Comparative allometric growth of the gastrointestinal tract of two sympatric congeners, copper rockfish (Sebastes caurinus) and quillback rockfish (S. maliger)

Allometric growth of the stomach, intestine, and caeca was compared between two sympatric congeners, the copper rockfish ( Sebastes caurinus ) and the quillback rockfish ( S. maliger ), to examine the species-specific differences in their gut tract in relation to their general feeding habits. The intestine of copper rockfish was shorter and its mass less than the intestine of quillback rockfish. Copper rockfish also had a greater stomach mass and, on average, a greater number of pyloric caeca than quillback rockfish. The differences in the gut allometry between the species were consistent with differences in their general food habits as copper rockfish consume proportionally more fish and larger crustaceans than quillback rockfish.     

Isolation and Characterization of Twelve Microsatellite Loci for Rockfish (Sebastes)

We describe the first microsatellites for rockfishes in the diverse genus Sebastes. Clones containing microsatellites were isolated from the genomic library of a quillback rockfish, Sebastes maliger. Twelve microsatellites are characterized; six of these are polymorphic in quillback rockfish, and eight are polymorphic in at least one rockfish species on which they were tested. The number of alleles per variable locus ranged from 4 to 15 and averaged 6.8. The expected heterozygosities ranged from 0.38 to 0.79 and averaged 0.60 in these loci. These loci should prove valuable in studies examining species identification, population genetics, hybridization, paternity, kinship, and microsatellite evolution. Received September 8, 1998; accepted November 23, 1998.     

Temporal recruitment patterns and gene flow in kelp rockfish (Sebastes atrovirens)

Pelagic dispersal of marine organisms provides abundant opportunity for gene flow and presumably inhibits population genetic divergence. However, ephemeral, fine-scale, temporal and spatial genetic heterogeneity is frequently observed in settled propagules of marine species that otherwise exhibit broad-scale genetic homogeneity. A large variance in reproductive success is one explanation for this phenomenon. Here, genetic analyses of 16 microsatellite loci are used to examine temporal patterns of variation in young-of-year kelp rockfish (Sebastes atrovirens) recruiting to nearshore habitat in Monterey Bay, California, USA. Population structure of adults from central California is also evaluated to determine if spatial structure exists and might potentially contribute to recruitment patterns. Genetic homogeneity was found among 414 young-of-year sampled throughout the entire 1998 recruitment season. No substantial adult population structure was found among seven populations spanning 800 km of coastline that includes the Point Conception marine biogeographic boundary. Comparison of young-of-year and adult samples revealed no genetic differentiation and no measurable reduction in genetic variation of offspring, indicating little variance in reproductive success and no reduction in effective population size for this year class. Simulation analyses determined that the data set was sufficiently powerful to detect both slight population structure among adults and a small reduction in effective number of breeders contributing to this year class. The findings of high gene flow and low genetic drift have important implications for fisheries management and conservation efforts.     

Gastric evacuation of three food types in the black and yellow rockfish Sebastes chrysomelas (Jordan and Gilbert)

The evacuation patterns of shrimp, crab and fish from the stomachs of black and yellow rockfish, Sebastes chrysomelas , were examined by feeding meals of known size and measuring the amount remaining after various post-prandial intervals. Linear, square-root, exponential, power exponential, logistic and Gompertz models (the latter two with unrestricted lower asymptotes, or with lower asymptotes restricted to 0% food remaining) were fitted to the wet weight, dry weight and volume of food remaining in the stomach as a function of post-prandial time. Evacuation patterns ranged from steeply concave (fish wet weight, dry weight, volume, shrimp dry weight), to linear (shrimp wet weight, crab dry weight), to highly convex with lag phases of up to 30 h (crab wet weight, crab and shrimp volume). Friability, the ease with which a food item is fragmented in the stomach, may be an important factor in determining evacuation patterns. The evacuation of a crab meal by tagged, free-ranging S. chrysomelas in the field was not significantly different from that of S. chrysomelas held in the laboratory.     

Paternity testing of wild black rockfish <Emphasis Type="Italic">Sebastes inermis</Emphasis> (brownish type) from the Seto Inland Sea of Japan

We developed four microsatellite DNA loci to test for multiple paternity of black rockfish, Sebastes inermis, from the Seto Inland Sea of Japan. All loci showed a high degree of polymorphism (number of alleles per locus = 10–14, expected heterozygosity = 0.80) and discriminating power (probability of identity index = 3.71 × 10⁻⁶, exclusion probability = 0.999) in unrelated wild specimens (n = 32). Genotypic assignment of five dams (109–220 mm in total length) and 50 embryos from each dam (n = 50) indicated that four dams were mated with a single sire. Only for one dam and three of her embryos we could not exclude multiple paternity.     

Analysis of Microsatellite DNA Polymorphisms in Rockfish Sebastes thompsoni and Application to Population Genetics Studies

Population differentiation and relationships among 6 natural rockfish populations collected from northern coastal seas around Japan were assayed using microsatellite DNA loci. Seven loci examined were polymorphic in all populations. The number of alleles per locus ranged from 6.7 to 9.3, and the average of observed and expected heterozygosity ranged from 0.63 to 0.68, and from 0.66 to 0.69, respectively. The observed genotype frequencies at each locus were almost in agreement with Hardy-Weinberg expectations with two exceptions (P < .05). The allele frequencies of 16 population pairs were significantly different (P < .05). Genetic distance (D _A ) between 6 populations ranged from 0.03 to 0.08. According to a neighbor-joining tree generated from the D _A values, the 6 populations fell into 3 clusters. These clusters were correlated with the geographical positions of each population; larval dispersions due to water current were also found to have an effect on these results. Received May 2, 2000; accepted July 17, 2000.     

Temporal and Spatial Patterns of Epibenthic Macroinvertebrates (EMI) from the San Pedro Shelf,California: Ten-Year Study

Temporal and spatial changes of epibenthic macroinvertebrates (EMI) were described from a ten-year (1985–1995) trawl study on the San Pedro Shelf, California. Community measures including number of species, individuals, biomass, dominance (DI), evenness (J'), and diversity (H' and SR) per trawl were computed for eight trawl stations representing four isobaths. Two reference stations and a test station (located at an ocean outfall) were featured in statistical analyses examining whether the outfall had any effect on EMI. During the ten-year period 127,389 individuals provided 106 EMI taxa. Water depth was the most important factor affecting EMI composition. Although some statistically significant differences in EMI community measures among trawl stations were found. differences between the outfall and both reference stations were either insignificant or inconsistent, providing no obvious ecological impacts attributable to the outfall.     

Stimulative effect of skipjack tuna soluble extract on pepsin-like protease in the stomach of rockfish (Sebastes schlegelii) using an in vitro perfusion method

The effect of intra-gastric infusion of skipjack tuna (Katsuwonus pelamis) muscle soluble extract and of carnosine, anserine and histidine, on pepsin-like protease activity was studied in the isolated, externally batch-cultured stomach of the rockfish (Sebastes schlegelii). Stomach was isolated from the fish, then intragastrically infused with the above solutions or with a balanced saline solution (control solution) as the stimulant at 0.1 mL/min for 6h. Intra-gastric efflux was collected for measurement of pepsin-like protease activity. Skipjack tuna soluble extract, but not carnosine, anserine or histidine alone caused significant enhancement of pepsin-like protease activity during the infusion. Pepsin-like protease activity from skipjack tuna soluble extract responded immediately after infusion and was kept for 150 min after infusion. Stomach motility at the end of infusion was also observed. These results suggest that isolated stomach can receive mucosal side stimulants in vitro. It is likely that some effective components for stomach digestion in fish exist in skipjack tuna soluble extract.     

Multilocus genealogies reveal multiple cryptic species and biogeographical complexity in the California turret spider Antrodiaetus riversi (Mygalomorphae, Antrodiaetidae)

Antrodiaetus riversi (Araneae, Antrodiaetidae) is a dispersal-limited, habitat specialized mygalomorph spider species endemic to mesic woodlands of northern and central California. This species occupies a disjunct distribution, with populations in the Sierra Nevada and Coast Ranges, separated by the inhospitable Central Valley. Previous studies of morphological and allozyme variation have suggested that these populations may constitute cryptic species. We investigated the phylogeography of A. riversi using both nuclear and mitochondrial DNA sequences, collected for a comprehensive population sample. These data reveal the presence of at least five species in the A. riversi complex - these species are deeply diverged, and genealogically exclusive in both nuclear and mitochondrial genomes. Each of these species is characterized by extreme population subdivision and deep phylogeographical structuring, consistent with minimal gene flow across the dissected Californian landscape. Three species are restricted to the Coast Ranges, one to high altitudes of the central Sierran Nevada, and one species is found in both ranges. These species have allopatric distributions, although species parapatry is hypothesized to occur in several areas. Species diversification appears to have pulsed in the Late Miocene/Early Pliocene, a timing consistent with biogeographical reconstructions for many Californian taxa, and a time of turbulent geological activity in the region.     

Parallel amino acid replacements in the rhodopsins of the rockfishes (Sebastes spp.) associated with shifts in habitat depth

Among various groups of fishes, a shift in peak wavelength sensitivity has been correlated with changes in their photic environments. The genus Sebastes is a radiation of marine fish species that inhabit a wide range of depths from intertidal to over 600 m. We examined 32 species of Sebastes for evidence of adaptive amino acid substitution at the rhodopsin gene. Fourteen amino acid positions were variable among these species. Maximum likelihood analyses identify several of these to be targets of positive selection. None of these correspond to previously identified critical amino acid sites, yet they may in fact be functionally important. The occurrence of independent parallel changes at certain amino acid positions reinforces this idea. Reconstruction of habitat depths of ancestral nodes in the phylogeny suggests that shallow habitats have been colonized independently in different lineages. The evolution of rhodopsin appears to be associated with changes in depth, with accelerated evolution in lineages that have had large changes in depth.     

Molecular characterization, expression, and functional analysis of two thioredoxins in the black rockfish (Sebastes schlegelii)

Thioredoxins (TRxs) are a family of small evolutionarily conserved proteins that are essential for the maintenance of cellular homeostasis. Two TRx homologue cDNAs were isolated from a black rockfish concanavalin A (Con A)/phorbol myristate acetate (PMA)-stimulated leucocyte cDNA library and named BrTPx1-1 and BrTPx1-2. As compared with other known TRx peptide sequences, the most conserved regions of both BrTRx1-1 and BrTRx1-2 peptides were found to be the redox-active site Trp-Cys-X-X-Cys (WCXXC). The TRx present in most species is a TRx1-2 protein with a Cys-Pro-Gly-Cys (CPGC) active site. However, in the larger 13 kDa BrTRx1-1 protein, a Cys-Pro-Pro-Cys (CPPC) active site was identified. Here, we report the identification of a new member of the TRx protein family from the teleost black rockfish, which defines a new subclass of 13-kDa TRx1-1 proteins. Phylogenetic analysis indicated that both BrTRx1-1 and BrTRx1-2 were grouped with other vertebrate TRx1 peptides. BrTRx1-1 expression was strongly induced in peripheral blood leucocytes (PBLs) 12-24 h following Con A/PMA stimulation, with peak expression at 24 h post-stimulation. BrTRx1-2 was induced in PBLs after stimulation with lipopolysaccharide (LPS), Con A/PMA, or poly I:C at 24 h. The BrTRx1-1 gene was predominantly expressed in the liver and gills, while BrTRx1-2 was expressed in PBLs and gills. After treatment with a high concentration (10 μg/mL) of rBrTRx1-1 or rBrTRx1-2, kidney leucocytes exhibited increased cell proliferation and viability under oxidative stress.     

Gonadal sex differentiation and effect of rearing temperature on sex ratio in black rockfish (Sebastes schlegeli)

Temperature-dependent sex determination has been demonstrated in some species of fish, and a high temperature during the period of sex differentiation typically produces a male-dominant population. This research investigated the gonadal sex differentiation and effect of rearing temperature on the sex ratio in larval black rockfish Sebastes schlegeli, which is a viviparous species. Two types of gonads were histologically distinguishable in fish 20 mm in total length (TL). The putative ovary started forming an ovarian cavity, while the putative testis was not clearly differentiated until 51 mm TL. In a temperature-controlled experiment, the proportions of females were 45% at 10°C, 46% at 14°C, 50% at 18°C, 63% at 22°C, and 83% (significantly different from 1:1 sex ratio) at 24°C. These results suggest that morphological sex differentiation in black rockfish occurs at approximately 20 mm in TL, and it is possible that high temperatures (24°C) induce not a male- but a female-dominant population in this species.     

Ontogenetic changes of habitat selection and thyroid hormone levels in black rockfish (Sebastes schlegelii) reared in captivity

This study examined the ontogenetic change in vertical distribution associated with algae and the thyroid hormone profiles of black rockfish (Sebastes schlegelii) under rearing conditions. Experimental observations on distribution were carried on black rockfish from the newly born larval stage to juveniles 75 days after birth (DAB). Position was categorized by vertical location [upper layer, mid layer and lower layer (LL)] and by association with artificial algae (floating algae, bottom algae and no association). Position of fish was observed four times a day, at 0400 (dawn), 1200 (noon), 1800 (dusk) and 2400 (midnight) hours. The majority of fish (>80%) reached transforming larval stage [17.8 ± 0.7 mm total length (TL)] at 25 DAB and juvenile stage (24.3 ± 0.6 mm TL) at 35 DAB. Newly born larvae were mainly distributed at surface and middle layers, the shift of vertical distribution to the LL occurred between 10 and 25 DAB, and over 98% of the individuals were distributed near the bottom after 35 DAB. Association behavior with algae was first observed from 20 to 30 DAB depending on the time of day. Percentage of fish associated with bottom algae increased from 25 to 40 DAB and reached 50–70% thereafter. Thyroid hormone (T₄) showed two surges at 30 and 50 DAB. The first surge corresponded to the transforming larval stage and the occurrence of association behavior with algae. The results indicate that pelagic larvae settle to the bottom layer before metamorphosis, and association behavior with algae appears at the transforming larval stage. A high T₄ concentration at 30 DAB indicates a close relationship with these morphological and behavioral developments.     

Geometric morphometrics reveals body shape differences between sympatric redfish Sebastes mentella, Sebastes fasdatus and their hybrids in the Gulf of St Lawrence

Significant body shape differences were observed between two commercially important redfish species Sebastes fasdatus and Sebastes mentella , in the Gulf of St Lawrence, first classified according to the variability at the MDH-A* locus, a diagnostic criterion for the two species in allopatry. The observed sexual dimorphism was probably related to the presence of gravid females in the sample. Sebastes mentella appeared to be more fusiform than S. fasdatus , a characteristic that may reflect the more pelagic behaviour of S. mentella . The body shape of their hybrids was closer to that of S. mentella . Similarities between hybrids and S. mentella were also observed for meristic characteristics and depth distribution. The implications of these similarities for introgression are discussed. Body shape variability of specimens of hybrid origin was greater than that of either parental species, with features ranging from S. mentella-like to S. fasciatus -like. The role of introgression in generating morphological variability is emphasized.     

Cryptic speciation and genetic structure of widely distributed brittle stars (Ophiuroidea) in Europe

Pérez‐Portela, R., Almada, V. & Turon, X. (2012). Cryptic speciation and genetic structure of widely distributed brittle stars (Ophiuroidea) in Europe. —Zoologica Scripta, 00, 000–000. The development of molecular techniques has led to the detection of numerous cases of cryptic speciation within widely distributed marine invertebrate species and important taxonomic revisions in all the major marine taxa. In this study, we analysed a controversial marine species complex in the genus Ophiothrix, a widespread taxon in European waters traditionally assigned to two nominal species, Ophiothrix fragilis and O. quinquemaculata. These species are important components of the rocky shores and deep marine benthos along the North Atlantic and Mediterranean littoral. Their status (including variants of both species) has remained contentious due to overlapping variability in morphological characters. In this study, we analysed the genetic and morphological differences of Ophiothrix lineages along the Atlantic and Mediterranean coasts. We also assessed population genetic structure in the Atlantic and Mediterranean basins by sequencing two mitochondrial genes, the 16S rRNA gene and COI gene, of 221 specimens from 13 locations. Phylogenetic analyses demonstrated the existence of two genetically distinct lineages, attributable to two different species although unrelated to previous taxonomic distinctions. Morphological differences could also be detected between these lineages. Samples from the Northeast Atlantic and one from the deep Mediterranean grouped within Lineage I, whereas Lineage II pooled together the southern Atlantic and rocky shallow Mediterranean samples. In the northern region of the Iberian Peninsula and at a deep locality in the Mediterranean, both lineages overlap. Speciation processes likely happened during the Mio–Pliocene transition (about 4.8–7.5 million years ago), when marine‐level oscillations led to the blockage of major marine corridors in Europe and promoted genetic isolation by vicariance. Secondary contact between lineages following sea‐level increases and recolonization during the refilling of the Mediterranean after the Miocene salinity crisis could explain the present‐day distribution of genetic variability. No barriers to gene flow along the Atlanto‐Mediterranean area were detected for Lineage II, and the lack of genetic structure could be caused by a mixture of several factors, such as wide dispersal potential, recent demographic expansion and large population size.     

Prevalence and spatial distribution of intraerythrocytic parasite(s) in Puget Sound rockfish (Sebastes emphaeus) from the San Juan Archipelago, Washington (USA)

Two morphologically distinct forms of an intraerythrocytic parasite(s) were detected by microscopic observation of Giemsa-stained blood films in 45.7% of 119 rockfish (Sebastes emphaeus) from the San Juan Archipelago (Washington State, U.S.A.). Infection prevalence for both forms was 53% in males, 44% in females, and 33% in fish of undetermined gender. A binucleate "ring-stage" was present at all 4 geographic sites, with a mean prevalence of 45.7%, while mean prevalence of a larger gamont-like form from the same sites was 5.1%. The relationship of the 2 forms to each other could not be determined. Neither schizogony nor binary fission was evident in any of the infected erythrocytes and the parasites contained no obvious pigment. The possibility of the 2 morphologic forms being 2 distinct species is supported by the observation that no difference in parasitemia was seen in the binucleate form among sites (1.6-1.9%), while parasitemia of the gamont-like form varied significantly among sites, ranging from a high of 4% to a low of 0.1%. Taxonomic status of either form could not be determined at this time based on limited existing morphologic data.     

Depth and habitat distributions of three species of rockfish (Sebastes) in British Columbia: observations from the submersible PISCES IV

Synopsis I describe a technique to quantify spatial distribution patterns of deep reef-fishes, and apply this technique to inshore rockfish (Sebastes) communities in the Strait of Georgia, British Columbia, Canada. Observations were made along vertical transects between 21–140 m using the submersible PISCES IV. A total of 31 transects were completed at 14 sites during 16 submersible dives. S. elongatus, S. maliger and S. ruberrimus were the dominant rockfish species that were observed. S. elongatus and S. ruberrimus had similar depth distributions, but tended to segregate by habitat type. S. elongatus was most abundant on mud and cobble substrates that interspersed rocky areas. S. maliger and S. ruberrimus were both abundant in complex rock habitats, but tended to segregate by depth. For all three species there was an increase in size with depth. Hence, habitat type and depth were important influences on distribution patterns of this species group.     

Purification and characterization of an antibacterial protein in the skin secretion of rockfish Sebastes schlegeli

An antibacterial protein in the skin secretion of rockfish (Sebastes schlegeli) was purified by lectin affinity chromatography on Con A-Sepharose and gel filtration on TSKgel G3000SW. The antibacterial protein featured the high molecular mass and selective action against Gram-negative bacteria. The molecular mass of the protein was estimated to be approximately 150 kDa in gel filtration and approximately 75 kDa by SDS-PAGE, suggesting that it is dimeric. The antibacterial principle was an acidic glycoprotein with pI 4.5, 3.4% reducing sugar and 2.8% amino sugar. Its sugar chains had N-type (high mannose-type) oligosaccharide and sialic acid components. It inhibited strongly the growth of Aeromonas salmonicida, Photobacterium damselae and Shewanella putrefaciens with a minimum inhibitory concentration (MIC) of approximately 3 microg/ml, and moderately the growth of Vibrio parahaemolyticus and A. hydrophila with a MIC of 12.5 microg/ml and 25 microg/ml, respectively. The values of the minimum bactericidal concentration were almost equivalent to those of MIC. The potent sensitivity against virulent pathogens such as A. hydrophila, A. salmonicida and P. damselae may contribute considerably to the innate host defense mechanism to combat microbes on the mucosal surfaces of the rockfish.