André Morgado Esteves

Marine nematode taxonomy in the age of DNA: the present and future of molecular tools to assess their biodiversity.

Molecular taxonomy is one of the most promising yet challenging fields of biology. Molecular markers such as nuclear and mitochondrial genes are being used in a variety of studies surveying marine nematode taxa. Sequences from more than 600 species have been deposited to date in online databases. These barcode sequences are assigned to 150 nominal species from 104 genera. There are 41 species assigned to Enoplea and 109 species to Chromadorea. Morphology-based surveys are greatly limited by processing speed, while barcoding approaches for nematodes are hampered by difficulties in matching sequence data with morphology-based taxonomy. DNA barcoding is a promising approach because some genes contain variable regions that are useful to discriminate species boundaries, discover cryptic species, quantify biodiversity and analyse phylogeny. We advocate a combination of several approaches in studies of molecular taxonomy, DNA barcoding and conventional taxonomy as a necessary step to enhance the knowledge of biodiversity of marine nematodes.

The relationship between sandy beach nematodes and environmental characteristics in two Brazilian sandy beaches (Guanabara Bay, Rio de Janeiro)

We investigated if the differences in density and nematode communities of intertidal sediments from two Brazilian sheltered sandy beaches were related to environmental characteristics. The upper tide level (UTL) and the low tide level (LTL) of both beaches were surveyed in January (austral summer) and June 2001 (austral winter) during low-spring tides, by collecting samples of nematodes and sediments. Differences in density between beaches, tidal level and seasons, and nematode community structure were investigated. Sediments from both beaches were composed of medium to very coarse sand. The highest nematode densities were found at the UTL, and significant differences between beaches, tidal levels and months were found. A total of 54 genera were found and the genera composition on both sheltered beaches was similar to other exposed worldwide sandy beaches. The density and structure of the nematode community at both beaches clearly varied along the spatial and temporal scales. Gravel percentage was the most important variable explaining the spatial distribution of the nematodes, determining the four sub-communities; this suggests that the sediment characteristics influence the nematode community, rather than physical hydrodynamic forces. Temperature and salinity were suggested to be important variables affecting the temporal variation.

SPATIO-TEMPORAL STUDY AND POPULATION STRUCTURE OF DAPTONEMA OXYCERCA (NEMATODA: XYALIDAE) IN COROA GRANDE, RIO DE JANEIRO, BRAZIL*

Daptonema oxycerca was originally described from the North Sea and, up to now, nothing is known of this species in tropical regions. The spatio-temporal distribution and the population structure of this species was studied during one-year period (from May 1998 through April 1999) in Coroa Grande, Rio de Janeiro, Brazil. For sampling, two fixed, parallel transects were established perpendicularly to the shoreline, and at each transect, four, equally spaced levels were marked to represent the upper and the low intertidal zones. The lowest temperatures occurred in the end of the austral winter and first month of the spring and the highest temperatures occurred in the austral summer. The density of D. oxycerca varied during the year, with a peak in August. This tendency was observed for males, ovigerous females, and non-ovigerous females. The species density was negative correlated with temperature. The sex ratio was not statistically significant. D. oxycerca was most abundant at the upper intertidal level in both transects. This work provides the first record of D. oxycerca in Brazil, and confirms the influence of temperature in regulating its population density.

Four new species of Desmodora (Nematoda) from the deep south-east Atlantic, and a case of intersexuality in Desmodoridae

Four new species of the genus Desmodora are described from the South Atlantic off the south-eastern coast of the State of Rio de Janeiro, Brazil. Desmodora porosum sp. nov. is characterized by sexual dimorphism in the shape of the amphids, which are closed loop-shaped in males, and multispiral amphids in females. A case of intersexuality was found in the species, with a functional female gonad. Desmodora profundum sp. nov. is characterized by filiform spicules with a capitulum, buccal cavity with one dorsal and one small ventral tooth, tail cylindrical with a terminal spinneret, and wider rings in the neck region than on the rest of the body. Desmodora veronicae sp. nov. possesses cryptospiral amphids, a buccal cavity with one dorsal tooth and two smaller ventral teeth, 14 tubular pre-cloacal supplements, two ventral cuticular protruberances on the tail, and curved spicules with a capitulum and velum. Desmodora curvatum sp. nov. has the cuticle finely striated, without somatic setae, multispiral amphids, and a gubernaculum without apophysis, curved dorsally with the tip directed toward the end of the body.

Hooked from the deep: a rare new species of Taeniogyrus (Holothuroidea, Chiridotidae) from the continental slope of Brazil, southwestern Atlantic.

Most species of Taeniogyrus Semper, 1867 are known from shallow water in the Indo-Pacific, with other records in Antarctica, Mediterranean Sea, and the Atlantic. A new species of Taeniogyrus is described and illustrated here from the continental slope of Campos Basin, southeast of Brazil. In this species, sigmoid hooks (336-405 µm) are much larger than in any other in the genus, bearing a long and conspicuous hook region. Wheels with six spokes (86-169 µm), inner margin with 60-125 continuous teeth, are confined to round papillae along each interradius. Polian vesicles are ventral, numerous (15-21), of different sizes, and tubular shaped with a terminal round region. This new species represents the deepest record of the genus Taeniogyrus. It increases to three the number of chiridotids in Brazilian waters, and the number of Taeniogyrus species in the Atlantic. Additionally, Taeniogyrus furcipraeditus (Salvini-Plawen, 1972) from the Mediterranean Sea and Taeniogyrus havelockensis (Rao, 1975) from the Andaman Sea are proposed as new combinations.

Five new species of Oncholaimellus (Oncholaimidae: Nematoda) from north-east Brazil, with an emended diagnosis and an updated key to the genus

Five new species of Oncholaimellus are described. They were found in macrofauna samples from the continental shelf in the Potiguar Basin, north-east Brazil. Cuticular pores with a sclerotized outline associated with a gland were observed in some species. Oncholaimellus multiporus sp. nov. is differentiated from other species by the presence of cuticular pores of different sizes; the smaller pores are abundant and give an appearance of ornamentation. Oncholaimellus intersexus sp. nov. and O. distortus sp. nov. are similar, but differ in the size of the external labial and cephalic setae compared to the corresponding diameter, the presence of the cuticular pores and the tail shape. Oncholaimellus paulus sp. nov. and O. sineporus sp. nov. are similar, although features such as the external labial and cephalic setae size compared to the corresponding diameter and the cuticular pores differentiate between them.

Is nematode colonisation in the presence of Scolelepis in tropical sandy-beach sediment similar to the colonisation process in temperate sandy beaches?

The role of a dominant macrobenthic polychaete, Scolelepis squamata, in the colonisation of defaunated tropical sediments by sandy-beach nematodes was investigated and compared with a previous colonisation experiment carried out on a temperate sandy beach. Experimental cylinders, equipped with lateral windows allowing infaunal colonisation, were filled with defaunated sediment containing two treatments, with and without S. squamata. These cylinders were inserted into microcosms containing sediment with indigenous meiofauna collected from the field. The treatments were incubated in the laboratory at ambient temperature and salinity for 7, 14 and 21 days. The nematode assemblages in both treatments did not differ in composition between treatments and from the natural assemblages, suggesting that all the species were equally able to colonise the experimental cores. The presence of the polychaete did not affect the development of the nematode community composition, in contrast to the results from a previous temperate-beach experiment. However, our results did not indicate whether the difference in results was caused by the different behaviour of the polychaete specimens, or by the different composition and response of the present nematode community.

Sandy beaches: state of the art of nematode ecology

In this review, we summarize existing knowledge of the ecology of sandy-beach nematodes, in relation to spatial distribution, food webs, pollution and climate change. We attempt to discuss spatial scale patterns (macro-, meso- and microscale) according to their degree of importance in structuring sandy-beach nematode assemblages. This review will provide a substantial background on current knowledge of sandy-beach nematodes, and can be used as a starting point to delineate further investigations in this field. Over decades, sandy beaches have been the scene of studies focusing on community and population ecology, both related to morphodynamic models. The combination of physical factors (e.g. grain size, tidal exposure) and biological interactions (e.g. trophic relationships) is responsible for the spatial distribution of nematodes. In other words, the physical factors are more important in structuring nematodes communities over large scale of distribution while biological interactions are largely important in finer-scale distributions. It has been accepted that biological interactions are assumed to be of minor importance because physical factors overshadow the biological interactions in sandy beach sediments; however, the most recent results from in-situ and ex-situ experimental investigations on behavior and biological factors on a microscale have shown promise for understanding the mechanisms underlying larger-scale patterns and processes. Besides nematodes are very promising organisms used to understand the effects of pollution and climate changes although these subjects are less studied in sandy beaches than distribution patterns.

Known and new species of Sabatieria Rouville, 1903 (Araeolaimida: Comesomatidae) from the southwest Atlantic (Campos Basin, Brazil)

Abstract In the Campos Basin, 12 species of Sabatieria were collected, 2 of which were new to science. Sabatieria labium sp. nov. is characterized by well-defined lips and a spiral amphideal fovea with 4.25–4.5 narrow turns, combined with cephalic setae 3 µm long and 7–8 small, pore-shaped supplements, gradually spaced further apart anteriorly. Sabatieria verteris sp. nov. possesses 8–10 minute, pore-shaped precloacal supplements, gradually spaced further apart anteriorly, and short, slightly sclerotized spicules. Additionally, redescriptions of Sabatieria flecha, S. fidelis, S. mortenseni, S. ornata and S. paracupida are presented. The collection of additional specimens of these species allowed a re-evaluation of morphological and/or morphometric variations.

New records and species of Enchelidiidae (Nematoda): Symplocostoma brasiliensis sp. nov. and a first description of the female of Calyptronema pigmentatum Gerlach, 1957

Abstract This contribution presents a new species of Symplocostoma, the first member of this genus identified for the coast of Brazil, and a dichotomous key for species of the genus. There is also a redescription of the male and the first description of the female of Calyptronema pigmentatum. Samples were collected on the continental shelf of the Potiguar Basin, northeastern Brazil. Symplocostoma brasiliensis sp. nov. has several distinguishing characteristics: the position of the secretory–excretory pore, tail length, the presence of denticles in the buccal cavity (female) and the number of precloacal supplements (male). The male of C. pigmentatum showed most morphological and morphometric characters of the original description, except for the size of the amphidial fovea and the number of precloacal supplements. The male differs from C. maxweberi in the spicular apparatus, gubernaculum shape, number of precloacal papillae and tail length. The female of the species has a buccal cavity similar to that of C. mawsoni, but differs in the position of the secretory–excretory pore and the shape of the amphidial fovea and tail.