Parminolia agapeta ( Melvill & Standen, 1896 )

Herbert, David G., 2024, The Umboniinae (Mollusca: Gastropoda: Trochidae) of New Caledonia, with descriptions of two new genera and eight new species, plus an additional new species from the Bismarck Sea, European Journal of Taxonomy 973, pp. 1-143 : 36-42

Parminolia agapeta ( Melvill & Standen, 1896)

Figs 18–20

Minolia agapeta Melvill & Standen, 1896: 312 , pl. 11 fig. 77. Type locality: Lifou, Loyalty Islands, New Caledonia (Hadfield).

Isanda (Parminolia) apicina – Ladd 1966 (non Monilea apicina Gould, 1861 ): 39, pl. 5 figs 1–2 (not 3–4 = holotype of Monilea apicina ); Miocene and Recent.

Material examined

Syntypes

NEW CALEDONIA • 1 specimen ( Fig. 18A–C ); Loyalty Islands, Lifou; MM.EE.3700 • 2 specimens; Loyalty Islands, Lifou; NMW.1955.158.00097 • 2 specimens; Loyalty Islands, Lifou; NMW.1955.158.00098 • 3 specimens; Loyalty Islands, Lifou; NHMUK 1897.1.22.137–139 .

Other material

NEW CALEDONIA – Grande Terre, Koumac • 3 specimens, living; Stn KD533; 20°32.2′ S, 164°05.5′ E; depth 11 m; 5 Nov. 2019; KOUMAC 2.3 leg.; sable blanc nu; MNHN • 10 specimens, living; Stn KD563; 20°33.4′ S, 164°06.3′ E; depth 5 m; 15 Nov. 2019; KOUMAC 2.3 leg.; sable blanc; MNHN • 1 specimen, dead; Stn KB636; 20°38.4′ S, 164°11′ E; depth 3 m; 11 Nov. 2019; KOUMAC 2.3 leg.; blocs et corail mort de tombant interne de récif barrière; MNHN • 5 specimens, living; Chenal de l’Infernet, Stn 1304; 20°38.6′ S, 164°13.2′ E; depth 12–15 m; Oct. 1993; Expédition Montrouzier leg.; sable gris, dalle; MNHN • 1 specimen, living; Stn KD568; 20°40.1′ S, 164°14.3′ E; depth 2 m; 16 Nov. 2019; KOUMAC 2.3 leg.; sable blanc et quelques débris coralliens; DNA voucher; MNHN- IM-2019-9358 • 1 specimen, dead; Chenal de la Passe de Koumac, Stn 1315; 20°40.7′ S, 164°14.7′ E; depth 66–87 m; Oct. 1993; Expédition Montrouzier leg.; sable coquillier vaseux; MNHN • 4 specimens, living; Stn KD560; 20°45.6′ S, 164°15.2′ E; depth 5–9 m; 14 Nov. 2019; KOUMAC 2.3 leg.; sable blanc et quelques algues brunes; MNHN • 1 specimen, dead; Stn KD559; 20°46′ S, 164°15.5′ E; depth 12–14 m; 14 Nov. 2019; KOUMAC 2.3 leg.; sable blanc; MNHN • 1 specimen, dead; Stn KD558; 20°43.7′ S, 164°15.9′ E; depth 6 m; 13 Nov. 2019; KOUMAC 2.3 leg.; petits blocs et débris coralliens; MNHN • 1 specimen, dead; around Plateau Karembé, Stn 1303; 20°37.7′ S, 164°15.9′ E; depth 0–8 m; Oct. 1993; Expédition Montrouzier leg.; sable vaseux, blocs; MNHN • 1 specimen, dead; Stn KB517; 20°37.6′ S, 164°17.3′ E; depth 0 m; 19 Nov. 2019; KOUMAC 2.3 leg.; sable, herbier et blocs coralliens morts; MNHN • 2 specimens, dead; Stn KD 552; 20°49.4′ S, 164°18.5′ E; depth 10–11 m; 13 Nov. 2019; KOUMAC 2.3 leg.; sable blanc; MNHN. – Grande Terre, Touho • 2 specimens, dead; surroundings of l’Îlot Ouao (=Î. Camille), Stn 1255; 20°43′ S, 165°08′ E; depth 11 m; Sep. 1993; Expédition Montrouzier leg.; sable, dômes détritiques; MNHN • 6 specimens, living; Grand Récif Mengalia, Stn 1245; 20°45.2′ S, 165°16.3′ E; depth 0 m; Sep. 1993; Expédition Montrouzier leg.; marée, platier, sable, herbiers; MNHN. – Grande Terre, Nouméa • 1 specimen, dead; Quatre Bancs de l’Ouest, Stn 1510; 22°26.5′ S, 166°18.35′ E; depth 0–1 m; 26 Oct. 2000; Cosel and Trondlé leg.; drague à main; MNHN • 17 specimens, dead; Grand Récif Aboré, Stn 1347; 22°23.6′ S, 166°20.1′ E; depth 10 m; 8 Oct. 1992; P. Bouchet leg.; vase sableuse sur dalle; MNHN • 1 specimen, dead; Île aux Goélands, Stn 1368; 22°24.3′ S, 166°20.7′ E; depth 10 m; 16 Apr. 1993; P. Bouchet leg.; fonds blancs; MNHN • 1 specimen, dead; Île aux Goélands ; 22°22.4′ S, 166°22.8′ E; depth 0–4 m; 1997–1999; Claude Berthault leg.; MNHN • 1 specimen, dead; Anse Vata ; 22°18.21′ S, 166°26.30′ E; depth 1–5 m; 12 Feb. 2002; Berthault leg.; MNHN • 15 specimens, living; Anse Vata ; 22°18.1′ S, 166°26.4′ E; depth 1–5 m; 1987–2007; Claude Berthault leg.; MNHN • 1 specimen, dead; Baie de Sainte Marie – Îlot Uéré ; 22°18.5′ S, 166°28.3′ E; depth 0–3 m; 1995-2003; Claude Berthault leg.; MNHN • 15 specimens; Île de Nou ; NMW.1955.158. – Loyalty Islands, Loyalty Ridge • 1 specimen, dead; Ride des Loyauté , Stn DW 431; 20°22′ S, 166°10′ E; depth 21 m; 18 Feb. 1989; NO Alis -MUSORSTOM 6 leg.; MNHN. – Loyalty Islands, Lifou • 2 specimens, dead; Baie du Santal, north of Cap Aimé Martin [= Acadro], Stn 1448; 20°45.8′ S, 167°01.6′ E; depth 20 m; 17 Nov. 2000; Atelier LIFOU 2000 leg.; aspirateur, fonds durs; MNHN • 5 specimens, living; Baie du Santal, north of Cap Aimé Martin [= Acadro], Stn 1450; 20°45.8′ S, 167°01.6′ E; depth 27–31 m; 17 Nov. 2000; Atelier LIFOU 2000 leg.; brossages; MNHN • 1 specimen, dead; Baie du Santal, Cap Aimé Martin [=Acadro], Stn 1441; 20°46.4′ S, 167°02′ E; depth 20 m; 13 Nov. 2000; Atelier LIFOU 2000 leg.; surplomb sciaphile; MNHN • 1 specimen, dead; Baie du Santal, between Cap Mandé and Cap Lefèvre [= Nem], Stn 1453; 20°54.6′ S, 167°02.1′ E; depth 21–30 m; 22 Nov. 2000; Atelier LIFOU 2000 leg.; tombant massif avec gorgones; MNHN • 6 specimens, living; Baie du Santal, Baie de Gaatcha, towards Cap Mandé , Stn 1424; 20°54.9′ S, 167°03′ E; depth 4 m; 15 Nov. 2000; Atelier LIFOU 2000 leg.; sable fin et algues photophiles sur dalle; MNHN • 1 specimen, dead; Baie du Santal, Baie de Gaatcha, Stn 1436; 20°55.5′ S, 167°04.2′ E; depth 20 m; 10 Nov. 2000; Atelier LIFOU 2000 leg.; patate corallienne sur tombant; MNHN • 60+ specimens, living; Baie du Santal, in front of landing beaches at Drueulu, Stn 1413; 20°55.3′ S, 167°05.0′ E; depth 3–10 m; 26 Nov. 2000; Atelier LIFOU 2000 leg.; fonds meubles; MNHN • 4 specimens, living; Baie du Santal, NE of Baie de Gaatcha, Stn 1444; 20°55′ S, 167°05.2′ E; depth 9–20 m; 26 Nov. 2000; Atelier LIFOU 2000 leg.; pente alternant zones caillouteuses “mortes” et passées sableuses grossières; MNHN • 2 specimens, living; Baie du Santal, in front of Huneté, Stn 1426; 20°45.9′S, 167°06.2′ E; depth 4–7 m; 20 Nov. 2000; Atelier LIFOU 2000 leg.; dalle et petites poches de séd.; MNHN • 5 specimens, dead; Baie du Santal, in front of Huneté, Stn 1414; 20°45.9′ S, 167°06.2′ E; depth 4–7 m; 20 Nov. 2000; Atelier LIFOU 2000 leg.; drague triangulaire; MNHN • 2 specimens, dead; Baie du Santal, W /SW of Pointe d’Easo, Stn 1430; 20°47.5′ S, 167°07.1′ E; depth 20–25 m; 9 Nov. 2000; Atelier LIFOU 2000 leg.; patates coralliennes, passées séd.; MNHN • 5 specimens, living; Baie du Santal, Baie d’Huneté, Stn 1425; 20°46.8′ S, 167°07.2′ E; depth 4–5 m; 17 Nov. 2000; Atelier LIFOU 2000 leg.; dalle avec couverture sed.; MNHN • 50+ specimens, living; Baie du Santal, in front of Peng, Stn 1423; 20°54′ S, 167°07.3′ E; depth 12 m; 14 Nov. 2000; Atelier LIFOU 2000 leg.; passées sableuses entre patates; MNHN • 6 specimens, living; Baie du Santal, small bay west of Pointe d’Easo, Stn 1422; 20°47.1′ S, 167°07.4′ E; depth 4 m; 25 Nov. 2000; Atelier LIFOU 2000 leg.; sable sur dalle, patates; MNHN • 1 specimen, dead; Baie du Santal, east of Pointe d’Easo, Stn 1418; 20°46.9′ S, 167°07.9′ E; depth 1–5 m; 25 Nov. 2000; Atelier LIFOU 2000 leg.; sable et herbier autour du wharf; MNHN • 12 specimens, living; Baie du Santal, between Îlot Huca Hutighé and coast, Stn 1421; 20°52.4′ S, 167°08.5′ E; depth 4 m; 26 Nov. 2000; Atelier LIFOU 2000 leg.; sable grossier sur dalle; MNHN • 6 specimens, living; Lifou, Baie du Santal, in front of Chépénéhé , Stn 1415; 20°47.1′ S, 167°09.1′ E; depth 3–7 m; 25 Nov. 2000; Atelier LIFOU 2000 leg.; sable; MNHN • 4 specimens, living; Baie du Santal, Pointe de Chépénéhé, Stn 1420; 20°47.7′ S, 167°09.4′ E; depth 4–5 m; 18 Nov. 2000; Atelier LIFOU 2000 leg.; dalle avec couverture séd.; MNHN • 1 specimen, dead; Baie du Santal, Pointe de Chépénéhé, Stn 1438; 20°47.7′ S, 167°09.4′ E; depth 6 m; 11 Nov. 2000; Atelier LIFOU 2000 leg.; tombant avec grandes passées sableuses; MNHN • 2 specimens, dead; Baie du Santal, in front of Kiki, Stn 1427; 20°47.6′ S, 167°10.2′ E; depth 10 m; 23 Nov. 2000; Atelier LIFOU 2000 leg.; sable grossier et coraux vivants au pied des patates; MNHN • 22 specimens, living; Baie du Santal, in front of Kiki, Stn 1411; 20°47.6′ S, 167°10.4′ E; depth 48 m; 23 Nov. 2000; Atelier LIFOU 2000 leg.; sable entre patates; MNHN .

KIRIBATI • 4 specimens, dead; Tarawa; Cox leg.; NMW.1955.158 .

Description ( Fig. 18 )

SHELL. Relatively small (adult shell diameter 4–5 mm) and stout, spire trochiform with indented suture; whorls weakly shouldered and weakly angled at periphery; base rounded with relatively narrow umbilicus. Sculpture of spiral cords, usually 4–5 on penultimate whorl, with finer spiral lirae on shoulder; a further cord level with abapical suture; shoulder cord and the one below it usually stronger and distinctly undulant, reminiscent of piped icing on a cake ( Fig. 19A ); peripheral cord also often undulant; cord intervals with close-set microscopic axial pliculae. Basal cords finer, more evenly sized and evenly spaced; peri-umbilical region sometimes with weak axial pliculae, more distinct in strongly sculpture specimens; umbilicus with a thickened cord just inside its rim, set off from remainder of base by a distinct furrow; a further low, broad funicle (sometimes indistinct) within umbilicus; aperture roundly quadrate; outer lip thick, internally smooth.

COLOUR. Pattern variable, but ground colour commonly whitish, mottled with shades of green/brown, or pink/red, often as subsutural blotches or flames and smaller peripheral spots; base usually with fewer markings, rarely with irregular axial flames. Occasional specimens with a pale pink wash above and below periphery ( Fig. 18I ). Apex normally whitish, but apical bulb of protoconch very occasionally dark.

PROTOCONCH ( Fig. 19B ). Typically umboniine, diameter ±170 µm; apical beak present and confluent with terminal lip; sculptured with subspiral threads toward periphery and near apical beak, crossed by transverse threads in region of apical bulb; terminal lip weakly convex.

OPERCULUM ( Fig. 19C–D ). Corneous, whorls relatively wide and growing edge moderately long; peripheral fringe narrow, not remaining evident on early whorls; surface lacking spiral microsculpture.

RADULA ( Fig. 19E–F ). Formula ∞+ (1) + 5 +1 +5 +(1) +∞, with ± 35 transverse rows of teeth; teeth of central field reduced, but base-plates remaining distinct; rachidian base-plate subquadrate with rounded anterior shoulders and a small rounded vestige of a shaft; base-plates of inner lateral teeth trigonal, pinched in anteriorly toward cusp vestige, outer margin rounded and expanded, overlapping outer neighbour; outer laterals more quadrate and elongate. Innermost marginal transitional, with trigonal base-plate and reduced shaft and cusp; other marginal teeth well developed with narrow shaft and strongly recurved cusp; cusps of inner series with an acuminate central denticle bearing 1–2 long slender basal denticles on both sides; marginals 3–10 with largest cusps; cusps progressively smaller thereafter.

EXTERNAL ANATOMY (from rehydrated specimens).Limited detail evident; inter-tentacular region(forehead) of moderate width, evidently with a thin transverse fold of tissue, pigmented with white, extending between the tentacles; snout prominent, subterminally papillate; eyestalks well developed, their tips expanded and containing large black eyes; left neck-lobe a rounded flap with digitate margin; right neck-lobe extensive, its margin entire and rolled to form a long exhalant siphon; four micropapillate epipodial tentacles on each side. Sides of foot with some whitish pigmentation, particularly the metapodium. Structure of ctenidium unclear, its tip appearing unattached.

Habitat

Mostly associated with white, sandy substrata and coralline debris on the inner side of the barrier reef; intertidal to a depth of 48 m (living specimens the same).

Distribution ( Fig. 20 )

Reliably known only from the New Caledonian marine ecoregion and northward to Kiribati and the Marshall Islands ( Ladd 1966, Miocene and Recent), but potentially more widely distributed under the name Parminolia apicina .

Remarks

The strength of the sculpture in P. agapeta exhibits considerable variation. In some specimens the spiral cords are relatively weak and scarcely undulant, in others they are strong and distinctly undulant. In occasional very strongly sculptured specimens the dips of the undulations align in prosocline furrows which extend around the periphery and onto the base, ending as peri-umbilical pliculae. These specimens closely resemble Gibbula vanwalleghemi Poppe, Tagaro & Dekker, 2006 from the Philippines. The latter is undoubtedly congeneric with P. agapeta and may prove to be a synonym thereof, but confirmation of such synonymy must await evidence from molecular data.

Under SEM ( Fig. 19B ), the microsculpture on the first teleoconch whorl is typically umboniine, comprising extremely fine, close-set axial threads. However, during the second whorl additional axial ribs develop, strengthening during the third whorl and rendering the spiral cords weakly granular at the intersections. On the fourth whorl the axial sculpture no longer appears as ribs but as flat-topped buttresses separated by narrow, deep clefts ( Fig. 19A ). These clefts are interrupted by the primary spiral cords. The type specimens were evidently collected as beached specimens and thus details of sculpture are worn.

Although Ladd (1966) followed Iredale in treating Minolia agapeta as a synonym of Monilea apicina , he noted that his Marshall Islands material differed from Gould’s type and this is evident in his illustrations. I believe Ladd’s Marshall Island material to be referable to Parminolia agapeta , rather than to Talopena apicina . The same may well apply to the majority of literature records of Monilea apicina and Parminolia apicina .

Monilea pusilla A. Adams, 1853 of unknown provenance is similar to Parminolia agapeta , but the holotype (NMHUK 1968101, H. Cuming Coll’n) has a strong carina-like cord at the shoulder on the second whorl and somewhat stronger axial sculpture on the early spire whorls. In addition, the umbilical funicle is narrower and more well defined, and the swelling at its termination at the base of the columella is less pronounced. In the absence of locality data for M. pusilla , these minor differences are difficult to evaluate, but the species clearly resembles P. agapeta closely and it is undoubtedly congeneric. I here provide the first illustration of the taxon ( Fig. 78A–C ).

Figures

Fig. 18. Parminolia agapeta (Melvill & Standen, 1896). A–C. Figured syntype of Minolia agapeta Melvill & Standen, 1896, diameter 4.7 mm (MM EE.3700). D–G. Koumac, Stn KD558, diameter 4.5 mm (MNHN).H. Koumac, Stn KD559, diameter 5.2 mm (MNHN).I. Koumac, Stn KD563, diameter 4.5 mm (MNHN). J–L. Nouméa, Anse Vata, diameter 4.5 mm (MNHN). M. Lifou, Stn 1423, diameter 4.0 mm (MNHN). N. Lifou, Stn 1423, diameter 4.2 mm (MNHN). O. High-spired specimen, Koumac, Stn, KD552, diameter 4.6 mm (MNHN).

Fig. 19. Parminolia agapeta (Melvill & Standen, 1896) (all MNHN). A. Detail of shell microsculpture, Koumac, Stn KB636. B. Protoconch, Koumac, Stn KD533. C–D. Operculum, Lifou, Stn 1423. E–F. Radula, Lifou, Stn 1423. Scale bars: A, C=0.5 mm; B= 50 µm; D = 100 µm; E–F =25 µm.

Fig. 20. Map showing the New Caledonian distribution of Parminolia agapeta (Melvill & Standen, 1896) in Grande Terre and the Loyalty Islands. Type locality (approximate) indicated in pink.

Fig. 78. Specimens examined and illustrated for comparison. A–C. Holotype of Monilea pusilla A. Adams, 1853, provenance unknown, H. Cuming Collection (NHMUK 1968101), height 3.2 mm, diameter 4.0 mm. Images courtesy of Kevin Webb, NHM Photo Unit. © The Trustees of the Natural History Museum, London. D–G. Topotype of Ethminolia probabilis Iredale, 1924, Two-fold Bay, New South Wales, Australia, diameter 5.0 mm (NMW.1955.158).H–K. Syntype of Minolia henniana Melvill, 1891, Magnetic Island, Queensland, Australia, diameter 4.3 mm (NMW.1955.150.00117).