Janthina pallida Thompson, 1840

Beu, Alan G., 2017, Evolution of Janthina and Recluzia (Mollusca: Gastropoda: Epitoniidae), Records of the Australian Museum (Rec. Aust. Mus.) 69 (3), pp. 119-222 : 194-196

Janthina pallida Thompson, 1840

Figs 2K–L , 5B

Janthina pallida Thompson, 1840: 96 , pl. 2, fig. 2 (under “ J. nitens ?”, name attributed to Harvey; tentatively a new species).

Janthina pallida Harvey. – Thorpe, 1844: 152; Küster, 1868: 5, pl. 1, fig. 5; Monterosato, 1878: 95; Locard, 1898: 2; Dall, 1908: 318.

Ianthina striolata A.Adams & Reeve, 1850: 54 , pl. 11, fig. 9; H. Adams & A. Adams, 1854: 87; Reeve, 1858: pl. 5, figs 24a–b; Hedley, 1900: 141; Pritchard & Gatliff, 1900: 141; Macpherson & Chapple, 1951: 124; Cotton, 1959: 376.

Ianthina pallida Harvey. – Forbes & Hanley, 1853: 553, pl. 69, figs 10–11; H. Adams & A. Adams, 1854: 87; Reeve, 1858: pl. 4, figs 20a–b; Benson, 1860: 412; G. B. Sowerby II, 1882: 51, pl. 444, figs 19–20.

Janthina (Amethistina) pallida Harway [sic]. – Mörch, 1860: 281.

Janthina (Amethistina) striolata Adams & Reeve. – Mörch, 1860: 282.

Amethistina pallida (Harvey) . – Monterosato, 1884: 105.

Janthina pallida (Harvey Mss) Thompson. –Bucquoy et al., 1886: 435, text-fig. 7.

Ianthina globosa var. pallida Harvey. – Tryon, 1887: 37, pl. 10, figs 15–16.

Janthina (Amethistina) pallida Harvey. – Thiele, 1929, p. 225; Priolo, 1959: 186.

Ianthina pallida Thompson. – Laursen, 1953: 31, figs 36–39; Macpherson & Gabriel, 1962: 119.

Ianthina globosa Swainson. – Morton, 1954: 167 (in part J. pallida , misidentified as J. globosa ).

Janthina pallida (Harvey) Thompson. – Pasteur-Humbert, 1962: 53, fig. 75.

Janthina pallida Thompson. – Bennett, 1966: 47, pl. 10, figs 2–3; Fretter & Graham, 1982: 393, fig. 280; Kilburn & Rippey, 1982: 79; Wells & Bryce, 1986: 60, fig. 154; Giannuzzi-Savelli et al., 1999: 54–57, figs 96a–101; Redfern, 2001: 76, pl. 36, fig. 317; Ardovini & Cossignani, 2004: 28, 136; Robertson, 2007a: 5, fig. 4; Luque, 2011: 209, text-fig.; Hernández et al., 2011: 98, figs 30J–K.

Violetta pallida (Thompson) . – Kuroda et al., 1971: 246, pl. 62, fig. 15.

Janthina (Violetta) pallida Thompson. – Abbott, 1974: 113, col. pl. 3, fig. 1180; Higo et al., 1999: 174.

Janthina (Violeta) [sic] pallida Thompson. – Rios 1994: 102, pl. 33, fig. 415.

Janthina (Amethistina) pallida Thompson. – Okutani, 2000: 319, pl. 158, fig. 3.

Janthina pallida Harvey in Thompson.– Poppe, 2008: 722, pl. 306, fig. 3.

Janthina exigua Lamarck. – Severns 2011: 198, lower fig (misidentification).

Type material. Janthina pallida , no type material in NHMUK, location of any type material not known; from Milton Malbay, County Clare, Ireland. Thorpe (1844: 152) also stated the locality as “ Clare ”. Janthina striolata , three syntypes NHMUK 1951.3.14.4–6, from “Pacific Ocean”, ex Cuming collection. It would be preferable to use a specimen that has been included in a molecular study as the neotype for J. pallida , as for all other species, but this species has not been studied by this means. A. Adams & Reeve’s (1850: 54, pl. 11, fig. 9) and Reeve’s (1858: pl. 4, figs 20a–b) illustrated syntype of J. striolata, NHMUK 1951.3.14.4, is here designated the neotype of Janthina pallida Thompson, 1840 . The three syntypes of Janthina striolata are unusual specimens with weak, irregularly spaced, insignificant spiral threads around the last whorl, but are otherwise typical of J. pallida . Because of the cosmopolitan distribution of this as well as all other Janthina species and the very wide locality stated for J. striolata , the type locality of these names is not considered to be an important consideration for a neotype designation, and the designation of this neotype is necessary for the stabilization of the name Janthina pallida .

Other material examined. Present-day samples from Australia and New Zealand: Australia: Northern Territory: Cape Wessel ( WAM); E side Cape Wessel I., Arnhem Land ( AMS C77883); Port Darwin ( AMS C13905). Western Australia: Cable Beach, Broome ( NMV); City Beach, Perth ( AMS); False Bay ( AMS); King George Sound (many, SAMA); Cheyne Beach ( WAM); Peaceful Bay,Bow Bridge ( WAM); Bunbury ( AMS);Windy Harbour, Cape D’Entrecasteaux ( GNS WM15256, 1). South Australia: Port Lincoln ( WAM); Victoria: Portland ( SAMA; NMV); Mordialloc ( NMV). Queensland: Torres Strait ( AMS).

Distribution. The writer is not aware of fossils of Janthina pallida . Laursen (1953: 33) recorded Janthina pallida from “the three oceans, but north of the equator … where the temperature does not drop below 15°C”. This peculiar distribution, in which inter-ocean connections would not be possible, is proved incorrect by Benson’s (1860) much earlier records of J. pallida collected from the Malcolm near Tristan da Cunha in the South Atlantic (30°S 18°W – 33°S 10°W) and NE of St Paul and Amsterdam Islands, as well as midway between Natal and Western Australia (33°S 81°E – 30°S 83°E) in the southern Indian Ocean. Bennett (1966: 47, pl. 10, figs 2–3) illustrated specimens collected alive in the North Pacific (31°06'N 130°06'W; and “in North Pacific waters”) during a cruise c. 500 km west of California, 31°N 125– 140°W.Australian beach records of J. pallida also disprove Laursen’s statement. Although J. pallida has never been recorded from much of the coastline of Australia by Hedley, Iredale or other major Australian authors, museum collections show that it occurs sporadically around the southern, western and northern coasts (clockwise, from western Victoria to Torres Strait). It is relatively common in southern Western Australia, and specimens have been seen from South Africa ( Table 9 )—a pattern suggesting transport from the Atlantic via South Africa in the Antarctic Circumpolar Current. Kilburn & Rippey (1982: 79) also recorded specimens from South Africa. However, the writer is not aware of records from New Zealand, eastern Australia, or Norfolk Island, Lord Howe Island and the Kermadec Islands. It is one of the more northward-ranging species in the Atlantic, occurring in southern Britain, and seems to have a somewhat sporadic occurrence throughout the world tropical and warm-temperate ocean. Savilov (1969: 402) also noted that the Vityaz observed J. pallida only in the North Pacific. Samples were obtained at only 12 stations in the northern subtropical circulation, mainly in areas contiguous with the Kuroshio Current. However, it is evidently common in the Mediterranean ( Figs 4A , 5B ); 280 specimens were reported by Palazzi (1979) cast ashore on beaches in Sicily.

Dimensions. See Table 9 .

Diagnosis. Moderate-sized (H to c. 30 mm), spire moderately tall, whorls strongly and evenly convex, suture deeply impressed; surface lightly polished, without obvious sculpture other than fine spiral threads on a few specimens. Sinus occupying entire height of outer lip, most shallowly V-shaped of all living Janthina species; apex in centre of lip. Anterior end of aperture evenly semicircular; many specimens with widely flared outer lip; central columella curved forwards (abaperturally). Almost uniform very pale violet, slightly paler dorsally; palest of all Janthina species. Lays ovate-triangular egg capsules on underside of float.

Remarks. Thompson (1840: 96, pl. 2, fig. 2) published the name Janthina pallida in the synonymy of “ J. nitens ?”, and stated that the name J. pallida had been suggested verbally by his friend Harvey, who collected the specimens. Thompson (1840: 96) stated that it was most similar to Ianthina nitens Menke , as described and illustrated by Philippi in “Enumeration molluscorum Siciliae” (i.e., Janthina globosa ), but differs in the columella being curved, instead of being straight, so that the anterior end of the aperture is rounded, and “ … the colour … is very different”. Thompson’s (1840: pl. 2, fig. 2) drawing is an excellent one of J. pallida of all later authors, emphasising the evenly subcircular aperture. Many authors before 1961, beginning with Thorpe (1844: 152), have treated J. pallida as the valid name for this species. Therefore, the name J. pallida is conserved under ICZN Article 11.6.1. Following Article 11.6.1 the name should be attributed to Thompson (1840: 96), “its first publication as a synonym”. The name has been attributed correctly by many later authors. Many others have attributed it to Harvey, but the name definitely was made available by Thompson (1840) according to Article 11.6.1. The name J. pallida was attributed to Harvey in 13 references listed by Priolo (1959: 186–187); only two of those Priolo cited attributed it to Thompson. Thorpe (1844: 152) provided a slightly muddled attribution of the name to “Thompson’s Annals of Nat. Hist. 5. p. 96. t. 2. f. 2.”, and was followed by Dall (1908: 318). Dall (1908) provided a publication date of 1817, even though Forbes & Hanley (1853: 553) provided the correct reference, despite attributing the name to Harvey. The name Janthina pallida was not published in 1817 (Sherborn, 1922–1933) and the page and figure numbers cited by both Thorpe and Dall are the same as for Thompson (1840), so their references were in error. Several other authors have published muddled references to this name, not having seen Thompson’s (1840) paper.

Janthina pallida consistently is smaller than the largest specimens of J. globosa , but is otherwise very similar in most characters. The illustration by Ardovini & Cossignani (2004: 136) shows an unusually tall, narrow specimen. The obvious difference from J. globosa is that it lacks the small, angular, anterior extension of the columellar margin of the aperture of J. globosa , and instead the anterior end of the aperture is evenly and regularly curved in J. pallida . The outer lip sinus also is very shallow, considerably shallower than in all other living Janthina species. A unique character is that the central area of the columella is quite strongly convex, curving towards the anterior (abaperturally). Many specimens also have the outer lip quite broadly flared, or reflexed, a further unique character. Most specimens are also a much paler violet colour than all other Janthina species, fading almost to white on the sutural ramp of some specimens. Some specimens also have a weak spiral ridge or groove formed as the trace of the apex of the sinus in the outer lip, showing as a low spiral ridge on spire whorls of about 20% of specimens (as in Laursen, 1953: fig. 36), but this is an individual character. The radular teeth ( Laursen, 1953: fig. 39) are much the shortest and most strongly hooked of all Janthina species. Janthina pallida also has a narrower distribution than most other Janthina species, and is one of the least common species throughout most of its range, particularly in the Southwest Pacific, although it is common in the Mediterranean and in southern Western Australia. Palazzi (1979) recorded 280 specimens collected on the beaches of Terrasini, Sicily. Priolo (1959: 186–187) also listed 21 references in the literature on Mediterranean molluscs mentioning J. pallida , including under other species names. Dimitris Poursanidis sent the writer photographs of living specimens collected at Arina Beach, Heraklion, Crete , revealing that the eggs are bright pink ( Figs 4A , 5B ), much deeper in colour than the other consistently pale pink Janthina eggs observed. These photographs also reveal that this is the one species of Janthina that does not seem to rest its head or snout in the (correspondingly very shallow) sinus in the outer lip. The specimens photographed by Dimitris Poursanidis did not expand out of their shells sufficiently to confirm their external anatomical characters fully, but do not appear to be distinguishable from other Janthina species anatomically.

Time range. No fossil record; living only.

Figures

Figure 2 (facing page 123). Shells of the five living species of Janthina and two species of Recluzia recognized in this work; apertural views, and left lateral views showing outer lip sinus.(A–F) Janthina janthina (Linnaeus);A–B, D, GNS RM4442, two specimens, beach, Takou Bay, Northland, New Zealand; C, GNS WM15986, “bicolor” form, San Lourenço Beach, Santa Maria I., Azores, Atlantic; E, GNS RM6735, “bicolor” form, Ohope Beach, Whakatane, New Zealand; F, GNS WM15297, beach between Hutchinson Bluff and Rayner Point, Raoul I., Kermadec Islands. (G–J) Janthina globosa (Swainson); G, GNS WM15254, beach, Mauritius, Indian Ocean; H–J, GNS RM5321, two specimens, Muriwai Beach, West Auckland, New Zealand. (K–L) Janthina pallida Thompson, GNS WM15256, beach, Windy Harbour, Cape D’Entrecasteaux, southern Western Australia.(M, O) Janthina exigua Lamarck, GNS RM5626, Nukumaru Beach, Whanganui, New Zealand. (N, Q) Janthina umbilicata d’Orbigny, GNS RM5627, Nukumaru Beach, Whanganui, New Zealand. (P, R) Recluzia johnii (Holten), GNS WM17360, ventral and dorsal views; trawled in sediment, 130–180 m, Swain Reefs, SE Queensland, Australia (shortest specimen, last entryin Table 12).(S–T) Recluzia lutea (Bennett), GNS RM6748,beach, Great Exhibition Bay,Northland, New Zealand (from same sample as Figs 36M–P). Scale bar 10 mm, applies to all figures.

Figure 4 (facing page 129). Living animals in aquaria. (A) Janthina janthina (Linnaeus) (centre) and J. pallida Thomson (left, and part of another float at right) together, showing different bubble sizes in floats, and J. janthina feeding on pink eggs of J. pallida beneath float; collected at Arina Beach, Heraklion, Crete. (B) Janthina janthina, collected on beach in northern New South Wales, Australia, clearly showing forked cephalic tentacles;(C–E) Janthina janthina, all data as for Fig.4A; C, showing forked cephalic tentacles, lack of eyes, and teeth and odontophore protruding from mouth at end of extended snout; D–E, showing extended head and snout, odontophore visible in mouth, and partially expanded right epipodium lying over shell (A, C–E, reproduced with permission of Dimitris Poursanidis, Heraklion, Crete; B, reproduced with permission of Denis Riek, Brunswick Heads, New South Wales). Scale bars 10 mm.

Figure 5. (See facing page 131 for caption).