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

Hydrobiologia (Impact Factor: 1.99). 01/2007; 586(1):179-189. DOI: 10.1007/s10750-006-0624-z

ABSTRACT 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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    ABSTRACT: In the absence of chemical or physical gradients, random displacement of organisms can result in unpredictable distribution patterns. In spite of a limited locomotive capability, marine nematodes may choose where to settle after re-suspension and may maintain their position in the sediment under calm conditions, leading to small-scale (,1 m) spatial variability. However, in more energetic environments, nematodes become re-suspended with sediments and re-distributed at distances dependent on prevalent hydrodynamic regimes, from metre- to decametre-scale or more. In this study, we tested the hypothesis that micro-habitats (i.e. runnels and sandbars) in a macrotidal sandy beach influence the distribution patterns of freeliving marine nematodes by exhibiting contrasting hydrodynamic regimes. Specifically, we predicted patchier distributions in the calmer environment (runnel). We sampled nematodes in each habitat from ,1 m to decametre scales. Our results show more heterogeneous spatial distributions in the runnel, presumably owing to a predominance of active displacement under calmer conditions and sediment cohesion by algal films. Biological similarity among runnel replicates was low, whereas replicates from the sandbar exhibited higher similarity, presumably because of homogenization of the sediment and inhabiting fauna by tidal currents. A significant negative correlation between biological similarity and sampling distance was found in the runnel, but not in the sandbar. The most similar samples were the closest in the runnel and the most distant in the sandbar. More patchily distributed taxa were found in the runnel and a larger fraction of homogeneously or randomly distributed taxa in the sandbar. We conclude that different hydrodynamic regimes in contrasting intertidal microhabitats significantly influenced the nematofaunal distribution, resulting in different spatial patterns next to one another in the same beach. This has significant implications for sampling and monitoring designs and begs the need for detailed studies about the physical and biological processes governing meiobenthic communities.
    Journal of the Marine Biological Association of the UK 01/2011; 91:615–622. · 1.02 Impact Factor
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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 01/2009; 2:e111.
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    ABSTRACT: Xyala finneyae sp. n. from the intertidal zone in the northern Gulf of California, Mexico, is described using light and scanning electron microscopy. The new species is characterised by the first ring of cuticular crests being at least twice as long as the crests on the remaining annules, vulva at 70-76% of body length from anterior end, sexual dimorphism in amphid fovea size with females having a smaller amphidial opening. Xyala finneyae sp. n. is most similar to the type species, X. striata, and to X. oxybiotica. It differs from the former in having the first ring of crests markedly longer than all subsequent ones, in having shorter outer labial and cephalic setae on the lip region (8-9 and 15-18 vs 12 and 22 μm, respectively), in a more anterior position of vulva (V = 70-76 vs 79-81) and in shorter spicules (29-31 vs 44-47 μm). From X. oxybiotica, it differs in the more spherical lip region with thinner cuticle on the lips (vs lips more protruding anteriad and with thicker cuticle in optical section), shorter outer labial and cephalic setae on the lip region (8-9 and 15-18 vs 13 and 23 μm, respectively), a more anterior vulva (V = 70-76 vs 81-89) and shorter spicules (29-31 vs 35 μm).
    Nematology 11/2010; 12(5):673-680. · 1.25 Impact Factor

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