Nacella FLAMMEA

NACELLA FLAMMEA (GMELIN, 1791)

(FIG. 7)

Patella flammea Gmelin, 1791: 3716, pl. 5, fig. 42.

Patinella flammea – Strebel, 1907: 145, pl. 5, fig. 73.

Nacella (Patinigera) flammea – Powell, 1973: 197, pl. 181; Mutschke et al., 1988: 8; Ramírez, 1981: 57; Linse, 1999: 400; Valdovinos & Rüth, 2005: 508, fig. 5C; González-Wevar et al., 2010: 116.

Nacella flammea – Ríos & Gerdes, 1997: 51; Ríos & Mutschke, 1999: 196; de Aranzamendi et al., 2009: 1; González-Wevar et al., 2011a: 1937; 2017: 863; Rosenfeld et al., 2015: 55; 2016: 77.

Material studied: Melimoyu (43º03’33.63’’ S, 73º15’12.55’’ W) N = 25; Port Famine, Strait of Magellan (53º36’34.07’’ S, 70º55’53.40’’ W) N = 50; Laredo Bay, Strait of Magellan (52º56’59.14’’ S, 70º48’03.96’’ W) N = 30; Tekenika Bay (55º03’24.66’’ S, 68º 07’52.22’’ W) N = 40; Puerto Williams, Beagle Channel (54º56’04.95’’ S, 67º36’48.33’’ W) N = 40; Hookers Point, Falkland / Malvinas Islands (51º42’09.60’’ S, 57º46’07.49’’ W) N = 25.

Shell: The shell shape and sculpture are relatively constant in the analysed individuals (Fig. 7A–C). The species exhibits a conical morphology, dorsally depressed with a thin and relatively translucent shell (Fig. 7A–F). The anterior part of the animal is laterally compressed (Fig. 7D–F). It has a medium shell size (maximum length 80 mm) and a low profile. The apex is situated at the anterior 30–40% of the shell’s length. All the slopes of the shell are regularly straight (Fig. 7A–F). The aperture of the shell is oval to oblong. The surface of the shell is sculptured with radial ribs, more obvious in the anterior zone, and concentric growth lines, which increase in thickness towards the shell margin. The margin of the shell is relatively even. The external coloration is quite constant in the analysed individuals with a white coloration pattern with light brown/grey/purple rays. Some rays beginning below the apical zone, others at the margin. The internal part of the shell exhibits a nacreous halo and a dun-brown spot corresponding to the animal’s body impression. Nacella flammea individuals exhibit similar internal and external coloration patterns.

External anatomy: The ventral area of the foot is white to light grey and the epipodial fringe is recognizable (Fig. 7G). The mantle fold is thick and creamy coloured. The mantle tentacles are in alternated series of three white shorter ones and a light grey longer one (Fig. 7G). The cephalic tentacles are not pigmented (Fig. 7G).

Radula: The first lateral teeth are set close together on the anterior edge of the basal plates, long and sharp pointed, with two cusps. The second laterals are broader, wider spaced, with three short cusps (Fig. 7H).

Distribution: Magellanic province. Pacific Patagonia: from Melimoyu (44°S) to Cape Horn (56°S). Atlantic Patagonia: Tierra del Fuego. Falkland/ Malvinas Islands (Fig. 7I).

Habitat: Subtidal rocky ecosystem between 5 and 40 m.

Comments: Field observations along the Magellanic province reveal that N. flammea exhibits a patchy distribution, being highly abundant in some localities and completely absent at others. Nevertheless, preliminary population-based analyses of the species suggest that it represents a single genetic unit across its distribution (unpublished data). This revision extends the known northern limit of this species to the Melimoyu Islands (44º03’33.63’’ S, 73º15’12.55’’ W).