RESUMO
Large oceanic sharks represent a suitable model to investigate the influence of a host's oceanic conditions on the structure of its helminth communities. In this study, we describe the intestinal helminth fauna, and investigate determinants of infracommunity structure, in 39 specimens of shortfin mako Isurus oxyrinchus collected in the NE Atlantic. Six cestode species were found in the spiral valve of makos: 3 are typical from lamnid sharks, namely, gravid specimens of Clistobothrium montaukensis, Gymnorhynchus isuri and Ceratobothrium xanthocephalum, and 3 are immature specimens of cestode species common to several elasmobranchs, namely, Dinobothrium septaria, Nybelinia lingualis, and Phyllobothrium cf. lactuca. In addition, L3 larvae of Anisakis sp. type I were detected. Infracommunities were species poor and had low total helminth abundance. The result of Schluter's variance ratio test was compatible with the hypothesis of independent colonization of helminth taxa. These results conform to previous studies on oceanic predators that have hypothesized that these hosts should have depauperate and unpredictable helminth infracommunities because oceanic conditions hamper parasite transmission. However, mean species richness and mean total abundance of cestodes of shortfin mako and other oceanic sharks did not significantly differ from those of elasmobranchs from other habitats. This suggests that the large body size and prey consumption rates of oceanic sharks offset the negative 'dilution' effect of oceanic habitat on transmission rates. Additionally, or alternatively, parasites of oceanic sharks may have expanded the use of intermediate hosts through the trophic web to spread out the risk of failure to complete their life cycles.
Assuntos
Helmintíase Animal/parasitologia , Helmintos/classificação , Tubarões/parasitologia , Animais , Oceano Atlântico/epidemiologia , Helmintíase Animal/epidemiologiaRESUMO
The African Spur tortoise, Geochelone sulcata, has been introduced to Costa Rica. A total of 31 tortoises were measured for 26 gross morphometry parameters. All individuals measured were inmature, aged from 5 to 34 months, and were born in captivity in La Garita de Alajuela, Costa Rica. Mean straight carapace length was 83.1 mm, mean straight plastron length was 68.3 mm and mean maximum height was 46.2 mm. All the measurements were correlated, except tail length and cloacal distance. Weight had the highest positive allometry coefficient. All the variables were joined in two Principal Components; tail length and cloacal distance in Factor 2 and the rest of them in Factor 1. Lack of correlation among tail measures and the other variables as well as their inclusion in a different Factor could be related with an incipient development of sexual dimorphism characters
Se midieron 31 ejemplares de tortuga africana de espolones Geochelone sulcata para la realización de un estudio biométrico. Se consideraron 26 medidas morfológicas para cada individuo. Las tortugas tenían una edad de entre 5 y 34 meses, y ninguna había alcanzado la madurez sexual. Todas ellas habían nacido en cautiverio en La Garita de Alajuela, Costa Rica, donde son una especie introducida. La longitud recta del espaldar fue de 83.1 mm, la anchura recta del espaldar de 68.3 mm y la altura máxima media de 46.2 mm. Todas las medidas estaban correlacionadas entre sí, salvo la longitud de la cola y la distancia cloacal. El mayor coeficiente de alometría positiva correspondió a la variable Peso. El mayor coeficiente de alometría negativa correspondió a la anchura a nivel de los escudos gulares. Todas las variables se agruparon en dos componentes principales, la longitud de la cola y la distancia cloacal en el Factor 2 y el resto en el Factor 1. La falta de correlación de las medidas de la cola así como su inclusión en un factor aparte al resto de la muestra podría responder a un proceso incipiente de diferenciación sexual
Assuntos
Animais , Peso Corporal , Tartarugas/anatomia & histologia , Análise de Variância , Biometria , Costa Rica , Modelos Logísticos , Tartarugas/crescimento & desenvolvimentoRESUMO
The African Spur tortoise, Geochelone sulcata, has been introduced to Costa Rica. A total of 31 tortoises were measured for 26 gross morphometry parameters. All individuals measured were inmature, aged from 5 to 34 months, and were born in captivity in La Garita de Alajuela, Costa Rica. Mean straight carapace length was 83.1 mm, mean straight plastron length was 68.3 mm and mean maximum height was 46.2 mm. All the measurements were correlated, except tail length and cloacal distance. Weight had the highest positive allometry coefficient. All the variables were joined in two Principal Components; tail length and cloacal distance in Factor 2 and the rest of them in Factor 1. Lack of correlation among tail measures and the other variables as well as their inclusion in a different Factor could be related with an incipient development of sexual dimorphism characters.
