Conus araneosus Lightfoot, 1786

Common Name

Status

Regarded as a valid species.

Type Locality

China, Coromandel

Distribution

Sri Lanka and S.E. India

Maximum Reported Size

101 mm

Description

Moderately large to large, solid to heavy. Last whorl conical, generally broader in C. araneosus (Pl. 2, Figs. 9-12); outline straight to slightly convex. Shoulder angulate, weakly to strongly tuberculate. Spire of low to moderate height, consistently low in ssp. nicobaricus (Pl. 3, Figs. 13-15); outline straight. Postnuclear spire whorls tuberculate. Later teleoconch sutural ramps concave and nearly smooth. Last whorl with weak spiral ribs above base.

C. araneosus: Ground colour white, tinged with violet in shells from India. Last whorl with a fine network of reddish brown lines outlining small white tents, usually with a dark brown spiral band on each side of centre. Bands interrupted by bluish ground-colour tents and a few brown tents. Teleoconch sutural ramps with fine reddish brown zigzag lines and bluish brown marginal blotches between tubercles. Aperture nearly white (shells from Sri Lanka) or outer part pale violet, interior deep yellow (shells from southeast India, Pl. 2 Fig. 12). ssp. nicobaricus: Ground colour white, occasionally with a tinge of red or violet. Last whorl with a network of reddish brown to blackish brown lines outlining variously sized white tents that often coalesce. Usually with 3 discontinuous bluish or blackish brown spiral bands, on both sides of centre and below shoulder; central band more pronounced than other bands. Spire and shoulder with fine, dark brown zigzag lines and blue-tinged brown blotches between tubercles. Aperture white to light violet, yellow deeper within.

Periostracum cream to brown, thin, translucent, smooth.

Periostracum yellow, thin, translucent, smooth.

C. araneosus: Foot buff; side and dorsum mottled with brown and with a black longitudinal line continued as a broad band around the anterior dorsum; anterior edge of sole yellow. Rostrum buff; tentacles buff, anterior margins grey. Tip of siphon orange, followed proximally by a narrow white stripe, broad grey stripe and broad stripe of buff heavily mottled with reddish brown (Kohn, 1978). ssp. nicobaricus: Foot buff, paler and with a bilobate black blotch on anterior part of dorsum; sole with irregular transverse and longitudinal brown lines, posterior half darker and anterior edge yellow. Siphon tipped with yellow, then banded with white, black, yellow and dark brown (Kohn, unpubl. observ.).

Radular teeth long and narrow, with one barb and a long, fine serration terminating in a distinct backward- pointing cusp at centre of shaft or somewhat posterior to it (Bergh, 1895). According to Nybakken (1990), radular teeth less elongate, serrations shorter, shaft with waist base with a spur; adapical armature consisting of a barb opposite a blade.

Shell Morphometry

L	55-100 mm
RW	0.40-1.50 g/mm
RD	0.61-0.70 (C. araneosus; 0.61-0.70; ssp. nicobaricus 0.54-0.63)
PMD	0.86-0.94
RSH	0.09-0.15 (C. araneosus; ssp. nicobaricus 0.04-0.09)

Habitat & Habits

C. araneosus: Intertidal to 20 m, on limestone and sandy substrata. C. araneosus appears to feed on gastropods (Kohn, 1978a). The egg mass consists of several layers of capsules, each containing 63-214 eggs about 490 µm in diameter. The larvae hatch at a stage that "swims and crawls" (= veliconcha; Natarajan, 1957). ssp. nicobaricus: Shallow water, on sand substrate under corals and in coral rubble on subtidal reef platforms. Radular tooth structure as given by Nybakken (1990; pers. comm.,1993) indicates vermivory, while that given by Bergh (1895) rather suggests molluscivory.

Discussion

C. araneosus resembles C. bandanus in shape, but the latter species attains larger size (to 150 mm). Its last whorl colour pattern is a much coarser network and has many fewer white tents. We consider C. araneosus and C. nicobaricus as subspecies, because they are nearly indistinguishable in shell characters and colouration of the animal. ssp. nicobaricus usually has a relatively narrower last whorl and larger shoulder tubercules, and it tends to have a slightly lower spire and coarser colour pattern.

Related Taxon

C. arachnoideus Gmelin, 1791
C. araneosus Hwass in Bruguière, 1792
C. monstrosus Küster, 1838
C. peplum Sowerby ii, 1857
C. reticulatus Perry, 1811
ssp. nicobaricus

References

Lightfoot, J., 1786. A Catalogue of the Portland Museum, Lately the Property of the Duchess Dowager of Portland, Deceased; Which will be sold by Auction... etc..
Röckel, Korn & Kohn, 1995. Manual of the Living Conidae Vol. 1: Indo-Pacific Region.