Spatio-temporal study and population structure of Daptonema Oxycerca (Nematoda: Xyalidae) in Coroa Grande, Rio de Janeiro, Brazil

Abstract

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. RESUMODaptonema oxycerca foi descrita originalmente para o Mar do Norte, mas até o momento nada se conhece sobre essa espécie em regiões tropicais. A distribuição espaço-temporal e a estrutura populacional de D. oxycerca foram estudadas durante o período de um ano (de Maio 1998 a Abril 1999) em Coroa Grande, Rio de Janeiro, Brasil. Para a amostragem, dois transectos fixos e perpendiculares à linha d'água foram estabelecidos, e, em cada transecto, quatro níveis foram marcados para representar as zonas superior e inferior do médiolitoral. As menores temperaturas foram observadas no final do inverno e início da primavera e as maiores temperaturas no verão. A densidade de D. oxycerca variou durante o ano, com um pico em agosto. Essa tendência foi observada para os machos, as fêmeas grávidas e as fêmeas não-grávidas. A densidade da espécie correlacionou-se negativamente com a temperatura. A variação da razão sexual não foi significativa. D. oxycerca foi mais abundante no nível superior do médiolitoral em ambos os transectos. Esse trabalho representa o primeiro registro de D. oxycerca no Brasil, assim como, confirma a influência da temperatura na regulação de sua densidade populacional.

State of the art of the meiofauna of Brazilian Sandy Beaches

“…Of these ecological studies, 7 are exclusively related to the effects of environmental variables on the population of a single nematode species (ESTEVES et al, 2003(ESTEVES et al, , 2004MARIA et al, 2008a;VENEKEY et al, 2011) and tardigrades (CASTRO et al, 1999;DA ROCHA et al, 2004;VERÇOSA et al, 2009) and have not been listed in Table 1. The other 37 are related to meiofauna community studies.…”

“…In Brazil, the most closely related studies that could be used as elements for the understanding of climate change are those that analyze the natural life cycle of the meiofauna over an one-year period (e. g., ESTEVES et al, 2003;2004;MARIA et al, 2008a;VENEKEY et al, 2011). However, these studies address the question to a single nematode population indicating that certain species increase their density during rainy or dry seasons.…”

Influence of the tidal and rainfall cycles on the population structure and density of Mesacanthion hirsutum gerlach (nematoda, thoracostomopsidae) on a tropical sandy beach (Tamandaré Bay, Pernambuco, Brazil)

“…The data concerning Nematoda in the same study area confirmed this pattern (SOUZA-SANTOS et al, 2003). Although the Nematoda group seems to be associated with the rainfall cycle, ESTEVES et al (2003), ESTEVES et al (2004) andMARIA et al (2008) studying Oncholaimus cobbi, Comesoma arenae and Daptonema oxycerca, respectively, on a tropical tidal flat (Coroa Grande, Rio de Janeiro -Brazil), found that each species behaved differently. Oncholaimus cobbi was more abundant during the warmer and rainy season while C. arenae and D. oxycerca preferred the colder and dry months.…”

“…Ecological studies on nematodes at low taxonomical level have just been begun with works such as those of NETTO and GALLUCCI (2003), FONSECA-GENEVOIS et al (2004), DA ROCHA et al (2006) andFONSECA-GENEVOIS et al (2006). Also recently, were published the first studies concerning the population structure of Oncholaimus cobbi Kreis, Comesoma arenae Gerlach and Daptonema oxycerca DE MAN by ESTEVES et al (2003), ESTEVES et al (2004) andMARIA et al (2008), respectively.…”