Predator-prey systems of drifting seaweed communities offthe Tohoku coast, northern Japan, as determined by feeding habitanalysis of phytal animals

Abstract

We collected phytal animals (fauna associated with drifting seaweeds)off the Tohoku coast in northern Japan in May and June 1994 to examine their feeding habits. Phytal animals were assignedto the following three feeding habit groups: (i) carnivores preyingon crustaceans: a gammarid (Stenothoe sp.) and a decapodmegalops; (ii) omnivores feeding on crustaceans and pinnate diatoms:a cirripede (Lepas anserifera), three gammarids (Calliopius sp., Jassaslatteryi and J. marmorata), an isopod (Idotea metallica),a decapod crustacean (Planes cyaneus), a decapod megalopsand two caprellids (Caprella penantis and Caprella mutica);and (iii) herbivores grazing on pinnate diatoms, fucoids and seaweedsother than fucoids: three gammarids (Allorchestes angusta, Amphithoelacertosa and Perampithoe lindbergi), an isopod (Cymodocejaponica) and a polychaete (Platynereis bicanaliculata).Pinnate diatoms in the gut contents were composed mainly of Licmophora spp., Navicula spp., Nitzschia spp.and Cocconeis spp. and seaweeds other than fucoids (i.e. Ectocarpussiliculosus and Sphacelaria furcigera). The latter twoalgae seemed to be epiphytes on drifting seaweeds. These resultssuggest that phytal animals play an important role in drifting seaweed communitiesthrough trophic linkage with two primary producers (i.e. driftingseaweeds and the epiphytes growing on them).

Long-distance dispersal, low connectivity and molecular evidence of a new cryptic species in the obligate rafter Caprella andreae Mayer, 1890 (Crustacea: Amphipoda: Caprellidae)

“…Only 2 % of world amphipods are obligate rafters; most of them are facultative (see Thiel and Gutow 2005b). Regarding this study, only C. andreae, Hyale grimaldii (Mcgrath and Myers 1989;Ruffo 1993;Zakhama-Sraieb et al 2010), and I. metallica are obligate rafters that have been reported to be found exclusively on floating objects (Butler 1975;Gutow and Franke 2003;Sano et al 2003), and all previous records of C. hirsuta, E. brasiliensis, and Fig. 4 a Mitochondrial (COI) haplotypes network (90 % parsimony connection limit) of C. andreae.…”

“…Some of the most common marine invertebrates reported rafting are peracarid crustaceans (amphipods, isopods, and tanaids) (Sano et al 2003;Fraser et al 2011;Xavier 2011). All peracarids have direct development and, in many species, females provide extended parental care for their offspring (Thiel 2003).…”

Differential life history responses of two Idotea species (Crustacea: Isopoda) to food limitation

“…sea birds) (Furness & Todd 1984, Kirkman & Kendrick 1997, predators in the water below them (e.g. fish) (Dooley 1972, Shaffer et al 1995 and from co-occurring predators on the raft (Edgar 1987, Sano et al 2003. Furthermore, cannibalism on juveniles is common among idoteids and increases when alternative food is scarce (Franke & Janke 1998).…”

Behavioural and metabolic adaptations of marine isopods to the rafting life style

“…Benthic populations of I. metallica are not known even though the species is reported from coastal waters in many parts of the world (Miller 1968;Hartmann 1976;Sano et al 2003;Abello´et al 2004), probably as a consequence of inferiority in interspecific competition with benthic species (Gutow and Franke 2003). Apparently, rafting is a specific and evolutionarily developed life style of I. metallica.…”