MOLLUSCA OF SOUTHERN CHILE 



125 



(radula), fig. N, no. 102 (protoconch) (synonymy). Castellanos, 

 1990: 8, pi. 2, figs 18,21. 

 Eumetula pulla - Bouchet & Waren, 1993: 601. 



Description. Shell to 8.8 by 3.5 mm (to 13 mm, Castellanos, 

 1990); narrowly elongate, thin-walled; spire whorls encircled by 

 three spiral rows of square nodules, aligned in axial rows, two spiral 

 ribs lacking nodules below periphery of last whorl; colour brown, 

 spiral rows of nodules darker. 



Habitat. Dredged from 10-15 m depth, on substrate of silt with 

 scattered pebbles and shells; uncommon. The species has been 

 reported from depths of 8 to 251-313 m (Powell, 1951). Other 

 members of the genus are known to live and feed on sponges, as do 

 most cerithiopsids (Houbrick, 1987), and this may be the typical 

 habitat of E. pulla also; one collection 'in sponge' was noted by 

 Melvill&Standen(1912). 



Records. Station 25 (1 dead, 2 live specimens). Elsewhere 

 Magellan Strait, Falkland Is and Burdwood Bank (Powell, 1 95 1 ), so 

 that our records are the northernmost. Range: 46-54°S. 



REMARKS. The more familiar genus Ataxocerithium has usually 

 been classified in the Cerithiidae, but was transferred to the 

 Cerithiopsidae by Houbrick (1987). Bouchet & Waren (1993) trans- 

 ferred this species to the cerithiopsid genus Eumetula on the basis of 

 radular characters. 



Family MURICIDAE 



Concholepas concholepas (Bruguiere, 1789) 



(Figure 30) 



Buccinum concholepas Bruguiere, 1789: 252. 



Concholepas concholepas - Beu, 1970: 44, pi. 4, figs 10-12. Dell, 



1971: 210-211. Marincovich, 1973: 35, fig. 73. Osorio, Atria & 



Mann, 1979: 21-22, fig. 23. Kool, 1993: 173-176, fig. 7A-F. 



DeVries, 1995: 286, figs 4, 6, 8, 9, 11, 19 (synonymy). 

 Concholepas concholepas concholepas -Stuardo, 1979: 5-38, pi. 1, 



figs 1-8, pi. 3, figs 17, 23 (synonymy). 



Description. Shell to 108 mm; body whorl greatly expanded to 

 produce limpet-like form; sculptured by coarse spiral ribs, imbri- 

 cated by raised axial growth lines; colour brown, interior white with 

 brown margin. 



Habitat. In rock crevices at top of calcareous red algal zone, 

 lowest eulittoral, on strongly exposed coast. In central Chile and 

 further north, adult populations are mainly subtidal, reaching depths 

 of 40 m (Rabi, Yamashiro & Quiroz, 1996), but the rarity of adults 

 in the littoral zone appears to be a consequence of exploitation by 

 humans. In reserves where this is prevented, large adults appear in 

 the littoral zone and density may increase to as many as 1.6-4.3 per 

 m 2 (Castilla & Duran, 1985; Moreno, Lunecke & Lepez, 1986; 

 Duran, Castilla & Oliva, 1987). Settlement occurs in the low 

 eulittoral, and juveniles move upwards as growth occurs (Moreno, 

 Reyes & Asencio, 1993). 



Records. Station 16. Elsewhere I. Lobos de Afuera (Peru) to 

 Cape Horn (DeVries, 1995). Range: 7-55°S. 



REMARKS. This large species supports the most important gastro- 

 pod fishery in Chile (Castilla, 1982); the catch has declined from 

 21236 tonnes in 1987 to 3154 tonnes in 1997 (SERNAP, 1998) and 

 collection is now permitted for only a few days in the year. It is a 

 common component of the ancient shell middens on Isla Traiguen. 



Collection by fishermen continues in the study area, but the intensity 

 of exploitation is not known, nor to what extent this might influence 

 the absence of this species from the more accessible coasts of 

 moderate exposure. The egg capsules are cylindrical and stalked, 25 

 mm long; these have been described by Castilla & Cancino (1976) 

 and the planktotrophic development of the larvae by DiSalvo ( 1 988). 

 This carnivorous species has a diet of barnacles, the ascidian Pyura, 

 Perumytilus and other molluscs (Castilla, Guisado & Cancino, 

 1 979; Castilla & Duran, 1 985 ) and is able to bore into its shelled prey 

 (Gruber & Carriker, 1990). As a top predator it has an important 

 influence on community structure, and where human collection is 

 prevented the cover of barnacles and Perumytilus declines signifi- 

 cantly (Moreno, Lunecke & Lepez, 1986). There is a large literature 

 on this species, reviewed by Rabi, Yamashiro & Quiroz ( 1 996). The 

 taxonomic status of the population on the Juan Fernandez Islands, 

 described as the subspecies C. concholepas fernandezianus Stuardo, 

 1979, requires investigation. 



Acanthina monodon (Pallas, 1774) 

 (Figure 3K, L) 



Buccinum monodon Pallas, 1774: 33, pi. 3, figs 3, 4. 



Acanthina monodon - Dell, 1971: 208-210 (synonymy). 

 Cernohorsky, 1977: 118 (synonymy). Osorio, Atria & Mann, 

 1979: 21, fig. 21. 



Acanthina monodon monodon - Wu, 1985: 56-58, figs 13, 14, 24, 

 34, 52-58, 71 (radula, anatomy). Vermeij, 1993: 22. 



Acanthina monodon unicornis (Bruguiere, 1789) - Vermeij, 1993: 

 22. 



Acanthina crassilabrum (Lamarck, 1816) - Dell, 1971: 210 (syn- 

 onymy). 



Acanthina monodon crassilabrum - Wu, 1985: 58-61, figs 15-17. 

 23, 35-37, 50, 51, 59, 71 (radula, anatomy). 



Description. Shell to 57 mm; whorls rounded, spire pointed; 

 usually sculptured by 20-30 raised spiral cords, often imbricated by 

 raised axial growth lines; sculpture may be obsolete on body whorl, 

 or eroded; outer apertural lip sharp, or thickened and with internal 

 denticles, always with labral spine near anterior end of outer lip; 

 colour polymorphic: purple brown, white, orange or banded with 

 brown. 



Habitat. Eulittoral rocky shores, in lower barnacle zone and 

 Mytilus zone, in exposed and moderately sheltered situations. Found 

 at salinities down to 15 and 22%c. 



Records. Stations 1,5, 7, 10, 12, 14, 15, 17, 20, 2 1,22. Elsewhere 

 from about 22°S to Magellan Strait (Dell, 1971) and Tierra del 

 Fuego (Wu, 1985). Range: 22-55°S. 



Remarks. This was one of the most frequent intertidal gastro- 

 pods in the study area. Members of this species are carnivorous, 

 and small mussels are a major component of the diet (Moreno, 

 1995). The related Californian genus Acanthinucella feeds mainly 

 on barnacles, which are attacked either by using the labral spine to 

 prise or wedge open the opercular valves before inserting the 

 proboscis, or alternatively by boring through the valves by means 

 of the accessory boring organ and radula (Malusa, 1985; Perry, 

 1985). The egg capsules are small and flask-shaped, 15 mm in 

 length, and laid in batches in crevices on the shore (Wu, 1985: figs 

 52, 53). The shell is remarkably variable in shape and sculpture, 

 showing a much thicker, smoother shell with narrower aperture 

 and stronger marginal denticles (Fig. 3L) in sheltered habitats, in 

 contrast to a thinner, scaly shell in exposed situations (Fig. 3K). 

 Similar variation occurs over a geographical scale, and some 



