Chromosomal analysis of repeated DNAs in the rainbow wrasse Coris julis (Pisces, Labridae)

Despite the interest of several authors, the karyotype of the labrid C. julis is still debated and in particular the presence of sex-chromosomes is still contradictory. In order to analyze the karyotype organization of C. julis we have performed an analysis with classical and molecular cytogenetic techniques. Our results after silver-, CMA₃- and DAPI-staining, C-banding and fluorescent in situ hybridization (FISH) using 28S rDNA, 5S rDNA, and telomeric repeat (TTAGGG) _n as probes allowed us to characterize the chromosomal location of several repetitive DNAs of C. julis. Finally, regardless of the technique used, no difference in the chromosome complement was found between males and females. This revised version was published online in August 2006 with corrections to the Cover Date.     

Sex-inversion of the hermaphroditic, protogynous teleost Coris julis L. (Labridae)

Sex-inversion of Coris julis , a protogynous hermaphrodite, was studied using histological and cytological criteria. Four stages were recognized: oocyte and oogonial atresia; occurrence of spermatogonia with primordial germ cells (PGC) in the ovarian wall; onset of spermatogonial proliferation; considerable proliferation of spermatogonia and PGC with build-up of seminiferous tubules. Spermatogonia arise from PGC, undifferentiated and bipotential cells, in which mitotic activity was detected.     

First report of Streptococcus agalactiae and Lactococcus garvieae from a wild bottlenose dolphin (Tursiops truncatus)

The isolation and characterization of two bacterial species, Streptococcus agalactiae and Lactococcus garvieae, previously unreported in wild marine mammals are described from a freshly dead bottlenose dolphin, Tursiops truncatus, from Kuwait Bay, Kuwait, in September 2001. Conventional and rapid identification systems were used to determine that isolates from muscle and kidney were S. agalactiae and L. garvieae, respectively. The isolates were gram-positive, catalase-negative, oxidase-negative, nonhemolytic cocci. The S. agalactiae was serotyped to group antigen B, whereas the L. garvieae could not be assigned to any serogroup. These Kuwait isolates displayed considerable homogeneity with corresponding American Type Culture Collection (ATCC) type isolates. Although the dolphin S. agalactiae isolate was nonhemolytic, it was biochemically similar to S. agalactiae isolated from mullet sampled in the concurrent Kuwait Bay fish kill. Some biochemical heterogeneity was observed between the dolphin isolates and corresponding mammalian ATCC type isolates, especially with Voges Proskauer, alanine-phenylanaline-proline arylamidase, and alpha-galactosidase tests. Nile tilapia, Oreochromis niloticus, experimentally infected with the dolphin S. agalactiae and L. garvieae isolates experienced 90% and 0% mortalities, respectively. This is the first isolation of S. agalactiae and L. garvieae from a wild marine mammal, and the microbial characteristics established here provide pertinent information for the future isolation of these bacteria.     

Catching power of pots for wrasse Evaluation of the relative catching power of pots for north European wrasse (Labridae)

The relative catching power of three types of pot was examined in aquaria and field trials. The Sunart trap was more efficient in catching goldsinny ( Ctenolabrus rupestris (L.)) and rock cook wrasse ( Centrolabrus exoletus (L.)) than was the prawn creel or the Norwegian trap; all catches were enhanced by using fish bait. Although the catch rate is lower, the Norwegian pot may still be preferred by fishermen since damage to wrasse is minimised.     

Social control of sex change in the Red Sea razorfish Xyrichtys pentadactylus (Teleostei,Labridae)

Synopsis The Red Sea razorfish, Xyrichtys pentadactylus, a territorial haremic labrid with dominance hierarchies within the harems. Theory predicts that primary males (fish developing initially as males) should be rare or nonexistent in haremic territorial species because the larger secondary males (males which have undergone sex and/or color change) limit access to females. Histological examination of gonads of 95 specimens showed that all males are derived from females by sex change (i.e. they are secondary males). During five months of field studies 100% of more than 200 observed matings were pair spawnings — the usual mating practice for monandric (having one type of male) species. Sex change in females was induced by male removal in nature. Isolation of four groups of females in aquaria showed that the largest female in the social group changes sex in the absence of a male, demonstrating that sex change is socially-controlled in this species.     

Modulation of prey capture kinematics in the cheeklined wrasse Oxycheilinus digrammus (Teleostei: Labridae)

The ability to modulate prey capture behaviors is of interest to organismal biologists as it suggests that predators can perceive features of the prey and select suitable behaviors from an available repertoire to successfully capture the item. Thus, behavior may be as important a trait as morphology in determining an organism's diet. Using high-speed video, we measured prey capture kinematics in three cheeklined wrasse, Oxycheilinus digrammus. We studied the effects of three experimental prey treatments: live fish, dead prawn suspended in the water column, and dead prawn pieces anchored to the substrate in a clip. Live prey elicited significantly more rapid strikes than dead prey suspended in the water column, and the head of the predator was expanded to significantly larger maxima. These changes in prey capture kinematics suggest the generation of more inertial suction. With greater expansion of the head, more water can be accelerated into the buccal cavity. The attached prey treatment elicited strikes as rapid as those on live prey. We suggest that the kinematics of rapid strikes on attached prey are indicative of attempts to use suction to detach the prey item. More rapid expansion of the buccal or mouth cavity should lead to higher velocities of water entering the mouth and therefore to enhanced suction. Further modulation in response to the attached prey item, such as clipping or wrenching behaviors, was not observed. J. Exp. Zool. 290:88-100, 2001.     

The distribution, age and growth of wrasse (Labridae) in inshore waters of west Scotland

Wrasse were widely distributed in inshore waters of west Scotland in rocky and algal habitats. Ctenolabrus rupestris and Centrolabrus exoletus dominated commercial and experimental catches using creels, traps and fyke nets, but Crenilabrus melops, Labrus bergylta and L. mixtus were infrequent. Maximum age of sampled fish was 16yr in C. rupestris , 9 yr in C. exolefus , 5 yr in C. melops , 15 yr in L. bergylta , and 11 yr in L. mixtus . Growth was more rapid prior to maturation in all species. The von Bertalanffy growth model fitted data for C. rupestris and C. exoletus . Male C. rupestris and C. exoletus were significantly longer than females in most age groups and growth of all species captured in mid–Scottish areas was more rapid than in northern localities. Mortality (Z) of C. rupestris was 0–1861 per year and 0·4185 in C exoletus .     

Benefits of heterospecific foraging by the Caribbean wrasse,Halichoeres garnoti (Pisces: Labridae)

Synopsis Terminal-phase yellowhead wrasses, Halichoeres garnoti, foraged alone or in association with foraging goatfish, Pseudupeneus maculatus and Mulloides martinicus. Whereas H. garnoti did not dig for benthic infauna, the goatfish foraged almost exclusively on and in sand substrata. Wrasses in the company of goatfish made significantly more strikes on sand substrata than did solitary wrasses, although there were no significant differences in the frequency of strikes on sand and hard substrata combined. The frequencies of other behaviors (searches, scratches, flights, chases, rests, yawns, and cleanings) were not significantly different between solitary and associated wrasses. H. garnoti are attracted to foraging goatfish, which provide access to an otherwise unavailable food resource. To whom reprint requests should be sent     

The effects of testosterone implants on ovarian morphology in the bluehead wrasse, Thalassoma bifasciatum (Bloch) (Teleostei: Labridae)

The effects of exogenous testosterone pellet implants at 21 and 40 days on the ovary of Thalassoma bifasciatum , a protogynous marine fish, are described. The characteristic markings of the terminal blue phase appeared by 4 to 5 days and were complete by 18 days. There was no shift in sex ratio in the treated fish when compared to an untreated control group. None of the ovaries showed signs of precocious transformation, i.e., spermatogenic tissue was lacking, and there was no evidence of duct formation. Instead, however, the ovaries of the treated fish showed marked degenerative changes characterized by oocyte breakdown, fat infiltration, vacuolization, the accumulation of fibrous PAS+ material and the appearance of small eosinophilic cells.
These findings conflict with earlier studies on the same organism that employed different procedures. However, they resemble more closely the results obtained from work on another protogynoid, the ricefield eel, Monopterus albus. They add new light on the role of sex hormones in the reversal process of T. bifasciatum and hermaphroditic fishes in general.     

Genetic population structure of the endemic fourline wrasse (Larabicus quadrilineatus) suggests limited larval dispersal distances in the Red Sea

The connectivity among marine populations is determined by the dispersal capabilities of adults as well as their eggs and larvae. Dispersal distances and directions have a profound effect on gene flow and genetic differentiation within species. Genetic homogeneity over large areas is a common feature of coral reef fishes and can reflect high dispersal capability resulting in high levels of gene flow. If fish larvae return to their parental reef, gene flow would be restricted and genetic differentiation could occur. Larabicus quadrilineatus (Labridae) is considered as an endemic fish species of the Red Sea and Gulf of Aden. The juveniles of this species are cleaner fish that feed on ectoparasites of other fishes. Here, we investigated the genetic population structure and gene flow in L. quadrilineatus among five locations in the Red Sea to infer connectivity among them. To estimate genetic diversity, we analysed 369 bp of 237 mitochondrial DNA control region sequences. Haplotype and nucleotide diversities were higher in the southern than in the northern Red Sea. Analysis of molecular variance (amova) detected the highest significant genetic variation between northern and central/southern populations (Phi(CT) = 0.01; P < 0.001). Migration analysis revealed a several fold higher northward than southward migration, which could be explained by oceanographic conditions and spawning season. Even though the Phi(ST) value of 0.01 is rather low and implies a long larval dispersal distance, estimates based on the isolation-by-distance model show a very low mean larval dispersal distance (0.44-5.1 km) compared to other studies. In order to enable a sustainable ornamental fishery on the fourline wrasse, the results of this study suggest that populations in the northern and southern Red Sea should be managed separately as two different stocks. The rather low larval dispersal distance of about 5 km needs to be considered in the design of marine protected areas to enable connectivity and self-seeding.     

Dating the evolutionary origins of wrasse lineages (Labridae) and the rise of trophic novelty on coral reefs

We estimated ages of divergence between major labrid tribes and the timing of the evolution of trophic novelty. Sequence data for 101 labrid taxa and 14 outgroups consisting of two mitochondrial gene regions (12s, 16s), and two nuclear protein-coding genes (RAG2, TMO4c4), a combined 2567 bp of sequence, were examined using novel maximum likelihood, maximum parsimony and mixed model Bayesian inference methods. These analyses yielded well supported trees consistent with published phylogenies. Bayesian inference using five fossil calibration points estimated the minimum ages of lineages. With origins in the late Cretaceous to early tertiary, the family diversified quickly with both major lineages (hypsigenyine and julidine) present at approximately 62.7 Ma, shortly after the K/T boundary. All lineages leading to major tribes were in place by the beginning of the Miocene (23 Ma) with most diversification in extant lineages occurring within the Miocene. Optimisation of trophic information onto the chronogram revealed multiple origins of novel feeding modes with two distinct periods of innovation. The Palaeocene/Eocene saw the origins of feeding modes that are well represented in other families: gastropod feeders, piscivores and browsing herbivores. A wave of innovation in the Oligocene/Miocene resulted in specialized feeding modes, rarely seen in other groups: coral feeding, foraminifera feeding and fish cleaning. There is little evidence of a general relationship between trophic specialization and species diversity. The current trophic diversity of the Labridae is a result of the accumulation of feeding modes dating back to the K/T boundary at 65 Ma, with all major feeding modes on present day reefs already in place 7.5 million years ago.     

Human chorionic gonadotropin (hCG) induces gonad reversal in a protogynous fish, the bluehead wrasse, Thalassoma bifasciatum (Teleostei, Labridae)

Female to male successive hermaphroditism (protogyny) is common in several groups of marine fish. Thalassoma bifasciatum, the bluehead wrasse (Labridae), found in the reefs of the Caribbean normally undergoes sex reversal after receiving behavioral cues. This report deals with the successful use of human chorionic gonadotropin (hCG) in inducing gonad reversal in this species. Eighty percent (n = 40) of the treated fish showed signs of reversal in 1-6 weeks; only 11% (n = 54) of the control (nontreated) group showed signs of reversal during the same period. The number of fish undergoing reversal increased with the length of the treatment period, 55% after 1 week, 100% after 6 weeks. A bluehead color pattern, typical of the terminal male phase, also appeared more frequently in the longer treated groups. To determine the efficacy of hCG in inducing gonad reversal, morphological criteria for reversal had to be established. For the majority of treated fish, the presence of both spermatogenic cysts and degenerating oocytes was sufficient to label these gonads unambiguously as undergoing reversal. However, at the extremes of this process, i.e., onset (early) and endpoint (late) stages, ambiguity could arise in identifying a gonad as undergoing reversal, and, therefore, key criteria were established for these stages. In our hands, the most consistent and reliable criterion for the early stage reversal was appearance of male germ line cells, clusters of "spermatogonial-like" cells. For the late stage, recognizable remnants of late-state oocytes had to be present. Some details of the histological changes that occur during early, middle, and late stages of reversal are also described. It is suggested that these results with hCG shed new light on the endocrine control of gonad reversal in T. bifasciatum.     

The spawning, embryonic and early larval development of the green wrasse Labrus viridis (Linnaeus, 1758) (Labridae) in controlled conditions

Green wrasse, Labrus viridis (Linnaeus, 1758), is an endangered species in the southern Adriatic Sea, but it is also of interest for potential rearing in polyculture with other commercial species for the repopulation of areas where it is endangered or as a new aquaculture species. A parental stock of the green wrasse was kept in aquaria for six years. The spawning, embryonic and early larval development maintained under controlled laboratory conditions are described and illustrated. The average diameter of newly spawned eggs was 1.01±0.03 mm. Mature and fertilized eggs were attached to the tank bottom by mucus. Hatching started after 127 h at a mean temperature of 14.4±0.8°C. The average total length of newly hatched larvae was 4.80±0.22 mm. Absorption of the yolk-sac was completed after the 5th day when larvae reached 5.87±0.28 mm. Larvae were fed with the rotifers Brachionus plicatilis. The pigmentation of L. viridis larvae is similar to that of Labrus merula and Labrus bergylta, but the main differences between these species are in the size of larvae and the development time of the melanophores on the anal fin-fold (five days later than with L. merula) and on top of the head (nine days earlier than with L. merula).     

Attack intensity by two species of territorial damselfish (Pomacentridae) as estimates of competitive overlap with two species of wrasse (Labridae)

The intensity of interspecific territorial defense should be based upon the degree of competitive overlap. We tested this relationship in two territorial Caribbean damselfish (dusky, Stegastes adustus, and longfin, S. diencaeous) with intruders being the bluehead wrasse (Thalassoma bifascatus) and the slippery dick wrasse (Halichoeres bivittatus). Based on food habits, the slippery dick and the bluehead wrasse should have the same degree of competitive overlap to the two damselfish species. We also predicted that the larger slippery dick wrasse intruder would receive more aggression than the smaller bluehead wrasse intruder. Neither damselfish species distinguished between the two wrasses suggesting that they were ecologically equivalent. We also tested size differences within both species of wrasse and found that size had no influence on the aggression in the dusky damselfish. The longfin also did not show a size preference for the bluehead but did prefer to attack the larger slippery dick wrasse. In spite of the similarities between the dusky and the longfin damselfish and the similar food habits of the bluehead and the slippery dick wrasse, our results suggest that using intensity of interspecific territorial defense alone may not be an adequate measure of competitive overlap.     

Streptococcus iniae infections in Red Sea cage-cultured and wild fishes

Streptococcus iniae was isolated from 2 moribund wild Red Sea fishes, Pomadasys stridens (Pomadasyidae) and Synodus variegatus (Synodontidae), both collected in shallow waters along the Israeli coast of the Gulf of Eilat. The site is approximately 2 km from a mariculture cage farm in which streptococcal infections were diagnosed in previous years in the red drum Sciaenops ocellatus. This is the first report of S. iniae in Red Sea fishes. Biochemical and molecular similarities between the isolates from cultured fishes and those from the wild specimens suggest that a single strain is involved, and that 'amplification' and dispersal of this pathogen from captive to feral fishes have occurred. At the molecular level, the pathogen is different from the S. iniae isolates that have been afflicting the Israeli freshwater aquaculture in recent years. Although S. iniae prevalence in the wild fish populations of the area remains to be determined, the northernmost region of the Gulf of Eilat, virtually landlocked and with generally calm seas and weak currents, seems to be particularly vulnerable to the impact of diseases that develop in this mariculture system.     

Characterization of plasmids in a human clinical strain of Lactococcus garvieae

The present work describes the molecular characterization of five circular plasmids found in the human clinical strain Lactococcus garvieae 21881. The plasmids were designated pGL1-pGL5, with molecular sizes of 4,536 bp, 4,572 bp, 12,948 bp, 14,006 bp and 68,798 bp, respectively. Based on detailed sequence analysis, some of these plasmids appear to be mosaics composed of DNA obtained by modular exchange between different species of lactic acid bacteria. Based on sequence data and the derived presence of certain genes and proteins, the plasmid pGL2 appears to replicate via a rolling-circle mechanism, while the other four plasmids appear to belong to the group of lactococcal theta-type replicons. The plasmids pGL1, pGL2 and pGL5 encode putative proteins related with bacteriocin synthesis and bacteriocin secretion and immunity. The plasmid pGL5 harbors genes (txn, orf5 and orf25) encoding proteins that could be considered putative virulence factors. The gene txn encodes a protein with an enzymatic domain corresponding to the family actin-ADP-ribosyltransferases toxins, which are known to play a key role in pathogenesis of a variety of bacterial pathogens. The genes orf5 and orf25 encode two putative surface proteins containing the cell wall-sorting motif LPXTG, with mucin-binding and collagen-binding protein domains, respectively. These proteins could be involved in the adherence of L. garvieae to mucus from the intestine, facilitating further interaction with intestinal epithelial cells and to collagenous tissues such as the collagen-rich heart valves. To our knowledge, this is the first report on the characterization of plasmids in a human clinical strain of this pathogen.     

Expression of immune-related genes in rainbow trout (Oncorhynchus mykiss) induced by probiotic bacteria during Lactococcus garvieae infection

The aim of the present study was to investigate the effect of lactic acid bacteria (LAB) on the control of lactococcosis as well as to assess the impact of probiotics on the expression of immune-related genes in the head kidney and intestine of rainbow trout (Oncorhynchus mykiss). Lactobacillus plantarum, Lactococcus lactis and Leuconostoc mesenteroides, were administered orally at 10? CFU g?1 feed to fish for 36 days. Twenty-one days after the start of the feeding period, fish were challenged with Lactococcus garvieae. Only the fish fed the diet containing Lb. plantarum showed significantly (P < 0.05) improved protection against L. garvieae compared to the control. Subsequently, real-time PCR was employed to determine the mRNA levels of IL-1β, IL-8, IL-10 and TNF-α in the head kidney, and IL-8, Tlr5 and IgT in the intestine of the control and Lb. plantarum groups. IL-1β, IL-10 and TNF-α gene expression were significantly up-regulated by Lb. plantarum. Moreover, the mRNA levels of IL-10, IL-8 and IgT were significantly higher in the Lb. plantarum group after L. garvieae infection, suggesting that Lb. plantarum can stimulate the immune response of rainbow trout. PCR-DGGE revealed no detectable levels of the probiotics or the pathogen present on the distal intestinal mucosa. These findings demonstrate that direct probiotic-host interactions with the intestine are not always necessary to induce host stimulatory responses which ultimately enhance disease resistance. Furthermore, as L. garvieae did not colonise the intestinal tract, and therefore likely did not infect via this route, the antagonistic properties of the probiotic candidate towards L. garvieae were likely of little influence in mediating the improved disease resistance which could be attributed to the elevated immunological response.