Fishes associating with shallow water echinoids at Roatán, Honduras

We studied the association of 11 species of fishes with 5 species of echinoids at Roatán, Honduras, from 27 August to 1 September 2017. Fishes associated most frequently with the echinoid Diadema antillarum (34.3% of echinoids, six fish species, n = 146 echinoids), followed by Echinometra viridis (25.0%, three fish species, n = 12), Echinometra lucunter (7.5%, ten fish species, n = 1,834), Eucidaris tribuloides (3.4%, four fish species, n = 116), and Tripneustes ventricosus (7.1%, one fish species, n = 28). Of 196 fishes seeking shelter beside echinoids, Malacoctenus aurolineatus was the most common (41.8% of fishes, three echinoid species), followed by Stegastes adustus (38.8%, three echinoid species), Stegastes diencaeus (6.6%, three echinoid species), Sargocentron coruscum (6.1%, five echinoid species), Chaetodon capistratus (1.5%, one echinoid species), Gobioclinus filamentosus (1.5%, one echinoid species), Pomacanthus paru (1.0%, two echinoid species), Labrisomus nuchipinnis (1.0%, two echinoid species), Equetus punctatus (0.5%, one echinoid species), Microspathodon chryurus (0.5%, one echinoid species), and Thalassoma bifasciatum (0.5%, one echinoid species). None of the fishes associated exclusively with echinoids or was specialized for associating with echinoids, indicating the association was facultative. All fishes were small (< 12 cm). Fishes associated most frequently with the longest-spined echinoid, D. antillarum, supporting the hypothesis that fishes seek shelter among the spines of echinoids to benefit from increased protection from predation.

Conservation and diversity in expression of candidate genes regulating socially-induced female-male sex change in wrasses

Fishes exhibit remarkably diverse, and plastic, patterns of sexual development, most striking of which is sequential hermaphroditism, where individuals readily reverse sex in adulthood. How this stunning example of phenotypic plasticity is controlled at a genetic level remains poorly understood. Several genes have been implicated in regulating sex change, yet the degree to which a conserved genetic machinery orchestrates this process has not yet been addressed. Using captive and in-the-field social manipulations to initiate sex change, combined with a comparative qPCR approach, we compared expression patterns of four candidate regulatory genes among three species of wrasses (Labridae)—a large and diverse teleost family where female-to-male sex change is pervasive, socially-cued, and likely ancestral. Expression in brain and gonadal tissues were compared among the iconic tropical bluehead wrasse (Thalassoma bifasciatum) and the temperate spotty (Notolabrus celidotus) and kyusen (Parajulus poecilepterus) wrasses. In all three species, gonadal sex change was preceded by downregulation of cyp19a1a (encoding gonadal aromatase that converts androgens to oestrogens) and accompanied by upregulation of amh (encoding anti-müllerian hormone that primarily regulates male germ cell development), and these genes may act concurrently to orchestrate ovary-testis transformation. In the brain, our data argue against a role for brain aromatase (cyp19a1b) in initiating behavioural sex change, as its expression trailed behavioural changes. However, we find that isotocin (it, that regulates teleost socio-sexual behaviours) expression correlated with dominant male-specific behaviours in the bluehead wrasse, suggesting it upregulation mediates the rapid behavioural sex change characteristic of blueheads and other tropical wrasses. However, it expression was not sex-biased in temperate spotty and kyusen wrasses, where sex change is more protracted and social groups may be less tightly-structured. Together, these findings suggest that while key components of the molecular machinery controlling gonadal sex change are phylogenetically conserved among wrasses, neural pathways governing behavioural sex change may be more variable.

Conservation and diversity in expression of candidate genes regulating socially-induced female-male sex change in wrasses

Fishes exhibit remarkably diverse, and plastic, patterns of sexual development, most striking of which is sequential hermaphroditism, where individuals readily reverse sex in adulthood. How this stunning example of phenotypic plasticity is controlled at a genetic level remains poorly understood. Several genes have been implicated in regulating sex change, yet the degree to which a conserved genetic machinery orchestrates this process has not yet been addressed. Using captive and in-the-field social manipulations to initiate sex change, combined with a comparative qPCR approach, we compared expression patterns of four candidate regulatory genes among three species of wrasses (Labridae) - a large and diverse teleost family where female-to-male sex change is pervasive, socially-cued, and likely ancestral. Expression in brain and gonadal tissues were compared among the iconic tropical bluehead wrasse (Thalassoma bifasciatum) and the temperate spotty (Notolabrus celidotus) and kyusen (Parajulus poecilepterus) wrasses. In all three species, cyp19a1a (encoding gonadal aromatase that converts androgens to oestrogens) and amh (encoding anti-müllerian hormone that primarily regulates male germ cell development) were downregulated and upregulated, respectively, at the initiation of gonadal sex change, and may act concurrently to orchestrate ovary-testis transformation. In the brain, our data argue against a role for brain aromatase (cyp19a1b) in initiating behavioural sex change, as its expression trailed behavioural changes. However, we find that isotocin (it, that regulates teleost socio-sexual behaviours) expression correlated with dominant male-specific behaviours in the bluehead wrasse, suggesting it upregulation mediates the rapid behavioural sex change characteristic of blueheads and other tropical wrasses. However, it expression was not sex-biased in temperate spotty and kyusen wrasses, where sex change is more protracted and social groups may be less tightly-structured. Together, these findings suggest that while key components of the molecular machinery controlling gonadal sex change are phylogenetically conserved among wrasses, neural pathways governing behavioural sex change may be more variable.

Conservation and diversity in expression of candidate genes regulating socially-induced female-male sex change in wrasses

Fishes exhibit remarkably diverse, and plastic, patterns of sexual development, most striking of which is sequential hermaphroditism, where individuals readily reverse sex in adulthood. How this stunning example of phenotypic plasticity is controlled at a genetic level remains poorly understood. Several genes have been implicated in regulating sex change, yet the degree to which a conserved genetic machinery orchestrates this process has not yet been addressed. Using captive and in-the-field social manipulations to initiate sex change, combined with a comparative qPCR approach, we compared expression patterns of four candidate regulatory genes among three species of wrasses (Labridae) - a large and diverse teleost family where female-to-male sex change is pervasive, socially-cued, and likely ancestral. Expression in brain and gonadal tissues were compared among the iconic tropical bluehead wrasse (Thalassoma bifasciatum) and the temperate spotty (Notolabrus celidotus) and kyusen (Parajulus poecilepterus) wrasses. In all three species, cyp19a1a (encoding gonadal aromatase that converts androgens to oestrogens) and amh (encoding anti-müllerian hormone that primarily regulates male germ cell development) were downregulated and upregulated, respectively, at the initiation of gonadal sex change, and may act concurrently to orchestrate ovary-testis transformation. In the brain, our data argue against a role for brain aromatase (cyp19a1b) in initiating behavioural sex change, as its expression trailed behavioural changes. However, we find that isotocin (it, that regulates teleost socio-sexual behaviours) expression correlated with dominant male-specific behaviours in the bluehead wrasse, suggesting it upregulation mediates the rapid behavioural sex change characteristic of blueheads and other tropical wrasses. However, it expression was not sex-biased in temperate spotty and kyusen wrasses, where sex change is more protracted and social groups may be less tightly-structured. Together, these findings suggest that while key components of the molecular machinery controlling gonadal sex change are phylogenetically conserved among wrasses, neural pathways governing behavioural sex change may be more variable.

DIVERSIDAD Y DISTRIBUCIÓN DE PECES EN EL GRADIENTE DE PROFUNDIDAD DE UNA PARED ARRECIFAL CORALINA EN LA ISLA DE SAN ANDRÉS, CARIBE COLOMBIANO

“Blue Wall”, in San Andrés Island (Colombia), is an outer reef slope with an inclination that increases with depth to nearly 90°. Such a steep gradient facilitates the identification of patterns of variation in species abundance and diversity along depth. To document such patterns in fishes associated with this habitat, 30 visual censuses were conducted along 30 x 2 m transects, located at 5 m intervals between 5-30 m depth, in which the abundance and diversity of species was estimated. A total of 2916 individuals belonging to 46 species from 21 families were recorded within transects. Ten additional species were observed outside of transects for a total richness of 56 species. The dominant species were Canthigaster rostrata, Chromis cyanea, Stegastes partitus, Thalassoma bifasciatum and Clepticus parrae, which together with four other species accounted for 92% of the total abundance. Several of these dominant species are planktivorous and abundant throughout the Caribbean and had broad ranges of vertical distribution with abundance peaks in different parts of the depth gradient. In general, there was a positive correlation between average abundance and breadth of depth distribution. Non-metric Multi-Dimensional Scaling analysis revealed distinct assemblages at each depth, which also differed significantly, but weakly, in their diversity and dominance, but not in their species richness and evenness. Shallow assemblages were clearly distinctive from deep ones, with greater differentiation between shallower than between deeper assemblages. We conclude that the fish assemblage at “Blue Wall” exhibits a structural order that can be explained, in part, by depth and that reef walls offer an excellent opportunity to examine processes responsible for patterns of community structure in coral reef fishes.

Reef fish community in presence of the lionfish (Pterois volitans) in Santa Marta, Colombian Caribbean

ABSTRACT Objective. Fish species community structure and benthic organisms coverage were studied in five localities in Santa Marta where the lionfish is present. Materials and methods. Abundance of fish species, including lion fish, was established using 30 m random visual censuses and video transects; trophic guilds were established according to available references. On the other hand benthic coverage was evaluated using the software Coral Point Count (CPCe) 4.0. Results. Families with higher species numbers were Serranidae, Labridae, and Pomacentridae. Lionfish abundances were low (2.6±2.1 ind/120 m2), but in any case Pterois volitans was observed as the eleventh more abundant species, surpassing species of commercial value such as Cephalopholis cruentata. Species that were found in larger numbers (>100, Thalassoma bifasciatum, Haemulon aurolineatum, Canthigaster rostrata, Abudefduf saxatilis, Chromis cyanea, and Stegastes partitus) were mainly invertebrate eaters, planctivores, and territorial herbivores. Coral coverage showed higher coral percentages in Chengue (69.9%) and Cinto (27.4%), larger sponge percentages in Morro (32.7%); Isla Aguja and Remanso showed the larger figures for abiotic substrate (41.6 and 37%, respectively); corals, sponges, and gorgonians were the components best explaining fish community, but not for the lion fish, which inhabit all studied reef formations. Conclusions. Lion fish is ranked between the 20 more abundant species, with none commercially important species larger, hence no species may qualify as a natural control. Lion fish has as well become a relatively abundant species in Santa Marta reefs, independent of benthic coverage.