Red bioluminescence in fishes: on the suborbital photophores of Malacosteus,Pachystomias and Aristostomias

Many deep-sea animals produce blue bioluminescence, but species of three genera of midwater dragonfishes also produce red light. In addition to numerous small body photophores, species of these genera (Malacosteus, Pachystomias and Aristostomias) have large suborbital photophores that emit red light and postorbital ones that emit blue light. Pachystomias microdon additionally has a red-emitting preorbital photophore. Fluorescence measurements from the intact suborbital photophores, and from their exposed cores, confirm the previous hypothesis that the red light emitted by Malacosteus is spectrally altered by a superficial shortwave cutoff brown filter. No such filter is present in the other two genera. Studies of the anatomy of the photophores show that the suborbital photophore of Malacosteus is similar in general organisation to other photophores, including the postorbital photophore. The red-emitting photophores of Pachystomias and Aristostomias, however, have a unique organisation, in which the bulk of the photophore comprises a gland that lies outside the thick reflector. Strands of tissue run from the gland into the photogenic core of the photophore through numerous pores in the reflector. The production and use of red light by these fishes is discussed in the context of these results.Electronic Supplementary Material Supplementary material is available for this article at     

Adsorption von Blei und Cadmium an Tonen

Clay minerals as major components of soils can adsorb heavy metals. The release of toxic heavy metals such as lead and cadmium into soil presents a serious problem. To evaluate the behaviour of these elements in the environment, it is necessary to develop methods which allow precise analysis of heavy metals. This article compares and optimizes AAS methods for lead and cadmium.     

Post-bloom grazing byCalanus glacialis,C. finmarchicus andC. hyperboreus in the region of the Polar Front,Barents Sea

The plankton community in the Polar Front area of the Barents Sea was investigated during a cruise from 14 to 28 July 1987. The colonial algaePhaeocystis pouchetii andDinobryon pellucidum dominated the phytoplankton. Depth integrated carbon assimilation rates varied from 190 to 810 mg C m^–2 d^–1. A high carbon:chlorophyll ratio (which varied from 123 to 352) prevailed at the three stations investigated, which may relate to facultative heterotrophic behaviour byD. pellucidum. The herbivorous zooplankton community was dominated byCalanus glacialis, C. finmarchicus, andC. hyperboreus. Maximum zooplankton biomass was found in the same depth strata as phytoplankton chlorophyll maximum. The herbivorous copepod populations did not display consistent day-night vertical migration patterns. Phytoplankton consumption rates of the various life stages were estimated from the turnover rate of plant pigments in the gut. The gut defecation rate constant (R) varied from 0.014 to 0.027 min^–1 at 0°C in copepodites (Stage II to adult female) ofC. glacialis, independent of developmental stage.Calanus spp. community carbon ingestion rates calculated from particulate carbon:chlorophyll ratios, were 10, 65 and 400% of daily phytoplankton carbon fixation rates at Stations 1, 2 and 3, respectively.     

Learning and natal host influence host preference,handling time and sex allocation behaviour in a pupal parasitoid

The host choice and sex allocation decisions of a foraging female parasitoid will have an enormous influence on the life-history characteristics of her offspring. The pteromalid Pachycrepoideus vindemiae is a generalist idiobiont pupal parasitoid of many species of cyclorrhaphous Diptera. Wasps reared in Musca domestica were larger, had higher attack rates and greater male mating success than those reared in Drosophila melanogaster. In no-choice situations, na?ve female P. vindemiae took significantly less time to accept hosts conspecific with their natal host. Parasitoids that emerged from M. domestica pupae spent similar amounts of time ovipositing in both D. melanogaster and M. domestica. Those parasitoids that had emerged from D. melanogaster spent significantly longer attacking M. domestica pupae. The host choice behaviour of female P. vindemiae was influenced by an interaction between natal host and experience. Female P. vindemiae reared in M. domestica only showed a preference among hosts when allowed to gain experience attacking M. domestica, preferentially attacking that species. Similarly, female parasitoids reared on D. melanogaster only showed a preference among hosts when allowed to gain experience attacking D. melanogaster, again preferentially attacking that species. Wasp natal host also influenced sex allocation behaviour. While wasps from both hosts oviposited more females in the larger host, M. domestica, wasps that emerged from M. domestica had significantly more male-biased offspring sex ratios. These results indicate the importance of learning and natal host size in determining P. vindemiae attack rates, mating success, host preference and sex allocation behaviour, all critical components of parasitoid fitness. Electronic Publication