Janthina umbilicata d'Orbigny, GNS RM 1841
Creators: name: Beu, Alan G.
Publisher: name: Zenodo
Year: 2017
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Janthinidae
Janthina
Janthina umbilicata

description: Janthina umbilicata d’Orbigny, 1841
Figs 2N, Q, 34D, G–H
Janthina globosa Blainville, 1822: 155 (Aug 1822; junior homonym of J. globosa Swainson, Jan 1822); Berry, 1958: 27; Keen, 1971: 442, fig. 687.
Janthina umbilicata d’Orbigny, 1841: 414, pl. 20, figs 22–23; Hedley, 1918: M62; Bennett, 1966: 43; Bosch et al., 1995: 111; Redfern, 2001: 75, pl. 36, figs 315A–B; Robertson, 2007a: 5, fig. 5; Spencer et al., 2009: 206.
Ianthina umbilicata d’Orbigny. – Reeve, 1858: pl. 5, figs 22a–b; Benson, 1860: 411; G. B. Sowerby II, 1882: 52, pl. 444, fig. 22; Martens, 1904: 143; Iredale, 1910: 71, 74; Oliver, 1915: 525; Laursen, 1953: 26, figs 26–28.
Janthina (Iodina) umbilicata D’Orbigny. – Mörch, 1860: 283; Rehder, 1980: 53, pl. 7, fig. 7; Okutani, 2000: 319, pl. 158, fig. 4.
Ianthina (Iodina) megastoma A. Adams, 1861: 403; Tryon, 1887: 38.
Janthina nitida A. Adams, 1869: 620, footnote; Tryon, 1887: 38.
Iodina nitida (A. Adams). – Iredale, 1929: 279; Iredale & McMichael, 1962: 49.
Janthina laeta Monterosato. – Pasteur-Humbert, 1962: 52, fig. 74 (misidentification as Amethistina laeta Monterosato, 1884, = J. globosa).
Iodina umbilicata d’Orbigny. – Habe, 1964: 48, pl. 14, fig. 8; Kuroda et al., 1971: 247, pl. 62, figs 13–14.
Janthina (Violetta) umbilicata d’Orbigny. – Higo et al., 1999: 174.
Janthina exigua Lamarck. – Luque, 2011: 209, text-fig. (misidentification).
Type material. Janthina umbilicata, four syntypes NHMUK 1854.12.4.403 (K. Way, NHMUK, pers. comm. 05 Feb 2013), from the “Atlantic Ocean”; recorded as present in the British Museum by Gray (1855: 36) and Reeve (1858: caption to pl. 5, figs 22a–b). Janthina globosa Blainville, location of any type material unknown. Because of confusion between the names Janthina globosa Swainson and J. globosa Blainville over many years, it is highly desirable to identify the name J. globosa Blainville unambiguously with the present species. The specimen illustrated as J. umbilicata by Reeve (1858: pl. 5, figs 22a–b), one of the syntypes of J. umbilicata in NHMUK 1854.12.4.403, is here designated the neotype of Janthina globosa Blainville, 1822. I. megastoma, from the Indian Ocean, no type material known; the specimen illustrated as J. umbilicata by Reeve (1858: pl. 5, figs 22a–b), one of the syntypes of J. umbilicata in NHMUK 1854.12.4.403, is here also designated the neotype of Janthina megastoma A. Adams, 1861.
No material in NHMUK is identified as Janthina nitida, but a board, NHMUK 1870.1.3.7, has nine specimens attached of J. umbilicata remaining wholly or partially intact out of an original 21 specimens. It is labelled “ J. balteata Reeve / N. Atlantic/ Mrs Knocker” and as Janthina nitida was described within a paper by Captain Knocker, this presumably includes the original syntypes described by A. Adams (K. Way, NHMUK, pers. comm. 05 Feb 2013). Knocker (1869: 616–619) presented a long table of specimens collected at numerous stations across the Pacific and Atlantic Oceans, recording J. nitida from 13 stations but, of course, it is now impossible to tell which specimens were collected at which stations. Knocker’s records are valuable, as he also records “ Ianthina –?”, “ I. fragilis ”, “ I. exigua ”, “ I. –? Light mauve colour, globular” (i.e., presumably J. pallida) and “ I. bicolor ”.
Other material examined. Present-day samples from Australia and New Zealand: Australia: Tasmania: (NMNZ M202862). New South Wales: Bermagui (AMS C40691, C40693); Port Stephens (NMV; AMS C91949); Putty Beach, Kilcare (AMS); Long Reef, Collaroy (AMS); Manly Beach, Sydney (AMS C32373, C56810); Cronulla (NMV); Botany Bay (AMS C83048). Queensland: Green I. (AMS C9856); Rocky Isle (AMS); Caloundra (AMS); Point Lookout, Stradbroke I. (AMS).
Kermadec Islands: Raoul I., Kermadec Is (NMNZ M00991, M202862, many).
New Zealand: 13 km N of Great King I., Three Kings Islands (NMNZ M146405, 1); Cape Maria van Diemen (M277743, 1); South Cavalli Seamount (M281315, 1); Ocean Beach, Whangarei Heads (M150840, 6); Waipu Cove, Northland (GNS RM4781, 2); Uretiti Beach, Bream Bay (M277742,1); Piha Beach,W Auckland (GNS RM5312, 8); SW of Waiuku, W coast Awhitu Peninsula, W Auckland (NMNZ M277700, 2; M277702, 4; M277704, many; M277706, 7; M277708, 3); Karioitahi Beach, W coast Awhitu Peninsula (M277710, 2); Papamoa Beach, Tauranga (M147404, 3); Boulder Bay, Motuhora I., Bay of Plenty (M042552, 1); Nukumaru Beach, W of Whanganui (GNS RM5627, 6).
Distribution. The writer is not aware of fossils of Janthina umbilicata. The 18 lots observed from the New Zealand region are listed above. Janthina umbilicata has not been recorded from New Zealand previously, other than in the list by Spencer et al. (2009: 206). The few records the writer is aware of from Australia are also listed above. There seem to be no records from the Northern Territory, WesternAustralia, South Australia or Victoria, and J. umbilicata and J. pallida seem to be largely mutually exclusive around Australia. The two species Janthina exigua and J. umbilicata seem to have closely similar distributions, J. umbilicata consistently being the less common, at least in the southern part of their range. Around New Zealand, small numbers of specimens occur in most large strandings of J. exigua, from Raoul Island, Kermadec Islands (where J. umbilicata is common) and from the Three Kings Islands to as far south as Whanganui, but the writer has seen no specimens of J. umbilicata from further south. Spencer (1982) reported that “seven J. umbilicata were found on Waitangi, Chatham Is.”, but although this is quite feasible, the writer has not seen specimens from the Chatham Islands. Few specimens have been observed south of the northeastern North Island warm-water region, extending from North Cape to East Cape. Because relatively few earlier authors have distinguished it from J. exigua, the range of J. umbilicata is poorly known, but it seems likely to occur with J. exigua throughout the world tropical and temperate ocean, although not extending quite as far into the southern temperate zone as J. exigua does. In contrast to its uncommonness around Australia and New Zealand, Savilov (1969: 398–399) reported that J. umbilicata was the most widespread and abundant Pacific Janthina species, collected at 333 of the 393 Vityaz stations where Janthina was collected. At many stations very large numbers were collected, up to 1000 specimens per 20 minutes of sampling. The largest specimens were 14 mm high. “Exceptionally large concentrations of mature individuals and young up to 4–5 mm long were observed in the central regions of … the N and S subtropical circulation in the California Current belt and in the eastern regions of the trade wind currents. Their quantity, notably that of mature animals, decreased considerably in the trade wind countercurrent area” (Savilov, 1969: 399).
Dimensions. See Table 10.
Diagnosis. Small, few specimens over 20 mm high; spire moderately tall, whorls evenly and strongly convex, suture deeply impressed; sinus occupying entire height of outer lip, deep, sharply V-shaped, with apex in centre of lip. Sculpture weak, of very fine, low, closely spaced, silky-looking, commarginal axial ridgelets over entire teleoconch surface, angulated in conformity with sinus; c. 30–40 µm apart at periphery. Most specimens deep, intense violet; a few paler, particularly large ones. Closely resembling J. exigua in all characters other than its much finer, lower axial sculpture and most specimens being slightly shorter. Lays ovate-triangular egg capsules on underside of float.
Remarks. Janthina umbilicata closely resembles J. exigua, and the two have been confused in several Australian and New Zealand collections. Besides a slightly shorter spire in most specimens of J. umbilicata, the main difference is that the axial sculpture is much lower, finer and more closely spaced in J. umbilicata than in J. exigua, producing a finely striate, silky-looking surface. As noted under J. exigua, measurement of the spacing of the axial ridges on SEM images showed that on the specimen of J. umbilicata (Fig. 34D) the ridges are only c. 30–40 µm apart at the periphery, whereas on the small specimen of J. exigua examined (Fig. 34B) the ridges are c. 120–200 µm apart at the periphery. The colour also is rather consistently deep bluish violet; a few paler specimens occur, particularly the largest ones seen, but less commonly than in samples of J. exigua. Few specimens show more than a very slight umbilical chink, as the inner lip is expanded slightly to cover the umbilicus in most adult specimens of this as in all other Janthina species, and the epithet “umbilicata” is no more appropriate for this species than for any other. The radular teeth (Laursen, 1953: fig. 28) are similar to those of J. exigua, although slightly shorter, and are moderately long and strongly hooked for a Janthina species. Rather strangely, this species was not mentioned, even in synonymy lists, by Küster (1868). Iredale (1910: 74) described J. umbilicata as “It has the form of exigua, Lam., but, being destitute of the rough sculpture of that shell, has a shiny appearance …”, and pointed out that d’Orbigny (1841: 414) distinguished this species carefully from J. exigua. Living specimens from northern New South Wales illustrated in colour on his web page by Riek (2017; Fig. 5C) have a long, narrow float identical to that of J. exigua. The attached egg capsules are pale pink, as in J. globosa.
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 196-197, DOI: 10.3853/j.2201-4349.69.2017.1666, http://zenodo.org/record/4677010