RESUMO
Coral reefs rival rainforest in biodiversity, but are declining in part because of disease. Tissue loss lesions, a manifestation of disease, are present in dominant Pocillopora along the Pacific coast of Mexico. We characterized tissue loss in 7 species of Pocillopora from 9 locations (44 sites) spanning southern to northern Mexico. Corals were identified to species, and tissue loss lesions were photographed and classified as those explainable by predation and those that were unexplained. A focal predation study was done concurrently at 3 locations to confirm origin of explained lesions. Of 1054 cases of tissue loss in 7 species of corals, 84% were associated with predation (fish, snails, or seastar) and the remainder were unexplained. Types of tissue loss were not related to coral density; however there was significant geographic heterogeneity in type of lesion; one site in particular (Cabo Pulmo) had the highest prevalence of predator-induced tissue loss (mainly pufferfish predation). Crown-of-thorns starfish, pufferfish, and snails were the most common predators and preferred P. verrucosa, P. meandrina, and P. capitata, respectively. Of the 9 locations, 4 had unexplained tissue loss with prevalence ranging from 1 to 3% with no species predilection. Unexplained tissue loss was similar to white syndrome (WS) in morphology, indicating additional study is necessary to clarify the cause(s) of the lesions and the potential impacts to dominant corals along the Pacific coast of Mexico.
Assuntos
Antozoários/fisiologia , Peixes/fisiologia , Comportamento Predatório , Caramujos/fisiologia , Estrelas-do-Mar/fisiologia , Animais , Recifes de Corais , México , Oceano PacíficoRESUMO
Coral reefs are threatened by a variety of factors including diseases that have caused significant damage in some regions such as in the Caribbean. At present, no data are available on coral diseases in the Mexican Pacific where Pocillopora spp. is a dominant component of coral communities. Here, we describe gross and microscopic morphology of lesions found in pocilloporids at four sites in the Mexican Pacific. Corals were identified and their lesions photographed and quantified in the field. Tissue samples were collected from healthy and affected colonies for histopathology. We recorded seven species of pocilloporids at the study sites with Isla Isabel being the location with the highest coral diversity (H'=1.27). Lesions were present in 42% of the colonies and included discoloration (32%), predation-induced tissue loss (30%), unexplained tissue loss (3%) and overgrowth by sponges or algae (35%). The most affected species, P. damicornis (50%), was also one of the most common in the region. No species was more prone to a particular lesion, but there was a significant association between location and the presence of lesions. Northern Islas Marietas (61%) and Isla Isabel (41%) had the highest prevalence of lesions, followed by Manzanillo (37%) and Bahías de Huatulco (23%). Histological changes included atrophy of the surface body wall with depletion of zooxanthellae (91%) in corals with discoloration (bleaching). Ablation of tissue from mesoglea (18%) was also observed. Colonies with unexplained tissue loss showed atrophy and thinning of the epidermis (89%), characterized by cuboidal instead of pseudocolumnar cells normally found in healthy pseudocolumnar ciliated epithelium. Bacterial aggregates between the mesoglea and gastrodermis (11%) were very conspicuous in healthy and diseased corals. Lesions produced by fish bites and gastropods were associated with tissue atrophy (40%) and, in some cases, algal overgrowth near the lesion (20%). No infectious agents associated with cell pathology were detected microscopically. Bleaching and overgrowth by algae and sponges, as well as unexplained tissue loss, are common in Pocillopora. These lesions and anatomical changes warrant further study since their incidence is potentially indicative of reef degradation.
Assuntos
Antozoários , Recifes de Corais , Animais , Antozoários/microbiologia , MéxicoRESUMO
After damming the Colorado River the freshwater flow was reduced to 1 of its virgin flow to the Upper Gulf of California (UGC). The ecological effects need to be properly documented. The UGC is the nursery area for Litopenaeus stylirostris, the most profitable fishery in the zone. In order to know the relative abundance of L. stylirostris postlarval stage we conducted a sampled survey every 14 days in 1993, 1994 and 1997, plus an intensive sampling during a complete tide cycle in July 1995 and 1996. We did 10 min trawls each hour during the flood tide. Relative abundance of postlarvae was higher (p < 0.05) in those years when freshwater flow reached the UGC.