Haemaphysalis (Elongiphysalis) elongata Neumann Subgen. n. (Ixodoidea: Ixodidae): Structural Variation, Hosts, and Distribution in Madagascar

Abstract

The subgenus Elongiphysalis, designated here, consists of 3 Haemaphysalis species, elongata Neumann, subelongata Hoogstraal, and tiptoni Hoogstraal. The first 2 species are recorded from the northern to the southern end of Madagascar, the third only in the central eastern region. Each parasitizes tenrecs (Insectivora: Tenrecidae; genera Tenrec, Setifer, Hemicentetes, Nesogale, and Echinops). The 3 tick species have occasionally been taken from a single tenrec and combinations of 2 are frequently found on the same host. Each species is characterized by a special pattern of bizarre spurs on the first 2 segments of the legs and by a peculiar form of the capitulum. These structures apparently aid the tick in movement within the harsh, spiny host pelage. Soft-furred tenrec species are not known to be infested by adult haemaphysalines. Structural variation in adults of elongata (the type species of the subgenus) is described and the nymph and larva are described for the first time. The subgenus Elongiphysalis, a small grouping adapted to unusual hosts, probably evolved from the major Old World bird-parasitizing stem Ornithophysalis Hoogstraal and Wassef, represented in Madagascar by H. (O.) simplex Neumann. Larvae of both subgenera have simple campanulate palpi but nymphal and adult palpi are broadly salient. The 2 subgenera, which differ significantly in mild (Ornithophysalis) and extreme (Elongiphysalis) development of coxal and trochanteral spurs and of capitular spurs and/or spurlike angles, illustrate the range of adaptive radiation in structurally advanced groups of the genus Haemaphysalis. Tenrecs are believed to have reached Madagascar from the Ethiopian Faunal Region but haemaphysalines from the Oriental Region. It is suggested that a comparative investigation of viruses, rickettsias, and protozoa in these 3 areas may assist in elucidating concepts of the earlier and present distribution of insectivores and haemaphysalines. We define a new haemaphysaline subgenus, Elongiphysalis, of three species highly specialized for parasitizing the coarse-haired and spiny tenrecs (Insectivora: Tenrecidae) which are the most common and widely distributed endemic mammals of Madagascar. This subgenus is like the Old World bird-parasitizing subgenus Ornithophysalis (Hoogstraal and Wassef, 1974) in basic structural characters Received for publication 26 October 1973. *From Research Projects MR041.09.01-0037A 6HJ and MF51.524.009-3010B F61, Bureau of Medicine and Surgery, Department of the Navy, Washington, D. C. The opinions and assertions contained herein are the private ones of the authors and are not to be construed as official or as reflecting the views of the Department of the Navy or of the naval service at large. This study was assisted by Agreement 03-005-1 between the NIAID (NIH) and NAMRU-3. t Medical Zoology Department, United States Naval Medical Research Unit Number Three (NAMRU-3), American Embassy, Cairo, Arab Republic of Egypt. t Food and Agriculture Organization of the United Nations, P.O. Box 9254, Dar Es Salaam, Tanzania. (palpi simple campanulate in larvae, broadly salient in nymphs and adults), but its numerous, large, bizarre spurs on coxae and trochanters and angles on palpal margins replace the generally small spurs and straight or mildly curving margins of the bird-infesting subgenus. Adults of the type species of the new subgenus, Haemaphysalis elongata Neumann, are redescribed to illustrate the previously unrecognized rather considerable degree of structural variation within samples attributed to this taxon (Figs. 1-60), the immature stages are described for the first time (Figs. 61-75), and much new information on distribution and hosts is provided (Table I). Numerous problems in the biology, ethology, and host relationships of H. elongata require experimental and observational investigations. Studies on the ecological requirements, functional anatomy, and vector potential of Elongiphysalis species are also lacking. Two other tenrec-parasitizing haemaphysalines, H. (Ornithophysalis) simplex Neumann and H. (Sharifiella) theilerae Hoogstraal, are discussed in the section of Hosts and listed in Table II. Important literature on the Mada-