Mangrove-associated fish assemblages off the southern Panama Bight region (tropical eastern Pacific)

The Panama Bight ecoregion (PBE) in the eastern Pacific contains probably the best developed mangrove forests in the American continent. Fishes inhabiting the mangrove-estuary mosaic play fundamental ecological roles and sustain the artisanal fishery operating there. Here, using data collected along ~300 km between 2012 and 2017, we examine the spatial dynamics of mangrove fish assemblages that undertake intertidal migrations in the southern part of the PBE (southern Colombian Pacific coast), where the largest and least disturbed mangroves of Colombia are located. Sixty-one fish species used intertidal mangrove habitats in these areas, constituting ~30% of all fishes inhabiting the whole mosaic of mangrove habitats in this ecoregion. Species within Clupeidae, Ariidae, Centropomidae and Tetraodontidae, all common in mangroves of the eastern Pacific, were the most dominant. Half of the fish species found are commercially important to the artisanal fishery. Differences in fish community structure could be related to salinity differences, but other environmental and ecological factors could also play a role in explaining these differences. A better understanding of the ecological role of mangrove fishes in the region could be gained by examining the ichthyofauna of other habitats within the mosaic and their trophic relationships.(AU)

La ecorregión del Panama Bight (EPB) en el océano Pacifico oriental contiene probablemente los bosques de manglar más desarrollados de America. Los peces que habitan el mosaico estuario-manglar juegan papeles ecológicos fundamentales y sostienen las pesquerías artesanales que operan allí. Usando datos colectados a lo largo de ~300 km entre 2012 y 2017, examinamos la dinámica espacial de ensamblajes de peces de manglar que realizan migraciones intermareales en el EPB sur (costa sur del Pacífico colombiano), donde se encuentran los manglares más grandes y menos intervenidos de Colombia. Sesenta y un especies de peces ingresaron en zonas intermareales de manglar, constituyendo ~30% de todos los peces que pueden ser encontrados en el mosaico de hábitats de manglar de esta ecoregión. Especies de Clupeidae, Ariidae, Centropomidae y Tetraodontidae, todas comunes en manglares del Pacífico oriental, fueron las más dominantes. La mitad de los peces encontrados son importantes comercialmente para la pesquería artesanal. Las diferencias en la estructura de la comunidad pueden estar relacionadas con diferencias en salinidad, pero otros factores ambientales y ecológicos podrían también jugar un rol explicando las diferencias encontradas. Un mejor entendimiento del rol ecológico de los peces de manglar de la región podría alcanzarse examinando la ictiofauna de otros hábitats de este mosaico y sus relaciones tróficas.(AU)

Mangrove-associated fish assemblages off the southern Panama Bight region (tropical eastern Pacific)

The Panama Bight ecoregion (PBE) in the eastern Pacific contains probably the best developed mangrove forests in the American continent. Fishes inhabiting the mangrove-estuary mosaic play fundamental ecological roles and sustain the artisanal fishery operating there. Here, using data collected along ~300 km between 2012 and 2017, we examine the spatial dynamics of mangrove fish assemblages that undertake intertidal migrations in the southern part of the PBE (southern Colombian Pacific coast), where the largest and least disturbed mangroves of Colombia are located. Sixty-one fish species used intertidal mangrove habitats in these areas, constituting ~30% of all fishes inhabiting the whole mosaic of mangrove habitats in this ecoregion. Species within Clupeidae, Ariidae, Centropomidae and Tetraodontidae, all common in mangroves of the eastern Pacific, were the most dominant. Half of the fish species found are commercially important to the artisanal fishery. Differences in fish community structure could be related to salinity differences, but other environmental and ecological factors could also play a role in explaining these differences. A better understanding of the ecological role of mangrove fishes in the region could be gained by examining the ichthyofauna of other habitats within the mosaic and their trophic relationships.(AU)

La ecorregión del Panama Bight (EPB) en el océano Pacifico oriental contiene probablemente los bosques de manglar más desarrollados de America. Los peces que habitan el mosaico estuario-manglar juegan papeles ecológicos fundamentales y sostienen las pesquerías artesanales que operan allí. Usando datos colectados a lo largo de ~300 km entre 2012 y 2017, examinamos la dinámica espacial de ensamblajes de peces de manglar que realizan migraciones intermareales en el EPB sur (costa sur del Pacífico colombiano), donde se encuentran los manglares más grandes y menos intervenidos de Colombia. Sesenta y un especies de peces ingresaron en zonas intermareales de manglar, constituyendo ~30% de todos los peces que pueden ser encontrados en el mosaico de hábitats de manglar de esta ecoregión. Especies de Clupeidae, Ariidae, Centropomidae y Tetraodontidae, todas comunes en manglares del Pacífico oriental, fueron las más dominantes. La mitad de los peces encontrados son importantes comercialmente para la pesquería artesanal. Las diferencias en la estructura de la comunidad pueden estar relacionadas con diferencias en salinidad, pero otros factores ambientales y ecológicos podrían también jugar un rol explicando las diferencias encontradas. Un mejor entendimiento del rol ecológico de los peces de manglar de la región podría alcanzarse examinando la ictiofauna de otros hábitats de este mosaico y sus relaciones tróficas.(AU)

Linking fish and crustacean taxonomic composition with seasonal contrasts in the soft-bottom intertidal zone / Ligação da composição taxonômica de peixes e crustáceos com contrastes sazonais na zona intertidal de fundo macio

The primary objective of this study was to investigate the seasonal fish and crustacean variations concerning taxonomic composition, species richness, and diversity in sandy beach habitat. For this purpose, we investigated the Sonmiani Hor lagoon area during four distinct seasons, i.e., northeast (NE) monsoon, pre-monsoon, south-west (SW) monsoon, and post-monsoon for one year. During each haul, the net was pulled about 100m along the beach in 0.5m depth. The results showed a strong linear correlation between the diversity index and equitability in fishes (r = 0.978). The diversity index was strong negatively correlated with the abundance and biomass (r = -0.978, -0.972, respectively). The physical attributes like sea surface water temperature and salinity showed a strong negative effect on species assemblages (r = -0.981 and -0.943, respectively). The mean air and water temperature illustrated approximately 3°C difference during NE and pre-monsoon seasons. However, salinity, pH, and electrical conductivity did not show any significant seasonal variabilities. Under the ecological indices, the fish species displayed higher diversity (H = 3.19) during SW monsoon, whereas the lowest diversity was observed during pre-monsoon (H = 1.58). The equitability and species richness, however, remained more noticeable during SW monsoon (J = 0.81). The total number of individuals of fish and crustaceans reached 4799 with 3813 fish individuals and 986 individuals of crustaceans. A total of 27 families of fish while five crustacean families comprising of 30 genera and 38 fish species while ten genera and 17 species of crustaceans were recorded. Liza subviridis displayed the highest abundance among the sampled fish species. In conclusion, fish species constituted a significant part of the coastal fauna in the study area. The seasonal variations displayed distinct variations in fish species composition and diversity.(AU)

O objetivo principal deste estudo foi investigar as variações sazonais de peixes e crustáceos em relação à composição taxonômica, riqueza de espécies e diversidade no habitat de praias arenosas. Para esse fim, investigamos a área da lagoa Sonmiani Hor durante quatro estações distintas, ou seja, monção nordeste (NE), pré-monção, monção sudoeste (SW) e pós-monção, por um ano. Durante cada transporte, a rede foi puxada cerca de 100 m ao longo da praia, a 0,5 m de profundidade. Os resultados mostraram uma forte correlação linear entre o índice de diversidade e a equitabilidade de peixes (r = 0,978). O índice de diversidade apresentou forte correlação negativa com a abundância e a biomassa (r = -0,978 e -0,972, respectivamente). Os atributos físicos, como temperatura da água da superfície do mar e salinidade, apresentaram forte efeito negativo sobre o conjunto de espécies (r = -0,981 e -0,943, respectivamente). A temperatura média do ar e da água teve uma diferença de aproximadamente 3 °C durante a monção NE e a pré-monção. No entanto, salinidade, pH e condutividade elétrica não apresentaram variabilidade sazonal significativa. A respeito dos índices ecológicos, as espécies de peixes apresentaram maior diversidade (H = 3,19) durante a monção SW, enquanto a menor diversidade observada foi na pré-monção (H = 1,58). A equitabilidade e a riqueza de espécies, no entanto, permaneceram mais perceptíveis durante a monção SW (J = 0,81). O número total de peixes e crustáceos foi de 4.799, com 3.813 peixes e 986 crustáceos. Foram registradas 27 famílias de peixes e 5 famílias de crustáceos, com 30 gêneros e 38 espécies de peixes, além de 10 gêneros e 17 espécies de crustáceos. Liza subviridis apresentou a maior abundância entre as espécies de peixes amostradas. Em conclusão, as espécies de peixes constituíram uma parte significativa da fauna costeira na área de estudo. As variações sazonais apresentaram variações distintas na composição e diversidade das espécies de peixes.(AU)

Genome sequence of Streptomyces mangrovisoli MUSC 149T isolated from intertidal sediments

As the largest genus in Actinobacteria family, Streptomyces species have the ability to synthesize numerous compounds of diverse structures with bioactivities. Streptomyces mangrovisoli MUSC 149T was previously isolated as a novel streptomycete from mangrove forest in east coast of Peninsular Malaysia. The high quality draft genome of MUSC 149T comprises 9,165,825 bp with G + C content of 72.5%. Through bioinformatics analysis, 21 gene clusters identified in the genome were associated with the production of bioactive secondary metabolites. The presence of these biosynthetic gene clusters in MUSC 149T suggests the potential exploitation of the strain for production of medically important compounds.(AU)

Comparing the use of beach seine and cast net at characterizing intertidal fish fauna structure of a subtropical bay / Comparando o uso da picaré e tarrafa na caracterização da estrutura da ictiofauna do entremarés de uma baía subtropical

Although beach seines and cast nets are widely used to sample fishes in coastal marginal habitats, a comparison between such gears at determining fish fauna structure of tidal flats during high water is lacking. Here we compared the effectiveness of a multifilament beach seine and a monofilament cast net for sampling the intertidal fish assemblage structure of a subtropical bay in Brazil. We found an overall best performance for beach seine. In comparison to cast net, the beach seine sampled (I) a substantially greater density for the local dominant species, Atherinella brasiliensis; (II) a slightly greater density for juveniles of other conspicuous species, i.e. Mugil curema, Eucinostomus argenteus, Harengula clupeola, and Oligoplites saurus; (III) a higher total and mean richness; and (IV) higher the number and abundance of benthivores and higher the abundance of omnivores. The cast net better sampled the small planktivores, especially Sardinella brasiliensis juveniles. Such outcomes could support a future local fish-monitoring program and emphasize the great importance of evaluating the gear performance before starting fish sampling operations.

Embora redes-de-arrasto-de-praia (picarés) e tarrafas sejam amplamente utilizadas para amostragem de peixes em habitats marginais costeiros, ainda não há uma comparação entre tais petrechos para a determinação da estrutura da ictiofauna de planícies de maré durante a maré alta. Neste estudo, comparamos a efetividade de uma picaré de multifilamento com a efetividade de uma tarrafa de monofilamento para amostrar a estrutura da ictiofauna do entre-marés de uma baía subtropical do Brasil. A picaré apresentou um melhor desempenho geral. Em comparação com a tarrafa, a picaré amostrou (I) densidade substancialmente maior da espécie localmente dominante, Atherinella brasiliensis; (II) uma média densidade relativamente maior para juvenis das demais espécies localmente conspícuas, i.e., Mugil curema, Eucinostomus argenteus, Harengula clupeola e Oligoplites saurus (III); maiores valores da riqueza média e total; e (IV) melhor tanto a abundância de onívoros, quanto o número e a abundância de bentívoros. A tarrafa amostrou melhor os pequenos planctívoros, especialmente juvenis de Sardinella brasiliensis. Tais resultados poderão dar suporte a um futuro programa de monitoramento da ictiofauna local e enfatizam a grande importância da avaliação do desempenho de amostradores da ictiofauna antes de se iniciar quaisquer atividades de amostragem.

Comparing the use of beach seine and cast net at characterizing intertidal fish fauna structure of a subtropical bay / Comparando o uso da picaré e tarrafa na caracterização da estrutura da ictiofauna do entremarés de uma baía subtropical

Although beach seines and cast nets are widely used to sample fishes in coastal marginal habitats, a comparison between such gears at determining fish fauna structure of tidal flats during high water is lacking. Here we compared the effectiveness of a multifilament beach seine and a monofilament cast net for sampling the intertidal fish assemblage structure of a subtropical bay in Brazil. We found an overall best performance for beach seine. In comparison to cast net, the beach seine sampled (I) a substantially greater density for the local dominant species, Atherinella brasiliensis; (II) a slightly greater density for juveniles of other conspicuous species, i.e. Mugil curema, Eucinostomus argenteus, Harengula clupeola, and Oligoplites saurus; (III) a higher total and mean richness; and (IV) higher the number and abundance of benthivores and higher the abundance of omnivores. The cast net better sampled the small planktivores, especially Sardinella brasiliensis juveniles. Such outcomes could support a future local fish-monitoring program and emphasize the great importance of evaluating the gear performance before starting fish sampling operations.(AU)

Embora redes-de-arrasto-de-praia (picarés) e tarrafas sejam amplamente utilizadas para amostragem de peixes em habitats marginais costeiros, ainda não há uma comparação entre tais petrechos para a determinação da estrutura da ictiofauna de planícies de maré durante a maré alta. Neste estudo, comparamos a efetividade de uma picaré de multifilamento com a efetividade de uma tarrafa de monofilamento para amostrar a estrutura da ictiofauna do entre-marés de uma baía subtropical do Brasil. A picaré apresentou um melhor desempenho geral. Em comparação com a tarrafa, a picaré amostrou (I) densidade substancialmente maior da espécie localmente dominante, Atherinella brasiliensis; (II) uma média densidade relativamente maior para juvenis das demais espécies localmente conspícuas, i.e., Mugil curema, Eucinostomus argenteus, Harengula clupeola e Oligoplites saurus (III); maiores valores da riqueza média e total; e (IV) melhor tanto a abundância de onívoros, quanto o número e a abundância de bentívoros. A tarrafa amostrou melhor os pequenos planctívoros, especialmente juvenis de Sardinella brasiliensis. Tais resultados poderão dar suporte a um futuro programa de monitoramento da ictiofauna local e enfatizam a grande importância da avaliação do desempenho de amostradores da ictiofauna antes de se iniciar quaisquer atividades de amostragem.(AU)

Patterns of mollusc distribution in mangroves from the São Marcos Bay, coast of Maranhão State, Brazil / Padrões de distribuição de moluscos em manguezais da Baía de São Marcos, costa do Estado do Maranhão, Brasil

The diversity and distribution of molluscs from the Amazon Coast of Maranhão State, Brazil, are poorly understood. The aim of this study was to investigate how molluscs in two mangrove creeks (Buenos Aires and Tronco) at the São Marcos Bay, coast of the Maranhão State, respond to spatial and temporal variations in the environment. Sampling was performed in the intertidal area along three zones established using a straight line transect of 100 m. Abiotic variables of water and sediment were measured at each creek. We found 5,912 specimens belonging to 23 species and 15 families of epifaunal and infaunal molluscs. The patterns of their distribution in the two creeks were different. Salinity, dissolved oxygen, and rainfall were the main variables that affected the temporal distribution of molluscs. We found low species richness in the overall mollusc composition. Diversity in the Buenos Aires Creek was lower than that observed in the Tronco Creek, possibly because of activities of a port located in proximity to the former. The spatial distribution of molluscs along the zones followed an abundance and diversity gradient, mainly influenced by exposure time during low tide. Port activities may influence the patterns of mollusc distribution in the surrounding mangroves, and we thus highlight the importance of management and monitoring of these areas.(AU)

A diversidade e distribuição de moluscos na Costa Amazônica do Estado do Maranhão, Brasil, são pobremente conhecidas. O objetivo deste estudo foi investigar como os moluscos em dois igarapés de manguezal (Buenos Aires e Tronco) na Baía de São Marcos, costa do Estado do Maranhão, respondem a variações espaciais e temporais no ambiente. A amostragem foi conduzida no entre-marés ao longo de três zonas estabelecidas a partir de um transecto em linha reta de 100 m. As variáveis abióticas de água e sedimento foram medidas para cada igarapé. Foram contabilizados 5.912 espécimes pertencentes a 23 espécies e 15 famílias na epifauna e endofauna. Os padrões de distribuição de moluscos foram distintos entre os dois igarapés. Salinidade, oxigênio dissolvido e precipitação foram as principais variáveis que influenciaram a distribuição temporal dos moluscos. Observou-se baixa riqueza de espécies na composição geral de moluscos. A diversidade no igarapé Buenos Aires foi menor do que a observada no igarapé Tronco, possivelmente por causa das atividades portuárias nas proximidades do primeiro. A distribuição espacial vertical de moluscos ao longo das zonas seguiu um gradiente de abundância e diversidade influenciado principalmente pelo tempo de exposição durante a maré baixa. As atividades portuárias podem estar influenciando os padrões de distribuição de moluscos nos manguezais do entorno, portanto destacamos a importância do manejo e monitoramento dessas áreas.(AU)

Patterns of mollusc distribution in mangroves from the São Marcos Bay, coast of Maranhão State, Brazil / Padrões de distribuição de moluscos em manguezais da Baía de São Marcos, costa do Estado do Maranhão, Brasil

The diversity and distribution of molluscs from the Amazon Coast of Maranhão State, Brazil, are poorly understood. The aim of this study was to investigate how molluscs in two mangrove creeks (Buenos Aires and Tronco) at the São Marcos Bay, coast of the Maranhão State, respond to spatial and temporal variations in the environment. Sampling was performed in the intertidal area along three zones established using a straight line transect of 100 m. Abiotic variables of water and sediment were measured at each creek. We found 5,912 specimens belonging to 23 species and 15 families of epifaunal and infaunal molluscs. The patterns of their distribution in the two creeks were different. Salinity, dissolved oxygen, and rainfall were the main variables that affected the temporal distribution of molluscs. We found low species richness in the overall mollusc composition. Diversity in the Buenos Aires Creek was lower than that observed in the Tronco Creek, possibly because of activities of a port located in proximity to the former. The spatial distribution of molluscs along the zones followed an abundance and diversity gradient, mainly influenced by exposure time during low tide. Port activities may influence the patterns of mollusc distribution in the surrounding mangroves, and we thus highlight the importance of management and monitoring of these areas.

A diversidade e distribuição de moluscos na Costa Amazônica do Estado do Maranhão, Brasil, são pobremente conhecidas. O objetivo deste estudo foi investigar como os moluscos em dois igarapés de manguezal (Buenos Aires e Tronco) na Baía de São Marcos, costa do Estado do Maranhão, respondem a variações espaciais e temporais no ambiente. A amostragem foi conduzida no entre-marés ao longo de três zonas estabelecidas a partir de um transecto em linha reta de 100 m. As variáveis abióticas de água e sedimento foram medidas para cada igarapé. Foram contabilizados 5.912 espécimes pertencentes a 23 espécies e 15 famílias na epifauna e endofauna. Os padrões de distribuição de moluscos foram distintos entre os dois igarapés. Salinidade, oxigênio dissolvido e precipitação foram as principais variáveis que influenciaram a distribuição temporal dos moluscos. Observou-se baixa riqueza de espécies na composição geral de moluscos. A diversidade no igarapé Buenos Aires foi menor do que a observada no igarapé Tronco, possivelmente por causa das atividades portuárias nas proximidades do primeiro. A distribuição espacial vertical de moluscos ao longo das zonas seguiu um gradiente de abundância e diversidade influenciado principalmente pelo tempo de exposição durante a maré baixa. As atividades portuárias podem estar influenciando os padrões de distribuição de moluscos nos manguezais do entorno, portanto destacamos a importância do manejo e monitoramento dessas áreas.

Ocorrência e recrutamento larval de Teredinidae (Mollusca, Bivalvia) na região do Sistema Costeiro Cananéia-Iguape, São Paulo, Brasil / The occurrence and larval recruitment of Teredinidae (Mollusca, Bivalvia) in Cananeia-Iguape Coastal System, São Paulo, Brazil

The occurrence and larval settlement of Teredinidae in Cananéia-Iguape Coastal System were observed for one year, by using laminated pinewood panels installed in three stations inside the mangrove forest (intertidal zone) and in one station, in the infralittoral. In the mangrove forest, the larval colonization occurred after four months in the most frequently flooded station and after eight months in the two less frequent flooded stations. In the infralittoral, the panels were highly infested after four months. Along the experiment, the number of individuals decreased, especially in the infralittoral, possibly due to competition between teredinids and pholadids for wood. Bankia fimbriatula was the most abundant teredinid, occurring in the infralittoral and in the mangrove area, followed by Bankia gouldi and Lyrodus floridanus, which occurred only in the infralittoral and Nausitora fusticula which was found only in the mangrove forest. In total, 704 individuals of Teredinidae were collected. Martesia striata, the single pholadid, was found in the infralittoral, and totaled 2,658 individuals(AU)

A ocorrência e o recrutamento larval de Teredinidae na região do Sistema Costeiro Cananéia-Iguape foram acompanhados por doze meses utilizando-se coletores laminados de pinho, instalados em três estações dentro do bosque de mangue (mediolitoral) e em uma estação, localizada no infralitoral. No manguezal, a colonização por larvas de teredinídeos ocorreu após quatro meses de permanência dos coletores na estação mais frequentemente inundada pela maré e somente após oito meses nas duas estações com menor frequência de inundação. No infralitoral, após quatro meses, os coletores já estavam consideravelmente danificados. Ao longo do experimento, houve um decréscimo no número de teredinídeos, especialmente no infralitoral, ocasionado possivelmente pela competição por alimento e espaço entre teredinídeos e foladídeos. Foram encontrados 2.658 indivíduos, sendo 704 de Teredinidae e 1.954 de Pholadidae. Entre os teredinídeos, Bankia fimbriatula foi a espécie mais abundante tanto no infralitoral quanto no manguezal, seguida de Bankia gouldi e Lyrodus floridanus que ocorreram somente no infralitoral, e Nausitora fusticula encontrada somente no manguezal. Martesia striata, único foladídeo, ocorreu somente no infralitoral(AU)

Ocorrência e recrutamento larval de Teredinidae (Mollusca, Bivalvia) na região do Sistema Costeiro Cananéia-Iguape, São Paulo, Brasil / The occurrence and larval recruitment of Teredinidae (Mollusca, Bivalvia) in Cananeia-Iguape Coastal System, São Paulo, Brazil

The occurrence and larval settlement of Teredinidae in Cananéia-Iguape Coastal System were observed for one year, by using laminated pinewood panels installed in three stations inside the mangrove forest (intertidal zone) and in one station, in the infralittoral. In the mangrove forest, the larval colonization occurred after four months in the most frequently flooded station and after eight months in the two less frequent flooded stations. In the infralittoral, the panels were highly infested after four months. Along the experiment, the number of individuals decreased, especially in the infralittoral, possibly due to competition between teredinids and pholadids for wood. Bankia fimbriatula was the most abundant teredinid, occurring in the infralittoral and in the mangrove area, followed by Bankia gouldi and Lyrodus floridanus, which occurred only in the infralittoral and Nausitora fusticula which was found only in the mangrove forest. In total, 704 individuals of Teredinidae were collected. Martesia striata, the single pholadid, was found in the infralittoral, and totaled 2,658 individuals

A ocorrência e o recrutamento larval de Teredinidae na região do Sistema Costeiro Cananéia-Iguape foram acompanhados por doze meses utilizando-se coletores laminados de pinho, instalados em três estações dentro do bosque de mangue (mediolitoral) e em uma estação, localizada no infralitoral. No manguezal, a colonização por larvas de teredinídeos ocorreu após quatro meses de permanência dos coletores na estação mais frequentemente inundada pela maré e somente após oito meses nas duas estações com menor frequência de inundação. No infralitoral, após quatro meses, os coletores já estavam consideravelmente danificados. Ao longo do experimento, houve um decréscimo no número de teredinídeos, especialmente no infralitoral, ocasionado possivelmente pela competição por alimento e espaço entre teredinídeos e foladídeos. Foram encontrados 2.658 indivíduos, sendo 704 de Teredinidae e 1.954 de Pholadidae. Entre os teredinídeos, Bankia fimbriatula foi a espécie mais abundante tanto no infralitoral quanto no manguezal, seguida de Bankia gouldi e Lyrodus floridanus que ocorreram somente no infralitoral, e Nausitora fusticula encontrada somente no manguezal. Martesia striata, único foladídeo, ocorreu somente no infralitoral

A new look into the small-scale dispersal of free-living marine nematodes

We tested experimentally the hypothesis that prevailing locomotion/feeding strategies and body morphology may lead to more active dispersal of free-living marine nematodes, besides passive transport. Neutral Red was applied to the sediment inside cores and the red plume formed during the flood tide was divided into near, middle, and distant zones. At 0.5 m and 1 m from the stained cores, sampling nets were suspended 5 and 10 cm above the sediment-water interface. Dispersion behaviors were defined as a function of a) the numbers of stained recaptured nematodes in comparison to their mean densities in the sediment, b) movement in the sediment or swimming in the water column, and c) body morphology. Tidal currents with average velocities of 9 cm/s resuspended the numerically dominant nematode taxa Sabatieria sp., Terschellingia longicaudata de Man, 1907, Metachromadora sp. and Viscosia sp. The recapture of stained nematodes as far as 2 m from the original stained cores showed that, despite their small body size, they can disperse through relatively large distances, either passively or actively, via the water column during a single tidal event. Recapture patterns in the sediment and in the water column indicate that nematode dispersal is directly influenced by their body morphology and swimming ability, and indirectly by their feeding strategies, which ultimately define their position in the sediment column. Besides stressing the role played by passive transport in the water column, our experiment additionally showed that mobility and feeding strategies also need to be considered as determinant of short-scale nematode dispersal.

A new look into the small-scale dispersal of free-living marine nematodes

We tested experimentally the hypothesis that prevailing locomotion/feeding strategies and body morphology may lead to more active dispersal of free-living marine nematodes, besides passive transport. Neutral Red was applied to the sediment inside cores and the red plume formed during the flood tide was divided into near, middle, and distant zones. At 0.5 m and 1 m from the stained cores, sampling nets were suspended 5 and 10 cm above the sediment-water interface. Dispersion behaviors were defined as a function of a) the numbers of stained recaptured nematodes in comparison to their mean densities in the sediment, b) movement in the sediment or swimming in the water column, and c) body morphology. Tidal currents with average velocities of 9 cm/s resuspended the numerically dominant nematode taxa Sabatieria sp., Terschellingia longicaudata de Man, 1907, Metachromadora sp. and Viscosia sp. The recapture of stained nematodes as far as 2 m from the original stained cores showed that, despite their small body size, they can disperse through relatively large distances, either passively or actively, via the water column during a single tidal event. Recapture patterns in the sediment and in the water column indicate that nematode dispersal is directly influenced by their body morphology and swimming ability, and indirectly by their feeding strategies, which ultimately define their position in the sediment column. Besides stressing the role played by passive transport in the water column, our experiment additionally showed that mobility and feeding strategies also need to be considered as determinant of short-scale nematode dispersal.

A new look into the small-scale dispersal of free-living marine nematodes

We tested experimentally the hypothesis that prevailing locomotion/feeding strategies and body morphology may lead to more active dispersal of free-living marine nematodes, besides passive transport. Neutral Red was applied to the sediment inside cores and the red plume formed during the flood tide was divided into near, middle, and distant zones. At 0.5 m and 1 m from the stained cores, sampling nets were suspended 5 and 10 cm above the sediment-water interface. Dispersion behaviors were defined as a function of a) the numbers of stained recaptured nematodes in comparison to their mean densities in the sediment, b) movement in the sediment or swimming in the water column, and c) body morphology. Tidal currents with average velocities of 9 cm/s resuspended the numerically dominant nematode taxa Sabatieria sp., Terschellingia longicaudata de Man, 1907, Metachromadora sp. and Viscosia sp. The recapture of stained nematodes as far as 2 m from the original stained cores showed that, despite their small body size, they can disperse through relatively large distances, either passively or actively, via the water column during a single tidal event. Recapture patterns in the sediment and in the water column indicate that nematode dispersal is directly influenced by their body morphology and swimming ability, and indirectly by their feeding strategies, which ultimately define their position in the sediment column. Besides stressing the role played by passive transport in the water column, our experiment additionally showed that mobility and feeding strategies also need to be considered as determinant of short-scale nematode dispersal.

Population biology and distribution of the tanaid Kalliapseudes schubarti Mañé-Garzon, 1949, in an intertidal flat in Southeastern Brazil

The population biology and the spatial and temporal distribution of Kalliapseudes schubarti Mañé-Garzon, 1949, a common tanaidacean in mud flats and estuaries in southern and southeastern Brazil, was studied in the Araçá region, São Sebastião (SP), Brazil. This species showed a clustered dispersion in the area and the individuals were concentrated in the superficial sediment layer (5 cm). Higher densities of K. schubarti were recorded in areas characterized by moderately sorted fine sediment. Multiple regression analysis revealed a positive influence of the organic matter contents and a negative effect of the silt-clay contents on the abundance of K. schubarti. This species showed a marked temporal variation with very low abundance in winter and fall (March to August). Sexual dimorphism was evidenced with males being larger than females. Ovigerous females were also larger than pre-ovigerous ones. Sex ratio was skewed towards females. Seven cohorts were identified during the sampling period, the estimated longevity was 12 months, and no seasonal oscillation in growth was evidenced. The continuous reproduction, as evidenced by the presence of larval phases (manca II and neutron) and reproductive females throughout the year, and high fecundity among the tanaids associated with fast growth and limited longevity support the case for the opportunistic life strategy suggested for this species in the literature.

A biologia populacional e a distribuição espacial e temporal de Kalliapseudes schubarti Mañé-Garzon, 1949, tanaidáceo comum em estuários e planícies lodosas do Sul e Sudeste do Brasil, foi estudada na região do Araçá, São Sebastião (SP), Brasil. Essa espécie apresentou distribuição agrupada na área amostrada e os indivíduos concentraram-se na camada superficial (5 cm) do sedimento. Altas densidades de K. schubarti foram obtidas em áreas caracterizadas por sedimento fino e moderadamente selecionado. A análise de regressão múltipla revelou influência positiva dos teores de matéria orgânica e efeito negativo dos teores de silte-argila sobre a abundância de K. schubarti. Além disso, essa espécie apresentou variação temporal com diminuição em abundância no outono e inverno (março a agosto). Um dimorfismo sexual foi verificado, com machos sendo maiores que fêmeas. Fêmeas ovígeras também foram maiores que as pré-ovígeras. A razão sexual mostrou-se desviada para fêmeas. Sete coortes foram identificadas durante o período de amostragem. A longevidade estimada para K. schubarti foi de 12 meses e nenhuma oscilação sazonal no crescimento foi comprovada. A reprodução contínua, evidenciada pela presença de fases larvais (manca II e nêutron) e fêmeas reprodutivas ao longo do ano, e a alta fecundidade dentre os tanaidáceos, associada ao rápido crescimento e à pequena longevidade, suportam uma estratégia de vida oportunista sugerida para essa espécie na literatura.