engleski

Life history traits of the epigean populations of Niphargus dalmatinus (Crustacea: Amphipoda) along the Cetina River, Croatia

Very little is known about the epigean niphargid autecology. The aim of this study was to establish the life history traits of the endemic amphipod Niphargus dalmatinus, which regularly inhabits springs, epigean streams and rivers in the Middle Dalmatia. Three replicate samples were collected once a month with benthos net in the period from August 2004 to August 2005 at ten study sites located in the upper, middle and lower reaches of the Cetina River and its tributaries. The highest population density of the species was recorded on two study sites in hypocrenal zone, where the mean water temperature reached 9.7°C with the narrow range of 7.3-12.5°C. Ovigerous females were recorded year-round at the main spring and in the upper course, but were more numerous during the spring (March, April, May) and autumn (October) months. The sex-ratio (males vs. females) was in favour of males almost throughout the all study year. Mean number of eggs was 30 for 100 analysed females, but one female carried maximum of 111 eggs. There was no correlation between fecundity and female body size (total body length). A better insight into the life history strategy of N. dalmatinus will help to interpret the distribution patterns, population structures, and the coexistence with other crustacean species.

spring; hypocrenal; fecundity; ovigerous females; sex-ratio

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