Janthina exigua Lamarck, GNS RM 1816
Creators: name: Beu, Alan G.
Publisher: name: Zenodo
Year: 2017
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Janthinidae
Janthina
Janthina exigua

description: Janthina exigua Lamarck, 1816
Figs 2M, O, 34A–C, E–F
Janthina exigua Lamarck, 1816, “Liste des objets”: 12, pl. 456, figs 2a–b; Eschscholtz, 1825: column 737; Gray, 1827: 495; Deshayes, 1843: 5; Gray, 1843: 241; Benson, 1860: 40; Küster, 1868: 7, pl. 2, figs 6–7; Monterosato, 1878: 95; Hutton, 1882: 128, pl. 14, fig. G (radula); Hutton, 1904: 80; Moss 1908: 28, pl. 7, fig. 1; Suter, 1913: 299, pl. 44, fig. 12; Oliver, 1915: 525; Bucknill, 1924: 50, pl. 19, fig. 4; Finlay, 1928: 246; Powell, 1937: 74, pl. 10, fig. 30; Mermod, 1953: 201, figs 200.1–2; PasteurHumbert, 1962: 52, fig. 72; Bennett, 1966: 41, pl. 9, fig. 2; Morton & Miller, 1968: 472, fig. 175.5; Cernohorsky, 1972: 198, pl. 56, fig. 10; Powell, 1976: 107, pl. 17, fig. 30: Kay, 1979: 158, fig. 55C; Powell, 1979: 254, pl. 48, fig. 21; Fretter & Graham, 1982: 394, fig. 281; Kilburn & Rippey, 1982: 79, pl. 11, fig. 19; Wells & Bryce, 1986: 60, fig. 153; Wilson, 1993: 281, pl. 44, figs 37a–b; Giannuzzi-Savelli et al., 1999: 52, 53, figs 94a–d, 95a–b; Smith, 1998: 813, figs 15.151C, G; Morley, 2004: 102; Robertson, 2007a: 5, fig. 1; Beu & Marshall, 2008: 285; Poppe, 2008: 722, pl. 306, fig. 1; Spencer et al., 2009: 206; Raven & Bracegirdle, 2010: 27, text-fig.; Willan et al., 2010: 385, text-fig.; Grove, 2011: 40, pl. 18, fig. 9; Severns, 2011: 198, pl. 82, fig. 1; Hernández et al., 2011: 97, figs 30A–D.
Ianthina exigua.– G. B. Sowerby I, 1822: 2nd Ianthina page, pl. 191, figs 2–3; Bronn, 1826: 328; d’Orbigny, 1841: 414; Reeve, 1842: 145, pl. 205, figs 2–3 (repeat of Sowerby’s 1822 figs); d’Orbigny, 1846: 84; Forbes & Hanley, 1853, vol. 2: 555, pl. 69, figs 8–9; H.Adams & A.Adams, 1854: 87; Reeve, 1858: pl. 5, figs 21a–b; Chenu, 1859: 118, fig. 519; Benson, 1860: 408; Angas, 1865: 190; Angas, 1867: 231; Hutton, 1873a: 6; Martens, 1873: 39; Tenison Woods, 1878: 43; Hutton, 1880: 71; G. B. Sowerby II, 1882: 51, pl. 444, figs 23–24; Watson, 1886: 134; Tryon, 1887: 37, pl. 10, figs 17–22; Whitelegge, 1889: 262; Locard, 1898: 4; Pritchard & Gatliff, 1900: 140; Tate & May, 1901: 407; Martens, 1904: 143; Verco, 1908: 9; Iredale, 1910: 71; Macpherson & Chapple, 1951: 124; Laursen, 1953: 22, figs 22–24; Macpherson, 1958: 33, pl. 29, fig. 4; Macpherson & Gabriel, 1962: 119, fig. 146.
Janthina incisa Philippi, 1849: 149; H.Adams & A. Adams, 1854: 87; Tryon, 1887: 38.
Ianthina nana J. E. Gray, 1850: 9, 101 (caption to M. E. Gray, 1842: pl. 48, figs 3–4).
Ianthina incisa Philippi. – H. Adams & A. Adams, 1854: 87.
Ianthina bifida “Nuttall in Jay” Reeve, 1858: pl. 5, figs 25a–b.
Janthina capreolata Montrouzier, 1860: 114, pl. 11, fig. 4; Hedley, 1918: M61; May, 1921: 63; May, 1923: pl. 19, fig. 4; Fischer-Piette, 1950: 18; Allan, 1950: 95, text-fig. 22.4.
Janthina (Janthina) nana Gray. – Mörch, 1860: 281.
Janthina (Iodina) exigua Lamarck. – Mörch, 1860: 282; Powell, 1946: 77, pl. 10, fig. 30; Powell, 1957: 98, pl. 10, fig. 30; Powell, 1962: 91, pl. 10, fig. 30.
Janthina (Iodina) capreolata Montrouzier. – Mörch, 1860: 283.
Janthina (Iodina) bifida Nuttall. – Mörch, 1860: 283.
Ianthina vinsoni Deshayes, 1863: 94, pl. 11, figs 9–11.
Jodina exigua (Lamarck). – Monterosato, 1884: 106.
Janthina courcellei Mabille & Rochebrune in Rochebrune & Mabille, 1889: 45, pl. 6, figs 3a–b [courcelli in text, courcellei in caption; the latter adopted by Rosenberg (Malacolog 4.1.1)]; Forcelli, 2000: 82, original illus. copied; Petit, 2010: 48.
Janthina (Jodina) exigua Lamarck. – Thiele, 1929: 225, fig. 228; Abbott, 1974: 113, col. pl. 3, fig. 1181; Rios, 1994: 102, pl. 33, fig. 416.
Ianthina capreolata Montrouzier. – Cotton, 1932: 537; Cotton & Godfrey, 1932: 36; Cotton & Godfrey, 1938: 16; Kershaw, 1955: 312; Cotton, 1959: 376.
Iodina capreolata (Montrouzier). – Iredale & McMichael, 1962: 49.
Janthina (Violetta) exigua Lamarck. – Higo et al., 1999: 173.
Type material. Janthina exigua, 3 syntypes MHNG 1094/80 examined, now catalogued as MHNG-INVE 51377, without locality; all are conspecific and agree with Laursen’s (1953) and all later interpretations of J. exigua. However, as with J. communis, Rosalie de Lamarck’s annotation on Lamarck’s copy of Animaux sans vertèbres states that there is only one specimen in Lamarck’s collection, so at least two and conceivably all three of these specimens are not original syntypes, although it is not possible to determine which is (Y. Finet, MHNG pers. comm. 27 Sep 2012). Two of the syntypes were illustrated by Mermod (1953: 201, figs 200.1–2), who described their angulated axial ridges commarginal with the mid-whorl sinus, and commented on the difficulty of matching any of them with the poor drawings in Lamarck (1816: pl. 456, figs 2a–b). The writer is not aware of the location of any type material of Janthina incisa, from Senegal; possibly in Philippi’s collection in Museo Nacional de Historia Natural, Santiago, not available for consultation, so a new type is not designated here.
The term “aucta” in G. B. Sowerby I’s (1822: second Ianthina p., pl. 191, fig. 3) caption to his second illustrated specimen of Janthina exigua does not constitute the proposal of a species-group name, but indicates that the illustration is enlarged. In an identical case, Petit (2009: 192, taxa note 27) stated that “The position taken here is that “ aucta ” is a descriptive term (= enlarged) and not an available name”. The drawings in Reeve (1841 –1842, vol. 2: pl. 205) are republications of the illustrations in G. B. Sowerby I (1822: pl. 191), and the term “aucta” appears in Reeve (1841 –1842: pl. 205) also, at the bottom edge of the plate.
Janthina nana J. E. Gray (1850: 9, 101; caption to M. E. Gray 1842: pl. 48, figs 3–4) refers to an illustration by “Quoy, Voy. Astrol. t. 29, f. 5, 6”, which shows a crudely drawn specimen of J. exigua from the Atlantic Ocean. Quoy & Gaimard (1833: caption to pl. 29) identified this specimen with the vernacular name “Janthine naine”, as pointed out by Mörch (1860: 281; as “nain”, sic), so Gray merely Latinized Quoy & Gaimard’s species name. Lamarck (1922: 206) earlier provided J. exigua with the vernacular name “Janthine naine”, so Quoy & Gaimard were repeating Lamarck’s vernacular name. The specimen of J. exigua illustrated by Quoy & Gaimard (1833, pl. 29, figs 5–6) is the holotype of J. nana. However, this specimen is not recognisable in MNHN (P. Bouchet, MNHN, pers. comm. 5 Apr 2016), so the largest syntype of J. exigua in MHNG-INVE51377 is here designated the neotype of Janthina nana Gray, 1850. Petit (2012: 76) apparently was not aware of the publication of the name Janthina nana by Gray (1850: 101) and attributed the name to Couffon & Surrault (1909: 57), where it is a nomen nudum.
Janthina capreolata, two lots of two specimens each in MNHN formerly were considered syntypes (Fischer-Piette 1950: 18), but as Montrouzier (1860: 114) stated that the types were in “ma collection Musée de Bordeaux, 4 ex. ”, the MNHN specimens are not syntypes; 3 remaining syntypes MHNB2004.TY.160.0; photographs of MHNB syntypes sent 21 Sep 2012 (pers. comm. L. Charles, MHNB, and V. Héros, MNHN); from Art Island, New Caledonia. Janthina vinsoni, no type material in either MNHN or Université Lyon-1, where most of Deshayes’s collection is stored (V. Héros, MNHN, pers. comm. 21 Sep 2012; E. Robert, Université Lyon-1, pers. comm. 02 Oct 2012), location unknown; from Réunion. Janthina courcellei, empty box in typothèque, MNHN, labeled “type perdu”, apparently long lost; from Orange Bay, Tierra del Fuego. The largest syntype of Janthina exigua, MHNG-INVE 51377, designated above as the neotype of J. nana, is here also designated the neotype of both Janthina vinsoni Deshayes, 1863 and Janthina courcellei Mabille & Rochbrune, 1889, in order to identify these names permanently with the present species.
Other material examined. Present-day samples from Australia and New Zealand: Australia: Western Australia: Cable Beach, Broome (NMV); Duke of Orleans Bay (AMS); Bunbury (AMS); Leighton (WAM); Point Peron,Fremantle (WAM.699/70-38, WAM.366/40, WAM.589/91-38); City Beach, Perth (AMS); Esperance (SAM, NMV); King George Sound (SAM); Albany (SAM); Rottnest I. (SAM); 300 fms, 120 mi W of Eucla (SAM); Ellensbrook Beach (SAM). South Australia: Coorong (SAM); Grange (SAM); Edithburgh (SAM); 165, 240 & 550 m, off Cape Jaffa (SAM); 190 m, 56 km SW of Neptune I. (SAM); Victoria: Portland (NMV); Mordialloc (NMV); Mallacoota (NMV, AMS); Warnambool (NMV); Curdie’s Inlet (NMV); New South Wales: Newcastle (SAM); Cronulla (NMV); Port Stephens (NMV); Bondi, Sydney (NMV); Curl Curl Beach, Sydney (AMS); Collaroy Beach, Sydney (AMS); C83049, Botany Bay (AMS); Terrigal (AMS); C67422, Maroubra Beach (AMS); Stockton Beach, Port Stephens (AMS); C40693, South Ocean Beach,Bermagui (AMS); C11240, Wollongong (AMS); Tasmania: Tasmania (WAM, NMV, NMNZ);C12904, Flinders I. (AMS); Queensland: Point Lookout, Stradbroke I. (AMS).
Lord Howe Island: C59571 (AMS); Norfolk Island: C59409 (AMS); Kermadec Islands: Raoul I. (NMV; C36654, AMS; NMNZ M202863, 12; M272663, many).
New Zealand: NW of Three Kings Islands (NMNZ M109274, 2; M308654, 8); Middlesex Bank, NW of Three Kings Islands (NMNZ M112779, 1); 37–39 km SW of Great King, Three Kings Islands (NMNZ M094277, 1; M308655, 5; M308656, 1); W Norfolk Ridge, W of Cape Reinga (NMNZ M171012, 1; M171907, 3; M172329, 17); Cape Maria van Diemen (AWM 30649); Spirits Bay (NMNZ M020279, 3); Ahipara Beach (GNS Suter colln, S2388, 7); Bayleys Beach, Dargaville (NMNZ M299995, 100); Cavalli Islands, Whangaroa (NMNZ M308653, 1); Maro Tiri I., Hen and Chickens Islands (GNS RM2672, 2); Bream Head, Whangarei (AWM 18335); Leigh, N Auckland (NMNZ M087156, 20); Anawhata Beach, W Auckland (GNS RM5864, 60; RM6014, 5); Bethells Beach, W Auckland (NMNZ M016291, 12; M087157, 500; M308658, 40); Piha Beach, W Auckland (GNS RM5311, 100; NMNZ M087158, 300); Muriwai Beach, W Auckland (GNS RM332, 20; AWM 18136; NMNZ M02762, 50; M087159, 1000; M145116, 100); Whatipu, Manukau Harbour,W Auckland (NMNZ M087155, 20); Mokohinau Islands (GNS Suter colln, S1658, 7); Kaitoke Beach, Great Barrier I. (NMNZ M087153, 5); W coast Awhitu Peninsula, SW of Waiuku, W Auckland (NMNZ M277699, 5; M277701, many; M277703, many; M277705, 1; M277707, 1; M277709, many; M277740, 3; M277741, 4); Matakana I., Bay of Plenty (AWM 42757); Papamoa Beach, Bay of Plenty (NMNZ M120141, 4); Boulder Bay, Motuhora I., Whakatane (NMNZ M 033166, 20); Opotiki, Bay of Plenty (GNS RM331, 4); Te Kaha, Bay of Plenty (NMNZ M040065, 6); E of Te Araroa, East Cape (GNS RM4899, 3); Wainui Beach, Gisborne (NMNZ M308657, 4); Waimarama, Hawke’s Bay (GNS RM334, 11); Nukumaru Beach, Whanganui (GNS RM5626, 100); Whanganui (GNS RM4053, 1); Otaki Beach, W Wellington (AWM 18344); Waitarere Beach, Levin (GNS RM2967, 42; NMNZ M011127, 11); Waikanae Beach, W Wellington (NMNZ M01154, 15; M018897, 50; M160084, 100; M303125, 40; M308027, 400; GNS RM5852, 2360; RM5845, 300; RM5894, 100); Pukerua Bay, W Wellington (NMNZ M02760, 30); Porirua Harbour mouth (GNS RM4041, 1); Titahi Bay, W Wellington (NMNZ M02759, 20; M06945, 50); Lyall Bay, Wellington (NMNZ M087154, 7); Ocean Beach, Farewell Spit (NMNZ M023154, 9); Carters Beach, Westport (GNS RM5318, 20); Mason Bay, Stewart I. (AWM; NMNZ M019480, 15; M020278, 3); Chatham Islands (AWM 16405; NMNZ M03853, 2; M05090, 3; GNS Suter colln, S2387, 8); Kaingaroa Beach, Chatham Islands (NMNZ M110413, 8); Te Whakaru, Chatham Islands (NMNZ M013073, 2); beach NW coast of Mangere I., Chatham Islands (GNS RM6013, 42).
Distribution. The writer is not aware of fossils of Janthina exigua. Janthina exigua is probably the most widely recorded of all living Janthina species. However, its distribution provides some surprises. It is the most common Janthina species in most beach strandings around New Zealand and southern Australia, whereas it is one of the least common species in the North Pacific, although it is among species recorded from Japan (as far north as Boso Peninsula, Honshu; Higo et al. 1999: 173). There seem to be few records from northern Australia, including Queensland. Savilov (1969: 398–403) described the distribution of Janthina species at 393 stations where Janthina was sampled by RV Vityaz in the Pacific. J. exigua was collected at only four of these 393 stations, all near the North Island of New Zealand. However, Savilov also noted that Laursen (1953) recorded J. exigua from further north in the South Pacific, to 10°S, from New Caledonia east to Tahiti, in the southern Indian Ocean, and near Hawaii, and that Fowler (1948, 1949) and Wilson & Wilson (1956) recorded J. exigua from the southern coasts of Britain. In contrast to all these observations, Benson (1860: 406) noted that “ I. exigua was the most widely distributed species met with” during a voyage from England to Calcutta in the Malcolm, correctly pointing out that I. capreolata Montrouzier is not separable. He first observed specimens two days before reaching Madeira (Benson, 1860: 405), and then observed specimens almost throughout the voyage. Benson’s careful distinctions between subtle forms, his comments on the synonymy of Reeve’s and other species names, and his references to publications by Coates (1825), Reeve (1858) and Mörch (1860) show that his observations are very reliable. Janthina exigua occurs throughout the world tropical and temperate ocean, as far south as Orange Bay, Tierra del Fuego (type locality of J. courcellei) and Mason Bay, Stewart Island, southern New Zealand (listed above), but most reporters have described it as less common than other species in the northern Pacific and Indian Oceans.
Dimensions. See Table 8.
Diagnosis. Small, few specimens over 20 mm high; spire tallest of all Janthina species, but height variable; whorls evenly and strongly convex, suture deeply impressed; sculpture of prominent, thin, closely spaced, commarginal axial ridgelets over entire teleoconch, c. 0.2–0.5 mm apart at periphery of large specimens, angulated in conformity with sinus. Sinus occupying entire height of outer lip, deep, sharply V-shaped, apex in centre of lip. Most specimens deep, intense violet, some paler, very few with pinkish tinge. Lays ovate-triangular egg capsules on underside of float.
Remarks. The small, deep violet species Janthina exigua is the most coarsely sculptured of living Janthina species, the only one with obvious, coarse axial ridges up to c. 0.5 mm apart over the entire exterior of large shells, resembling the axial sculpture of J. typica, J. chavani and J. krejcii sp. nov. and of a finely sculptured Epitonium species. Measurement of the spacing of the axial ridges on SEM images (Fig. 34B) showed that on this small specimen of J. exigua the ridges are c. 120–200 µm apart at the periphery, whereas on the specimen of J. umbilicata examined by SEM (Fig. 34D) the ridges are only c. 30–40 µm apart at the periphery. The axial lamellae of J. exigua also are considerably higher and more prominent than those of J. umbilicata. The apex of the outer lip sinus is at the periphery, i.e., in the centre of teleoconch whorls, and leaves a clear trace of the sinus apex around the centre of all whorls of tall-spired specimens. The consistently deep coloration is also a species character, the colour varying from deep reddish violet to (much more commonly) deep bluish violet, with a narrow paler zone beneath the suture in a few specimens. The radular teeth (Laursen, 1953: fig. 24) are similar to those of J. umbilicata, but have shorter bases, and some are less strongly hooked than those of J. umbilicata. The float (e.g., Laursen, 1953: fig. 1; Bennett, 1966: pl. 9, fig. 2) is proportionally the longest and narrowest of all Janthina species, although a specimen photographed alive in northern New South Wales by Denis Riek (Brunswick Heads, NSW; Fig. 5C) demonstrates that the float of J. umbilicata is indistinguishable from that of J. exigua. The distinctiveness of J. exigua is attested by the remarkably few synonyms it has received in this vastly over-named genus.
Time range. No fossil record; living only.
description: Published as part of Beu, Alan G., 2017, Evolution of Janthina and Recluzia (Mollusca: Gastropoda: Epitoniidae), pp. 119-222 in Records of the Australian Museum (Rec. Aust. Mus.) (Rec. Aust. Mus.) 69 (3) on pages 191-194, DOI: 10.3853/j.2201-4349.69.2017.1666, http://zenodo.org/record/4677010