Beu: Evolution of Janthina and Reduzia 
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propodium, the mesopodium to which the float is attached, 
and the colourless, translucent epipodium of the right 
side. Another epipodium on the left is not visible in this 
view, although its posterior edge is shown in Fig. 1A and 
a contracted left epipodium of J. janthina is visible in Fig. 
5A. The drawings by Okutani (1956: text-figs 9-10) are the 
only ones the writer is aware of that reveal a pair of almost 
identical epipodia, right and left, linked across the centre 
so they comprise one deeply embayed structure, with finely 
digitate margins. The right epipodium (Fig. 1A, centre) is 
subcircular with finely digitate edges when fully expanded, 
and when resting on the shell extends down to cover the top of 
the last shell whorl and part of the surface of the penultimate 
whorl below the aperture. Its relationship to the rest of the 
foot is shown well in Figs 4D-E. Another good photograph by 
Wells & Bryce (1986: 61) shows the epipodium less clearly. 
Another was used as the cover illustration for Journal of 
Molluscan Studies vol. 77, but shows the base of the shell 
rather than a spire view, so epipodia are not visible. Another 
view published by Batson (2003: 107) shows a specimen of 
J. janthina with its propodium extended, evidently in the 
process of adding a bubble to its float, but the epipodia are 
out of focus. Anderson (2007: 48) also published a good 
photograph of a living specimen of J. janthina , showing the 
float excellently, including its degenerating outer end and 
Lepas barnacles attached to the shell, but again epipodia 
are not visible. Anderson (2007: 48) described the float 
as “quite firm, reminding me of ... plastic bubble wrap”. 
Another excellent photograph of J. janthina by Dimitris 
Poursanidis included in a “creatura-blog” by Crew (2014) 
clearly shows the expanded snout with slightly protruding 
odontophore, the black-speckled, subdivided cephalic 
tentacles, the separate propodium between the float and the 
tentacles, and a contracted left epipodium (Fig. 5A). The 
function of the epipodia seems not to have been determined, 
although Thiele (1892: 580, pi. 23, fig. 2) described and 
compared Janthina epipodia. Wilson & Wilson (1956: 301) 
suggested that the right epipodium helps control the passage 
of water through the mantle cavity. Wilson & Wilson (1956: 
301) also noted that “when the animal is alive the shell is 
very slippery”, so one possible function of the epipodia is 
to secrete mucus over the external surface of the shell. This 
would help it to avoid both predators and epifauna. A problem 
with this interpretation, though, is that in photographs of 
living specimens (Figs 5D-E) the epipodia scarcely touch the 
shell. Certainly, the epipodia are held virtually motionless. 
No observers during the last century have confirmed the 
suggestions of early writers that the epipodia aid movement 
of the animal with swimming motions, in the same manner as 
pteropod “wings”. Morch (1860: 263) discussed the various 
opinions published up until that time on the function of the 
epipodia (he did not provide references to most of these 
opinions, but most are fairly obvious among the references 
in the present report). He stated that Blainville and Rang 
considered them to be “appareil natatoire”, i.e., swimming 
apparatus, and Quoy & Gaimard (1832: 244) stated that they 
helped a little with locomotion carried out largely by the 
foot. Johnston also regarded the epipodia as governing the 
animal’s movements, but d’Orbigny (1841) rejected these 
assertions. Grant also stated (correctly, as is now known) 
that the epipodia do not move at all, although slight motion 
to rest against the shell or lie free above it must be possible 
if the epipodia secrete mucus over the shell exterior. 
No epipodia are visible in any illustrations of living 
specimens of Reduzia species, in the excellent photograph 
published by Bennett (1966: pi. 11, fig. 1), in those by 
Churchill et al. (2011a: fig. IB; 2011b: figs IB, G), or in 
Figs 6-7. Epipodia apparently are not present in Recluzia 
species. If their functions in Janthina include the secretion 
of mucus over the shell surface, the persistent pale brown 
conchiolin periostracum of Reduzia possibly serves the 
same protective function. A periostracum is not obvious in 
any Janthina specimens the writer has observed and it is 
apparently very ephemeral in Janthina species. 
Ianthinin purple dye. Robertson (2007a: 9) stated that the 
purple dye of Janthina is very different from the “Tyrian 
purple” of muricoidean neogastropods, as muricoidean 
purple dye is secreted by a different gland, has a different 
composition, is in solution, and is an anaesthetic used to 
help capture prey. In contrast, Janthina purple dye is finely 
particulate, and Robertson thought it was used in defence. 
However, Ganapati & Subba Rao (1959) described a 
specimen of Porpita collected with a specimen of Janthina 
(J. pallidal ) attached to its underside. Secretion of purple 
dye by the Janthina specimen caused the Porpita animal 
to remain motionless and distended while Janthina preyed 
upon it. This seems to indicate that the dye has an anaesthetic 
effect in Janthina, besides its camouflaging and antagonistic 
effects. Wilson & Wilson (1953: 301-302) also reported 
observations made by R M. David on RV Discovery II on 
Janthina specimens collected at sea: “Several... Velella were 
taken with small Ianthina attached to the under surface ... 
apparently browsing on the Velella ; the latter seemed to be 
lifeless ... It was observed that the Ianthina exuded their 
purple dye periodically (fairly frequently) while feeding, and 
it seems possible the dye may be used to anaesthetize the 
Velella ”. Similar accounts of feeding apparently involving 
anaesthesia were provided by Hardy (1956) and Rolan 
& Trigo (2003). Janthina pallida , in particular, has been 
reported by several authors to relinquish its float and creep 
on specimens of Velella or Porpita while browsing on the 
chondrophore, forming another float when only the Velella 
skeleton remains (Ganapati & Subba Rao, 1959; Bayer, 1963: 
458) [Bayer (1963: 458) pointed out that the account by 
Ganapati & Subba Rao (1959) actually described a capsule¬ 
laying species, not J. janthina as they thought], Bennett 
(1966: 47, pi. 10, fig. 3) noted of specimens observed in 
the North Pacific: “by the time the ship reached 127°31'W, 
it was found that almost all [Velella] animals caught had 
from one to five small Janthina pallida Thompson, feeding 
on the undersuface among the tentacles”. Most specimens 
of J. pallida collected near the Kuroshio Current by the 
Vityaz also were attached to Velella floats, on which they 
had been feeding (Savilov, 1969). Most notably, Palazzi 
(1979) recorded 280 specimens of J. pallida , ranging from 
small juveniles to 21 mm high, collected on the beaches of 
Terrasini, Sicily, on 7-8 Mar 1979, of which 253 (90.4%) 
were still attached to and feeding on specimens of Velella 
when collected. Giannuzzi-Savelli et al. (1999: 56, 57, fig. 
101) also published photographs of specimens of J. pallida 
feeding on the underside of specimens of Velella , again aided 
by the anaesthetic effects of ianthinin purple dye. 
Allan (1934) gave a popular account of “Tyrian purple” 
and its sources, recording several muricids, “sea hares” 
( Tethys ), Janthina and benthic Epitoniidae as secreting 
