Proceedings of the United States National Museum
Total Page：16
File Type：pdf, Size：1020Kb
PROCEEDINGS OF THE UNITED STATES NATIONAL MUSEUM issued j^Jf^vA, v)?^| by th SMITHSONIAN INSTITUTION U. S. NATIONAL MUSEUM Vol. 107 Washmgton : 1958 No. 3390 NORTH AMERICAN COPEPODS OF THE FAMILY NOTODELPHYIDAE By Paul L. Illg ^ Introduction The uotodelphyid copepods are almost universally inhabitants of the body cavities of ascidians. Correlated with this specialized mode of existence is the elaborate series of structural modifications displayed by these organisms. Preservation of fundamental characteristics, in spite of a high degree of adaptive radiation, renders the group a well- defined natural unit. The members of this family are poorly known, however, over the greatest extent of their occurrence and information concerning North American representatives is particularly meager. Despite their interesting biological features, these ascidicoles have been neglected by the taxonomist and ecologist alike. To the specialist on copepods the principal limitation on availability of notodelphyids is the obvious fact that their occurrence is dependent upon that of tlie host organisms. The methods of obtaining and working over ascidians do not form a usual part of the operations of workers on the copepods. Considering the significant biological implications of the ascidicoles, they have received little notice from the specialists on ascidians. It is rare to chance upon a note in the ' Department of Zoology, University of Washington, Seattle, AVash. 463 464 PROCEEDINGS OP THE NATIONAL MUSETIM vol. io7 literature on ascidians that even mentions these almost constantly present associates. The record of these organisms, from the standpoint of world distribution, is equallj'' scanty. The onl}'- outstanding faunistic records are provided by the excellent knowledge available of occurrence of ascidicoles on the coasts of the Scandinavian countries and on the Mediterranean shores of Europe. As a result of the lack of distributional knowledge and ignorance of the majority of extant forms, the s^^stematics of this group is in a very undeveloped state. The scattered references to the group have never been brought together on a large scale. The neglect of the ascidicoles is undoubtedly at least partially due to the fact that both they and their hosts have distinctly minor practical or economic importance. The worker on the copepods thus is confronted first with the problem of obtaining host material, and then with the even greater difficulty of obtainmg valid determinations of the host species. No large-scale work has been published on the North American notodelphyids. The records available from this area, including Greenland, are from the reports of Blake (1933), Gray (1938), Hansen (1923), Henderson (1931), Herdman (1898), Huntsman (1912), Pearse (1947, 1952), Stephenson (1913), and Wilson (1920, 1932, 1935a, 1935b). The present material has been available from the most diverse situations in North America. Although the primary aim has been the establishment of the North American rejjresentation of the family Notodelphyidae, a thorough stud}'" along these lines has required careful perusal of the records of world distribution. Since this is the first time a compilation of such extent has been available, the opportunity is taken of presenting a bibliography^ of the notodelphyids and s^^nonymies of the species. References compiled in the bibliog- raphj'' are all those which were thought significantly to affect taxo- nomic evaluation or provide definite information as to distribution. Incidental references to various of the genera or species are scattered throughout the whole of the literature on copepods and complete coverage of such items was not attempted. In the listing of hosts, all the different names used by authors are presented, although it is presumed some are synonymous. Further, these are quoted as found in the literature, with such attribution of authority as provided in the reference concerned only. The task of bringing the usages in- volved and the identifications of hosts into accordance with the modern classification of ascidians must devolve upon a specialist in that field. There is still the need for similar treatment of the remaining families of ascidicolous copepods. It is hoped that the present attempt will NOTODELPHYID COPEPODS—ILLG 465 demonstrate that the project is a rewarding one in terms of the array of biological information disclosed. In the genera not actually studied in the present work the taxonomy of the earlier workers is accepted and the scheme of G. Sars (1921) is used, supplemented, where it is incomplete, from Schellenberg (1922), However, the necessity of proposing new genera to recognize the new information concerning the anatomy of the group brought forth from the study has led to the formation of six new combinations as nomenclatural concepts. Most of the reallocations of species have involved those originally proposed in the genus Doropygus, which, by combining the work of Sars in 1921 and the present study, has been finally subdivided into four genera. The present study has produced records in 11 genera of 23 species, of which 14 are described as new to science. New findings of zoogeographic interest include the rediscovery of a typical arctic species, unreported since its original description, now found in collections ranging from Point Barrow, Alaska, to the Gulf of Maine, and to the north coast of Siberia. Still another instance is the establishment of the occurrence of a long-known Mediterranean species in considerable numbers along the Gulf Coast of Florida. A large number of species seems to be entirely restricted to North America, but such findings as the above leave reason to assume that some of these species will be found to have wide distributions. The almost cosmopolitan species, Doropygus pvlex Thorell, has been found only on the east coast of North America. Only six typically European species have so far been found in the American fauna. Acknowledgments The present study has been made possible by the encouragement and considerable contribution of a large gi'oup of colleagues and associates and the authorities of a number of institutions. It is a pleasm"e to record my indebtedness as a partial expression of my gratitude. The use of facilities and materials was made possible by the land offices of the authorities of the United States National Museum; the American Museum of Natural History; the Friday Harbor Laboratories, University of Washington; the Ai'ctic Research Laboratory; and the Oceanographic Institute, Florida State University. Curator Dr. Karl Lang, of the Naturhistoriska Riksmuseet, Stocldiolm; Dr. C. Delamare Deboutteville, of the Laboratoire Arago, Banyuls, France; and Mr. J. H. Stock, of the Amsterdam Museum, have furnished me valuable information and literature and have provided important specimens. Encouragement, assistance in collecting and identifying materials, and aid in the task of preparing this report have been most freely given 466 PROCEEDINGS OF THE NATIONAL MUSEUM vol. iot l)y Dr. Waldo L. Schmitt, Miss Lucile McCain, Dr. Fennor A. Cliaco, Frederick M. Bayer, Dr. R. E. Blackwelder, Mrs. Thomas Biircli, Professor and Mrs. G. E. MacGinitie, Dr. Harold Humm, Dr. William Siitcliffe, Jr., Dr. John L. Mohr, Dr. J. E. Lynch, Dr. Robert Fernald, Dr. Emery F. Swan, Dr. Donald P. Abbott, and Dr. Cadet Hand. Methods The problems of collection of notodelphyids is in the main that of obtaining quantities of ascidians, the host organisms. Ascidians are entirely marine, very few tolerating even an approach to brackish conditions. Availability of free-flov,'ing currents of water is a prime requisite for abundance of ascidians, which are notable and con- spicuous members in the aggregations of animals encrusting piers and floats. However, personal experience in the accumulation of the present series indicates that the most favorable site for obtaining infested ascidians would be bottom-dwelling beds, usually those well below the level of tidal fluctuation. Dredging is therefore the recommended procedure for collecting the hosts. Relatively few notodelphyids inhabit compound ascidians. The few that so occur are most readily obtained by observation of the living host. There ususally is a high degree of transparency, or at least translucence, of the compound tunicate, which favors detection of the dissimilar texture, and often color, of the infesting copepod, particularly under illumination for microscopic examination. Teas- ing out of zooids is necessary for the capture of the forms inhabiting the branchial cavities. Teasing of the matrix or systematic slicing of the colony may produce favorable results in the search for the species that live in the common channels or lie independently in matrical cavities. The majority of forms live within the bodies of simple, or solitary, ascidians. These may be tumbled out by wholesale slicing of quan- tities of ascidians. It is preferable, however, to obtain the ascidicoles by dissection of the host, which procedure assures the preservation of an ascidian specimen for taxonomic identification and yields the optimum in details of biological relationships of host and com- mensal or parasite. For dissection it is necessar}^ to orient the ascidian. If the siphons are obvious, the tunic may be slit well away from them and peeled like rind from the enclosed If there is surface a body. no landmark , for orientation, the best procedure is cautious peeling to expose the body and establish the location of the siphons. The specimen then should be sectioned just to one side of the median plane, preferably by a cut of deeply inserted scissors. The median plane is established as the line passing through the siphons and the cut is arranged to NOTODELPHYID COPEPODS—ILLG 467 start at one siphon and end at the other, leaving the resultant halves united by the intersiphonal portion of the body. In individuals with thin tests this procedure can be accomplished by cutting directly through test and all. The body, after sectioning, may be spread open and pinned down, preferably under fluid. Exposed to view will be the inner wall of the pharynx with the mid-dorsal line running down the center.