A Review of the Crayfish Genus Astacoides (Decapoda: Parastacidae)
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A Review of the Crayfish Genus Astacoides (Decapoda: Parastacidae) • HORTON H. HOBBS, JR SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY • NUMBER 443 SERIES PUBLICATIONS OF THE SMITHSONIAN INSTITUTION Emphasis upon publication as a means of "diffusing knowledge" was expressed by the first Secretary of the Smithsonian. In his formal plan for the Institution, Joseph Henry outlined a program that included the following statement: "It is proposed to publish a series of reports, giving an account of the new discoveries in science, and of the changes made from year to year in all branches of knowledge." This theme of basic research has been adhered to through the years by thousands of titles issued in series publications under the Smithsonian imprint, commencing with Smithsonian Contributions to Knowledge in 1848 and continuing with the following active series: Smithsonian Contributions to Anthropology Smithsonian Contributions to Astrophysics Smithsonian Contributions to Botany Smithsonian Contributions to the Earth Sciences Smithsonian Contributions to the Marine Sciences Smithsonian Contributions to Paleobiology Smithsonian Contributions to Zoology Smithsonian Folklife Studies Smithsonian Studies in Air and Space Smithsonian Studies in History and Technology In these series, the Institution publishes small papers and full-scale monographs that report the research and collections of its various museums and bureaux or of professional colleagues in the world of science and scholarship. The publications are distributed by mailing lists to libraries, universities, and similar institutions throughout the world. Papers or monographs submitted for series publication are received by the Smithsonian Institution Press, subject to its own review for format and style, only through departments of the various Smithsonian museums or bureaux, where the manuscripts are given substantive review. Press requirements for manuscript and art preparation are outlined on the inside back cover. Robert McC. Adams Secretary Smithsonian Institution SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY • NUMBER 443 A Review of the Crayfish Genus Astacoides (Decapoda: Parastacidae) Horton H. Hobbs, Jr. SMITHSONIAN INSTITUTION PRESS Washington, D.C. 1987 ABSTRACT Hobbs, Horton H., Jr. A Review of the Crayfish Genus Astacoides (Decapoda: Parastacidae). Smithsonian Contributions to Zoology, number 443, 50 pages, 23 figures, 1987.—The crayfish fauna of Madagascar consists of six species belonging to the endemic genus Astacoides. Four of them, originally recognized as varieties of a single species Astacoides madagascarensis and subsequently accorded subspecific status, are elevated to specific rank. Two, A. crosnieri and A. petiti, are described as new. Following remarks on the limited range of the genus, which appears to be confined to higher elevations in the eastern part of the island between 18° and 25° South latitude and 46° to 49° East longitude, are notes on the organization of the text and a resume of our previous knowledge of the genus. This is followed by discussions of the taxonomic characters considered in the study, the common origin of the disjunct Astacoides with other parastacid stocks, and the evolution and interrelationships of the Madagascan species. A diagnosis of the genus accompanies a key provided for the recognition of its members. A synonymy, diagnosis, description, statement of range, list of localities and specimens examined, and illustrations are provided for each species. OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded in the Institutions annual report, Smithsonian Year. SERIES COVER DESIGN: The coral Montastrea cavernosa (Lin- naeus) Library of Congress Cataloging in Publication Data Hobbs, Horton Holcombe, 1914- A review of the crayfish genus Astacoides (Decapoda: Parastacidae) (Smithsonian contributions to zoology ; no. 443) Bibliography: p. I. Astacoides—Classification. 2. Crustacea—Classfication. 3. Crustacea—Madagascar Classification I. Title. II. Series. QL1.S54 no.443 [QL444.M33] 591s 86-13093 [595.3'841] Contents Page Introduction 1 Acknowledgments 3 Remarks on Presentation 3 Synonymies 4 Diagnoses 4 Descriptions 4 Type-Localities 4 Types 4 Range and Specimens Examined 4 Remarks 4 Vernacular Names 4 Resume of Previous Knowledge 4 Comments on Previous Studies 8 Taxonomic Characters of the Genus Astacoides 8 Sexual Dimorphism 8 Rostrum 9 Areola 9 Postorbital Ridge 9 Spination of Carapace and Abdomen 9 Eyes 10 Antennal Scale 10 Mandible 10 Third Maxilliped 11 Sternal Keel 13 Branchiae 13 Pleurocoxal Lappets 16 Abdomen 16 Origin and Interspecific Relationships 18 Characters Compared 26 The Genus Astacoides 26 Key to the species of the Genus Astacoides 27 Astacoides crosnieri, new species 27 Astacoides petiti, new species 31 Astacoides granulimanus Monod and Petit, new status 33 Astacoides madagascarensis (H. Milne Edwards and Audouin), new status . 38 Astacoides caldwelli (Bate), new status 41 Astacoides betsileoensis Petit, new status 44 Literature Cited 48 A Review of the Crayfish Genus Astacoides (Decapoda: Parastacidae) Horton H. Hobbs, Jr. Introduction mann, 1961) does not seem a satisfactory nomenclature. To students of crayfishes, the genus Astacoides, endemic Holthuis (1964) reluctantly accepted the infraspecific des- on the Island of Madagascar, holds a number of special ignation of at least one of the varieties recognized by Monod interests. For more than a hundred years those interested and Petit, for he remarked (page 316): in zoogeography have been puzzled as to the origin of its The differences from the other forms are so striking that I would be members and how they reached the island. Their isolated inclined to consider A. m. betsileoensis an independent species. As however, position, emphasized by the absence of crayfishes in Africa Monod and Petit's opinion that it is only a subspecies of A. madagascarensis is based on much more material than that which I have at my disposal, I and the Indian subcontinent, has led to interesting, if not abide, for the time being at least, by their decision. satisfying speculations. In only a few parts of the world— Mexico (See Villalobos, 1955, 1983), Guatemala, Hondu- Monod and Petit (1929:29-37) provided a rather detailed ras, and Cuba (see Hobbs and Villalobos, 1964) in the discussion of the surprisingly small known range of the Western Hemisphere, and Madagascar, New Guinea, Aru genus that extends on the Hauts Plateaux from the region Islands, and Misol (see Holthuis, 1949, 1950, 1982), and of Anjozorobe, a short distance north of Tananarive, south- northern Australia in the Eastern Hemisphere—have cray- ward for about 700 kilometers to the Isaka Valley. On the fishes been successful in invading the tropics. Where they east the range is limited largely by the escarpment bounding have done so, many, if not most, of the species live at higher the plateau, the crayfishes descending the rivers to about elevations as they do on Madagascar where most of the 800 meters. On the west they are not known to be present known localities occur between 800 and 2000 meters above beyond the headwaters of the westward flowing streams. sea level. Few crayfishes living in temperate latitudes have Thus the genus occupies a range of some 700 by 100 been found at elevations so high as the latter. Unique in kilometers in the southeastern part of the island (Figure 1). appearance is the seemingly excessively spiny Astacoides It is regrettable that so little detailed habitat data are betsileoensis Petit, 1923, which probably exhibits the most available for these crayfishes. On the basis of what has been ornate appearance of any extant, and very likely extinct, reported, one would conclude that they are virtually limited species in the ancestry of the two crayfish superfamilies, to streams of the high plateaus where they are most abun- Astacoidea and Parastacoidea. Although none of the cray- dant in headwaters, brooks, and swifter rivers flowing fishes living on Madagascar attain a size approaching that through forests. Moreover, little information concerning of the Tasmanian Astacopsis gouldi Clark, 1936, all are the habitats or habits of previously unrecorded specimens comparatively large, sometimes attaining carapace lengths accompanies them. The reason for lamenting the lack of of more than 80 mm. such data is that, judging by combinations of morphological Intriguing also is the fact that the several recognized features exhibited by the several forms, adaptive radiation forms, some even having been accorded different vernacu- appears to have played a more important role in the evolu- lar names, have been recognized as "varieties" of a single tion of Astacoides than existing information suggests. species (Monod and Petit, 1929). That such extreme varia- My active interest in the Madagascan crayfishes was kin- tion exhibited by the crayfish fauna of the island might dled when a decade ago my friend Alain Crosnier asked if occur in a single gene pool appeared unlikely to me, and I might be interested in examining several lots of specimens their subsequently being recognized as subspecies (Pretz- he had collected on the island. Aware that the fauna had been reported to consist of four varieties of a single species, Horton H. Hobbs, Jr., Department of Invertebrate Zoology, National Museum of I assumed that the specimens could be assigned quickly to Natural History, Smithsonian Institution, Washington, D.C. 20560. one or more of them and returned. Such prompt identifi- SMITHSONIAN