OBSERVATIONS ON ERGASILUS CHELANGULATUS (COPEPODA: ERGASILIDAE) A GILL PARASITE OF TILAPIA ZILLI FROM MANZALLA LAKE
Ramadan Anwar Mohammed Ramadan
Fish Diseases Department, Central Laboratory For Aquaculture Research, Agricultural Research Center, Ministry Of Agriculture, Egypt.
Received 9/ 11/ 2011 Accepted 5/ 12/ 2011
Abstract
Ergasilus chelangulatus infested gill filaments of Tilapia zilli from Manzalla Lake. Only females were detected and the males are non parasitic. E.chelangulatus has a serrate seta on exopod one and a two-segmented first endopod. The body is elongate and protruded anteriorly. The antennae are elongate and have prominent sensilla on segments two and three. E. chelangulatus can be distinguished by the fourth antennal segment (claw) which is bent at nearly a right angle. Monthly study between June 2008 – May 2009, and a total of 463 fish were collected. The distribution of parasitic copepods in relation with the length, sex of fish was recorded. Mean intensity of 6.2/fish and a prevalence incidence of 34.2%. The prevalence and mean intensity were seasonal with higher levels in summer with 51.2% and 7 respectively. No significant differences were noticed in the infestation of male and female fish. A slight increase in the infestation prevalence was recorded as the size of fish increased. Gills showed severe pathological changes, where clubbing and fusing of the gill filaments were observed. Deep indentations were recorded in the tips of the damaged filaments which had broken off. Fish were infected at a similar rate, having 1 to 20 copepods attached to the end of the clubbed filaments or the proliferated epithelium . In histological sections the head part of the parasite was found in a deep cavity of the proliferated epithelium, piercing its antennae deep into the tissues. Only the end of the filaments showed changes. The proliferated epithelium was infiltrated by eosinophilic granular cells. In the central and basal parts of the hemibranchia the original structure of the filaments was preserved with intact secondary lamellae.
Key words:
Oreochromis zilli parasite; copepod parasite; freshwater fish; pathological changes; Abbassa, Egypt.
