Biochemical polymorphism of starry flounder, Platichthys stellatus, from the northwestern and northeastern Pacific Ocean

Three enzyme systems, MDH, PGM and AGPDH, were investigated in starry flounder collected from off northwestern Hokkaido Island, Japan; western Kamchatka; USSR; Puget Sound, Washington, USA; and Yaquina Bay, Oregon, USA. Significant differences in MDH allele distribution were found between the Asian-Puget Sound and Yaquina Bay-Puget Sound samples suggesting that this system may be useful to separate different population units.
The allele frequencies of MDH and PGM did not show significant variation with body length and handedness in starry flounder collected from Puget Sound, Washington, and did not support the hypothesis of differential viability between dextral and sinistrial forms of starry flounder.     

Early growth and development of reciprocal hybrids of the starry flounder Platichthys stellatus and stone flounder Kareius bicoloratus

Larval growth and development of hybrid flounder were observed and compared with those of their parent species. The reciprocal hybrids of female starry flounder Platichthys stellatus and male stone flounder Kareius bicoloratus (hybrid Sb) and of female K. bicoloratus and male P. stellatus (hybrid Bs) both survived and grew to juveniles. Development was divided into nine stages (A–I). Many of the hybrids' traits were identical and intermediate to those of their parents. The position of the eye, however, was primarily sinistral in both hybrids (80% in Sb and 76% in Bs), a trait possessed by P. stellatus (80%) in the western Pacific Ocean. The daily growth rates of the larvae were similar. In the parent species, development was more rapid in P. stellatus than in K. bicoloratus whereas rate of development was intermediate in both Sb and Bs hybrids. The size at settlement [standard length (L_S) at stage H (mean ± s.d. )] was 9·82 ± 1·47 mm for the hybrid Sb and 9·99 ± 0·90 mm for the hybrid Bs, while the minimum age at metamorphosis (initial age at stage H) was 29 days after hatching (DAH) in both hybrids. In comparison, L_S at settlement in parent species was 6·43 ± 0·25 mm for P. stellatus and 12·87 ± 1·29 mm for K. bicoloratus. Minimum age at metamorphosis for the parents was 23 DAH at stage G in P. stellatus and 34 DAH at stage H in K. bicoloratus. Thus, the timing of settlement of hybrids was different from that of their parent species. These traits may occur with high frequency in a natural habitat.     

Physiology of acute silver toxicity in the starry flounder (Platichthys stellatus) in seawater

Physiological effects of exposure to silver (AgCl_n ⁿ⁻¹; 250 μg Ag l⁻¹ or 1000 μg Ag l⁻¹) in seawater fish were investigated using adult starry flounders. While all fish survived up to 10 days in 250 μg Ag l⁻¹, flounders started to die after day 4 in 1000 μg l⁻¹. Dose-dependent increases in plasma and hepatic silver concentrations showed that silver was available for uptake. There were minimal negative effects on hematological parameters, acid-base status, and blood gases. Plasma ammonia showed a pronounced (three- to four-fold), but transient increase in flounders exposed to either 250 μg Ag l⁻¹ or 1000 μg Ag l⁻¹. Whole body ammonia and acid equivalent efflux measurements indicated that ammonia retention was due to a combination of stimulated production and inhibited excretion. In the 1000-μg Ag l⁻¹ group there was a similar transient increase in plasma [magnesium], which was restored by day 4. In contrast, plasma chloride and sodium levels increased gradually towards the point when fish began to die. At 250 μg Ag l⁻¹, the Na⁺/K⁺-ATPase activity of the intestine was unaffected but there was a two-fold increase in branchial Na⁺/K⁺-ATPase activity. The latter effect was interpreted as compensation for an elevated chloride and sodium load. The increases in plasma chloride and sodium concentrations were accompanied by a marked suppression of drinking, thereby indicating that acute silver toxicity was likely caused by a combination of elevated electrolyte concentrations and dehydration. Accepted: 9 June 1999     

Specific features of the external morphology of starry flounder Platichthys stellatus at atavism in the body color

An analysis of the morphology of starry flounder Platichthys stellatus, completely pigmented from both sides, was performed. It considerably differs from common individuals (pigmented from only one side) by several characters. The right eye in the atavistic specimen was located on the upper part of the head, and there was a deep notch between the eye and the dorsal fin. The differences between body proportions and sizes of fins in bilaterally pigmented and common flounder specimens were also detected. Based on an analysis of the data obtained, opinions concerning the causes of these morphological deviations in bilaterally pigmented flounder individuals are provided.     

Freshwater adaptation during larval, juvenile and immature periods of starry flounder Platichthys stellatus, stone flounder Kareius bicoloratus and their reciprocal hybrids

The freshwater tolerance of starry flounder Platichthys stellatus , stone flounder Kareius bicoloratus and their reciprocal hybrids, produced by artificial insemination, were examined in the larval, juvenile and immature phases. Survival rate on being transferred to fresh water in the pre-settlement phase was 0% in stone flounder and hybrids and 16·7% in starry flounder. This rate in the post-settlement phase was elevated to >50% in starry flounder and hybrids but was still 0% in stone flounder and similarly in the immature period starry flounder and hybrids survived in fresh water, although stone flounder did not. The lamella chloride cells of the gill epithelium increased in starry flounder and hybrids in fresh water in all periods. Densities of lamella chloride cells increased from 1·6 ± 0·4 (mean ± s . e . number of cells per 1 mm filament) before the transferral (day 0) to 60·3 ± 6·2 on 14 days after the transfer to fresh water (day 14) in starry flounder in the immature period. These densities in hybrids were 0·6 ± 0·3 and 1·0 ± 0·3 on day 0, and, 35·3 ± 2·8 and 23·2 ± 4·6 on day 14, respectively. Stone flounder did not show a substantial change in chloride cell densities throughout the experimental period. These results suggest that low salinity tolerance was well developed in the settlement period in starry flounder and hybrids, and hybrids were also adapted to fresh water sufficiently regardless of the cross type.     

Isolation and characterization of polymorphic microsatellite loci from a dinucleotide-enriched genomic library of starry flounder (Platichthys stellatus) and cross-species amplification

Starry flounder (Platichthys stellatus) is a rare fish species in China. Here, we reported 12 polymorphic microsatellite loci isolated from a dinucleotide-enriched genomic library of starry flounder (P. stellatus). The number of alleles, observed and expected heterozygosity per locus in 30 individuals ranged from two to six, from 0.2500 to 1.0000 and from 0.4512 to 0.7667, respectively. One locus significantly deviated from Hardy–Weinberg equilibrium after Bonferroni correction and no significant linkage disequilibrium between pairs of loci was found. Cross-species amplification of these microsatellite loci in additional three fish species was performed. These polymorphic microsatellite loci would be useful for investigating genetic population structure and construction of genetic linkage map in P. stellatus. Guidong Miao and Changwei Shao have contributed equally.     

Genetic diversity and differentiation of the Korean starry flounder (Platichthys stellatus) between and within cultured stocks and wild populations inferred from microsatellite DNA analysis

The Korean starry flounder, Platichthys stellatus, is economically valuable coastal resident fish species. However, the annual catch of this fish has fluctuated and suffered major declines in Korea. We examined the genetic diversity and population structure for four wild populations and three hatchery stocks of Korean starry flounder to protect its genetic integrity using nine microsatellites. A group of 339 genotypes belonging to seven populations were screened. High degrees of polymorphism at the microsatellite loci were observed within both the wild and hatchery populations. Compared to the wild populations, genetic changes, including reduced genetic diversity and highly significant differentiation, have occurred in cultured stocks. Significant population differentiation was also observed in wild starry flounder populations. Similar degrees of inbreeding and significant Hardy–Weinberg equilibrium deviations were detected in both the wild and the hatchery populations. The genetic connectivity pattern identified four distinct metapopulations of starry flounder in Korea by clustering in the phylogenetic tree, Bayesian analyses, molecular variance analysis, PCA and multidimensional scaling analysis. A pattern of isolation-by-distance was not significant. This genetic differentiation may be the result of the co-effects of various factors, such as historic dispersal, local environment or anthropogenic activities. These results provide useful information for the genetic monitoring of P. stellatus hatchery stocks, for the genetic improvement of this species by selective breeding and for designing suitable management guidelines for the conservation of this species.     

The comparative ultrastructure of the egg membrane and associated pore structures in the starry flounder,Platichthys stellatus (Pallas), and pink salmon,Oncorhynchus gorbuscha (Walbaum)

Eggs of the starry flounder (Platichthys stellatus) and pink salmon (Oncorhynchus gorbuscha) were examined by scanning and transmission electron microscopy to determine differences in egg membrane structure with reference to contrasting ecological conditions in which the eggs normally develop. The egg membrane of the starry flounder constitutes 0.22--0.50% of the egg's diameter. The zona radiata is composed of 6 continuous horizontal lamellae, covered by a thin triple layered border, and pierced by numerous regularly spaced pore canals. The micropyle canal measures 8 microns at the opening and tapers to 3.6 microns as it penetrates the membrane. In contrast, the thicker membrane of the pink salmon egg forms 0.80--1.0% of the egg's diameter, is composed of numerous short discontinuous lamellae which are pierced by pore canals, and is covered by a coating of irregular thickness. The 15--16 micron micropyle opening is surrounded by an area of protrusions, and the funnel-shaped canal tapers to 2 microns at its terminal aperture. Contrasting environmental conditions during embryogenesis of these two species may be reflected by the thin membrane and simple lamellar structure in the pelagic egg of the starry flounder, and the thick membrane and complex lamellar structure in the demersal egg of the pink salmon.     

Which way to turn? Effect of direction of body asymmetry on turning and prey strike orientation in starry flounder Platichthys stellatus (Pallas) (Pleuronectidae)

Starry flounder Platichthys stellatus , a rare polymorphic flatfish exhibiting a large-scale geographic cline in the frequency of right-eyed (dextral) and left-eyed (sinistral) morphs, was studied to investigate whether foraging behaviour (turning angle and prey strike orientation) differed between dextral and sinistral laboratory-raised juveniles. Platichthys stellatus foraging on brine shrimp Artemia sp. nauplii tended to strike dorsally at prey ('left' to an observer for dextral flounder and 'right' to an observer for sinistral flounder), although this effect was stronger for sinistral fish. This dorsal tendency also increased with body size. Non-strike behaviours (movements between strikes) were ventrally biased for both morphs. Maximum turn angles were larger for both morphs towards the dorsal side than the ventral side during prey strikes but were the same during non-strike behaviours. The positioning of the eyes of the juvenile starry flounder was skewed towards the dorsal midline rather than being symmetrically placed between dorsal and ventral margins on the eyed side of each fish. The migrating eyes of dextral fish, however, were significantly closer to the dorsal midline than in sinistral fish. This, in addition to the more dorsally oriented prey strikes in sinistral fish, suggests that the morphs are not simple behavioural mirror images of one another and therefore may differ ecologically.     

Bacterial diversity in deep-sea sediment from northeastern Pacific Ocean

16S rDNA sequencing method is one of the effectively used culture-independent techniques in recent years. In this study, 16S rDNA sequencing method was used to investigate the bacterial diversity in deep-sea sediment from northeastern Pacific polymetallic nodule province. Total DNAs were extracted by using 2 different methods (chemical method and DNA extracting kit method). After purification, genomic DNA was amplified by using 2 universal primers (27F and 1492R). Clones were selected and sequenced randomly. After the sequences were checked by using the Chimera Check Program of the RDP database, a bacterial 16S rRNA gene library of 79 clones was established. Phylogenetic analysis indicated that 79 clones could be divided into 11 phylotypes. Gamma Proteobacteria (22.8%) and alpha Proteobacteria (16.5%) were the dominant components of the sediment bacterial community, followed by Planctomycetacia (7.6%), delta Proteobacteria (6.3%), Nitrospira (6.3%), Actinobacteria (6.3%), beta Proteobacteria (5%), Acidobacteria (5.1%), Sphingobacteria (3.8%), Firmicutes (2.5%) and uncultured bacteria (17.7%). Gamma Proteobacteria also dominated at slices 0–2 cm and 4–6 cm. Different slices had different types of bacteria, alpha Proteobacteria, gamma Proteobacteria, delta Proteobacteria, Planctomycetacia, Nitrospira, Actinobacteria and Acidobacteria, however, appeared in all slices. Pseudomonas is common in many different deep-sea environments. In this study, it accounted for 22.2% of the total gamma Proteobacteria.     

Urotensin I and its N-terminal flanking peptide from the flounder, Platichthys flesus

The caudal spinal cord region of teleost fish terminates in a neurosecretory organ, the urophysis. Two peptides have been purified to homogeneity from an extract of the urophysis of a teleost fish, the flounder. The primary structure of one peptide, Ser-Glu-Asp-Pro-Pro-Met-Ser-Ile-Asp-Leu10-Thr-Phe-His-Met-Leu-Arg- Asn-Met-Ile- His20-Met-Ala-Lys-Met-Glu-Gly-Glu-Arg-Glu-Gln30-Ala-Gln-Ile- Asn-Arg-Asn-Leu-Leu - Asp-Glu40-Val, indicates identity with urotensin I. By analogy with other urotensins, the COOH-terminal residue is probably alpha-amidated. A second peptide was present in the extract in a concentration that was approximately equimolar with that of urotensin I. The amino acid composition of this peptide indicated a total of approximately 65 residues. The amino acid sequence of a fragment produced by digestion with trypsin was established as: Ala-Ala-Ala-Ala-Gly5-Asp-Ser-Ala-Ala-Ser10-Asp-Leu-Leu-Gly-Asp1 5-Asn-Ile-Leu- Arg. This sequence shows partial homology to carp prepro-urotensin I(41-59)-peptide as deduced from the nucleotide sequence of a cloned cDNA. It is concluded that the second peptide probably represents the N-terminal flanking peptide of pro-urotensin I which, it has previously been suggested, may function as a urotensin-binding peptide (urophysin) analogous to the neurophysins.     

Direct development of the brittle star Amphiodia occidentalis (Ophiuroidea, Amphiuridae) from the northeastern Pacific Ocean

Abstract. The highly modified development of the brittle star Amphiodia occidentalis is described from post-fertilization to the juvenile stage. Fertilized eggs are negatively buoyant, ∼190 μm in diameter, surrounded by a thick hyaline layer and a tough fertilization envelope. After gastrulation, embryos flatten into a bilaterally symmetrical disk with a U-shaped ridge surrounding an indented stomodeum on the oral surface. Internally, a ring of ∼22 calcitic ossicles grows at the edge of the disk. Vestigial ophiopluteal structures such as a ciliated band, paired larval spicules, or larval arms are not expressed during development. Although the fertilization envelope disintegrates on day 3, developmental stages remain immotile for five more days until they move with podia. At hatching, five hydrocoelic lobes are evident on the left side of the post-gastrula, and these migrate clockwise around the stomodeum, establishing pentamerous radial symmetry. Central and radial plates originate on the right side and migrate to a dorsocentral location as pentamerous symmetry is established. Development of the juvenile oral skeletal frame follows closely that described by Hendler (1978) for Amphioplus abditus except that A. occidentalis did not form buccal scales. The juvenile mouth opened by day 12. Fifty-five days after fertilization, juveniles had not added their first arm segments, although the first lateral arm plates had appeared. Developmental stages identical to those described here have been found in plankton tows taken in Oregon usually after storms that bring high waves. The unusual development of this species probably occurs in both benthic and pelagic environments.     

Vascular pathways in the gill filaments of the flounder, Platichthys flesus L.

This study is concerned with functional organization of some of the blood pathways in the gill filament of the flounder, Platichthys flesus L. The existence of two independent vascular pathways has been confirmed. The blood from the efferent filament artery (EFA) enters the central venous sinus (CVS) through very small blood vessels which are characterized by the presence of sphincter-like structures. The existence of an independent chamber of the CVS mainly full of white blood cells provides evidence of an independent lymphatic system connected to the CVS. Gill rays support the afferent side of a gill filament whereas plasma and an extensive network of nutritive blood vessels in the CVS supports the efferent part.     

Saurida fortis,a new species of lizardfish (Aulopiformes: Synodontidae) from the northwestern Pacific Ocean

Ichthyological Research - Saurida fortis sp. nov., a lizardfish (Aulopiformes: Synodontidae) from the northwestern Pacific Ocean, previously misidentified as Saurida umeyoshii Inoue and Nakabo 2006...     

Metals in the tissues of the starry flounderPleuronectes stellatus from Nyiskii Bay (Southeastern Sakhalin)

We examined the concentrations of the heavy metals Zn, Cu, Cr, Pb, and Cd in the liver, gonads, and muscles of male and female starry flounderPleuronectes stellatus from Nyiskii Bay (off the northeastern coast of Sakhalin) in August 1996. It is shown that the accumulation of the metals was different in the organs and tissues of males and females. The greatest differences were recorded in the gonads. The concentrations of Zn and Cu were greater in the gonads of females, whereas the concentrations of Cd, Pb, and Cr were greater in male gonads. More Cd and Pb accumulated in the liver of females, whereas the concentrations of Zn and Cd were greater in the muscles of males. The results obtained seem to reflect the specific features of physiological processes in specimens of different sexes and the biochemical composition of the tissues of fish organs during the period of foraging and gonad development. The concentrations of metals in the muscles of starry flounder from Nyiskii Bay did not exceed the sanitary standards.     

Reproductive Biology and Ecology of Shortspine Thornyhead Rockfish, Sebastolobus alascanus, and longspine thornyhead rockfish, S. altivelis, from the northeastern Pacific Ocean

We examined the reproductive biology and estimated life history parameters for female shortspine thornyhead, Sebastolobus alascanus, and longspine thornyhead, S. altivelis, from histological samples prepared from specimens collected from both Alaska and the West Coast of the United States. Both species spawn pelagic gelatinous egg masses, although timing differs between taxa and locations. Shortspines spawn between April and July in Alaska and between December and May along the West Coast. Longspines spawn between January and April along the West Coast. Length at 50% maturity differed between species and areas, with shortspines at 21.48cm in Alaska and 18.19cm on the West Coast, and longspines at 17.83cm on the West Coast. We used the gonadosomatic index to estimate instantaneous rates of natural mortality (M). Values of M differed little between species and areas despite substantial differences in temperature and dissolved oxygen concentrations. Estimates for shortspines from both Alaska and the West Coast ranged between 0.013 and 0.017, while longspines from the West Coast showed an M value of 0.015. Such low estimates of M suggest Sebastolobus are extremely long-lived.     

Characterization of Digestive Enzymes in the Intestine of the Pacific Halibut Hippoglossus stenolepis Schmidt, 1904 and the Starry Flounder Platichthys stellatus (Pallas, 1788)

The activity and temperature characteristics of hydrolases (maltase, α-amylase, total proteinase, alkaline phosphatase) in the intestine of Far Eastern flatfishes were studied. The character of the temperature dependence differed among the investigated enzymes. The activity of individual hydrolases in the two fish species varied. The results of this study suggest that flatfish intestinal hydrolases are efficient at low temperatures and that the digestive process in flatfishes is well adapted to the conditions in which it functions, thus ensuring optimal vital activity at low temperatures in the Far Eastern seas.Original Russian Text Copyright © 2005 by Biologiya Morya, Korostelev, Nevalenny, Levchenko.