Diet shifts of Rhizoprionodon terraenovae from the southern Gulf of Mexico: possible scenario by temperature changes

The current study examined the stomach contents of the Atlantic sharpnose shark (Rhizoprionodon terraenovae) in the southern Gulf of Mexico during 2015 to understand the relationship between diet and changes in sea surface temperature (SST). Prey-specific index of relative importance (%PSIRI), diet breadth (Bi), trophic level (TrL), and trophic overlap (PERMANOVA) were calculated between sexes, body size, and climatic seasons (dry, rainy and winter storm). The lowest temperature recorded in the area was during February (23.9°C), and the highest was during August (29.1°C). A total of 124 stomachs were analyzed, with 54.84% containing food. The trophic spectrum was composed of 32 identified prey, with demersal fish (Haemulon plumierii; %PSIRI = 22.82) and pelagic fish (Sardinella aurita; %PSIRI = 12.83) being the most important. According to the diet breadth (Bi = 0.002), Costello's graph, and trophic level (TrL = 4.2), R. terraenovae is a specialist tertiary consumer. PERMANOVA indicated significant trophic differences between sexes (F = 32.22; P < 0.05), body size (F = 13.68; P < 0.05), and among climatic seasons (F = 23.86; P < 0.05). Spearman's correlation indicated a negative relationship between the diversity of prey consumed by R. terraenovae and sea surface temperature (r = -0.75; P < 0.05). Therefore, diet for R. terraenovae is associated with SST, allowing for the development of possible scenarios related to climatic phenomena like climate change.

NUEVOS REGISTROS DE COPÉPODOS PARÁSITOS (COPEPODA: PANDARIDAE, EUDACTYLINIDAE, CALIGIDAE) EN CINCO ESPECIES DE TIBURONES (PISCES: ELASMOBRANCHIA) EN EL GOLFO DE MÉXICO

El presente estudio es parte de una investigación en curso de los copépodos parásitos de peces de las aguas costeras en el Estado de Campeche (sur del Golfo de México). El objetivo de este trabajo fue describir las especies de copépodos parásitos que se encontraron en cinco especies de tiburones: Carcharhinus leucas (Müller & Henle, 1839), Carcharhinus limbatus (Müller & Henle, 1839), Carcharhinus plumbeus (Nardo, 1827), Rhizoprionodon terraenovae (Richardson, 1836), y Sphyrna tiburo (Linnaeus, 1758). Aexcepción de R. terraenovae, todas las especies de tiburones estuvieron infectados al menos con una especie de copépodo. Un total de ocho especies de copépodos fueron encontrados: Nesippus orientalis Heller, 1865, Nemesis sp. y Paralebion elongatusWilson C.B., 1911 en C. leucas (n = 6); Tuxophorus caligodesWilson C.B., 1908, Lepeophtheirus longispinosus Wilson C.B., 1908 y Pandarus sinuatus Say, 1818 en C. limbatus (n = 9); Pandarus sp. en C. plumbeus (n = 4); y Eudactylina longispina Bere, 1936 en S. tiburo (n = 24). La ocurrencia de estas especies de copépodos en estos tiburones del Golfo de México constituye nuevos registros de hospedero y extienden su distribución geográfica conocida, y contribuye al conocimiento de la biodiversidad de los copépodos parásitos en México.