Biodiversity of littoral nematodes from two sites in the Gulf of California

Hydrobiologia (Impact Factor: 2.28). 07/2007; 586(1):179-189. DOI: 10.1007/s10750-006-0624-z


The Gulf of California, Mexico, consists of unique environmental conditions resulting in a rich array of biological diversity.
Nematodes are present in most marine sediments and are probably the most abundant metazoans. This research analyses and compares
nematode biodiversity in two shallow, littoral locations of the Gulf and compares the results with other Pacific and Atlantic
faunae. Samples collected in Punta Estrella and Santa Clara were processed for nematode extraction by standard methods. A
total of eighty genera were identified, sixty-seven occurring in coarser sediments at Punta Estrella and fifty-five in more
silty sediments at Santa Clara. Nematode abundance was higher at the latter location, on average. The region was not especially
high or low in diversity compared to other littoral sites, and was most similar to locations in Europe with a corresponding
ecology but at temperate latitudes.

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    • "The marine nematode communities of the Gulf of California are poorly known and data are available from only two localities in the UGC (Mundo-Ocampo et al. 2007; Holovachov et al. 2008), and there is no information available from the Pacific coast of Baja California. Thus, this study focused on enoplids reveals novel insights about the distribution of marine nematodes in other areas of the Gulf of California as well as the first data from the Pacific coast of Baja California, Mexico. "
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    ABSTRACT: We used morphological and molecular approaches to evaluate the diversity of free-living marine nematodes (order Enoplida) at four coastal sites in the Gulf of California and three on the Pacific coast of Baja California, Mexico. We identified 22 morphological species belonging to six families, of which Thoracostomopsidae and Oncholaimidae were the most diverse. The genus Mesacanthion (Thoracostomopsidae) was the most widespread and diverse. Five allopatric species, genetically and morphologically differentiated, were found in two localities in the Gulf of California (M. sp1 and M. sp2) and three in the Pacific coast (M. sp3, M. sp4 and M. sp5). Overall, we produced 19 and 20 sequences for the 18S and 28S genes, respectively. Neither gene displayed intraspecific polymorphisms, which allowed us to establish that some morphological variation was likely either ontogenetic or due to phenotypic plasticity. Although 18S and 28S phylogenies were topologically congruent (incongruence length difference test, P>0.05), divergences between species were much higher in the 28S gene. Moreover, this gene possessed a stronger phylogenetic signal to resolve relationships involving Rhabdodemania and Bathylaimus. On the other hand, the close relationship of Pareurystomina (Enchilidiidae) with oncholaimids warrants further study. The 28S sequences (D2D3 domain) may be better suited for DNA barcoding of marine nematodes than those from the 18S rDNA, particularly for differentiating closely related or cryptic species. Finally, our results underline the relevance of adopting an integrative approach encompassing morphological and molecular analyses to improve the assessment of marine nematode diversity and advance their taxonomy.
    Marine Biology 08/2010; 157(8):1665-1678. DOI:10.1007/s00227-010-1439-z · 2.39 Impact Factor
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    • "The mid-intertidal maxima in species richness have been attributed to optimal combinations of physical and chemical conditions (Armonies and Reise 2000; Gheskiere et al. 2004). Environmental gradients as well as individual environmental factors have received foremost attention in our understanding of intertidal community patterns, whereas the role of habitat complexity has been widely neglected or even avoided (Gheskiere et al. 2004; Mundo-Ocampo et al. 2007). However, complexity is the hallmark of some beach types, such as macrotidal (i.e. "
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    ABSTRACT: The role of habitat complexity has been widely neglected in the study of meiofaunal community patterns. We studied the intertidal nematode community of a structurally complex macrotidal beach exhibiting contrasting microhabitats (sandbars and runnels) to understand the influence of environmental gradients and habitat heterogeneity in the community structure. We tested whether topographical complexity affected (1) the zonation pattern in terms of abundance and diversity, and (2) local diversity by promoting compartmentalization into distinct faunal groups. Our analyses revealed three major faunal assemblages along the exposure gradient associated to differences in mean grain size and chlorophyll a. Diversity patterns involved a mid-intertidal peak, consistent with the intermediate disturbance hypothesis, and another peak at the limit with the subtidal region, consistent with the transition zone. These results highlight the predominance of environmental gradients in establishing intertidal zonation. However, microhabitats differed in environmental conditions and possessed significantly distinct nematofaunal communities. Runnels featured higher levels of taxonomic and functional diversity, many unique genera, and the community differed from the assemblage at the limit to the subtidal, stressing their role as distinct microhabitats. The nematofauna of the structurally complex beach was more diverse than the one from a homogeneous beach nearby, supporting the hypothesis that structural heterogeneity promotes diversity by compartmentalization and highlighting the importance of microhabitats in the assessment of biodiversity. Contrary to previous predictions, our results indicate potentially high regional marine nematode diversity in the Upper Gulf of California. Electronic supplementary material The online version of this article (doi:10.1007/s00227-010-1447-z) contains supplementary material, which is available to authorized users.
    Marine Biology 08/2010; 157(8):1741-1753. DOI:10.1007/s00227-010-1447-z · 2.39 Impact Factor
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    • "The intertidal nematode community of Santa Clara features at least 55 genera. Predators include Enoploides (Thoracostomopsidae), Richtersia, Gammanema (both Selachinematidae) and facultative predators such as Viscosia and Oncholaimus (both Oncholaimidae) (Mundo-Ocampo et al., 2007 "
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    ABSTRACT: This study documents direct evidence of nematode predation in the free living marine nematode Synonchiella spiculora recorded in the intertidal of Santa Clara beach in the Upper Gulf of California, Mexico. The heavily armored buccal cavity that allows S. spiculora to break larger particles and ingest other organisms is characteristic of nematodes categorized as predators and omnivores (Wieser, 1953). The inferred feeding behaviour of S. spiculora and other Selachinematidae suggests that engulfing whole and relatively large prey items may be common in this group. Synonchiella spiculora could be classified in the guild of ‘predators’ sensu Jensen (1987) and Moens & Vincx (1997). Nevertheless, more direct observations are required to ‘ground truth’ inferences based on their morphological variation and to better understand their feeding ecology.
    Marine Biodiversity Records 05/2009; 2:e111. DOI:10.1017/S1755267209001092
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