Crepidula pyguaia, Simone, 2006

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 : 23-26

Crepidula pyguaia new species

(Figs. 7–9, 34, 97–106)

Crepidula protea: Rios 1994: 71 (part).

Types: Holotype: MZSP 35831 ♀ . Paratypes: BRAZIL; Santa Cataria; Bombinhas , 0–1 m depth, MZSP 35832 , 2♀ (Tarasconi col., 22/vii/1993) , Trapiche and Embrulho beaches, MZSP 34640 , 2♀, 2 shells, 9 young (Simone col. 20/ii/2002) ; Camburiu, Central beach, MZSP 34603 , 2 shells (Simone col. 21/ii/2002) ; Itapema, Canto da Praia , MZSP 35842 , 2♀, 1 shell (Tarasconi col., 28/xii/1999) .

Type locality: BRAZIL; Santa Catarina; Bombinhas, Enseada de Zimbros 27º06S 48º 30W (otter trawl, 2–5 m depth, xii/1993, Tarasconi leg.) .

Diagnosis: Shell occurring intertidal in Santa Catarina coast. Shell whitish, with periostracum persistent covering most of shell. Siphonal pallial fold broad and wide. Pericardium constricted in middle portion, being narrow in its posterior half. Osphradium occupying about 5% of pallial aperture, bearing about 10 filaments close from each other. Pallial oviduct having 7 seminal receptacles connected to albumen gland almost in same region. Female genital papilla lacking folds, broad, irregular, inflated.

Description: Shell (Figs. 7–9): Of medium size (up to 20 mm), white, convex, flat, surface opaque. Protoconch not seen (eroded). Periostracum heavy, rich in hair, color pale brown, lost in older regions but generally covering most of shell. Sculpture lacking, except concentric undulations and growth lines. Septum somewhat short, wide, triangular, curved septum lateral insertions slightly far from shell outer edges, mainly at right. Septum anterior edge with a wide central notch, its right edge almost straight, its left edge curved, convex; another narrower notch in left end weakly deeper. Inner surface glossy, white, smooth.

Head­foot (Figs. 97, 103): General characters similar to those of C. margarita , differences and notable features following. 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 very reduced, contours anterior border of shell septum, more concentrated at right (Fig. 97). Anterior edge of foot, with pedal gland furrow, simple.

Mantle organs (Figs. 98–101): Characters similar to those of C. plana , remarks following. Mantle border special arrangement of folds (in middle region of pallial cavity aperture) very broad, covering anterior end of gill, and exceeding beyond mantle border (Figs. 99, 100); decreasing gradually towards left, disappearing in middle level of osphradium. This fold possesses a broad and shallow central furrow. Dorsal shell muscle well developed (Fig. 98: dm), relatively large. Lateral shell muscle reduced, almost absent. Pallial cavity aperture occupies almost half 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 3 oclock) (Figs. 98, 99). Pallial cavity length about same of total length of animal (Figs. 98). Osphradium small, length about 1/6 of pallial aperture length. Osphradium leaflets tall, tip rounded, close from each other, somewhat thick, varying around 11 in number (Fig. 100). Gill filaments triangular base short, extending by about 1/5 of filament length (Figs. 100, 101). Endostyle (Figs. 99, 100: en) simple. Hypobranchial gland thin, white, more developed in left side of intestine.

Visceral mass (Figs. 98, 99): Shorter and broader than that of C. margarita .

Circulatory and excretory systems (Fig. 102): Characters very similar to those of C. atrasolea , remarks following. Pericardium right region broader, with auricle curved, possessing a blunt angle in its middle anterior region. Kidney posterior­right region with 2–3 broad, tall, longitudinal folds in dorsal surface; these folds running towards anterior covering left surface of rectum, bearing longitudinal folds; in anterior­left region renal issue covering only dorsal surface, having oblique folds, some penetrating in adrectal sinus. Adrectal sinus continuous to kidney, surrounding rectum up to short distance of anus, gradually decreasing.

Digestive system (Figs. 103–105):. Buccal mass extending little posterior to proboscis. Odontophore muscles (Fig. 104): m7 pair with insertion inside radular sac, connected with each other by about half of their length; m11 pair present. Radula extending little beyond odontophore length. Radula (Fig. 34): rachidian tooth tall, narrow, central cusp large and sharp, single secondary cusps, no basal cusps but pair of lateral reinforcements on its borders; lateral tooth broad, curved internally, with about eight triangular cusps, medial cusp larger, apical, turned towards median, cusps somewhat similar sized, disappearing about in middle region of tooth, remaining a slight thick border; both marginal teeth long, curved, tall, sharp pointed tip, about seven cusps in their inner­apical margin; inner marginal tooth with about double width than outer marginal tooth. Salivary glands narrow, (Fig. 103), length longer than of haemocoel length, running almost straight along haemocoel, becoming broader in region posterior to nerve ring. Stomach (Fig. 105) similar to that of C. atrasolea , except for 1) insertion of esophagus somewhat close to posterior end of stomach; 2) posterior duct to digestive gland very much narrow, simple, running towards posterior; 3) anterior duct to digestive gland broad, dichotomic only after some distance. Stomach inner surface with a single, narrow, pair of folds running along ventral surface of style sac; these folds running in opposite side from each other in region just anterior to anterior duct to digestive gland, surrounding origin of style sac, fading in dorsal surface. Digestive gland pale beige in color. Intestine similar in attributes than that of C. atrasolea , except for strongest U­shaped loop of rectum exposed in pallial cavity (Figs. 100, 105).

Genital system: Development: All examined specimens females and larger than 15 mm. No males available.

Female (Fig. 106): Albumen gland narrower, differing little from visceral oviduct. About 7 seminal receptacles inserted in right side of albumen gland, reunited in a short region. Seminal receptacles duct slender and long. Capsule gland narrower, somewhat triangular, inner duct broad, flat, straight; walls slightly thin. Vaginal tube originating from anterior­left region of capsule gland; running obliquely to capsule gland towards right, narrow; length little shorter of that of capsule gland; vaginal tube inner surface with 7–8 longitudinal, very narrow folds. Genital papilla tall, situated at sort distance of anterior region of albumen gland, at long distance from anus; its inner surface continuous with vaginal tube folds. Papilla broad, blunt, anterior half semispherical, posterior surface with irregular folds Genital pore a transversal, terminal slit with edges tall and thick.

Central nervous system: With normal characters as remainder known Crepidula ( Simone 2002) , located posterior, far removed from buccal mass, close to visceral mass.

Habitat: Intertidal rocks.

Distribution: Brazilian coast of Santa Catarina.

Measurements of shells (in mm): MZSP 35831: 16.3 by 14.0; MZSP 35832, ♀ 2: 16.0 by 13.4; ♀ 3: 19.4 by 14.0.

Etymology: The specific epithet came from the Tupy language, pyguaia , meaning concave, and allusion to the possible extreme form of some specimens.

Material examined: Types.

Discussion: Crepidula pyguaia is similar to the other congeneric species from Western Atlantic. Differs mainly in flat, concave shell, somewhat rounded outline, and by heavy periostracum preserved in youngest region. The characteristic uniform white color is also distinctive, since the remaining species are usually brownish. The anatomical characters also corroborate with the specific separation, mostly explored above. The most important are the longer osphradium, with filaments closer to each other; the shorter triangular base of the gill filaments; the curved fashion of the auricle; the longer salivary glands; the different conformation of gastric ducts to digestive gland (simpler and narrower); and the strongest curve of the U­shaped portion of rectum. However, the deeper differences are in the characters of the pallial oviduct, such as the narrow albumen gland situated almost perpendicularly to the capsule gland; the seminal receptacles in a larger number, reunited forming a single mass, and the genital papilla blunt, almost spherical.

C. pyguaia has been identified as C. protea , a species re­described in Simone (2002) occurring in deeper waters (generally on other shells), with taller and more convex shell, lacking periostracum, and more colorful.