110 



D.G. REID AND C. OSORIO 



(Soot-Ryen, 1 959) and Lamellariacea and Opisthobranchia (Marcus, 

 1959) were produced, but no report on the Gastropoda appeared 

 (although some of the new records were published by Brattstrom & 

 Johanssen, 1983). The second was the Royal Society Expedition to 

 Southern Chile in 1958-1959. Again collections were made around 

 Isla Chiloe, and also at Isla Wellington (49°S) and to the south of 

 Tierra del Fuego at Isla Navarino (55°S). The Mollusca from this 

 expedition were described by Dell (1971). Although Marincovich's 

 (1973) study of the intertidal molluscs of Iquique relates to an area 

 in the north of Chile (20°S), it is a useful account of the more 

 common Peruvian species, some of which extend to the southern 

 part of the country; it is also unique among all previous reports in 

 being comprehensively illustrated. Recently, an extensive dredging 

 programme has been carried out in the Beagle Channel (55°S) 

 (Linse, 1997). A number of useful catalogues have appeared: of the 

 molluscs of Argentinian Patagonia (Carcelles, 1950); of the mol- 

 luscs of the Magellanic region (Carcelles & Williamson, 1951; and 

 a notable series of 14 papers by Castellanos and others, 1988-1993); 

 of the bivalves of Chile (Osorio & Bahamonde, 1970); of the 

 bivalves of the entire eastern Pacific Ocean (Bernard, 1983) and of 

 the Sacoglossa and Nudibranchia of Chile (Schrodl, 1996). 



Later in the twentieth century the production of faunistic works 

 declined and emphasis shifted towards monographic revisions of 

 taxonomic groups at a regional or wider level. Among those that 

 have included Chilean species are monographs of Chiton (Bullock, 

 1988), other polyplacophoran families (Kaas & Van Belle, 1985- 

 1994), Nacellidae (Powell, 1973), Fissurella (McLean, 1984), 

 rissoiform gastropods (Ponder & Worsfold, 1994), Acanthina (Wu, 

 1985), Xymenopsis (Pastorino & Harasewych, 2000),Volutidae 

 (Weaver & duPont, 1970), Protobranchia (Villarroel & Stuardo, 

 1998), Mytilidae (Soot-Ryen, 1955), Chlamys (Waloszek, 1984) 

 and Teredinidae (Turner, 1966). 



In conclusion, therefore, there is an impressive array of literature 

 available for the identification of the molluscs of southern Chile. 

 Nevertheless, this literature is difficult for the non-specialist to use, 

 for it is widely scattered and most of the potentially useful faunistic 

 reports and catalogues are not illustrated, or only inadequately so. 

 There are also deficiencies in geographical coverage, for the major- 

 ity of collecting effort has been expended on the Magellan Strait, 

 Tierra del Fuego and the Patagonian Shelf in the south, and to a 

 lesser extent on Isla Chiloe and the central region of Chile. Conse- 

 quently, geographical ranges are poorly known (Brattstrom & 

 Johanssen, 1983; Schrodl, 1997). Furthermore, this inadequate sam- 

 pling makes it difficult to evaluate cases of geographical variation as 

 either clines, allopatric subspecies or partially sympatric sibling 

 species (examples include Chiton magnificus, Nacella magellanica, 

 Scurria ceciliana, Acanthina monodon, Malletia magellanica, 

 Felaniella inconspicua and Carditella tegulata). With the exception 

 of commercial species, anatomical and genetic work on molluscs of 

 the region has only just begun. There are already several cases of 

 developmental and radular studies that have distinguished species 

 with closely similar or identical shells (e.g. Clench & Turner, 1964, 

 on Adelomelon and Odontocymbiola; Gallardo, 1979, on Crepidula), 

 and more such examples can be anticipated as detailed investiga- 

 tions by local workers continue. Some Magellanic molluscs show 

 confusing variability in shell characters, and numerous nominal 

 species have been described. Among the bivalves, examples include 

 the genera Mulinia and Zygochlamys; in the latter case availability 

 of an enormous series of shells has led Waloszek (1984) to 

 synonymize several poorly defined species in one variable taxon. In 

 the gastropod genera Acanthina, Trophon, Xymenopsis and 

 Pareuthria shell variability may be connected with local adaptation 

 facilitated by the nonplanktonic development that is common at high 



latitudes, or perhaps by ecophenotypic effects. Almost three dec- 

 ades after Dell's ( 1 97 1 ) review of the state of systematic malacology 

 in Chile, it remains true that these confusing taxa are, in his words, 

 'outstanding examples of groups demanding modern treatment by 

 workers on the spot' . 



A review of ecological research on molluscs in southern Chile is 

 beyond our scope here. Suffice it to say that distribution and life 

 history of the several commercially important species have received 

 most attention, as reviewed by Osorio, Atria & Mann (1979). 

 Marine molluscs are an important resource in Chile, and intertidal 

 and shallow-water species are widely collected by artisanal fisher- 

 men ('divers-mariscadores' and 'recolectores de orilla'). National 

 statistics for 1997 indicate that 7554 fishermen extracted 93269 

 tonnes of molluscs (Servicio Nacional de Pesca, 1998). Examples of 

 recent field studies on commercial species include work on 

 Concholepas concholepas (Castilla & Duran, 1985; Moreno, Reyes 

 & Asuncio, 1993), Choromytilus chorus (Navarro, 1988; Moreno, 

 1995), Ensis macha, Tagelus dombeii and Venus antiqua (Clasing, 

 Brey, Stead, Navarro & Asencio, 1994; Urban, 1994, 1996; Urban & 

 Tesch, 1996). Some of the more common intertidal molluscs have 

 been mentioned in studies of zonation and community structure 

 (Jara & Moreno, 1984; Alvarado & Castilla, 1996), including a 

 series of investigations on the influence of human predation on the 

 organization of intertidal communities (Moreno & Jaramillo, 1983; 

 Duran, Moreno, Lunecke & Lepez, 1986; Castilla &01iva, 1987). In 

 general, however, field research has been concentrated on the central 

 Chilean coast and around Isla Chiloe (Ramorino, 1968; Brattstrom, 

 1990; Santelices, 1991), together with a few studies in the Magellan 

 Strait and Beagle Channel (Guzman, 1978; Miranda & Acuna, 

 1979; Ojeda & Santelices, 1984; Castilla, 1985; Benedetti-Cecchi & 

 Cinelli, 1997; Linse, 1997; Linse & Brandt, 1998). To our know- 

 ledge, there has been but one previous report on marine ecology 

 within the Laguna San Rafael National Park, an account of the 

 impoverished brackish-water ecosystem of the Laguna itself (Dav- 

 enport etai, 1995) that mentioned only two molluscs. The taxonomic 

 reports of the exploratory cruises mentioned earlier did mostly 

 include depth ranges and habitat notes for the species encountered. 



Such, then, is the status of research on molluscs in southern Chile. 

 With this in mind, we have the following objectives in the present 

 survey. To facilitate future marine ecological work in this neglected 

 part of southern Chile we briefly describe the 62 species discovered 

 during the exploration of the Laguna San Rafael National Park and 

 adjacent area, and clearly illustrate the 59 species with external 

 shells (in 12 cases these are the first photographic illustrations of the 

 species). We give notes on habitats and station lists; of interest here 

 is the gradient of reduced salinity towards the San Rafael Glacier, 

 and the differential penetration of brackish water by the species. As 

 a guide to the scattered taxonomic literature we give abbreviated 

 synonymies, and point out those taxa requiring systematic revision. 

 The geographical range of each species is critically reviewed, based 

 on literature records and museum collections. Since the study area 

 lies within such a poorly studied region of the Chilean coast, and in 

 the zone of transition between Magellanic and Peruvian faunal 

 provinces, many of our records represent significant range exten- 

 sions. 



THE ENVIRONMENTAL SETTING AND 

 MOLLUSCAN ASSOCIATIONS 



The fjordland of southern Chile is formed from sunken ranges of 

 coastal mountains. Within this area the fjord system of the Laguna 



