Identification and characterization of Perkinsus sp. (Perkinsida: Perkinsidae) in oysters from Manila Bay
Abstract/Summary
Oysters cultured in the Manila Bay, specifically, Cavite City and Naic, Cavite and Obando, Bulacan were surveyed for the occurrence of Perkinsus sp., for three months from June to August 2012. Rays Fluid Thioglycollate Medium (RFTM) was utilized in determining the presence of Perkinsus sp. in oysters. RFTM revealed the presence of Perkinsus sp. hypnospores in oyster tissues. Based from the hypnospores present, infection rate was recorded highest in Obando, Bulacan with 79.4%, followed by Naic, Cavite with 66.1%and Cavite City, Cavite with 62.8% as the lowest. Intensity of infection was also recorded highest in Obando, Bulacan with 18.93 followed by Naic, Cavite with 12.86 and Cavite City, Cavite with 12.56 as the lowest in which no significant differences occurred across sites. However, a decreasing pattern was observed from June to July 2012 and an increase in the month of August 2012 which revealed significant differences across the six collection period specifically, during July 2012 and the first collection in August 2012. Furthermore, histological sections were made to confirm the RFTM for the occurrence of the parasite and the potential damage it caused in the host tissue. Oyster hemocytes were likewise present along with Perkinsus sp. Circular damage in the mantle was observed. It was also noted that the parasite’s trophozoite stage in the histological sections is much smaller than 1μm which is unusual for Perkinsus species. However, it was confirmed by experts that these are Perkinsus sp. which can be possible new species exclusive in the Philippines. Interestingly, mixed infections of Tylocephalum sp. (Leanicephalidea: Tetragonocephalidae) which is a metacestode, Nematopsis sp. (Eugregarinorida:Porosporidae) which is a gregarine, ciliates from the family Orchidophryidae of the order Scuticoliatida, flagellates from the Phylum Sarcomastigophora, a Cryptosporidium-like organism and a Rickettsia-like organism were noted.
