Studies on the life cycle of Pallisentis nagpurensis Bhalerao, 1931 (Pallisentidae; Acanthocephala) parasitic in the fish Ophiocephalus striatus (Bloch)

Abstract

The life cycle of Pallisentis nagpurensis involves the fish Ophiocephalus striatus as the final host and the copepod Cyclops strennus as the intermediate host. The embryonated eggs are adapted to float in water. The development of the acanthors up to the stage of infective acanthellae takes place in the haemocoel of the cyclops in 15-20 days. The juveniles develop to maturity in the intestine of the fish after about 50 days. Incompletely developed juveniles penetrate the intestinal wall adjacent to the liver and then encyst in the peripheral tissues of the liver. Cannibalism among the fish seems to help the establishment of the encysted worms for normal development within the intestine. The life-cycle of the worm is neatly geared to the feeding habits of the host fish. A number of transport hosts have also been observed. Study has also been made on the morphology of various developmental stages of the worm.

Pallisentis rexus from the Chiang Mai Basin, Thailand: ultrastructural studies on egg envelope development and the mechanism of egg expansion

“…Egg expansion in contact with water seems to be a common and distinctive feature of the genus Pallisentis. Two other members of this genus have been described as undergoing egg expansion, namely P. nagpurensis (George & Nadakal, 1973) and P. panadei (Rai, 1967). However, the nature of the expansion in these species was only described in these publications in a preliminary manner and the descriptions do not include information on the expansion mechanism.…”

“…The observations of the present study were aimed at providing a detailed description of the development and final configuration of the egg envelopes of the eoacanthocephalan, P. rexus. These studies have also facilitated the first ultrastuctural study into the mechanism by which mature eggs of acanthocephalans in the genus Pallisentis expand enormously when they contact fresh water (Rai, 1967;George & Nadakal, 1973;Wongkham, 1998).…”

Embryonic development of eggs and stereological analysis of body of Neoechinorhynchus buttnerae (Golvan, 1956) (Eoacanthocephala: Neoechinorhynchidae)

“…The layers that coat the eggs have the purpose of promoting the protection of the larva from any mechanical and chemical actions of the host and the environment in which they happen to be, and present strategies that help in its attractiveness to the host, thus facilitating its ingestion (Wharton, 1983; Nikishin, 2001). In the case of Pallisentis nagpurensis eggs, for example, the thin membrane lining the eggs in contact with water swells and floats freely, facilitating their ingestion by the host (George and Nadakal, 1973). However, for the eggs of Leptorhynchoides thecatus , the thin outer membrane of the egg is lost in the environment, leaving the fibrillated structure exposed, allowing the eggs to settle in filamentous algae that will serve as food for the intermediate host (amphipods) (Uznanski and Nickol, 1976).…”