The More the Merrier: Swarming as an Antipredator Strategy in the Mysid Neomysis Integer

Abstract

The swarming behaviour of a Baltic littoral mysid shrimp, Neomysis integer, was studied both in the presence and absence of a predator (European perch, Perca fluviatilis L.). I performed two kinds of laboratory experiments. First, the swarming tendency of mysids and the effect of swarm size on swarm choice were studied. Second, the ingestion rate of mysids was measured when feeding alone versus in a swarm. The results indicate that N. integer actively join swarms. The avoidance of the perch by N. integer individuals was stronger when there was a swarm present. Larger swarms were preferred over smaller ones regardless of presence or absence of the predator. The overall feeding rate was similar when feeding alone and in swarm, but predator cues reduced feeding rate only when the mysids were feeding alone. This study demonstrates the capability of N. integer to assess predation risk and social context and alter their behaviour accordingly.

Fortune favours the bold: a higher predator reduces the impact of a native but not an invasive intermediate predator

“…The current study indicates that when placed in the broader community, the impacts of M. salemaai , as natives or invaders, may be somewhat ameliorated by higher predators through a combination of direct and non‐consumptive mechanisms, whereas the impacts of invasive H. anomala may be primarily ameliorated via direct mechanisms. As studies have indicated that predator avoidance behaviour in gregarious mysids is more pronounced in individuals than in groups (Lindén ), the ecological consequences of direct and non‐consumptive effects will primarily relate to the group level. Further, the risk‐foraging trade‐offs that result from predator avoidance can result in reduced growth and fecundity (Lima ), and M. salemaai is only capable of producing one brood per year, whereas H. anomala can produce up to four (Minchin & Boelens ).…”

“…These mysids represent an ideal study system with which to explore higher order interactions as, generally, mysids are gregarious, group‐forming animals whose predatory efficacy is demonstrably related to their association with conspecifics (Hansson et al . ) which, in turn, can alter the non‐consumptive effects exerted by higher predators (Lindén ). More specifically, whilst congeners of M. salemaai have themselves been implicated as damaging invaders (Spencer, McCelland & Stanford ), H. anomala is also known to have severe ecological impacts (Ketelaars et al .…”

“…Here, we use a comparative functional response-based approach (Dick et al in press) (2005), exert different impacts on prey, as individuals, in conspecific groups and in conspecific groups in the presence of a higher fish predator, Gasterosteus aculeatus Linnaeus, 1758. These mysids represent an ideal study system with which to explore higher order interactions as, generally, mysids are gregarious, group-forming animals whose predatory efficacy is demonstrably related to their association with conspecifics (Hansson et al 2001) which, in turn, can alter the nonconsumptive effects exerted by higher predators (Lind en 2006). More specifically, whilst congeners of M. salemaai have themselves been implicated as damaging invaders (Spencer, McCelland & Stanford 1991), H. anomala is also known to have severe ecological impacts (Ketelaars et al 1999;Ricciardi, Avlijas & Marty 2011), and is a more voracious predator of multiple prey species than M. salemaai (Dick et al 2013).…”

Fish odour triggers conspecific attraction behaviour in an aquatic invertebrate

“…Some recent studies on aggregation preferences in crustaceans ended up with complex results (e.g. Baumgärtner et al 2002;Evans et al 2007;Linden 2007). The present study suggests that the presence of predator cues may influence the tendency to aggregate in invertebrates and should be considered in examinations referring to this problem.…”

Importance of seagrass vegetation for habitat partitioning between closely related species, mobile macrofauna Neomysis (Misidacea)

“…Previous studies have also suggested that mysid species may be facilitative, whereby the formation of mixed species aggregations confers benefits to each of the component species. Such benefits may include, maintaining a suitable position in a favorable habitat (Clutter, 1969;Ritz, 1994), energetic benefits (Hough & Naylor, 1992;Herskin & Steffensen, 1998;Ritz, 2000), increased food uptake (Eggers, 1976;Ritz, 2000), reduced predation risk (Ritz, 1994;Lindén, 2007), and facilitation of breeding (Clutter, 1969;Ritz, 1994).…”