Detection of Zooplankton Prey in Squid Paralarvae with Immunoassay

Abstract

Sustainable management of economically important squid requires monitoring of changes in their abundance, which are related inter alia, to their success in the food chain. The highest mortality is expected in the paralarval stages, which are prone to starvation. Causes of starvation may be linked to the lack of suitable prey. A multiple detection system was developed for the simultaneous identification of five putative zooplankton prey in the guts of paralarval Chokka squid, Loligo vulgaris reynaudii, by employing polyclonal rabbit antisera in conjunction with solid phase immunoassays. Specificities of antisera were validated by ELISA screening against different zooplankton taxa. Cross-reactions observed with ELISA were minimized through manipulation of antibody and antigen concentrations resulting in more specific detection of target prey antigens when used in an immunodot assay. Application of this optimised immunoassay detected multiple predation in paralarval squid samples collected from diverse areas in the Agulhas Bank ecosystem on the south coast of South Africa.

Chokka squid (Loligo vulgaris reynaudii) abundance linked to changes in South Africa's Agulhas Bank ecosystem during spawning and the early life cycle

“…Chokka squid paralarvae seemingly prey mainly on copepods (Venter et al, 1999), of which two species are abundant around southern Africa, Calanoides carinatus, which dominates the cold Benguela upwelling system of the west coast, and Calanus agulhensis, which inhabits the warmer and relatively more stable waters of the Agulhas Bank (Huggett and Richardson, 2000). Irrespective of species, copepod biomass is generally greatest on the west coast.…”

“…Little is known about predation levels on squid paralarvae, but starvation may be a very important control. Chokka squid paralarvae are thought to feed mainly on copepods (Venter et al, 1999), whose spatial distribution and abundance is driven by the oceanography and concomitant primary production.…”

Diet Composition and Variability of Wild Octopus vulgaris and Alloteuthis media (Cephalopoda) Paralarvae: a Metagenomic Approach

“…However, a high proportion of stomach contents comprises unrecognizable soft material (Roura et al, 2012; Camarillo-Coop et al, 2013) or small pieces of exoskeleton (Passarella and Hopkins, 1991; Vecchione, 1991; Vidal and Haimovici, 1999). Alternative approaches have also been attempted: Specific prey species of Loligo reynaudii were detected by applying immunoassays (Venter et al, 1999) and in O. vulgaris paralarvae up to 20 different prey were detected cloning PCR products with group-specific primers (Roura et al, 2012). However, these methods are costly and time-consuming, and thus can only be applied to a limited number of samples and clones sequenced.…”

Identification of the Clam Species Ruditapes decussatus (Grooved Carpet Shell), Venerupis rhomboides (Yellow Carpet Shell) and Venerupis pullastra (Pullet Carpet Shell) by ELISA

“…These methods rely upon detection of species-specific proteins in samples, using antibodies raised specifically against them by immunization of laboratory animals Sotelo et al, 1993;Carrera et al, 1996;Venter et al, 1999).…”