MALACOLOGIA, 1984, 25(1): 109-141 NORTH AMERICAN FRESHWATER SNAIL GENERA OF THE HYDROBIID SUBFAMILY LITHOGLYPHINAE Fred G. Thompson Florida State Museum, University of Florida, Gainesville, Florida 32611, U.S.A. ABSTRACT The classification of the North genera of Lithoglyphinae is reviewed, based on anatomical and conchological characters. Five genera are recognized: Gillia Stimpson, 1865, Fluminicola Stimpson, 1865, Somatogyrus Gill, 1863, Clappia Walker, 1909, and Lepyrium Dall, 1896. The North American genera are conservative in their anatomies. Primary morphological differentiations involve radular and shell characters. The North American genera are demon- strated to have evolved through trophic specializations and microhabitat specializations. Lepyrium Dall, 1896, formerly considered a monotypic family, is closely related to Clappia and Somatogyrus. Birgella Baker, 1926, is removed from the Lithoglyphinae, where it has been placed by authors, and is demonstrated to be in the Nymphophilinae. The following species are described in detail: Lepyrium showaiteri (Lea, 1861), Somatogyrus rheophilus n. sp., Gillia altilis (Lea, 1841). A neotype is designated for the latter species. Key words: Gastropoda, snails, Hydrobiidae, Lepyriidae, Lithoglyphinae, Lepyrium, Clappia, Somatogyrus, Gillia, Fluminicola, systematics, evolution. INTRODUCTION placed in a monotypic family of uncertain affinity within the MESOGASTROPODA (Pilsbry This paper discusses the systematic rela- & Olsson, 1951). Its soft anatomy was found tionships between the North American litho- to be hardly distinguishable from that of glyphine genera: Lepyrium, Somatogyrus, Somatogyrus. These two genera have very Clappia, Gillia, and Fluminicola (Class GAS- dissimilar shells, but they have in common TROPODA, Subclass PROSOBRANCHIA, Order similar habitats. Lepyrium and most Somato- MESOGASTROPODA, Family HYDROBIIDAE, gyrus live on rocks and boulders in high- Subfamily LITHOGLYPHINAE). A sixth genus, energy rivers. The habitat deployments Antrobia Hubricht, 1972, is placed by Burch & among these two genera focus on the adap- Tottenham (1980: 100) in the Lithoglyphinae. tive radiation of the Lithoglyphinae in eastern clarify the limits of It is a monotypic genus from a cave in Mis- North America. In order to souri; the anatomy remains undeschbed and this basic radiation other relevant genera Antrobia is omitted from further discussion in were examined. The results of these studies this paper. Another genus, Cochliopina Morri- are presented herein. son, 1946, traditionally has been associated with the Lithoglyphinae. Hershler (in press) shows that it is a genus of the Littohdininae. MATERIAL AND METHODS Birgella Baker, 1926, Is another genus that has been confused with this subfamily, even Anatomical descriptions and illustrations in the following speci- as recently as 1981 (Clarke). It is in the NYM- this paper are based upon PHOPHILINAE, as is discussed in Appendix B. mens: This study stems from two independent Lepyrium showaiteri (Lea). Two lots of collected June investigations. The first was an attempt to about 100 specimens each, and June 22, 1 978 (UF determine species-group characteristics with- 21 , 1 978 (UF 31 343) River, 2.4 km in Somatogyrus, a genus containing many 31342) in the Little Cahaba species (Burch & Tottenham, 1980: 104- upstream from the Cahaba River, Bibb Co., with menthol 106). The study was tabled temporarily be- Alabama by F.G.T. Relaxed in Bouin's solution and pre- cause very little anatomical diversity was dis- crystals, fixed covered among the species examined. In- served in 70% ethanol. Somatogyrus rheophilus n. sp. (described dependently I examined the anatomy of of speci- Lepyrium showaiteri (Lea), a snail previously below). One series of thousands (109) 110 THOMPSON mens collected October 21, 1973, in the Flint shoals. Lepyrium showalteri (Lea) is de- River, 9.7 km SW of Lincoln Park, Upson Co., scribed in detail because its systematic affini- Georgia by F.G.T. (UF 40511). Relaxed with ties have been in question since it was dis- menthol crystals, fixed in Bouin's solution and covered. Its shell is described in Appendix A. preserved in 70% ethanol. The shell (Figs. 59-62) is peculiar because it Gillia altilis (Lea). One series of about 400 has a depressed spire and an expanded, specimens collected June 1, 1980 in Lake flattened body whorl, giving it a neritid Waccamaw, Columbus Co., North Carolina appearance. The first whorl of the protoconch by Hugh J. Porter (UF 27550). Fixed un- is smooth, except for a few short spiral fur- relaxed and preserved in 70% ethanol. rows below the periphery (Fig. 39). The Fluminicola nuttalliana (Lea). One series of neomelanian type operculum (Fig. 7) is mod- 23 specimen collected July 20, 1974 in the ified in shape to conform to the enlarged Satsop River at Satsop, Grays Harbour Co., aperture. This is accomplished by rapid ex- Washington by Dennis R. Paulson (UF pansion of the last whorl from the paucispiral 34813). Fixed unrelaxed and preserved in nucleus, a minor elaboration of the basic con- 70% ethanol. dition that also exists in Somatogyrus and Dissections were made in 70% ethanol un- Gillia (Fig. 52). Its radular teeth are modified der a WILD M-2 dissecting microscope. Serial for feeding on small-sized food particles. sections were made at 10 ixm and stained in Lepyrium is the most divergent of the North 10% Harris' hematoxylin stain. Radulae were American LITHOGLYPHINAE because of these cleaned in a saturated solution of potassium specializations. Other aspects of its anatomy hydroxide and examined with a HITACHI S- are conservative and indicate a close relation- 41 5A scanning electron microscope at the ship to Clappia and Somatogyrus. Department of Zoology, University of Florida. External morphology and color Foot broad Museum abbreviations are given in Appen- and rounded (Figs. 1-3). Operculigerous lobe dix overlaps on each side, and edge of oper- culum overlaps extended foot on left side and posteriorly. Mucous groove present along an- ANATOMY OF THE GENERA terior edge of foot. Food grooves and epitae- nial folds absent on body and snout. Col- The genera Lepyrium, Clappia, Somatogy- umellar muscle extending into shell for about rus, Gillia and Fluminicola are placed in the a quarter whorl. Columella muscle insertion subfamily LITHOGLYPHINAE. The conical, or short but wide, extending transversely nearly depressed-conical, or globose-conical, or the complete width of body whorl (in other neritoid-shaped shells have in common spiral genera the insertion is narrower). Mantle col- sculpture on the protoconch (Figs. 39-42). lar complete around body, without tentacles Other protoconch sculpture may also be or papillae. Mantle cavity of males semicircu- present. Other aspects of the shell are not lar in saggital section; triangular in females, distinctive at the subfamily levels among bounded posteriorly by palliai gonoduct, per- North American hydrobiid genera, although icardium and stomach. Gill (gf) consisting of the lithoglyphines tend to be stocky species 19-20 lamellae that are arranged in an with relatively heavy shells. oblique series on mantle wall. Lamellae A high degree of anatomical uniformity ex- triangular in shape (Fig. 8), with greatest ists among the North American LITHOGLYPHI- height along intestine. Osphradium (og) long, NAE. Principal morphological differences narrow, L-shaped. Excurrent and incurrent occur in trophic structures and in the shell. siphons absent. Kidney small, broadly quad- Minor diversity also occurs in the male and rangular, overlying posterior left corner of female reproductive systems. Because of this mantle cavity. basic uniformity it is convenient to describe Tentacles long and slender in life, and the anatomy of Lepyrium and compare other actively beat substrate in alternate strokes as genera with it. animal moves about. Snout highly extendable and constantly sampling substrate in moving Lepyrium Dall, 1896 animal. Mantle jet black (Fig. 1) on all surfaces, Lepyrium is a monotypic genus endemic to completely opaque to all internal morphology. the Coosa and Cahaba Rivers in Alabama Snout and tentacles dark gray, fading posteri- where it lives on boulders in high energy orly and laterally to light gray on sides of body NORTH AMERICAN LITHOGLYPHINAE 111 FIGS. 1-3. Lepyrium showalteri (Lea). Fig. 1. Specimen denuded of shell showing pigmentation of mantle. Fig. 2. Male with melanin removed showing intemal anatomy. Fig. 3. Female with melanin removed showing internal anatomy. Legend: ast = anterior chambers of stomach; di = digestive gland; gf = gill filaments; goo = ovary; got = testis; in = intestine; ki = kidney; og = osphradium; op = operculum; pe = penis; pov = palliai oviduct; pr = prostate; sty = style sac. and nape. Tentacles also with diffuse, sca- Radula. Taenioglossate (Figs. 15-18, tered xanthophores. Sole very light gray. about 1.8 mm long, containing 140-149 Center of muzzle white. Penis white. transverse rows of teeth (7 specimens ex- Digestive system. Typically hydrobioid in its amined). Cusps rapidly worn, barely distin- configuration (Fig. 4). Two elongate claviform guishable on distal third of ribbon. Central salivary glands (sg) enter posterior buccal tooth (Fig. 15) about 130 ixm wide, broadly mass along dorso-lateral edges, and extend trapezoidal in shape with a long mid-basal posteriorly over top of nerve ring. Oesopha- projection; lateral angles with a low ridge gus (es) entering stomach on left side of bearing 9-11 small, nearly uniform,