View - Kowalewski, M. - Virginia Tech

LABANDEIRA—PREDATORS, PARASITOIDS, AND PARASITESLophotrochozoa display the most varied strategiesfor predation: two phyla use cutaneous absorptionthrough the body wall (platyhelminth flukes andtapeworms, acanthocephalans); one group usesmodifications of a distinctive oral device, the radula(pulmonate gastropods); another group producescopious amounts of pharyngeal mucus to ensnareprey, with or without an oral circlet of buccal ciliaor hooks (oligochaete annelids); hirudinean annelids(leaches) use their distinctive oral armature of slicingjaws in conjunction with a suction apparatus; and alast group (other leaches, nemertineans) housesstylets within an eversible proboscis. By contrast,the Ecdysozoa displays a more uniform pattern ofpredation and parasitism. Proboscides withprotractile chitinous stylets involved in fluid feedingare found in some nematodes (one stylet),tardigrades (two stylets), and larval pentastomes andnematomorphs (three stylets), housed in amouthcone or tubular rostrum (Brusca and Brusca,1990). Other ecdysozoan feeding apparatusesinclude the three or more radially symmetrical jawlikestructures in some nematodes; the two pairs ofslicing, chitinous jaws in onychophorans; thechelicerae and pedipalps of arachnids; and especiallythe primitively adducting/abducting mandibles ofcrustaceans, myriapods, and hexapods. Themouthparts of basal mandibulate hexapods havebeen transformed into a bewildering array ofparticulate and invasive or noninvasive system offluid feeding, including filter-feeding, sponging,siphoning, rasping, lapping, and boring (Schram,1986; Labandeira, 1997a; Walter and Proctor, 1999).Lophotrochozoans.—The Lophotrochozoa—represented by the Rotifera, Acanthocephala,Platyhelminthes, Nemertinea, Mollusca, andAnnelida—have not successfully entered thecontinental realm, and remain overwhelminglymarine. The only significant continental clades arethe gastropod molluscs, and annelids (earthwormsand leeches), many of which occur in fresh waterrather than on land. Extant and extinct specioseclades include bivalve molluscs, cephalopods, andnonpulmonate gastropods, some of which haveonly marginally invaded fresh water. Terrestrializedlophotrochozoan phyla range in species diversityfrom about 750 species for the Acanthocephala toabout 20,000 for pulmonate gastropods.Unlike the Ecdysozoa, the Lophotrochozoalack a unifying synapomorphous or otherwiseobvious feature that could account for theirprevalence in terrestrial habitats. Rather, they havebecome terrestrial and subsequently carnivorousvia four basic strategies, each of which hasoriginated multiple times within and among phyla.The first pathway is via endoparasitism—as incestode and trematode platyhelminths (flukes andtapeworms) and acanthocephalans, all of which←FIGURE 3—The fossil history of carnivory by terrestrial invertebrates, expressed as predation, parasitism,mixed strategies, and microvory. Major sources are Conway Morris (1981), Little (1983), Eisenbeis andWichard (1988), Gray (1988), Brusca and Brusca (1990), Wills (1993), Foelix (1996), Selden (1996),and Poinar and Poinar (1999). Phyla are capitalized; classes or approximately equivalent ranks are inlowercase and standard font; and supraphyletic ranks are in lower case and bold. Geochronology isresolved to stage level and is modified from Gradstein and Ogg (1996); abbreviation: Neog., Neogene.A question mark indicates a questionable geochronologic assignment. Missing epoch designations,from bottom to top: Wenlock and Pridoli (Silurian); Gzelian (Carboniferous), Early and Middle (Triassic);and Pliocene and Pleistocene (Neogene).Notes: (1) The Pentostoma and Acanthocephala lack a body-fossil terrestrial fossil record, thoughboth are internal parasites of mammals and other vertebrate lineages that extend to the Paleogene.(2) The Nemertinea and Nematoda have earliest terrestrial occurrences in the Paleozoic that cannotbe assigned to a higher-level clade (Schram, 1973). (3) See Figure 4 for delimitation of lower taxonomicranks. (4)Microvory is defined as the consumption of live or dead small particulate food and includesunicellular organisms.221