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Hydrobiologia (2008) 595:7983 DOI 10.1007/s10750-007-9112-3
FRESHWATER ANIMAL DIVERSITY ASSESSMENT
Global diversity of hairworms (Nematomorpha: Gordiaceae) in freshwater
George Poinar Jr.
Springer Science+Business Media B.V. 2007
Abstract Freshwater hairworms (Gordiaceae) and marine hairworms (Nectonematoidea) comprise the phylum Nematomorpha. Only the freshwater forms are discussed here. While freshwater hairworms develop as parasites of both aquatic and terrestrial arthropods, they all enter fresh water to mate, oviposit and produce infective stages (preparasitic larvae). The global species diversity of freshwater hairworms based on published descriptions is approximately 326 species and a conservative estimate for the global species diversity in this group would be around 2,000 species.
Keywords Nematomorpha Hairworms
Gordiaceae
Introduction
There are two classes in the phylum Nematomorpha: the freshwater hairworms or Gordiaceae, comprising a dozen genera and the marine hairworms or Nectonematoidea, with a single genus. The host range,
species diversity and distribution of the Nectonematoidea were summarized by Poinar and Brockerhoff (2001) and since all of the ve known species are marine, they will not be included here.
While all freshwater hairworms develop as parasites in arthropods, all enter fresh water to mate, oviposit, and infect paratenic hosts. Freshwater hairworm adults, eggs and preparasitic larvae occur in ponds, streams, lakes, and various man-made structures that retain water. The adults range from tan to black in color and from several centimeters to over a meter in length. The body wall is covered with a hard, opaque, multilayered cuticle that varies in texture from smooth to highly sculptured. The surface projections (areoles), warts and/or bristles on the epicuticle as well as the male tail, provide important taxonomic characters. While the anterior end can be attenuated, the tail may be rounded, bilobed, or even trilobed. Hairworm preparasitic larvae are capable of encysting (without development) in a wide range of paratenic hosts, including invertebrates and vertebrates. Development occurs in the body cavity of invertebrates (especially insects) that have ingested paratenic hosts (Poinar, 2001; Schmidt-Rhaesa, 1997; Smith, 2001; Hanelt et al., 2005) Fig. 1.
Species/generic diversity
Some 21 extant and two fossil genera of freshwater hairworms have been described worldwide (Table 1).
Guest editors: E. V. Balian, C. Lvque, H. Segers &K. MartensFreshwater Animal Diversity Assessment
G. Poinar Jr. (&)
Department of Zoology, Oregon State University, Corvallis, OR 97331, USAe-mail: [email protected]