Effects of temperature and the presence of benthic predators on the vertical distribution of the ctenophore Pleurobrachia pileus

Abstract

This study details the investigations of the effect of temperature and the presence of predators on the vertical distribution of the ctenophore Pleurobrachia pileus. Previous studies had suggested that P. pileus moves to the sediment when exposed to colder temperatures as an energy saving strategy. Although we did observe an effect of temperature on the movement of the ciliate combs, the effect of temperature on the average depth of animals in the water column was not significant, but a significant interaction was found between temperature and exposure time. In the presence of benthic predators or of water previously inhabited by these predators P. pileus changed its vertical distribution significantly, and moved away from the sediment, thus reducing the risk of being predated. We conclude that P. pileus can sense the presence of its predators, and changes its behaviour accordingly.

Benthic scavengers and predators of jellyfish, material for a review

“…Rasmussen 1973). Contrary to sea anemones, decapod crabs may be able to actively pursue jellyfish as has been reported by Esser et al (2004) for Pagurus bernhardus jumping up to capture P. pileus from the water column. Decapod crabs also are able to protect and defend their jellyfish prey, e.g.…”

Seasonal changes and population dynamics of the ctenophore Mnemiopsis leidyi after its first year of invasion in the Kiel Fjord, Western Baltic Sea

“…While during the low abundance period (March-June) the bulk of the population was concentrated in deep layers, during the outburst of the species (August-September) the vertical pattern shifted and the bulk of the population was located in the upper layers. Dense aggregation of the M. leidyi in deep layers are likely a population response to low temperatures, which have been found to constrain the reproductive potential and as an energy saving strategy of ctenophores (Esser et al 2004). The shift in the vertical pattern from bottom to upper layers matched with the temperature increase in late spring, which enhances the reproduction capacities of the species and allows a fast expansion in the water column.…”

Predator-induced vertical behavior of a ctenophore

“…In contrast to previously documented escape behaviors of M. leidyi, which occur post-encounter, vertical positioning may enhance survival by limiting predator encounters. Such avoidance behaviors are common among smaller pelagic crustaceans (Titelman & Fiksen, 2004) and have been suggested for the ctenophore Pleurobrachia pileus (Esser et al, 2004). M. leidyi populations may be dense both close to the bottom and the surface (Miller, 1974;Costello & Mianzan, 2003).…”

“…Responses, such as crumpling, to remote fluid disturbances also exist (Moss et al, 2004). In contrast, escape strategies such as migration and vertical habitat shelters in response to perceived risk are virtually unexplored for ctenophores (e.g., Esser et al, 2004), despite being widespread amongst zooplankton (e.g., reviews in Ohman, 1988;Hays, 2003), including scyphozoan jellyfish (Albert, 2011). Chemical cues from jellyfish can induce vertical behavior in crustacean zooplankton (McKelvey & Forward, 1995;Cohen & Forward, 2003).…”