L. Forró szerk.: Miscellanea Zoologica Hungarica 9. 1994 (Budapest, 1994)

Forró, L.: Distribution and occurrence of Daphnia atkinsoni Baird, 1859 and Daphnia similis Claus, 1876 (Crustacea, Anomopoda) in Hungary

Body size and number of eggs Table 1 shows body size for both species in different months. These results correspond more or less to the size range given by Hrbácek (1987) for these taxa. Parthenogenetic females of D. atkinsoni had largest body size in March, while ephippial females were largest in June. The shell spine was longer in June than in the spring. Largest body size for D. similis was found in April. The shell of this species was longest in June usually, while it was short in March. Specimens from larger and deeper waters had shorter spines, and it was longer in a population from a very shallow pool. The number of eggs varied between 2 and 29 in D. similis, the greatest number was found mostly in March, it was changing between 10 and 26. In June was it much smaller, varying between 2 and 7. D. atkinsoni had higher number of eggs. Maximal numbers were found in March, in the population from Nagykunsági puszta it varied between 24-61, while in samples from Balmazújváros and Kelemenszék between 13 and 44, averages were 21 and 40, respectively. The clutch size was much smaller in June, changing between 9 and 16. Table 1. Body length (mm) and proportion of shell spine to total length (in parentheses) of Daphnia atkinsoni and D. similis Daphnia atkinsoni Daphnia similis March April parth. female 2.529 (18) 2.338 (17) 3.575 (20) 2.913 (17) 3.750 (25) 2.944 (18) ephip. female 2.061 (18) 2.369 (18) 2.369 (18) male 1.569 (25) June 3.686 (23) 2.646 (30) 2.695 (31) 2.870 1.673 (30) parth. female ephip. female March 3.076 (19) 4.073 (22) 4.270 (30) male April June 3.489 (35) 3.169 (26) 4.843 (37) 3.366 (33) 3.953 (35) 3.107 (28) 3.181 (32) 1.981 (26) Environmental conditions One characteristic feature of most waters sampled was that they were turbid and shallow, some of them only a few centimeters deep. In some cases the two species occurred in the same sample, however, based on the pH and conductivity, they seem to be different in their habitats. D. atkinsoni was found in a relatively high pH range (7.99-9.09) and in more saline waters, the conductivity range I recorded was 91-2260 pS. D. similis was found between 91-1260 jiS, with most sites below 1000 |nS. The sampling site of the lowest conductivity was at Furta, 21. 03. 1991, where both species occurred. Accompanying fauna Temporary pools have a characteristic Branchiopoda fauna, and the two Daphnia species under consideration belong to this group. Branchinecta ferox, Streptocephalus torvicornis, Triops cancriformis very often co-occurred, of the Anomopoda more frequently two Moina (M. brachiata, M. macrocopa), in some cases both species, and Macrothrix hirsuticornis were found in the samples containing D. atkinsoni and/or D. similis. These communities are very similar to those reported by e. g. Hollwedel (1975) and Hudec (1981).