Patógenos no sururu Mytella falcata (Orbigny, 1846) do estuário do rio Jaguaribe-CE, com especial enfoque para o protozoário de declaração obrigatória Perkinsus

Abstract

The exploitation of bivalve Mytella falcata in the estuaries of Ceará by the local population has an important socio-economic aspect. This species can be affected by various pathogens which can cause massive mortality. The presence of protozoa from the genus Perkinsus is worrisome because they are responsible for severe losses in bivalve populations. The aim of this study was to investigate the occurrence of pathogens in M falcata from Jaguaribe River estuary, Ceará, with emphasis on protozoan Perkisnus. The monthly collections were conducted during March-July 2010, totaling 600 animals (150/coleta). For the pathological diagnosis the techniques used were macroscopic examination, tissue culture in liquid thioglycolate (RFTM) and histology. The animals were weighed, measured and opened, and rectum and gill tissues were incubated in RFTM to verify the presence of Perkinsus. For histology a cross-section was made, containing mantle, gonads, gills and digestive gland. After histological procedures, sections of 5 gm were stained with hematoxylin and eosin. The diagnosis of the pathogens was achieved by optical microscopy. Macroscopic analysis showed no fouling organisms and changes in the tissues of animals. The results of RFTM presented here detected for the first time the presence of hypnospores of Perkinsus sp. infecting mussels M. falcata from Jaguaribe River estuary. The higher prevalence of Perkinsus sp. observed was 36% (54/150) in July. Histological analysis confirmed the presence of trophozoites of Perkinsus sp. infecting the gill tissue, mantle and around the digestive gland with prevalence rates of up to 40% (12/30). In addition to that, rickettsia-like bacteria were observed in gill and digestive gland, in low prevalence, and meta7oan from the genus Tylocephalum infesting many of the sampled animals. So far none of the pathogens detected in Mytella falcata from Jaguaribe River estuary seems to represent a health risk for that bivalve, since they were detected in low intensity. However, considering that the protozoan Perkisnus sp. represents a serious threat to shellfish populations, the local banks should be continuously monitored.