File:American malacological bulletin (1988) (17970017719).jpg

Title: American malacological bulletin
Identifier: americanmal6719881990amer (find matches)
Year: 1983 (1980s)
Authors: American Malacological Union
Subjects: Mollusks; Mollusks
Publisher: (Hattiesburg, Miss. ?) : (American Malacological Union)
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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84 AMER. MALAC. BULL. 6(1) (1988) of valves dark red with white maculations; unexposed parts dark red to plum. Girdle broad, fleshy, tan to dark reddish brown, appearing smooth but with very small clusters of short, stout, white spicules widely scattered on dorsal surface, especially where girdle intrudes between valves; long spicules in dorsal tufts reddish brown, shorter basal spicules of tufts blue-green. Valve i semilunate (Fig. 11), wider than long, concave posteriorly, with anterior insertion plate bearing 5 U-shaped slits; tegmentum occupying about 65% total valve length. Valves ii-vii beaked (Fig. 12); tegmentum alate (wing-shaped), little wider than long but constricted over much of anterior portion, with markedly concave anterolateral margins; sutural laminae very large, longer than wide, broad, flared antero- laterally, separated anteriorly by wide, deep, U-shaped sinus; lateral margins not parallel to each other or to jugum; single slits near midpoints of margins. Valve viii broadly triangular (Fig. 13), about twice as wide as long, rounded posteriorly, with mucro posterior of center; tegmentum drop-shaped, longer than wide, constricted anteriorly along jugum; sutural laminae very wide, flared anteriorly, separated by wide, V- shaped sinus, with straight anterior margins; 2 slits in posterior insertion plate small, narrow, V-shaped. Jugum smooth, narrow, with parallel sides well- separated from lateral tegmental surface, extending anteriorly beyond main body of tegmentum. Tegmental pustules drop- shaped (Fig. 14), 120 /*m long, 80 /tm wide, with single cen- tral macresthete, 3-6 micresthetes nearly all adapical of macresthete. Girdle upper surface covered with dense mat of very small (50 /xm) brown spicules interrupted by clusters of stout, white, 200-400 ^m long spicules (Fig. 15), clusters very sparse on main dorsal surface, dense where girdle intrudes between valves; 18 anterior and sutural tufts containing about 50 straight, stout, sharp-tipped spicules up to 2 mm long, brown along shafts, blue-green at base, with extremely fine, needle- like spicules within base; margin fringed with slender, straight or slightly curved, sharp-tipped blue or blue-green spicules up to 1.4 mm long; underside densely covered with slender, sharp-tipped spicules about 80 ^m long, directed toward periphery. DISCUSSION: Pilsbry (1983) described Acanthochitona rhodea from an alcoholic specimen 28 mm long, 15 mm wide, that had already "lost the cuticle and hairs from its girdle, leaving a smooth whitish surface pitted at the sutures." Thus, one important identification character, the girdle spicules, could not be described. Now all that remains of the holotype are three disarticulated valves, ii, vii(?), and viii (Figs. 16-18). Nevertheless, sufficient evidence remains in the drop-shaped pustules, well-illustrated by Pilsbry (1893: pi. 12, fig. 49), to demonstrate that A. rhodea is the species that inhabits the Caribbean coast of Panama. Thus, Ferreira's (1985) restric- tion of the type locality to Portobelo was appropriate. Characters important in separating Acanthochitona rhodea from A. hemphilli include the drop-shaped rather than reniform pustules, the dark red rather than greenish white sutural laminae, and the small clusters of stout spicules widely scattered among the mat of shorter spicules on the dorsal
Text Appearing After Image:
Figs. 16-18. Acanthochitona rhodea (Pilsbry, 1893), holotype; "Panama"; ANSP 63429. Fig. 16. Valve ii. Fig. 17. Valve vii (?). Fig. 18. Valve viii. surface of the girdle. Differences between A. rhodea and the Pacific coast species are discussed under remarks following the description of that species. Ferreira's (1985) distributional records of Acantho- chitona rhodea are unreliable because he identifed all three species as A rhodea. Houbrick's (1968) specimens from the Caribbean coast of Costa Rica, which I examined, are A. rhodea. Leloup's (1941) description and illustrations of drop- shaped tegmental pustules (his figs. 5, 6) and large spicules scattered in widely separated groups among the smaller spicules of the dorsal girdle surface demonstrate that his specimens from off Colombia in 28-29 fm (51-53 m) were A. rhodea. Scattered spicule clusters on the girdle and shapes of valves i, vii, and viii indicate that specimens illustrated as A. hemphilli from Curacao by Kaas (1972) are A. rhodea. Likewise, Gdtting's (1973) illustration of scattered clusters of girdle spicules indicates that specimens he reported as A. rhodea from Caribbean Colombia were identified correctly. Thus, the species is known with certainty only from the southern Caribbean Sea, where it usually is collected in the shallow subtidal zone.

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