Gaza fischeri Dall, 1889

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 : 18-19

Gaza fischeri Dall, 1889

( Figs. 28–32 , 55–57 , 93–98 )

Gaza fischeri Dall, 1889: 355–356 (pl. 37, fig. 6). Clench & Abbott 1943: 4 (pl. 3, fig. 3–5: lectotype). Abbott 1974: 49 (fig. 376). Abbott & Dance 1983: 40 (unnumbered text­fig. of holotype).

Types: Lectotype MCZ 7543 (examined) (explicitly designed by Clench & Abbott 1943) . Paralectotype USNM 94989 (examined) .

Type locality: Caribbean Sea , off St. Lucia Island, 13º54’55”N 61º06’05”W, 229 m depth, (A. Agassiz col., 16/ii/1879) .

Diagnosis: Color of entire shell pale­beige iridescent, smooth, spire very low with about five whorls. Protoconch without hole in adult. Body whorl with very narrow spiral lines, spire diameter about 60% of total shell diameter. Weak carina at middle level of body whorl. Umbilicus completely covered by callus. Orifices in anterior part of mesopodium: 5 on left, 6 on right side. Number of epipodial tentacles: 6 on right, 5 on left side. Rachidian tooth with trapezoidal base, about 1/6 of total radular width, about 20 tall, slender marginal teeth.

Distinctive description

Shell ( Figs. 28–31 ): Size about 30 mm. Color beige with orange tinge. General form discoid; spire low, height nearly one half of body whorl, about half its volume. Spire profile forming flat dome; whorls highly convex, suture well marked. Protoconch smooth, glossy, with about 2 whorls ( Fig. 29 ). Sculpture similar to that of G. compta , with about 25 spiral lines in penultimate whorl. Teleoconch with first 4 whorls possessing axial lines weakly broader than local spiral lines, well spaced from each other, stronger close to upper suture smooth, gradually disappearing towards lower suture; gradually axial lines disappearing before penultimate whorl; peri­umbilical area with weak axial sculpture. Callus sealing entire lower region of umbilical opening ( Figs. 30, 31 ).

Head­foot ( Figs. 93, 94, 96 , 98 ): Snout papillae three­times larger at edge than close to mouth ( Fig. 98 ). Foot’s anterior orifices; 5 orifices on left, 6 at right side; each orifice located at tip of rounded, low stalk ( Fig. 96 : fo). Flap of anterior third of epipodium as long as snout ( Fig. 93 : ep). Remaining epipodium with very long, slender tentacles of similar size, middle one about half as long, 6 on right, 5 on left side.

Operculum ( Fig. 32 ): similar to that of G. compta .

Mantle organs ( Fig. 95 ): Anterior end of gill pointed. Left gill filaments with about twice surface area of right filaments, possessing one ventral­left, pointed projection; right filaments simpler, weakly pointed. Rectum about 1/4 length of pallial cavity width, sigmoid, posterior region as undulating line up to region posterior to anus.

Digestive system ( Figs. 95 , 97, 98 ): Foregut similar to that of G. compta , including intrinsic and extrinsic musculature of odontophore; m1v about 50% broader. Radula ( Figs. 55–57 ): Cutting edges of rachidian, lateral teeth with triangular fashion; their bases having wider proximal edge than distal edge (trapezoidal); their projected region about 50% narrower ( Figs. 55, 56 ). About 20 marginal teeth, narrow, with 3 pairs of very small marginal cusps, along most of tooth shaft. Salivary glands small, attached to esophageal origin region, on lateral sides ( Fig. 97 : sg). Fecal material solid, hard, filling entirely intestine, possessing three middle, ventral, longitudinal furrows ( Fig. 95 ).

Central nervous system ( Fig. 97 ): Nerve ring similar to that of G. compta , except for about 30% more slender cerebral ganglia.

Measurements (in mm): Lectotype = 32.5 x 21.0; AMNH 269826: #1 23.0 x 15.0; #2, 20.9 x 14.3.

Distribution: Caribbean Sea.

Habitat: Muddy sand bottom; about 230 m depth.

Material examined: Lectotype, Paralectotype. BAHAMAS; off Long Island, AMNH 269826 , 2 specimens ( RV Columbus, deep trawl, 21/xi/1981) .

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 49–57. Radulae in SEM. Figs. 49–52: Gaza compta. Fig. 49–51: Holotype. Figure 49: entire shell; scale bar = 100 µm. Fig. 50: Detail of central and lateral teeth; scale bar = 50 µm. Fig. 51: Same, detail of marginal region; scale bar = 50 µm. Fig. 52: Paratype, central region; scale bar = 50 µm. Figs. 53–54: G. cubana. Fig. 53: Entire shell; scale bar = 100 µm. Fig. 54: Lateral teeth, scale bar = 100 µm. Figs. 55–57: G. fischeri. Fig. 55: Entire shell, scale bar = 100 µm. Fig. 56: Detail of central and lateral teeth; scale bar = 100 µm. Fig. 57: Detail of lateral region; scale bar = 50 µm.

FIGURES 93–96. Gaza fischeri anatomy. Fig. 93: Head­foot, lateral­left view. Fig. 94: Same, lateral­right view, partially shown. Fig. 95: Pallial cavity hoof, ventral view, rectum (rt) seen as in situ, a transversal section of the fecal thread, in indicated region, also shown. Fig. 96: Foot, head removed, foot anterior orifices (fo) shown. Scale bars = 2 mm.

FIGURES 97–98. Gaza fischeri anatomy. Fig. 97: Foregut, left view, some adjacent structures, like part of nerve ring, also shown as in situ. Fig. 98: Head and haemocoel, ventral view, foot and columellar muscle removed. Scale bars = 1 mm.