Bull. nat. Hist. Mus. Lond. (Zool.) 66(2): 109-146 



Issued 30 November 2000 



The shallow-water marine Mollusca of the 

 Estero Elefantes and Laguna San Rafael, 

 southern Chile *y £y*>o0 «. O 



THE NATURAL 

 HtSTORY A4USSUM 



22 NOV 2000 : 



P ' ED i 



"HFT 



DAVID G. REID 



Department of Zoology, The Natural History Museum, London SW7 5BD, U.K. E-mail: dgr@nhm.ac.uk 



CECILIA OSORIO 



Departamento de Ciencias Ecologicas, Facultad de Ciencias, Universidad de Chile, Las Palmeras 3425, 

 Casilla 653, Santiago, Chile. E-mail: cosorio@uchile.cl 



ARY 



SYNOPSIS. Taxonomically, the Mollusca of southern Chile are moderately well known, but the literature is scattered, there is 

 little information on their habitats, and distributional records are scarce for the Chilean archipelago lying between Isla Chiloe and 

 Tierra del Fuego. In 1 998 a survey was made of the marine biodiversity of the Laguna San Rafael National Park and an area of 

 the Chonos Archipelago immediately to the north (approximately 46°S). The Laguna consists of a basin of low salinity, strongly 

 influenced by glacial meltwater, and the Estero Elefantes is a complex fjord system with both brackish and fully marine 

 environments, including sheltered bays and exposed coasts. Collections of molluscs were made at 26 stations, from intertidal 

 habitats, kelp plants and by dredging from depths of up to 15 m. A total of 62 species was recorded, consisting of 9 

 Polyplacophora, 33 Gastropoda and 20 Bivalvia. In order to facilitate future studies in the region, these are briefly described and 

 all the shelled species illustrated ( 12 of these photographed for the first time). Notes are given on habitats, depth and salinity, and 

 geographical ranges are reviewed. Biogeographically, the area lies at the poorly known southern extreme of the transitional zone 

 between the Magellanic and Peruvian faunal provinces. As a result, 27% of the species records are extensions to the known 

 ranges, representing northern limits of Magellanic forms and southern limits of Peruvian ones. Of the 62 species found, 48% could 

 be classed as Magellanic (found in the transitional zone and southwards) and 8% as Peruvian (found in the transitional zone and 

 northwards), while the remainder occurred in both provinces. 



INTRODUCTION 



The archipelago or fjordland of southern Chile is a remote and 

 relatively inaccessible area where little marine research has previ- 

 ously been carried out. In the heart of the fjordland (at a latitude of 

 46°S) lies the Laguna San Rafael National Park, a protected area of 

 1 .7 million hectares. In recognition of its importance as a wilderness 

 area covering a wide range of habitat types, with no significant 

 human impact, the park has been declared a UNESCO Biosphere 

 Reserve. Knowledge of the biodiversity of the area, and in particular 

 that of the marine habitats, remains poor. Therefore, in 1996 a 

 biodiversity research programme was initiated as a collaboration 

 between the administrative authority of Chilean protected areas, the 

 Corporacion Nacional Forestal (CONAF), the youth development 

 charity Raleigh International, the Museo Nacional de Historia Natu- 

 ral in Santiago, the Natural History Museum in London and the 

 World Conservation Monitoring Centre in Cambridge. This report 

 describes the results of the initial survey in 1998 of the marine 

 molluscs of the Laguna San Rafael and southern Estero Elefantes 

 that lie within the park, and an area of the Estero Elefantes in the 

 vicinity of Isla Traiguen immediately to the north of the present park 

 boundary. A preliminary report on the general marine survey of this 

 area has been prepared by Paterson et al. (in press). 



Dell (1971) has outlined the history of malacological investiga- 

 tions in southern Chile, and only a brief account will be repeated 

 here. Owing to its strategic importance, the Magellan Strait was the 

 object of several British surveys by H.M.S. 'Beagle' and 'Adven- 

 ture' during 1826 to 1830, from which the Mollusca were described 

 by King & Broderip (1832). Although this work is scarce and not 

 illustrated, it nevertheless contains the first descriptions of many of 



the common shallow-water species of the Magellanic region. From 

 about 1 822 to 1831 the notable collector Hugh Cuming was based in 

 Chile, where he amassed a great collection which was eventually 

 acquired by the British Museum. This material was the source of 

 many of the new species described by Sowerby (1833a, b, 1834, 

 1835, 1838, 1840) and by Reeve, later illustrated in Reeve's 

 Conchologia Iconica (1843-1878). The largest single work on the 

 Mollusca of South America was d'Orbigny's monumental Voyage 

 dans VAmerique Meridionale (1834-1847), based on the results of 

 his own extensive travels in the southern part of the continent. 

 Malacological knowledge of Chile was further advanced by the 

 collections of Gay, described by Hupe (1854), and by the arrival in 

 Santiago in 1851 of Philippi. As a result, by the middle of the 

 nineteenth century the molluscan fauna of southern South America 

 was remarkably well known. 



Towards the end of the nineteenth and in the early twentieth 

 century a number of important expeditions continued the biological 

 survey of the Magellanic region and dredging activities revealed 

 more of the subtidal fauna. Molluscs from the 'Alert' expedition 

 were described by E. A. Smith (1881), those from the French 

 Mission to Cape Horn by Mabille & Rochebrune (1889), from 

 Swedish and German expeditions by Strebel (1904-1907) and from 

 the 'Discovery' cruises by Powell ( 195 1 ) and Dell ( 1 964). Two later 

 expeditions are the source of most of the little existing knowledge of 

 the fauna of the fjordland between Puerto Montt and the Magellan 

 Strait. First was the Lund University Chile Expedition which made 

 extensive collections in the vicinity of Puerto Montt and Isla Chiloe 

 (41^t3°S) during 1948-1949, and also sampled a few localities 

 further south in the Chonos Archipelago (44-46°S) and Magellan 

 Strait (52-54°S). Important taxonomic accounts of the Poly- 

 placophora (Leloup, 1956), Cephalopoda (Thore, 1959), Bivalvia 



© The Natural History Museum, 2000 



