Introduction to Physidae (Gastropoda: Hygrophila); Biogeography, Classification, Morphology
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Rev. Biol. Trop. 51 (Suppl. 1): 1-287, 2003 www.ucr.ac.cr www.ots.ac.cr www.ots.duke.edu Introduction to Physidae (Gastropoda: Hygrophila); biogeography, classification, morphology Dwight W. Taylor1 1 Mailing address: P.O. Box 5532, Eugene, Oregon 97405. Abstract: Physidae, a world-wide family of freshwater snails with about 80 species, are reclassified by pro- gressive characters of the penial complex (the terminal male reproductive system): form and composition of penial sheath and preputium, proportions and structure of penis, presence or absence of penial stylet, site of pore of penial canal, and number and insertions of penial retractor muscles. Observation of these characters, many not recognized previously, has been possible only by the technique used in anesthetizing, fixing, and preserving. These progressive characters are the principal basis of 23 genera, four grades and four clades within the family. The two established subfamilies are divided into seven new tribes including 11 new genera, with diagnoses and lists of species referred to each. Proposed as new are: in Aplexinae, Austrinautini, with Austrinauta g.n. and Caribnauta harryi g.n., nom.nov.; Aplexini; Amecanautini with Amecanauta jaliscoensis g.n., sp.n., Mexinauta g.n., and Mayabina g.n., with M. petenensis, polita, sanctijohannis, tempisquensis spp.nn., Tropinauta sinusdul- censis g.n., sp.n.; and Stenophysini, with Stenophysa spathidophallus sp.n.; in Physinae, Haitiini, with Haitia moreleti sp.n.; Physini, with Laurentiphysa chippevarum g.n., sp.n., Physa mirollii nom.nov.; and Physellini, with Chiapaphysa g.n., and C. grijalvae, C. pacifica spp.nn., Utahphysa g.n., Archiphysa g.n., with A. ashmuni, A. sonomae spp.nn., Physella hemphilli sp.n., and Ultraphysella sinaloae g.n., sp.n. The simplest reproductive system is found in Austrinauta of the Aplexinae; its penial complex approach- es that in the related family Lymnaeidae. Within Physinae a close approximation is found in Haitia. By these two genera the two subfamilies are drawn close together. Four grades of progressive complexity are recognized: (I) penial sheath entirely muscular; (II) penial sheath with both glandular and muscular tissue; (III) penis with penial stylet or other specialization of the tip of the penis; and (IV) pore of penial canal lateral rather than ter- minal as in the lower grades. In both subfamilies there are clades with glandular tissue in the penial sheath, a penial sheath subdivided into two parts, and tip of penis specialized in various ways. These clades are formal- ized as new tribes. Of 23 genera of Physidae, 17 occur in Pacific drainages of North and Central America, eight of these restricted to the region. Concentration of primitive genera along the Pacific coast from Mexico to Costa Rica conforms to previous observations that primitive pulmonate families are concentrated within, or along the con- tinental margins of, the Pacific Ocean. An ancestral origin of Physidae along an ancient eastern Pacific coast is probable. From this region the several lineages have spread north, south and east in the Americas, and through Siberia to Europe. Although Physinae have fewer genera than Aplexinae (11 v. 12), they have more species (47 v. 34). Greater land area in the temperate zone has provided more opportunity for speciation of Physinae, in contrast to the gen- erally tropical and warm-temperate range of Aplexinae. Furthermore, 10 species of Physinae are localized in individual lakes, whereas Aplexinae are not lake-dwellers. Both well-developed egg strings and capsular strings are found in the spawn of Sibirenauta elongatus. These structures have been known in Lymnaeidae, but not hitherto in Physidae; they are a link with some marine groups, such as Siphonariidae. Spiral color bands and white streaks in the shell of Mexinauta recall those in Lancidae (Lymnaeacea), whereas the radula of Physidae is like that of Chilinidae. Physidae thus show affinities to various basal stocks of aquatic pulmonates; no clear-cut sister-group can be recognized. Most species have a restricted range; out of 55 with sufficiently detailed information for analysis, 25 are limited to a single 1ºx1º quadrangle. Only a few species are widespread, on one or even two continents. Accordingly, more species of Physidae are threatened by habitat destruction than in other families of Hygrophila with generally wider distributions. Other features are a key to genera; catalog of more than 430 names applied to living Physidae, with orig- inal reference, type locality, and location of type specimens; summary of museums with types; and glossary. Key words: Physidae, classification, biogeography, new species, new genera, new tribes. 2 REVISTA DE BIOLOGÍA TROPICAL Physidae are common freshwater snails in disposal than have any others. Frustratingly, the North Temperate to Arctic Zones and virtually all preserved specimens borrowed throughout the Americas, in readily accessible from museums (albeit with gratitude) have been habitats such as ditches, ponds, lakes, small of wretched quality, more tantalizing than streams, and rivers. They can be collected eas- informative. Only such a quantity and quality of ily and maintained in an aquarium. The family well-preserved samples allowed recognition of has been recognized as such for more than a progressive characters in the male reproductive century. Yet there has been no classification in system that are fundamental to the present clas- which relationships between genera are clari- sification (Figs. 1-3). In addition, I have been fied, no agreement on what characters are prim- able to see many more characters overall than itive or advanced, and no consistent ranking. have previous students of Physidae. Indeed, an Scarcity of careful morphological studies is a implicit message of this work is an appeal for principal cause. more and thorough morphological studies and Lack of shell characters means that it is not for more detailed illustrations. only previous classifications, entirely or largely Naturally, with this foundation, new bio- based on shells, that are deficient. Identification geographic conclusions have been possible. of species, except in rare cases, has been practi- The more primitive Physidae are concentrated cally impossible. In the thousands of local lists, in Pacific drainage from southern Mexico to keys, handbooks, and other citations published Costa Rica, and the primitive pulmonates with during the last 200 years, species identifications which Physidae share some traits are also found are simply untrustworthy. This in a group often along the eastern Pacific coast. Perhaps ancient encountered by not only collectors, but by all adaptation to fresh waters in this region accom- those with a general interest in freshwater habi- panied differentiation of the modern families. In tats, or those engaged in some applied study. any case, one can trace lineages of Physidae Generalizations as to diversity in a region, from this area, to Europe, Asia, North and species distributions, and ecology are corre- South America, and the West Indies. spondingly suspect. The species composition of Beyond morphology, I have tried to stabi- a country or region has been understood only lize nomenclature by preparing a catalog of the where the fauna is sparse (as in the British Isles more than 430 nominal species (p. 208-251), and northwestern Europe), or where there has finding many preoccupied names in the process. been morphological verification of the species Type localities have been refined by allocating (as in Connecticut and New York: Jokinen, the species to expeditions or voyages, tracing 1983, 1992). routes and itineraries (under Museum Advances of this work over previous stud- Collections, p. 198-207). The taxonomist’s com- ies are due principally to the technique used in mon question is, “Where is the _ _ _ _ type?” anesthetizing and fixing. This permitted exami- Sherborn (1940), in “Where is the _ _ _ _ nation of material in far better condition for collection?,” helped much in this respect; now detailed study than was available to most earli- there are many catalogs of types in various er writers. Then, too, I have had the advantage museums that are of great assistance. And yet, of collecting widely (extensively in the western not always. The zeal of some curators who were United States, also Minnesota, Wisconsin, also “type collectors” has led to the supposed Alabama and Florida; in British Columbia; in existence of multiple holotypes or lectotypes in many states of Mexico; Guatemala and Costa several cases. I have merely recorded such Rica; in the West Indies in Jamaica, Dominican information without attempting a resolution of Republic, Barbados, and Trinidad; Argentina, the matter. Hawaii, Singapore, and England) and have had The new classification (Fig. 1) is based well-preserved material of more genera at my almost entirely on the terminal male reproductive INTERNATIONAL JOURNAL OF TROPICAL BIOLOGY AND CONSERVATION 3 Fig. 1. Classification of Physidae, with division into grades and clades, based on progressive changes in penial complex and its musculature. system (the penial complex), including its retractor muscles. Many features useful in dis- tinguishing genera and even species are found in other structures and systems: in the hermaph- roditic and female reproductive tracts, in shell, mantle, prostate, spawn, and external body pig- mentation. In none of these, however, are pro- gressive characters found consistently. For sim- plicity of presentation,