Janthina janthina janthina (Linnaeus 1758
Evolution of Janthina and Recluzia (Mollusca: Gastropoda: Epitoniidae)
(Janthina, 1758) janthina (Linnaeus, 1758)
Figure 1. Living specimens of Janthina janthina (Linnaeus) in life position in an aquarium, suspended beneath their floats, redrawn from photographs in Wilson & Wilson (1956: pl. 1, figs 1–2) and Yonge & Thomson (1976: pl. 5, lower); bubbles in float shown schematically. (A) left (anatomically right) lateral view, showing float, attached to mesopodium and located against propodium (at left end of float); partially extended snout; black-tipped right cephalic tentacle, not fully visible here; smooth, almost circular right epipodium (centre); digitateposterior edge of left epipodium, at rear between shelland mesopodium; and rear end of float disintegrating.(B) dorsal(anatomically ventral) view of another specimen forming a new float bubble, showing odontophore and radula partly everted out of mouth at tip of snout; black-tipped, forked cephalic tentacles; cupped propodium with black lining, in process of enclosing an air bubble; shell (right edge); and epipodium (left edge; anatomically on right). Scale bar 10 mm.
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).
Figure 33. Janthina janthina (Linnaeus), range of variation in shell shape; copy at published size of Laursen (1953: fig. 15); numbers on figure as published by Laursen.Fig. 33.3, lectotype designated here of Helix janthina Linnaeus, 1758; Figs 33.7, 33.12, paralectotypes of Helix janthina; all three in collection of Linnean Society of London. Original scale bar included = 20 mm (i.e., figures reduced slightly).
Figure 32. Specimens of Janthina janthina (Linnaeus). (A–D) GNS RM5844, Waikanae Beach, west Wellington, New Zealand; SEM, 2 specimens; apical views showing steeply inclined protoconch, slightly irregular teleoconch coiling, weak irregular spiral sculpture, and prominent axial riblets on early teleoconch whorls; B, protoconch of A enlarged; D, apex of protoconch of C enlarged. (E–F) NHMUK1854.12.4.399a,lectotype designated here ofJanthina orbignyi Mörch,“Atlantic Ocean”; largest of seven syntypes in d’Orbigny’s South American collection, illustrated by d’Orbigny (1841: 413, pl. 61, figs. 8–10); NHMUK photos sent by A. Salvador. Scale bars:A, C, 4 mm; B, 500 µm; D, 300 µm; E–F, 10 mm.