The redfish species Sebastes viviparus, Sebastes marinus and Sebastes mentella have different composition of their tissue fatty acids

The fatty acid profile in the tissue of heart, gill, skull- and otolith-oil of the three redfish species, Sebastes viviparus, S. marinus and S. mentella was determined by a chemometric method, consisting of methanolysis of samples of the tissues and of the oils and gas chromatography of the resulting fatty acid methyl esters. The analytical data were treated by multivariate statistics comprising principal component analysis (PCA) and soft independent modeling of class analogy (SIMCA). Although the differences in fatty acid composition among the two tissues and two oils were the dominating features of the data, the three species had significantly different fatty acid profiles within each tissue. Variation among the individuals was considerable. The fatty acid profiles appeared to be species specific. The mutual relationship between S. marinus and S. mentella is closer than the relationship between either of them and S. viviparus. A comparison with a corresponding investigation on the same three species from another location indicates that the observed differences do not seem to be affected by biotic or abiotic factors.     

Discrimination of Sebastes viviparus, Sebastes marinus and Sebastes mentella from Faroe Islands by chemometry of the fatty acid profile in heart and gill tissues and in the skull oil

The composition of fatty acids in the tissue of heart, gill and skull oil of the three redfish species, Sebastes viviparus, Sebastes marinus and Sebastes mentella was determined by a chemometric method. The method consists of methanolysis of samples of the tissues and of the oils, gas chromatography of the resulting fatty acid methyl esters and multivariate statistical treatment, by principal component analysis, of the analytical data. Although the differences in fatty acid composition among the three tissues were the dominating features of the data, the three species had significantly different fatty acid profiles within each tissue, even though variation among the individuals was considerable. The fatty acid profiles appear to be species specific. The mutual relationship between S. marinus and S. mentella is closer than the relationship between either of them and S. viviparus.     

Growth Properties in Redfishes of the Genus Sebastes on the Flemish Cap Bank

Journal of Ichthyology - This article analyzes the dynamics of the linear growth rate for three redfish species of the genus Sebastes on the Flemish Cap bank: beaked redfish S. mentella, golden...     

Evidence for broadscale introgressive hybridization between two redfish (genus Sebastes) in the North-west Atlantic: a rare marine example

The evolutionary importance of introgressive hybridization has long been recognized by plant evolutionists, and there is now a growing recognition for its potential role in animals as well. Detailed empirical investigations of this evolutionary process, however, are still lacking in many animal groups, particularly in the marine environment. Using integrated microsatellite DNA data (eight loci analysed over 803 individuals representing 17 sampling locations) and multivariate statistical procedures (principal component, factorial correspondence and admixture proportion analyses), we: (i) provide a detailed dissection of the dynamics of introgressive hybridization between Sebastes fasciatus and S. mentella, two economically important redfishes from the North-west Atlantic; and (ii) infer the factors potentially involved in the maintenance of the hybrid zone observed in the gulf of St. Lawrence and south of Newfoundland. This study provided one of the rare examples of extensive introgressive hybridization in the ocean, and highlighted the predominant role of this process in shaping the extent of genetic diversity, interspecific differences and population structuring among redfishes from the North-west Atlantic. The extensive (average rate of introgression = 15%) but geographically circumscribed and asymmetrical pattern of introgressive hybridization, the sympatric persistence of two reproductively isolated introgressed groups, the differential patterns of linkage disequilibrium among samples, and the maintenance of genetic integrity of both species outside the defined zone of introgression despite high potential for gene flow, all implicated selection in promoting and maintaining the observed pattern of introgression.     

Genetic variation of Sebastes viviparus Krøyer in the North Atlantic

As part of a more extensive study on the inter- and intraspecific genetic variation of redfish, genus Sebastes , a total sample of 593 individuals of the species Sebastes viviparus were collected from several locations in Norwegian waters and off the south-west coast of Iceland. Haemoglobin and five polymorphic enzymes were analysed. A new haemoglobin polymorphism was observed, and unique alleles were found in Icelandic and Norwegian samples. The results of the enzyme analyses were largely consistent with previous results, but interpopulation variation was observed in the frequencies of IDHP * and Hb * alleles. S. viviparus displayed higher similarity with S. fasciatus from the West Atlantic than with the other Sebastes species.     

Extensive hybridization and associated geographic trends between two rockfishes Sebastes vulpes and S. zonatus (Teleostei: Scorpaeniformes: Sebastidae)

Interspecific hybridization is an important evolutionary process, which has significant influence on the diversity within and between participating taxa. Although interspecific hybridization in terrestrial and freshwater organisms has been subjected to many detailed studies, studies in marine realm have been limited in terms of both numbers and detail. In this study, the potential for interspecific hybridization between two rockfishes, Sebastes vulpes and S. zonatus, occurring in the western North Pacific, was assessed on the basis of 177 specimens collected from three sampling localities within the main geographic distribution of both species, and analysed using a combination of amplified fragment length polymorphisms (AFLP), mitochondrial DNA (mtDNA) markers and morphometric characters. Bayesian‐based individual genetic assignment based on 364 AFLP loci detected a total of 63 (35.6%) hybrid specimens in the data set, the presence of interspecific hybrids also being rigorously supported by mtDNA analysis using partial sequences from the control region and morphological analysis based on 31 morphometric characters. Hybrids from all three localities were found, showing a common pattern of biased introgression across the localities whereby hybrids were more closely related to S. zonatus than to S. vulpes. Apart from this common pattern, rates of hybridization varied considerably among the localities, being greater in the northern localities. Variations in the local rates of hybridization were associated with variations in habitat segregation and thermal regime, implying that vertical water temperature regimes determined the extent of habitat segregation of the two species and, accordingly, the opportunity for hybridization.     

The incomplete history of mitochondrial lineages between two rockfishes, Sebastes longispinis and Sebastes hubbsi (Scorpaeniformes: Scorpaenidae)

The genetic divergence between two closely related rockfishes, Sebastes longispinis and Sebastes hubbsi, was inferred from both mitochondrial DNA (mtDNA) sequence variations and amplified fragment length polymorphism (AFLP) markers. The two species were placed into two distinct clades in a neighbour-joining tree based on the AFLP data, clearly indicating that they represented separate species. Although this evidence, together with a previous morphological study, revealed clear differences between the two species, no obvious clustering of haplotypes by species was detected in the minimum spanning network inferred from sequence variations in the mtDNA control region (c. 500 base pairs). In fact, the significant Φ(ST) estimates indicated only a restriction of gene flow between the two species. Uncorrected pairwise sequence differences in mtDNA between two species were small (1·8% at maximum, on the lower end of the range of control region divergence between previously studied sister species pairs), suggesting their speciation event as having been fairly recent. The incongruent results of AFLP and mtDNA phylogenies suggested incomplete lineage sorting and introgression of mtDNA in the course of the evolution of the two species. Differences in their main distributional ranges and the small level of sequence divergence in mtDNA suggests that speciation and dispersal may have been associated with glacio-eustatic sea level fluctuations between the Japanese Archipelago and the Korean Peninsula during the past 0·4 million years.     

Pigment variability in larval Sebastes jordani off central California

Atypical pigment was observed in pre‐flexion, flexion and post‐flexion larval Sebastes collected off central California in 1991 and 1992 that otherwise resembled Sebastes jordani . Atypical pigment occurred on the axillary region at the base of the pectoral fin (most prominent on the inner edge of the pectoral fin base adjacent to the gut), on the median and distal regions of the pectoral fin and on the median and distal regions of the pelvic fin. In addition, lower and upper jaw pigment was observed at a much smaller size in these specimens than previously described in the literature. Identifications of these atypical specimens as S. jordani were confirmed using meristic and otolith characters as well as mitochondrial DNA sequence data. The ontogenetic variability of S. jordani is described. Specimens collected north of Point Conception were more pigmented than larval S. jordani described in the literature (collected predominately south of Point Conception), suggesting geographic variation in pigment development during the larval stage.     

Comparative morphology of pre‐extrusion larvae,Sebastes mentella and Sebastes norvegicus (Pisces: Sebastidae) in Icelandic waters

This study evaluated potential differences in morphology of unextruded larvae from Sebastes mentella and Sebastes norvegicus in Icelandic waters. Fifty‐four larvae of each species were measured, and 18 measurements were recorded for each specimen (morphometric, meristic and pigmentation patterns). Pre‐extrusion larvae of S. norvegicus were longer than those of S. mentella. Additionally, there were significant differences in morphometric, meristic and pigmentation characters between pre‐extrusion larvae of these species. Pigmentation of S. mentella differed from that of S. norvegicus in several aspects. Dorsal and ventral body pigmentation tended to begin more posteriorly in S. mentella, therefore, the overall length of these pigmented areas tended to be longer in S. norvegicus.     

Parasites and Maturation Rate as Indicators of Population Structure in the Beaked Redfish Sebastes mentella (Sebastidae)

Journal of Ichthyology - The direction of phylogenesis of beaked redfish Sebastes mentella is considered based on a comparative analysis of the parasite fauna and maturation rate of individuals in...     

Comparative study on the surface ultrastructures of fertilized eggs of three Sebastes species

Fertilized eggs of Sebastes schlegelii, Sebastes pachycephalus and Sebastes hubbsi are morphologically similar under stereomicroscope. However, under the scanning electron microscope, significant differences in the ultrastructures of the egg surface among the three species were observed, and herein, a taxonomic key was proposed for future applications. A clustering analysis based on the ultrastructures of the egg surface and the diameter of the oil globule suggested that among the three species, S. hubbsi and S. pachycephalus were more genetically similar, while S. schlegelii had diverged earlier. The results agree with the conclusions drawn from morphological and molecular analyses on adult samples of the same species.     

Ecological and Population Features of Beaked Redfish Sebastes mentella (Sebastidae) in the Northwest Atlantic Based on the Analysis of Its Parasite Fauna

Journal of Ichthyology - The results of studying the composition and features of the ecology, zoogeography, and formation of the parasite fauna of beaked redfish Sebastes mentella in the waters of...     

When Anthropogenic River Disturbance Decreases Hybridisation between Non-Native and Endemic Cyprinids and Drives an Ecomorphological Displacement towards Juvenile State in Both Species

Understanding the impact of non-native species on native species is a major challenge in molecular ecology, particularly for genetically compatible fish species. Invasions are generally difficult to study because their effects may be confused with those of environmental or human disturbances. Colonized ecosystems are differently impacted by human activities, resulting in diverse responses and interactions between native and non-native species. We studied the dynamics between two Cyprinids species (invasive Chondrostoma nasus and endemic Parachondrostoma toxostoma) and their hybrids in 16 populations (from allopatric to sympatric situations and from little to highly fragmented areas) corresponding to 2,256 specimens. Each specimen was assigned to a particular species or to a hybrid pool using molecular identification (cytochrome b and 41 microsatellites). We carried out an ecomorphological analysis based on size, age, body shape, and diet (gut vacuity and molecular fecal contents). Our results contradicted our initial assumptions on the pattern of invasion and the rate of introgression. There was no sign of underperformance for the endemic species in areas where hybridisation occurred. In the unfragmented zone, the introduced species was found mostly downstream, with body shapes similar to those in allopatric populations while both species were found to be more insectivorous than the reference populations. However, high level of hybridisation was detected, suggesting interactions between the two species during spawning and/or the existence of hybrid swarm. In the disturbed zone, introgression was less frequent and slender body shape was associated with diatomivorous behaviour, smaller size (juvenile characteristics) and greater gut vacuity. Results suggested that habitat degradation induced similar ecomorphological trait changes in the two species and their hybrids (i.e. a transition towards a pedomorphic state) where the invasive species is more affected than the native species. Therefore, this study reveals a diversity of relationships between two genetically compatible species and emphasizes constraints on the invasion process in disturbed areas.     

Taxonomic review of the Sebastes vulpes complex (Scorpaenoidei: Sebastidae)

Ichthyological Research - A taxonomic review of the Sebastes vulpes complex (S. vulpes, S. zonatus and S. ijimae) established the existence of two valid species, Sebastes vulpes Döderlein in...     

Temporal variation and feeding ecology of juvenile Sebastes in rocky intertidal tidepools of northern California, with emphasis on Sebastes melanops Girard

This study examined the seasonal use of rocky intertidal areas by young-of-the-year (YOY) Sebastes spp. at three locations in northern California, 2003 to 2005. Six species of Sebastes were noted during the study with black rockfish Sebastes melanops comprising >99% of the total number sampled. Sebastes melanops were noted in rocky intertidal areas from May to August with peak abundances occurring in May or June. Variation in recruitment and feeding was evident among years. Diet analysis, using the index of relative importance (% I _RI) and the modified index (% I _M), showed that YOY S. melanops and Sebastes mystinus consumed a variety of prey items with harpacticoid copepods and gammaridean amphipods being the dominant prey categories. The rocky intertidal appears to serve as an important habitat for YOY S. melanops in northern California.     

Genetic and morphological divergence within the Sebastes pachycephalus complex (Scorpaeniformes: Scorpaenidae)

Genetic and morphological divergence among the four subspecies in the Sebastes pachycephalus complex (S. pachycephalus pachycephalus, S. p. nigricans, S. p. nudus and S. p. chalcogrammus) was clarified. Principal coordinate analysis (PCoA) based on AFLP clearly divided 55 specimens of the complex into two groups, the S. p. pachycephalus?CS. p. nigricans group (P-Ni group) and the S. p. nudus?CS. p. chalcogrammus group (Nu-C group), although three specimens occupied intermediate positions. The minimum spanning network (MSN) based on partial sequences of the mitochondrial control region (mtCR) failed to separate either the P-Ni and Nu-C groups or the four subspecies into distinct clades, although restricted gene flow and genetic differentiation between the former were indicated by the F _ST estimation. Differences in morphological characters, including counts of pectoral fin rays and counts of dorsal fin spines lacking basal scales, were also evident between the two groups. However, little or no genetic or morphological difference was found between the two subspecies within each group. It was concluded that the P-Ni and Nu-C groups of the S. pachycephalus complex actually represent two different species, which is further supported by their sympatric distribution. Differences in dorsal body coloration and the presence or absence of brown spots on the ventral surface, which were formerly used to discriminate between four ??subspecies,?? may simply represent intraspecific variation. The three specimens occupying intermediate positions in the AFLP PCoA also occupied equivocal positions between the two species in the principal component analysis (PCA) based on morphometric characters, suggesting that they were hybrids between the two species. The star-shaped MSN of mtCR, which lacks distinct clades representing the two species, may be due to not only interspecific hybridization but also the sharing of ancestral haplotypes.     

Taxonomic review of the <Emphasis Type="Italic">Sebastes inermis</Emphasis> species complex (Scorpaeniformes: Scorpaenidae)

A taxonomic review of three color morphotypes of the Sebastes inermis species complex established the existence of three valid species, viz. S. inermis, S. ventricosus, and S. cheni. The complex is defined by having two sharp lachrymal spines, the head weakly armed with nasal, preocular, supraocular and parietal spines, and the caudal fin not distinctly emarginated. Sebastes inermis, known from southern Hokkaido southward to Kyushu, Japan, and the southern part of the Korean Peninsula, is characterized as follows: body dark red or light brown dorsally and laterally when fresh, pectoral fin extending beyond level of anus when depressed, pectoral-fin rays 15, anal-fin rays 7, pored lateral line scales 36–44 and gill rakers 31–37. Sebastes ventricosus, known from Iwate and Ishikawa Prefecture southward to Kyushu, Japan, and the southern part of the Korean Peninsula, is characterized as follows: body somewhat greenish-black dorsally and dark silver ventrally when fresh, pectoral-fin rays 16, anal-fin rays 7–8, pored lateral line scales 43–49, and gill rakers 35–39. Sebastes cheni, known from Iwate and Akita Pref. southward to Kyushu, Japan, and the southern part of the Korean Peninsula, is characterized as follows: body dark golden-brown dorsally and laterally when fresh, pelvic fin extending beyond anus when depressed, pectoral-fin rays 17, anal-fin rays 8, pored lateral line scales 37–46 and gill rakers 32–37. In the genetic analysis, the presence or absence of two AFLP fragments was completely fixed among the three species. Sebastes tokionis and S. guentheri are regarded as junior synonyms of S. inermis and S. ventricosus, respectively. A lectotype is designated for S. cheni, and a key to the three species of the S. inermis species complex provided.     

Genetic structure of hybrid zones between Silene latifolia and Silene dioica (Caryophyllaceae): evidence for introgressive hybridization

Natural hybrid zones provide a valuable tool to study introgressive hybridization, because they can contain a wide variety of genotypes that result from many generations of recombination. Here we used molecular markers and morphological variation to describe the structure of two natural hybrid zones between Silene latifolia and Silene dioica in the Swiss Alps. Populations in both hybrid zones consisted of few intermediate hybrids and were dominated by backcross hybrids. The latter were also found in the parental populations at the margins of the hybrid zones. Out of 209 amplified fragment length polymorphism (AFLP) markers scored in 390 individuals, only 7 (3.3%) were species specific. These results indicate that introgression between S. dioica and S. latifolia is extensive, and that hybrid zones act as bridges to gene flow between these two species. Analysis of linkage disequilibrium identified few populations in which hybridization is ongoing, whereas in most populations linkage disequilibrium has eroded. Where hybridization is ongoing, strong changes in species-specific marker frequencies and morphological traits were observed. Plastid introgression into the hybrid zone was found to be bidirectional, but only the S. latifolia plastid haplotype was found in a nuclear S. dioica background. This unidirectional plastid introgression from S. latifolia into S. dioica is most likely due to pollen-flow from S. dioica onto S. latifolia, and results in plastid capture. Comparisons between the molecular and the morphological hybrid indices revealed that morphology in this study system is useful for identifying hybrids, but not for detailed analysis of hybrid zone structure.     

Relative warp analysis of skull shape across the hybrid zone of the house mouse (Mus musculus) in Denmark.

The changes in skull shape that occur in the hybrid zone between the two European subspecies of the house mouse ( Mus musculus musculus and M. m. domesticus ) were studied by relative warp analyses. Landmarks observed on the ventral view of the skulls of 269 mice sampled in 18 localities in Denmark were analysed. Each population was also characterized by a hybrid index estimated from allozymic data. Although no clear pattern of within-population variability of shape could be established across the hybrid zone, the shape changes among the 18 populations were found to be correlated with the allozymic introgression but not with geographical location. Finally, the cline obtained for skull shape seems to be steeper than that corresponding to the average allozyme hybrid index which suggests that skull development could be slightly perturbed in hybrids.