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108 Accepted by W. Sterrer: 31 Jan. 2014; published: 20 Mar. 2014
ZOOTAXA
ISSN 1175-5326 (print edition)
ISSN 1175-5334 (online edition)
Copyright © 2014 Magnolia Press
Zootaxa 3780 (1): 108–134
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Article
http://dx.doi.org/10.11646/zootaxa.3780.1.4
http://zoobank.org/urn:lsid:zoobank.org:pub:E1E25433-72CD-4592-B9C2-62F4D11F2D82
State of knowledge of the Acotylea (Polycladida, Platyhelminthes)
from the Mediterranean coasts of Spain: new records and new species
DANIEL MARQUINA1,3, DAVID OSCA1, JORGE RODRÍGUEZ1, ESTRELLA FERNÁNDEZ-DESPIAU2,
& CAROLINA NOREÑA1
1Departamento de Biodiversidad y Biología Evolutiva. Museo Nacional de Ciencias Naturales (CSIC), c/ José Gutierrez Abascal 2,
28006 Madrid, Spain
2c/ San Marcelino 11, 46017 Valencia, Spain
3Corresponding author. E-mail: danielmarquinahz@gmail.com
Abstract
Along the Mediterranean coast of the Iberian Peninsula, great species diversity is thought to exist, but our knowledge of
Iberian polyclads is, in fact, very limited. This study contributes to the Polycladida (Platyhelminthes) of the Iberian Pen-
insula, in particular those of the Mediterranean coast. Nine species, mainly new species or new records, are described.
Imogine stellae sp. nov. from Mar Menor (Murcia, Spain) is described, while I. mediterranea Galleni, 1976 is recorded
for the first time in Spain. The genus Planocera Blainville, 1828 within the Mediterranean basin is reviewed: Planocera
graffi Lang, 1879 is redescribed, and its synonymisation with Planocera pellucida (Mertens, 1833) considered. Also, the
genus Notoplanella Bock, 1931 is represented by two species in Spain, N. inarmata Bock, 1931 type species, from For-
mentera Island and N. estelae sp. nov., from Mar Menor. Trigonoporus cephalophtalmus Lang, 1884 is rediscovered after
the description of Lang (1884). Stylochus neapolitanus (Delle Chiaje, 1841-1844) Lang, 1884 is recorded and S. pilidium
(Goette, 1881) is also redescribed, and Leptoplana mediterranea (Bock, 1913) is newly recorded for the Iberian Peninsula.
Key words: Polycladida, marine flatworms, Iberian Peninsula, Mediterranean Sea, distribution, taxonomy
Introduction
Yungia dicquemari (Risso 1818) Lang 1884 and Thysanozoon brocchi (Risso 1818) Grube 1840 are possibly the
first reliable records for polyclads within the Mediterranean basin, although originally described within the phylum
Mollusca as Tergipes dicquemari Risso, 1818 and Tergipes brocchi Risso, 1818. Shortly thereafter, Stefano Delle
Chiaje (1822–1829) wrote an exhaustive study on invertebrates of the Kingdom of Naples. Several polyclad
species were described, but all were included in the genus Planaria, which was in the order Tricladida at the time.
Delle Chiaje wrote a similar study for Sicily in 1841 in which all of the described polyclad species were also
included in the genus Planaria.
In addition to the works of Delle Chiaje, Adolf Eduard Grube (1840) produced a compilation describing
marine invertebrates (mainly Actinia, Echinodermata and Vermes) of the Mediterranean and Adriatic Seas. In this
work, several polyclad species belonging to the genera Stylochus, Leptoplana and Thysanozoon were briefly
mentioned. Later, Jean Louis Armand de Quatrefages (1845) published an impressive study describing several
genera including Tricelis Quatrefage, 1845 (currently Cestoplana Lang, 1884), Polycelis Quatrefage, 1845
(including several species that nowadays belong to other genera of Polycladida), Prosthiostomum Quatrefages,
1845, Proceros Quatrefages, 1845 (currently Pseudoceros Lang, 1884), Eolidiceros Quatrefages, 1845 (currently
Thysanozoon Grube, 1840) and Stylochus Ehrenberg, 1831.
In 1884, Arnold Lang published a detailed study of polyclads from the Mediterranean Sea, particularly those
found in the Gulf of Naples. Lang's study marked a turning point in the field of polyclad taxonomy, as most of his
discoveries and results are still considered essential for systematic studies of this group within the Mediterranean.
Subsequent studies are highly specific or restricted because only a small number of species from localised regions
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ACOTYLEA FROM MEDI TERRANEAN COASTS OF SPAIN
were described. However, these studies are essential for understanding the distribution and biodiversity of
Mediterranean polyclads. These works include the description of Cestoplana raffaelei Ranzi, 1928 (currently
Acestoplana raffaelei (Ranzi, 1928)) from the Gulf of Naples, a review of polyclads from Sebastopol by Jakubova
(1909), especially his studies of the family Stylochidae, contributions by Ludwig van Graff (1886, 1889) on the
Polycladida of the Adriatic Sea, which includes a description of Enantia spinifera Graff, 1889 (Family Enantiidae
Graff, 1889), an extremely peculiar species (with cuticular spines along the body edge) that was found by that
author in the summer of 1876, but has never since been recaptured, and more recently, a revision of the genus
Leptoplana within the Mediterranean Sea (Gammoudi et al. 2012).
For the Iberian Peninsula, high invertebrate species diversity along the Mediterranean coast is recognised
(Hofrichter 2003), but our knowledge of Iberian polyclads is, in fact, very limited. The first comprehensive study
of the order Polycladida in the Iberian Peninsula is the thesis of Carles Novell (2003) in which 22 different
polyclad species found along the Catalan coast were recorded. Since then, few records for Iberian polyclads have
been published, though these include studies in which Echinoplana celerrima Haswell, 1907 is mentioned for the
first time (e.g., Gammoudi and Tekaya 2012).
In this study, we focus on the acotylean genera and species from the Mediterranean coast of the Iberian
Peninsula, specifically the coastline from Castellón to Almuñecar (Granada), including Mar Menor (Murcia, Spain)
and various islands (Fig. 1, Table 1).
Material and methods
Specimens of Imogine stellae sp. nov. were collected between and underneath old bricks and rubble covered with
periphyton and algae on the eastern seashore of Mar Menor, Murcia, (37º46’16.10’’N, 0º45’02.50’’W) in August
2011. The specimens were found in shallow warm waters from 0.2 to 0.4 metres deep and water temperatures of
approximately 30 ºC.
Specimens of Planocera graffi were collected on the seashore of Calpe at ‘Raco Beach’ (38º 38’07.26’’N, 0º
04’15.28’’ E), and near Cabo de Palos (37°37’49.11’’N, 0°41’46.38’’W) from waters 2 to 5 metres deep and a
water temperature of 20 ºC. They were found next to a Posidonia oceanica meadow, underneath rocks covered
with green epiphytic algae that were sitting on a sandy bottom.
Specimens were collected live, placed into plastic bottles and then transported to the laboratory. Animals were
fixed in Bouin’s fluid, following the Newman and Cannon method (Newman and Cannon 2003). Photographs were
taken of both live and fixed animals to retain maximum information regarding shape, colouration and internal
anatomy.
Notoplanella estelae sp. nov., Leptoplana mediterranea, Imogine mediterranea, Stylochus neapolitanus and
Stylochus pilidium were collected in Mar Menor (Murcia) during 2006, as part of the project titled: “Food web
reply to nutrient inputs in a coastal lagoon (EUTRO-COST)” (Ecology and Management of Coastal Marine
Ecosystems research group, University of Murcia. Principal Investigator: Angel Pérez-Ruzafa).
Notoplanella inarmata and Trigonoporus cephalophtalmus were collected over two periods, during Iberian
Fauna oceanographic campaigns III and IV in 1994 and 1996, respectively. Iberian Fauna oceanographic campaign
III (June–July 1994) occurred in the Baleares and Columbretes Islands, while Iberian Fauna oceanographic
campaign IV (June–July 1996) took place in the Columbretes and Hormigas Islands and Alborán Island. Samples
were obtained by SCUBA diving in depths from 0 to 44 metres, and from dredges up to 400 metres deep. In Mar
Menor, rocky surfaces were sampled by total scratching, while soft bottoms were sampled by dredging. Specimens
were fixed with 4% formaldehyde and preserved in 70% ethanol.
Specimens were subsequently embedded in paraplast, serially sectioned at intervals between 7 to 10 μm and
stained with AZAN (trichrome staining method). Reconstructions of internal anatomy were derived from serial
sagittal sections. Measurements were determined from fixed material.
Holotypes were deposited into the Invertebrate Collection of the Museo Nacional de Ciencias Naturales de
Madrid (MNCN) in Spain.
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TABLE 1. Acotylean species of the Mediterranean shores of the Iberian Peninsula.
Species Sites Coordinates Collection Substrate Depth
(m)
Discocelis tigrina (Blanchard, 1847)
Lang, 1884
Catalan coast 41°22’ N-02°11’ E;
41°40’ N-02°48’ E;
42°17’ N-03°16’ E
41°50’ N-03°08’ E
SCUBA diving Rocks, algae 0 -18
Pleioplana atomata (O. F. Müller,
1776) Faubel, 1983
Catalan coast 41°40’ N-02°48’ E SCUBA diving Rocks, Codium 0 - 15
Notoplana vitrea (Lang, 1884) Bock,
1913
Catalan coast 41°40’ N-02°48’ E SCUBA diving Rocks 15
Complana agilis (Lang, 1884) Catalan coast 41°40’ N-02°48’ E SCUBA diving Rocks, algae, Posidonia
oceanica
7 - 12
Hoploplana villosa (Lang, 1884)
Laidlaw, 1902
Catalan coast 41°40’ N-02°48’ E SCUBA diving Algae 9
Notoplanella inarmata Bock, 1931 Formentera Island (12 miles East) 38°45’ N-01°18’ E;
38°43’ N-01°18’ E
Dredging Rocks
126 - 134
Notoplanella estelae sp. n. Lo Pagán; (Mar Menor, Murcia) 37°48’ N-00°47’ W SCUBA diving Rocks 0.2 - 1
Leptoplana mediterranea Bock, 1913 Isla del Ciervo, Lo Pagán, Los Urrutias;
(Mar Menor, Murcia)
37°48’ N-00°47’ W;
37°40’ N-00°49’ W;
37°39’ N-00°44’ W
SCUBA diving,
dredging
Clays, Caulerpa prolifera 2
Trigonoporus cephalophthalmus Lang,
1884
Columbretes Islands, Hormigas Islands,
Alborán Island (3 miles North)
39°52’ N-00°40’ E;
37°39’ N-00°38’ W;
35°58 N-02°58 W
SCUBA diving Rocks 14.3;
23.5; 36
Planocera pellucida, Mertens, 1833 Calpe (Alicante, Spain) at the ‘Raco
beach’; Cabo de Palos (Murcia, Spain)
38º 38’N-0º04’ E SCUBA diving Underneath rock covered with
green epiphytic algae
2 - 5
Planocera ceratommata (Palombi,
1936) Faubel 1983
Catalan coast 41°40’ N-02°48’ E;
41°53’ N-03°11’ E
SCUBA diving Rocks, Codium 17
Imogine mediterranea Galleni, 1976 Los Urrutias; Mar Menor (Murcia,
Spain)
37°40’ N-00°49’ W SCUBA diving Rocks 0.2 – 0.5
Imogine stellae sp. nov. El Estácio; Mar Menor (Murcia, Spain) 37°46’N-0°45’W SCUBA diving Old brick and rubble covered
with periphyton
0.2 – 0.5
Stylochus neapolitanus (Delle Chiaje,
1841-1844) Lang, 1884
Los Urrutias; Mar Menor (Murcia,
Spain)
37°40’ N-00°49’ W SCUBA diving,
dredging
Rocks, Caulerpa prolifera 0.2 - 2
Stylochus pilidium (Goette, 1881) Los Urrutias; Mar Menor, (Murcia,
Spain)
37°40’ N-00°49’ W Dredging Caulerpa prolifera 2
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Systematics
Suborder ACOTYLEA Lang, 1884
Superfamily LEPTOPLANOIDEA Faubel, 1984
Family CRYPTOCELIDAE Laidlaw, 1903
Genus Notoplanella Bock, 1931
Notoplanella inarmata Bock, 1931
Figs. 1 (1), 2, 3
Material examined. One mature specimen sagitally sectioned, collected in Formentera Island from rocky substrate
found between 126–134 metres deep.
Morphological remarks. This specimen is consistent with Bock’s description of Notoplanella inarmata.
Unfortunately, the description was realized only on fixed material, therefore the information about the colour is
scarce. The fixed individual presents an oblong-oval body shape, lacking tentacles and whitish-grey background
colouration with reddish-brown speckles arranged in lines, diverging from the centre to the margins. Marginal band
and pharynx region free of pigment spots (Fig. 2A). Paired cerebral and tentacular eye clusters present (Fig. 2B,
3A). Pharynx ruffled central, oral pore at the posterior end (Fig. 2C).
Within the male reproductive system (Fig. 2D), a narrow duct connects the seminal vesicle to the prostatic
vesicle (Fig. 3B). The prostatic vesicle is interpolated, enlarged, with numerous secretory ducts. Unarmed penis
papilla (Fig. 3C). The female apparatus consists of a muscular external vagina, with the common oviduct clearly
differentiated and without Lang’s vesicle. Unlike to the description of N. inarmata from Cape Town (Bock 1931),
both gonopores, female and male, are well separated (Fig. 2D), and the musculature of the body wall surrounding
the female genital pore (Fig. 3D) is considerably thickened. This feature was also recognised by Prudhoe (1989),
when he examined specimen from Cape Province dredged in 19 metres deep, also from Danger Point and Saldanha
Bay.
Distribution. South Africa South Africa (Simon’s Bay, Bock 1931; False Bay, Day et al. 1970; Cape Province,
Danger Point, Saldanha Bay, Prudhoe 1989). This is the first record for the Mediterranean Sea.
Notoplanella estelae sp. nov.
Figs. 1 (2), 4, 5
Type locality. Lo Pagán, Mar Menor, 37°48’ N, 00°47’ W. Collected by SCUBA diving; from rocky substrate
found between 0.2–1 metres deep; Fig. 1 (2).
Type material. Holotype: one mature specimen sagittally sectioned; MNCN 4.01/200 to MNCN 4.01/215 (15
slides). Paratype: one mature specimen sagittally sectioned; MNCN 4.01/216- MNCN 4.01/231 (16 slides). Leg.
Angel Pérez-Ruzafa.
Material examined. Two mature (MNCN 4.01/200 to MNCN 4.01/215 (15 slides) and MNCN 4.01/216-
MNCN 4.01/231 (16 slides)) and two juvenile specimens sagittally sectioned. The material is deposited in the
invertebrate collection of Museo Nacional de Ciencias Naturales de Madrid (Spain). Collected by Angel Pérez-
Ruzafa.
Etymology. The specific epithet is dedicated to Estela Barroso, girlfriend of the first author.
Diagnosis. Notoplanella with numerous dark spots on the dorsal surface, except on the median line. With
nuchal tentacles. Tentacular and cerebral eyes present. A short duct links the seminal and the prostatic vesicles and
shows a dilatation before the prostatic vesicle. Large penis papilla. Female system with a small Lang’s vesicle.
Gonopores separated.
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FIGURE 1. Distribution map of examined specimens. General views of A the eastern coast of the Iberian Peninsula, B Mar
Menor (Murcia). Numbers: Notoplanella inarmata (1), Notoplanella estelae sp. nov. (2), Trigonoporus cephalophtalmus (3),
Leptoplana mediterranea (4), Planocera graffi (5), Imogine mediterranea (6), Imogine stellae sp. nov. (7), Stylochus
neapolitanus (8), Stylochus pilidium (9).
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FIGURE 2. Notoplanella inarmata (Bock, 1931). A Habitus; B eyes; C sagittal reconstruction of the whole animal (anterior to
the right); D sagittal reconstruction of the male and female genital systems (anterior to the right). Abbreviations: b, brain; ce,
cerebral eyes; cg, cement glands; ed, ejaculatory duct; ev, external vagina; fp, female pore; i, intestine; m, mouth; o, ovary; ovd;
ph, pharynx; pp, penis papilla; pv, prostatic vesicle; sv, seminal vesicle; te, tentacular eyes; vd, vas deferens. Scale bars: A
5mm, B 500µm, C, D, 200µm.
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FIGURE 3. Histological sections of Notoplanella inarmata (Bock, 1931). A eyes; B male copulatory complex; C penis
papilla; D external female reproductive system. Abbreviations: ce, cerebral eyes; ed, ejaculatory duct; fp, female pore; pp,
penis papilla; pv, prostatic vesicle; sv, seminal vesicle; te, tentacular eyes. Scale bars: A 500µm, B, C, D 200µm.
Description. Fixed specimen is 7 mm long by 2 mm wide. Body elongated, anteriorly truncated, lateral
margins almost parallel, posteriorly slightly rounded. Ground colour pail, with numerous smaller and larger dark
spots on the dorsal surface, except along above the pharynx and the genital region. Sometimes the smaller spots
arranged in small interconnected groups. Marginal band free of spots (Fig. 4A). Small nuchal tentacles present.
Tentacular eyes primarily at the bases and some inside the tentacles (Figs. 4B, 5A). The cerebral and pre-cerebral
eyes form a single and elongated undifferentiated group; marginal or frontal eyes lacking. Tentacular eyes larger
than cerebral ones. Bilobated brain with two symmetrical lobes (Fig. 4B). The pharynx occupies the middle third of
the body, mouth opening at the medial region (Fig. 4C).
Testes and ovaries extend on both sides of the body; testes ventral and ovaries dorsal. Gonopores separated.
Male copulatory apparatus, directed backwards, begins almost immediately behind the pharyngeal cavity. Deferent
ducts become wider before entering ventrally, describing an arc, into the seminal vesicle (Fig. 4D). Seminal vesicle
with thick muscular walls. Elliptic prostatic vesicle (65 µm in length and 40µm in width) interpolated, with a
strong muscular envelope and inner epithelium folded, with eosinophilic secretion. Seminal and prostatic vesicle
connected by a short narrow duct that widens at the end. Ejaculatory duct straight, with undifferentiated inner
epithelium. Large and unarmed penis papilla, conical-shaped, housed in a non-ciliated atrium (Fig. 5B).
Female system with vestigial Lang’s vesicle. Oviducts lead together into an unpaired organ, anterior to the
poorly developed Lang’s vesicle. The narrow proximal tract of the vagina runs forwards, turns backwards, then
becomes wider and receives secretions from well developed cement glands. The external vagina is short and
narrow, and runs straight down to the gonopore (Figs. 4D, 5C).
Discussion. The genus Notoplanella has the only species Notoplanella inarmata from South Africa Bock,
1931. With the discovering and description of N. estelae, the genus has currently increased to two species. The
specimen captured in Mar Menor clearly belongs to the genus Notoplanella. It exhibits characteristics of the genus,
such as an oval-shaped body, paired cerebral and tentacular eye clusters, a central pharynx, a true seminal vesicle
connected by a narrow duct to a large elliptic and interpolated prostatic vesicle with strong muscle layers, an
unarmed penis papilla, a weak muscular vagina and a common oviduct (Bock 1931).
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FIGURE 4. Notoplanella estelae sp. nov. A Habitus; B dorsal view of the anterior region; C sagittal reconstruction of the
whole animal (anterior to the left); D sagittal reconstruction of male and female genital systems (anterior to the left).
Abbreviations: b, brain; ce, cerebral eyes; cg, cement glands; com. ov, common oviduct; ed, ejaculatory duct; ev, external
vagina; fp, female pore; i, intestine; Lv, Lang’s vesicle; m, mouth; mp, male pore; o, ovary; ov, oviduct; ph, pharynx; pp, penis
papilla; pv, prostatic vesicle; sv, seminal vesicle; t, tentacle; te, tentacular eyes; ts, testes; vd, vas deferens. Scale bars: A 2mm,
B 500µm, C 1mm, D 200µm.
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FIGURE 5. Histological sections of Notoplanella estelae sp. nov. A Tentacle region and eyes (anterior to the left); B male
copulatory complex (anterior to the right); C female reproductive system (anterior to the right). Abbreviations: cg, cement
glands; com. ov, common oviduct; ev, external vagina; fp, female pore; mp, male pore; pp, penis papilla; pv, prostatic vesicle; t,
tentacle; te, tentacular eyes; sv, seminal vesicle. Scale bars: A 100µm, B, C 200µm.
Notoplanella estelae sp. nov., in contrast to N. inarmata, possesses nuchal tentacles, located slightly behind
the brain. The brain is bilobated in both species; however, in N. inarmata, the anterior end of the lobes is pointed
and larger than the posterior end (Bock 1931), while in N. estelae, the lobes are rounded in both extremes and the
posterior end is larger than the anterior. Both species of the genus also have centrally-located pharynges, although
in N. inarmata, the oral pore opens at the posterior end of the pharynx, while in N. estelae, it opens at the centre.
The main differences in the reproductive system largely correspond to the male complex. The characteristic
duct between the seminal and prostatic vesicles is much shorter in N. estelae and enlarges before entering the
prostatic vesicle. In addition, the prostatic vesicle is smaller and the penis papilla is much larger in N. estelae than
in N. inarmata. The only difference in the female system between these two species is the presence of a vestigial
Lang’s vesicle in N. estelae.
In the description of N. inarmata, Bock (1931) asserts that the opening of the oviducts suggests its ancestor
had a Lang's vesicle and, furthermore, that the structure of the proximal portion of the vagina can only be explained
owing do this character. Thus, the presence of a vestigial Lang’s vesicle in N. estelae is compatible with belonging
to the genus Notoplanella.
The presence of nuchal tentacles and a vestigial Lang’s vesicle in N. estelae requires the addition of those
characters to the genus’ diagnosis. Therefore, the genus diagnosis is now as follows:
Diagnosis (Bock 1931) emended: Cryptocelidae with oblong-oval body shape, with or without tentacles.
Paired cerebral and tentacular eye clusters present. Pharynx central. True seminal vesicle connected to the prostatic
vesicle by a narrow duct. Interpolated large prostatic vesicle, elliptic, with numerous secretory ducts. Unarmed
penis papilla. Weak muscular vagina, with or without a vestigial Lang’s vesicle, with the common oviduct clearly
differentiated.
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Family LEPTOPLANIDAE Stimpson, 1857
Genus Leptoplana Ehrenberg, 1831
Leptoplana mediterranea (Bock, 1913)
Synonymous: Leptoplana tremellaris forma mediterranea Bock, 1913
Material examined. Six mature specimens, collected in Isla del Ciervo, Lo Pagán and Los Urrutias (Mar Menor,
Murcia). From clays and Caulerpa prolifera (Chlorophyta) found two metres deep; Fig. 1 (4).
Morphological remarks. As described in Gammoudi et al. (2012), the position and structure of the proximal
chamber of the prostatic vesicle, and its ventral attachment to the seminal vesicle, are similar in all six specimens
and confirms that our exemplars belong to L. mediterranea, supporting the hypothesis that L. mediterranea is the
only representative of the genus in the Mediterranean Sea (Gammoudi et al. 2012).
Distribution. Well documented in the Mediterranean Sea (although also reported as Leptoplana tremellaris)
by Grube 1840 (Palermo); Lang 1884 (Naples); Lo Bianco 1888, 1899 (Naples); Pruvot 1897 (Gulf of Lyon);
Micoletzky 1910 (Trieste); Palombi 1928 (Port Said), 1936 (Naples); Steinböck 1933 (Adriatic Sea); Arndt 1943
(Naples); Galleni & Gremigni 1989 (Italian coasts); Novell 2003 (Catalonia); Gammoudi et al. 2012 (Tunisia); and
here for Mar Menor (Murcia, Spain).
Superfamily STYLOCHOIDEA Poche, 1926
Family CALLIOPLANIDAE Hyman, 1953
Genus Trigonoporus Lang, 1884
Trigonoporus cephalophtalmus Lang, 1884
Figs. 1 (3), 6, 7
Material examined. Three mature specimens, collected in the Columbretes and Hormigas Islands and Alborán
Island from rocky substrate found at 14.3, 23.5 and 36 metres deep, respectively for each location; Fig. 1 (3).
Description. Fixed specimen is approximately 2 cm long by 5 mm wide. Very elongated body. Colour whitish-
yellow, partially lost during conservation, with numerous and small brown spots (Fig. 6A). Region between the
brain and the anterior margin strewn with numerous small eyes spreading out in a fan-like manner (Fig. 6B).
Marginal eyes arranged along the frontal margin of the body. Tentacles and tentacular eyes lacking. Brain located
about 2 mm from the anterior margin (Figs. 6C, 7C). Ruffled pharynx situated in the middle third of the body with
the oral pore opening in the centre of it. Ovaries dorsal. Separated gonopores (Fig. 6C).
Male copulatory complex directed backwards, near the pharyngeal cavity (Fig. 6D). Vasa deferentia occupy
the middle third of the body due to being dilated, and open laterally into a tubular seminal vesicle thickened in the
junctions region (Figs. 6D, 7D).The ejaculatory duct runs ventrally from the seminal vesicle to the proximal end of
the prostatic vesicle. The prostatic vesicle has a strong muscular envelope and is lined with a smooth and folded
glandular epithelium (Fig. 7B). The penis papilla, small and unarmed, is conical-shaped, with a strong muscular
envelope, housed in a wide, ciliated atrium.
The epidermis around the female pore appears corrugated, forming an adhesive pad (Figs. 6D, 7A). The female
system consists of an external and internal vagina. The short narrow external vagina runs from the gonopore
upwardsto the internal vagina. The internal vagina ascends from the proximal region of the external vagina, curves
downwards and backwards and, after receiving the oviducts, continues to the ductus vaginalis. Oviducts lead
separately into the middle of the internal vagina. Proximal tract of the internal vagina runs forwards, receiving
secretions from the well developed cement glands. Lang’s vesicle lacking. The ductus vaginalis opens to the
exterior behind the female pore.
Distribution. Trigonoporus cephalophtalmus has only been found once in the Gulf of Naples, Italy (Lang
1884). This is the first record for this species both outside of the Gulf of Naples and for the Iberian Peninsula.
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FIGURE 6. Trigonoporus cephalophtalmus (Lang, 1884). A Habitus; B, C eyes; D sagittal reconstruction of the whole animal
(anterior to the left); E sagittal reconstruction of the male and female genital systems (anterior to the left). Abbreviations: b,
brain; cg, cement glands; dv, ductus vaginalis; e, eyes; ed, ejaculatory duct; ev, external vagina; fp, female pore; i, intestine; m,
mouth; mp, male pore; o, ovary; ov, oviduct; ph, pharynx; pp, penis papilla; pv, prostatic vesicle; sv, seminal vesicle; vd, vas
deferens. Scale bars: A 1cm, B 2mm, C 5mm, D 5mm, E 500µm.
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FIGURE 7. Histological sections of Trigonoporus cephalophtalmus (Lang, 1884). A eyes; B vas deferens and seminal vesicle;
C prostatic vesicle and penis papilla; D female reproductive system. Anterior to the left in all figures. Abbreviations: b, brain;
cg, cement glands, d, ductus vaginalis; e, eyes; ed, ejaculatory duct; ev, external vagina; fp, female pore; mp, male pore; pp,
penis papilla; pv; prostatic vesicle; sv, seminal vesicle; vd, vas deferens. Scale bars: A 1mm, B, C, D 500µm.
Family PLANOCERIDAE Lang, 1884
Genus Planocera Blainville, 1828
Planocera graffi Lang, 1879
Figs. 1 (5), 9, 10
Type locality. Gulf of Naples, associated with other invertebrates such as Balanus, Halichondria, Penares and
Lithodomus (Lang 1879, 1884, Tyler et al. 2012).
Type material. not available.
Material examined. One mature specimen from Cabo de Palos (Murcia, Spain) and two mature specimens
from littoral areas near Calpe (Alicante, Spain) were studied. One mature specimen from Calpe was sectioned
sagittally and mounted on 50 slides (MNCN 4.01/130 - MNCN 4.01/180). The specimen from Cabo de Palos and
the second specimen from Calpe were stored in alcohol 70%.
Localities: Cala Racó, Calpe, Alicante (38º38.07’N, 0º04.46’E) Spain; Cabo Palos, Murcia, Spain
(37º37.39’N, 0º42.25’W); Fig. 1 (5).
Other material. Planocera pellucida (Mertens, 1833) Oersted, 1844 Zoologisches Institut und Zoologisches
Museum der Universität Hamburg, slides: V 13167/1-V13167/18 (Atlantic Ocean, pelagic); V 131171/1-V13171/
15 (Atlantic Ocean, pelagic); V 13169/1-V13169/37 (Atlantic Ocean); V 13177/1-V13177/11 (Atlantic Ocean) and
5 specimens in alcohol: V13131 (Cape Verde Islands).
Description. The specimen (Fig. 9A–D) has a broadly oval, almost round, form with slightly ruffled margins,
20 mm long by 15 mm wide (measurements from fixed specimen). The ground colour is yellow-orange, with a
reddish net-like accumulation of pigment granules at the body midline along the intestine branches. The terminal
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ramifications on the dorsal side and the margin of the body sometimes reflect a white colour. The body appearance
is fleshy, but very transparent and frail in appearance. Two conspicuous conical tentacles located near the brain, but
far from the margins. Numerous tentacular eyes at the base of each tentacle. Several small cerebral eyes present
anterior as well as posterior to the tentacles, being more abundant behind the tentacles. A broad ruffled pharynx
occupies the central region of the body (Fig. 9E).
In general, the organisation of the copulatory complex (Fig. 9F) agrees with the detailed descriptions of Lang
(1884). Nevertheless, some additional details can be discerned in our specimens. For example, the vasa deferentia
dilate and become the spermiducal bulbs before entering proximally into the muscular cirrus bulb. The prostatic
vesicle opens together with the spermiducal bulbs at the distal end of the male bulb. The prostatic vesicle is lined
with a glandular epithelium forming the characteristic tubular chambers. The ejaculatory duct is wide and short.
The cirrus is composed of distal spines and teeth that progressively increase in size towards the genital atrium. The
rather short male genital atrium is bottle-shaped. The entire male complex is surrounded by thick muscle layers.
The female apparatus does not show remarkable differences from Lang's (1884) description of the species. Briefly,
it consist of a muscular external vagina or vagina bulbosa, surrounded by muscle layers, which is lined with a
delicate cuboidal, glandular epithelium at the distal end; in some sections, this epithelium shows fringe-like
extensions. The internal vagina first runs anteriorly and then posteriorly. Numerous cement glands open in the
distal section of the internal vagina. Proximally, the two oviducts join the internal vagina and Lang’s vesicle is
either entirely lacking or only present as a vestigial vesicle.
Discussion. The genus Planocera Blainville, 1828 shows a wide, almost cosmopolitan, distribution (Fig. 8).
From the Mediterranean basin, three species have been reported: Planocera folia Grube, 1840, Planocera graffi
Lang, 1879 and Planocera ceratommata (Palombi, 1936).
Planocera graffi was first described for the Gulf of Naples (Lang 1879, 1884), and also reported for the islands of
Sao Vicente (Cape Verde) (Laidlaw 1903) and the Catalan coast (Novell 2003).
Planocera folia was originally described for Palermo by Grube (1840), and later cited for Barwick Bay, USA
(Apalachee Bay?) by Johnston (1865). Unfortunately, the internal anatomy of P. folia is unknown, thus making it
impossible to compare with other species of the genus. Ludwig von Graff (1904) last cited P. folia, merely as the
record of Grube (1840); therefore, the last real record of P. folia appears to be in 1865 by George Johnston. For the
Mediterranean, the only record is the original description of Grube (1840).
Planocera ceratommata was originally described by Palombi (1936) for Cape Town (South Africa), but more
recently has been cited by Novell (2003) for the Catalan coast.
Although Lang (1879, 1884) could not compare Planocera graffi with P. pellucida (Mertens, 1833) as the
description of P. pellucida does not include internal anatomical features, he did comment on the great similarity
between P. g r a f f i and P. pelagica (Moseley, 1877), which only differ in the shape of the ejaculatory duct (tortuous
in P. pelagica). Years later, Faubel (1983) synonymised P. pelagica with P. pellucida (Mertens, 1833).
Bock (1913) and Faubel (1983) described P. pellucida as oval, tapering posteriorly and P. graffi as rounded,
sometimes broader than long. However, Prudhoe (1985) reported that P. pellucida could show both body shapes,
slightly elongated or rounded. This variation in body shape is, in our opinion and after a careful reading of the
original description, the only reported difference between both species. An anatomical comparison between both
species was necessary. Therefore, specimens of P. pellucida from the invertebrate collection if the Zoological
Museum of Hamburg, captured in the Atlantic shores, were compared with our specimens from the Mediterranean
coasts. The results of this comparative study (Fig. 10) are the following: the cirrus of the male copulatory organ
shows the same shape and type of spines in all specimens, the disposition and localisation of the prostatic and
seminal vesicle is the same and the vasa deferentia show identical trajectories. It is evident that there are no
significant morphological differences between the two species and a synonymization is justified. Therefore, we
propose that P. graffi is synonymous with P. pellucida with the consequent expansion of the distribution of P.
pellucida within the Mediterranean Sea.
With respect to the third Planocera species cited for the Mediterranean shores, P. ceratommata (Palombi,
1936), this species is actually the most cited species of the genus Planocera within the Mediterranean Sea,
although it was originally described for Still Bay, Cape Town (South Africa) (Palombi 1936).
Unfortunately, the original material of P. ceratommata is missing, but numerous similarities between this
species and P. pellucida suggest a possible case of synonymy; although, some differences must also be considered,
that not allow a synomization. The most significant variation between P. ceratomata from South Africa and our
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material lies in the arrangement of the eyes. In P. pellucida, the tentacular eyes surround the tentacles in an orderly
(stereotypical) manner, whereas in P. ceratommata the arrangement of the eyes is irregular (Palombi, 1936; fig.
17). A similar pattern is also observed for the cerebral eyes. Another difference concerns the organisation of the
prostatic vesicle. According to Palombi (1936), the copulatory organ “É formato de una grossa vescicola
glandulare granulosa avvolta di una rica fascci muscolare costituita di fibri longitudinale e circolari” (“It is formed
by a large glandular prostatic vesicle involved by well developed bundles of muscles formed by longitudinal and
circular fibers"); this description, together with the figure (Palombi 1936, fig. 18), illustrate a prostatic vesicle that
is different from the vesicle in P. pellucida described by Bock (1913). Nevertheless, we assume that many of the
records of P. ceratommata for the Mediterranean in fact concern P. pellucida.
FIGURE 8. Map of known localities of Planocera pellucida (black dots), Planocera ceratommata (white squares) and
Planocera graffi (red dots).
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FIGURE 9. Planocera graffi (Lang, 1879). A Dorsal and B ventral views of fixed specimen; C dorsal view of a cleared
animal; D dorsal view of a live animal; E sagittal reconstruction of the whole animal (anterior to the left); F sagittal
reconstruction of male and female genital systems (anterior to the left). Abbreviations: e, eyes; ed, ejaculatory duct; fp, female
pore; m, mouth; mp, male pore; o, ovary; ph, pharynx; pv, prostatic vesicle; spb, spermiducal bulb; t, tentacle; ts, testes; tee,
teeth; v, vagina; vb, vagina bulbosa; vd, vas deferens. Scale bars: A, B, C, D 7mm, E 500µm, F 500µm.
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FIGURE 10. Planocera pellucida (Mertens, 1833) of the Atlantic coast. A–B specimen V13167/1-V13167/18 (Iron-
hematoxylin-eosin stain), A male copulatory organ, B detail of cirrus and teeth; C–D specimen V13171/1-V13171/15 (Pasini
staining), C male copulatory organ, D detail of cirrus; E–F specimen V13169/1-V13169/37 (Pasini staining), E male
copulatory organ, F detail of cirrus; G–H specimen of the Mediterranean coast (Azan staining), G male copulatory organ, H
detail of cirrus. Anterior to the left in all figures. Scale bars: A, C, E, G 500µm, B, D 200µm, F, H 100µm.
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Family STYLOCHIDAE, Stimpson, 1857
Genus Imogine Girard, 1853
Imogine mediterranea Galleni, 1976
Synonymous: Stylochus mediterraneus Galleni, 1976.
Material examined. One mature specimen, collected in Los Urrutias (Mar Menor, Murcia). From rocky substrate
found between 0.2 to 0.5 metres deep; Fig. 1 (6).
Morphological remarks. The specimen shows very few frontal eyes. The marginal eyes are present only in
the anterior half of the body and not in the whole body margin as originally described for Imogine mediterranea
(Galleni, 1976). However, the internal anatomy of the reproductive organs of I. mediterranea coincides with the
original description and figure of Galleni (1976). This difference in the distribution of marginal eyes may be related
to the size of the specimen: mature worms are approximately 3 cm long, and this specimen, though mature, is only
12 mm long.
Distribution. Imogine mediterranea has been found in several areas of the northern Mediterranean coast
(Italy: Livorno, La Spezia, Pisa (Galleni 1974) and Liguria (Wenzel et al. 1992); Croatia: Istria (Bytinski-Salz
1935)) and now in the western Mediterranean coast in Mar Menor.
Imogine stellae sp. nov.
Figs. 1 (7), 11, 12; Table 2
Type locality. Mar Menor (Murcia, Spain) (37º46.16’N, 0º45.02’W); Fig. 1 (7).
Type material. Holotype one mature specimen sectioned sagittally. MNCN 4.01/181 - MNCN 4.01/199 (18
slides).
Material examined. 14 live specimens from the eastern seashore of Mar Menor (Murcia, Spain) were studied;
of these, four mature specimens were sectioned sagittally and mounted on slides. The material is deposited in the
invertebrate collection of Museo Nacional de Ciencias Naturales de Madrid (Spain).
Etymology. The specific epithet is dedicated to Estrella Fernandez-Despiau, who collected the species.
Diagnosis. Imogine with elongated body, without marked undulations; pigmentation brownish with dark
brown spots, less dense at the margins and midline; nuchal tentacles present; tentacular, marginal and cerebral eyes
present; anchor-shaped seminal vesicle opens at the base of the prostatic vesicle; prostatic vesicle “djiboutiensis”
type; male and female atrium not ciliated; male and female gonopore close together, but clearly separated.
Description. Body elongated with rounded anterior and posterior ends, 12 mm long and 5.5 mm wide, tapering
slightly posteriorly. Body margins without marked undulations. Nuchal tentacles located in the anterior one-fifth of
the animal. Dorsal pigmentation brownish with dark brown spots, turning pale and less dense towards the margins
and midline (Fig. 11A). Tentacular, marginal and cerebral eyes present. Tentacular eyes denser at the inner margins
of the nuchal tentacles (Fig. 12A). Cerebral eyes form two elongated clusters. Marginal eyes small, arranged
around the anterior end of the body margin. Ventral surface light yellow. Pharynx located in the anterior half of the
body. Oral pore located at one-third of the body length. Main digestive trunk extends forwards and backwards of
the pharyngeal cavity (Fig. 11B).
Reproductive system (Figs. 11C, 12B): The male system is located in the posterior part of the animal and
consists of well developed spermiducal bulbs, a true anchor-shaped seminal vesicle, a musculo-glandular ovoid
prostatic vesicle, a penis papilla, crossed by a straight ejaculatory duct and an atrium. The conspicuous spermiducal
bulbs are located behind the anchor-shaped seminal vesicle. The vasa deferentia ducts are wide, becoming even
wider towards the seminal vesicle, finally entering laterally into the vesicle. The characteristic seminal vesicle
opens through a curved duct directly at the base of the prostatic vesicle. This duct subsequently becomes the
ejaculatory duct. The prostatic vesicle shows, according to Faubel 1983, the characteristic shape of the
“djiboutiensis” type: a small lumen with an external muscle layer and internal glandular lining, and surrounded by
numerous prostatic glands. The conspicuous muscle layer at the distal end of the ejaculatory duct forms the penis
papilla. The male atrium is narrow and not ciliated.
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FIGURE 11. Imogine stellae sp. nov. A Habitus; B sagittal reconstruction of the whole animal anterior to the right); C sagittal
reconstruction of male and female genital systems (anterior to the right). Anterior to the left in all figures. Abbreviations: b,
brain; ce, cerebral eyes; cg, cement glands; ed, ejaculatory duct; fa, female atrium; fp, female pore; i, intestine; m, mouth; ma,
male atrium; me; marginal eyes; mp, male pore; ov; oviduct; ph; pharynx; pv, prostatic vesicle; spb, spermiducal bulbs; t,
tentacle; te; tentacular eyes; sv, seminal vesicle; vd, vas deferens. Scale bars: A, B 6mm, C 200µm.
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FIGURE 12. Histological sections of Imogine stellae sp. nov. A tentacles region and B male copulatory organ (anterior to the
left). Abbreviations: ce, cerebral eyes; ed, ejaculatory duct; fp, female pore; mp, male pore; pp, penis papilla; pv, prostatic
vesicle; spb, spermiducal bulb; t, tentacle; te, tentacular eyes. Scale bars: A 100µm, B 200µm.
The female system is located close to the male copulatory organ. Female and male gonopores are in close
proximity, but clearly separated. The paired oviducts enter separately at the proximal end of the internal vagina. In
preserved specimens, the vagina runs from the dorso-lateral side of the body to the medial axis, then bends
anteriorly and runs ventrally towards the female pore; this last portion is known as the external vagina. The female
atrium is narrow, conical and not ciliated. Numerous cement glands are located along the entire female system, but
are open mainly in the external vagina. Lang's vesicle is absent.
Discussion. Due to the presence of an anchor-shaped seminal vesicle and a strong muscular penis papilla,
Imogine stellae sp. nov. belongs to the genus Imogine. However, with a comparative study of highly characteristic
features of the 34 known Imogine species (Jennings & Newman 1996; Bulnes 2010; and Table 2 of this study), we
can distinguish three major groups based on four main features; viz. the location of the male and female gonopores,
the junction of the sperm duct with the prostatic duct, the shape and size of the penis papilla, and the distal shape of
the female external vagina.
The first group (Table 2) contains species characterised by the presence of two separate, yet physically close,
gonopores: Imogine stellae sp. nov.; I. hamanensis (Kato, 1944); I. hyalina (Bock, 1913); I. ceylanica (Laidlaw,
1904); I. izuensis (Kato, 1944); I. meganae Jennings & Newman, 1996; I. sixteni (Bock, 1931); I. megalops
(Schmarda, 1859); I. minima (Palombi, 1940); I. nebulosa (Girard, 1853); I. rutilis (Yeri & Kaburaki, 1918) (Table
2). However, I. stellae sp. nov. can be differentiated from the other species of the group by its proximal junction of
the prostatic and sperm ducts, a character also shared with I. minima; the other species of this group show either
medial or distal junctions. Other differences are found in the male and female systems. The female gonopore and
distal region of the external vagina of I. stellae sp. nov. present a remarkable dilatation, while the penis papilla
appears longer than in other species. These characters distinguish I. stellae sp. nov. from I. minima, in which the
distal external vagina lacks dilatations and the penis papilla is very short in comparison. Nevertheless, these
characters must be carefully treated as their size may be influenced by the state of relaxation or contraction of the
animal during fixation (Meixner 1907).
The second group comprises Imogine miyadii Kato, 1944; I. necopinata Sluys, 2005; I. tripartitus (Hyman,
1953); I. uniporus (Kato, 1944); and I. catus (Bois-Reymond Marcus, 1958). This group is characterised by a
common gonopore and an external vagina without dilatations. Differences between species concern the location of
the fusion of the prostatic and sperm duct and the shape of the penis papilla.
The third group contains the largest number of species (Table 2) and is mainly characterised by the marked
separation of the female and male gonopores. Species of this group show different types of prostatic and sperm
ducts junctions, as well as varying sizes and shapes of penis papillae and external vaginas. Species of this group
include Imogine aomori (Kato, 1937); I. arenosa Willey, 1897; I. exigua (Hyman, 1953); I. ijima (Yeri & Kaburaki,
1918); I. kimae Jennings & Newman, 1996; I. lateotentare Lee, Beal & Johnston, 2005; I. lesteri Jennings &
Newman, 1996; I. marmorea (Bock, 1925); I. mcgrathi Jennings & Newman, 1996; I. mediterranea (Galleni,
1976); I. melihertani Bulnes, 2010; I. oculifera Girard, 1853; I. orientalis (Bock, 1913); I. pardalotus (Jennings &
Newman, 1996); I. pulcher (Hyman, 1940); I. referta (Bois-Reymond Marcus, 1965); I. speciosa (Kato, 1937); I.
tica (Marcus, 1952); and I. zebra (Verrill, 1882). Species of this group can be differentiated by the pattern of
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pigmentation, size of the tentacles, disposition of the tentacular, cerebral and marginal eyes and distribution of the
cement glands around the female canal (Jennings & Newman 1996, Bulnes 2010).
In relation to the Mediterranean basin, aim of our research, only two other Imogine species have been
previously described from the Mediterranean basin: I. mediterranea (Galleni, 1976) and I. melihertani Bulnes,
2010 (both members of the third group). Imogine mediterranea (Galleni, 1976) is known from the Italian and
Tunisian coasts (Galleni 1976, Gammoudi et al. 2009), while I. melihertani has been reported from the western
coast of the Aegean Sea (Bulnes 2010). Imogine stellae sp. nov. differs from I. mediterranea in the location of the
two gonopores, which are clearly separated in I. mediterranea and close together in I. stellae sp. nov. Another
conspicuous difference in I. stellae sp. nov. is the opening of the seminal vesicle at the caudal base of the prostatic
vesicle, whereas in I. mediterranea and I. melihertani, the ejaculatory duct receives the prostatic duct at a medial
region. Furthermore, the vasa deferentia and spermiducal bulbs are more prominent and well developed in I. stellae
sp. nov. compared to I. mediterranea, although this may be due to differences in developmental states.
The shape of the female system also shows clear differences between these three Mediterranean species. In
I.stellae sp. nov., the female pore is wide, while the atrium is pyramid-like and lacks cilia, whereas in I.
mediterranea and I. melihertani, the female pore is small, and the atrium is ciliated in I. melihertani. The location
of the cement glands along the internal and external vagina is similar in I. stellae sp. nov. and I. mediterranea, but
differs in I. melihertani, in which the cement glands extend along the entire female canal.
Genus Stylochus Ehrenberg, 1831
Stylochus neapolitanus (Delle Chiaje, 1841–1844) Lang, 1884
Synonymous: Planaria neapolitana Delle Chiaje, 1941.
Material examined. Two mature specimens, collected in Los Urrutias (Mar Menor, Murcia). From rocky substrate
and Caulerpa prolifera found between 0.2 to 2 metres deep; Fig. 1 (8).
Morphological remarks. Male copulatory system with simple seminal vesicle; the ejaculatory duct runs
straight to the base of the prostatic vesicle, where it joins the prostatic duct and forms the penis papilla. Gonopores
separated. Simple female system without Lang’s vesicle. The specimens agree with the description and figure of
Lang’s Stylochus neapolitanus (1884), except for one difference: S. neapolitanus only has marginal eyes in the
anterior edge, but one of these specimens have them around the entire body edge. Such phenotypic variation in the
distribution of the eye spots have been reported by Meixner (1907).
Distribution. Western Mediterranean Sea: Delle Chiaje 1841 (Sicily); Lang 1884 (Naples); Novell 2003 (Cap
de Creus). Laidlaw (1906) cited it for the Cape Verde Islands, but Palombi (1939) later assigned that specimen to
Stylochus castaneus.
Stylochus pilidium (Goette, 1881)
Figs. 1 (9), 13
Synonyms: Planaria neapolitana Delle Chiaje, 1841 in Goette, 1878; Stylochopsis pilidium Goette, 1881.
Material examined. One mature specimen, collected in Los Urrutias (Mar Menor, Murcia). From Caulerpa
prolifera found two metres deep; Fig. 1 (9).
Description. Fixed specimen about 10 mm long and 7 mm wide. Colour lost during conservation. Well
developed nuchal tentacles, with numerous internal eyes. Numerous cerebral eyes behind the tentacles, arranged in
two longitudinal clusters. Large marginal eyes arranged around the first third of the body edge. Few frontal eyes.
The muscular pharynx is located in the middle third of the body. Mouth opening in the centre (Fig. 13A).
Gonopores separated and located in the last third of the body. Testes ventral. Male copulatory apparatus with
simple seminal vesicle, which has weak muscular walls. Spermiducal bulbs developed. Prostatic vesicle elongated
(225 µm in length and 75 µm in width) and well developed, dorsal to the seminal vesicle, with thick muscular
envelope. The prostatic duct joins the ejaculatory duct at the base of the prostatic vesicle (Figs. 13B, 13E). The
ejaculatory duct runs straight to the tip of a short conical penis papilla housed in a ciliated atrium.
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FIGURE 13. Stylochus pilidium (Goette, 1881). A Sagittal reconstruction of the whole animal anterior to the left); B–D
histological sections, B male copulatory complex, C, D female reproductive system; E sagittal reconstruction of male and
female genital systems (anterior to the left). Abbreviations: b, brain; ce, cerebral eyes; cg, cement glands; div, diverticulum; ed,
ejaculatory duct; fe, frontal eyes; fp, female pore; i, intestine; m, mouth; me, marginal eyes; mp, male pore; o, ovary; ov,
oviduct; ph, pharynx, pp, penis papilla; pv, prostatic vesicle; sv, seminal vesicle; t, tentacle; ts, testes; te, tentacular eyes;v,
vagina; vd, vas deferens. Scale bars: A 1.5mm, B, C, D, E 200µm.
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Ovaries dorsal. Female system lacks Lang’s vesicle (Figs. 13C, 13E). The oviducts enter separately. Proximal
tract of female duct, the vagina interna or internal vagina, extending forwards, first anterior-dorsally and then
anterior-ventrally. The last tract, which is known as external vagina or vagina externa, runs straight down, with
strong muscular walls, wider than the proximal tract. Narrow, forward-oriented diverticulum at the top of the
external vagina (Fig. 13D), not described for any species of the genus Stylochus.
Discussion. Given that descriptions of Stylochus pillidium are rare, we aim to provide a detailed description of
this species.
Goette (1881) first designed this species as Planaria neapolitana, but later identified it as Stylochopsis
pilidium. In his original description, Stylochopsis pilidium was only compared to Stylochus neapolitanus. Stylochus
and Stylochopsis are both cited by other authors (Lang 1884, Meixner 1907), however, these identifications were
made based only on external morphology. Novell (2003) was the first to describe its internal anatomy.
Stylochus pilidium is clearly similar to S. neapolitanus as both species share the following characters: the
junction of the ejaculatory and prostatic duct, the shape and size of the penis papilla and the outline of the seminal
vesicle and of the female system. Nonetheless, although in previous descriptions (Lang 1884; Meixner 1907), S.
pilidium and S. neapolitanus are described as quite similar or even equal, some characters are different in both
species: S. pilidium shows separated gonopores, which in S. neapolitanus are common, and the distance from the
female gonopore to the posterior end is greater and the prostatic vesicle is longer in S. pilidium than in S.
neapolitanus.
Distribution. West Mediterranean Sea: Naples (Lang 1884); Sitges, Catalonia (Novell 2003); Mar Menor,
Murcia (this paper).
Conclusions
Based on the presence and distribution of the studied species, four types of distribution patterns are observed on the
Mediterranean shores of the Iberian Peninsula. Generally, species either are endemic to the Mediterranean (group
A) or show a nearly cosmopolitan distribution (group C). Between these opposing groups, we find intermediate
models (group B). The fourth group consists of species thought to have been introduced (group D). One important
factor that influences polyclad distribution is dispersion. Some species have indirect development with a planktonic
larval stage (Götte, Müller and Kato’s larvae; Gammoudi et al. 2011), and frequently use plants, algae meadows
(Plehn 1896, Bock 1913) and vessel hulls for dispersal (Bock 1931).
A) Endemic species. The following species may be considered endemic in the Mediterranean:
Notoplana vitrea (Lang, 1884) Bock, 1913
Notoplana vitrea is considered an endemic species of the Mediterranean Sea, cited from the Gulf of Naples
(Lang 1884), the Gulf of Triest (Micoletzky 1910) and Catalonia (Novell 2003). To date, N. vitrea has never been
cited for eastern coasts of the Mediterranean.
Trigonoporus cephalophtalmus Lang, 1884
This species was first described by Lang (1884). Although other Trigonoporus species have been reported for
localities outside of the Mediterranean (Tyler et al. 2012), T. cephalophtalmus has, to date, never again been cited.
Only one exemplar T. cephalophtalmus was previously collected in the Isle of Gaiola in the Gulf of Naples (Lang
1884). In this study, only one exemplar for each locality in the islands of Columbretes, Hormigas and Alboran (Fig
1 (3)) was also collected, showing that this species is very rare.
Comoplana agilis (Lang, 1884) Faubel, 1983
Originally described as Stylochoplana agilis Lang 1884, this species was reported for the first time for the Gulf
of Naples (Lang 1884) and later for the coast of Catalonia (Novell 2003). In this study, C. agilis was not found at
any of the sampled localities, but based on existing information, we consider C. agilis an endemic species of the
Mediterranean Sea.
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Leptoplana mediterranea (O. F. Müller, 1773) Bock, 1913
Leptoplana mediterranea is a endemic species of the Mediterranean Sea and its distribution extends mainly
throughout the western Mediterranean basin (Gammoudi et al. 2012); to date, it has not been cited for the eastern
Mediterranean coast.
Imogine mediterranea (Galleni, 1976) Jennings & Newman, 1996
The genus Imogine Girard, 1853 is a relatively new genus for the Mediterranean Sea, though known since
nineteenth century for the western Pacific (e.g. Japan, Australia, Thailand) and western Atlantic (e.g. USA, Costa
Rica, Brazil) coasts. Imogine is nearly unknown for the European Atlantic coast, with the exception of I.
necopinata Sluys, 2005 (Sluys et al. 2005) from the North Sea canal in The Netherlands.
In the Mediterranean Sea, Imogine has only been reported twice: I. mediterranea (Galleni, 1976) and I. melihertani
Bulnes, 2010. Within the Iberian Peninsula, I. mediterranea (Galleni, 1976) was found for the first time in the
present study.
The lack of Imogine records in the well known occidental shores of the Mediterranean (Galleni 1976), suggests
that this genus recently extend its distribution within the Mediterranean and possesses a high degree of speciation.
Stylochus neapolitanus (Delle Chiaje, 1841–1844) Lang, 1884
Since 1884, S. neapolitanus has been well known for the occidental coasts of the Mediterranean but, to date,
has not been cited in the eastern Mediterranean coast. Laidlaw (1906) cited S. neapolitanus for the Cape Verde
Islands, but he also considered this record dubious (pg. 707, Laidlaw 1906). Therefore, at present, S. neapolitanus
is considered an endemic species of the Mediterranean.
Stylochus pilidium (Goette, 1881) Lang, 1884
Currently, S. pilidium is only known for the western Mediterranean coast and thus can be considerated
characteristic or endemic for the Mediterranean Sea.
Notoplanella estelae sp. nov. and Imogine stellae sp. nov. are considered endemic for the Mediterranean until
proven otherwise.
B) Species mainly known for Mediterranean waters, but that have also been cited in other regions.
Discocelis tigrina (Blanchard, 1847) Lang, 1884
Discocelis tigrina was first cited for the coast of Sicily (Blanchard 1847), then subsequently for the Gulf of
Naples (Lang 1884) and the coast of Catalonia (Novell 2003). Also recorded for Mauritania by Palombi (1939)
although, this is the only record for D. tigrina outside of the Mediterranean. Discocelis tigrina did not appear in
sampling and/or collection material in this study.
Hoploplana villosa (Lang, 1884) Laidlaw, 1902
Hoploplana villosa was originally described as Planocera villosa by Lang (1884) for the Gulf of Naples,
specifically for Nisida Island. It was also recorded once from Susaki (Izu, Japan) by Kato (1937) and from
Catalonia by Novell (2003).
C) Species that have been cited in several regions and thus have a cosmopolitan distribution.
Pleioplana atomata (O. F. Müller, 1776) Faubel, 1983
Although cited by Novell (2003) for the coast of Catalonia, this species was not found in the southern
Mediterranean shores of the Iberian Peninsula in this study. It was also cited by Palombi (1928) for the Canal of
Suez. This species is considerated cosmopolitan because it is also common along the North Atlantic coasts of
Europe and North America (Tyler et al. 2012).
Planocera pellucida (Mertens, 1833)
With the synonymization of P. graffi Lang, 1884 with P. pellucida (Mertens, 1833), the distribution of this
MARQUINA ET AL.
132 · Zootaxa 3780 (1) © 2014 Magnolia Press
species, which is already known for both the northern and southern coasts of the Atlantic Ocean (Bock 1913,
1931), as well as some locations for Japan, has extended to include the Mediterranean Sea.
D) Species suspected to have been introduced.
This section lists the species thought to have been introduced based on their sporadic appearance and divergent
sampling localities.
Notoplanella inarmata Bock, 1931
Notoplanella inarmata is known for different localities near Cape Town (Bock 1931, Day 1970, Prudhoe
1989), but it has never been captured in the Mediterranean until now. However, localities between Cape Town and
the Iberian Peninsula were not sampled, therefore we cannot be certain it is an introduced species. In South Africa
and Formentera, the specimens were collected by dredging (0–134 metres). This finding, together with
Notoplanella estelae sp. nov., is the first record of Notoplanella for the Mediterranean Sea.
Planocera ceratommata (Palombi, 1936) Faubel, 1983
Palombi (1936) originally described this species from South Africa (Still Bay) as Planocerodes ceratommata;
Novell (2003) also cited this species for the Catalan coasts. As well as P. ceratommata is frequently photographed
in the shores of the Mediterranean (e.g. see http://fotosubmallorca.blogspot.com.es/2010/02/opistobranquio-no-
clasificado.html; http://bitxosdelmediterrani.blogspot.com/2008/10/planoceros-sp.html; http://www.cibsub.com/
bioespecie_es-planocera_ceratommata-36639; http://doris.ffessm.fr/fiche2.asp?fiche_numero=1090). Although
the identification is somewhat dubious, because it is only based on the external anatomy and this genus needs for
the determination at species level the study of the internal anatomy.
Acknowledgements
We thank Ivan Acevedo and Jorge Gutierrez for their help in collecting polyclads. We are grateful to Dr. Angel
Pérez-Ruzafa for generously providing material collected from Mar Menor, without which this study would not
have been possible. We thank Dr. A. Schmidt-Rhaesa and Mrs. H. Roggenbuck for kindly sending the Planocera
pellucida material from the Zoological Museum of Hamburg. This study was supported by I+D Project grants CGL
2010-15786/BOS and CGL2011-29916, which are financed by the Spanish Ministry of Economy, and by the
Spanish Agency for International Cooperation (AECI Project ref.: A/030038/10). We are indebted to Melinda
Modrell for proofreading the English text and the two anonymous reviewers for their careful corrections and
valuable comments made on the manuscript.
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