THE ACANTOR MEMBRANES OF TWO SPECIES OF ACANTHOCEPHALA.

Acanthocephalus jacksoni and Echinorhynchus gadi acanthors have four enveloping membranes. A literature review indicates many inconsistencies concerning the description and number of acanthor membranes even within a single species. The greatest variation observed in the membranes is in the "fibrillar coat. " The membranes are more easily observed in fresh, unfixed smears of eggs. It is recommended that the traditional citing of three membranes as the typical description be reviewed with the suggestion that four membranes are typical for the acanthor stage. Since the time of Burow's (1836) original description of three membranes, the number of membranes reported for the acanthocephalan acanthor has ranged between two and five in different species, and even within a single species. This is especially true of reports for Macracanthorhynchus hirudinaceus. Anton Meyer (1928) described the development of four membranes in this species. Yet, in a later work with this same species, von Brand (1940) refers to only three membranes. There are many similar accounts in which three membranes are cited for this species. Most investigators have not considered the possibility of constancy of number for these membranes. Moore (1946 and 1962), in describing the number for two species, Moniliformis dubius and Mediorhynchus grandis, states in the first instance that there are "two distinct shells plus two adhering membranes" whereas, in the second instance he describes "two shells and three accessory membranes. " This problem has been referred to on several occasions. Manter (1928) stated that "textbooks are incorrect in ascribing three eggshells to the eggs of M. hirudinaceus. Four are clearly present . " An earlier reference was made to this problem by Korschelt and Received for publication 25 March 1964. * This study was supported, in part, by a National Defense Educational Act Fellowship and was submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Zoology at The University of New Hampshire. t Present address: Department of Biology, Suffolk University, Boston, Massachusetts. Heider (1895) in which they made note of the fact that "ordinarily three such embryonal membranes are formed" but that in the case of E. gigas "four of them are present. " Recently, Rogers (1962) has stated that "they consist of three or four layers. " MATERIALS AND METHODS Two easily accessible species of Acanthocephala were investigated in this study to determine whether or not their mature acanthors demonstrated any basic similarities or differences in the nature of their enclosing membranes. The two species, Acanthocephalus jacksoni Bullock and Echinorhynchus gadi (Zoega) Miiller, are both members of the Palaeacanthocephala. A. jacksoni was obtained from the intestine of various trout at the New Hampshire Fish Hatchery, New Hampton, New Hampshire. E. gadi was collected from the intestine of pollack and cod brought in to Gloucester, Massachusetts by commercial fishermen. The acanthors of both of these species have been described previously. Bullock (1962) described the acanthor of A. jacksoni and Hamann (1891) illustrated the acanthor of E. gadi. Both had suggested the presence of four membranes although neither cited them as such in their descriptions. Mature and gravid females of both species were collected at different seasons of the year: spring, summer, and fall for A. jacksoni and winter for E. gadi. Some were relaxed in distilled water, fixed in various fixatives, i.e., Bouin's, Helly's, and Demke's and treated with various stains. Others were sacrificed immediately upon procurement from the intestine of the definitive host. Freshly obtained females were rinsed in a Ringer's solution to remove debris usually found adhering to the body and hooks of the Acanthocephala. The worms were then blotted dry and the contents of the pseudocoel smeared onto a glass slide. The smears were allowed to air dry