Recruitment of Demosponges (Porifera,Demospongiae) in Rocky and Coral Reef Habitats of Santa Marta,Colombian Caribbean*

Abstract. Recruitment of demosponges (Porifera, Demospongiae) was monitored bimonthly for one year (March 1987 – March 1988) on acrylic plates, and compared to cover of adults, in six rocky and coral reef habitats at Santa Marta, Colombian Caribbean, an area subjected to seasonal, upwelling-outwelling regimes. According to suggestive but not significant trends, recruitment rates are more positively influenced by the total sponge cover near groups of plates than by cover at a larger (habitat) scale; recruit mortality is lower where recruitment is higher. These findings are in agreement with a model of higher settlement (probably due to short-distance dispersal) and lower postsettlement mortality within a few meters of adult sponges. Recruitment varied seasonally, being relatively high from May to November-December during the rainy, outwelling season, when seawater temperature was warmer, water turbidity higher, and benthic algal density lower; it was very low from January to April during the dry, upwelling season.     

The Contribution of Secondary Space to Benthic Taxon Richness of a Coral Reef: Colonisation of Dendrostrea frons (Mollusca)

Abstract. The reef‐dwelling oyster Dendrostrea frons occupied only a small proportion of space in coral reefs of the Quirimba Archipelago, Mozambique, but supported a disproportionately high variety of taxa. Assemblages on primary (substratum), secondary (dead coral heads) and ephemeral secondary space (D. frons shells) of similar area were compared across 5 depths (5, 10, 15, 20 and 25 m) and at four taxonomic levels (species, genus, class and phylum). Differences between the taxonomic richness of each type of space differed with both taxonomic level considered and depth. Of the three categories of space considered, ephemeral secondary space had the most taxa at all levels with the maximum at 10 – 15 m. Despite being small in space and time, animal externa, such as shells of D. frons, may provide important niches for particular organisms at many taxonomic levels.     

Phylogeographic patterns in Maguimithrax spinosissimus (Decapoda: Mithracidae) from Colombian Caribbean

The Caribbean king crab Maguimithrax spinosissimus is an important artisanal fisheries resource with a distribution range that includes the Florida Keys and Caribbean Sea islands. We carried out a phylogeographic analysis of M. spinosissimus in one oceanic (Old Providence) and two continental islands (Rosario and Tintipán). We analysed 89 and 49 Control Region (CR) and Cytochrome Oxidase I (COI) sequences, respectively. We found genetic differentiation between Old Providence and Rosario?+?Tintipán units (F_ST values of 0.84 for CR and 0.91 for COI gene), and gene flow between Rosario and Tintipán (F_ST values ?0.0085 for CR, P?>?.88; ?0.01 for COI gene, P?>?.99). Our analysis showed two genetic stocks and possibly an isolated biogeographic unit of M. spinosissimus. We suggest managing the species as different populations, and conducting more ecological and biological studies for the determination of possible cryptic species.     

Tethya (Porifera,Demosponglae) Species Coexisting in a Maldivian Coral Reef Lagoon: Taxonomical,Genetic and Ecological Data

Abstract. Tethya microstella, T. orphei, T. robusta, and T. seychellensis live in sympatry in a Maldivian coral reef lagoon (Gangehi Island, Ari Atoll). A morphological, morphometric, and electrophoretical study of these species show that their Maldivian populations are well separated morphologically and genetically. The genetic distances and the other data are more consistent with an immigration than with a local speciation hypothesis. Their coexistence may be explained by a differentiation in ecological requirements. The four species inhabit the shallow water biotope of the lagoon among the rubble of dead corals. Our data show that T. orphei and T. seychellensis occupy the upper rubble layer, T. microstella and T. robusta the lower one. This distinction agrees with the different morpho-functional features of the two pairs of species.     

The Bryozoan Rhynchozoon larreyi (Audouin, 1826)–A Successful Competitor in Coral Reef Communities of the Red Sea

Abstract. Rhynchozoon larreyi (A udouin , 1826) is a successful competitor for space in sessile reef communities at Port Sudan and Eilat (Red Sea). At these localities it has always been found in association with Zanclea sp. The relationship between the two species is regarded as mutualistic. The hydroid benefits through association with a successful spatial competitor; the bryozoan gains advantage through protection of its surface from predation and fouling. Morphological modification of the bryozoan colony in response to this association leads to a highly organized reticulate surface pattern, which provides both symbionts with access to feeding currents.     

Distribution of the genus Hypoplectrus (Teleostei: Serranidae) in the Greater Caribbean Region: support for a color‐based speciation

The reef‐associated fish genus Hypoplectrus (Serranidae), endemic to the western Atlantic Ocean, represents an ideal model to study speciation within a potentially highly dispersive (marine) ecosystem, because it consists of a complex of at least 10 morphs differentiated primarily by coloration. Although several recent studies on genetics, diet, and fertilization reveal little to no difference between the Hypoplectrus color morphs, there is still not a full understanding of what keeps these morphs distinct or drives their variation. Ecological information is needed alongside the genetic information to better understand this variation. Based on presence/absence records from scientific literature and direct observations in coral reefs, this work examined the distribution of the genus Hypoplectrus in the Greater Caribbean region. Some color morphs occurred simultaneously at given locations, but others showed geographic restrictions. Using cluster and nMDS analyses, we found three major groupings according to distribution: (i) widespread (Hypoplectrus puella, Hypoplectrus unicolor, and Hypoplectrus nigricans), (ii) less widespread (Hypoplectrus indigo, Hypoplectrus gummigutta, Hypoplectrus chlorurus, Hypoplectrus aberrans, and Hypoplectrus guttavarius), and (iii) geographically confined or segregated (Hypoplectrus gemma, Hypoplectrus providencianus). Geographic sections selected for the Greater Caribbean (eastern, western and northern) were dominated by at least three widely distributed Hypoplectrus morphs. New geographic records of some color morphs were documented and compared to previous established distribution ranges in the Greater Caribbean.     

The onset of fish colonization in a coastal defence structure (Chioggia,Northern Adriatic Sea)

Coastal defence structures constitute the most extensive hard substrates of the Northwestern Adriatic Sea and are known to sustain rich benthic and nektonic communities. To appreciate the pattern of colonization, we studied the fish assemblage of a recently deployed breakwater. We compared observations from two years, the different sides (landward and seaward) of the barrier, and the two fringes, characterized by timing of work completion. The results indicate that colonization, still in process, follows different patterns among species. Benthic and necto-benthic species presented a striking increase in abundance and richness in the second year of colonization, while more mobile species did not evince any variation between years. Differences in mobility among species suggest that the latter group may have reached the breakwater from nearby artificial substrates, whereas the former colonized the new structure as recruits. In addition, fish assemblages differed between the two sides, likely due to variation in the environmental characteristics, and according to depth, reflecting species preferences.     

Benthic Communities of the lnfralittoral in the N. Sporades (Aegean Sea): a Variety of Biotopes Encountered and Analysed

Abstract. The infralittoral benthos was studied on three islands of the Northern Sporades in the Aegean Sea. Thirteen stations were sampled on both hard and soft substrata and 408 taxa were identified, some of zoogeographical interest. Multivariate statistical methods such as classification, ordination and Similarilies Terms Analysis were combined with existing ecological information to delineate the various communities present and to point to the indicator species characterising them. The communities were then defined using the indicator species and their affinities to typical biocoenoses. The main factor responsible for the observed distribution proved to be the type of substratum (algal cover or sediment type), which reflects the light and hydrodynamic conditions. The observed bathynietric zonation was similar lo that of the Balearic Islands in the western Mediterranean.