Abstract in English:Population rates of the three dominant amphipod species (Hyale nigra, Caprella danileviskii and Caprella penantis) associated to Bryocladia thrysigera, were calculated revealing similar values for the intrinsic growth rate. The empirical data modeled presented a good fit to the May-Leonard three-species competition model in a discrete Ricker form with periodic cycles for the carrying capacity. In adjusting model to data, a new method to calculate competition coefficients emerged in good agreement with ecological and behavior particularities. A simulation of environmental stochasticity was achieved by the insertion of random parameters for the calculation of each species carrying capacity. H. nigra presented a persistent behavior in extreme environmental stress, whereas C. penantis is highly sensitive to stress.
Abstract in English:The factors that influence the selection of marine macrophytes by meso-herbivores are complex, and may include the nutritional quality of algae, the value of the habitat as a shelter, and the availability of algae in the environment. Here we investigated the existence of differential use of Sargassum filipendula C. Agardh, 1824 (Phaeophyta) and Galaxaura stupocaulon Kjellman, 1900 (Rhodophyta) as habitats and feeding resources by species of Hyalidae and Ampithoidae, in laboratory manipulation experiments and in an algal bed on the northern coast of the state of São Paulo, Brazil. In the field, 19 fronds were collected from each alga and the associated amphipods were identified and counted. To evaluate food preference and habitat selection by amphipods, we conducted laboratory experiments using containers containing fragments of algae and individuals of Cymadusa filosa Savigny, 1816 or Hyale nigra (Haswell, 1879). In natural conditions, the density of C. filosa was significantly higher on G. stupocaulon, while in the feeding and habitat preference experiment we found a higher density on S. filipendula. The densities of H. nigra did not differ between the algae in both experiments, probably as a result of the variety of food items in its diet, and its high mobility and wide distribution on different substrates. The different results for C. filosa suggest that the pattern of feeding and habitat selection can be affected by external characteristics of the algae; probably, refuge from predation is an important selective force acting on the use of algae by these animals.
Abstract in English:The preference for a particular type of prey implies an active behavioral choice of the predator. The present work deals with the prey preference of the large stone crab Platyxanthus crenulatus among similar sized gastropods and bivalves of different substrates using a recent proposed methodology based on a two-stage approach. In laboratory, crabs received different mollusk species separately to determine the consumption in number of each species when choice was not possible. Further, crabs were offered the same mollusc species but together to record differences of specific consumption when choice was possible. Results were then compared to assess prey preferences. Platyxanthus crenulatus is able to effectively attack and consume the majority of the sympatric mollusk species, although preferred the dominant species Brachidontes rodriguezii over the others. Such preference seems to be driven by shell shape and thickness which may be a common pattern in prey preference among large stone crab species.
Abstract in English:Macrobrachium brasiliense is a cosmopolitan shrimp species found in the channel of large rivers, streams, lakes, igapós and upland igarapés and can present diversity in the use of food resources. This study aimed to evaluate the feeding habits according to sex, molt stage, seasonal and spatial variation, and size class. Organisms were collected every three months from May 2011 to March 2012 at three sampling sites in the Curral de Arame Stream, including the upstream, middle, and downstream sections. Animals were sampled with 50x50cm sieves (1 mm mesh size) on the margin, and with "D" dip nets 40 cm wide (500 µm mesh size) at the bottom. Of each animal we examined the sex, molt stage, carapace length, and stomach content. Data were analyzed through the frequency of occurrence and compared by a chi-square test. Four-hundred-thirty shrimps were collected, of which 26.05% male and 73.95% female; of the total males, 69.64% showed content in the stomach, and females, 72.96%. Among food items stood out: Non-identified Organic Matter (90%), Insects (89.68%), Sand (87.10%), Algae (49.03%), Oligochaeta (29.68%), Fungi (26.77%) and Plant fragment (14.52%). No significant difference was detected in the diet between males and females, but there was a seasonal difference related to the molt stage, and differences along the space and per size classes, and it was concluded that the species has omnivorous habits.
Abstract in English:A study on the relative growth was carried out in a population of the fiddler crab Uca uruguayensis from the mangrove of Garças River, Guaratuba Bay, Paraná State, southern Brazil. The dimensions analyzed were the length of the major chela (LMC) of males and width of the abdomen (AW) of females, because they are related to reproductive activities of waving (males) and egg incubation (females). The cheliped handedness in males was also analyzed. The LMC was measured in 480 males, the AW in 566 females, and all crabs had the carapace width (CW) measured that was considered as the reference dimension for both sexes. The inflection point in the graphs between each the dimensions and CW was calculated with the aid of the software REGRANS. The CW ranged from 2.33 to 8.33 mm in males and from 1.65 to 7.79 mm in females. The relationship between CW and LMC showed an inflection point at 4.14 mm CW among males, and between CW and AW at 3.52 mm CW among females. The allometric growth was positive for both dimensions throughout the entire ontogeny of both sexes, before and after the puberty. The equations describing the relationship between CW and LMC in males were: logLMC = - 0.695960 + 1.72.logCW for juveniles and logLMC = - 1.212513 + 2.5.logCW for adults. In females, the equations were logAW = - 0.519071 + 1.02.logCW and logAW = - 0.902874 + 1.73.logCW, respectively for juveniles and adults. The population of U. uruguayensis from Guaratuba Bay is composed of the smallest crabs, and it also attains morphological sexual maturity at smallest CW. The frequency of occurrence of right and left handed males was statistically the same (1:1) as in most population of fiddler crabs.
Abstract in English:This work aims to estimate the average size at the onset of morphological and physiological sexual maturity and the reproductive period of Callinectes danae. Specimens were captured from a shrimp fishing boat equipped with a trawl net from March 2009 to February 2010. After sorting, crabs were sexed, and the following morphometric dimensions were measured: carapace width (CW), length and height of the major (MAP and HMAP), and the minor cheliped propodus (MIP and HMIP) for both sexes, and the abdominal width for females (AW). The onset of morphological maturity was estimated with the REGRANS program, in which the inflection point is calculated. The size at the onset of physiological maturity was determined by logistic regressions fitted to the relationships between the percentages of juvenile and adult individuals of each CW. A total of 893 individuals were sampled. Of these individuals, 389 were males, 472 non-ovigerous females, and 32 ovigerous females. The CW ranged from 19.81 to 117.17 mm for males, 19.91 to 113.11 mm for non-ovigerous females, and 70.55 to 88.60 mm for ovigerous females. Morphological sexual maturity was attained at 86.47 mm CW (males) and 67.87 mm CW (females). The size at the onset of physiological maturity was calculated to be 86.50 mm CW (males) and 67.00 mm CW (females). Due to the closeness of these values, both techniques were deemed suitable for determination of the onset of sexual maturity in C. danae. This species reproduces throughout the year, but reproduction is more intense during the winter. Mature males are present throughout the year. Data from this investigation will help resource managers to develop strategies that will ensure a sustainable harvest of this important species of swimming crab in southern Brazil.
Abstract in English:A new species of the amphipod family Ampithoidae Stebbing, 1899 is described from the northeastern Brazilian waters. The new described taxon is grouped in the genus Cymadusa Savigny, 1816, since it presents all the diagnostic characteristics of the genus. The examined material was collected by scuba diving in the Rocas Atoll, off Rio Grande do Norte state coast, Camamu Bay and Todos os Santos Bay, Bahia state. The new species described here is close to C. filosa Savigny, 1816, type species of the genus, by presenting anterior margin of gnathopod 1 poorly setose, male gnathopod 2 densely setose, with palmar corner not defined by a spine and dactylus subequal in length to palm, being considered part of the C. filosa complex. Among the species of this complex, the one which most resembles to the new taxon is C. imbroglio Rabindranath, 1972, which is distinguished by the absence of both the trapezoid process in the palm and spine at the palmar corner in the gnathopod 2. This is the second species of the genus Cymadusa recorded from Brazilian waters.
Abstract in English:The aim of this study was to describe the composition and structure of cladocerans of littoral areas with and without macrophytes from a temporary shallow pond in the Caatinga of Pernambuco state (Brazil). Samples were taken between June 2011 and August 2012. The sampling of cladocerans and environmental variables was performed at four fixed points, using a plankton net (45 µm) and a multiparameter probe. Twenty-two cladoceran species were recorded, with two new occurrences for Pernambuco state: Chydorus cf. brevilabris and Macrothrix superaculeata. The species richness of non-planktonic cladocerans (16) was higher than that of planktonic ones (4). The mean density was 186.7 ± 273.6 ind. L-1. Macrothrix elegans, Diaphanosoma spinulosum and Ephemeroporus hybridus were the most abundant. The fluctuation index of the main species showed greater instability during the driest months or greater rainfall, a pattern not observed for the environmental data. However, the pond did not show limnological and cladoceran structure differences between the dry and rainy seasons and between the areas with and without macrophytes. With the exception of temperature and rainfall, the structure and richness of cladocerans was not related to the fluctuation of the other variables. Warmer months had higher densities and richness of cladocerans. On the other hand, months of greatest rainfall had lower richness, especially for the Chydoridae family. Although this Caatinga pond is maintained exclusively by rainwater, the richness of cladocerans is high when compared to other tropical and subtropical ecosystems. These results suggest that rainfall and temperature exert greater control on the dynamics of cladocerans in the Caatinga's temporary shallow ponds, and demonstrate the importance of these ecosystems to biodiversity in the semiarid region.
Abstract in English:To the present 57 species of Hyalella were described for Americas, 15 of them found in Brazil, which is among the most diverse countries for this genus. This work aims to describe a new Hyalella species with benthic habits which is found in a water source on Southeastern Brazil. It is mainly characterized by a wide truncated process formed near the dactylus insertion on gnathopod 2, besides both coxal and sternall gills present on pereonits 2 to 7. This work improves the knowledge on biodiversity about Hyalella species.
Abstract in English:We provide an updated checklist of the snapping shrimps of the genus Alpheus Fabricius, 1798 (Crustacea: Alpheidae) from the Brazilian coast, as well as a key for their identification. The checklist was based on an exhaustive analysis of the literature published up to now, supported by analysis of material of 24 of the 33 species presently recorded from Brazil. Illustrations of the main diagnostic characters are provided to facilitate the identification process, as well as color photographs of 16 species collected by the authors, to facilitate the identification of fresh specimens. For each species, we provide information on the distribution and a list of previous records for the Brazilian coast. Comments on dubious records or taxonomic remarks are provided when appropriate. Finally, the zoogeography of the species is briefly discussed.
Abstract in English:This paper evaluates the role of three species of macrophytes in the population of caridean shrimps in the Salsa river (Northeastern of Brazil). Results revealed that macrophytes have important functions and directly responsible for modulating the spatial distribution of these shrimp species.