Trophic structure on the West Antarctic Peninsula shelf: Detritivory and benthic inertia revealed by delta(13)C and delta(15)N analysis

Summer bloom-derived phytodetritus settles rapidly to the seafloor on the West Antarctic Peninsula (WAP) continental shelf, where it appears to degrade relatively slowly, forming a sediment ""food bank"" for benthic detritivores. We used stable carbon and nitrogen isotopes to examine sources and sinks of particulate organic material (POM) reaching the WAP shelf benthos (550-625 m depths), and to explore trophic linkages among the most abundant benthic megafauna. We measured delta(13)C and delta(15)N values in major megafaunal taxa (n = 26) and potential food sources, including suspended and sinking POM, ice algae, sediment organic carbon, phytodetritus, and macrofaunal polychaetes. The range in delta(13)C values (> 14 parts per thousand) of suspended POM was considerably broader than in sedimentary POC, where little temporal variability in stable isotope signatures was observed. While benthic megafauna also exhibited a broad range of VC values, organic carbon entering the benthic food web appeared to be derived primarily from phytoplankton production, with little input from ice algae. One group of organisms, primarily deposit-feeders, appeared to rely on fresh phytodetritus recovered from the sediments, and sediment organic material that had been reworked by sediment microbes. A second group of animals, including many mobile invertebrate and fish predators, appeared to utilize epibenthic or pelagic food resources such as zooplankton. One surface-deposit-feeding holothurian (Protelpidia murrayi) exhibited seasonal variability in stable isotope values of body tissue, while other surface- and subsurface-deposit-feeders showed no evidence of seasonal variability in food source or trophic position. Detritus from phytoplankton blooms appears to be the primary source of organic material for the detritivorous benthos; however, seasonal variability in the supply of this material is not mirrored in the sediments, and only to a minor degree in the benthic fauna. This pattern suggests substantial inertia in benthic-pelagic coupling, whereby the sediment ecosystem integrates long-term variability in production processes in the water column above. Published by Elsevier Ltd.

Immature stages of Calycopis bellera (Hewitson) and C-janeirica (Felder) (Lepidoptera, Lycaenidae, Theclinae, Eumaeini): Taxonomic significance and new evidence for detritivory

Details of egg, larval, and pupal morphology are described and illustrated for Calycopis bellera (Hewitson) and C. janeirica (Felder), with a special emphasis on larval chaetotaxy. Wild-caught Calycopis females laid eggs on dead leaves in the laboratory, and the caterpillars successfully completed development on an artificial agar diet to which no leaves were added. Males and females of the sexually dimorphic C. bellera had been previously placed in different genera or different species groups. Calycopis janeirica had been chronically misidentified (and misspelled C. jeneirica). Males and females of this species appear to be correctly associated for the first time. Whereas C. bellera has five larval instars-as reported previously for C. caulonia-C. janeirica has four. Morphological characters of the immatures of C. bellera and C. janeirica are summarized in a table and compared with those of other reared Calycopis species.