Seasonal variations in the intermediate metabolism of Aegla platensis (Crustacea, Aeglidae)

This study investigated the effects of circadian and seasonal fluctuations on the intermediate metabolism of the freshwater crustacean Aegla platensis. Individuals were collected each month, at 6:00 h, 12:00 h and 18:00 h, between August 1999 and June 2002 in the Municipality of Taquara, Rio Grande do Sul, Brazil (29 degrees 30'0.2'S and 50 degrees 46'50'W). Anomuran crabs were separated by sex, and samples of haemolymph, hepatopancreas, abdominal muscle, and gills were collected for quantification of glucose, proteins, lipids, triglycerides, and glycogen. No variations were observed in the analyzed metabolic parameters for the different tissues during the different times of day, either for males or females. However, the storage and use of the energetic substrates analyzed did fluctuate seasonally. These results suggest an increase in energy demand, possibly for the production of gametes during summer, incubation and egg laying during autumn and winter, and parental care during spring and summer, respectively. A similar pattern has been observed for other crustaceans.     

The gonads of Aegla platensis Schmitt (Decapoda, Anomura, Aeglidae): a macroscopic and histological perspective

The aim of this study is to characterize the gonads of Aegla platensis, relating aspects of colour and size of ovaries, testes and vasa deferentia (VD) to histological observations. The ovaries are H‐shaped, extending from behind the stomach and ending at the 1st or 2nd abdominal somite. The male has a pair of testes from which the VD issue and extend over the pereon. For males and females, macroscopic categories of gonad development are defined. Stages of the male gonad are defined as types 1, 2 and 3. Type 1 includes the less developed gonads, and type 3 includes extremely developed testes and completely differentiated VD. The ovaries are classified into four stages according to their colour: I (white), II (yellow), III (orange) and IV (red), beginning with the least developed gonads. The number and size of oogonia and oocytes depend on the stage of the ovary and coincide with the different degrees of development as indicated by ovary colour. In males, the presence or absence of spermatozoa in the testes and VD is determined only for the more developed gonads. Neither spermathecae (female) nor spermatophores (male) were found. The lack of spermatophore in the present species is a rare characteristic among the anomurans.     

Clinal variation in carapace shape in the South American freshwater crab,Aegla uruguayana (Anomura: Aeglidae)

South America has been influenced by different geoclimatic events ever since its separation from Africa. The inland water fauna has evolved in response to the changing landscape. Currently, there are indications of variations in populations, occurring to different degrees that would indicate a clinal pattern in morphology. Among South America's fauna, the freshwater anomuran, Aegla, is an enigmatic group as a result of its endemicity and is composed of only one genus. Of all the species in this family, Aegla uruguayana has the broadest distribution. Its native habitats have been influenced by several marine transgressions during the Miocene–Quaternary Periods; thus, it is likely that their current distribution has been more recent. Its habitat spreads across a number of isolated basins and sub‐basins that display distinct degrees of isolation/connection, making clinal variation patterns in the morphology of this species possible. The present study aimed to evaluate the pattern of carapace shape variation in A. uruguayana and how it relates to the isolation and/or connection of populations from different basins and sub‐basins, allowing the determination of any extant clinal patterns. The specimens studied belong to 25 separate populations, representing all areas in which the species currently exists. A total of 523 crabs were analyzed. We identified 13 landmarks and four semi‐landmarks in the carapace. The aeglids were divided into seven size intervals to avoid an allometry effect. In each size category, shape relationships analyzed by principal component analysis suggest a geographical pattern corresponding to the distribution of the populations studied. An evaluation of covariation between body shape and geographical coordinates reveals a strong pattern and shows that population distribution had a significant effect on species morphology. Additionally, according to covariance analysis, the variation in shape was not associated with the environmental variables studied. We observed a clinal pattern throughout the species distribution, which could be attributed to genetic drift. It is possible that this process is being amplified by the geographical isolation of the basins, differences in environmental characteristics, and low dispersal ability. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113 , 914–930.     

Effect of different starvation and refeeding periods on macromolecules in the haemolymph,digestive parameters,and reproductive state in Aegla platensis (Crustacea,Decapoda, Aeglidae)

In the present study we assessed the effects of different periods of starvation and refeeding on macromolecule levels (glucose, proteins, triglycerides, and glycerol) in the hemolymph as well as circulating levels of cholesterol in Aegla platensis. We also studied possible changes in the distribution of stomach fullness classes (DSFC), mean stomach fullness degree (SFD), and the mean stomach fullness, hepatosomatic, and gonadosomatic indices. Animals were collected in the field, sexed and divided into groups. This was made as follows: lab control (10 days on standard diet); 5, 15, and 30 days starvation; and 5 days refeeding. During the starvation period there were differences in cholesterol, glucose, and proteins in both genders, but we observed no differences in total lipid, triglycerides, or glycerol levels. The SFD was the lowest in the 30-day starvation group in both females and males. Starvation appears to modulate gastric emptying and possibly digestive processes as well as induce preferential utilization of carbohydrates and proteins. This enables survival throughout the study period. We observed maintenance of gonadosomatic index and reduction of hepatosomatic index in females during the study period with a return to baseline after refeeding. Refeeding was insufficient to restore the DSFC, but sufficient to restore glucose and cholesterol levels.     

High genetic differentiation of Aegla longirostri (Crustacea, Decapoda, Anomura) populations in southern Brazil revealed by multi-loci microsatellite analysis

Species with a broad distribution rarely have the same genetic make-up throughout their entire range. In some cases, they may constitute a cryptic complex consisting of a few species, each with a narrow distribution, instead of a single-, widely distributed species. These differences can have profound impacts for biodiversity conservation planning. The genetic differentiation of four populations of Aegla longirostri, a freshwater crab found in two geographically isolated basins in Rio Grande do Sul State, Brazil, was investigated by analyzing pentanucleotide multi-loci microsatellites in a heteroduplex assay. Although no morphological differences were evident, we found significant genetic differentiation among the four populations, based on F(ST) values and clustering analysis. This high level of differentiation may be indicative of cryptic species in these populations. If this hypothesis is correct, then the species occurring in the Ibicuí-Mirim River, at the southern limit of the Atlantic Rain Forest, would be under threat, considering its very restricted distribution.     

Sexual dimorphism in the cephalothorax of freshwater crabs of genus Aegla Leach from Chile (Decapoda,Anomura, Aeglidae): an interspecific approach based on distance variables

Some morphological studies based on the comparisons between two or three species of Aegla indicate that, as an expression of sexual dimorphism, the cephalothorax is longer in males and wider at the posterior end in females. To assess whether this is a general trend, we performed a series of covariational analyses relating the length and posterior width of cephalothorax in 1,242 specimens of both sexes from 17 of the 19 species of Aegla reported from Chile. By using a covariable homologous for all individuals, it was shown that the bias toward females in the posterior cephalothoracic width is greater than the bias toward males in the cephalothoracic length. Additionally, both variables show positive phylogenetic signal, both in each trait individually and their male–female relationship. For the entire Chilean clade of Aegla, both variables showed a narrow covariation pattern influenced by the sex of the individuals. Furthermore, the phylogenetic signal both in each variable individually and the female–male relationships derived from directional phylogenetic comparative analyses suggests that this relationship is inherited by shared common ancestry, restricting their adaptive potential to most probably directions of change. However, within certain limits, this variability has important reproductive and behavioral implications that are directly associated with the fitness of the taxon.     

Larval development ofNeopisosoma neglectum werding, 1986 (Decapoda: Anomura: Porcellanidae) under laboratory conditions

The complete larval development of the porcellanid crabNeopisosoma negluctum Werding, 1986, was studied under laboratory conditions. At 27°C, the megalopa appeared after 9 days. The development consists of a transitory prezoea, two zoeal stages and a megalopa stage. The larvae exhibit telsonal features which places them in thePetrolisthes-group of porcellanid larvae. Larval morphology gives no additional support for the status ofNeopisosoma as an independent genus.     

Global diversity of crabs (Aeglidae: Anomura: Decapoda) in freshwater

The freshwater anomuran crabs of the family Aeglidae are all restricted to southern South America occurring in Chile, Brazil, Bolivia, Uruguay, Paraguay, and Argentina. The family consists of a single genus, Aegla, containing 63 currently described species. There are another 5–10 known yet undescribed species to complement this diversity. The aeglids occur in freshwater lakes, streams, rivers, and in caves with freshwater. The origin of the family appears to be from marine ancestors from the Pacific invading streams in Chile about 75 mya radiating both in Chile and again on the eastern side of the Andes, particularly in Brazil. Of the 63 species, 23 or 36.5% are considered under threat and are in need of conservation action. Guest editors: E. V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment     

Molecular systematics and biogeography of the southern South american freshwater "crabs" Aegla (decapoda: Anomura: Aeglidae) using multiple heuristic tree search approaches

Recently new heuristic genetic algorithms such as Treefinder and MetaGA have been developed to search for optimal trees in a maximum likelihood (ML) framework. In this study we combined these methods with other standard heuristic approaches such as ML and maximum parsimony hill-climbing searches and Bayesian inference coupled with Markov chain Monte Carlo techniques under homogeneous and mixed models of evolution to conduct an extensive phylogenetic analysis of the most abundant and widely distributed southern South American freshwater"crab,"the Aegla(Anomura: Aeglidae). A total of 167 samples representing 64 Aegla species and subspecies were sequenced for one nuclear (28S rDNA) and four mitochondrial (12S and 16S rDNA, COI, and COII) genes (5352 bp total). Additionally, six other anomuran species from the genera Munida,Pachycheles, and Uroptychus(Galatheoidea), Lithodes(Paguroidea), and Lomis(Lomisoidea) and the nuclear 18S rDNA gene (1964 bp) were included in preliminary analyses for rooting the Aegla tree. Nonsignificantly different phylogenetic hypotheses resulted from all the different heuristic methods used here, although the best scored topologies found under the ML hill-climbing, Bayesian, and MetaGA approaches showed considerably better likelihood scores (Delta> 54) than those found under the MP and Treefinder approaches. Our trees provided strong support for most of the recognized Aegla species except for A. cholchol,A. jarai,A. parana,A. marginata, A. platensis, and A. franciscana, which may actually represent multiple species. Geographically, the Aegla group was divided into a basal western clade (21 species and subspecies) composed of two subclades with overlapping distributions, and a more recent central-eastern clade (43 species) composed of three subclades with fairly well-recognized distributions. This result supports the Pacific-Origin Hypothesis postulated for the group; alternative hypotheses of Atlantic or multiple origins were significantly rejected by our analyses. Finally, we combined our phylogenetic results with previous hypotheses of South American paleodrainages since the Jurassic to propose a biogeographical framework of the Aegla radiation.     

Size at the onset of sexual maturity in the anomuran crab, Aegla uruguayana (Aeglidae)

The size at maturity was studied in the crab Aegla uruguayana from the Areco River (31°14′ S, 59°28′ W), Argentina. Size at sexual maturity was determined according to three criteria: morphometric (change in the relative growth of reproductive characters), histological (first maturation of gonads) and functional (capability to mate and carry eggs). Regarding females, morphometric maturity occurred at a carapace length (CL) of 11.50 mm, considering abdomen width as a reproductive character. Gonad maturity of females could be observed at a minimum size ranging from 15 to 17 mm CL. The smallest ovigerous female observed in the field was 15.60 mm CL, although a relevant population incidence of ovigerous females (86.6%) has just been observed at values higher than 17 mm CL. As for males, the relative growth of the left chela length changed at a value of 15.40 mm CL, while morphological changes in sexual tube occurred between CL of 14 and 16 mm. Testicular maturation occurred at a CL ranging from 17 to 19 mm. The smallest size of males having spermatozoids in their vasa deferentia was 18.70 mm CL. The results obtained indicated that, in both sexes, functional maturity occurred after morphometric maturity and at a size similar to that of gonad maturity. Comparing sexes, females acquired sexual maturity (morphometric, gonad and functional maturity) at sizes statistically smaller than those of males.     

Survivorship and fecundity of Argulus bengalensis (Crustacea; Branchiura) under laboratory conditions

The Life table features and the fecundity schedule of the fish louse Argulus bengalensis (Branchiura: Argulidae) were estimated under laboratory conditions using Cirrhinus mrigala as the model host. The cohort-based Life table revealed that survival of A. bengalensis declines as a function of age. Life expectancy was observed to be 34?days for a newly emerged adult. The mean number of eggs produced per egg strip was 86 (±8.89 S.E.). The sex ratio 2:1 was biased towards males. The net reproductive rate (R₀) varied between 50 and 487 while the cohort generation time (T_c) ranged between 24 and 26?days. The intrinsic rate of increase (r) was 0.14–0.23, while the finite rate of increase (λ) remained between 1.16 and 1.28. The Life table features and the fecundity schedule of A. bengalensis are comparable with congenerics of temperate regions. Early reproduction (between 21 and 23?days) and an extended postreproductive phase (47?days) of females are characteristic of A. bengalensis and a reflection for survival under uncertain conditions and a parasitic mode of life.     

Larval development of Hexapanopeus caribbaeus (Stimpson, 1871) (Crustacea, Decapoda, Xanthoidea, Panopeidae) reared under laboratory conditions

The genus Hexapanopeus Rathbun, 1898 contains eight species,of which three are found in the Brazilian coast. The larvaldevelopment of two of these species has already been studiedin the laboratory. This article describes in detail the morphologyof the complete larval stages of Hexapanopeus caribbaeus rearedunder laboratory conditions, and the morphology is comparedwith that of the larvae of the other species of the same genus.     

Feeding and masticatory structures of selected Anomura (Crustacea)

Seven species representing the three superfamilies of the Anomura were studied regarding food, feeding mechanisms, and masticating ossicles of the gastric mill in order to determine whether the structure of the gastric mill was determined by diet or phylogeny. The hippid representative and both porcellanids examined feed on suspended detritus and plankton while the pagurids feed on a variety of substances ranging from detritus to motile prey. The morphology of the mouthparts and chela are related to feeding activity, especially the hippid and porcellanids, but general features of feeding requiring specific anatomical characters were not found in the paguridae. Feeding similarity was measured using the overlap measure of Horn.Among the species the masticating ossicles of the gastric mill differ in those species feeding primarily on detritus; it is finely toothed or setose with the masticating portions of the ossicles blunt. The gastric mill of the species feeding on macromaterial is strongly toothed and sparcely setose, with the masticating portions sharp and cutting. The structure of the gastric mill was found to be influenced by both diet and phylogeny, but the effect of diet appears to be more important.     

The larval development of Petrolisthes politus (Gray, 1831) (Crustacea: Decapoda: Porcellanidae) under laboratory conditions

The complete larval development of the shallow-water Caribbean porcellanid crab, Petrolisthes politus (Gray, 1831), is described and illustrated from specimens reared in the laboratory. Petrolisthes politus hatches as a prezoea, which persist for less than 90 minutes, and then molts through two subsequent zoeal stages, which are completed in 6 to 7 and 14 to 16 days, respectively, before the megalopal stage is reached. From a total of about 2000 zoeae that were cultured, only two reached the megalopal stage. The two megalopae survived for up to 5 days but did not molt to the first crab stage. The zoeae of P. politus are compared with those of Petrolisthes rufescens (Heller, 1861), Petrolisthes lamarckii (Leach, 1820), Petrolisthes carinipes (Heller, 1861), Petrolisthes coccineus (Owen 1839) and Petrolisthes pubescens (Stimpson, 1858), which were hitherto the only species having bifid lateral spines on the telson of the first zoeal stage.     

Larval stages of Brachynotus atlanticus Forest, 1957 (Crustacea: Decapoda: Grapsidae) reared under laboratory conditions

The complete larval development of the Eastern Atlantic grapsidcrab, Brachynotus atlanticus, was obtained in the laboratory.Five zoeal stages, the megalopa and the first crab stage aredescribed and illustrated. Under laboratory conditions at 23°Cthe first crab appeared on the 25th day. This is the first speciesof the genus for which the complete larval development is known.Larval features are compared with those of other members ofthe subfamily Varuninae.