Histopathology of the mangrove land crab Ucides cordatus (Ocypodidae) affected by lethargic crab disease

Abstract

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.

Research Note Single primer-based DNA amplification as a suitable and low-cost tool for assessing genetic diversity in mangrove crabs

“…The mangrove crab Ucides cordatus, which occurs along the subtropical and tropical Atlantic coast of America, is a threatened species. It is possible that heavy exploitation, habitat destruction and occurring diseases are directly affecting the genetic diversity of crab populations (Alves et al, 2005;Boeger et al, 2007). These events can result in the collapse of this important fishery resource and cause ecological and social impacts on the ecosystem and fishing communities, respectively.…”

Disseminated Phaeohyphomycosis in Weedy Seadragons (Phyllopteryx Taeniolatus) and Leafy Seadragons (Phycodurus Eques) Caused by Species of Exophiala, Including a Novel Species

“…Melanized fungi have been associated with disease in humans, 6,57 mammals, 11,18,28,61 birds, 32,56 amphibians, 12 reptiles, 30 fish, 19,60 and invertebrates. 8,62 Of special interest are members of the order Chaetothyriales, such as Exophiala and Cladophialophora, which are ecologically different and seem to be associated with assimilation of alkylbenzenes, compounds that are also present in vertebrate bodies. 50 These fungi are regularly encountered as causative agents of mycoses of medical and veterinary importance; only Onygenales, the order containing dermatophytes and dimorphic pathogens, has a comparable number of clinically relevant fungi.…”

Growth and mortality of the exploited mangrove crab Ucides cordatus (Ucididae) in N-Brazil

“…This large species (carapace width, CW: males > 90 mm; females > 70 mm) is the main leaf litter feeder in Brazilian mangroves and plays an important ecological role by processing up to 81% of the litter production in some areas (Nordhaus et al 2006). Artisanal fishermen have been harvesting U. cordatus for decades along the Brazilian coast, and in recent years several crab populations have experienced strong declines due to deforestation, a fungal disease and overfishing (Nordi, 1994;Botelho et al, 2000;Alves et al, 2005;Boeger et al, 2007). The fishery targets mostly large males and in some areas yields are still six to eight tons per km² per yr (e.g.…”