Crepidula atrasolea Collin, 2000

Simone, Luiz Ricardo L., 2006, Morphological and phylogenetic study of the Western Atlantic Crepidula plana complex (Caenogastropoda, Calyptraeidae), with description of three new species from Brazil, Zootaxa 1112 (1), pp. 1-64 : 17-19

Crepidula atrasolea Collin, 2000

(Figs. 3, 4, 30, 31, 68–82)

Crepidula atrasolea Collin 2000: 1500–1512 (figs. 12, 3E –F, 4, 5C, F, 6 right); 2001 (fig. 5).

Type: Holotype ANSP 19188 ; UNITED STATES OF AMERICA; Florida, Sanibel Island, Wolfert Point , 26º29'N 82º10'W . Paratypes FMNH 282203 , 282206 , 282217 .

Differential diagnosis: Shell (Figs. 3, 4): growth lines stronger, producing a rougher outer surface. Other details in Collin (2000).

Head­foot (Figs. 69, 75, 79): Color darker, with grey or black spots in foot sole and neck ventral surface. Tentacles tip weakly bifid. Eyes dark, very small, located on very short ommatophores in level between basal and middle thirds of tentacles lateral margin. Head and neck little shorter than foot length. Columellar muscle reduced, contours anterior border of shell septum, more concentrated at right (Fig. 69, 79), as in smaller specimens as in larger ones.

Mantle organs (Figs. 68, 71–73): Mantle border special arrangement of folds in middle region of pallial cavity aperture with main fold narrower, located from gill anterior end running towards left, decreasing and disappearing gradually; anterior edge of this fold short, disappearing at short distance from gill anterior end; posterior edge continuing with inner edge of mantle border (Fig. 73). This broader fold with a weak central furrow. Dorsal shell muscle well developed (Fig. 68: dm), although thin. Lateral shell muscle (Figs. 68: lm) very small, located slightly posteriorly. Pallial cavity aperture occupies about 2/3 of anterior half of shell border turned to right (if shell compared with a clock, in dorsal view and with head occupying 12 oclock, pallial aperture begins in 9:30 and finishes in 2:30 oclock) (Fig. 70). Pallial cavity length about 4/5 of total length of animal (Figs. 68, 71). Osphradium very small, monopectinate, located between anterior half of gill and mantle border, at some distance from gill anterior end (Figs. 71, 73). Osphradium length about 1/ 10 of pallial aperture length, in form of a small fold, attached to mantle, separated from gill structures. Osphradium leaflets rounded, close to each other, somewhat thick and tall, varying around 7 in number (Fig. 73). Gill filaments triangular base somewhat longer, extending by about half of filament length (Fig. 72). Endostyle (Figs. 71, 73: en) yellowish, divided along its length by a narrow, middle furrow, into 2 similar ridges. Hypobranchial gland very thin, almost absent.

Visceral mass (Figs. 68, 70, 80): broader and longer area of pallial cavity.

Circulatory and excretory systems (Figs. 74, 77): Kidney central region mostly hollow, with single, irregular lobe, rich in longitudinal vessels (Fig. 77). A very broad vessel running in center, coming from adrectal sinus; a ventral branch coming from haemocoel; also several other smaller vessel branches covering dorsal, anterior and left surface of renal chamber, and local portion of intestine. Nephridial gland in renal limit with pericardium, very small, presenting a series of triangular, transversal, narrow folds connected with dorsal renal lobe (Fig. 77: ng) in anterior region, and longitudinal folds in posterior region. Nephrostome a very small slit in left region of ventral wall (Fig. 74), in middle region of hollow portion of kidney, protected at left by larger longitudinal vessel. Adrectal sinus broad, edging externally intestine loop exposed in pallial cavity almost all along its length; connecting directly to kidney chamber anterior­left edge.

Digestive system (Figs. 76, 78): Buccal mass occupying most of proboscis inner space and a short portion of haemocoel posterior to it. Pair of dorsal folds broad, their inner edge closer to median line. Odontophore muscles (Fig. 76): m11) pair of ventral tensor muscles of radula, originating in haemocoel ventral surface in region of proboscis base, running towards anterior, penetrating in odontophore ventral, middle region; inserting in subradular membrane in ventral end of radula. Radula extending little beyond odontophore length. Radula (Figs. 30, 31) similar to that of C. margarita , distinction and notes: rachidian tooth secondary cusps varying from 4 to 6 pairs; lateral tooth with about 14–16 triangular cusps, fifth cusp very larger; inner marginal tooth with 6–10 cusps along its inner­subapical margin and about 4 in outer subapical margin; inner marginal tooth with about 4 very small cusps along its inner subapical margin. Salivary glands very narrow and small (Fig. 75), with about 1/6 of haemocoel length. Salivary glands aperture a transversal slit in anterior region of dorsal folds of buccal mass. Esophagus (Figs. 75, 78, 80) narrow, long; anterior esophagus inner surface with pair of broad folds as continuation of those of buccal mass dorsal wall, located in opposite side from each other. Stomach (Fig. 78) somewhat more curved. Anterior duct to digestive gland about in middle region of stomach ventral surface; highly dichotomic. Stomach gradually narrowing towards anterior and left, arriving close to left­posterior extremity of pallial cavity. Posterior duct narrow, strongly turned towards posterior. Stomach inner surface (Fig. 78) with a very small gastric shield located in middle­right region of right surface of stomach, by side of esophageal insertion; a narrow fold starting in right side of posterior duct to digestive gland insertion, running towards anterior, along gastric ventral surface; bifurcating in a Y­ shape in region just anterior, and right of posterior duct to digestive gland, raising a transversal fold separating gastric chamber from style sac chamber; on opposite side, this transversal fold suddenly runs towards anterior in left gastric surface, originating a pair of longitudinal folds dividing gastric surface into intestinal and style sac portions. No preserved crystalline style found. Digestive gland pale beige in color. Intestine narrow (Fig. 78) differing by ampler and more separated loops. Anus small, siphoned, located in right region of pallial cavity close to mantle border.

Genital system: Development: See Collin (2000).

Male (Figs. 79–81): Largest male examined was 6.6 mm. Testis white in color, located in anterior and left regions of visceral mass. Seminal vesicle convoluted, narrow, cream in color, located in anterior­right extremity of visceral mass (Fig. 80). Penis large (about 4 times tentacle length, and about double width), curved; suddenly narrows before tip producing a very long papilla, with about 1/3 of penis length, papilla base somewhat broad, narrowing gradually towards distal (Figs. 79, 81). Penis furrow runs about in middle region of penis ventral surface until papilla tip.

Female (Fig. 82): Ovary cream in color. Albumen gland narrower. About 5 seminal receptacles inserted in right side of albumen gland, successively smaller towards anterior. Seminal receptacles duct broad and short. Capsule gland narrower, inner duct narrow, flat, straight. Vaginal tube originating from anterior­left corner of capsule gland; running parallel to capsule gland towards right; form somewhat thick and broad (about 1/2 of capsule gland width); length about same as that of capsule gland. Genital papilla very tall, situated close to anterior region of albumen gland, at some distance from anus. Papilla with a single longitudinal fold along posterior surface, starting gradually in papilla base, finishing surrounding pore. Genital pore a small, transversal, terminal slit.

Habitat: See Collin (2000), on oyster shells near mangrove roots, up to 1 m depth.

Distribution: North Carolina, Gulf and Atlantic coast of Florida, Florida Keys.

Measurements of shells (in mm): MZSP 36328 ♀ 1: 15.2 by 11.7; ♂ 2: 4.9 by 4.6; ♀ 3: 15.0 by 11.8; ♂ 4: 6.5 by 3.4; ♀ 5: 6.6 by 5.4 (mature).

Material examined: UNITED STATES OF AMERICA; Florida; Harbor Branch , MZSP 36328 , 2♂, 3♀ (R. Collin col.)