Spectrophotometric Characterization of Integumental Pigments from Uninfected and Acanthocephalus dirus-Infected Asellus intermedius

Abstract

Study of methanolic HCI (19:1, v/v) extracts of the integumental of Asellus intermedius revealed two ommochrome fractions: an ommatin and an ommin. Amounts of both types of were decreased in isopods that harbored larvae of Acanthocephalus dirus. Differrences in absorption between pigment extracts from infected and uninfected isopods were as high as 61% for the ommatin fraction and 74% for the ommin fraction. The ultraviolet absorption spectrum for a methanolic HC1 extract of 29 A. dirus, removed from a group of isopods, resembled the ultraviolet absorption curve observed by using the pigment extracted from infected isopods as a blank and the extract of pigment from uninfected isopods as the sample. Competition between developing acanthocephalan and developing isopod for amino acid resources of the ommochrome pathway may be the cause of the pigmentation dystrophy that occurs in North American freshwater isopods infected with species of Acanthocephalus. North American freshwater isopods infected with species of Acanthocephalus exhibit altered integumental pigmentation described as dichromatism (Seidenberg, 1973, for Asellus intermedius infected with Acanthocephalus dirus [Van Cleave, 1931] Van Cleave and Townsend, 1936) or depigmentation (Muzzall and Rabalais, 1975a, b, c, for Lirceus lineatus infected with Acanthocephalus jacksoni Bullock, 1962). Oetinger and Nickol (1981) documented further the occurrence of altered integumental pigmentation in these species as well as in L. garmani infected with A. dirus. They found altered pigmentation to also include pigment associated with the male reproductive system, but not that of isopod eyes. From microscopic examination and spectrophotometric analyses of in situ were no detectable differences in alteration of pigmentation relative to intensity of infection, sex, or size of parasites (Oetinger and Nickol, 1981). Quantitative and qualitative chemical differences in pigment extracts from North American freshwater isopods infected with species of Acanthocephalus have not been reported. Baldwin and Beatty (1941) studied pigmentation of Asellus aquaticus and described a melanin-type pigment, i.e., not extractable Received 5 December 1980; revised 21 April 1981; accepted 5 October 1981. * Present address: Department of Biology, Houghton College, Houghton, New York 14744. with methanol, ethanol, ether, petroleum ether, benzene, chloroform, carbon disulphide, pyridine, or trichloracetic acid. The carotenoids, a-carotene and cryptoxanthine were extracted and characterized. Needham and Brunet (1957) were the first to characterize the melanin-type pigment of A. aquaticus. They considered the postmortem red color described by von Kaulbersz (1913) to be evidence of a reversible, oxidation-reduction reaction. After extraction of carotenoids with acetone they found the dark brown pigment could be completely extracted with 1% (w/v) HC1 in absolute methanol or 1% (w/v) aqueous HCl. The extract was golden and became pink when treated with reducing agents at pH 4 to 6. Absorption maxima of the oxidized form were 250, 380, and 465 nm whereas those of the reduced form were 280, 385, and 490 nm. Chromatography was used to demonstrate the similarity of pigment extracts with xanthommatin, and alkaline hydrolysis revealed further similarities. They concluded that pigment extracted from A. aquaticus belonged to the xanthommatin group of ommochromes and that, there is no reason to believe that, when fresh, the solution contains significant amounts of other pigments (Needham and Brunet, 1957, p. 208). Needham (1970) re-examined the chemical nature of the integumental of Asellus aquaticus. After removing alimentary tract and gonads, washing, and extracting the carotenoids, he found, in addition to the origi-