Fine structure of the peritrichous ectocommensal Zoothamnium sp. with emphasis on its mode of attachment to penaeid shrimp

Abstract

The colonial peritrich Zoottiamnium sp. is a common ectocommensal of shi'imp. Heavy branchial infestations of this protozoan can cause mass moi'talities of commercially important penaeid species in shrimp culture. In an effort to better understand the morphology of these organisms, the ciliates and their attachment to gills and pereiopods of Penaeus aztecus and P. setiferus were examined by transmission and scanning electron microscopy. Each zooid contains peristomial rows of cilia, numerous food vacuoles, a large macronucleus, one or more contractile vacuoles, freeribosomes, abundant mitochondria, and rough endoplasmic reticulum. The contractile spasmonehie is surrounded by striated tubules that appear to develop from scopular cilia. The pellicular surface is crenated and has numerous pores. The base of the ciliate's stalk forms a circular disc that fuses with the epicuticle but does not penetrate the underlying cuticle or epithelium. Intertwining microflbrils and osmiophilic particles in the stalk accumulate along the base and merge with the cuticular surface coat. This mode of attachment inflicts no damage to the host tissue and elicits no appreciable pathological response. The shrimp apparently suffocate when dense colonies reduce the respiratory surface area.

Epibiosis in Crustacea: an overview

“…on the gills of the decapod Callinectes sapidus in culture (Couch, 1966), and the peritrich ciliates Zoothamnium spp. in penaeid shrimp cultures (Overstreet, 1973;Lightner, 1975;Couch, 1978;Foster et al, 1978;Morado & Small, 1995). Diverse control methods have been developed in order to prevent these problems, such as formalin baths (concentrations between 15 and 250 ppm), e.g., placing the crustacean in a tank with 25 ppm formalin to treat Zoothamnium infestations (Johnson, 1976a;Lightner, 1988;Morado & Small, 1995).…”

Ciliate parasites and related diseases of crustacea: A review

“…Zoothamnium spp. are major concerns in penaeid shrimp culture (Overstreet, 1973;Lightner, 1975;Couch, 1978;Foster et al, 1978). Indeed, densities of Zoothamnium on the gills of penaeid shrimp are directly correlated with shrimp density, and in one case, with shrimp mortality (Overstreet, 1973).…”

Distribution and Prevalence of 15 Species of Epibiont Peritrich Ciliates on the Crayfish Cambarellus Patzcuarensis Villalobos, 1943 in Lake Pátzcuaro, Michoacán, Mexico

“…The impact of the population s or communities of ciliated Protozoa on their hosts has been considered both without repercussion (Foster et al, 1978), or in relation with some damage to their hosts, like some impairment of swimming ef ciency of the host (Henebry & Ridgeway, 1979;Evans et al, 1979). The epibionts appeared to be involved in mortality of pond-reared shrimps (Overstreet, 1973) or in reducing subitaneous egg production and naupliar and adult survival, and, for heavily infested females, attachment of these ciliates may block the genital pore (Weissman et al, 1993).…”