View - Kowalewski, M. - Virginia Tech

LABANDEIRA—PREDATORS, PARASITOIDS, AND PARASITESTylenchida, insect hosts include the Staphylinidae(rove beetles; Poinar and Brodzhinsky, 1985),Mycetophilidae (fungus gnats; Poinar 1991a), andDrosophilidae (pomace flies; Poinar 1984a,1984b). In the Mermithida, reported insect hostsare the Cerambycidae (longhorn beetles; Heyden,1860, 1862), Chrysomelidae (leaf beetles; Voigt,1957), Limoniidae (crane flies; Poinar, 1984c),Culicidae (mosquitoes; Poinar, 1984c; Poinar et al.,1994a), and Chironomidae (aquatic midges;Menge, 1866; Schlee and Glöckner, 1978; Poinaret al., 1994b; Poinar and Milki, 2001). Nematodetrails have been found in the Middle Eocene GreenRiver Formation in Utah (Moussa, 1970); and theparasites have been found in association withspiders from Baltic amber (Poinar, 2000), and inPleistocene mammals, including a horse from theBalkans (Dubinina, 1972) and a ground squirreland a mammoth from Russia (Dubinin, 1948).2. Nematomorphs. Nematomorphs, or hairworms, are thin endoparasitic worms that mayreach a meter in length. In the juvenile phase theyinhabit particular species-specific tissues or organsin arthropods, particularly orthopteroid insects(Brusca and Brusca, 1990). As adults they areaquatic and free-living. The obligately parasiticphylum Nematomorpha includes about 250 extantspecies, and has a sparser historical record thannematodes, with only two known fossil occurrences.Members of the Gordidae are preserved in middleEocene compression deposits in Germany and Italy(Voigt, 1938; Sciacchitano, 1955), although thisassignment has been questioned by Poinar (1999b).By contrast, a member of the Chorododidae has beenfound extruding from the anus of a member of thecockroach family Blatellidae in younger Dominicanamber (Poinar, 1999b).3. Tardigrades. Water bears, or tardigrades, area poorly known phylum of arthropod-likeinvertebrates that occur in the oceans, fresh water,and humid terrestrial environments (Dewel andDewel, 1998). They have a fossil record beginningin Middle Cambrian deposits of northern Siberia(Müller et al., 1995). These specimens, however,are demonstrably marine, cannot be assigned to anypost-Jurassic clade, and have been considered tobelong to a stem-group lineage (Müller et al., 1995).The next and only post-Paleozoic fossil tardigragesare members of the Class Eutardigrada found in LateCretaceous ambers of North America—specificallythe Turonian of New Jersey (Bertolani and Grimaldi,2000) and the Campanian of Manitoba (Cooper,1964)—as well as in the Pleistocene of Italy(Durante and Maucci, 1972). Continental, free-livingtardigrades are herbivores or predatory carnivores.They are significantly different from their Cambrianmarine progenitors, as they possess a fourth, hindpairof legs that are positioned laterally rather thanventrally. However, there are similarities betweenextant marine parasitic Tardigrades and theCambrian forms, such as dorsoventral flattening,the presence of anterior cephalic (suction) discs, aninvoluted mouth, and laterally deployed, robustlyclawed legs (Müller et al., 1995). The Cambrianforms most likely are ancestors of extant marinetardigrades—namely the mostly parasiticarthrotardigrades of the Class Heterotardigrada,which are basal within the phylum and exhibit thegreatest range of morphology (Dewel and Dewel,1998). They represent the stock from which thecontinental lineages evolved, especially thecomparatively diverse Eutardigrada.4. Onychophorans. Velvet worms, oronychophorans, are predaceous, terrestrial,caterpillar-like relatives of arthropods withlobopodous limbs. Their head region has hiddenmouthparts consisting of two pairs of cutting bladesthat serve as jaws and slice tissue in a fore-and-aftmotion (Manton, 1977). Onychophorans currentlyhave a Gondwanan distribution and typically preyon terrestrial invertebrates in tropical to subtropicalenvironments. The fossil record of the phylumextends to the primitive form Aysheaia from theMiddle Cambrian Burgess Shale of Alberta (Gould,1995). A hiatus of approximately 225 million yearsseparates these early marine forms from the nextfossil occurrences, the Late Carboniferous andterrestrial Mazon Creek Helenodora in Illinois(Thompson and Jones, 1980), and an undescribedform from Montceau-les-Mines in France (Rolfeet al., 1982). No Mesozoic specimens are known.Two demonstrably terrestrial taxa, however, are225