The complete mitochondrial genome of the Senegal sole, Solea senegalensis Kaup. Comparative analysis of tandem repeats in the control region among soles.

The complete nucleotide sequence of the mitochondrial genome for the Senegal sole Solea senegalensis Kaup was determined. The mitochondrial DNA was 16,659 base pairs (bp) in length. Sequence features of the 13 protein-coding genes, two ribosomal RNAs and 22 transfer RNAs are described. The non-coding control region (1017 bp) was compared with those of the closely related soles Solea solea and Solea lascaris. The typical conservative blocks were identified. A cluster of 42 and 22 tandemly arrayed repeats was detected near the 3' end of control region in S. solea and S. lascaris, respectively. On the contrary, only two (93.8% of haplotypes) or three copies (6.2%) of an 8-bp repeated sequence motif was found in S. senegalensis. Phylogenetic analysis showed that 7 out of 9 of haplotypes bearing three copies grouped in a separate cluster. Possible mechanisms influencing the evolution of control region among soles are discussed.     

Comparative feeding ecology of sympatric Solea solea and S. senegalensis, within the nursery areas of the Tagus estuary, Portugal

Among the stomach contents of 609 individuals of Solea solea and 1104 of S. senegalensis the main food items of S. solea were Corophium spp. and Hediste diversicolor, and of S. senegalensis were Corophium spp., H. diversicolor and Scrobicularia plana. For both species, the importance of larger prey items in the diet, namely H. diversicolor and Crangon crangon, increased with fish size. Feeding activity of S. solea and S. senegalensis increased in spring and summer. Short-term variations were particularly related to the tidal cycle and the two species fed in intertidal areas. Dietary dierences between the two nursery areas reflected prey availability mainly. Although intra- and interspecific length classes overlapped in diet, potential interspecific competition was probably minimized by a dierential habitat use pattern.     

Differential Use of Nursery Areas Within the Tagus Estuary by Sympatric Soles, Solea solea and Solea senegalensis

The spatio-temporal pattern of estuarine use by both Solea solea and Solea senegalensis was investigated between April 1995 and November 1996 by beam trawl surveys. Spatial and seasonal distribution and abundance were different for each species. The highest densities of S. solea were recorded in deeper, warmer, low salinity areas and where the sediment consisted of a high proportion of fine sand and presented a high abundance of amphipods. The 0-group individuals of this species first occurred on the nursery ground in April. Numbers peaked in June and July, and from October to April abundance was low. S. senegalensis had a wider distribution and its abundance was related to food availability. The 0-group individuals of this species occurred in the nursery areas later than S. solea, from June to August.     

Comparative study of sexual cycles, oogenesis and spawning of two Soleidae, Solea lascaris (Risso, 1810) and Solea impar (Bennet, 1831), on the western coast of Brittany

Two sand sole species, Solea lascaris and Solea impar , are common on the western coast of Brittany, France. Their reproduction (oogenesis and spawning) has been studied by following the gonadosomatic index, histological changes in ovary development, and oocyte diameter distribution. Both species have a prolonged spawning season, from spring to late summer. Each mature female breeds twice during the spawning season: in May and July for 5. lascaris , and in early June and July for 5. impar. Throughout the spawning season, several oocyte batches undergo vitellogenesis and there is a continuous recruitment of immature or primary oocytes into vitellogenesis. The two species are thus serial synchronous spawners. This, together with oocyte atresia late in the season (especially noticeable in S. impar ) makes fecundity estimation difficult.     

Molecular systematics of the Atlanto-Mediterranean Solea species

Within the genus Solea , four sister lineages have been evolved that actually correspond to the species S. vulgaris, S. senegalensis, S. kleini and S. lascaris . The existence of S. aegyptiaca and S. impar is not supported and these species can be synonymized under S. vulgaris and S. lascaris , respectively. This pattern of taxonomy agrees fully with that proposed by Ben-Tuvia (1990; Journal of Fish Biology 36, 947–960) based on morphological features. In addition, mtDNA data contradict the widely accepted relatedness between S. kleini and S. lascaris based on the shared enlarged forenostril on the blind side. A sample of soles clearly related to S. senegalensis was caught in the Gulf of Taranto (Ionian Sea), representing the most western finding of this species in the Mediterranean Sea.     

Growth variability of juvenile soles Solea solea and Solea senegalensis, and comparison with RNA : DNA ratios in the Tagus estuary, Portugal

Growth variability and condition of juvenile soles Solea solea and Solea senegalensis , were assessed through RNA : DNA estimates and compared to absolute growth rates. Higher mean cohort RNA : DNA ratios were observed for cohort I at the beginning of estuarine occurrence for both species (4·42 and 4·87, for S. solea and S. senegalensis respectively). Despite different estuarine colonization habits, no significant differences were observed between RNA : DNA monthly variation for both sole species within the same year ( P  > 0·05 for 2003 and 2004). Juvenile S. senegalensis showed significant differences between RNA : DNA ratios obtained for the two nursery areas ( P  < 0·001). The decrease of seasonal growth rates with fish age was similar to seasonal variation of mean RNA : DNA values. Thus the RNA : DNA pattern of juvenile S. solea and S. senegalensis reflected growth and estuarine colonization patterns.     

Effect of temperature and salinity on the gastric evacuation of juvenile sole Solea solea and Solea senegalensis

The juveniles of Senegal sole, Solea senegalensis, Kaup 1858, and common sole, Solea solea (Linnaeus 1758) concentrate in estuarine and coastal nurseries of widely differing temperatures and salinities. Yet, little is known about the effect of these physiologically important variables on the gastric evacuation rates of these species. Gastric evacuation experiments were performed on juveniles of S. senegalensis and S. solea. Three temperatures were tested, 26, 20 and 14°C at a salinity of 35‰. A low salinity experiment was also carried out at 15‰, at 26°C. Experimental conditions intended to reflect conditions in estuarine and coastal nurseries where juveniles of these species spend their first years of life. The relation between stomach contents and time was best described by exponential regression models for both species. An analysis of covariance (ancova ) was performed in order to test differences in evacuation rate due to temperature and salinity (slope of evacuation time against stomach contents) for each species. While increasing temperature increased evacuation rates in both species (although not at 26°C in S. solea), the effect of low salinity differed among species, leading to a decrease in gastric evacuation rate in that of S. senegalensis and an increase in S. solea. Differences in gastric evacuation rate between species were related to its metabolic optimums and to its distribution in the nursery area where fish were captured. Implications for the habitat use of estuarine and coastal nurseries are discussed.     

圆斑星鲽及相关种类线粒体DNA控制区结构分析

采用PCR产物直接测序法测定了圆斑星鲽(Verasper variegatus)的24个个体的线粒体控制区(Control region)核苷酸全序列, 并进行了结构分析。结果表明, 圆斑星鲽线粒体控制区核苷酸全序列具有长度多态性, 得到4种长度单元型, 主要表现为控制区中的串联重复序列的长度不同。对鲽形目鱼类如鲽科的条斑星鲽(Verasper moseri)、黄盖鲽(Limanda feruginea)、马舌鲽 (Reinhardtius hippoglossoides), 美洲拟庸鲽(Heppoglossoides platessoides )和鲆科的牙鲆(Paralichthys olivaceus)以及鳎科的欧洲鳎(Solea solea)、塞内加尔鳎(S. senegalensis)和沙鳎(S. lascari)的控制区的比较研究发现, 鲽形目鱼类的线粒体控制区均存在相似的结构, 即线粒体控制区可分为终止相关序列区(ETAS)、中央保守区(包括CSB-A、CSB-B、CSB-C、CSB-D、CSB-E、CSB-F)以及保守序列区(CSB1、CSB2、CSB3)和重复序列区(Repeat region)4个区域。通过与脊椎动物各个纲线粒体控制区序列的比较分析, 发现只有鲽形目(包括鲆、鲽类和鳎类)鱼类和两栖纲的无尾类在CSB-3之后存在相似的串联重复序列。     

Comparison of Solea solea macroparasites between two nursery-continental shelf systems in the Bay of Biscay and the Portuguese coast

Digenean metacercariae of 0 year group common sole Solea solea ( n = 70) were more abundant in the embayed nursery of the Pertuis Charentais than in the Tagus estuary nursery. Macroparasite assemblages of adult sole ( n = 119) displayed only one species in common between the Bay of Biscay and the Portuguese coast continental shelves. These data highlighted the potential use of macroparasites as biological tags in various aspects of common sole ecology.     

Comparison between the life cycles of two Soleidae, the common sole, Solea solea, and the thickback sole, Microchirus variegatus, in the Bay of Biscay (France)

The life history of two Soleidae, the common sole, Solea solea, and the thickback sole, Microchirus variegatus, were compared in the Bay of Biscay in an attempt to set out factors which could explain settlement styles known to be different between juveniles of each species. Common sole juveniles had been shown to depend on coastal and estuarine nurseries, and the thickback sole to develop in open-sea nurseries, although the spawning grounds and spawning season of both species overlapped (offshore and at springtime, respectively). For this study, data on adult, juvenile and larva distributions were obtained from cruises carried out in the Bay of Biscay during the last decade. In addition, growth rate of larvae and planktonic interval duration, estimated by means of otolith increment analysis, were compared, as well as literature-derived information on behaviour of larvae. By comparing larval features, it appeared that thickback sole did not obtain the advantage of a slightly longer pelagic life span for an increased dispersal, due to an early shift to benthic behaviour. Other evidence was given by more specifically stated distributions that the further and deeper offshore spawning of M. variegatus, compared to S. solea, was a likely key-factor of the juvenile settlement process. This could explain why the thickback sole, contrary to the common sole, never reach coastal areas and thus settle offshore, in waters deeper than 30 m.     

Interspecific variations of otolith chemistry in estuarine fish nurseries

Otolith chemical composition differed between juveniles of five fish species ( Solea solea , Solea senegalensis , Platichthys flesus , Diplodus vulgaris and Dicentrarchus labrax ) in nursery areas of six estuaries along the Portuguese coast (Douro, Ria de Aveiro, Mondego, Tejo, Sado and Mira). Spatially consistent patterns in the concentration of some elements were responsible for differences between species. Discrimination of estuaries using data from all species simultaneously averaged 44·7% of correctly classified cases, whilst discrimination of species averaged 76·2%. Moreover, species-related patterns in otolith fingerprints were highlighted when comparing species for each estuarine nursery area, with intra estuarine species discrimination averages ranging from 86·2 to 100·0%. Similarities in the otolith elemental fingerprints were larger between species with close phylogeny and ecology, particularly between flatfish and perciform species. In addition to the differences in physiological regulation of species, specific microhabitat use in a common environment was suggested as a relevant factor for the differentiation of otolith chemistry among species occurring in the same locations. Despite positive results in specific estuaries, variation in otolith composition limited the use of species as proxies to classify others to their system of origin.     

Feeding ecology of juvenile flatfishes of the surf zone of a sandy beach

Prey items of 0- and 1-group plaice Pleuronectes platessa , sole Solea solea , brill Scophthalmus rhombus , turbot S. maximus and dab Limanda limanda of the surf zone of a Belgian sandy beach, included hyperbenthic (e.g. mysids), endobenthic (e.g. polychaetes) and epibenthic (e.g. shrimps) species. Little dietary overlap was observed. If diet overlap did occur, it mainly involved prey species that are dominant in the surf zone of Belgian beaches, such as shrimps and mysids. These results suggest an opportunistic utilization by flatfish of the available food resources in surf zone ecosystems. Also, two strategically different feeding habits could be distinguished between the five flatfish species. Turbot and brill mainly fed on large, highly mobile prey (e.g. fish, mysids) and had a rather narrow prey spectrum, whereas plaice, dab and sole ate more benthic prey (e.g. polychaetes) and had a broader prey spectrum.     

Changes in the Tagus nursery function for commercial fish species: some perspectives for management

The Tagus estuary has long been subjected to several human activities and uses. Changes in the estuarine fish community were evaluated based on beam trawl surveys in 1978–1980 and 1994–1996. There was a decrease of abundance of many species that use the Tagus as a nursery, namely bib (Trisopterus luscus), five bearded rockling (Ciliata mustela), tub gurnard (Trigla lucerna), and flounder (Platichthys flesus), possibly due to reduction of the water quality. In 1994–1996, only sea bass (Dicentrarchus labrax), sole (Solea solea) and Solea senegalensis Kaup, 1858, were found within the nursery grounds, showing an irregular pattern of abundance. Condition and vacuity index were highly variable. The major problems affecting the fish community, namely pollution, fishery regulation and waterflow regulation, are discussed in relation to the management and conservation of this estuarine system.     

Development of the bony skull in common sole: brief survey of morpho-functional aspects of ossification sequence

The postembryonic development of the bony cephalic skeleton in the common sole Solea solea , observed from hatching to the juvenile stage or postmetamorphic larva, appears to follow a similar chronological order to that observed in other Pleuronectiformes and Perciformes and the sequence in bone formation is a response to functional demands. At hatching, S. solea has no bony structure. On day 4, only the outlines of maxillaries and opercular bones are visible. On day 6, a thin parasphenoid appears between the orbits and isolates the braincase from the buccal cavity making food ingestion possible without any impact on the brain. On day 8, the dentaries form and two small preopercular bones appear on each side of the head. On day 9, at weaning from the yolk sac, branchial arches support the gill filaments (used for respiration and trapping phytoplankton which pass through the open mouth). On day 10, the premaxillaries develop in front of the maxillaries. The superimposing of the maxillaries and the premaxillaries is a typical feature of species possessing an acanthopterygian protractile mouth at the adult stage. On day 12, the frontals develop above the orbits and the set of opercular bones is complete. On day 18, the migration of the left eye begins. On day 20, the left eye has moved to the median crest of the head. On day 23, both eyes are located on the same side. On day 26, the braincase is formed by a basioccipital, exoccipitals, pterotics, sphenotics and a supraoccipital. On day 50, new structures have appeared, others have developed and have undergone an extensive remodeling due to metamorphosis.     

Coupling of heart rate and locomotor activity in sole, Solea solea (L.), and bass, Dicentrarchus labrax (L.), in their natural environment by using ultrasonic telemetry

Field measurements of distance moved and heart rate in sole, Solea solea (L.) and bass, Dicentrarchus labrax (L.) using ultrasonic telemetry revealed two different strategies. Heart rate in the sole increases during activity, accurately reflecting fluctuation in metabolic rate and so can be used as a measure of metabolic rate in the field. In contrast, the relatively stable value of the heart rate in bass during the whole tracking period whatever the activity level suggests that in this species heart rate in the field cannot be associated with metabolic rate determination.     

Isolation of mycobacteria from frozen fish destined for human consumption

Mycobacteria were isolated from defrost water and tissue of sole (Solea solea), hake (Merluccius merluccius), cod (Gadus morhua), ling (Genypterus blacodes), and monkfish (Lophius piscatorius) on L?wenstein-Jensen medium after incubation at different temperatures. Samples of frozen fish were obtained under sterile conditions inside a refrigeration chamber (-18 to -22 degrees C) in a wholesale market from which these products are distributed to shops for retail sale and human consumption.     

Biosystematics and genetic relationships of Solea aegyptiaca and S. senegalensis

The isoenzymes from seven populations of Solea senegalensis or aegyptiaca were compared et 24–30 loci, six of which display significant differences in their allelic frequencies. In addition, these populations were compared to six other Soleidae species, namely Solea vulgaris, S. impar, S. lascaris, S. lutea, Michrochirus azevia, and M. variegatus. It was shown that S. senegalensis and S. aegyptiaca can be separated into two distinct genetic groups. Their high genetic similarity in comparison with the other species of Soleidae studied suggests that they have a common origin. The systematic status (species or semispecies) of these taxa could not, however, be elucidated. The high degree of genetic polymorphism observed in the regions where the two taxe are found together suggests that there still is some gene flow between them. However, this could be due to selection.     

The rate of development and longevity of the monogenean skin parasite Entobdella soleae

Using soles (Solea solea) infected experimentally with oncomiracidia of the monogenean skin parasite Entobdella soleae, it was found that the parasite begins to assemble eggs at about 85 days post infection and may survive for as long as 6 1/2 months at 12 +/- 1 degrees C. Growth of the anterior hamuli continues throughout life but the growth rate decreases with time. The oldest (largest) parasites recovered from laboratory soles were similar in size to the largest parasites collected in the wild.     

Intraspecific diversity of the marine fish pathogen Tenacibaculum maritimum as determined by randomly amplified polymorphic DNA-PCR

AIM: The aim of the present study was to evaluate the intraspecific genetic variability within Tenacibaculum maritimum strains isolated from different species of marine fish. METHODS AND RESULTS: Twenty-nine strains isolated from five different fish species and three reference strains were characterized by randomly amplified polymorphic DNA (RAPD) method. Cluster analysis of RAPD-PCR profiles showed that the strains, regardless of the oligonucleotide primer employed (P2 and P6), were separated into two main groups that strongly correlated with the host species and/or O-serotypes described for this pathogen. One group composed all strains isolated from sole (Solea senegalensis and S. solea) and gilthead seabream (Sparus aurata), and the other compiled the T. maritimum isolates from yellowtail (Seriola quinqueradiata), Atlantic salmon (Salmo salar) and turbot (Scophthalmus maximus). An important exception was observed in the RAPD patterns of the reference strains, which were included in different genetic groups depending on the primer employed. CONCLUSIONS: The results obtained demonstrated genetic variability within the T. maritimum isolated from different marine fish. Such genetic variability proved to be strongly associated with the host and/or serogroups described for this pathogen. SIGNIFICANCE AND IMPACT OF THE STUDY: The RAPD analysis constitutes a valuable molecular technique for epidemiological studies of T. maritimum. Interestingly, this is the first report of intraspecific differentiation and characterization of T. maritimum strains isolated from cultured fish.