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/ THE UNIVERSITY OF ILLINOIS LIBRARY NATURAL HISTORY SURVBY 5705 ILL, ., 4\ ^^^ V. 5 cop.4 . charge c on an books. is^^L^e^^rall't^'^overdue U. of/. Library ILLINOIS BIOLOGICAL MONOGRAPHS Vol. V April, 19 19 No. 2 Editorial Committee Stephen Alfred Forbes William Trelease Henry Baldwin Ward Published tTNDER the Auspices of the Graduate School by THE University of Illinois Copyright, 1920 by the University of Illinois Distributed Jxjne 7, 1920. CONTRIBUTIONS TO THE LIFE HISTORIES OF GORDIUSROBUS- TUS LEIDY AND PARAGOR- DIUS FARIUS (LEIDY) WITH TWENTY-ONE PLATES BY HENRY GUSTAV MAY Contributions from the Zoological Laboratory of the University of Illinois under the direction of Henry B. Ward, No. 144 THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY IN ZOOLOGY IN THE GRADUATE SCHOOL OF THE UNIVERSITY OF ILLINOIS 1917 TABLE OF CONTENTS PAGES Introduction 7 Material and Methods 10 Observations on Gordius robusius 16 Determination of Species 16 Habits of Adults 19 Early Development 21 Parasitism 23 Organogeny 29 29 Metamorphosis , Derivation of Tissues 29 Later Development 31 Observations on Paragordius varius 44 Determination of Species 44 Habits of Adults 44 Early Development 45 Parasitism 45 Organogeny 47 Discussion 56 Biology 56 Occurrence and Behavior of Adults 56 Behavior of Larvae 59 Infection and Intermediate Host 59 Developmental Period 60 Organogeny 60 Metamorphosis 61 Later Development 62 Physiology 68 Nutrition 68 Excretion 68 Functions of Nervous System 69 Relationships 70 Bibliography 72 Explanation of Plates 76 127] UFE HISTORY OF GORDIUS AND PARAGORDIUS—MAY INTRODUCTION The Gordiacea seem to have escaped the observation of the earlier writers or else to have been mistaken for filariae. Meissner (1856) and Villot (1874) who review the older literature, agree that the first reference to the group was made by Albert the Great. Linnaeus introduced the term Gordius on account of the resemblance of a mass of the worms to the Gordian knot. He included in the genus the three species G. aquaticus, medinensis the argillaceus and , representing respectively present families of Gordiidae, Mermithidae and Filariidae, only the first of which is today retained in the order Gordiacea. Dujardin was the first to give detailed descriptions of two species, Gordius aquaticus and Gordius tolosanus, and to point out the difference between Gordius on the one hand and Mermis on the other. Von Siebold and following him Meissner (1855) placed Gordius and Mermis together to form the order Gordiacea. Meissner's work on the anatomy and physiology of Gordius and Mermis is in many respects an excellent production and it is inconceivable how, after such observations, he could still regard the two groups as closely related. The work of Gren- acher (1868) on the anatomy of Gordius was a step in the right direction. He emphasized again the difference between Gordius and Mermis and stated that the two could not possibly belong to the same family. Villot was the first to take up the study of museum specimens and living material in larger quantities. His investigations were carried on for a long series of years and with an earnest desire to solve the problems of taxonomy, physiology and life history; but unfortunately did not con- tribute much to a clearer knowledge of the group. The problem was too great for the methods he employed. In England Baird described several species and in Germany von Lin- stow added a large number of names without giving descriptions adequate for identification. The greatest contributions to the taxonomy of the group have undoubt- edly been made by Camerano, chiefly because he had at his disposal more material than has ever been available to any other writer. He not only described a large number of species, but subdivided the group into several genera. Creplin (1847) had already established the genus Chordodes. Camerano (1897) carried the division farther in separating the genera Paragordius and Parachordodes from the genus Gordius. This separation was made purely on external characters. Montgomery in a paper coming out somewhat later also established a genus Paragordius which, so far as the anatomy of the forms is known, includes the same species as does that of 8 ILLINOIS BIOLOGICAL MONOGRAPHS {128 Camerano, but is founded on much more essential characters. That the genus has found universal acceptance is perhaps due more to Montgomery's characterization tljjn to that of Camerano. The genus Parachordodes has not been universally accepted; but here again the evidence presented in this report shows that the characters given by Cj^merano are accompanied by others which indicate a natural division of the group. He characterizes Gordius by the presence of a postcloacal ridge in the male and the absence of true areoles on the cuticula, Parachordodes by the absence of postcloacal lidge and the presence of areoles. In America several species were described by Leidy, but most of the systematic work was done later by Montgomery. Here as well as in Europe little more than pioneer work has been done. Descriptions and identi- fications have been made chiefly from preserved material and isolated specimens and only in a few cases from living material collected in abim- dance. The confusion that still exists in the group is due in a large measure to the fact that the variations within a species are very great while the differ- ences between species are relatively small. When isolated and often poorly preserved specimens are studied it is natural that essential characters are often overlooked and variations are taken for specific characters. This tends on the one hand to throw species together and on the other to separate members of a single species. The two characters causing the most confusion are size and color. Nearly all of von Linstow's descriptions include besides these only those that are common to nearly all Gordiacea. Such descriptions are useless. I have in my own collection specimens of a single species ranging in length from 10 to 50 cm. and in color from light brown to nearly black and others that are an iridescent gray. Even as late as 1910 Wesenberg-Lund identi- fied specimens as Gordius aquaiicus on account of their size and made the errors that I shall point out later. The light spots in the cuticula and the postcloacal ridge in the male have been taken as specific characters, and the species bearing either has usually without hesitation been assigned to Gordius aquaiicus. The ridge certainly is possessed by more than one species and may be a generic character while the white spots, as Montgomery suspected, are due to physiological con- ditions in the American species but may be due to structures in the hypo- derm in some of the European species. Altho the structure of the cuticula is one of the best specific characters, its use has led to confusion because different authors have studied it imder different conditions and have made different interpretations of what they saw. The erroneous theory that size, color and cuticular structures change with the age of the free living specimen has also contributed to the tangle. 1291 UFE HISTORY OF GORDIUS AND PARAGORDIUS—MA 7 9 The habits of different species are practically unknown. Most of the material has been found accidentally as isolated specimens and observations on behavior have been made mostly on animals in captivity as Wesenberg- Lund has already pointed out. The scant observations made on animals in nature are mostly referred to the group as a whole and not to any parti- cular species. But there is no reason for supposing that the habits of different species are the same, and they are not the same in the species forming the subject of this paper. The problem of the life history of the group has attracted much atten- tion. Villot at one time thought he had the complete cycle, but found later that he had to modify his theories. He observed the embryological development, the encystment of the larvae in a large number of animals, and the presence of nearly adult worms in beetles. After holding for a long time the view that the animals harboring the encysted larvae were inter- mediate hosts he finally concluded that the encysted larvae perish and that the life cycle is completed in some other way. Camerano indepen- dently arrived at the same conclusion. Blunck (1915) again speaks of an intermediate host. He states that the larvae of Gordius tolosanus penetrate soft-bodied animals and these in turn are devoured by Dytiscus larvae. Tadpoles form for the most part the intermediate host. Development is completed in Dytiscus and the worms escape soon after the beetle emerges from the puparium. The facts upon which these deductions are based are not given. Nothing has been published on the metamorphosis or the structure of the early parasite. In regard to the later organogeny Villot (1891) and Vejdovsky (1894) have supplied the only information. The adult organization is better known. If the knowledge of it is still incomplete, that is due chiefly to the fact that the material at hand has often been scarce and the methods employed have given only poor results. Here as elsewhere the greatest confusion has arisen because of the belief that what is true of one species must be true for all. Writers have not hesitated to denounce their fellow workers when their particular species failed to show what others had found in very different species. This very brief discussion of the literature on Gordiacea has been given not with the purpose of presenting an historical account of the subject but with the object of pointing out the need for further investigation and some of the difficulties that have presented themselves.

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