Mitochondrial DNA patterns describe the evolutionary history of the bonnethead shark Sphyrna tiburo (Linneus 1758) complex in the western Atlantic Ocean.

The apparent lack of physical barriers in the marine realm has created the conception that many groups have a constant gene flow. However, changes in ocean circulation patterns, glacial cycles, temperature, and salinity gradients are responsible for vicariant events in many fish species, including sharks. The bonnethead shark, Sphyrna tiburo, is an endangered small coastal shark species. Although considerable efforts have recently been undertaken, little remains known about the possible biogeographic scenario that can explain its actual distribution within the western Atlantic (WA). Here, we used 599 mitochondrial sequences to assess the phylogeographic structure and implement Bayesian phylogenetic analyses to obtain divergence times and reconstruct the ancestral geographic range. This allowed us to infer processes responsible for the diversification of S. tiburo into major divergent lineages. Our results indicated that S. tiburo in the WA represents three independent lineages, with Brazilian samples differentiated into a distinct genetic cluster. The posterior probability of ancestral range analysis indicated that the species likely originated in the northern region (Carolina Province and the southern Gulf of Mexico), where it colonized southward through the uplifting of the Central American Isthmus (CAI). The Northern and Caribbean genetic clusters appear to have arisen from the intensification of the Loop Current, which currently flows northward passing the Yucatan Peninsula, Gulf of Mexico, and east Florida. Following initial colonization, the Northeastern Brazil group differentiated from the Caribbean region due to the sediment and freshwater discharge of the Amazon-Orinoco Plume. Thus, the evolutionary history of the S. tiburo complex can be explained by a combination of dispersal and vicariance events that occurred over the last ~5 million years (MY). We established and confirmed the species and population limits, demonstrating that the Amazon-Orinoco Plume constitutes a significant dispersal barrier for coastal sharks. Finally, we discuss some recommendations for the conservation of the bonnethead shark.

A new species of the genus Verilus (Teleostei, Percomorpha, Acropomatidae) from Brazil.

A new species of Acropomatid fish, Verilus costai sp. nov., is described from a single locality off Belmonte, State of Bahia, Brazil. It resembles Verilus pseudomicrolepis (Schultz, 1940) from the Caribbean Sea. The two are considered vicariant and they are interpreted to be separated from other species of the genus Verilus by (amongst other characters) the presence of fangs on the dentary (vs. only villiform teeth), the anal fin formula (II+9 vs. III+7) and the naked occiput (vs. scaled). However, formal establishment of a separate genus is postponed until a complete phylogenetic review of the family has been performed. Verilus costai can be distinguished from V. pseudomicrolepis by its higher number of gill rakers (27-31 vs. 21-25), lower number of pseudobranchial filaments (15-23 vs. 21-28), shorter snout length (8.2-11.3 vs. 11.3-13.4 % of SL), and more compressed otoliths (OL:OH = 1.3-1.35 vs. 1.35-1.5). In addition, the fossil otolith-based species Verilus mutinensis (Bassoli, 1906) from the late Miocene to middle Pleistocene of the Mediterranean is thought to be related and indicates that in the past this group was more widely distributed than nowadays and comprised more vicariant species.

BRUVS reveal locally extinct shark and the way for shark monitoring in Brazilian oceanic islands.

Here we present records of sharks obtained using baited remote underwater stereo-video systems (stereo-BRUVS) at two Brazilian oceanic islands. Fourteen of the 60 deployments recorded 19 sharks in Trindade Island. In Saint Peter and Saint Paul Archipelago (SPSPA), two pelagic and two demersal deployments recorded two and one shark, respectively, including the locally extinct Galapagos shark Carcharhinus galapagensis. Stereo-BRUVS should be considered as adjuncts to other non-invasive methods to monitor shark populations.

New records of the snow bass Serranus chionaraia (Perciformes: Serranidae) confirm an established population in the Brazilian Province.

The snow bass Serranus chionaraia is a small-bodied reef fish presumed to be restricted to the Caribbean Province, with a single specimen captured south of the Amazon River mouth. Recent surveys with baited remote underwater stereo-video systems detected the species c. 1900 km southward. Meristic and morphometric characters of two specimens examined in this study confirmed the species identity, which greatly extends the species' range southward on the eastern coast of Brazil and indicates the presence of an established population of S. chionaraia in the Brazilian Province.

Marine tardigrades of the Bahamas with the description of two new species and updated keys to the species of Anisonyches and Archechiniscus.

This is the first survey of subtidal marine tardigrades from the Bahamas, and we compare our results with earlier studies of Bahamian intertidal habitats. In 2011 and 2014 we collected 60 subtidal sand samples from Bimini, the Berry Islands, New Providence, Eleuthera, and the Exumas. We found 11 species only one of which, Dipodarctus subterraneus (Renaud-Debyser, 1959), had been found in the previous intertidal Bahamian collections. Thus, 10 species are new records for the Bahamas, and four of these are new to science. We describe two of the new species (Archechiniscus bahamensis sp. nov. and Anisonyches eleutherensis sp. nov.). Additional material is needed for a conclusive identification of the undescribed species of Batillipes and Florarctus. Based on examination of the holotype of Anisonyches diakidius Pollock, 1975, we redescribe this species and give an emended diagnosis of the genus and the species. We also provide new keys to the species in the genera Archechiniscus and Anisonyches. A Chao2 species richness estimate indicated that our sampling effort was extensive and probably recovered most common species. Correlations of abundance and diversity indices with regard to depth, distance to nearest shore, and sediment grain size were not significant.

Mixing rates in weakly differentiated stocks of greater amberjack (Seriola dumerili) in the Gulf of Mexico.

The greater amberjack (Seriola dumerili) is a commercially and recreationally important marine fish species in the southeastern United States, where it has been historically managed as two non-mixing stocks (Gulf of Mexico and Atlantic). Mark-recapture studies and analysis of mitochondrial DNA have suggested the two stocks are demographically independent; however, little is currently known about when and where spawning occurs in Gulf of Mexico amberjack, and whether stock mixture occurs on breeding grounds. The primary objective of this study was to quantify stock mixture among breeding populations of amberjack collected from the Atlantic and Gulf of Mexico. Genetic data based on 11 loci identified very low, though statistically significant differentiation among Gulf of Mexico samples (GST = 0.007, [Formula: see text] = 0.009; all P = 0.001) and between reproductive adults collected from two spawning areas (GST = 0.007, [Formula: see text] = 0.014; all P = 0.001). Naïve Bayesian mixture analysis supported a single genetic cluster [p(S|data) = 0.734] whereas trained clustering (using Atlantic and Gulf spawning fish) gave the highest support to a two-cluster model (p(S|data) = 1.0). Our results support the argument that the genetic structuring of greater amberjack is more complex than the previously assumed two, non-mixing stock model. Although our data provide evidence of limited population structure, we argue in favour of non-panmixia among reproductive fish collected from the Gulf of Mexico and Florida Keys.

Reproductive biology of Sympterygia bonapartii (Chondrichthyes: Rajiformes: Arhynchobatidae) in San Matías Gulf, Patagonia, Argentina

This study estimates and analyses the reproductive parameters and cycle of Sympterygia bonapartii in San Matías Gulf, northern Patagonia, Argentina. A total of 827 males and 1,299 females were analysed. Males ranged from 185 to 687 mm of total length (TL) and females from 180 to 742 mm TL. Sexual dimorphism was detected; females were larger, heavier, exhibited heavier livers, wider discs and matured at lager sizes than males. Immature females ranged from 180 to 625 mm TL, maturing females from 408 to 720 mm TL, mature ones from 514 to 742 mm TL and females with egg capsules from 580 to 730 mm TL. Immature males ranged from 185 to 545 mm TL, maturing ones from 410 to 620 mm TL and mature males from 505 to 687 mm TL. Size at which 50% of the skates reached maturity was estimated to be 545 mm TL for males and 594 mm TL for females. According to the reproductive indexes analysed, S. bonapartii exhibited a seasonal reproductive pattern. Mating may occur during winter-early spring and the egg-laying season, during spring and summer.(AU)

El presente estudio estima y analiza los parámetros reproductivos y el ciclo reproductivo de Sympterygia bonapartii en el Golfo San Matías, Patagonia norte, Argentina. Se analizaron 827 machos y 1.299 hembras. Los machos midieron entre 185 y 687 mm de largo total (LT) y las hembras entre 180 y 742 mm LT. Se detectó dimorfismo sexual; las hembras fueron más grandes y pesadas que los machos y presentaron anchos de disco, pesos de hígado y tallas de madurez sexual mayores a los de los machos. Las hembras inmaduras midieron entre 180 y 625 mm LT, las hembras en maduración entre 408 y 720 mm LT, las maduras entre 514 y 742 mm LT y las hembras con cápsulas entre 580 y 730 mm LT. Los machos inmaduros midieron entre 185 y 545 mm LT, los machos en maduración entre 410 y 620 mm LT y los maduros entre 505 y 687 mm LT. La talla media de madurez sexual fue estimada en 545 mm LT para los machos y 594 mm LT para las hembras. De acuerdo con los índices reproductivos analizados, S. bonapartii se reproduce estacionalmente. El apareamiento ocurriría durante el invierno y la primavera y la temporada de puesta durante la primavera y el verano.(AU)

Reproductive biology of Sympterygia bonapartii (Chondrichthyes: Rajiformes: Arhynchobatidae) in San Matías Gulf, Patagonia, Argentina

ABSTRACT This study estimates and analyses the reproductive parameters and cycle of Sympterygia bonapartii in San Matías Gulf, northern Patagonia, Argentina. A total of 827 males and 1,299 females were analysed. Males ranged from 185 to 687 mm of total length (TL) and females from 180 to 742 mm TL. Sexual dimorphism was detected; females were larger, heavier, exhibited heavier livers, wider discs and matured at lager sizes than males. Immature females ranged from 180 to 625 mm TL, maturing females from 408 to 720 mm TL, mature ones from 514 to 742 mm TL and females with egg capsules from 580 to 730 mm TL. Immature males ranged from 185 to 545 mm TL, maturing ones from 410 to 620 mm TL and mature males from 505 to 687 mm TL. Size at which 50% of the skates reached maturity was estimated to be 545 mm TL for males and 594 mm TL for females. According to the reproductive indexes analysed, S. bonapartii exhibited a seasonal reproductive pattern. Mating may occur during winter-early spring and the egg-laying season, during spring and summer.

RESUMEN El presente estudio estima y analiza los parámetros reproductivos y el ciclo reproductivo de Sympterygia bonapartii en el Golfo San Matías, Patagonia norte, Argentina. Se analizaron 827 machos y 1.299 hembras. Los machos midieron entre 185 y 687 mm de largo total (LT) y las hembras entre 180 y 742 mm LT. Se detectó dimorfismo sexual; las hembras fueron más grandes y pesadas que los machos y presentaron anchos de disco, pesos de hígado y tallas de madurez sexual mayores a los de los machos. Las hembras inmaduras midieron entre 180 y 625 mm LT, las hembras en maduración entre 408 y 720 mm LT, las maduras entre 514 y 742 mm LT y las hembras con cápsulas entre 580 y 730 mm LT. Los machos inmaduros midieron entre 185 y 545 mm LT, los machos en maduración entre 410 y 620 mm LT y los maduros entre 505 y 687 mm LT. La talla media de madurez sexual fue estimada en 545 mm LT para los machos y 594 mm LT para las hembras. De acuerdo con los índices reproductivos analizados, S. bonapartii se reproduce estacionalmente. El apareamiento ocurriría durante el invierno y la primavera y la temporada de puesta durante la primavera y el verano.