Subterranean Fishes of the World

4713

2013

145 pages

Instituto dc Biociencias da Universidade de Sao Paulo. Departamento de Zoologia

Population ecology and behaviour of subterranean fishes, Rhamdia sp. n. e Ancistrus sp. n. from Serra da Bodoquena karstic area, Mato Grosso do Sui (Siluriformes: Heptapteridae, Loricariidae) This project studied aspects of the population ecology of two troglomorphic Siluriformes of genera Rhamdia and Ancistrus, which are syntopics in a subterranean stream of Serra da Bodoquena karst area, Mato Grosso do Sui. The research comprised the investigation of the population sizes and densities, survival rates, individual growth rate, frequency of standard length, weight and condition factor, and displacements. Adicionally, the behavior of Rhamdia sp. n. was investigated with focus on locomotor rhythmicity and reaction to light. Six collections were made between 2010 and 2011 to gather population data, based on visual census and mark-recapture, as well as search for other localities to investigate the distribution range of these species. The population size estimated to Rhamdia sp. n. was 391 individuals in Fadas Cave and 104 individuals in the Cinco dc Ouros Cave. The population densities of Ancistrus sp. n. suggests a lower population size compared to Rhamdia sp. n., possibly with less than 100 individuals in the studied area. The average population density estimated through visual census to Rhanidia sp. n. was 0.09 ind / m' in the Fadas Cave and 0.1 ind. I m' in the Cinco dc Ouros Cave, lower than the results estimated by mark-recapture, 0. 76 ind. / m' and 1.48 ind. I m', for each cave, respectively. To Ancistrus sp. n., the average population density was 0.018 ind / m'. The low variability throughout the year in population densities, weight, and in condition factor for both species in Fadas Cave, indicate and higher environmental stability in this cave compared to Cinco dc Ouros Cave. In Rhamdia sp. n., individuals without externally visible eyes (anophthalmics) showed higher survival rate compared to those with asymmetric or two normal eyes. The individual growth of Rhamdia sp. n. was heterogeneous with no relation to individuals' size and through the von Bertalanffy model estimate the maximum length (L m of 170 mm and growth constant (K) of 0.241. The median maximum longevity was 15 years. With little movement between sectors, individuals of Rhanidia sp. n. exhibited philopatry, while Ancistrus sp. n. moved around, with only one individual recaptured in the same cave sector. In relation do behavior Rhamdia sp n. showed significant circadian rhythmicity, with intra-specific differences in the spectral power values. In the study of light reduction, the intra-specific variation was observed in the degree of photophobia related to eyes morphology. Surveys conducted in 24 caves in the Campina settlement revealed that Rhamdia sp. n. occurs in the Fadas, Cinco dc Ouros, Manoel Cardoso and Dona Benedita caves, while Ancistrus sp. n. occurs only in the Fadas Cave. The mosaic of morphological variations observed in Rhanidia sp. n. and Ancistrus sp. n., the strong circadian locomotor activity and the high degree of photophobia observed in Rhamdia sp. n. suggests that these species are in early stages of setting troglomorphic characters, indicating a recent isolation in subterranean environment. Key-words: Subterranean fishes, population ecology, behavior, chronobiology, Mato Grosso do Sui, caves.

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