Calliostoma melliferum, Cavallari & Simone, 2018

Cavallari, Daniel C. & Simone, Luiz R. L., 2018, A new species of Calliostoma (Vetigastropoda: Calliostomatidae) from Canopus Bank, off northeastern Brazil, Zootaxa 4457 (1), pp. 156-166 : 157-163

Calliostoma melliferum sp. nov.

( Figs. 1–33 )

Type material. Holotype: MZSP 53718. Paratypes: MZSP 53923, 1 spm (viii/2005); MZSP 53693, 5 spm (viii/ 2005); MZSP 53711, 2 shells (viii/2005); MZSP 55522, 1 spm (viii/2005), all from type locality (same depth); same locality data, 240-260 m, MZSP 53939 , 2 shells (viii/2005) ; MZSP 66589, 1 shell (viii/2005); MZSP 67310, 6 shells (xi/2005); MZSP 70308, 70 shells (xi/2005); MZSP 71960, 1 shell (viii/2005); MZSP 71961, 1 shell (xi/ 2005); MZSP 90268, 150 shells (xi/2005); MZSP 94218, 27 shells (xi/2005); MZSP 94254, 13 shells (xi/2005); MZSP 94837, 1 shell (xi/2005); MZSP 100414, 6 shells (xi/2005).

Type locality. Brazil, Ceará, 190 km off Fortaleza, Canopus Bank , 02°14’25”S, 38°22’50”W, 60 m (Coltro & Costa leg., viii/2005).

Diagnosis. Shell with slightly convex whorls and spire slightly taller than wide; background color ivory, with honey yellow spiral cords and apex; suture marked by distinct thin, smooth suprasutural cord; base inflated, smooth; umbilicus narrow, deep. Surface of snout smooth, with small lateral expansions; pair of anterior odontophore cartilages fused; anterior and posterior odontophore cartilages partially fused; horizontal muscle divided into m6 and m6a; spiral caecum in stomach absent; mantle border bearing long papillae aligned in a single row.

Description. Shell ( Figs. 1–9 , 21–23 , 30–33 ). Shell small (H = 8–10 mm), trochoid, slightly taller than wide (H/D ~1.2), of up to 7.25 slightly convex whorls; ground color ivory white, with honey yellow apex ( Fig. 2 ) and spiral cords ( Fig. 3 ), occasionally with nacreous gleam underneath, visible through transparency ( Figs. 5–8 ). Spire tall (height ~1/2 of shell height), prominent, high and broad; spire angle ~60°. Protoconch ( Figs. 9 , 23 ) prominent, of ~1 whorl (width = 0.32–0.35 mm), glossy, honey yellow, apical fold tip with a darker-orange shade; surface sculptured with intersected delicate lines forming a honeycomb-like pattern of hexagons; transition marked by a thick terminal varix. Teleoconch I short (~0.1 whorl after protoconch), sculptured with closely spaced axial striae and 4–5 sinuous spiral ribs with variable width; growth scar nearly indistinct. Teleoconch II with up to ~6 convex whorls; first 3.5 whorls internally calcified in adult specimens ( Figs. 31–32 ); whorls mainly sculptured with 4–6 spiral cords of similar width ( Figs. 2, 7 ) that multiply by intercalation, separated by wider interspaces (~ 2x cord width); primary cords presenting numerous small, closely-packed, angular nodules, secondary cords smooth ( Figs. 21 , 30 ); ontogeny of cords as follows ( Fig. 22 ): P1 commencing at 0.75 teleoconch whorl; P2 commencing right after protoconch; P3 commencing at 1.3 teleoconch whorl; P4 commencing just before P3 on same whorl; S1 commencing at 4.5 whorls; S2 commencing at 4.3 whorls. Suture delicate but distinct, marked by a thin, smooth suprasutural cord ( Figs. 21 , 30, 33 ). Aperture rounded to subquadrate ( Figs. 1, 5, 8 ), prosocline ( Fig. 6 ), height ~1/ 3 of shell height, ivory white, nacreous, somewhat dislocated laterally in older specimens ( Fig. 5 ); inner lip slightly flared, forming a narrow callus ( Figs. 1, 5 ). Base distinctly convex, mostly smooth ( Fig. 33 ) or very rarely sculptured with smooth, almost obsolete spiral cords ( Fig. 4 ), yet always presenting two smooth, similarly wide peripheral cords, the uppermost of which is visible as a suprasutural cord in the preceding whorls ( Fig. 21 ); umbilicus narrow but deep, reaching first teleoconch whorls ( Figs. 31–32 ), bordered by 1–2 smooth, periumbilical spiral cords ( Figs. 4 , 33 ); interior sculptured with thin, closely spaced axial striae ( Figs. 31, 33 ).

Operculum ( Figs. 8, 10 ) golden yellow, corneous, circular, multispiral, with central nucleus; inner scar shallow, occupying ~1/2 of inner surface.

Head-foot ( Figs. 12–14 ). Total body length slightly exceeding half of body whorl length in preserved specimens. Head bulged, located approximately in middle region of head-foot. Snout (sn) wide, slightly flattened, slightly longer than wide, ~1/4 of head-foot length; anterior end simple, slightly flap-like, lacking papillae; lateral edges of snout bearing small lateral projection on each side ( Fig. 14 ). Mouth (mo) longitudinal, small, located centrally on ventral surface of snout, at distal end of pseudoproboscis ( Fig. 14 : pb), bearing a pair of closely-placed folds, running posteriorly up to ventral region of origin of snout, abruptly twisting leftward, dorso-posteriorly lying at left border between snout and foot. Cephalic tentacles (te) about as long as snout. Ommatophores (om) located on outer base of cephalic tentacles, length ~1/5 of tentacle length and almost same width of their base. Eyes large, dark, occupying most of distal region of ommatophores. Foot thick, occupying about half of total head-foot length, divided into mesopodium (fs) and epipodium (ep), surrounding lateral-dorsal region of mesopodium, far away from sole; anterior edge wider than remaining foot area; furrow of pedal gland very narrow, running along entire anterior edge of foot. Anterior third of epipodium relatively small and short, forming neck lobes ( Figs. 12–13 : nu); anterior end covered by ommatophore; remaining 2/3 of epipodium relatively low and thick, bearing 4 pairs of long, slender tentacles (et) inserted in its distal edge; each epipodial tentacle almost equidistantly distributed, similar-sized, distinctly separated from each other, apparently symmetrical on both sides. Pair of columellar muscles ( Fig. 12 : mc) completely fused with each other, thick, length ~1/4 whorl, fused with each other along median line at considerable length. Haemocoel ( Fig. 14 ) spanning ~1/2 of head-foot length, ~twice as long as wide; lacking any visceral structures; buccal mass occupying ~1/2 of inner haemocoel volume.

Mantle organs ( Fig. 16 ). Mantle border (mb) relatively thick, whitish, bearing small and closely spaced papillae. Pallial cavity ~3/4 whorl in length. Osphradium (os) node-like, relatively large, located at base of suspensory stalk of gill. Gill (gi) located approximately at the centre of the cavity, gradually expanding towards left posteriorly; length ~90% of pallial cavity length; projected anteriorly by suspensory stalk (gm) for ~1/5 of total gill length (ga). Anterior end of gill pointed, projecting outside cavity (ga). Both gill filaments relatively symmetrical, with larger filaments at middle gill level, gradually decreasing toward both sides. Ctenidial or efferent gill vessel (cv) about three times wider than afferent vessel, running along basal region of central axis of gill; directly connected to pericardium; gill separated from rectum for about 1/4 of pallial cavity width. No clear hypobranchial gland. Rectum (rt) narrow, slightly sinuous, ~1/2 of pallial cavity in length, running close along right edge. Anus narrow, long siphoned (~1/5 of rectum length), located halfway through length of cavity, posterior to mantle border.

Visceral mass ( Fig. 16 ). Located about 2.5–3 whorls posterior to pallial cavity, leaving some of apical shell whorls empty. Gonad (go) white, occupying ~2/3 of internal volume, located mainly in superior and external regions. Digestive gland (dg) beige, occupying regions close to columella; thicker around stomach. Stomach located close to posterior end of pallial cavity, occupying ~1/3 of local volume, ~0.15 whorl long, somewhat fusiform, slightly flattened. Reno-pericardial structures as anterior end, encroaching pallial roof.

Circulatory and excretory systems ( Fig. 16 ). Pericardium (pc) not seen in detail due to preservation issues; relatively small, located between pallial cavity and visceral mass, just posterior to left kidney, close to median line, slightly dislocated to left. Left kidney (kl) ~3-times longer than right kidney (kr), white, solid, simple. Nephrostome (ne) at anterior end of kidneys, preceded by a short hollow stalk.

Digestive system ( Figs. 11 , 14–17, 19–20 ). Oral tube ( Fig. 15 : ot) with ~1/3 of odontophore length, wide, with relatively thick muscular walls. Jaw and peribuccal muscles ( Fig. 15 : mj) very thick, originating laterally and ventrally at inner surface of mouth, close to median line, running divergently towards posterior and lateral regions, inserting in ventral surface of odontophore; additionally, also inserting in narrow region of middle level on ventral side of anterior odontophore cartilages ( Fig. 20 : mj). Odontophore (od) occupying ~1/4 haemocoel length. Odontophore muscles ( Figs. 19–20 ): m1, series of small muscles connecting buccal mass to adjacent inner surface of snout and haemocoel; m1l, pair of small lateral protractors ( Fig. 15 ), originating on lateral middle wall of snout, running towards anterior region, inserting in lateral-posterior region of odontophore; pair of buccal mass retractors absent; m4, broad pair of dorsal tensor muscles of radula and subradular membrane, originating part in anterior cartilages, along their ventral surfaces at some distance from median line, and part in posterior cartilages, on their posterior and lateral surfaces, surrounding lateral and ventral surfaces of anterior cartilages, inserting along subradular membrane, in its dorsal region exposed inside buccal cavity, with a portion in radular ribbon in region preceding buccal cavity; m5, pair of small auxiliary dorsal tensor muscles of radula, originating on ventral surface of posterior cartilages, running towards dorsal and medial regions along ~1/5 of odontophore length, inserting in radular ribbon in region preceding buccal cavity; m6, horizontal muscle, uniting both anterior cartilages along ~half their ventral edge (just posterior to fusion of cartilages), on their external surface; m6a, secondary horizontal muscle, length ~1/10 odontophore’s length, located at middle level between posterior end of m6 and that of posterior cartilage; m8, pair of broad approximators of cartilages, originating in anterior cartilages in a small area on their lateral surface, posterior to insertion of mj, running towards posterior region, decreasing gradually, inserting in middle region of anterior surface of posterior cartilages; m10, small pair of odontophore protractor muscles ( Fig. 15 ), originating at middle level of ventral surface of oral tube, running towards posterior region along ~1/4 of odontophore length, inserting in anterior-ventral region of odontophore; m11, pair of narrow and thin ventral tensor muscles of radula ( Fig. 20 ), originating at middle region of ventral surface of posterior cartilage, separated from each other close to median line, running anteriorly covering m6 and m8, inserting in distal edge of subradular membrane at some distance beyond it towards radular ribbon, along the inner surface.

Jaw plates ( Figs. 11 , 17 : jw). Thick, barely triangular; cutting edge anterior, occupying most of dorsal surface of buccal cavity; separated from each other by a narrow space; central projection of jaw (ja) well-developed. Pair of dorsal folds ( Fig. 17 : df) initiating just posterior to jaw plates, fused with each other, encircling an area equivalent to jaws, having a distal edge wider than their base. Salivary glands absent. Anterior esophagus relatively wide, inner surface bearing a pair of tall and narrow folds ( Fig. 17 : ef) as a continuation of dorsal folds, producing wide dorsal furrow. Esophageal crop ( Figs. 15, 17 : eg) occupying central region of esophagus, spanning along ~1/3 of its length; pair of longitudinal folds as continuation from those of anterior esophagus (ef), remaining area totally covered by small papillae; each papilla short, separated from each other by interspaces equivalent to their respective size, tip rounded. Pair of esophageal folds (ef) disappearing after crop; posterior esophagus with simple, smooth inner surface. Stomach ( Fig. 16 : st) fusiform, location and size described above; inner surface smooth; single duct to digestive glans (dd) located close to intestinal origin; stomach tapering gradually both at esophageal insertion and intestinal origin. Rectum and anus described above (pallial organs).

Non-muscular odontophore structures ( Figs. 19–20 ). oc, pair of anterior odontophore cartilages, ~4-times as long as wide, flat, anterior and posterior ends rounded, about same length as odontophore; fused with its respective pair at the first ~1/4 of anterior region of ventral edge ( Fig. 19 : of); po, small pair of posterior odontophore cartilages, antero-posteriorly short, length ~1/10 of anterior cartilages length, ~2/3 their width; located in posterior region, slightly lateral side of anterior cartilages, its outer side partially fused with anterior cartilages ( Fig. 20 : po); br, subradular membrane, covering most of exposed portion of odontophore in buccal cavity ( Fig. 19 ); sc, subradular cartilage, maintaining radular ribbon and expanding in buccal cavity beyond radula, covering about half of exposed portion of subradular membrane ( Fig. 19 ). Radular sac ( Figs. 15, 17 : rs) wide, projecting beyond posterior side of odontophore for approximately the same length the odontophore itself. Radular nucleus (rn) bifid, divided in the middle by a furrow.

Radula ( Figs. 24–29 ). Rachidian occupying ~15% of radula width, ~twice as long as wide; base rectangular, with abrupt notch preceding cutting edge ( Fig. 28 ); cutting edge ~half of tooth height, strongly curved, triangular, pointed tip angle ~25° ( Figs. 26, 29 ); ~10 pairs of secondary cusps along lateral border of cutting edge; each secondary cusp small, narrow, ~4-times longer than tall, tip sharply pointed, separated from each other by space equivalent to their basal width. Lateral teeth five pairs in number. Similar shape as rachidian, except for having ~1/3 of its width and being slightly curved medially; apical angle ~10° ( Figs. 25, 26, 29 ). Marginal teeth ~25 pairs, medial teeth slightly broader (as wide as lateral teeth), gradually becoming narrower towards lateral ends of radula; innermost marginal tooth with 4 large, wide cusps in subapical region of inner edge and series of minute marginal cusps along entire outer edge ( Figs. 25, 26 ), 25~ times as tall as wide; second innermost tooth with 8–10 strong, thin cusps in subapical region of inner edge ( Fig. 27 ) and series of minute marginal cusps along entire outer edge ( Fig 27 ), ~25 times as tall as wide; remaining marginal teeth as narrower versions of preceding marginal tooth; outermost teeth bearing taller, filiform secondary cusps ( Figs. 27, 29 ). Row of radular teeth clearly arched, with no signs of asymmetry.

Genital system. Gonad described above, no additional genital structure detected.

Central nervous system ( Figs. 15, 18 ). Nerve ring surrounding middle level of buccal mass ( Fig. 15 ); pair of pedal ganglia located just posterior to ventral base of snout, encased inside pedal musculature ( Fig. 14 : nr). Cerebral ganglia (ce) broad, rather flattened, located in lateral region of buccal mass ( Fig. 15 ); size of each ganglion equivalent to ~1/15 of that of buccal mass. Cerebral commissure narrow and long (~½ buccal mass width). Pleural and pedal ganglia (gp) hard to distinguish from each other; pedal ganglia widely connected to each other close do median line; each pedal ganglion with about same size as cerebral ganglion, relatively cylindrical. Cerebro-pleural and cerebro-pedal connectives relatively long, left connectives (right in Fig. 18 ) slightly shorter than right connectives. Statocysts (sy) small (size ~1/12 of each pleuro-pedal ganglion size), located side by side and close to each other; bearing several internal statoconia. Pair of buccal ganglia well-developed and individualized ( Figs. 15, 17 : bg), located at intersection between odontophore and esophageal origin, with each ganglion relatively separated from each other, size ~1/10 of cerebral ganglion size.

Distribution. Known only from type locality.

Habitat. Coralline bottoms, from 60 m (live specimens) to 260 m (empty shells only).

Etymology. The specific name is from Latin mel (“honey”) + - ifer (“-bearing”), an allusion to the honey yellow coloration of the shell’s apex and cords, and also to the honeycomb-like sculpture of the protoconch.

Measurements (in mm): Holotype, 6.75 whorls, H = 7.42, D = 6.13; Paratype MZSP 55522 #1 ( Figs 6-8 ), 5.75 whorls, H = 5.00, D = 4.60; Paratype MZSP 67310 ( Fig. 5 ), 7.25 whorls, H = 9.58, D = 8.13; Paratype MZSP 70308, 5 whorls, H = 4.50, D = 4.10; Paratype MZSP 90268 ( Figs. 21–23 ), 5.5 whorls, H = 4.80, D = 4.30.

Figures

FIGURES 1–11. Calliostoma melliferum shells, operculum and jaw; 1. Holotype MZSP 53718, apertural view (H = 7.42 mm); 2. same, apical view (D = 6.13 mm); 3. same, abapertural view; 4. same, umbilical view. 5. Paratype MZSP 67310, apertural view (H = 9.58 mm, D = 8.13 mm). 6–8. Paratype MZSP 55522 shell with soft parts; 6. whole specimen, left lateral view (H = 5.0 mm); 7. same, apical view; 8. same, apertural view (D = 4.6 mm); 9. Holotype, protoconch detail (scale = 0.2 mm). 10. Paratype MZSP 55522 operculum; 11. same, jaw plates, ventral view (scales = 0.5 mm).

FIGURES 12–20. Anatomy of Calliostoma melliferum; 12. head-foot, right view, anterior portion of mantle also shown; 13. same, left view; 14. head and haemocoel, ventral view, foot and columellar muscle removed; 15. foregut and nerve ring, right view; 16. pallial cavity and visceral mass, ventral view, layer of digestive gland ventral to stomach removed; 17. foregut, ventral view, longitudinally opened, odontophore deflected to right; 18. nerve ring, ventral view; 19. odontophore, dorsal view, first layer of membranes and muscles removed, both cartilages slightly deflected; 20. same, ventral view, anterior region of m4 and br removed, right-anterior portion of m11 showing its topology (scales = 1 mm).

FIGURES 21–29. Calliostoma melliferum in SEM. 21. Paratype MZSP 90268, apertural view (D = 4.3 mm); 22. same, apical view (H = 4.8 mm); 23. same, protoconch detail (scale = 0.2 mm). 24–29. Radulae in SEM: 24. wide view (scale = 50 µm); 25. same, detail of right half (scale= 30 µm); 26. same, detail of central region (scale = 10 µm); 27. same, detail of right marginal teeth (scale = 10 µm); 28. another specimen, wide view, (scale = 50 µm); 29. same, detail of central region (scale = 20 µm).

FIGURES 30–33. Calliostoma melliferum micro-computed tomography of Paratype MZSP 70308; 30. 3D reconstruction of shell, apertural view (H = 4.5 mm, D = 4.1 mm; voxel siZe = 8.8 µm); 31. same, longitudinal section showing the columellar axis, slightly lateral view; 32. same, longitudinal section showing the columellar axis, apertural view; 33. same, umbilical view.