meiofauna

The relationship that benthic organisms have on fish that live on the reef is well known. Some benthic organisms can be regarded as bio-indicators, acting as indicators of nutrient levels in an ecosystem. Benthic organisms are also an important food source for fish and other invertebrates. In this study, organisms from sediment cores at five different depths were analyzed. Meiofauna and macrofauna cores were collected at each depth and the organisms were identified to family level. This study provides information on where these organisms prefer to live, and if there are any depths that are more favorable or diverse. The abundance of species increased in macrofauna samples from depth 10 m to 20 m. This was after a decrease in density from 5 m, which had the highest density, to 10 m depths, which had the lowest density. This trend was also present in macrofauna species richness. The meiofauna samples also had the highest species richness and density of individuals at 5 m depth for species, but both variables decreased with increasing depths. The data shows an increase at the 5 m depth. With further testing we can better understand the relationship depth has on the diversity of the benthic zone in the southern Caribbean

This student research was retrieved from Physis: Journal of Marine Science XI (Fall 2012)19: 9-14 from CIEE Bonaire.

Abstract

Macrodasyidan gastrotrichs are hermaphrodites with complex reproductive organs that function in sperm transfer and receipt, but homology among the organs of members of different clades remains undetermined, as does a broader understanding of evolutionary trends in the reproductive biology of macrodasyidans. In this study, we investigate the evolution of reproduction in Urodasys, a clade of 15 macrodasyidan species that shows variability in reproductive mode (hermaphroditic and parthenogenetic) and sexual anatomy. We use partial 18S rDNA sequence data from 30 specimens representing five described species, sequence data from one undescribed species in GenBank, and sequence data from a potentially new species found at Capron Shoal, Florida, to gain insight into the phylogeny of the clade and clarify evolutionary trends in reproductive modality. Based on a total of 33 specimens of seven potential species, we found that members ofUrodasys can be separated into three clades reflective of different reproductive modalities: Clade I, species with paired male and female gonads but without accessory sexual organs; Clade II, species with a single left testis, paired ova, and accessory organs including a sclerotic stylet; and Clade III, parthenogenetic species without testes or accessory organs. In addition, we find that the potentially new species from Florida can form spermatophores, a condition shared with another species in Clade I. Herein, we describe this novel spermatophore-bearing species and discuss the significance of spermatophore formation in the genus.