Abstract Crustacean decapod larvae have developed several adaptations to maximize their survival, including swimming behavior. Swimming improves larvae dispersal and contributes to their response to environmental stresses, including variations in abiotic factors, presence of predators, and search for food. Data on larval behavior can also assist in studies on conservation and in species management in aquaculture. Unfortunately, swimming behavior remains unstudied in many species. The present work aims to analyze the swimming behavior in newly hatched larvae of six common decapod crustaceans in coastal Southeast Brazil (Macrobrachium acanthurus, Macrobrachium olfersii, Emerita brasiliensis, Ucides cordatus, Minuca rapax, and Callinectes danae). The analysis included tests with larval responses to four isolated stimuli: gravity (geotaxis), vertical salinity gradients, low-pressure zones, and presence of the planktivorous fish, Atherinella brasiliensis (only for C. danae and M. rapax). The first two and the last two stimuli were used as indicators of dispersal and defensive behaviors, respectively. All larvae preferred water depth with higher salinity levels. Additionally, negative geotaxis was observed in M. olfersii, M. acanthurus, U. cordatus, and C. danae, being stronger in the last. Both Macrobrachium larvae responded to low-pressure zones, promptly moving away. Callinectes danae and M. rapax larvae avoided contact with the predatory fish by creating avoidance zones around it, even in the absence of light. This is an active defensive behavior that has never been reported for the newly hatched larvae of these two species.

ABSTRACT The vertical distribution of copepod assemblages, ascertained from the surface down to 1,200 m, was investigated during two sampling periods (rainy and dry seasons), at four depths, in the oligotrophic waters of the southwestern Atlantic Ocean. Total density, diversity, and richness differed among sampling depths. Copepod density decreased with depth in the two sampling periods, with a maximum at 1 m and a slight decrease at 800 m. Higher diversities were observed at 250 m and 1,200 m during the rainy season and at 1 m and 1,200 m during the dry season. The maximum number of species was found at 1,200 m during the rainy season and at 1 m during the dry season. Various copepod assemblages were delimited in the water column in the two sampling periods. The deeper copepod assemblages occupied a wider range of depths. Salinity and temperature influenced the structure of copepod assemblages and reflected the hydrographic characteristics of the water masses in the region. Candacia pachydactyla (Dana, 1849), Scolecithrix danae (Lubbock, 1856), and Agetus limbatus (Brady, 1883) were the indicator species found at 1 m. The effects of different environmental factors on the copepod assemblages suggest that these consortia occupy distinct niches in the ocean.

Esse trabalho teve como objetivo identificar e avaliar as variações espaciais e sazonais das apendiculárias no estuário do rio Caravelas e área costeira adjacente (17º35' - 18º22' S e 39º8' - 39º55'W). As coletas foram realizadas em 12 campanhas durante cinco anos (2001 e 2003 - 2006). Foram identificadas dez espécies, sendo que Oikopleura dioica, O. rufescens e O. longicauda foram as mais abundantes. Estas três espécies representaram mais de 95% do total de apendiculárias coletadas. As outras espécies foram menos freqüentes e ocorreram em baixas densidades. A densidade média de apendiculárias encontrada nas estações e costeiras (804 ind.m-3) foi maior que na de estuário (158 ind.m-3). As diferenças encontradas entre as estações de estuário e costeiras não foram significativas (p=0,73). As campanhas realizadas durante o período seco apresentaram densidade média (587 ind.m-3) maior que do período chuvoso (376 ind.m-3). As diferenças entre os períodos chuvoso e seco foram estatisticamente significativas (p>0,01).

This study aimed to identify and assess the seasonal and spatial variations of the appendicularians in the Caravelas River estuary and the adjacent coastal area. Samples were taken during 12 campaigns over five years (2001 and 2003-2006). Ten species were identified; the most abundant were Oikopleura dioica, Oikopleura rufescens, and Oikopleura longicauda. These species represented more than 95% of the total numbers of appendicularians. The remaining species were less frequent and occurred in low densities. The mean density of appendicularians found at the coastal stations (804 ind.m-3.) was higher than in the estuary (66 ind.m-3). However, the differences observed between the estuary and coastal stations were not significant (p=0.54). The samples taken during the dry season showed a higher mean density (587 ind.m-3) than in the rainy season (376 ind.m-3), and the differences between the seasons were statistically significant (p=0.004).

The Caravelas River estuary and adjacent coastal region were studied during the rainy and dry seasons of 2003-2004 to assess the copepod community structure. Abiotic and biotic parameters were measured, and the total density, frequency and percentage of copepod taxa were determined for each sampling period. Copepod densities showed significant differences between sampling periods, with higher densities in the rainy seasons (Mean: 90,941.80 ind.m-3; S.D.: 26,364.79). The sampling stations located to the north and south, in the coastal region adjacent to the Caravelas River estuary presented the lowest copepod density values. The copepod assemblage was composed mainly of estuarine and estuarine/coastal copepods. The seasonal variations in temperature and salinity influenced the abundance of species during the rainy and dry seasons, with the following dominant species alternating: Paracalanus quasimodo Bowman, 1971 in the rainy season of 2003, Parvocalanus crassirostris Dahl, 1894 in the dry season of 2003 and Acartia lilljeborgii Giesbrecht, 1892 in the rainy and dry seasons of 2004. Non-parametric multidimensional scaling indicated differences in copepod assemblages between sampling periods, but not between sampling stations.

The copepod assemblage on the inner continental shelf adjacent to the coastal system of Camamu Bay (state of Bahia, Brazil) is described in relation to hydrographic conditions, during the wet and dry seasons of 2004. The zooplankton samples were obtained in vertical tows using a net with 200 µm mesh size. Temperature and salinity were measured, and the total density, frequency and percentage occurrence of the copepod taxa were determined for each sampling period. The highest densities were observed at the entrance of Camamu Bay (up to 7.473 ind.m-3), and the lowest on the adjacent inner continental shelf south of Camamu Bay (less than 500 ind.m-3). A total of 57 copepod taxa were identified. Paracalanus quasimodo Bowman, 1971, Subeucalanus pileatus (Giesbrecht, 1888), Clausocalanus furcatus (Brady, 1883), Corycaeus giesbrechti F. Dahl, 1894, Temora turbinata (Dana, 1849), Oithona similis Claus, 1866, Temora stylifera (Dana, 1849) and Nannocalanus minor (Claus, 1863) dominated numerically. The densities measured in both sampling seasons were significantly different: the means were 1.849 ± 1.922 ind.m-3 and 3.657 ± 3.170 ind.m-3 for the wet season and dry season, respectively. Depth and temporal variation in temperature and salinity influenced species abundance during the wet and dry seasons, with the dominant species alternating. Species richness and diversity increased on the inner shelf adjacent to the coastal system of Camamu Bay at the 30- and 50-m isobaths, suggesting that most species were oceanic in origin. The diversity was similar to other coastal systems of northeast Brazil.

Este trabalho descreve a estrutura da comunidade de copépodes em relação às condições hidrográficas da baía do Espírito Santo, no período de 1993 a 1997. As amostras do zooplâncton foram obtidas através de arrastos horizontais, quatro vezes ao ano, com uma rede de 200µm. A temperatura, a salinidade e o oxigênio dissolvido foram determinados nas amostras de água. A densidade média dos copépodes foi de 9.085 ind.m-3, com picos superiores a 15.000 ind.m-3, durante o verão e o outono de 1993 a 1995. Utilizou-se a PCA para relacionar as variáveis ambientais à distribuição dos copépodes. A comunidade dos copépodes, principalmente as altas densidades das espécies Acartia lilljeborgi, Oithona hebes, Oithona oculata, Paracalanus quasimodo, Parvocalanus crassirostris e Euterpina acutifrons foram relacionados à diminuição da diversidade. As variações espaço-temporais da temperatura e da salinidade influenciaram a abundância das espécies durante os cinco anos de coleta, com a alternância das espécies dominantes.

The aim of this work was to study the structure of the copepod community in relation to hydrographic conditions in Espírito Santo Bay, from 1993 to 1997. Zooplankton samples were obtained in the horizontal tows four times a year, using a 200 µm net. Temperature, salinity and dissolved oxygen were determined in the water samples. The overall mean density of the copepods was 9,085 ind.m-3 with the peaks exceeding 15,000 ind.m-3 in the summer and autumn during the first three years (1993 - 1995). The PCA analysis was used to relate the environmental conditions with the distribution of the copepods. The increases in the abundant species, namely Acartia lilljeborgi, Oithona hebes, Oithona oculata, Paracalanus quasimodo, Parvocalanus crassirostris and Euterpina acutifrons, were related to the decreases in the diversity. The spatial and temporal variations of the temperature and salinity influenced the abundance of the species during the five years of the sampling and the dominant species alternated in abundance.

Durante uma série de amostragens de zooplâncton, realizadas durante o ano de 1984, na costa sul do estado do Rio Grande do Norte, Brasil, um total de 50 exemplares de copépodes Monstrilloida foram coletados. Os exemplares pertencem a quatro espécies (Monstrilla brasiliensis Suárez-Morales & Dias, Cymbasoma cf. longispinosum, Cymbasoma cf. rigidum and Cymbasoma gracilis Gurney). Os complexos taxonômicos formados pelas espécies C. cf. longispinosum e C. cf. rigidum em águas brasileiras são discutidos. Os comprimentos totais dos exemplares são fornecidos com a finalidade de contribuir com futuros estudos e revisões dos espécimes pertencentes a estes complexos de espécies. A espécie Monstrilla brasiliensis foi coletada pela primeira vez na região costeira do estado do Rio Grande do Norte, expandindo a sua distribuição geográfica na costa nordeste brasileira. Os resultados apresentados aumentam a quatro o número de espécies de Monstrilloida conhecidas para a costa do estado do Rio Grande do Norte.

During a series of zooplankton surveys carried out during 1984, off the south coast of the state of Rio Grande do Norte, Brazil, several species of monstrilloids were present in the samples. A total of 50 individuals of monstrilloid copepods were collected. These belong to four species (Monstrilla brasiliensis Suárez-Morales & Dias, Cymbasoma cf. longispinosum, Cymbasoma cf. rigidum, and Cymbasoma gracilis Gurney). The taxonomic complexes formed by the species C. cf. longispinosum and C. cf. rigidum in Brazilian waters are discussed. The lengths of the specimens are provided in order to contribute to studies and revisions of the specimens belonging to these species-complexes. The species Monstrilla brasiliensis is recorded for the first time in the Rio Grande do Norte coastal region, thus expanding its geographical range in the Brazilian northeastern coast. The results presented herein increase to four the number of species of Monstrilloida known from off Rio Grande do Norte state.

Durante uma série de amostragens de zooplâncton, realizadas de 2001 a 2005, na costa do estado de Bahia, Brasil, 98 exemplares de copépodes Monstrilloida foram coletados. Os exemplares pertencem a cinco espécies (Monstrilla grandis, Cymbasoma cf. longispinosum, Cymbasoma cf. rigidum, Cymbasoma gracilis and Cymbasoma quadridens). As primeiras três espécies foram coletadas pela primeira vez na região costeira do estado da Bahia. A distribuição geográfica de C. quadridens foi expandida para a costa nordeste brasileira. Os resultados apresentados aumentam a nove o número de espécies Monstrilloida conhecidas para a costa da Bahia. A diversidade ambiental do Canal de Caravelas, com áreas altamente produtivas e a proximidade de uma região de recifes de coral, abriga uma abundante e diversa fauna de Monstrilloida, que deve ser examinada mais detalhadamente.

During a series of zooplankton surveys carried out from 2001 through 2005 off the coast of the state of Bahia, Brazil, 98 individuals of monstrilloid copepods were collected. These belong to five species (Monstrilla grandis, Cymbasoma cf. longispinosum, Cymbasoma cf. rigidum, Cymbasoma gracilis, and Cymbasoma quadridens). The first three are recorded for the first time in the Bahia coastal region. The geographical range of C. quadridens is expanded to the Brazilian northeastern coast. The results presented herein increase to nine the number of nominal species of Monstrilloida known from off Bahia; the environmental diversity of Caravelas Channel with highly productive areas and coral reef zones harbor an abundant and diverse monstrilloid fauna that should be surveyed in more detail.

Uma nova ocorrência para o copépode Calanoida Euchaeta paraconcinna Fleminger, 1957 foi registrada na região costeira da baía de Camamu, estado da Bahia, Nordeste do Brasil (14º02'49"S; 38º52'58"W). Três fêmeas foram coletadas em arrastos verticais, com rede de plâncton, de 200 µm de malha. Este registro revela uma nova ocorrência desta espécie no Nordeste do Brasil.

The calanoid copepod Euchaeta paraconcinna Fleminger, 1957 is reported from Camamu Bay, state of Bahia, northeastern Brazil (14º02'49"S; 38º52'58"W). Three females were collected by vertical hauls with a plankton net of 200 µm mesh size. This is a new record for this species in northeastern Brazil.

Larvas de crustáceos decápodes são organismos planctônicos comuns tanto em regiões costeiras rasas como em estuários. Nesse trabalho, foi acompanhada a variação da densidade das larvas de decápodes num ponto estratégico entre a porção interior da baía de Guanabara e a região costeira adjacente. A coleta de grandes quantidades de zoés de braquiúros, principalmente das famílias Portunidae e Grapsidae, na superfície durante as marés de vazante noturnas sugere uma tendência de exportação para a região costeira adjacente. A repetição desse padrão no inverno e no verão demonstrou que as respostas dos organismos às variações de luz e maré não foram alteradas de modo significativo entre as duas estações do ano, exceto para os luciferídeos. O fluxo observado para a única espécie de luciferídeo capturada (Lucifer faxoni) foi significativamente diferente entre os dois períodos do ano analisados. É provável que essas diferenças na distribuição de Lucifer faxoni seja relacionada ao ciclo reprodutivo da espécie. Foi observado um padrão de dispersão similar para as larvas zoé dos portunídeos, grapsídeos e ocypodídeos; transporte para a região costeira adjacente pela superfície durante as marés de vazante noturnas.

In the present study, we observed seasonal variations in the density of decapod larvae as well as changes in density related to diurnal and tidal cycles. Among the decapod larvae collected, portunids and grapsids were the most abundant, especially during nocturnal ebb tides and near the surface. The same results were obtained in late winter (September) and late summer (March). These results demonstrated a flow of decapod larvae from Guanabara Bay to adjacent coastal waters. Luciferid (Lucifer faxoni) was the only group with high densities during flood tides and we suggest this is an evidence of L. faxoni larvae entering Guanabara Bay in late winter. Probably these changes in distribution of Lucifer faxoni among winter and summer were related to reproductive cycle in the bay. For the portunids, grapsids and ocypodids, a similar dispersion strategy was observed towards adjacent coastal waters in the surface during nocturnal ebb tides.