engleski

Population dynamics of Synurella ambulans (Müller, 1846) (Crustacea, Amphipoda) in the hyporheic zone of the Sava River (Croatia)

Knowledge of population structure and dynamic in crustaceans is fundamental for the understanding of population ecology and protection of the aquatic ecosystems. The hyporheic zone (HZ) is a unique dynamic ecotone that is located at the interface of surface water and groundwater [1]. This habitat belongs to the groundwater connected ecosystems (GWCEs) which are threatened by human activities due to accumulation of pollutants in aquifers. Species Synurella ambulans is a small freshwater stygophilous amphipod inhabiting a relatively wide range of water bodies, including the HZ. The objective of the study was to determine population dynamic and reproductive biology in S. ambulans from HZ of the Sava River (sampling sites: Medsave and Jarun) sampled in December 2018, April, July and October 2019. The following life history traits were analysed: body length of individuals and sex ratio (female:male). The reproductive season of S. ambulans was determined to be in early spring (from March to April) because juveniles appeared during the spring (April 2019). The parenting generation died out after the spring season (May to June) and was subsequently replaced by juveniles which started to reproduce at the beginning of the following spring (March). In the Jarun study site the total body length (TBL) of adult females ranged between 3.38 and 6.00 mm (mean = 5.08 mm ; SD = 0.67), whereas in Medsave ranged between 4.13 and 6.38 mm (mean = 5.22 mm ; SD = 0.49), in all seasons. Adult male TBL ranged between 3.00 and 4.50 mm (mean = 3.57 mm ; SD = 0.32) in Jarun, and between 3.00 and 5.00 mm (mean = 3.68 mm ; SD = 0.40) in Medsave. Results revealed that mean body length of females was greater than that of males. These values were comparable to the literature data, where the maximum body length of females and males was found to be 7.0 and 4.7 mm, respectively [2]. Data on the sex ratio of S. ambulans indicate that males were more abundant than females in all seasons, while the opposite was found in populations from Poland [2]. Distinct seasonal trend in sex ratio throughout the sampling period was observed, ranging from 0.44:1 in October to 0.08:1 in July. Current results concerning the life cycle and reproduction of S. ambulans shed light on this poorly investigated species and its temporal dynamics in the vulnerable groundwater-connected habitat. ACKNOWLEDGMENTS The financial support of the European Regional Development Fund for the Qua/Qua Protein project (KK.01.1.1.07.0023) and of Croatian Science Foundation for the AQUAMAPMET project (IP-2014-09-4255) are acknowledged. We are grateful to Mr. Ivica Barač for his great help in the field work. REFERENCES [1] T. Orghidan, Bul. Stiint. Sect. Biol. Stiinte Agric. Sect. Geol. Geog. 7 (1955) 657–676. [2] A. Konopacka, M. Błazewicz-Paszkowicz, Pol. Arch.Hydrobiol. 47 (2000) 597–605.

groundwater connected ecosystems ; reproductive biology ; seasonality ; total body length ; sex ratio

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