Diel horizontal migration and swarm formation in Daphnia in response to Chaoborus

Abstract

Dense swarms of Daphnia longispina (up to 4000 animals 1 -I) were recorded along the littoral zone in a lake where Chaoborus flavicans is considered the main predator. D. longispina coexisted with D. pulex, but there were no D . pulex in the littoral swarms . Swarms were less dense at night (about 1/10 the density), and D. longispina exhibited diel horizontal migrations by aggregating in the littoral during the day and spreading out at night . Laboratory experiments showed that Chaoborus capture efficiency on juvenile daphnids was higher in the light compared to darkness, and that Daphnia exhibited a behavioural response to water that had previously contained Chaoborus . We conclude that predation from Chaoborus can be an important factor affecting the distribution patterns of Daphnia observed in this lake. The behavioural experiments indicated that this influence might be partly mediated by chemical agents .

Patch exploitation by planktivorous fish and the concept of aggregation as an antipredation defense in zooplankton

“…There are additional reasons why in a small lake, and in the middle of the day, the risk from visual predators may be reduced by aggregating to make it even more adaptive: (1) the numerical response of planktivorous fish in space is limited by the small size of the fish population residing in such a small habitat (fewer fish can assemble at the location which was also the case in our experimental setup); (2) the risk for a cladoceran prey of joining an aggregation is further reduced by the reluctance of individual fish to leave their daytime refuge in deeper strata or among littoral vegetation (in this case, the mass numerical response becomes reduced to a few fish that risk foraging outside the antipredation window- Clark and Levy 1988;Gliwicz et al 2006); (3) feeding by the small number of the hungriest fish within such an aggregation would probably be very inefficient with their attention being mainly focused on the mortal risk from visually feeding piscivores rather than on the opportunity offered by the abundant prey (such prioritization in fish behavior was first demonstrated in studies with a virtual kingfisher (Alcedo atthis) by Milinski and Heller 1978;Heller and Milinski 1979); and (4) small lakes and ponds are mostly shallow, thus precluding the use of diel vertical migrations as an alternate behavioral antipredation defense in zooplankton (De Meester et al 1999). Moreover, swarming sensu Ambler (2002) may also represent an effective defensive behavior in Daphnia against predation by invertebrates such as phantom midge (Chaoborus) larvae (Kvam and Kleiven 1995). These invertebrates lack great mobility-in contrast to fish-thus precluding the massive numerical response in space exhibited by roach in this study.…”

“…This may explain why swarming could be induced by fish kairomone treatment in Daphnia propagated at high density in the laboratory (Pijanowska and Kowalczewski 1997). It may also explain why aggregation by cladocerans has been occasionally observed in the field as dense swarms of Bosmina (Jakobsen and Johnsen 1988), Daphnia (Kvam andKleiven 1995), or Scapholeberis (De Meester et al 1991) that are always found in the middle of the day, and in small lakes or ponds, but not in larger lakes (where densities of a medium-sized Daphnia beyond 30 ind. L 21 are uncommon, and densities orders of magnitude higher are never reported).…”

“…To exclude the predation of Daphnia by invertebrate predators, the experimental setup was covered with mosquito netting to prevent egg deposition by phantom midge (Chaoborus) and other insects ( Fig. 1A), these representing a potential source of extraneous predation against which aggregating might be an effective defense (Kvam and Kleiven 1995). For each feeding session, the fish were transferred to each tank in a 1 liter steel bowl constituting the central part of the bottom of a cage made of nylon netting (5 mm mesh).…”

Predator‐specific inducible morphological defenses of a water flea against two freshwater predators

“…Inducible defenses are a ubiquitous phenomenon in many taxa, ranging from protists to vertebrates (Altwegg, Marchinko, Duquette, & Anholt, 2004; Frost, 1999), and are especially well studied in the model organism Daphnia (Lass & Spaak, 2003; Seda & Petrusek, 2011). Since they are prey for many different aquatic predators, Daphnia have evolved a broad range of inducible defenses, including changes in behaviour (Loose & Dawidowicz, 1994; Vetti Kvam & Kleiven, 1995), shifts in life history (Stibor, 1992), physiological responses (Weiss, Leese, Laforsch, & Tollrian, 2015) and changes in morphology (Tollrian, 1995b).…”

The trans-generational impact of population density signals on host-parasite interactions

“…Daphnia are well known for their plastic life-history and morphological responses to environmental parameters like predation [28, 29], pollutants [30], temperature [31, 32], salinity [33], and food stress [34, 35]. As an inhabitant of rock-pools and ponds, they also experience extensive and fast variation in population density across the season, with numbers ranging from a few females per cubic meter to up to 1000 Daphnia per litre [36, 37]. In response to signals of high density, Daphnia have been shown to reduce filter-feeding rates, growth and offspring number [38–40]; instead producing offspring of a larger size or switching to sexual reproduction in some circumstances [41].…”