Amino Acids in Seven Species of Cestodes

Abstract

Nitrogen and amino acid analyses were performed on acid hydrolysates of seven species of cestodes (Taenia pisiformis, Hydatigera taeniaeformis, Taeniarhynchus saginatum, Raillietina cesticillus, Dipylidium caninum, Moniezia expansa, Raillietina cesticillus, and Hymenolepis diminuta). The three taenid species had significantly more nitrogen than the other four. Certain species were distinguishable from all the others by one significantly abundant amino acid. Comparative biochemical studies on animals have begun to shed additional light on taxonomic relationships (Johnson and Wicks, 1959; Sibley, 1962). In the main, these studies have utilized electrophoretic analysis of proteins from serum or from eggs. In the present study, extension of this chemical classification has involved the quantitative comparison of a-amino acids released by acid hydrolysis of whole body proteins from seven species of cestodes. MATERIALS AND METHODS Freeze-dried samples of six species of tapeworms were obtained from Dr. I. G. Kagan, Communicable Disease Center, Atlanta, Georgia. Three weighed samples of each of these worms and of 28-day-old, freeze-dried Hynenolepis diminuta from Wistar strain rats were hydrolyzed in 6 N HC1 in vacuo at 110 C for 24 hr. Amino acids in dried hydrolysates were determined quantitatively by ion exchange chromatography using sulfonated styrene-8% divinylbenzene copolymer resin columns as described in a previous paper (Goodchild and Dennis, 1965). Nitrogen determinations were performed on hydrolysates by the nesslerization method of Lang (1958). Data were analyzed statistically using Student's t test for probability of significance of difference between means. OBSERVATIONS AND RESULTS Means and their standard errors for per cent nitrogen in the seven species of tapeworms (Taenia pisiformis, Hydatigera taeniaeformis, Taeniarhynchus saginatum, Dipylidium caninum, Moniezia expansa, Raillietina cesticillus, and Hymenolepis diminuta) are given in Table I. The first three species, representing the family Taeniidae, had significantly more nitrogen than any of the other cyclophyllideans, representing the families DipyReceived for publication 16 August 1965. * This investigation was supported in part by a research grant (PHS-E795) from the NIAID of the NIH, PHS. lidiidae, Anoplocephalidae, Davaineidae, and Hymenolepididae, respectively. No significant difference in nitrogen was noted among the species in these four families. Table I also shows the means and standard error of the mean for per cent of ammonia and 17 amino acids in the seven species of tapeworms. Three species could be distinguished from the others by one significantly abundant amino acid: proline in H. taeniaeformis, alanine in T. saginatum, and histidine in H. diminuta.