Signaling Events During Cyclic Guanosine Monophosphate-Regulated Pigment Aggregation in Freshwater Shrimp Chromatophores

Crustacean color change results partly from granule aggregation induced by red pigment concentrating hormone (RPCH). In shrimp chromatophores, both the cyclic GMP (3', 5'-guanosine monophosphate) and Ca2+ cascades mediate pigment aggregation. However, the signaling elements upstream and downstream from cGMP synthesis by GC-S (cytosolic guanylyl cyclase) remain obscure. We investigate post-RPCH binding events in perfused red ovarian chromatophores to disclose the steps modulating cGMP concentration, which regulates granule translocation. The inhibition of calcium/calmodulin complex (Ca2+/CaM) by N-(6-aminohexyl)-5-chloro-1-naphthalenesulphonamide (W7) induces spontaneous aggregation but inhibits RPCH-triggered aggregation, suggesting a role in pigment aggregation and dispersion. Nitric oxide synthase inhibition by N omega-nitro-L-arginine methyl ester hydrochloride (L-NAME) strongly diminishes RPCH-induced aggregation; protein kinase G inhibition (by rp-cGMPs-triethylamine) reduces RPCH-triggered aggregation and provokes spontaneous dispersion, disclosing NO/PKG participation in aggregation signaling. Myosin light chain phosphatase inhibition (by cantharidin) accelerates RPCH-triggered aggregation, whereas Rho-associated protein kinase inhibition (by Y-27632, H-11522) reduces RPCH-induced aggregation and accelerates dispersion. MLCP (myosin light chain kinase) and ROCK (Rho-associated protein kinase) may antagonistically regulate myosin light chain (MLC) dephosphorylation/phosphorylation during pigment dispersion/aggregation. We propose the following general hypothesis for the cGMP/Ca2+ cascades that regulate pigment aggregation in crustacean chromatophores: RPCH binding increases Ca2+ (int), activating the Ca2+/CaM complex, releasing NOS-produced nitric oxide, and causing GC-S to synthesize cGMP that activates PKG, which phosphorylates an MLC activation site. Myosin motor activity is initiated by phosphorylation of an MLC regulatory site by ROCK activity and terminated by MLCP-mediated dephosphorylation. Qualitative comparison reveals that this signaling pathway is conserved in vertebrate and invertebrate chromatophores alike.

It is a matter of taste: chemical signals mediate nuptial gift acceptance in a neotropical spider

Nuptial gift offering is a courtship trait found among several insect orders and some spider families. Recent studies indicate that this gift-giving behavior in spiders represents the male mating effort acting on female receptivity through a mechanism of foraging motivation. However, little attention has been given to the sensory channels that are influencing female acceptance. To understand the role of these sensory channels in female perception of a nuptial gift, we focused on the nuptial gift of the neotropical spider Paratrechalea ornata (Araneae, Trechaleidae). The nuptial gift of this species is composed of a prey item wrapped in silk, and previous works suggest that visual and/or chemical cues may be involved in inducing female grasping behavior. We isolated sensory channels using mimetic nuptial gifts (artificial items) or by manipulating real nuptial gifts. Isolated visual signals were not responsible for female acceptance, whereas chemical signals found within the nuptial gift silk layer induced female acceptance. Our findings clearly indicate that a chemical signal located in the silk of the nuptial gift is the main attractant channel, and we formulated 2 hypotheses to explain the mechanisms of action in the female sensory system. We also discuss the consequences of such signaling over female acceptance.

Maternal Care in the Soft Tick Antricola marginatus

Among spiders, scorpions, and whip spiders, a common type of maternal care consists of females carrying newly hatched offspring on their body for a few days until they are able to live independently. While this maternal care has been suggested to occur in different argasid tick species, it has been recorded only once, for Antricola marginatus in Cuba; however, this earlier record only superficially mentioned the occurrence of this behavior, with no further details. Here we report the occurrence of maternal care in the argasid tick A. marginatus under natural conditions in a cave at Yucatan. Mexico, where 8 A. marginatus females, while walking on bat guano, had their body entirely covered by a mean number of 305 +/- 112 conspecific unfed larvae (range: 105-466). Larvae covered the entire idiosoma of the female tick, where they were motionless or displayed just slight movement. This result substantially expands the number of unique characters that have been found only in Antricola spp, ticks, when compared to the other tick genera. Our findings also indicate that maternal care evolved independently in different taxa of Arachnida, since it has been reported for species of Araneae, Scorpiones, and Amblypygi, and here for an Acari species.

Alien shrimps in evidence: new records of the genus Athanas Leach, 1814 on the coast of So Paulo, southern Brazil (Caridea: Alpheidae)

The occurrence of two alien alpheid shrimps of the genus Athanas Leach, 1814 [in Leach 1813-1814], the Indo-West Pacific A. dimorphus Ortmann, 1894 and the Eastern Atlantic A. nitescens (Leach, 1813 [in Leach 1813-1814]), on the coast of the state of So Paulo, Brazil, is reported. The presence of A. dimorphus extends the range of this species in the western Atlantic farther to the south in Brazil, whereas A. nitescens is reported for the first time in the western Atlantic, representing the second alien alpheid species on this side of the Atlantic and the twenty-first decapod crustacean introduced in Brazil. We provide morphological accounts of the material examined and illustrate the most important diagnostic characters of both species. An overview of the possible mechanisms of their introduction on the coast of So Paulo is also provided.

Is shell partitioning between the hermit crabs Pagurus brevidactylus and Pagurus criniticornis explained by interference and/or exploitation competition?

The effect of crab behaviour on shell-use dynamics was analysed, comparing both interference and exploitation behaviours between the hermit crabs Pagurus criniticornis and Pagurus brevidactylus. Although these species exhibited microhabitat separation, with P. criniticornis dominating (100%) in sandy substrates and P. brevidactylus (80%) on rocky shores, they overlapped in the rocky shore/sand interface (P. criniticornis, 53%; P. brevidactylus, 43%). Pagurus criniticornis occupied shells of Cerithium atratum in higher frequencies (84%) than P. brevidactylus (37%), which was hypothesized to be a consequence of competitive interactions combined with their ability to acquire and/or retain this resource. The species P. criniticornis was attracted in larger numbers to simulated gastropod predation events than was P. brevidactylus, which, on the few occasions that it moved before P. criniticornis, tended to be attracted more rapidly. Interspecific shell exchanges between these species were few, suggesting the absence of dominance relationships. The shell-use pattern in this species pair is thus defined by exploitation competition, which is presumed to be intensified in areas of microsympatry. These results differ from other studies, which found that interference competition through interspecific exchanges shapes shell use, indicating that shell partitioning in hermit crabs is dependent on the behaviour of the species involved in the contests.

Hermit crabs as bioindicators of recent tributyltin (TBT) contamination

Evaluation of the assimilation pathway and depuration time of a given pollutant by aquatic species is important to understand the dynamics of this substance in the biota, and to search for potential ecological indicators. In the present study, the uptake pathway and depuration time and rate of the pollutant tributyltin (TBT) were investigated in the omnivorous hermit crab (Clibanarius vittatus). The assimilation and uptake pathway were investigated using hermit crabs collected in an area free of TBT. The crabs were held in the laboratory for 45 days, under one of four treatments: procedural control (PC) - water and food without TBT; T1 - water with and food without TBT; 12 - water without and food with Tiff; and 13 water and food with TBT. To determine the depuration time, the crabs were collected in a contaminated area, maintained in the laboratory with clean water, and removed every 15 days for 120 days. The concentrations of TBT and DBT (dibutyltin) were determined by chromatographic analysis. The TBT was taken up by the crabs mainly via food, and the presence of DBT in crab tissues was hypothesized to result from internal TBT degradation. TBT (as well as DBT) was depurated rapidly by C. vittatus. After approximately 30 days, the initial concentration of 111 +/- 36 ng Sn g(-1) w. w. decreased to 3 +/- 3 ng Sn g(-1) w. w., and after 75 days the TBT concentration was below the detection limit. The same pattern was recorded for DBT, which showed a higher deputation rate than TBT. The rapid TBT and DBT deputation is useful information, since C. vittatus and possibly other hermit crabs may be used as indicators of recent or recycled environmental contamination.

Composition and Seasonal Variation of Brachyura and Anomura (Crustacea, Decapoda) Associated with Brown Mussel Farms at Praia da Cocanha, Brazil

The composition and seasonal variation of brachyuran and anomuran species associated with mussel farms were evaluated at Praia da Cocanha, Sao Paulo between May 2007 and February 2008. Nine mussel ropes were sampled at random in each quarter, and 1,208 organisms were identified, comprising five families and 28 species. The most numerous species was the porcellanid Pachycheles laevidactylus (18.5%), followed by the xanthids Acantholobulus schmitti (16.6%), Hexapanopeus paulensis (11.3%), Panopeus americanus (10.2%), and Menippe nodifrons (8.4%). The exotic crab Charybdis hellerii was recorded throughout the study period. The ecological descriptors, except Pielou evenness index, varied significantly over the time. The highest abundance and diversity of the species were recorded during November and February. This pattern was reversed for Berger-Parker dominance, with the lowest values recorded in February. The development of epifauna was correlated with the different stages of the mussel farms, since the mean size of mussels and consequently the abundance of epibiotic organisms and the structural complexity on the mussel ropes increased from May (seeding) until February (harvest). Despite this, the temporal population variations in recruitment patterns of the different epibionts should not be overlooked. The results indicated that the mussel farms provided favorable conditions for the development of these crustacean groups, which could be used in environmental monitoring programs and / or be exploited for the aquarium trade.

Cross-taxon congruence of alpha and beta diversity among five leaf litter arthropod groups in Colombia

In this study alpha and beta diversity patterns of five leaf litter arthropod groups (ants, predatory ants, oribatid mites, spiders and other arachnids) were described and compared in 39 sampling patches of a transformed landscape in southwestern Colombia, that represented five vegetation types: secondary forest, riparian forest, giant bamboo forest, pasture and sugarcane crop. It was also assessed whether some taxa could be used as diversity surrogates. A total of 6,765 individuals grouped in 290 morphospecies were collected. Species richness in all groups was lower in highly transformed vegetation types (pasture, sugarcane crop) than in native ones (forests). In contrast, there were no clear tendencies of beta diversity among vegetation types. Considering sampling patches, 0.1-42% of the variation in alpha diversity of one taxonomic group could be explained from the alpha diversity of another, and 0.2-33% of the variation of beta diversity of a given taxon was explained by that in other groups. Contrary to recent findings, we concluded that patterns of alpha diversity are more congruent than patterns of beta diversity. This fact could be attributed to a sampling effect that promotes congruence in alpha diversity and to a lack of a clear regional ecological gradient that could promote congruent patterns of beta diversity. We did not find evidence for an ideal diversity surrogate although diversity patterns of predatory ants had the greatest congruencies. These results support earlier multi-taxon evaluations in that conservation planning should not be based on only one leaf litter arthropod group.

Behavioral analysis of the interaction between the spitting spider Scytodes globula (Araneae: Scytodidae) and the harvestman Discocyrtus invalidus (Opiliones: Gonyleptidae)

Spitting spiders (Scytodidae) have a distinct predatory strategy in which they eject a sticky secretion from their cheliceral fangs to immobilize prey. This behavior could potentially allow the spider not only to avoid defensive secretions but also to bite specific vulnerable spots of a potential prey such as a harvestman. We used an ethogram, a fluxogram and an experiment to analyze the interaction between the harvestman Discocyrtus invalidus Piza 1938 (Arachnida: Opiliones) and the syntopic spider Scytodes globula (Nicolet 1849) (Arachnida: Araneae). These spiders, while readily taking crickets as prey, seldom spat at and never bit the harvestmen, which apparently did not exude repugnatorial secretions. We therefore tested, by clogging the glands and using appropriate controls, whether non-visible amounts of secretions could cause the rejection, but the harvestmen were still refused. This is the first detailed and quantified description of an interaction between a spitting spider and a harvestman. The general conclusions are that S. globula avoids preying on D. invalidus, S. globula behaves differently when attacking harvestmen and crickets and the scent gland secretions of D. invalidus do not play a direct role in this predator-prey interaction.

Tributyltin in crustacean tissues: analytical performance and validation of method

The hermit crab Clibanarius vittatus is a typical organism from intertidal regions being considered as a good bioindicator of tributyltin presence at these environments. Thus this study presents the analytical performance and validation method for TBT quantification in tissues of C. vittatus by gas chromatography with pulsed flame photometric detector (GC-PFPD) after extraction with an apolar solvent (toluene) and Grignard derivatization. The limits of detection of the method (LOD) were 2.0 and 2.8 ng g-1 for TBT and DBT (dibutyltin), respectively, and its limits of quantification (LOQ) were 6.6 and 8.9 ng g-1 for TBT and DBT, respectively. The method was applied to samples from Santos Estuary, São Paulo State, Brazil. TBT and DBT concentrations ranged from 26.7 to 175.0 ng g-1 and from 46.2 to 156.0 ng g-1, respectively. These concentrations are worrisome since toxic effects (such as endocrine disruption) have been reported for other organisms even under lower levels of registred at this study.

Composition and seasonal variation of brachyura and anomura (Crustacea, Decapoda) associated with brown mussel farms at Praia da Cocanha, Brazil

The composition and seasonal variation of brachyuran and anomuran species associated with mussel farms were evaluated at Praia da Cocanha, São Paulo between May 2007 and February 2008. Nine mussel ropes were sampled at random in each quarter, and 1,208 organisms were identified, comprising five families and 28 species. The most numerous species was the porcellanid Pachycheles laevidactylus (18.5%), followed by the xanthids Acantholobulus schmitti (16.6%), Hexapanopeus paulensis (11.3%), Panopeus americanus (10.2%), and Menippe nodifrons (8.4%). The exotic crab Charybdis hellerii was recorded throughout the study period. The ecological descriptors, except Pielou evenness index, varied significantly over the time. The highest abundance and diversity of the species were recorded during November and February. This pattern was reversed for Berger-Parker dominance, with the lowest values recorded in February. The development of epifauna was correlated with the different stages of the mussel farms, since the mean size of mussels and consequently the abundance of epibiotic organisms and the structural complexity on the mussel ropes increased from May (seeding) until February (harvest). Despite this, the temporal population variations in recruitment patterns of the different epibionts should not be overlooked. The results indicated that the mussel farms provided favorable conditions for the development of these crustacean groups, which could be used in environmental monitoring programs and / or be exploited for the aquarium trade.

Brazilian sandy beach macrofauna production: a review

The state of the art of the studies on the production of Brazilian sandy beach macrofauna was analyzed on the basis of the data available in the literature. For this purpose, the representativeness of the production dataset was examined by latitudinal distribution, degree of exposure and morphodynamic state of beaches, taxonomic groups, and methods employed. A descriptive analysis was, further, made to investigate the trends in production of the more representative taxonomic groups and species of sandy beach macrofauna. A total of 69 macrofauna annual production estimates were obtained for 38 populations from 25 studies carried out between 22º56'S and 32º20'S. Production estimates were restricted to populations on beaches located on the southern and southeastern Brazilian coast. Most of the populations in the dataset inhabit exposed dissipative sandy beaches and are mainly represented by mollusks and crustaceans, with a smaller number of polychaetes. The trends in production among taxonomic groups follow a similar pattern to that observed on beaches throughout the world, with high values for bivalves and decapods. The high turnover rate (P/B ratio) of the latter was due to the presence of several populations of the mole crab Emerita brasiliensis, which can attain high values of productivity, in the dataset. Most of the studies focus on the comparison of production and, especially, of P/B ratio according to life history traits in populations of the same species/taxonomic group. Despite the importance of life history-production studies, other approaches, such as the effect of man-induce disturbances on the macrofauna, should be undertaken in these threatened environments.

Proteomic characterisation of toxins isolated from nematocysts of the South Atlantic jellyfish Olindias sambaquiensis

Surprisingly little is known of the toxic arsenal of cnidarian nematocysts compared to other venomous animals. Here we investigate the toxins of nematocysts isolated from the jellyfish Olindias sambaquiensis. A total of 29 unique ms/ms events were annotated as potential toxins homologous to the toxic proteins from diverse animal phyla, including conesnails, snakes, spiders, scorpions, wasp, bee, parasitic worm and other Cnidaria. Biological activities of these potential toxins include cytolysins, neurotoxins, phospholipases and toxic peptidases. The presence of several toxic enzymes is intriguing, such as sphingomyelin phosphodiesterase B (SMase B) that has only been described in certain spider venoms, and a prepro-haystatin P-IIId snake venom metalloproteinase (SVMP) that activates coagulation factor X, which is very rare even in snake venoms. Our annotation reveals sequence orthologs to many representatives of the most important superfamilies of peptide venoms suggesting that their origins in higher organisms arise from deep eumetazoan innovations. Accordingly, cnidarian venoms may possess unique biological properties that might generate new leads in the discovery of novel pharmacologically active drugs.