Rissoella venezolanicola Caballer, Ortea & Narciso 2011

Shell very small (Tab. 3), smooth and translucent (Fig. 18); protoconch about half a whorl after the nucleus (Fig. 19); teleoconch of two whorls and three quarters; aperture oval, with the columella slightly bowed and arched; umbilicus narrow and deep, slightly closed by the expansion of the columellar edge; preumbilical cord extended, with an angle delimiting and closing the umbilicus forming a trapezoid (Figs 11–12, 20); average height of the last whorl, 82.9% of shell length; average height of the aperture, 49.6% of shell length (Tab. 3); Shell length/width ratio = 1.52; spiral angle = 58°; umbilical angle = 23°-25°. Operculum oval, translucent with an amber tinge, membranous consistence; head, flanks, oral lobes and cephalic tentacles translucent white with scattered black to greenish brown dots (Fig. 6); eyes black; foot translucent white (Fig. 7); hypobranchial gland translucent white with scattered blotches black to greenish brown and a distinctive yellow design quaver-shaped (Fig. 8); visceral mass in the first whorls, black; protoconch with fuchsia highlights in live animals. Odontophoral cartilages kidney-shaped, with large uncini placed longitudinally (Fig. 21); radular formula of an specimen 0.96 mm shell length, 16 × 1.1.R.1.1; rachidian tooth wide, with bilobed apex forming two smooth cusps (Fig. 22), slightly larger than marginal tooth; lateral tooth triangular, 28.3 µm long, with the apex hooked and smooth; imbricated with the opposite tooth above the rachidian; marginal tooth triangular and curved, 16.3 µm long, with blunt apex. Table 3.Rissoella venezolanicolasp. n. Measurements of specimens. (%) means percentage compared to the total length of the shell.Protoconch (whorls)Last whorl (mm)Aperture(mm)Length /widthHolotype1.02 × 0.66 mm1.250.82 (80%)0.46 (45%)1.54Paratypes0.96 × 0.64 mm1.250.80 (83%)0.52 (54%)1.500.54 × 0.46 mm1.50.46 (85%)0.38 (70%)1.18Average83%*50%/57%*1.52/1.4 * Excluding the juvenile specimen. Synthesis of characters of the Caribbean species ofRissoellaGray, 1847 based onRobertson (1961), Wise (1998), Ortea and Espinosa (2001;2004), Espinosa and Ortea (2009). Aa = Average height of the aperture vs shell length, Al = Average height of the last whorl vs shell length, E = Eyes, H = Habitat, HG = Hypobranchial gland, LW = Shell length/width ratio, Pc = Preumbilical cord, Pf = Pigmentation of the body in the firsts whorls, Rf = Radular formula, Rt = lateral and marginal teeth, Sa = Spiral angle, U = Umbilicus, Ua = Umbilical angle.ShellAlAaLWSaUaUPcEHGBand around HGPfRfRtHRissoella caribaeaTransparentTo 1.8 mm length75–80%50%1.4260°25°Narrow with a keel. Partly closed by columellar edgeAbsentBlack on unpigmented areasGrey with black blotchesPale yellow. Boomerang-shaped with transversal bandsHomogeneous black30 × 1.1.R.1.1.Slightly serratedClean rocks and coral rubleRed and green algae on mangrove rootsShallowRissoella galbaTransparent with white band around umbilical regionTo 0.68 mm length-----NarrowAbsentBlackPale yellowAbsentHomogeneous pale brown--Filamentous green algae on rocks or filamentous red algae on mangrove rootsIntertidalRissoella gandocaensisTransparentTo 0.8 mm length-----With a slight keelAbsentBlack on clear areasYellow with violet blotchesAbsentViolet with red blotches---Rissoella ameliaeTransparentTo 1.62 mm length75%50%1.5745°18°Narrow and deepAbsentUnpigmented or absentYellow with pale violet blotchesAbsentHomogeneous pale violet--Rocks and coral ruble on sand in the coral slope15–18 m deepRissoella belkisaeTransparentTo 1.2 mm length80%50%1.3860°25°Narrow but not deepAbsentUnpigmented or absentYellow with black blotchesAbsentHomogeneous dark grey--Rocks and coral ruble on sand in the coral slope20–27 m deepRissoella dianaeTransparentTo 1.15 mm length75%44%1.640°30°Wide and deep. Partly closed by columellar edgeAbsentBlackTranslucentCurved, Yellowish white, broken at the backBrilliant Yellow with big square-shaped black blotches--Rocks and coral ruble on sand in the coral slope25–30 m deepRissoella zaidaeTransparentTo 1 mm length78%50%1.6350°30°Narrow and deepPresentBlack on unpigmented areasKidney-shaped, pale violet with lilac blotchesGold-yellow with transverse bandsHomogeneous lilac--Rocks and coral ruble on sand in the coral slope15–18 m deepRissoella floraeTransparentTo 1.2 mm length79%55%1.3560°18°Narrow and deepPresentBlack on lighter areas of orange hueIntense yellow with black spotsAbsentHomogeneous brown-grey--Rocks and coral ruble on sand in the coral slope25–30 m deepRissoella elsaeTransparentTo 1.2 mm length76%50%1.6945°25°Nearly closed by columellar edgePresentUnpigmented or absentWhite with big green blotchesKidney-shaped, white without transverse bandsHomogeneous green--Rocks and coral ruble on sand in the coral slope15–25 m deepRissoella taniaeTransparentTo 1.1 mm length82%52%1.465°43°WidePresentUnpigmented or absentCurved. White with big green spotsAbsentHomogeneous dark green--Rocks and coral ruble on sand in the slope15 m deepRissoella aliciaeTransparentTo 1.45 mm length67%40%1.5245°22°Wide and deepAbsentBlack on lighter areasPale yellow with black blotchesYellow. Discontinuous, broken at the backViolet with circular brown blotches--Filamentous algae on rocks in sandy bottoms35 m deepRissoella morrocoyensissp. n.Transparent To 1.25 mm length85%60%1.3260°21°–28°Very narrow and deep. Partly closed by columellar edgePresentBlack on unpigmented areasTranslucent white, with black blotchesPale yellow. Boomerang-shaped with no transversal bandsHomogeneous black15 x 1.1.R.1.1.SmoothLeaves of Thalassia near mangroves1 m deepRissoella venezolanicolasp. n.Transparent To 1.02 mm83%57%1.5258°23°–25°Narrow and deepLong, with an angle, forming a trapezoidBlack on unpigmented areasTranslucent white with black to greenish brown blotchesYellow. Quaver-shapedHomogeneous black16 x 1.1.R.1.1.SmoothCoral reef on on Dictyota spp.10 m deep