Comparison between the shrimp species richness (Caridea and Dendrobranchiata, Decapoda, Crustacea) of the south and north mid Atlantic ridge

Abstracts

The Mid Atlantic Ridge (MAR) is a seamount chain extending for 60.000 km, divided into south and north regions by the Equatorial Fracture which cuts across it. This latter has a maximum depth of 7,760 m and an average width of 19 km. In this study we include data from the two cruises of the international project MAR-ECO, undertaken, respectively, one on the north and the other on the south MAR. Our main objective is to compare the species richness and species composition of pelagic and benthic decapod shrimps of these two areas to observe the patterns of their latitudinal distribution along the MAR. Using rarefaction methods, we obtained interesting results: the pelagic samples curve of the northern MAR is almost an asymptote, so we concluded that we are close to the true number of pelagic shrimp species for this region. The pelagic samples curve of the southern MAR had the greatest slope, so our conclusion is that we are still far from the true number of species for this region. A comparison of species richness at 12 samples (the smallest number of samples shared by both the surveys) revealed that the pelagic species richness was greater than the demersal, and that the northern MAR contained a larger number of species than the southern.

Mid Atlantic Ridge; Decapoda; Caridea; Dendrobranchiata; Species richness; Specific composition; Distributional patterns

A Cordilheira Meso Atlântica (CMA) é uma cadeia de montes submersos com 60.000 km, dividida em região norte e sul, separadas pela Fratura Equatorial, que corta transversalmente a CMA. A Fratura Equatorial possui profundidade máxima de 7.760 m e largura média de 19 km. Incluímos aqui dados de dois cruzeiros do projeto internacional MAR-ECO, um no norte e um no sul da CMA. Nosso principal objetivo é comparar a riqueza de espécies e a composição específica de camarões decápodes, pelágicos e bentônicos, dessas duas áreas para observar padrões de distribuição latitudinal ao longo da CMA. Usando métodos de rarefação, obtivemos resultados interessantes: a curva de amostras pelágicas da CMA norte encontra-se perto de uma assíntota, o que nos levou a concluir estarmos próximos ao número verdadeiro de espécies de camarões pelágicos nesta região. Por sua vez, a curva de amostras pelágicas da CMA sul possui uma inclinação muito forte, o que nos permitiu concluir que nessa região ainda estamos longe do número verdadeiro de espécies. Uma comparação da riqueza de espécies em 12 amostras (menor número de amostras compartilhado pelos dois cruzeiros) revelou que a riqueza de espécies pelágicas é maior do que a demersal, e que a CMA norte contém uma riqueza maior que a região ao sul.

Cordilheira Meso-Atlântica; Decapoda; Caridea; Dendrobranchiata; Riqueza de espécies; Composição específica; Padrões de distribuição

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Publication Dates

• Publication in this collection
  03 June 2014
• Date of issue
  Mar 2014

History

• Received
  27 Mar 2013
• Accepted
  21 Jan 2014
• Reviewed
  15 Dec 2013