Hydrobiologia 434: 211–212, 2000. © 2000 Kluwer Academic Publishers. Printed in the Netherlands.
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Mixed multispecific schools of littoral Anomopoda (Crustacea: ‘Cladocera’) Alexey A. Kotov A. N. Severtsov Institute of Ecology and Evolution, Leninsky Prospect 33, Moscow 117071, Russia E-mail:
[email protected] Received 19 January 2000; in revised form 18 April 2000; accepted 10 May 2000
Key words: Anomopoda, ‘Cladocera’, behaviour, multispecific schools, Glubokoe Lake
Abstract Mixed multispecific schools of anomopod species were found in the open littoral of Glubokoe Lake (Moscow Region, Russia). Besides Scapholeberis, which formed the bulk of the schools, the schools contained Megafenestra, Ceriodaphnia, Pleuroxus, Chydorus and Alonella.
Introduction Aggregations of Scapholeberis mucronata, one of the most common school-forming anomopod (De Meester et al., 1993), have frequently been noted in Glubokoe Lake, Moscow Region, Russia (Sherbakov, 1967). In July 1996, I observed in the open littoral of this lake dense and compact aggregations of small-sized water fleas. On July 11, I collected a qualitative sample of water from one of these aggregations. In the course of laboratory study of this sample, I found that this aggregation was a mixed school of several anomopod species. On July 13, a new school, about 25 ñm in diameter, was observed. Animals occupied only the upper 7– 10 cm of water. The school was moving toward the pelagial and was located at a distance of c.15 m from the shore at the moment of its detection; the total depth was 1.2 m. Keeping in mind that it might be multispecific too, I sampled the school nucleus with the help of a 1 l vessel. For comparison, 20 samples (volume 5 l each) were collected by a Vovk planktonic sampler in the sub-surface water layer near the school. The same sampling pattern was applied to pelagic plankton. The sample from the school and the other samples were studied for the average density of different species. More aggregations were observed and sampled on July 19 and 22. However, these were monospecific.
Besides Scapholeberis, which formed the bulk of the schools of July 11 and 13, I recorded Megafenestra, Ceriodaphnia, Chydorus, Pleuroxus and Alonella (Table 1), which were absent or recorded incidentally in the sublittoral plankton and are more characteristic of the fauna of water at the shore or in vegetation (Smirnov, 1983; Korovchinsky, 1986) of Glubokoe Lake. Chydorus sphaericus sometimes penetrates the sublittoral (and pelagic!) plankton in a significant number, but this was not characteristic for July 1996. Polyphemus was not a component of the school, and undoubtedly arrived to attack anomopods in the aggregation. I think that multispecific schools can be multipreted as the accidental capture of some shore anomopods by a school of Scapholeberis. This was possibly aided by a similarity of individual behaviour of different anomopod species, or attraction by pheromones of Scapholeberis. Different explanations have been offered as causes of school formation in anomopod species, such as a concentration of gamogenetic specimens for reproduction (Ratzlaff, 1974), for feeding (Cuddington & McCauley, 1994) or protection against predators (De Meester et al., 1993) (respectively, ‘mating’, ‘coincidental’ and ‘survival’ groups according to Hamner, 1988). Mating swarms should be rejected, because there were no males or ephippial females in this school. This aggregation was not feeding group, since
212 Table 1. Density per 1 l of different species in the school, plankton of open littoral and pelagic plankton on July 13, 1996; + single individuals; – absent Species
School
Scapholeberis mucronata 1410 Ceriodaphnia pulchella 110 C. reticulata + C. quadrangula 9 Megafenestra aurita 49 Bosmina longirostris 12 Chydorus sphaericus 23 Pleuroxus truncatus 37 Alonella nana 5 A. excisa 12 Other Chydoridae gen. sp. + (Eurycercus lamellatus, Pleuroxus uncinatus, Graptoleberis testudinaria, Alona affinis, Acroperus harpae) Polyphemus pediculus 230
Plankton of Pelagic the open plankton littoral 0.1 4.3 + – 14.3 0.6 – – + +
– + + – – – – – – +
15.2
+
the guts of all animals were empty. Survival groups are characteristic of Scapholeberis (De Meester et al., 1993), and I think what exactly the protection against juvenile fish or Chaoborus (both are numerous in Glubokoe Lake in the summer (Shcherbakov, 1967)) caused the forming of the above-mentioned schools. It is remarkable that school formation in anomopods may be controlled by the same causes as in vertebrates (Manteifel, 1987). Mixed multispecific aggregations, characteristic for groups of vertebrates with complex behaviour (e.g. fishes (McKaye, 1981), tadpoles (Griffiths & Denton, 1992), birds, and ungulates) are now found in anomopods too, suggesting that small branchiopods may demonstrate complex collective behaviour.
Acknowledgements I am grateful to Prof. N. N. Smirnov and Prof. H. J. Dumont for criticism and linguistic corrections. This study is a continuation of long-term programm on the ‘Cladocera’ performed at the Hydrobiological Station ‘Lake Glubokoe’. The investigation is supported by a grant from the Russian Foundation for Basic Research (99-04-48969).
References Cuddington, K. M. & E. McCauley, 1994. Food-depend aggregation and mobility of the water fleas Ceriodaphnia dubia and Daphnia pulex. Can. J. Zool. 72: 1217–1226. De Meester, L., S. Maas, K. Dierckens & H. J. Dumont, 1993. Habitat selection and patchiness in Scapholeberis: Horizontal distribution and migration of S. mucronata in a small pond. J. Plankton. Res. 15: 1129–1139. Griffiths, R. A. & J. Denton, 1992. Interspecific associations in tadpoles. Anim. Behav. 44: 1153–1157. Hamner, W. M., 1988. Behaviour of plankton and patch formation in pelagic ecosystems. Bull. mar. Sci. 43: 752–757. Korovchinsky, N. M., 1986. Invertebrates of the littoral zone of Lake Glubokoe. Hydrobiologia 141: 83–88. Manteifel, B. P., 1987. Ekologicheskije i evolutsionnije aspekti povedinia zhivotnich. Nauka Publ., Moscow: 272 pp. (Ecological and evolutionary aspects of animal behavior. In Russian). McKaye, K. R., 1981. Natural selection and the evolution of interspecific brood care in fishes. In Alexander, R. D. & D. W. Tinkle (eds), Natural Selection and Social Behaviour. Blackwell Scientific Publishers, Oxford: 173–183. Ratzlaff, W., 1974. Swarming in Moina affinis. Limnol. Oceanogr. 19: 993–995. Shcherbakov, A. P., 1967. Ozero Glubokoe. Nauka Publ., Moscow: 379pp. (Lake Glubokoe. In Russian). Smirnov, N. N., 1983. Naselenije ureza vodi. In Smirnov, N. N. (ed.), Biotsenozi Mezotrofnogo Ozera Glubokogo. Nauka Publ., Moscow: 117–120 (Community of water’s edge. In Russian).
