Costs and benefits of surplus offspring in the lesser kestrel (Falco naumanni )

Lesser kestrels (Falco naumanni) lay clutches which appear excessive as only 3% of them yield as many young as eggs laid. Four hypotheses may explain the adaptive value of producing surplus eggs: (1) the bet-hedging hypothesis assumes that the environment varies unpredictably and surplus eggs serve to track uncertain resources; (2) the ice-box hypothesis suggests that surplus offspring serve as a reserve food during a period of shortage; (3) the progeny choice hypothesis says that parents produce surplus offspring in order to choose these with higher fitness; and (4) the insurance-egg hypothesis proposes that extra eggs are an insurance against the failure of any egg. To test the significance of this strategy in the lesser kestrel, an experiment manipu-lating brood size at hatching was carried out over 2 years, with good and bad feeding conditions. The experiment consisted of adding a chick to experimental broods where one egg failed to hatch or removing a randomly selected chick from experimental broods where all eggs had hatched. Independently of annual food availability, pairs with brood sizes reduced by one chick fledged more nestlings than pairs with brood size equalling their clutch sizes. Body condition of young was also better in the former group, but only in 1993 (a high-food year). Independently of year, mean local survival of parents with complete broods at hatching was lower than for parents raising reduced broods. These results supported only the insurance-egg hypothesis which says that surplus eggs may be an insurance against the failure of any egg, but parents may suffer reproductive costs when all eggs hatch. Received: 17 January 1997 / Accepted after revision: 27 April 1997     

Removal of the herbicide amitrole from water by anodic oxidation and electro-Fenton

Here we demonstrate that an aqueous solution of the herbicide amitrole can be completely depolluted at pH 3.0 by anodic oxidation and electro-Fenton process. Anodic oxidation gives faster degradation with a boron-doped diamond anode than with a Pt anode. Electro-Fenton with a Pt anode and 1 mmol l ^–1 Fe²⁺ as catalyst yields the quickest depollution. Amitrole decay always follows a pseudo first-order reaction. NO₃^– and NH₄⁺ are accumulated in the medium during mineralization, although volatile N-products are also formed. These environmentally friendly electrochemical treatments could be applied to the remediation of wastewaters containing amitrole.     

Innate immune defense of the sponge<Emphasis Type="Italic"> Suberites domuncula</Emphasis> against gram-positive bacteria: induction of lysozyme and AdaPTin

Sponges are filter feeders that are exposed to large amounts of bacteria present in their surrounding aqueous milieu. The characteristic cell wall component of gram-positive bacteria, peptidoglycan (PPG), was used as a model molecule to study the responsiveness of cells from the marine demosponge Suberites domuncula toward gram-positive bacteria. The sponge lysozyme, which hydrolyzes PPG, was isolated from the living sponge; in addition its gene was cloned (SDLYS) and expressed in Escherichia coli. Antibodies were raised against the recombinant protein to demonstrate that in the Western blot both molecules give the same signal. In situ hybridization with SDLYS as a probe showed that cells in the mesohyl, the gray cells, strongly react with SDLYS. Subsequent immunofluorescence studies with antibodies raised against lysozyme revealed that only bacteria react with anti-lysozyme and only those that are scattered within the mesohyl of the tissue. An adaptor gene (AdaPTin-1) was isolated from the same sponge species that encodes a putative protein involved in endosome formation. Based on its differential expression we conclude that sponge cells react to PPG with a rapid activation of endocytosis, followed by the release of lysozyme.Communicated by O. Kinne, Oldendorf/LuheThe cDNA sequences from Suberites domuncula have been deposited (EMBL/GenBank): cDNA for the lysozyme (SDLYS) under the accession number AJ699166 and the AdaPTin-1 cDNA (SDAP1) under AJ699167.     

Is benthic trophic structure affected by food quality? The Dogger Bank example

The aim of this study was to evaluate the relationship between food quality and trophic structure of macrobenthic communities of the Dogger Bank. Therefore, 21 stations along different depth gradients (a transect across the central Dogger Bank and at a station cross in the north-eastern part) were sampled and analysed for macrofauna trophic structure and food supply, indicated by phytopigment composition and organic matter contents of the sediment. The study revealed differences in the trophic structure of the benthic community in areas with contrasting food supply. The trophic structure reflected differences in relative quality of organic matter. The sandy sediments on top of the bank receiving intermediate quantities of high food quality were inhabited by high abundances of interface feeders and sand-licking amphipods of the genus Bathyporeia. The southern stations characterised by a comparatively high amount of intermediate food quality were dominated by interface feeders such as Amphiura filiformis. The northern and north-eastern stations showing the highest diversity of feeding types were characterised by a comparatively low, but highly variable input of intermediate-quality organic matter consisting of both fresh and degraded organic matter. Results are discussed with a special emphasis on specific Dogger Bank features such as benthic primary production and frontal system characteristics.Communicated by O. Kinne, Oldendorf/Luhe     

Crinoid phylogeny: a preliminary analysis (Echinodermata: Crinoidea)

We describe the first molecular and morphological analysis of extant crinoid high-level inter-relationships. Nuclear and mitochondrial gene sequences and a cladistically coded matrix of 30 morphological characters are presented, and analysed by phylogenetic methods. The molecular data were compiled from concatenated nuclear-encoded 18S rDNA, internal transcribed spacer 1, 5.8S rDNA, and internal transcribed spacer 2, together with part of mitochondrial 16S rDNA, and comprised 3,593 sites, of which 313 were parsimony-informative. The molecular and morphological analyses include data from the bourgueticrinid Bathycrinus; the antedonid comatulids Dorometra and Florometra; the cyrtocrinids Cyathidium, Gymnocrinus, and Holopus; the isocrinids Endoxocrinus, and two species of Metacrinus; as well as from Guillecrinus and Caledonicrinus, whose ordinal relationships are uncertain, together with morphological data from Proisocrinus. Because the molecular data include indel-rich regions, special attention was given to alignment procedure, and it was found that relatively low, gene-specific, gap penalties gave alignments from which congruent phylogenetic information was obtained from both well-aligned, indel-poor and potentially misaligned, indel-rich regions. The different sequence data partitions also gave essentially congruent results. The overall direction of evolution in the gene trees remains uncertain: an asteroid outgroup places the root on the branch adjacent to the slowly evolving isocrinids (consistent with palaeontological order of first appearances), but maximum likelihood analysis with a molecular clock places it elsewhere. Despite lineage-specific rate differences, the clock model was not excluded by a likelihood ratio test. Morphological analyses were unrooted. All analyses identified three clades, two of them generally well-supported. One well-supported clade (BCG) unites Bathycrinus and Guillecrinus with the representative (chimaeric) comatulid in a derived position, suggesting that comatulids originated from a sessile, stalked ancestor. In this connection it is noted that because the comatulid centrodorsal ossicle originates ontogenetically from the column, it is not strictly correct to describe comatulids as unstalked crinoids. A second, uniformly well-supported clade contains members of the Isocrinida, while the third clade contains Gymnocrinus, a well-established member of the Cyrtocrinida, together with the problematic taxon Caledonicrinus, currently classified as a bourgueticrinid. Another cyrtocrinid, Holopus, joins this clade with only weak molecular, but strong morphological support. In one morphological analysis Proisocrinus is weakly attached to the isocrinid clade. Only an unusual, divergent 18S rDNA sequence was obtained from the morphologically strange cyrtocrinid Cyathidium. Although not analysed in detail, features of this sequence suggested that it may be a PCR artefact, so that the apparently basal position of this taxon requires confirmation. If not an artefact, Cyathidium either diverged from the crinoid stem much earlier than has been recognised hitherto (i.e., it may be a Palaeozoic relic), or it has an atypically high rate of molecular evolution.Electronic Supplementary Material Supplementary material is available in the online version of this article at Communicated by J.P. Thorpe, Port Erin     

What attracts juvenile coral reef fish to mangroves: habitat complexity or shade?

The value of mangroves for fish species is usually explained in terms of high food abundance or shelter against predators as a result of high turbidity and structural complexity. In a field experiment, artificial mangrove units (AMUs) were designed as open cages, each of which was provided with a different degree of structural complexity and shade. Fish species that were attracted to the AMUs were identified and counted and the effects of shade and structural complexity, as well as the interaction between the two factors, were tested. Diurnal fish showed a preference for the greatest structured complexity and for a moderate increase in shade. Two nocturnal species common in local mangroves as well as seagrass beds showed statistically significant effects: densities of Haemulon sciurus were positively related to both shade and structural complexity, whereas only shade had a significant positive effect on densities of Ocyurus chrysurus. The experiment indicated that the attractiveness of mangrove vegetation for H. sciurus may be influenced by the structural complexity of the habitat as well as by the degree of shade, and that both factors are equally and separately important. Individuals of O. chrysurus that are attracted to mangroves are more likely to be influenced by the presence of shade than by the degree of structural complexity. The data thus indicated that the positive relationship between fish densities in mangrove habitats and the degree of shade and structural complexity, or both, is species-specific.Communicated by O. Kinne, Oldendorf/Luhe