Habitat and species differences in prevalence and intensity of Neobenedenia melleni (Monogenea: Capsalidae) on sympatric Caribbean surgeonfishes (Acanthuridae)

We quantified Neobenedenia melleni from the skin of Caribbean surgeonfishes (Acanthuridae) from June through October 2005 and 2007. Prevalence, or mean intensity of infection, or both, varied significantly among the 3 species, and among sites and between years for the most heavily infected species, blue tang (Acanthurus coeruleus). Among 6 sites sampled, no more than 12% of ocean surgeonfish (Acanthurus bahianus) were infected, compared with 10 to 100% of A. coeruleus. The prevalence of infection among doctorfish (Acanthurus chirurgus), collected at only 1 of the sites, was intermediate between the other 2 species (46%). Mean intensity (range) of infection for the few infected A. bahianus was 1 (1) to 3 (1-8), compared with 1.3 (1-2) to 14.3 (1-59) for A. coeruleus, and 2.5 (1-8) for A. chirurgus. Expected abundance of N. melleni on A. coeruleus from shallow bay sites was greater than for those from non-bay sites. Higher infections on A. coeruleus may be attributable to differences in habitat use, or susceptibility to infection, or both, compared to other species. Among site and between-year differences may be associated with differences in benthic habitat, or water conditions, or both. This system seems ideal for future comparative studies on the relationship between environmental variables and parasites on Caribbean coral reefs.     

Isolation and characterization of 23 microsatellite loci in the yellow tang, Zebrasoma flavescens (Pisces: Acanthuridae)

Twenty‐three microsatellites were isolated from the yellow tang (Zebrasoma flavescens), an ecologically and commercially important reef fish. Genetic diversity was assessed in 90 adults collected from Honokohau, Hawaii. The number of alleles per locus varied from four to 29 (mean = 13.8) and observed and expected heterozygosities ranged from 0.15 to 0.94 (mean = 0.70) and from 0.29 to 0.93 (mean = 0.81), respectively. Eight loci exhibited significant departure from Hardy–Weinberg equilibrium due to the presence of null alleles. Exact tests showed no evidence of genotypic disequilibrium between loci. Overall, loci were well resolved, easy to score and highly polymorphic.     

Social grouping and genetic variation in common shiners,Notropis cornutus (Pisces,Cyprinidae)

Synopsis Heterogeneous gene frequencies of Est-1 across groups ofNotropis cornutus provide evidence of behaviourally imposed restrictions on stock structuring. Positive fixation indices (F_1S = 0.056 and F_1T = 0.085) were reflected by a deficiency of heterozygotes for pooled groups. The degree of subdivision ofN. cornutus stocks cannot be evaluated with the present evidence. but it is likely that their schooling behaviour is associated with significant genotypic structuring of the species.     

Behavioural and growth responses to the intensity of intraspecific social interaction among medaka, Oryzias latipes (Temminck and Schlegel) (Pisces, Cyprinodontidae)

When access to food is restricted, faster growing fish may be those whose behaviour is relatively unaffected by the presence of nearby conspecifics. Behavioural experiments were carried out to determine the relation between growth and motor activity levels in crowded and uncrowded conditions, and measures of aversion/attraction to groups of conspecifics. Two experimental groups of Or)-ius laripes (Temminck and Schlegel) were grown for several weeks in two environments manipulated so as to maximize differences in social interactions. In the high interaction environment (HI), food was provided inside a floating cork ring. In the low interaction environment (LI), food was spread over the container's surface. Fish were measured at the end of the growth period and tested for their activity levels in the presence of conspecifics and for their preference for, or tolerance of crowded conditions. The correlation between motor activity and growth was significantly more positive in the HI environment than in the LI environment. The relationship between preference for crowded conditions and growth was negative for both groups of fish, although less so for HI than for LI. We conclude that artificial selection for faster growth may produce more aggressive fish only under very high levels of forced social interaction (competition), if at all. Under conditions of reduced social interaction, the social-aversive or socially indifferent fish grow faster.     

Patterns of lineage diversification in the genus Naso (Acanthuridae)

The evolutionary history of the reef fish genus Naso (F. Acanthuridae) was examined using a complete species-level molecular phylogeny of all recognized (19) species based on three loci (one nuclear ETS2 and two mitochondrial 16S, cyt b). This study demonstrates that distinct foraging modes and specialized body shapes arose independently at different times in the evolutionary history of the genus. Members of the subgenus Axinurus, characterized by a scombriform morphology, caudal fin structure and pelagic foraging mode, were consistently placed basal to the remaining Naso species, suggesting that pelagic foraging is plesiomorphic and benthic foraging derived in this genus. We used a genus-level phylogeny (nuclear marker, ETS2), which included several taxa from all other acanthurid genera, to obtain a range of age estimates for the most recent common ancestor of the genus Naso. These age estimates (range of 52-43.3 MY) were then used to estimate divergence times (by nonparametric rate smoothing method) of the node giving rise to extant Naso species using the combined sequence data (from all loci). The reconstruction of the pattern of divergence of extant species indicates two sequences of events. The basal species characterized by pelagic foraging modes arose during the Eocene and Oligocene. Most of the remaining Naso species, including those characterized by benthic foraging, arose over a period of 20 MY during the Miocene. Diversification during this period was associated with major plate tectonic and glaciation events, resulting in changes in sea level, ocean temperature and productivity regimes. Regardless of the foraging mode exhibited, all species of Naso have a caudal propulsive unit similar to that observed in pelagic scombriform fishes, a legacy of the basal position of the subgenus Axinurus in the phylogeny of the genus.     

An integrative approach to sex change: social, behavioural and neurochemical changes in Lythrypnus dalli (Pisces)

This study examined three aspects of protogynous sex change in Lythrypnus dalli (Gobiidae): (1) social influences on the rate of sex change, (2) the sequence of behavioural changes, and (3) neuroendocrine changes. Social groups consisted of either four females, or four females with a male who was subsequently removed. Sex change occurred most rapidly in male- removed groups when the sex changer was larger than other females. Sex changers in female only groups and sex changers not larger than other females in male-removed groups changed sex at similar rates. These differences may be explained by two factors that affect dominance: prior knowledge of the social group and greater size. Sex changers were dominant to other females prior to male removal, and larger sex changers increased displacement rates three-fold immediately after male removal. Sex changers in the other groups did not show this increase in displacements. This early establishment of dominance accounts for the overall difference in the rate of sex change. Prior to spawning, however, all sex changers increased displacements and performed male-typical displays. Arginine vasotocin-immunoreactive forebrain cells of sex changers were similar in size to field-collected males, and larger than field-collected females. Previously nesting males also changed sex in male-only groups, but at slow rates. These data are combined with those of existing studies to generate an integrative model of sex change in this goby. Received: 17 March 1999 / Received in revised form: 15 May 1999 / Accepted: 28 May 1999     

Cytogenetic studies of Poecilia (Pisces)

Natural populations of triploid females resembling the gynogenetic teleost, Poecilia formosa (Girard), occur in northeastern Mexico where they intermingle with diploid populations of this species and the members of congeneric bisexual species such as P. mexicana or P. latipinna. Mitotic configurations from gill epithelial cells show 46 chromosomes for the diploid fishes, but 69 chromosomes for members of the triploid clones associated with P. formosa. Triploid females have erythrocytes that are significantly larger than those from diploid specimens and also show a roughly 50% elevation in the average DNA content of their somatic nuclei. Similar analyses of two functionally incompetent males of P. formosa, of a number of bisexual F₁ and F₂ hybrid offpsring from P. latipinna x P. mexicana, and of females from several other poeciliid species consistently show only diploid DNA levels and somatic chromosome complements where 22N=46. Demonstration of cytogenetic criteria by which females from triploid clones may be clearly distinguished from sympatric diploid specimens of P. formosa or P. mexicana leaves unresolved, for the present, problems of an appropriate systematic designation for natural populations of triploid gynogenetic fishes. The role of sympatric speciation in the evolution of poeciliid genomes is discussed in terms of alternative mechanisms to account for the persistence in nature of a vertebrate triploid of hybrid origin.This work was supported by grants from the National Science Foundation (GB 7393) and from the U.S. Public Health Service (GM 14644).Recipient of a Research Career Development Award from the U.S. Public Health Service (1 K3 GM 3455).     

Karyotype similarities among Pimelodidae (Pisces, Siluriformes) from the Brazilian amazon region.

Three neotropical species of freshwater fish (Pseudoplatystoma fasciatum, P. tigrinum and Sorubim lima) of the Amazon region (Brazil) were cytogenetically analysed by means of conventional, silver staining and C-banding techniques. All showed 2n = 56, with a predominance of biarmed chromosomes. The NORs were located in the terminal position on the short arms, and only two chromosomes bearing NORs were detected. Heterochromatin was found to be equilocally distributed in some chromosomes of the three species, which may share homologous chromosomes. The present data indicate a somewhat conservative karyotypic evolution in this fish group.     

Alternative reproductive styles in seabreams (Pisces: Sparidae)

Synopsis A review of sexuality in the Sparidae shows that protandrous, protogynous, simultaneous and rudimentary hermaphroditism have all been reported in the family. Careful histological study shows that even in those species reputed to have separate sexes, intersexuality is found in the juvenile condition. We suggest that two reproductive styles, sex change and late gonochorism are found in the family. The bi-potentiality of the sparid gonad is considered to be a pre-adaptation for the development of sequential hermaphroditism in species in which reproductive success is size related. In these species sex change is an alternative reproductive style that enables individuals to maximise their lifetime reproductive success by functioning as one sex when small and the other sex when large.     

Phylogenetic relationships among Spanish Barbus species (Pisces,Cyprinidae) shown by RAPD markers

Random amplified polymorphic DNA (RAPD) markers were used to estimate the population structure and phylogenetic relationships among the eight species of the genus Barbus that inhabit the Iberian Peninsula. Ten random oligodecamers were used to amplify DNA from 232 fish sampled from 15 populations. A total of 270 markers were detected that revealed low levels of genetic variability. The conclusions of cluster analysis indicate two main branches and three well-differentiated groups: north-eastern, Mediterranean and Atlantic. This clustering mainly reflects the evolutionary history of the genus, which is closely related to the paleogeography of the Iberian Peninsula. The contribution and application of these results to the conservation of the species, to their taxonomic status and to the process of colonization of the Iberian Peninsula by the genus Barbus are discussed.     

Evolution and biogeography of marine angelfishes (Pisces: Pomacanthidae)

Phylogenetic relationships among angelfishes (Pomacanthidae) and their putative sister taxon, the butterflyfishes (Chaetodontidae), were examined using 12S and 16S mitochondrial DNA sequences. ML and MP trees were highly congruent with good basal resolution. Monophyly of the two families was supported, although a clade comprising the Chaetodontidae and one of the outgroups, the Scatophagidae, formed the sister clade to the Pomacanthidae. All genera and subgenera within the Pomacanthidae were examined. The relationships among the 24 representative species were consistent with traditional generic boundaries, with the exception of the genus Centropyge, but differed from previous phylogenies. Estimated ages of divergence based on trans-isthmian pairs were compared with independent fossil evidence. Trans-isthmian estimates were highly conservative, while fossil-calibrated estimates were most consistent with available evidence. Fossil calibrated estimates suggest that the family has been impacted by both the Terminal Tethyan Event and the closure of the Isthmus of Panama. Within the family, ecological diversity and species-level diversification are restricted primarily to a single pygmy angelfish clade with an origin near the Oligocene-Miocene boundary.     

Postconflict social interactions among barbary macaques (Macaca sylvanus)

We investigated the occurrence of postconflict social interactions in a group of Barbary macaques (Macaca sylvanus)that live in a large enclosure. We collected data during the mating and the nonmating seasons and analyzed them via two methods. Separate analyses for the two seasons yielded very similar results. Reconciliation and redirection occurred. But we found no evidence for consolation and postconflict kin-oriented affiliation. The consistency of these findings with those on other species of Macacaindicates that reconciliation and redirection are typical postconflict social interactions of macaque victims.     

Short communication. First record of larval Brama brama (Pisces: Bramidae) and Corphaena hippurus (Pisces: Coryphaenidae) in the Adriatic Sea

The occurrence of early larval stages of Brama brama and Coryphaena hippurus is reported for the first time in Adriatic waters. Two larvae of B.brama between 4.36 and 5.00 mm, and two larvae of C.hippurus between 4.75 and 4.95 mm standard length, were found in ichthyoplankton collections taken off the River Neretva estuary (43010N, 17°250E) and station Stoncica, island Vis (43°000N, 16°20E) (eastern middle Adriatic), respectively. The capture of both species (B.brama) in August 1998; C.hippurus in May 1998) is in agreement with their proposed seasonal life cycle in the Adriatic Sea.      

Hormonal stimulation of maturation and ovulation of oocytes in Zebrasoma scopas (Acanthuridae)

The experiments were carried out on hormonal stimulation of oocyte maturation in Zebrasoma scopas from the South China Sea, Vietnam. Three variants of surfagon injections were studied: 1—double injections (5 + 20 μg/kg of fish body weight); 2—double injections (2 + 8 μg/kg); and 3—single injections (20 μg/kg). The time interval between two injections comprised 15–24 h. Ovulation of oocytes in variants 1 and 2 was observed in most (67%) females 33–47 h after the first injection. The increase of the time interval between injections I and II was followed by the decrease of the interval between injection II and ovulation. In variant 3, oocytes ripened but ovulation was absent. The oocytes possessed with the competence for maturation are always present in the ovaries because of a continuous type of oogenesis. The morphological changes in oocytes in the process of maturation were observed. Ovulated oocytes could be stored in the ovary cavity no more than 4 h; the number of embryos with normal cleavage decreased during this time from 90 to 53%.     

Male-female Parental Roles in Sarotherodon galilaeus (Pisces: Cichlidae)

Sarotherodon galilaeus is a predominantly biparental, sexually monomorphic mouthbrooder. 15 spawnings of pairs in the weight range 150–450 g were observed in aquaria. Only clutches of females larger than 320 g were reared jointly; with those of smaller females, the first fish to pick up eggs brooded alone, while the comparatively few eggs left for the second fish were invariably eaten. The latency after which eggs were picked up increased with the duration of spawning and indirectly with fish size. This increase was larger in males than in females, so large males started to collect eggs later than their mates. In small pairs (female weight < 200 g), by contrast, the male would pick up eggs first and carry them alone. This is the case in a smaller congeneric species, S. melanotheron, indicating that the apportioning of broodcare is based on a unitary, size-dependent mechanism among Sarotherodon. Yet picking-up order was not entirely determined by these equations. Some fish did not show any reaction towards the eggs and occasionally males became care-givers despite expected longer latency, seemingly because of aggressive dominance.     

Internal fertilization in Lepidogalaxias salamandroides Mees (Pisces: Lepidogalaxiidae)

The gonads of Lepidogalaxias salamandroides are structurally distinctive. A duct, the surface of which is ciliated, is located on the ventral surface of each ovary and may be a modification of the ovarian tunica. The testes are small and the majority of the testicular structure functions as a sperm storage area. Secondary requisite sex characters are present in the male and the function of a modified scale sheath in copulation is unique among teleosts. Fertilization is internal and a viscous mucus mass secreted during copulation may serve as a copulatory plug. It is postulated that internal fertilization within this species has arisen as a response to sperm competition.     

Internal fertilization in Lepidogalaxias salamandroides Mees (Pisces: Lepidogalaxiidae)

The gonads of Lepidogalaxias salamandroides are structurally distinctive. A duct, the surface of which is ciliated, is located on the ventral surface of each ovary and may be a modification of the ovarian tunica. The testes are small and the majority of the testicular structure functions as a sperm storage area. Secondary requisite sex characters are present in the male and the function of a modified scale sheath in copulation is unique among teleosts. Fertilization is internal and a viscous mucus mass secreted during copulation may serve as a copulatory plug. It is postulated that internal fertilization within this species has arisen as a response to sperm competition.