Ontogeny of Copepod Predation in Juvenile Squid (Loligo opalescens)

Abstract

Copepods are the major prey of juvenile squid, and small species of squid such as Loligo opalescens face a great challenge in catching these erratically moving crustaceans. We studied the ontogeny of copepod predation in laboratory-reared animals and found that mastery of copepod capture develops progressively, starting shortly after hatch with strong attacks of a simple type. Modifications of the initial basic attack lead to more specialized strategies that effectively extend the range of capture to both longer and shorter distances. This progression culminates, by approximately 40 days post-hatching, in adult-like prey capture behavior involving tentacle extension and retraction. Squid raised exclusively on easily captured Artemia nauplii and introduced to a copepod diet 40 days after hatching displayed only basic attack behavior, characteristic of very young squid. All of these attacks were unsuccessful, and very few of these animals survived the transition. Copepod capture thus appears to be a skill that must be acquired in an experience-dependent manner early in post-hatching life.

Aperture effects in squid jet propulsion

“…These sequential jets were angled so the squid traced a circular path through the water, as though following a racecourse. The direction of swimming during circular jets was always fins-first, unlike the slower lateral circling in which paralarval D. opalescens orient arms-first toward their prey, orbiting it as the moon orbits the earth (Chen et al, 1996). Both circular jetting and fast single jets could represent escape behavior, although they often occurred without any startling stimulus that was obvious to the observer.…”

Embryonic life of the loliginid squid Loligo vulgaris: comparison between statoliths of Atlantic and Mediterranean populations

“…Embryonic incubation in the laboratory at cool temperatures (mean 12.2°C) produced Loligo vulgaris hatchlings that were significantly heavier (8%) and longer (7%) than embryos incubated at warmer temperatures (mean 19.5°C) (Villanueva 2000a). Larger L. vulgaris hatchlings probably have an initial competitive advantage due to their greater swimming power, which may enhance food-searching and prey-capture capacities (Packard 1969, Chen et al 1996, Villanueva et al 1996, making them less vulnerable to small predators. Thus, a compromise between the risks of long versus short embryonic incubation duration, and the resulting hatchling size and hatchling competence, probably exists.…”

Ontogeny of mantle musculature and implications for jet locomotion in oval squidSepioteuthis lessoniana

“…For example, at hatching, cephalopod molluscs are broadly similar in form to adults (Boletzky, 1974;Sweeney et al, 1992), yet these tiny hatchlings may grow several orders of magnitude in size, shift from the neuston or plankton to the benthos or nekton (Marliave, 1980;Hanlon et al, 1985) and may use different mechanisms to capture prey (O'Dor et al, 1985;Chen et al, 1996;Kier, 1996) and for locomotion (Villanueva et al, 1995;Kier, 2001a,b, 2002). In many cases, these life cycle changes are correlated with physiological and morphological changes that may have important effects on the locomotor performance or ecology of the animal.…”