Behavior of Gammarus aequicauda (Crustacea, Amphipoda) during predation on Artemia (Crustacea, Anostraca): New experimental results

Abstract

Gammarus aequicauda and Artemia spp. are abundant crustacean species in Crimean hypersaline lakes. G. aequicauda preys on Artemia but there was no quantitative data on this before the current study. Predation of G. aequicauda on adult Artemia was studied in experiments with two different approaches evaluating (a) the time balance of the feeding process and (b) the grazing intensity. The threshold prey concentration, when consumption began to increase with increasing concentration, was approximately 15 ind./L in 200-ml vessels and about 5 ind./L in 500-ml vessels. When the Artemia abundance reached 20-25 ind./L, there was no further influence on the gammarid consumption rate. There was a significant negative correlation between the consumption rate of gammarids and Artemia abundance. According to study results, an individual G. aequicauda may eat up to 20-24 Artemia/day. Our study suggests that (a) G. aequicauda is an omnivorous species and can significantly suppress populations of its prey. (b) The two experimental approaches used to study the feeding of gammarids on Artemia produced similar results, and both may be used to quantitatively assess relations in a "prey-predator" system. (c) The abundance of predators and prey, as well as the experimental vessel volume, may influence the feeding rate. (d) The presence of plant food resources such as the leaves of Ruppia does not influence on the predatory feeding rate of G. aequicauda. (e) The rate of prey consumption by G. aequicauda is not constant and depends nonlinearly on prey and predator abundance. (f) Cannibalism occurs in the presence of plant resources only, but not in the presence of Artemia. (g) Other gammarids react to the capture of Artemia by one of them. They swim up to the successful individual and try to take some part of the prey.

CanGammarus aequicauda(Amphipoda) suppress a population ofBaeotendipes noctivagus(Chironomidae) in a hypersaline lake? A case of Lake Moynaki (Crimea)

“…The general conclusion from this follows that the role of G. aequicauda in the regulation of the number of chironomid larvae depends on their abundance and the characteristics of the habitats. At the same time, as noted earlier (Remy et al., 2017; Shadrin et al., 2020a,2020b), the populations of G. aequicauda cannot exist and reproduce without animal food at all, like as some other Gammarus species (Dick, 1995; Ironside et al., 2019; Remy et al., 2017). Cannibalism was observed in Gammarus if animal food was absent (Dick, 1995; Ironside et al., 2019; Shadrin et al., 2020a).…”

“…Using our data (see above), the authors considered the time balance of G. aequicauda when feeding on chironomid larvae (Shadrin et al., 2020a):where T is the total time spent on searching (T 1 ), eating (T 2 ) and digesting (T 3 ) of one prey by a predator.…”

“…No such decrease of chironomid abundance was observed in the Ruppia thickets. Previously, it was shown that G. aequicauda consumes both Ruppia leaves and planktonic crustaceans in the lake (Shadrin et al., 2020a,2020b). Probably, in Ruppia thickets, their leaves with epibionts, both living and dead, play the main role in the composition of the gammarus diet.…”

“…For a long time, gammarids have been mentioned as belonging to the feeding group of the ‘shredding’, consuming plant and algal biomass, detritus and associated microbes (Friberg & Jacobsen, 1994; Gayte & Fontvieille, 1997; Greze, 1968). Recently, based on results of experiments and gut content analyses, different gammarid species are regarded as omnivores or predators with a broad spectrum of consuming prey organisms (Krisp & Maier, 2005; Maier et al., 2011; Pellan et al., 2016; Shadrin et al., 2020a,2020b; Shadrin, Yakovenko et al., 2019; Syrovatka et al., 2020). In the Crimean hypersaline waterbodies, the gammarid Gammarus aequicauda (Martynov, 1931) lives, often in great numbers, and is promising to use in aquaculture (Biandolino & Prato, 2006; Guerra‐García et al., 2017; Harlioğlu & Farhadi, 2018; Shadrin et al., 2020b).…”

“…In the Crimean hypersaline waterbodies, the gammarid Gammarus aequicauda (Martynov, 1931) lives, often in great numbers, and is promising to use in aquaculture (Biandolino & Prato, 2006; Guerra‐García et al., 2017; Harlioğlu & Farhadi, 2018; Shadrin et al., 2020b). In recent years, it has been shown that this species can intensively consume various types of planktonic animals, suppressing the development of their populations in the Crimean hypersaline waterbodies (Shadrin et al., 2020a,2020b; Shadrin, Yakovenko et al., 2019). The purpose of this work was, after conducting experimental and field studies, to answer the question: Can G. aequicauda effectively feed on chironomid larvae and to some extent influence the development of benthic animal populations, in particular chironomid larvae?…”