Crucibulum scutellatum

Crucibulum scutellatum (W. Wood, 1828) is a marine snail of the family Calyptraeidae, an accepted name in the World Register of Marine Species ^[1]. Calyptraeids are sedentary snails that filter-feed and live attached to hard substrates ^[2]. A review of the family in Peru recorded it from Tumbes to Ica, on rocky infralittoral bottoms, with a recorded length of 67.0 mm ^[3].

The shell is a low cone with a subcentral apex. Its sculpture has thick, scaly radial ribs, sometimes interlaced with concentric sculpture, that project at the margin as heavy spines; the colour is brownish and the septum is white ^[3]. The review gives a length of 67.0 mm ^[3].

The cup-shaped septum, attached at the centre of the shell, sets Crucibulum apart from Calyptraea, whose septum is an inclined plane tracing a loose spiral ^[2]. Species of Crucibulum generally have spiny, ridged or rugose sculpture and keep a slight curve at the apex ^[2]. Because shells are plastic and often conform to the substrate, many species are hard to identify from the shell alone ^[2].

Similar species

• Crucibulum spinosum: It has tubular spines interspersed on the radial ribs and a yellowish-brown colour; the review gives a diameter of 46.1 mm ^[3].
• Crucibulum lignarium: It has fine radial ribs and an olive-brown colour with white radial bands; the review gives a length of 36.7 mm ^[3].

The world register accepts Crucibulum scutellatum as the valid name and bases it on Patella scutellata W. Wood, 1828 ^[1]. The Peruvian review gives it from Punta Piaxtla, in Sinaloa (Mexico), to Ecuador, and south to Pimentel, in Lambayeque (Peru) ^[3].

The Peruvian collections examined in that review amounted to 23 lots and 72 specimens, and their habitat is the rocky infralittoral ^[3]. The review was based on 1237 calyptraeid specimens from along the Peruvian coast, collected by hand in the intertidal zone and the rocky sublittoral ^[3].

Within the family, all calyptraeids are protandrous hermaphrodites: they start as males and change to females as they grow, and males may attach to the shells of females in stacks of decreasing size ^[2]. The early stages are always brooded between the female's neck, propodium and the substrate ^[2].

For Crucibulum scutellatum, Collin's compilation of modes of development classifies it as planktotrophic and without nurse eggs ^[4]. Those data come from Panama and Costa Rica, near 8° N, and not from Peru ^[4].

The anatomy of calyptraeids is dominated by modifications of the gill and the mantle cavity for filter feeding ^[2]. They are found attached to hard substrates such as rocks, shells and human-made objects, especially glass bottles ^[2].

In Crucibulum, the mantle cavity and the style sac curve backwards around a plug of connective tissue that fills the cup-shaped septum ^[2]. In the eastern Pacific, upwelling areas are associated with calyptraeid abundances of up to hundreds per m2 and with species of large body size ^[2].

The 2006 Peruvian review recorded the species in Tumbes (Puerto Pizarro, Zorritos, Bocapán, Cancas and Punta Sal), Piura (Máncora, Los Órganos, Lobitos, Paita, Bocana de San Pedro, Bayóvar and Islas Lobos de Tierra) and Ica (Bahía Independencia) ^[3]. Its habitat is the rocky infralittoral ^[3].