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First occurrence of putative hybridization in the genus
Lobatus (Caenogastropoda: Strombidae)
Gijs C. Kronenberg
Mollusca Collection
Naturalis Biodiversity Center
P.O. Box 9517
NL-2300 RA Leiden
The Netherlands
ABSTRACT
A putative hybrid Lobatus gigas L. gallus is reported. It is
compared with its putative parental species.
Additional Keyword: Caribbean
INTRODUCTION
Kronenberg (2008: 332, table) presented a review of
known putative hybrids within the gastropod family
Strombidae. A total of sixteen different combinations of
putative parental species, all of Indo-Pacific origin, were
indicated. Some of these were known from only one spec-
imen, but others from over 100 specimens. Presumed
cases of hybridization of Strombidae within the Caribbean
are anecdotal, see for instance Conch-L archives (www
.listserv.uga.edu), and restricted to Strombus pugilis
Linnaeus, 1758 S. alatus Gmelin, 1791. Images of
such putative hybrids are published on the website of
Bill Frank (www.jaxshells.org/strombss1ax.htm).
Reed (1995a, b) observed frequent interspecific mating
between co-occurring species of Caribbean Strombidae
with a remarkably little discrimination in choice of part-
ner, i.e., males have frequently been observed attempting
to mate with non-conspecific females. However, only
matings of S. pugilis S. alatus produced fertile eggs.
In May 2012 I received an e-mail from Harry G. Lee,
from Jacksonville, Florida, who drew my attention to a
putative hybrid Lobatus gallus (Linnaeus, 1758) L. gigas
(Linnaeus, 1758) in the private collection of Pete Stimpson,
in Loudon, Tennessee. Subsequently, Dr. Stimpson made
the specimen available for examination. The results are
presented herein.
SYSTEMATICS
Family Strombidae Rafinesque, 1815
Genus Lobatus Swainson, 1837
Type Species: Strombus bituberculatus Lamarck,
1822 (¼ Strombus raninus Gmelin, 1791) by monotypy.
Pliocene to Recent, Caribbean.
Discussion: The genus name Lobatus first appeared
in 1837 in an anonymously compiled catalogue. Iredale
(1921: 208) concluded that authorship of that catalogue
should be attributed to Swainson. Therefore all newly
introduced names in this catalogue should be attributed
to Swainson. In his broad concept of the large, broad-
winged Strombidae, Abbott (1960) synonymized Lobatus
with Tricornis Jousseaume, 1886 (Type species: Tricornis
tricornis (¼ Strombus tricornis [Lightfoot], 1786) by
monotypy). Jung and Heitz (2001) argued that the intro-
duction of Lobatus should be considered as a historical
accident and considered the name unavailable.
The name Lobatus was further discussed by Kronenberg
and Lee (2007) and Landau et al. (2008), who concluded
that Lobatus was the first available name for the group
of large, broad winged Strombidae from the Caribbean
and Panamic Fauna province, rejecting the conclusions
reached by Jung and Heitz (2001). Based on molecular
(Latiolais et al., 2006) and morphological (Kronenberg,
2008) data it was concluded that Lobatus could not be
considered a junior synonym of Tricornis.
Lobatus gallus (Linnaeus, 1758) Lobatus gigas
(Linnaeus, 1758)
(Figures 1–5)
Description: Shell large, length from apex to tip of
anterior canal 131 mm, consisting of about 9 teleoconch
whorls and broad flaring outer lip (wing) with tip
reaching beyond apex. Protoconch broken off and first
teleoconch whorls badly eroded; of preserved teleoconch
whorls second with axial costae, irregularly interrupted
by broader costae, about three per whorl, here inter-
preted as varices. Costae gradually changing into
pointed knobs on shoulder with abapical part of base
adjacent to suture. Some knobs distinctly broader as a
THE NAUTILUS 127(1):36–39, 2013 Page 36
continuation of pattern of varices, last varical knob on
antepenultimate whorl. Knobs gradually increasing in
number and size, penultimate whorl with eleven knobs.
On last whor l, knobs increasing in size at faster r ate,
penultimate knob largest, slightly past mid dorsum, last
knob much smaller. Spiral sculpture much less promi-
nent, on first teleoconch whorls eroded, on other spire
whorls about seven discernible. Last whorl with promi-
nent spiral cords abapically to shoulder knobs. Outer lip
widely dilated, with adapical broadly rounded point, rim
of lip slightly sinuous sloping down to point of attach-
ment with ventral side of last whorl. Lateral part of outer
lip slightly undulating on abapical half, corresponding
with spiral cords on dorsal side, stromboid notch well
developed. Adapertural side of outer lip smooth, colu-
mella smooth, apart from two narrow, l ow folds running
into aperture. Anterior canal slightly developed. Callus
on ventral side extended, thin, translucent, with gray-
metallic ha ze on central part. Color of shell cream with
irregular mottling of brown, rim of adapertural side of
outer lip cream, aperture light pink; base of columella
cream, adapical part light pink. Operculum stromboid,
smooth edged, 40 mm in length. Soft parts unknown.
Material Examined: One specimen from Puerto
Rico, west coast, off Mayagu¨ ez at about 4.6 m, Septem-
ber 1972, Pete Stimpson collection, unnumbered.
Distribution: So far only one specimen known, for
data see above.
Figures 1–5. Putative hybrid Lobatus gallus L. gigas. Puerto Rico, off Mayagu¨ ez at about 4.6 m, September 1972, Pete Stimpson
collection, unnumbered, height from apex to tip af anterior canal: 131 mm. 1. Apertural view. 2. Dorsal view. 3. Lateral view, note
relatively large shoulder knob. 4. Apical view, same scale as Figures 1–3. 5. Operculum, 40 mm length.
G.C. Kronenberg, 2013 Page 37
Remarks: In general the specimen is closest to L. gallus,
both in general shape as well as size. Although usually
smaller, the largest L. gallus measured attained a size of
134 mm from apex to tip of anterior canal. The hybrid
specimen differs from L. gallus by its shorter anterior
canal;therelativelargersizeofthepenultimateshoul-
der knob on the last whorl; the shape of the p osterior
lobe of the outer lip, which is much more narrow in
L. gallus; and the color of the aperture. In L. gallus the
rimoftheadaperturalsideoftheouterlipandthe
columella are cream to pinkish light orange c olored,
but deep within the aperture it is always white. In the
specimen here discussed, the rim of the outer lip is
white, but deep within the aperture as well as the colu-
mella, it is pink, a color never seen in L. gallus.
Lobatus gigas grows to a much larger size, although
dwarfs of about 150 mm are known. The hybrid speci-
men differs from L. gigas by its smaller size; slightly
longer an teri or canal, the shape of the posterior lobe
of the outer lip; and the much larger knobs on the
penultimate whorl.
DISCUSSION
The occurrence of the traits in the specimen reported
herein could also be explained by developmental muta-
tions within a specimen of one the putative parental
species. However, in such a case one might expect that
not so many shifts in shell characters reported herein as
compared to one of the supposed parental species would
occur, or one might expect one or more unique traits, i.e.
shell characters that cannot be attributed to a character
of one of the parental species or being intermediate
between the supposed parental species. As this is not
the case, and the specimen exhibits characters that are
more or less intermediate between L. gallus and L. gigas,
sometimes closer to either of these supposed parental
species, I conclude that at present we are dealing with a
putative hybrid L. gallus L. gigas.
Several cases of putative hybridization within the
Strombidae were summarized by Kronenberg (2008).
All of these have been solely based on shell morphology
and this case is no exception. The remarks by Kronenberg
(1993), i.e., that the anatomy of the presumed hybrid was
never examined nor that mating between supposed paren-
tal species was ever observed, are in fact still valid for
all cases of presumed hybridization within Strombidae.
Exceptional are observations made by Reed (1995a, b),
who observed reproductive behavior of several species
currently assigned to Lobatus,viz.L. gigas; L. gallus;
L. costatus (Gmelin, 1791) and L. raninus (Gmelin, 1791).
She observed mating between several species of Lobatus
both in the field and in the laboratory. Apart from the
observation that males occasionally attempted copulation
with a male that already was engaged in copulation with
a female, mating with non conspecific females was also
observed. Reed (1995a) reported the following combi-
nations: L. gallus ♂ L. costatus ♀ ; L. raninus ♂
L. costatus ♀; L. raninus ♂ L. gallus ♀;andL. gallus ♂
L. raninus ♀. Reed (1995b) also observed one case of
multiple partners, i.e. copulation of L. costatus ♀
with
L. gallus ♂ and L. raninus ♂. None of the females
spawned after these copulations. Although L. gigas was
present during these experiments, no mating between
L. gigas and L. gallus or any other species of Lobatus,
was reported.
It should be noted that “In a separate collection of
Strombus pugilis and S. alatus individuals mated at
random with no apparent distinction between species,
and females spawned fertile egg masses, regardless of
the male involved.” (Reed, 1995a: 329). However, we
don’t know anything about further results, i.e., whether
the eggs hatched or not. Within the genus Lobatus,
L. gallus and L. gigas appear to be the most closely
related species ac cording to the cladogram p resented
by Latiolais et al. (2006). These authors did not incor-
porate L. goliath (Schro
¨
ter, 1805) in their analysis. In
an analysis based on anatomy (Simone, 2005), L. gigas
and L. goliath groupassistertaxa,whichinturnare
sister taxa to L. cost atus and L. gallus.
Recently, Oxenford (2011) described a small popula-
tion of L. goliath off Barbados, reported from two local-
ities on the western coast of that island. In Barbadian
waters, several species ofStrombidaewerealready
reported, among them L. gigas (Oxenford, 2011). Oxenford
already noted that, although it is quite unlikely that
L. golia th would have a serious negative impact on the
marine ecosystem, it would be desirable to monitor
this / these population(s) to record any developments.
Taking into consideration the relatively large number of
putative cases of hybridization in Strombidae (Kronenberg,
2008), the close relationship between L. goliath and
L. gigas (Simone, 2005), and the behavior of Strombidae
as reported by Reed (1995a, b), we cannot exclude the
possibility that hybridization will occur. Of course,
these species should also occur syntopic, i.e. not only
living in the same geographical range but also sharing
thesamehabitat.
ACKNOWLEDGMENTS
I thank Dr. Harry G. Lee, Jacksonville, Florida, for drawing
my attention to the specimen discussed herein; Dr. Pete
Stimpson, Loudon, Tennessee for sending the specimen on
loan; andDr. GregoryHerbert, Universityof SouthFlorida,
for additional comments on possible results of hybridiza-
tion. Dr. Lee also reviewed a first draft of the manuscript
and provided useful comments. Two anonymous reviewers
provided useful comments that further helped to improve
this paper. Mr. Eelco Kruidenier, Naturalis Biodiversity
Center made the photographs. I thank my partner, Ms.
Marianne Matthijssen for her abiding support.
LITERATURE CITED
Abbott, R.T. 1960. The genus Strombus in the Indo-Pacific.
Indo-Pacific Mollusca 1(2): 33–146.
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