Population biology of Uca thayeri Rathbun, 1900 (Brachyura, Ocypodidae) in a subtropical South American mangrove area: Results from transect and catch-per-unit-effort techniques

The population biology of Uca thayeri was studied in a subtropical mangrove in Ubatuba, State of São Paulo, Brazil. Two sampling techniques were used: transect sampling and catch-per-unit-effort. Size frequency distribution, sex-ratio, and reproductive period were analysed. For juvenile crabs (CW < 4.6 mm), the transect procedure was most efficient, while ovigerous females were most collected during the capture effort. Males were most numerous in the transect technique, while in the catch-per-unit-effort there was no difference between sexes. The species showed a different size frequency distribution for each sampling procedure. The reproduction of U. thayeri is seasonal, being more pronounced in the warmer months of the year. However, juveniles occurred all over the year, although more numerous in the colder months. The success of the species in reproductive activity and the constant colonization of the area can be attributed to the availability of food resources and differential occupation of the habitat by ovigerous females.

Reproductive output of Uca vocator (Herbst, 1804) (Brachyura, Ocypodidae) from three subtropical mangroves in Brazil

Crab fecundity is widely known to vary proportionally to female size, but the female's nutritional state also has an important effect on egg production. This study evaluates intraspecific variability of reproductive output by monthly sampling Uca vocator populations from the Itapanhau, Indaia, and Itamambuca mangroves on the southeastern coast of Brazil. The presence of ovigerous crabs, their carapace width (CW) and their number of eggs were recorded. Additionally, the productivity of the mangroves and the content of organic matter of the sediments were analysed in order to estimate food availability in each locality. Size-specific fecundity relationships were obtained for each population and compared among the three populations. Ovigerous females from Itamambuca are the largest and their fecundities are also the highest among the populations studied. These results probably are associated with the favourable environmental conditions in Itamambuca, as this is a young mangrove with a high productivity level.

A comparison of the allometric growth in Uca leptodactyla (Crustacea : Brachyura : Ocypodidae) from two subtropical estuaries

The allometric growth of Uca leptodacyla from two distinct subtropical estuaries on the Brazilian coast was evaluated concerning its growth pattern and size at onset of sexual maturity. Females attained maturity at similar sizes in both sites (4.1 mm of carapace length in Indaia and 4.2 mm in Ubatumirim), while males differed slightly. They reached the size at sexual maturity of 5.3 mm of carapace length in Indaia and 4.6 mm in Ubatumirim. Growth pattern is Usually similar among crabs from distinct Sites while size at sexual maturity is frequently different. However, in the case of U. leptodacyla it did not occur, probably due to the strong habitat similarity and intrinsic features of this species.

Diel variations in decapod catch rate and size of captured individuals in a subtropical area of Brazil

Diel variations in decapod crustaceans catch rate, as well as variations in size of sampled individuals, were investigated in a sublittoral portion of Ubatuba Bay (23 degrees 20', 23 degrees 35'S and 44 degrees 50', 45 degrees 14'W) in order to detect differential patterns of occurrence. Three replicate trawls, each enclosing a 2,500 m(2) area, were performed at a median depth of 3.5 m during the waning moon period, in 3 consecutive summer and winter months. Trawls were conducted at dawn, noon, dusk and midnight. Hydrological and substratum features were monitored. Penaeoideans did not show a significant diel catch rate variation during the sampling periods, but the catch rate of brachyurans was highest at dusk and midnight during winter (p < 0.01). Fixing diel variation, catch rates of both brachyurans and penaeoideans are subjected to significant seasonal differences (p < 0.05). The largest specimens of Callinectes ornatus, Xiphopenaeus kroyeri, Rimapenaeus constrictus and Farfantepenaeus spp were found at twilight during summer. Differences on size of captured individuals mainly in samples of portunids and penaeids taken during the course of the day evidences that significant daily movements take place. This confirms that activity alterations depend on characteristics of daily schedules and on environmental demands of studied species.

Size variation in the grapsid crab Aratus pisonii (H. Milne-Edwards, 1837) among populations of different subtropical mangroves

Size variation in the adult population of the grapsid crab Aratus pisonii (H. Milne-Edwards, 1837) was studied by comparing median values obtained from six different populations from nearby mangrove areas. The mangrove structure at those sites was also examined and related to size differences among populations. Disregarding sex, crab size is apparently related to the mangrove structure. Smallest and largest crab sizes were recorded at the sites where tree density and tree diameter were minimum and maximum, respectively. Estimates of size at the onset of maturity, considering the size of the smallest ovigerous female, followed the same trend. These results support the hypothesis that average crab size and size at the onset of maturity can be associated to mangrove productivity.

On the population biology of the mottled shore crab Pachygrapsus transversus (Gibbes, 1850) (Brachyura, Grapsidae) in a subtropical area

The mottled shore crab P. transversus is probably the most common brachyuran crab living in the marine rocky intertidal of southeastern Brazil. However, its biology is largely unknown. In this study, some aspects of the population biology of this species are investigated. Distribution of individuals in the intertidal range is heterogeneous. Sabellariid worm reefs and mytilid mussel beds can be considered as nursery grounds retaining most part of juveniles, while the rocky surface is mostly inhabited by adults, which find safety shelters in rock crevices. Annual size frequency distributions revealed clues of population stability and indicated that young individuals reach the adult habitat in a gradual process. Sex-ratio follows the 1:1 proportion in smaller size classes but is biased towards males in larger ones. Higher mortality in larger females is indicated as a possible cause of this pattern. Ovigerous ratio shows a remarkable seasonality in which highest percentages of ovigerous females occur during summer months, while recruitment of young is more intense from April to July, suggesting a very extensive larval development. Once established in the intertidal zone, young recruits will develop to mature individuals in late spring, when molting crabs become scarce and proportion of breeding females increases. Therefore, growth and reproduction are in a great part temporally separated, allowing an annual life cycle in which settlement, growth and breeding may take place within a I-yr period.

A morphometric study of the mud crab, Panopeus austrobesus Williams, 1983 (Decapoda, Brachyura) from a subtropical mangrove in South America

The relative growth of the xanthid crab, Panopeus austrobesus was investigated by means of the allometric method. Crabs were obtained in the mangrove formed by the estuary of the rivers Comprido and Escuro (23degrees29'24S 45degrees10'12W), Ubatuba, São Paulo State, Brazil. All crabs were measured to obtain their carapace width (CW) and length (CL), abdomen width (AW) at the basis of the 5(th) somite, and major cheliped propodus length (PL) and height (PH). Males were also measured for their gonopod length (GL). The size of crabs based on CW ranged from 4.0 to 44.8 mm for males and 3.1 to 34.5 mm for females. The relative growth equation (Y = aX(b)) based on the relationship between GL and CW suggested that males reach their sexual maturity near 14.6 mm CW. Such relationship shows a positive allometry during the juvenile phase and an isometric growth in adult life. In females, the estimated size at 50% maturity is 13.0 mm CW, based on the relationship AW vs. CW. Males reach larger sizes than females, which probably provides them better conditions to protect females during courtship. Concerning cheliped size, approximately 73% of the crabs analysed (N = 209), disregarding sex, have the right PL larger than the left. The PL growth shows that specimens with a left major cheliped (26%) have a higher allometric coefficient, despite being smaller considering their CW. Such a difference may compensate the smaller size of the crab during defense or prey capture.

Sexual maturity of Eurytium limosum (say 1818) from a subtropical mangrove in Brazil

The size at onset of maturity of Eurytium limosum from a subtropical mangrove in Brazil was investigated. In this species, sexual maturity for males can be indicated by the allometric growth and gonopod length. For females, the morphological sexual maturity can only be externally verified through the relative quantity of setae along the abdominal margins and pleopods. Internally, gonad development was also examined. The size at which half of the population is physiologically mature was 11.6 mm of CW for females and 12.3 mm of CW for males. The values for the morphological and physiological maturity are very similar, indicating that the development of the secondary sexual characters is synchronized with the achievement of the physiological maturity for E. limosum.

Structural description of humic substances from subtropical coastal environments using elemental analysis, FT-IR and C-13-solid state NMR data

Elemental composition and spectroscopic properties (FT-IR and CP/MAS C-13-NMR) of sedimentary humic substances (HS) from aquatic subtropical environments (a lake, an estuary and two marine sites) are investigated. Humic acids (HA) are relatively richer in nitrogen and in aliphatic chains than fulvic acids (FA) from the same sediments. Conversely, FA are richer in carboxylic groups and in ring polysaccharides than HA. Nitrogen is mostly present as amide groups and for lake and marine HS the FT-IR peaks around 1640 cm(-1) and 1540 cm(-1) identify polypeptides. Estuarine HS exhibit mixed continental-marine influences, these being highly influenced by site location. Overall, the data suggest that aquatic and mixed HS are more aliphatic than has been proposed in current models and also that amide linkages form an important part of their structural configuration.

Phytoplankton assemblages in a reservoir cascade of a large tropical - subtropical river (SE, Brazil)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Population biology of spine shrimp Exhippolysmata oplophoroides (Holthuis) (Caridea, Hippolytidae) in a subtropical region, São Paulo, Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Subtropical Brazilian mangroves as a refuge of crab (Decapoda: Brachyura) diversity

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Lek phenology of the White-bearded Manakin (Manacus manacus, Aves: Passeriformes: Pipridae) in a subtropical region

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Distribuição temporal e espacial de anuros em área de Pampa, Santa Maria, RS

Este estudo teve como objetivo determinar a riqueza, a constância de ocorrência, os modos reprodutivos, o padrão de distribuição da abundância, a temporada de vocalização e testar a correlação das variáveis climáticas sobre a atividade de vocalização dos anuros em uma região do Bioma Pampa, Santa Maria, Rio Grande do Sul. Durante o período de novembro de 2001 a outubro de 2002 foram realizadas coletas mensais empregando o método de busca em sítio de reprodução e exame de exemplares depositados na Coleção Herpetológica do Setor de Zoologia da Universidade Federal de Santa Maria (UFSM) (ZUFSM). Foi registrada a ocorrência de 25 espécies de anuros. A anurofauna registrada corresponde a 30% das espécies encontradas no Rio Grande do Sul e normalmente está associada a áreas abertas encontradas no estado e em países vizinhos. Foram registrados quatro modos reprodutivos: modo 1 (14 espécies; 58,3%); modos 11 e 30 (nove espécies; 37,5%) e modo 24 (uma espécie; 4,2%). A baixa diversificação de modos reprodutivos provavelmente está relacionada à homogeneidade do hábitat primariamente campestre. A maior parte das espécies mostrou-se constante ou acessória na área estudada e o padrão de distribuição da abundância das espécies apresentou ajuste aos modelos Broken Stick e Log-normal, caracterizados pela homogeneidade na distribuição da abundância das espécies. A maioria das espécies apresentou grande plasticidade na ocupação de hábitats, mas poucas foram plásticas no uso dos sítios de vocalização. Houve correlação positiva, ainda que fraca, da riqueza de espécies com a precipitação mensal acumulada e da abundância com a temperatura média máxima. As correlações obtidas indicaram que na área estudada a temperatura parece atuar mais sobre a abundância de machos em atividade de vocalização e a precipitação sobre a riqueza, apesar da riqueza de espécies ser significativamente maior durante o período mais quente do ano. Estes resultados revelaram que as variáveis climatológicas testadas explicaram muito pouco da ocorrência sazonal das espécies, assim a influência de outras variáveis ambientais merece ser testada em estudos futuros.