Lethargic crab disease (LCD) has caused extensive epizootic mortality of the mangrove land crab Ucides cordatus (Linnaeus 1763) (Brachyura: Ocypodidae) along the Brazilian coast. Direct culture of tissue samples from sick crabs and subsequent isolation and purification identified the causative agent as an Exophiala species of fungus. The histopathology of crabs with variable signs of LCD indicates that the most affected tissues are the epidermis, connective tissue, heart, hepatopancreas, nervous system, and gills. Gonads, somatic muscles, and digestive system are less affected by the fungus. The observed pathology is compatible with the clinical signs of LCD. Necrosis, tissue degeneration, and congestion of hemal sinuses and vessels are present in heavily infected organs. Nerve fibers may be compressed by accumulations of yeast-like cells. In heavy infections the tissue of gill lamellae is destroyed with subsequent dilation or compression. Cellular immune responses include hemocytic infiltration, agglutination and encapsulation, and phagocytosis. Phagocytosis of yeast-like cells is abundant in the connective tissue associated with the exoskeleton. These results indicate that LCD is the result of a systemic phaeohyphomycosis caused by a species of Exophiala. The present study also suggests that dispersal of the fungus within the crab occurs through the hemal system.

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The crab Ucides cordatus (Decapoda: Ocypodidae) is a species of considerable economic and ecological importance in mangrove areas of the Western Atlantic coast. However, habitat loss, overfishing, and a new infectious disease are causing substantial reductions in local stocks of this species, leading to a pressing need to design efficient management strategies. A crucial step in this design in an understanding of how the genetic variability of U. cordatus is distributed among estuaries throughout its range. In this study we assess the degree of spatial structure in the pattern of genetic variation of U. cordatus over local (estuaries located within 100 km from each other) and geographical scales (estuaries located farther than 2700 km from each other). Ninety individuals were collected from nine estuaries and analyzed using PCR-RFLP and RAPD techniques. The percentage of polymorphic bands within populations ranged from 15% to 46% for RFLP markers and from 40% to 70% for RAPD markers. Our results failed to demonstrate significant geographical structure in the pattern of genetic variation, indicating that populations of U. cordatus are capable of extensive gene flow among estuaries. The implications of these results for the management of U. cordatus populations are discussed.

Species-specific disturbance calls of five commercially-important characiform species are described, the Curimatidae commonly called branquinhas: Potamorhina latior, Potamorhina altamazonica and Psectrogaster amazonica; Prochilodontidae: jaraquí Semaprochilodus insignis and curimatã Prochilodus nigricans. All species have a two-chambered swimbladder and the sonic mechanism, present exclusively in males, utilises hypertrophied red muscles between ribs that adhere to the anterior chamber. The number of muscles is unusually plastic across species and varies from 1 to 4 pairs suggesting considerable evolution in an otherwise conservative system. Advertisement calls are produced in river confluences in the Madeira Basin during the high-water mating season (January-February). Disturbance calls and sampling allowed recognition of underwater advertisement choruses from P. latior, S. insignis and P. nigricans. The advertisement calls of the first two species have largely similar characteristics and they mate in partially overlapping areas in the Guaporé River. However, P. latior sounds have a lower dominant frequency and it prefers to call from river confluences whereas S. insignis shoals occur mostly in the main river channel adjacent to the confluence. These results help identify and differentiate underwater sounds and evaluate breeding areas during the courtship of commercially important characids likely to be affected by two hydroelectric dams. K E Y W O R D S

We evaluated fish diversity in three tributaries of the São Francisco River, one of the largest watercourses in Brazil. The study site is in the sub-basin of the Carinhanha River [Carinhanha, Cocos (I and II) and Itaguari Rivers], located in the South region of the Bahia state. These rivers are crossed by bridges of the federal highway BR-135. After sampling, upstream and downstream from each bridge, during drought and rain seasons, 3,520 specimens of fish (57 species, 21 families) were captured. The species with highest occurrence were Astyanax cf. taeniatus, Serrapinnus heterodon, Astyanax bimaculatus and Astyanax cf. rivularis. During drought season, the number of specimens captured was higher, leading to an increase of species dominance. In the rainy season, species diversity was higher with a greater distribution of individuals among species. The data indicate the maintenance of the fish faunal structure despite anthropogenic activities on the studied areas.

Soft-shell crab is considered a gastronomic delicacy, reaching high values in the international market. Under normal conditions, the process of hardening of the crab's exoskeleton after moulting takes approximately two days to complete; however, the commercial consistency of soft-shell crab is lost in just 3 hours. The goal of this research was to evaluate the effects of chemical changes of water on the duration of postmoult, specifically at the stage in which they can be marketed as soft-shelled crab. In this research, Callinectes ornatus (n=241) underwent two experiments: One group was maintained in tanks with partial daily water renewal (Experiment 1), and other in tanks without water renewal (Experiment 2). In the experiment 1, the chemical characteristics of the water remained unchanged over time (p > 0.05), and the median time to hardening of the exoskeleton after moulting was 3 hours.

14Soft-shell crab is considered a gastronomic delicacy, reaching high values in the 15 international market. The process of hardening of the crab's exoskeleton after 16 moulting takes approximately two days to complete; however, the duration for which 17 the shell remains at the consistency of high commercial value is only 3 hours on 18 average. After this period, the shell assumes a consistency classified as "paper", 19 later becoming "hard" again. The goal of this work was to evaluate the use of the 20 crabs themselves to alter the chemical characteristics of the water and thereby 21 increase the amount of time during which they can be marketed as "soft-shell crab". 22In this work, 241 individuals of Callinectes ornatus were used in two experiments. In 23 the first experiment, the animals were maintained in a collective system with filtration 24 and partial daily water renewal. In the second experiment, the crabs were maintained 25 in a collective system with filtration but no water renewal. In Experiment 1, the 26 chemical characteristics of the water remained unchanged over time (p > 0.05), and 27 the median time to hardening of the exoskeleton to the paper consistency after 28 moulting was 3 hours. Over the course of Experiment 2, there was a significant 29 reduction (p < 0.05) in pH and significant increases in the ammonia and nitrite 30 concentrations. When moulting occurred in water with a pH below 7.3 and total 31 ammonia concentrations above 6.0 mg/L, the crabs' shells did not harden, and it was 32 possible to keep them soft for up to 5 days. 33