Relationships of Some Species of Digenea with the Marine Prosobranch Littorina littorea (L.) III. The Effect of Larval Digenea on the Glycogen content of the Digestive Gland and Foot of L. littorea

Abstract

Summary1. Individual chemical estimations of the glycogen concentration of the digestive gland and the foot were made on 272 uninfected L. littorea and 395 L. littorea infected with larval Digenea from Scalby Rocks, North Yorkshire, during the period from September 1966 to November 1967.2. The glycogen concentrations of the digestive gland and the foot of both infected and uninfected L. littorea showed pronounced seasonal changes, being highest during the autumn and lowest in the spring. Infected L. littorea had less glycogen in the digestive gland and foot than had uninfected L. littorea, and the amount of reduction was characteristic for each of the three species studied, namely Cryptocotyle lingua, Renicola roscovita and H. leptosoma. Infection with C. lingua caused greater decrease in the glycogen concentration of the digestive gland, while infection with R. roscovita had a more marked effect on the foot. The effect of infection with H. leptosoma and with concurrent infections with two species are described and considered.3. The seasonal changes in the amount of glycogen in the digestive gland and the foot of uninfected and infected L. liitorea are considered in relation to seasonal reproductive changes and the ecology of the host at Scalby Rocks.

Carbohydrate reserves and phosphatase activity in the mollusc-trematode relationship ofMytilus edulisL. andProctoeces maculatus(Looss, 1901) Odhner, 1911

“…Cheng and Burton (1966) observed a significant decrease in the amount of stored glycogen in Crassostrea virginica infected with sporocysts of Bucephalus sp. Robson and Williams (1971) found the concentrations of glycogen in the digestive gland and foot ofLittorina Uttorea infected with the redia ofHimasthla leptosoma to be essentially the same as corresponding uninfected tissues. The works of Friedl (1961) and Vernberg and Hunter (1963) suggest that some trematodes may have a metabolism based on substances other than carbohydrates.…”

Parasites alter community structure

“…Developing trematode rediae obtain nutrition by consuming the host's visceral hump, which contains the gonad, digestive gland, and some connective tissue (24,27). Extensive damage is induced in L. littorea's digestive gland during the course of trematode infection (22) as a result of direct consumption by parasite larvae (24), mechanical pressure (22), flooding with parasite wastes (22), loss of glycogen (28) and glucose (29), and autophagic and autolytic activity (22). Additionally, parasitism causes reduced fecundity and, often, a complete cessation of gamete production in the host (30,31).…”