectivity were calculated. Anchovy density was negatively influenced by temperature and positively by salinity and prey density. Diet was dominated by Acartia omorii, which was positively selected with two other copepods, Calanus sinicus and Pseudodiaptomus marinus. In contrast, Oithona davisae was highly dominant in the environment but was absent in anchovy guts; thus, this copepod was negatively selected, with two others, Tortanus derjugini and Sinocalanus sinensis. Overall, larger prey were positively selected and smaller ones were negatively selected; value of electivity index correlated negatively with prey size. Larvae [<18 mm of standard length (SL)] showed significantly lower feeding intensities and higher rates of empty guts than juveniles (≥18 mm SL). In juveniles, feeding intensity increased steadily as the fish grew in size, with a corresponding reduction in empty guts. Feeding intensity correlated positively and empty gut correlated negatively with fish size. We suggest that larger prey are important diets for postlarval Japanese anchovy in Ariake Bay.     

Diet Composition and Intensity of Feeding of Tenualosa ilisha (Hamilton, 1822) Occurring in the Northern Bay of Bengal,India

Feeding intensity and diet composition of Hilsa Shad (Tenualosa ilisha) from Northern Bay of Bengal were studied between June 2010 and March 2011. The stomach contents of 320 fishes were analyzed from the northern part of the Bay of Bengal to understand the food items of this species. The major constituents of food are organic debris (26.06 ± 5.19 % SD), diatoms (31.22 ± 11.97 % SD), other algae (12.41 ± 2.62 % SD), and crustaceans (3.50 ± 1.28 % SD). The most abundant species of diatoms were Coscinodiscus, Pleurosigma, Bacillaria, Nitzschia, Biddulphia, Diatoma and Asterionella. The stomach of Hilsa was found to be almost empty during June to October while it was almost full during November to March. Significant positive correlation among feeding intensity, chlorophyll-A concentration and salinity of the ambient water indicated that feeding in T. ilisha is influenced by a number of factors. Strong positive correlation between percentage occurrence of diatoms and intensity of feeding indicated their preference for diatom–food.