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Mapping alien Mollusca distribution in the Mediterranean Sea: The Lessepsian immigrant Retusa desgenettii (Audouin, 1826) reaches Turkey

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The opening of the Suez Canal in 1869 has led to the colonisation of the Mediterranean Sea by a large number of tropical/subtropical species, including several sea slugs and shelled relatives. Among them, the Red Sea taxon Retusa desgenettii (Audouin, 1826) is a well known Lessepsian invader, being first recorded from the Suez Canal and subsequently from the Mediterranean waters of Egypt and Israel. We hereby review R. desgenettii Mediterranean literature and offer an updated map of its Mediterranean spreading. On the basis of the analysis of a bioclastic sediment from Bozburun, we also considerably extend the known invaded Mediterranean range, first reporting its presence from Turkey, presumably reached via natural dispersal. R. desgenettii shell is redescribed and compared with the most similar native Retusa sensu stricto and alien Cephalaspidea recorded from the Mediterranean Sea, as to facilitate possible future records in the wide area between previous records and present ones. Within this framework, Retusa candidula (Locard, 1892), Retusa pellucida (T. Brown, 1827) and Retusa obtusa (Montagu, 1803) are also excluded from the Mediterranean fauna.
AeG. Lessepsian Cephalaspidea. HeP. Native northeastern AtlanticMediterranean Retusa sensu stricto listed as living in the Mediterranean Sea by recent authors. AeB, E. Retusa desgenettii (Audouin, 1826). A. Abu Ramada (Hurghada, Egypt, Red Sea) e sediment 13 m. B, E. Bozburun (Turkey, Mediterranean Sea) e beached bioclastic sediment. C, F. Pyrunculus fourierii (Audouin, 1826). Data as B. D, G. Acteocina mucronata (Philippi, 1849). Data as B. H. Retusa multiquadrata Oberling, 1970 sensu Buzzurro and Greppi (1997) (after Segers et al., 2009). Madeira. I. Retusa candidula (Locard, 1892) e syntype (MNHN-IM-2000-28257). Ile de R e (France). JeK. Retusa mammillata (Philippi, 1836) (after Oliverio and Tringali, 2001). Kas¸(Kas¸(Turkey) e bioclastic sediment 34 m. LeN. Retusa minutissima (Monterosato, 1878) (after Oliverio and Tringali, 2001). L. Paleohora (Crete Island) e bioclastic sediment 10 m. MeN. Valencia (Spain) e unrecorded depth e MTRS (ZMR). O. Retusa obtusa (Montagu, 1803) (after Oliverio and Tringali, 2001). Le Verdon-sur-Mer (Aquitanie, western France) e unrecorded depth e FS coll (ZMR). PeQ. Retusa truncatula (Brugui ere, 1792) (after Oliverio and Tringali, 2001). P. Kas¸(Kas¸(Turkey) e bioclastic sediment 34 m. Q. Djerba Island (Tunisia) e unrecorded depth. R. Retusa leptoeneilema (Brusina, 1866) (after Oliverio and Tringali, 2001). Umag (Croatia) e beached bioclastic sediment. S. Retusa pellucida (T. Brown, 1827). Ura-Guba (Russia). Scale bars: D, I, OeS: 1.0 mm; AeC, H,
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Mapping alien Mollusca distribution in the Mediterranean Sea:
the Lessepsian immigrant Retusa desgenettii (Audouin, 1826)
reaches Turkey
Fabio Crocetta
a
,
*
, Lionello Paolo Tringali
b
a
Stazione Zoologica Anton Dohrn, Villa Comunale, I-80121 Naples, Italy
b
Via Elio Lampridio Cerva 100, I-00143 Roma, Italy
article info
Article history:
Available online xxx
Keywords:
Mollusca
Cephalaspidea
Retusa desgenettii
Mediterranean Sea
Turkey
Alien species
abstract
The opening of the Suez Canal in 1869 has led to the colonisation of the Mediterranean Sea by a large
number of tropical/subtropical species, including several sea slugs and shelled relatives. Among them,
the Red Sea taxon Retusa desgenettii (Audouin, 1826) is a well known Lessepsian invader, being rst
recorded from the Suez Canal and subsequently from the Mediterranean waters of Egypt and Israel. We
hereby review R.desgenettii Mediterranean literature and offer an updated map of its Mediterranean
spreading. On the basis of the analysis of a bioclastic sediment from Bozburun, we also considerably
extend the known invaded Mediterranean range, rst reporting its presence from Turkey, presumably
reached via natural dispersal. R.desgenettii shell is redescribed and compared with the most similar
native Retusa sensu stricto and alien Cephalaspidea recorded from the Mediterranean Sea, as to facilitate
possible future records in the wide area between previous records and present ones. Within this
framework, Retusa candidula (Locard, 1892), Retusa pellucida (T. Brown, 1827) and Retusa obtusa (Mon-
tagu, 1803) are also excluded from the Mediterranean fauna.
©2015 Elsevier Ltd and INQUA. All rights reserved.
1. Introduction
The Mediterranean molluscan fauna is considered as the best
known in the world (Oliverio, 2003). However, despite continuous
efforts to provide updated data sets for the entire basin, a general
discrepance occurs between western/northern and eastern/south-
ern parts (Crocetta et al., 2015). The general knowledge of the latter
is still considerably poor when compared with that of the central
and western basins, despite the presence of updated check-lists
based on both bibliographic and unpublished data (Barash and
Danin, 1992;
Oztürk et al., 2004, 2014; Crocetta et al., 2013a,
2013b; 2014). So far, ~2000 molluscan species are known from
the Mediterranean Sea, of which ~200 are aliens (Zenetos et al.,
2012; Sabelli and Taviani, 2014). Thirty of them are sea slugs, the
majority of which has an Indo-Pacic origin (recent reviews in
Yokes¸ et al., 2012; Bogi and Galil, 2013; Crocetta et al., 2013b).
Among them, Retusa desgenettii (Audouin, 1826) is a well known
Lessepsian invader, occurring in the Red Sea (Yonow, 2008) and
being rst recorded from the Suez Canal (Moazzo, 1939) and sub-
sequently from the Mediterranean waters of Egypt and Israel (Bogi
and Galil, 2002, 2006, 2007; Mienis, 2004; Mienis and Zaslow,
2004; Scaperrotta et al., 2009; Cossignani and Ardovini, 2011;
Perna, 2013). Starting from the analysis of R.desgenettii collected
in a bioclastic sediment from Bozburun (Turkey, Mediterranean),
we hereby redescribe its shell and compare it with the most similar
alien and native Mediterranean Retusa sensu stricto. In addition, we
review the Mediterranean literature covering the species and offer
an updated map of its Mediterranean spreading, rst reporting the
presence from Turkey and considerably extending the known
Mediterranean invaded range.
2. Materials and methods
2.1. Abbreviations and acronyms
The following abbreviations and acronyms were used: coll e
collection/s; FS eFrancesco Settepassi, Roma (Italy); GA eGaetano
Ambrosiano, Roma (Italy); LPT eLionello Paolo Tringali, Roma
(Italy); m emeter/s; MO eMarco Oliverio, Universit
a di Roma La
Sapienza(Italy); MTRS eMonterosato coll (Museo Civico di
*Corresponding author.
E-mail address: fabio.crocetta@szn.it (F. Crocetta).
Contents lists available at ScienceDirect
Quaternary International
journal homepage: www.elsevier.com/locate/quaint
http://dx.doi.org/10.1016/j.quaint.2015.03.009
1040-6182/©2015 Elsevier Ltd and INQUA. All rights reserved.
Quaternary International xxx (2015) 1e6
Please cite this article in press as: Crocetta, F., Tringali, L.P., Mapping alien Mollusca distribution in the Mediterranean Sea: the Lessepsian
immigrant Retusa desgenettii (Audouin, 1826) reaches Turkey, Quaternary International (2015), http://dx.doi.org/10.1016/j.quaint.2015.03.009
Zoologia, RomaeItaly); NMBE eNaturhistorisches Museum, Bern
(Swisse); RR eRuggero Ruggeri, Roma (Italy); sh eshell/s; spm e
specimen/s; SR eStefano Runi, Universit
a di Roma 2 eTor Ver-
gata(Italy); ZMR eZoological Museum Rome (Museo Civico di
Zoologia, RomaeItaly).
2.2. Unpublished data and laboratory work
Unpublished material was obtained by a sample of bioclastic
sediment collected on the beach of Bozburun (southern Turkey)
and is currently deposited in SR coll. Shells were air dried, mounted
on SEM stubs and goldepalladium coated for SEM examination
with a Philips XL30.
2.3. Taxonomy, Mediterranean literature and updated map
Updated taxonomy and nomenclature hereby used follow World
Register of Marine Species (WoRMS). Published Mediterranean
records of Retusa desgenettii (Audouin, 1826) were searched both in
indexed and grey literature (i.e. non peer-reviewed and/or non
indexed papers), and carefully reviewed. Published and unpub-
lished data were used to build an updated distributional map.
3. Results
3.1. Systematics
Class GASTROPODA Cuvier, 1795
Order CEPHALASPIDEA P. Fischer, 1883
Family RETUSIDAE Thiele, 1925
Genus Retusa T. Brown, 1827
Retusa desgenettii (Audouin, 1826)
(Figures 2AeB, E)
3.2. Material examined
Type material: not examined. Note: a syntype (Savigny coll) is
gured in Bouchet and Danrigal (1982) and Vald
es and H
eros
(1998).Additional material: Bozburun (Turkey, Mediterranean
Sea), 08/2002, beached bioclastic sediment, 3 sh (SR legit), with
Pyrunculus fourierii (Audouin, 1826) (Fig. 2C, F) and Acteocina
mucronata (Philippi, 1849) (Fig. 2D, G); Abu Ramada (Hurghada,
Egypt, Red Sea), 1991, bioclastic sediment, 13 m, 5 sh (GA legit);
Marsa Fijab (Sudan, Red Sea), 28/01/1992, beached bioclastic sedi-
ment, 76 partially preserved spm and sh (MO legit); Green Island
(Massawa, Eritrea, Red Sea),1970, beached bioclastic sediment, 1 sh
(ex RR coll, LPT coll).
3.3. Mediterranean literature and updated map
Retusa desgenettii (Audouin, 1826) is a well-known Lessepsian
invader, being rst recorded from the Suez Canal (Moazzo, 1939)
and then from Egypt, in 1969 (Mienis, 2004) and Israel, in 1997
Fig. 1. The eastern Mediterranean and the known distribution of Retusa desgenettii
(Audouin, 1826) (main localities of presence highlighted). Circles: published records.
Square: present record. Numbers corresponding to bibliographic references and
geographic coordinates reported in Table 1.
Fig. 2. AeG. Lessepsian Cephalaspidea. HeP. Native northeastern Atlantic-
Mediterranean Retusa sensu stricto listed as living in the Mediterranean Sea by
recent authors. AeB, E.Retusa desgenettii (Audouin, 1826). A. Abu Ramada (Hurghada,
Egypt, Red Sea) esediment 13 m. B, E. Bozburun (Turkey, Mediterranean Sea) e
beached bioclastic sediment. C, F.Pyrunculus fourierii (Audouin, 1826). Data as B. D, G.
Acteocina mucronata (Philippi, 1849). Data as B. H.Retusa multiquadrata Oberling, 1970
sensu Buzzurro and Greppi (1997) (after Segers et al., 2009). Madeira. I.Retusa can-
didula (Locard, 1892) esyntype (MNHN-IM-2000-28257). Ile de R
e (France). JeK.
Retusa mammillata (Philippi, 1836) (after Oliverio and Tringali, 2001). Kas¸ (Turkey) e
bioclastic sediment 34 m. LeN.Retusa minutissima (Monterosato, 1878) (after Oliverio
and Tringali, 2001). L. Paleohora (Crete Island) ebioclastic sediment 10 m. MeN.
Valencia (Spain) eunrecorded depth eMTRS (ZMR). O.Retusa obtusa (Montagu, 1803)
(after Oliverio and Tringali, 2001). Le Verdon-sur-Mer (Aquitanie, western France) e
unrecorded depth eFS coll (ZMR). PeQ.Retusa truncatula (Brugui
ere, 1792) (after
Oliverio and Tringali, 2001). P. Kas¸ (Turkey) ebioclastic sediment 34 m. Q. Djerba
Island (Tunisia) eunrecorded depth. R.Retusa leptoeneilema (Brusina, 1866) (after
Oliverio and Tringali, 2001). Umag (Croatia) ebeached bioclastic sediment. S.Retusa
pellucida (T. Brown, 1827). Ura-Guba (Russia). Scale bars:D,I,OeS: 1.0 mm; AeC, H,
JeN: 500
m
m; EeG: 200
m
m.
F. Crocetta, L.P. Tringali / Quaternary International xxx (2015) 1e62
Please cite this article in press as: Crocetta, F., Tringali, L.P., Mapping alien Mollusca distribution in the Mediterranean Sea: the Lessepsian
immigrant Retusa desgenettii (Audouin, 1826) reaches Turkey, Quaternary International (2015), http://dx.doi.org/10.1016/j.quaint.2015.03.009
(Bogi and Galil, 2002), where the species has been subsequently
found in several sampling sites (Bogi and Galil, 2006, 2007;
Scaperrotta et al., 2009; Perna, 2013). Cossignani and Ardovini
(2011) also reported a specimen generically stating a provenience
as from Israel. Bogi and Galil (2013) listed a record from Mienis and
Zaslow (2004), but no records were published in that article (C.
Bogi, pers. comm.). Scaperrotta et al. (2009) listed it from Israel,
Turkey, Lebanon and Cyprus, misunderstanding the distribution of
the other alien Pyrunculus fourierii (Audouin, 1826) (C. Bogi, pers.
comm.), and therefore a presence from these additional countries,
except those listed before, should be excluded. Exact locations and
geographic coordinates of conrmed Mediterranean records (both
published and new data) are reported in Table 1 and Fig. 1,asto
facilitate indexing in existing databases, such as EASIN (European
Alien Species Information Network: see Katsanevakis et al., 2015).
3.4. Diagnosis
Small shell (height of the largest examined sh eMarsa Fijab,
Sudan e3.3 mm) (Fig. 2AeB) usually with cylindrical outline,
variably slender, but generally stubby and anteriorly slightly
swollen. Body whorl with sides from weakly sinuous to nearly
straight. More or less truncated posteriorly (Fig. 2E). Spire sunken
in an apical umbilicus (see Tringali and Oliverio, 2001). Aperture
slightly protruding posteriorly. Very narrow and shallow umbilical
chink at the base, nearly concealed by the columellar callus; occa-
sionally slightly more opened. Columellar callus slightly oblique,
thin or weakly thickened, with no fold. Sculpture consisting of
close-set spiral lines crossing axial riblets, covering the whole shell.
Variable sculpture strength, with riblets sometimes very protrud-
ing or closer one to each other.
3.5. Remarks
The taxon Bulla desgenettii was originally introduced by Audouin
(1826) based on a reference to Savigny's plates on Egyptian molluscs
(Savigny, 1817: plate 5, gure 6; see also Pallary, 1926). As for other
species introduced by the same author, Retusa desgenettii (Audouin,
1826) may be found quoted with two different dates (1826 or 1827).
However, according to Sherborn (1897) and Bouchet and Danrigal
(1982), the earlier year is the one to be used. Pallary (1926) pro-
posed an emendation in Retusa desgenettesi, since the species
was named after Mr. Desgenettes, arguably Ren
e-Nicolas
Dufriche, Baron Desgenettes (1762e
1837), medical doctor in chief of
Napoleon's Egyptiancampaign. However, since unnecessary, the use
of R.desgenettesi is to be avoided. Its attribution to the genus Retusa
T. Brown, 1827 was denitively conrmed by Tringali and Oliverio
(2001) by the analysis of gizzard plates.
R.desgenettii shells are easily distinguished from those
belonging to other Mediterranean retusid species. Those previously
ascribed to Cylichnina Monterosato, 1884 ebut now regarded as
members of Retusa T. Brown, 1827 echaracterized by small sizes
and spire sunken in an apical umbilicus, are discussed in another
article of the present issue. All those species lack the evident
sculpture of R.desgenettii, with well marked axial riblets combined
with spiral lines (for discussions see Crocetta et al., 2015). On the
contrary, with regards to those considered as belonging to Retusa
sensu stricto, clear differences occur [R.desgenettii and other seven
species: Retusa candidula (Locard, 1892), Retusa leptoeneilema
(Brusina, 1866), Retusa mammillata (Philippi, 1836), Retusa minu-
tissima (Monterosato, 1878), Retusa obtusa (Montagu, 1803), Retusa
pellucida (T. Brown, 1827) and Retusa truncatula (Brugui
ere, 1792) e
see Coll et al., 2010; authorities and years by WoRMS except R.
pellucida; and the puzzling Retusamultiquadrata Oberling, 1970,
not included by Coll et al., 2010 and discussed here following the
genus used in the original description]. Retusa multiquadrata
Oberling, 1970, originally described from La Franqui Beach (Aude,
southern France), is a problematic taxon due to the telegraphic
description not matching with any original gure and the absence
of its type material in the Oberling coll (NMBE eauthors' personal
observation). Until few years ago, its identity has been mostly
assessed on the basis of the denitive identication proposed by
Buzzurro and Greppi (1997) (see Fig. 2H) and in agreement with
Nordsieck (1972). However, Ortea et al. (2013), while describing
Notodiaphana atlantica Ortea, Moro and Espinosa, 2013 from the
Atlantic Ocean, re-opened the question and considered
R. multiquadrata anomen dubium. Also Micali (2014), although
suggested that R. multiquadrata and N.atlantica may be synonyms,
stated that N.atlantica is the name to be used until Oberling's type
material will be traced and studied. Whatever will be the true
identity of R.multiquadrata, the general shape, the more rapidly
growing whorls, the true reticulate sculpture and the slender
columella [as based on Oberling (1970, 1971) descriptions] are
clearly different from R.desgenettii. Moreover, further analysis
needs to be conducted on Retusa robagliana (P. Fischer in de Folin
and P
erier, 1869), that could be an additional synonym of R.multi-
quadrata.Retusa candidula (Locard, 1892) [ ¼Bullina laionkaireana
Basterot, 1825 sensu Locard (1886)] was briey described, but not
originally gured, from the Atlantic coast of France (Locard, 1892).
Vald
es and H
eros (1998) rst published a syntype (MNHN-IM-
2000-28257). It comes from Ile de R
e (Bay of Biscay, France) and was
also hereby reported (Fig. 2I). According to Dautzenberg and
Durouchoux (1914),Jeffreys (1869: plate 94, gure 4) gured R.
candidula as Utriculus obtusus var. laionkaireana.Dautzenberg and
Durouchoux (1914) also published a photo of R.candidula and of
an intermediate shell with R.obtusa, but these specimens seem not
to match Locard syntype. Sabelli et al. (1990e1992) also considered
it a species of dubious validity. It therefore may be either a synonym
of R.obtusa or a distinct species closely related to the latter. In both
cases it does not share with R.desgenettii the typical sculpture with
well marked spiral lines and axial riblets, as well as the apical
umbilicus. Furthermore, the presence of R. candidula in the Medi-
terranean Sea is very doubtful, and we are prone to exclude it from
the Mediterranean fauna until well documented records. Retusa
mammillata (Philippi, 1836), a valid species sometimes erroneously
synonymised with R.truncatula (e.g. Lemche, 1948; Mikkelsen,
1995), is the sole species of the group sculptured with spiral lines,
yet it is devoid of axial riblets. Its shell is very variable posteriorly,
Table 1
Localities, dates, geographic coordinates (as originally reported) and bibliographic
references of records shown in Fig. 1.
N References Localities Dates Coordinates
1Mienis, 2004 Bardawil Lagoon 12/1969 e
2Bogi and Galil, 2002 Haifa Bay ee
2Bogi and Galil, 2002 Haifa port ee
2Bogi and Galil, 2002 Ashkelon ee
2Bogi and Galil, 2002 Akko ee
3Bogi and Galil, 2006 Agan 09/2004,
09/2005
31.51N e34.39E
3Bogi and Galil, 2006 Via Maris 05/2004,
09/2004
31.56N e34.41E
3Bogi and Galil, 2006 Samedan 12/2005 31.46N e34.19E
3Bogi and Galil, 2006 Atlit Neve-Yam 02/2006 e
3Bogi and Galil, 2006 Haifa Port ee
4Bogi and Galil, 2007 Haifa Bay 08/2006 32
49.246N e
350
01.187E
5Scaperrotta et al., 2009 Palmahim ee
5Scaperrotta et al., 2009 Haifa Port ee
6Perna, 2013 Haifa Bay 2009 e
present paper Bozburun 08/2002 36
41
0
N-28
02
0
E
F. Crocetta, L.P. Tringali / Quaternary International xxx (2015) 1e63
Please cite this article in press as: Crocetta, F., Tringali, L.P., Mapping alien Mollusca distribution in the Mediterranean Sea: the Lessepsian
immigrant Retusa desgenettii (Audouin, 1826) reaches Turkey, Quaternary International (2015), http://dx.doi.org/10.1016/j.quaint.2015.03.009
with specimens displaying from a sunken spire (with the exception
of the protoconch) to a prominent (Acteocina-like) spire, even
within the same population (Tringali and Oliverio, 2001)(Fig. 2JeK).
Shells with sunken spire, nevertheless, differ from R.desgenettii in
lacking an apical umbilicus, displaying a peculiar protoconch that
protrudes above the top. R.mammillata shape is also more slender
and evenly cylindrical. All the other above mentioned species,
except R.multiquadrata, lack both a spiral sculpture and an apical
umbilicus, with the partial exception of Retusa minutissima (Mon-
terosato, 1878). The latter, along with R.mammillata, shows a very
variable top, with a spire ranging from protruding to sunkenwithin
an apical umbilicus (Oliverio and Tringali, 2001) - intermediate
shells with at spire, or nearly so, are, nevertheless, the most
common. However, even the shells with apical umbilicus are
promptly identied on account of the tiny size, much smaller than
R.desgenettii, and of the absence of spiral lines. The shape is
generally less swollen anteriorly and the body whorl outline is less
sinuous at the sides (Fig. 2LeN). Retusa obtusa (Montagu, 1803) is
closely related to R.minutissima. It is usually considered a wide-
spread species ranging from the European coasts up to the North
Pacic, that has been widely reported from the Mediterranean Sea
too (e.g.: Carus, 1893; Hidalgo, 1917; Pruvot-Fol, 1954; Oberling,
1962; Nordsieck, 1972; Piani, 1980; Cattaneo-Vietti and Thompson,
1989; Sabelli et al., 1990e1992; Koutsoubas and Koukouras, 1993;
Bedulli et al., 1995; Sammut and Perrone, 1998; Cachia et al., 2001;
Cervera et al., 2004; Repetto et al., 2005; Coll et al., 2010). However,
R.obtusa lacks a planktotrophic larval stage, having direct larval
development (Smith, 1967) and therefore suggesting that the wide
published geographic distribution is doubtful. The analysis by one
of us (LPT) of Mediterranean material ascribed to R.obtusa, and
preserved in several Italian collections, invariably revealed
misidentication of R.minutissima (Monterosato, 1878), R.lep-
toeneilema and/or the protruding-spire form of R.truncatula
(Brugui
ere, 1792) from Djerba Island (Tunisia) (see also Oliverio and
Tringali, 2001). The inclusion of R.obtusa within the Mediterranean
fauna presumably spread after Jeffreys (1870).Herst considered R.
minutissima a dwarf form with at spire of Utriculus obtusus, and
named it as a varietas minor, apice depressoof the latter (see also
Monterosato, 1878). Later on, Jeffreys (1877) added also R.lep-
toeneilema to the synonymy of R.obtusa, although he had previously
regarded R.leptoeneilema as an apparent synonym of R.truncatula
(see Jeffreys, 1867). His view was followed by Carus (1893), who
quoted R.obtusa as Mediterranean, and by the key work on
Northern and Arctic Cephalaspidea by Lemche (1948). The latter
listed both R. leptoeneilema and R.minutissima among the synonyms
of R.obtusa, and his view arguably spread on a large part of the
following works which dealt with Mediterranean retusid gastro-
pods. Further examples of confusion between R.minutissima and R.
obtusa can be found in Thompson et al. (1985), that listed a Retusa
agg.from the Patras Gulf and the Ionian Sea as resembling to R.
obtusa, and in Oberling (1962), that listed Retusa obtusa var.from
Greece. The rst mentioned record clearly belongs to R.minutissima,
as arguably is also the case of the record in Oberling (1962),
although subsequent authors (e.g. Koutsoubas and Koukouras,
1993) quoted the latter as belonging to R.obtusa overlooking any
additional remarks. However, R.minutissima and R.leptoeneilema
are close to R.obtusa, but clearly distinct (see notes on Utriculus
minutissimus Monterosato in Oliverio and Tringali, 2001). Therefore,
since no actual evidences of the occurrence of R.obtusa sensu stricto
in the Mediterranean wereever provided, the species should not be
considered as a Mediterranean inhabitant. Compared with R.des-
genettii,R.obtusa is larger, with a proportionally thinner columella
and the spire is usually low to well prominent, not sunken in an
apical umbilicus. It also lacks the sculpture of the Lessepsian species
(Fig. 2O). Retusa truncatula (Brugui
ere, 1792) has generally a more
abruptly truncated shell and a more sinuous outline. Its spire is
slightly concave, thus lacking an apical umbilicus. Furthermore, it
does not bear spiral lines. The sculpture is composed by more or less
protruding axial riblets vanishing anteriorly, and faint growth lines
in the interspaces (Fig. 2PeQ). Retusa leptoeneilema (Brusina, 1866)
is similar in sculpture pattern to R.truncatula, but with generally
thinner and more numerous axial riblets. It is very abruptly trun-
cated posteriorly and the spire is generally very at or nearly so, but
never umbilicated. Moreover, the columellar callus is usually much
more thick than R.desgenettii (Fig. 2R). Retusa pellucida (T. Brown,
1827) has been recently discussed by Chaban and Nekhaev (2010).It
is an European species presumably not present in Mediterranean,
displaying a shape similar to R.truncatula. However, it is sculptured
by growth lines only, lacking the characteristic axial riblets of the
latter (Fig. 2S). The general shape and the sculpture distinguish it
from R.desgenettii.
Finally, the Lessepsian immigrant Pyrunculus fourierii (Audouin,
1826), also found in the same sediment from Bozburun (Fig. 2C),
shares the sculpture with R.desgenettii, but it is easily distinguished
by being more slender and pear-shaped, with an aperture further
protruding posteriorly, and the whorls growing more abruptly
(Fig. 2F). Furthermore, it posteriorly has a wider and deeper apical
umbilicus and is encircled by a weak but evident recess, all char-
acters lacking in R.desgenettii (see Tringali and Oliverio, 2001; Bogi
and Galil, 2002). Finally, gizzard plates are provided of only two
tubercles, as characteristic of the genus Pyrunculus Pilsbry, 1895
(see Crocetta et al., 2015). Empty shells of a third Lessepsian
cephalaspidean species were also found in the sample from Boz-
burun, belonging to Acteocina mucronata (Philippi, 1849) (Family
Cylichnidae H. Adams and A. Adams, 1854) (Fig. 2D). However, the
latter shows a slender cylindrical shape, a characteristic mucronate
apex, whorls with channeled shoulder, markedly plicated under the
sutures, and is not posteriorly swollen (Fig. 2G) (van Aartsen et al.,
1990; Zenetos et al., 2004).
4. Discussion
Biological invasions are severely affecting Europe, impacting
biodiversity, ecosystem services, economy and human health (Vil
a
et al., 2010; Katsanevakis et al., 2014). The Mediterranean Sea itself
is now under siege due to a continuous alien pressure, mostly due
to the opening of the Suez Canal, aquaculture and ship transport
(Galil, 2009; Zenetos et al., 2012). The bulk of introduced organisms
are thermophilic species of Indo-Pacic origin, coming from the
Red Sea through Lessepsian migration. Originally conned to the
Levantine shores, several species are now spreading all over the
Mediterranean, favoured by a general warming of the Mediterra-
nean Sea (Occhipinti-Ambrogi, 2007; Raitsos et al., 2010).
Constantly updated data on distribution of alien species are reliable
information to assess their status, population dynamics and ecol-
ogy features. In fact, trends in abundance, temporal occurrence and
spatial distribution in the wild, notably in risk areas, may aid the
tracking of the origin and source of alien species and the moni-
toring of the impacts. The same data represent a strong basis to
assess invasiveness and propagule pressure and to provide rec-
ommendations for management measures (Lee et al., 2008;
Simpson et al., 2009; Hulme and Weser, 2011; Gatto et al., 2013;
Ojaveer et al., 2014).
The role of citizen scientists and molluscan amateurs in
observing and tracing variations in Mediterranean biodiversity, as
well as in assessing the correct distribution of alien and native
species, has been previously highlighted in several papers (e.g.
Albano, 2010; Crocetta, 2012; Zenetos et al., 2013), and their
contribution to the knowledge of the Mediterranean molluscan
fauna is still central. The presence of a lot of Retusa desgenettii
F. Crocetta, L.P. Tringali / Quaternary International xxx (2015) 1e64
Please cite this article in press as: Crocetta, F., Tringali, L.P., Mapping alien Mollusca distribution in the Mediterranean Sea: the Lessepsian
immigrant Retusa desgenettii (Audouin, 1826) reaches Turkey, Quaternary International (2015), http://dx.doi.org/10.1016/j.quaint.2015.03.009
(Audouin, 1826) from Turkey in a private Italian collection adds
another piece to the matter, better dening the Mediterranean
spread pattern of the taxon. There is no certainty, at present,
regarding the possible vector of arrival of R.desgenettii in Turkey.
Indeed, previously known populations are too far away for natural
range extension to operate. However, since Bozburun is quite far
from any commercial route, the most probable possibility is that
this taxon may live elsewhere in the Mediterranean in as yet un-
discovered populations, and therefore may easily have colonized
Turkish shores via natural dispersal.
Acknowledgements
Gaetano Ambrosiano (Italy), Marco Oliverio (Italy), Mauro
Pizziniy(Italy), Stefano Runi (Italy) and Ruggero Ruggeriy(Italy)
helped with material and SEM photographs. Cesare Bogi (Italy)
kindly communicated misunderstandings on Retusa desgenettii
published distribution. Henk Mienis (Israel),
Angel Vald
es
(Pomona, California) and Argyro Zenetos (Greece) sent requested
articles. Virginie H
eros (Paris, France) and Manuel Caballer (Paris,
France, project E-RECOLNAT: ANR-11-INBS-0004) provided photos
of the syntype of Cylichna candidula. Elena Chaban (Russia) pro-
vided unpublished photos of Retusa pellucida. She also helped to
improve the article, as well as an anonymous reviewer. Paolo Cro-
vato (Italy), Willy Segers (Belgium), Frank Swinnen (Belgium) and
Roland De Prins (Belgium) authorised the reproduction of photos
of native northeastern Atlantic-Mediterranean Retusa sensu
stricto published on Bollettino Malacologico (Italy) and of
Retusa multiquadrata on Marine Molluscs of Madeira.
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Please cite this article in press as: Crocetta, F., Tringali, L.P., Mapping alien Mollusca distribution in the Mediterranean Sea: the Lessepsian
immigrant Retusa desgenettii (Audouin, 1826) reaches Turkey, Quaternary International (2015), http://dx.doi.org/10.1016/j.quaint.2015.03.009
... Retusa canariensis (F. Nordsieck and F.G. Talavera, 1979) is the only species that lacks a true apical umbilicus and shows a more typical Retusa outline (see discussion in Crocetta and Tringali, 2015), therefore being different from the others, whilst Retusa tenerifensis (F. Nordsieck and F.G. Talavera, 1979) H eros, 1998). ...
... With regards to the other species, all but Retusa nitidula (Lov en, 1846) show more or less numerous spiral lines, simple and slightly flexuous. It is the case of Retusa crebrisculpta (Monterosato, 1884) (see Monterosato, 1884;Oliverio and Tringali, 2001), Retusa crossei (Bucquoy, Dautzenberg & Dollfus, 1886) (see Bucquoy et al., 1886;Gaglini, 1991), Retusa laevisculpta (Granata-Grillo, 1877) (see Granata-Grillo, 1877;Gaglini, 1991; authors personal observation on 2 syntypes: Fig. 3JeK) and the puzzling Retusa multiquadrata Oberling, 1970(see Oberling, 1970, often forgotten by recent authors (see discussions in Crocetta and Tringali, 2015). Retusa robagliana (P. ...
... Retusa robagliana (P. Fischer in de Folin and P erier, 1869) is a poorly-known Cylichnina-like species described from the Bay of Biscay, which bears a network of weak axial ribs and spiral lines, thus not fitting R. parvula, but possibly being conspecific with R. multiquadrata (see discussions in Crocetta and Tringali, 2015). Retusa umbilicata (Montagu, 1803) is the oldest available name in the Northeastern AtlanticeMediterranean for all Retusa species with an apical umbilicus. ...
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To date, the knowledge of the biodiversity of Cretan Archipelago sea slugs and shelled relatives is poor in comparison to other parts of the Greek seas and to the Mediterranean Sea in general. Based on an extensive review of literature data, complemented by recent field observations, we provide an updated checklist of 81 taxa from the Cretan Archipelago, 11 of which constitute new records. Careful attention has been given to molluscan species described from the area (four taxa, two of which valid), as well as to doubtful records (five taxa). Finally, taxonomic remarks are offered for Bulla vestita Philippi, 1840, Cylichna parvula Jeffreys, 1883 and Bulla girardi Audouin, 1826. B. vestita has priority over Bulla retifer Forbes, 1844, that is definitively considered a junior synonym of the former. C. parvula is redescribed, changed of family (from Cylichnidae H. Adams & A. Adams, 1854 to Retusidae Thiele, 1925), first moved to the genus Retusa T. Brown, 1827 and compared with similar congeneric species. Within this framework, we also figure a syntype of Cylichna laevisculpta Granata-Grillo, 1877 for the first time. Finally, the attribution of B. girardi to the genus Ventomnestia Iredale, 1936 is discussed and its establishment status in Greece is re-evaluated. The present paper lays the foundations to extend local studies on sea slugs and shelled relatives and fills some expected gaps in the Mediterranean distribution of several taxa. It therefore constitutes a mandatory step when providing large-scale and well-defined Mediterranean molluscan distributional patterns, and emphasizes the necessity of more intensive studies of the molluscan communities in the area.
... This high number can be easily detected also in Turkish waters: a total of 1065 mollusc species had been recorded along the Turkish coasts, of which 118 had been stated as species with alien origin in the checklist by Öztürk et al. (2014). Later Ozturk et al. (2015 reported four more alien molluscs and Crocetta & Tringali (2015) added one more to the Turkish fauna. Among mollusc species recorded herein, two of them are alien, namely Crithe cossinea and Monotygma fulva. ...
... The present study contributes to Turkish mollusc fauna by the addition of six more species (namely Crithe cossinea, Melanella alba, Mangelia callosa, Mangelia tenuicosta, Clathromangelia loiselieri, Raphitoma bicolor). Thus, the number of mollusc species of the Turkish coasts increased from 1065 (Öztürk et al., 2014) to 1076, of which 124 aliens (Crocetta & Tringali, 2015;Öztürk et al., 2015;present study) in only one year. ...
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The whole molluscan assemblages along the Turkish coasts of the Aegean Sea and the Levantine Sea (Southern Turkish coasts), were studied from 20 stations at depths ranging from 11 m to 69 m, between August and October 2014. This has resulted in new contribution to Mediterranean marine molluscan fauna. Crithe cossinea is a new lessepsian for the Mediterranean Sea, five Gastropoda (Melanella alba, Mangelia callosa, Mangelia tenuicosta, Clathromangelia loiselieri, Raphitoma bicolor) are new records for Turkish Seas, two Gastropoda (Ondina obliqua, Retusa nitidula) are new records for the Aegean Sea while another two Gastropoda (Alvania hispidula, Vexillum hypatiae) are new records for the Turkish coast of the Aegean Sea and four Gastropoda (Cerithiopsis fayalensis, Bela menkhorsti, Raphitoma aequalis, and the alien species Monotygma fulva) are new records for the Turkish coasts of Levantine Sea. Among Bivalvia species, Thyasira alleni is a new record for both seas and Pitar mediterraneus is a new record for the Turkish coasts of Levantine Sea. The present study contributes to molluscan fauna of Turkish waters by the addition of six more species, increasing their number to 1076.
... This result should not be considered surprising as many molluscan groups of the Mediterranean Sea have not been fully subjected to a focused review based on literature and modern genetic methods, and Mediterranean checklists are often still being compiled. In addition, deletion of species reported in local, national, or Mediterranean checklists is an ongoing and time-consuming process necessary towards a homogenization of the general knowledge of the Mediterranean malacofauna [31,[114][115][116][117][118][119][120]. ...
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The precise number of Okenia taxa inhabiting the Mediterranean Sea, as well as their general taxonomy, varies according to different specialists. So far, eight valid species have been reported from the area: Okenia aspersa (Alder & Hancock, 1845), Okenia cupella (Vogel & Schultz, 1970), Okenia elegans (Leuckart, 1828), Okenia hispanica Valdés & Ortea, 1995, Okenia impexa Er. Marcus, 1957, Okenia leachii (Alder & Hancock, 1854), Okenia mediterranea (Ihering, 1886), and Okenia zoobotryon (Smallwood, 1910). Of these, only three (O. elegans, O. hispanica, and O. mediterranea) have their type localities in the Mediterranean Sea, whereas the others were described from different biogeographic areas and later included in the Mediterranean biota. We carried out a review on Mediterranean Okenia species through an integrative approach, based on a wide literature search and a morphological and molecular analysis of available type material and samples collected recently. The present study confirmed the presence of O. aspersa, O. elegans, O. hispanica, and O. mediterranea in the Mediterranean Sea, although leaving remaining questions about some of those taxa. The distribution of O. cupella, O. impexa, and O. zoobotryon is limited to the western Atlantic, and of O. leachii to the eastern Atlantic. All specimens previously identified as O. cupella, O. impexa, and O. zoobotryon by different authors in the Mediterranean Sea were repeatedly misidentified. Thus, we describe Okenia problematica sp. nov. and Okenia longiductis sp. nov., from the “Mediterranean” Okenia cupella/impexa and O. zoobotryon. We also consider here Okenia pusilla Sordi, 1974 a nomen dubium and include a redescription of the holotype of O. cupella. A molecular phylogeny, including all the sequenced Okenia species, was performed in order to evaluate the evolutionary relationships of the newly described species with the other congeneric taxa.
... The key role of amateur malacologists in observing and recording variations in local biodiversity, as well as in contributing to new distribution data, is still central in the Mediterranean Sea (e.g. see Crocetta, 2011Crocetta, , 2012Crocetta and Tringali, 2015), and is here confirmed by the present paper. However, as highlighted in the literature review carried out, the true Mediterranean distribution of this species still remains unknown or partially questionable, and lack of past and recent field studies along the Mediterranean shores of Libya and Egypt, as well as under-sampling along the northern Tunisian coastline, have also widely contributed to the statements discussed in the introduction. ...
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Background The known historical range of Siphonaria pectinata in the Mediterranean basin is unclear so far. Confirmed records come from the Strait of Gibraltar, the African coastline up to Algeria and the Spanish coastline up to Murcia/Valencia area, whilst all those published from additional Mediterranean areas are affected by a high degree of uncertainty. In addition, this taxon occurs in Tunisia (northern shores up to Cap Bon area), Greece (Saronikos Gulf) and Croatia (Split area), where it has been sighted only recently. The three latter records were widely discussed in the current literature due the possible rationale at the basis of the absence of past sightings, and there is a general agreement in considering that the Greek and Croatian records are the result of a human induced introduction. Results A literature overview on the Mediterranean distribution and alien status sensu lato of the striped false limpet Siphonaria pectinata is here provided for the first time. Concomitantly, the presence of this taxon in Croatia is here shown to date back to 1978 on the basis of material preserved in private collections, and at least to 1960–70 on the basis of local knowledge of Croatian malacologists and shell sizes of specimens collected in 1978. The findings reported in the present paper overall backdate by ca. 30–40 years the presence of this taxon in the Adriatic Sea, and also constitute the first confirmed record of the striped false limpet from the entire northern Mediterranean shores. Conclusions The present note corroborates the key role of citizen scientists in observing and recording variations in local biodiversity, as well as in contributing new and past distributional data, and concomitantly suggests the necessity of further work in the Mediterranean area to assess the local species distribution and pattern of spread before its designation as alien sensu lato.
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Notodiaphana atlantica and Liloa mongii are two cephalaspidean species described respectively from the Atlantic Ocean and the Red Sea, and considered widespread in their native ranges. Both species have also been recently recorded from the Mediterranean Sea, prompting some authors to consider them alien. Notwithstanding clear morphological differences in their shells, the two species have often been confused or misidentified in the literature, or specimens have been described with incorrect locality data. We hereby review the occurrence, distribution and status of both species in the Mediterranean Sea based on published data and examination of new material. Notodiaphana atlantica is considered a cryptogenic species with a range spanning from the western to eastern part of the basin. The presence of L. mongii in the Mediterranean is questioned until specimens that can be reliably assigned to this taxon or to any congeneric species are found in the area. Alien species inventories play an important role in regional policy and management decisions, thus requiring a high degree of confidence in the validity of species identification and their non-indigenous status. The present paper adds further evidence of the excess of “bibliographically introduced” alien records and reiterates the need for periodic re-evaluation of published data.
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This study deals with the alien mollusc species recorded along the Turkish coast after the last checklist published in 2014. Six species (Lodderia novemcarinata, Eratoena sulcifera, Zafra obesula, Z. pumilla, Retusa desgenetti, and Martesia striata) were added to the alien mollusc fauna of the Levantine coast of Turkey, two species (Leucotina natalensis and Pyrunculus fourierii) were recorded along the Aegean coast of Turkey and one species (Arcuatula senhousia) was found in the Sea of Marmara. The present study is also the first report of Varicopeza pauxilla (Gastropoda: Cerithiidae) from the Mediterranean Sea. This gastropod species, which originates from the Indo-West Pacific Ocean, was found in İskenderun Bay (Levantine coast of Turkey). With the above-mentioned species, the total number of alien molluscs along the Turkish coast amounts to 125 species.
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We herein review the Adriatic opisthobranch fauna, provide an updated checklist of 223 species and assess their distribution at regional and country levels. New Adriatic records are provided for 67 opisthobranch taxa, adding three new records for the Italian coastline, five new records for Albania, eight for Croatia and 15 for Montenegro. The presence of Hermaea bifida (Montagu, 1815), Hermaea variopicta (Costa A., 1869) and Facelina annulicornis (Chamisso & Eysenhardt, 1821) is reported for the first time from anywhere in the Adriatic Sea. Including the new findings, our inventory includes 28 species from Albania, 163 from Croatia, 178 from the Italian coastline of the Adriatic, 41 from Montenegro and 74 from Slovenia. No records were available from Bosnia and Hercegovina. Ninety species (40.4%) are widespread, and were recorded from all three main divisions (Northern, Western and Eastern Adriatic), whilst 79 species (35.4%) were reported from only one of them. At sub-division levels, the Albanian inventory is the most dissimilar to the other country/regional lists, presumably because of the lack of targeted field surveys. The highest similarity is observed amongst the Western Adriatic, Croatia and the Italian Ionian coastline. Seven alien, one possible alien and three cryptogenic opisthobranchs were reliably recorded from the Adriatic Sea. The first Mediterranean records of five species were in the Adriatic Sea, of which four species have not been found elsewhere in the Mediterranean. Shipping and aquaculture are the probable pathways for most of the alien species. A steady rate of one to two alien introductions per decade since the 1970s was evident. The Northern Adriatic coasts are the most affected by alien invasions, probably due to repeated local introductions along with shellfish transfers (oysters, mussels, Manila clams), and heavy maritime transport.
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A reviewed knowledge of the opisthobranch species from Lebanon (eastern Mediterranean Sea), based on literature records (scattered throughout various papers published over a period of more than 150 years) and recently collected material (1999-2002 within the CEDRE framework and other samples), is presented, yielding a total number of 35 taxa recorded from the Lebanese shores identified to species level. Special emphasis has mainly been given to the alien species, for which scattered notes are also given. The known opisthobranch biota is composed of 22 native (~ 63%), 12 alien (~ 34%) and one cryptogenic (~ 3%) taxa. Eleven of these (Berthella aurantiaca, B. ocellata, Aplysia fasciata, Felimare picta, Felimida britoi, F. luteorosea, F. purpurea, Phyllidia flava, Dendrodoris grandiflora, D. limbata and Aeolidiella alderi) constitute new records for the Lebanese fauna, whilst the examined material of a further seven species (Elysia grandifolia, Pleurobranchus forskalii, Aplysia dactylomela, Bursatella leachii, Syphonota geographica, Goniobranchus annulatus, Flabellina rubrolineata) anecdotally cited from Lebanon on the basis of the samples here studied, is here first explained. One additional taxon belonging to the genus Haminoea has been identified to genus level only. Despite the searching effort poning the basis of the material analyzed here, data reported clearly suggest that strong investments are still needed for a better understanding of the eastern Mediterranean opisthobranch fauna.
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The project for a revision of the types of marine species described by T. Di Maria, known as Monterosato, kept in the Museo Civico di Zoologia, Roma (ZMR) is presented, with the purpose of providing a clear check-list of these types with the best possible iconography. The problems encountered while carrying out the project are reported, together with comments on the problematic history of the Monterosato collection. In this first part, the types of the opisthobranchs have been examined. Monterosato introduced ten available specific names, and an infrasubspecific name, raised to subspecific rank by F. Nordsieck before 1985, now regarded as belonging to the opisthobranchs. They are: Acteon candiddus Monterosato, 1923, Ringicula conformis Monterosato, 1877, Cylichnina crebrisculpta Monterosato, 1884, Haminoea hydatis var. cymoelium Monterosato, 1923, Spirialis diversa Monterosato, 1875, Coleophysis effusa Monterosato, 1890, Philine intricata Monterosato, 1884, Utriculus minutissimus Monterosaro, 1878, ex H. Martin MS., Philine monterosati Monterosato, 1874, ex Jeffreys MS., Amphispyra quadrata Monterosato, 1874, Philine striatula Monterosato, 1874, ex Jeffreys MS. Type material of all the species have been found in the Monterosato coll. (ZMR), and is here documented. The authors preliminary discuss the identity of the mentioned specific names.
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During the Napoleonic campaign to Egypt a collection of Red Sea, Mediterranean and continental mollusks was brought together by Savigny who published upon them in 1817 as folio engravings. These served as type-figures for a number of species described by 19th century malacologists, including Audouin, Ehrenberg, Deshayes, Philippi, Hupé, Landrin, Jonas, Issel, Morlet, Vaillant, P. Fischer, Tapparone-Canefri, von Martens, Weinkauff, Monterosato, Jousseaume, H. Fischer and finally Pallary. A checklist and illustrations of 86 of these original types from the Savigny collection, now in the Paris Museum, are presented, supplemented by reproductions of the unpublished color vellums of opisthobranchs and cephalopods.
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The present work is an attempt to update the check-list of the Mediterranean species of Pyrunculus Pilsbry, 1895. The species have been ascribed to the genus on the base of: (a) the small sized bubble-shell, characteristically pear-shaped; (b) the gizzard plates (three), subtriangular in shape, corneous, light brown coloured, with two darker blunt tubercles. Three members of the genus are considered as present in the Mediterranean Sea: Pyrunculus ovatus (Jeffreys in W.B. Carpenter & Jeffreys, 1871), P. hoernesii (Weinkauff, 1866), and P. fourierii (Audouin, 1827). P. ovatus is still living in the Atlantic, but is possibly extinct in the Mediterranean waters. Cylichna obesiuscula Brugnone, 1877, is regarded as a form of P. ovatus, as probably is also Cylichna obscura Sykes, 1904. The view of TRINGALI (1993) that Cylichna hoernesii Weinkauff, 1866, should be assigned to Pyrunculus is confirmed. Cylichna cuneata Tiberi, 1868, is a synonym of P. hoernesii. Bulla fourierii Audouin, 1827, usually included in Retusa, is assigned to Pyrunculus basing on its gizzard plates. The shell morphology itself does not allow to give this systematic position. The species is a Lessepsian migrant, apparently well-acclimatised in the Levant Sea, and widespread through the Indo-Pacific waters. There are other more recent names possibly available for P. fourierii: Bulla decussata A. Adams, 1850, Utriculus simillimus R.B. Watson, 1883, Cylichna protumida Hedley, 1903, all to be checked on the type material. The statement by BOGI & KHAIRALLAH (1987) that the Tunisian Retusa dilatata Pallary, 1904, and its variety minor Pallary, 1904, are synonyms of P. fourierii, is rebutted. Utriculus minutissimus Monterosato, 1878, considered by several workers as a Pyrunculus, must be removed from this genus, being a Retusa, as shown by both the shell and the gizzard plates morphology.
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Surveys carried out in the summers of 1981 and 1982 revealed 19 macrobenthic species, the most varied assemblage of infaunal and epifaunal opisthobranchs yet reported. The infaunal carnivore Philine aperta was the most prevalent opisthobranch in the area as a whole, followed closely by the herbivorous Haminea navicula and the carnivorous Weinkauffia diaphana. Some species, like Cylindrobulla fragilis, were purely herbivorous. Others were micro-carnivores, feeding on infaunal foraminiferans, annelids and bivalved molluscs (eg Cylichna cylindracea, Rhizorus acuminatus, Acteon tornatilis, Aglaja tricolorata, Retusa truncatula). Biogeographically there are 4 categories represented in the samples: 1) an indigenous Mediterranean component (27.8%), 2) a Mauretanian component (16.7%) , 3) a Lusitanian component (27.8%), and 4) a group of eastern Atlantic cosmopolitan species (27.8%), of which 2 species (11.1%) penetrate as far as the Black Sea.-from Authors