Ergasilus zacconis

From Fish
Ergasilus hanging the gill filament.
Female adult of E. zacconis

Ergasilus zacconis are a copepod parasite of the gills of many fish including Ayu (Plecoglossus altivelis) and freshwater minnow (Zacco platypus)[1].

Life cycle

Ergasilus zacconis is an ectoparasitic crustacean. It is composed of cephalosome, metasome, genital somite, two abdominal somites, anal somite and caudal ramus[2]. Only females (0.7-1.7 mm) are visually observed. A nauplius larva, which is hatched from eggs, becomes a copepodite larva, which attaches to host’s gill filament by a pair of craw-shaped antennae and feeds on the proliferated gill tissues. This parasite, which had been originally named as Pseudergasilus zaconnis, was transferred to the genus Ergasilus[3].

Clinical signs

Infection with Ergasilus zacconis can cause anaemia in heavy infestations.

Pathological changes (haemorrhage, congestion, proliferation of the epithelia, aedema, mucus secretion, etc.) are observed in the gill[4]. Heavily infected fish exhibit growth retardation resulting from anorexia.

Since this parasite is not infectious to human, it is harmless in food hygiene.

Diagnosis

Diagnosis is determined by clinical signs and observation of adult Ergasilus.

References

  1. Nakajima, K. and S. Egusa (1973) Parasitic copepode, Pseudergasilus zacconis YAMAGUTI, found on the gills of cultured ayu, Plecoglossus altivelis ? II. Histological damage and bathing effects of some chemicals. Fish Pathol 9:95-99
  2. Kim, I.H. and K. Nagasawa (2006) Redescription of Ergasilus zacconis (Copepoda: Poecilostomatoida: Ergasilidae) parasitic on the freshwater fish Zacco platypus from Japan. Korean J Syst Zool 22:121-125
  3. Kim, I.H. & Choi, SK (2003) Copepod parasites (Crustacea) of freshwater fishes in Korea. Korean J Syst Zool 19:57-93
  4. Nakajima, K. and S. Egusa (1973) Parasitic copepode, Pseudergasilus zacconis YAMAGUTI, found on the gills of cultured ayu, Plecoglossus altivelis. I - Morphology. Fish Pathol 8:106-110