Genetic, abiotic and social influences on sex differentiation in cichlid fishes and the evolution of sequential hermaphroditism

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73799/1/j.1467-2979.2005.00184.x.pd

A functional analysis of food procurement in two surgeonfish species, Acanthurus nigrofuscus and Ctenochaetus striatus (Acanthuridae)

The mechanisms of food procurement in the surgeonfishesCtenochaetus striatus andAcanthurus nigrofuscus from the Great Barrier Reef were determined by functional analyses of the jaws and associated structural elements (based on myological and osteological examinations and X-ray photographs) and by video analyses of actions of the mouth and body during feeding.Acanthurus nigrofuscus has relatively robust jaw bones. The movement of the elements during mouth opening is limited with a mean maximum gape angle of 112.8°. Each bite is relatively fast and is characterized by a quick nip at algal filaments, usually followed by a sidewads flick of the head. The jaws bear several broad multidenticulate teeth. It appears that these teeth engage turf algal strands which are either sheared during mouth closure or torn off as the head flicks sideways. InC. striatus, the jaw bones are considerably lighter than those ofA. nigrofuscus. There is much greater movement of the elements during mouth opening, resulting in a mean maximum gape angle of 177.6°. Each bite is slower than inA. nigrofuscus and is characterized by a wide gape as the mouth is applied to the substratum followed by a quick, upward flick of the lower jaw, with no sideways flick of the head. The jaws bear numerous elongate flexible teeth, with expanded incurved denticulate tips; those on the dentary often possessing a pointed blade-like process. It appears that these teeth brush particulate and epiphytic material from the surface of the turf algal strands and other substrata. These observations demonstrate howA. nigrofuscus andC. striatus are able to remove microalgae and detritus, respectively, from the same substratum. The results also demonstrate how relatively small differences in morphology can have a profound influence on the feeding abilities and trophic ecology of fishes

Diversidade e capacidade simbiótica de rizóbios isolados de nódulos de Mucuna-Cinza e Mucuna-Anã

As espécies de mucuna são muito utilizadas como adubos verdes, e poucas informações estão disponíveis a respeito dos rizóbios nativos capazes de nodulá-las. O objetivo deste trabalho foi avaliar a diversidade e a capacidade simbiótica de isolados bacterianos de nódulos de mucuna-cinza (Mucuna pruriens (L.) DC.) e mucuna-anã (Mucuna deeringiana (Bort.) Merr.). As bactérias foram isoladas de nódulos de mucunas cinza e anã cultivadas em vasos com solos de um sistema de produção agroecológica. Foram isoladas 160 bactérias, sendo 80 de mucuna-anã e 80 de mucuna-cinza, que foram autenticadas e selecionadas para avaliação da capacidade simbiótica. A diversidade dos isolados foi avaliada por meio das características culturais em meio de cultura YMA e da técnica de análise de restrição do produto de PCR do gene 16S rDNA. A inoculação de cinco isolados em mucuna-cinza e dois em mucuna-anã apresentou elevada biomassa da parte aérea. A maioria dos isolados apresentou crescimento rápido e acidificou o meio de cultura. A análise de restrição demonstrou que as bactérias isoladas apresentam baixa similaridade com estirpes de referência, sugerindo a existência de isolados pertencentes a novos grupos, capazes de nodular as mucunas anã e cinza