Gaza olivacea Quinn, 1991

Simone, Luiz Ricardo L. & Cunha, Carlo M., 2006, Revision of genera Gaza and Callogaza (Vetigastropoda, Trochidae), with description of a new Brazilian species, Zootaxa 1318 (1), pp. 1-40 : 15-18

Gaza olivacea Quinn, 1991

( Figs. 24–27 , 61–63 , 89–91 )

Synonymy: see Quinn (1991:166). Complement:

Gaza sp : Hickman & McLean 1990: 91 (fig. 51a).

Gaza olivacea: Quinn 1991:166–168 , figs. 1–3. Merlano & Hegedus 1994:117, fig. 366.

Types: Holotype USNM 752369 ; Paratypes USNM 859424 , 22 shells ; USNM 752390 , 17 shells ; UMML 308365 , 1 shell ; FSBCI 39513 , 1 shell. (All examined) .

Type locality: COLOMBIA; off Península de la Guajire, 12º30’N 72º08’W, 475 m depth .

Diagnosis: Color of entire shell beige iridescent; surface smooth, spire low with about five whorls. Protoconch with hole in adult. Body whorl with very low spiral lines, glossy. Height/width 1.47 on average. Weak carina in lower level of body whorl. Umbilicus almost completely covered by callus, except by narrow lower opening. Orifices in anterior part of mesopodium: 7 on left, 8 on right side. Number of epipodial tentacles: 6 on right side. Rachidian tooth with elongated base, about 1/10 of total radular width, six lateral teeth somewhat similar to rachidian, about 10–12 tall, slender marginal teeth.

Distinctive description

Shell ( Figs. 24–27 ): Size about 35 mm. Color beige with green tinge. Outline turbiniform; spire height, volume approximately same as body whorl. Protoconch eroded forming small hole communicated with umbilicus ( Fig. 25 ). Spire profile forming hemisphere; whorls weakly convex, suture shallow. Sculpture similar to that of G. superba ; shell surface somewhat glossy; spiral lines weakly visible, about 15 spiral lines on penultimate whorl; axial sculpture almost absent, except some very weak lines in periumbilical area. Callus covering umbilicus almost completely, except for short, narrow lower region ( Figs. 26, 27 ), surrounded by inner lip, forming tube communicating with umbilical chamber.

The following anatomical description is based on a re­hydrated specimen.

Head­foot ( Figs. 89, 91 ): Snout papillae broad (about 1/20 of shout width and length), touching each other. Tentacles having two clearly separated regions: basal half broader, with long cilia; distal half slender, smooth. Epipodial tentacles slightly short, uniform in size, stubby, 7 on left, 8 on right side ( Fig. 89 ), inserting on ventral surface of epipodium (instead of its border). Foot’s anterior orifices 6 on right ( Fig. 91 ) side, not seen on left side.

Operculum: similar to that of Gaza compta .

Mantle organs: Details not seen because of problematic preservation.

Digestive system ( Fig. 90 ): Foregut with similar characters to G. compta . Radular ( Figs. 61–63 ) characters similar to those of G. compta , with following differences: rachidian and lateral teeth about 50% longer antero­posteriorly than their width ( Figs. 61, 62 ); rachidian about 1/10 of total radular width; fewer marginal teeth (about 10–12 pairs per row), slender, with marginal cusps along almost entire length (about 30 pairs). Intestinal loops in anterior region of visceral mass, posterior region of pallial cavity very wide ( Fig. 90 ), having two long antero­posterior loops preceding rectum.

Measurements of shell (in mm): Holotype = 32.9 x 27.0.

Distribution: Caribbean Sea to Rio de Janeiro, Brazil.

Habitat: Muddy bottom with coral aggregations; from 370 to 606 m depth, mostly at 400 m depth; with a record of a dead shell in 28 m depth (FMNH 187421).

Material examined: ( R. V. Oregon, o.t.; S.Walker det.). COLOMBIA. Off Riohacha ( R. V. Oregon II) : 11º25’N 73º56’W, 440 m depth, FMNH 187431 , 4 shells (sta. 11252, 10/ xi/1970) ; off Península de la Guajire, 444–454 m depth, FMNH 187445 , 2 shells, (sta. 4923, 2/vi/1964) , 12º31’N 71º58’W, 380 m depth, FMNH 187435 , 2 shells (sta. 5692, 10/ x/1965) ; 12º30’N 72º08’W, 475 m depth, FMNH 187434 , 12 shells (Topotype, sta. 5690, 10/x/1965) ; off Santa Marta, 11º03’N 75º10’W, 370 m depth, FMNH 187440 , 12 shells (sta. 10260, 2/xii/1968) , 11º18’N 74º44’W, 606 m, FMNH 187424 , 3 shells (sta. 11248, 9/ ix/1970) , 11º04’N 74º25’W, 28 m depth, FMNH 187421 , 1 shell (sta. 10266, 2/xii/1968) . TRINIDAD. Northwest, 11º33’N 62º30’W, 370 m, FMNH 187442 , 2 shells (sta. 2782, 20/ iv/1960) , 11º37’N 62º47’W, 370–444 m depth, FMNH 187428 , 3 shells (sta. 5037, 24/ix/ 1964) , 11º31’N, 62º24’W 343–370 m depth, FMNH 187427 , 6 shells (sta. 2351, 23/ix/ 1958) ; off west side on Penin, 12º29’N 72º19’W, 490 m, FMNH 187439 , 3 shells (sta. 5689, 9/x/1965) . SURINAM. North off Paramaribo , 7º34’N 54º13’W, 370 m depth, FMNH 187433 , 6 shells (sta. 4301, 24/iii/1963) , 7º34’N 54º50’W, 370 m depth, FMNH 223560 , 49 shells (sta. 2005, 6/xi/1957) . FRENCH GUIANA. North of Cayenne , 7º10’N 53º07’W, 370 m depth, 6 shells, FMNH 187438 (sta. 2026, 9/xi/1957) , 370 m, 20 shells, FMNH 223558 (sta. 2026, 9/xi/1957) . BRAZIL; Rio de Janeiro; 23º40’S 41º00’W, 545 m depth, IBUFRJ 10050 , 1 shell and part of dry specimen (Revizee central II, RV Astrogaroupa, sta. #5C, 25/x/1997) .

Remarks: The single lot examined from Brazil (IBUFRJ 10050), contains one complete dry specimen and soft parts of another specimen. This material differs from the remaining lots of G. olivacea examined by having a lower spire and a more discoidal shell outline. However, the remaining shell characters, such as sculpture, color and umbilical flap, are very similar. As the G. olivacea lots from the north Atlantic lack soft parts for a more comprehensive analysis, and taking into account the remaining shell similarities of both materials, a conservative approach is given here: the specimens from Brazil are referred to G. olivacea , until addition material becomes available.

Figures

FIGURES 24–36. Gaza spp. Figs. 24–27: G. olivacea FMNH 223560 (from Surinam). Figs. 24–26: Shell, apertural, apical and umbilical views. Fig. 27: Detail of umbilical area. Scale bar = 10 mm. Figs. 28–32: G. fischeri Paralectotype USNM 94989. Figs. 28–30: Shell in apertural, apical and umbilical views. Fig. 31: Detail of umbilical area. 32. Operculum, outer view. Scale bar = 5 mm. 33–36. G. rathbuni AMNH 254993 (off Cape Mala, Panama) shell. Figs. 33–35: Apertural, apical and umbilical views. Fig. 36: Detail of umbilical region. Diameter = 32.5 mm.

FIGURES 58–66. Shell and radulae in SEM. Figs. 58–60: Callogaza watsoni from off Pará, Brazil (specimen mentioned by Dall, 1889, USNM 97116): apertural, umbilical and apical views; diameter = 7.1 mm. Figs. 61–63: Gaza olivacea. Figs. 61–62: Central and lateral teeth. Fig. 63: Detail of lateral teeth; scale bars = 100 µm. Figs. 64–66: Gaza superba. Fig. 64: Entire shell; scale bar= 200 µm. Fig. 65: Detail of central and lateral teeth; scale bar = 100 mµ. Fig. 66: detail of lateral teeth; scale­bar = 100 µm.

FIGURES 89–92. Gaza spp. anatomy. Figs. 89–91: G. olivacea, Brazilian re­hydrated specimens. Fig. 89: Head­foot, frontal view. Fig. 90: Mid and hindgut as in situ, dorsal­slightly right view. Fig. 91: Foot (re­hydrated and partially damaged), head removed, foot anterior orifices (fo) shown. Fig. 92: G.compta, foot, head removed, foot anterior orifices (fo) shown. Scale bars = 2 mm.