Habitat use,seasonality and demography of the broadnose sevengill shark Notorynchus cepedianus in central Patagonia: Another piece of the puzzle

The habitat use, seasonality and demography of the broadnose sevengill shark Notorynchus cepedianus were investigated in central Patagonia, where a data gap exists for the species. Catch and effort and video‐derived indices indicated high relative abundance of sharks during warm months. Video stations revealed differences in the spatial use by sharks, being more frequently observed in the inner section of the bay. Complementary tagging efforts evidenced both a seasonal residence pattern and site fidelity between consecutive warm seasons. Juveniles outnumbered adults, which suggests that they may use the study area as a secondary nursing ground. Evidence from spontaneous regurgitation further suggests that prey abundance may be driving the seasonal occurrence of sharks in the region. This study allows for a more comprehensive understanding of the population structure and dynamics of sevengill sharks in the Southwest Atlantic. Abstract in Spanish is available with online material.     

First record of Terpios fugax Duchassaing and Michelotti, 1864 (Demospongiae: Suberitidae) in the Eastern Pacific Ocean

ABSTRACT

The brightly blue shallow water species Terpios fugax Duchassaing and Michelotti, 1864 was originally described from the Caribbean and has been extensively recorded in the Atlantic Ocean, but rarely found in the Indian and Pacific Oceans. In the Pacific Ocean it has been only reported from Sulawesi, Indonesia and from the Caroline and Marshall Islands. Here we report the first record of Terpios in the Eastern Pacific, based on the presence of T. fugax at Caldera, Región de Atacama, northern Chile. Although this species may have been inadvertently introduced to the area by human activity, it should also be considered that the geographically distant populations of this sponge (from the Caribbean to the Eastern Pacific) may represent different species.     

Residency of the scalloped hammerhead shark (<Emphasis Type="Italic">Sphyrna lewini</Emphasis>) at Malpelo Island and evidence of migration to other islands in the Eastern Tropical Pacific

Sixty nine hammerhead sharks, Sphyrna lewini, were tagged at Malpelo Island (Colombia) with ultrasonic transmitters during March 2006, 2007 and 2008, as part of a study to understand their residency at the island and their horizontal and vertical movements. Five sharks visited Cocos Island, 627 km distant from Malpelo. One of the sharks that appeared at Cocos Island also visited the Galapagos Islands, 710 km from Cocos, a month later. There is connectivity of Sphyrna lewini between Malpelo, Cocos and the Galapagos Islands, but the frequency of movements between the islands appears to be relatively low (<7% of the tagged sharks). The most common depth at which the sharks swam coincided with the thermocline (rs = 0.72, p < 0.01). The depth of the thermocline varied depending on the time of the year. Nocturnal detections of the sharks were more frequent during the cold season than during the warm season (W = 60, p < 0.01). We also found that hammerheads spent significantly more time on the up-current side of the island (Kruskal-Wallis = 31.1008; p < 0.01). This study contributes to the knowledge of hammerhead sharks not only in Malpelo Island but also at a regional level in the Eastern Tropical Pacific.     

First record of dicephalia in a bull shark Carcharhinus leucas (Chondrichthyes: Carcharhinidae) foetus from the Gulf of Mexico,U.S.A.

The first recorded incidence of dicephalia in a bull shark Carcharhinus leucas is reported from a foetus collected by a fisherman in the Gulf of Mexico near Florida, U.S.A. External examination, Radiography and magnetic resonance imaging revealed a case of monosomic dicephalia where the axial skeleton and internal organs were found to divide into parallel systems anterior to the pectoral girdle resulting in two well‐developed heads.     

Phylogeography of the flag cabrilla Epinephelus labriformis (Serranidae): implications for the biogeography of the Tropical Eastern Pacific and the early stages of speciation in a marine shore fish

Aim To examine the role of previously described biogeographical boundaries in shaping phylogeographical relationships within and among two putative eastern Pacific sibling species, the flag cabrilla, Epinephelus labriformis and the Clipperton grouper, Epinephelus clippertonensis (Serranidae). Location Tropical Eastern Pacific (TEP). Methods Sequence data from the mitochondrial cytochrome b gene were obtained from samples throughout the range of the species. Coalescence analysis, mismatch distributions and an analysis of molecular variance (amova ) were used to infer population differentiation. Results Overall, 49 haplotypes were found among 304 specimens, and there was significant structure corresponding to geographical locality (amova , Φ_ct = 0.198, P < 0.001; Φ_st = 0.207, P < 0.001; F_st = 0.169, P < 0.001; F_ct = 0.151, P = 0.036). Coalescence analysis indicates a population expansion at Clipperton Atoll during the mid‐Pleistocene. Main conclusions Our results suggest that previously described barriers to dispersal along the mainland of the TEP may not impinge on the dispersal ability of marine species, such as these groupers, that have long‐lived pelagic larvae. In contrast, gene flow between mainland and island populations of the readily distinguishable morphospecies E. labriformis and E. clippertonensis is restricted. The low level of genetic differentiation between the two species indicates that changes in external colour patterns may evolve more rapidly than genetic markers commonly used to delimit species boundaries. Thus a combination of colour differences and a lack of reciprocal monophyly may act as good indicators of incipient speciation in the marine environment.