Deep-sea Fauna of the Sea of Japan, edited by T. Fujita, National Museum of Nature and Science Monographs, No. 44,
pp. 39–54, 2014

A New Species of Deep-sea Solenogastres (Mollusca) from the Sea of Japan
Hiroshi Saito1 and Luitfried von Salvini-Plawen2
1

Department of Zoology, National Museum of Nature and Science,
4–1–1 Amakubo, Tsukuba-shi, Ibaraki, 305–0005 Japan
E-mail: h-saito@kahaku.go.jp
2Integrative Zoologie, Universität Wien, Althanstraße 14, A–1090 Wien, Austria
E-mail: luitfried.salvini-plawen@univie.ac.at

Abstract: A new species of deep-sea Solenogastres-Amphimeniidae, Alexandromenia marisjaponica, is described from the Sea of Japan at 300–600 m depth. This new species attains a size of 16 ×
1.7 cm, exhibits a reddish coloration and shows up to 26 pedal folds. Internally, it is characterized
among others, by the shape of the monoserial radula consisting of teeth provided with a pair of longhorn-like lateral denticles and by the conﬁguration of the spawning ducts. The organisation of the
new species is displayed and compared with known congeneric representatives. This record enlarges
the poorly known biodiversity of Solenogastres in Japanese waters.
Key words:
Japan.

Solenogastres, Amphimeniidae, Alexandromenia, new species, taxonomy, Sea ofIntroduction
The Solenogastres is a small group of shell-less laterally narrowed mollusks, which is characterized by a mantle that produces a chitinous cuticle throughout, as well as unicellularly
formed aragonitic sclerites, and by a midventral groove which houses a pedal fold or folds withcilia for gliding locomotion. The Solenogastres are exclusively marine animals, occurring at thedepth from 1 to 6850 m (Salvini-Plawen and Schwabe, 2012). They are free living animals, predominantly feeding on Cnidaria. At present, 275 nominal species have become known (Gil-Mansilla et al., 2011, 2012; Salvini-Plawen and Schwabe, 2012; Zamarro et al., 2012), which areclassiﬁed into four orders (two subclasses) mainly based on the features of the cuticle and thesclerites (Salvini-Plawen, 1978).
During the course of a deep-sea research project, “Research on Deep-Sea Fauna of the Sea ofJapan, 2009–2013” conducted by the National Museum of Nature and Science (NSMT), ﬁve
specimens of large Solenogastres were collected from the Sea of Japan at the depth from 300 to
600 m, that is the transitional zone extending between the margin of continental shelf and theupper bathyal zone, thus already belonging to the deep-sea. Examination of those specimens
together with two additional specimens deposited in the NSMT, which were collected from thesame zone of the Sea of Japan, revealed that those specimens are conspeciﬁc, and belong to thegenus Alexandromenia of the family Amphimeniidae. To date, ten species of Alexandromenia are
known: four species from the Antarctic, four species from the North Atlantic, two species fromthe East Paciﬁc. Taxonomic comparisons between the present species and those ten congeners
revealed sufﬁcient differences, which warrant the present species to be new to science.

Hiroshi Saito and Luitfried von Salvini-Plawen

40

Materials and Methods
The localities of the seven examined specimens are shown in Fig. 1. Among them, the holotype and another specimen were incidentally collected together by a ﬁshing trawl, which was
operated off Shin-minato, Toyoma Bay, at the depth of ca. 300 m; the remaining ﬁve specimens
were collected during the research project “Research on Deep-Sea Fauna of the Sea of Japan”.
All specimens were ﬁxed in 10% neutral formalin, and preserved in 70–80% ethanol.
Among seven specimens examined in total, three specimens were investigated histologically,four specimens were dissected to observe general morphology of the internal organization.
For examination of mantle sclerites, pieces of mantle cuticle were dissected, macerated indiluted household bleach (hypochloride), and rinsed, and sclerites were then removed from the
cuticle in a drop of 80% ethanol on slide glass using needles. Those removed sclerites were air
dried and permanently mounted in ENTELLAN® neu (Merck & Co. Inc.). Identiﬁcation, measurement, and drawing of sclerites were made by using a light microscope equipped with an ocular micrometer and a camera lucida.
For observation of the radula, the radula area of the foregut was isolated by dissection andmacerated in diluted household bleach. The dislodged radula was transferred into distilled waterby a pipet for washing, then to ethanol series and DMP (2,2-dimethoxy propane) for dehydrationin small dimples on a slide glass. Subsequently, the radula was transferred into a drop of xylene
on a slide glass and mounted in the same medium with the sclerites.
For histological study, both terminal portions of specimens were decalciﬁed in Bouinʼs solution. Then, these portions were rinsed with 70% ethanol with drops of ammonium solution, dehydrated with DMP, embedded in parafﬁn, serially cross sectioned in 10 μm thickness by a microtome, and stained with Mayerʼs hematoxyline and eosin B.

Fig. 1.

Localities of specimens. Asterisk indicates the type locality.

A New Species of Deep-sea Solenogastres from the Sea of Japan

41

Reconstruction of the body organization was made manually by the conservative method,plotting on millimeter-scaled paper.
All specimens are deposited in the molluscan collection in the Department of Zoology,
National Museum of Nature and Science, at Tsukuba.
Description is made based on the holotype specimen. When additional information from theparatypes was given, it was indicated in parenthesis with the registration number of the source
specimen.
Abbreviations: a, anus; ac, anterior caecum of midgut; at, atrium; au, heart auricle; bg, buccal
ganglion; bw, “spongy” body wall; c, cone of out-leading duct of latero-ventral foregut glandularorgan; cg, cerebral ganglion; d, ductule of latero-ventral foregut glandular organ; dp, diverticulaof pallial cavity; dts, dorsoterminal sense organ; e, esophagus; eg, esophageal glands; fg, packages of latero-ventral foregut glandular organ; fgd, out-leading duct of latero-ventral foregut
glandular organ; fn, frontal nerve; g, gonad; gp, gonopericardioduct; gpi, ganglia posteriora inferiora; gps, ganglia posteriora superiora; h, heart; hg, hindgut; lg, (1st) lateral ganglion; m, mouth;ma, mantle; mg, midgut; oe, opening of esophagus; ofg, opening of out-leading duct of lateroventral foregut glandular organ; og, glands of the spawning duct outlet; op, beginning (proximal
opening) of pericardioduct; osd, opening of spawning duct; p, pericardium; pc, pallial cavity; pd,
pericardioduct; pf, pedal fold; pg, pedal glandular organ; phg, pharyngeal glands; ph, pharynx;
pp, pedal pit; r, radula; rf, respiratory folds; sc, suprarectal commissure; sd, spawning duct; sdo,
spawning duct outlet; sdg, spawning duct glands; sp, sensory papillae; spg, suprapallial gland; sr,seminal receptacle; vn, heart ventricle; vg, (1st) ventral ganglion.
Systematic AccountClass Solenogastres Gegenbaur, 1878 (sensu Simroth, 1893)
Order Cavibelonia Salvini-Plawen, 1978
Diagnosis. Mantle cuticle generally thick, mostly with multiple layers of hollow spicules
and long epidermal papillae.
Family Amphimeniidae Salvini-Plawen, 1972
Diagnosis. Solenogastres with thick mantle cuticle, sclerites acicular as hollow spicules(needles). Radula monoserial (or lacking); antero-ventral radula sack (when present) unpaired.
Foregut glandular organs opening pre-radular, typically as ramiﬁed ducts with terminallyarranged packages of gland cells (= type D). Spawning ducts with subepithelially arranged, intercellularly opening glands. Ten genera recognized.
Genus Alexandromenia Heath, 1911
Type species. Alexandromenia agassizi Heath, 1911
Diagnosis. Epidermal papillae present. Sclerites in two main sizes. Mouth within common
atrio-buccal cavity. Radula present. Pre-radular outlet of latero-ventral foregut glandular organs
into pouch with cone. Midgut with constrictions. Secondary genital opening unpaired. Without
copulatory stylets. Dorsoterminal sense organ and respiratory organs present.

42

Hiroshi Saito and Luitfried von Salvini-Plawen

Alexandromenia marisjaponica n. sp.
(Figures 1–11)
Material examined. Holotype – NSMT-Mo 73240, 82 mm long × 13 mm wide, anterior
body in cross sections on 161 slides, posterior body in cross sections on 152 slides, mid bodypreserved in 75% ethanol; off Shin-minato, Toyama Bay, Sea of Japan, approximately 36°50′N,
137°10′E, ca. 300 m, ﬁshing trawl; coll. H. Numanami, 31 March 2003. Paratypes – NSMT-Mo
73241, 1 specimen, 58 mm long × 8.8 mm wide, anterior part in cross sections on 83 slides, posterior part in cross sections on 42 slides, same lot as holotype. NSMT-Mo 78543, 1 specimen,
164 mm long × 17 mm wide, dissected; T/S Tanshu-maru St. TS09-T105, 36°06.43′N,
135°43.39′E–36°05.13′N, 135°42.46′E, 292–291 m; coll. T. Kubodera, 31 May 2009. NSMT-Mo78544, 1 specimen, 120 mm long × 10 mm, dissected; same lot with NSMT-Mo 78543. NSMTMo 78545, 1 specimen, 54 mm long × 10 mm wide, anterior part in cross sections on 108 slides,
posterior part in cross sections on 62 slides; R/V Tansei-maru St. KT-11-09-E2, 41°50.26′N,
139°34.03′E–41°48.70′N, 139°34.18′E, 388–538 m; coll. H. Saito, 29 May 2011. NSMT-Mo78546, 1 specimen, 20 mm long × 4 mm wide, dissected; R/V Tansei-maru St. KT-11-09-N4,
38°08.04′N, 136°49.64′E–38°09.00′N, 136°51.20′E, 617–604 m; coll. H. Saito, 1 June 2011.
NSMT-Mo 78547, 1 specimen, 69 mm long × 8 mm wide, dissected; T/S Tanshu-maru St. TS13S01, 38°01.30′N, 134°07.90′E –38°01.04′N, 134°07.38′E, 414–428 m; coll. K. Hasegawa, 24
August 2013.
Etymology. The name refers to the record of the present species in the Sea of Japan.
Diagnosis. Animals up to 164 mm × 17 mm. Body narrowly elongate, reddish, often withnumerous transverse wrinkles, neither dorsal keel nor warts. Mantle sclerites as two types of hollow needles, epidermal papillae stout and densely arranged. Up to 26 pedal folds, three entering
pallial cavity. Pallial cavity with radially arranged numerous respiratory folds and with anterior
pouch. Atrial papillae single, arranged among ciliated folds. Single dorso-terminal sense organ
located above anterior to middle pallial cavity. With three sets of foregut glands: subepithelial
multicellular pharyngeal glands and esophageal glands, as well as paired latero-ventral glandularorgans with ramiﬁed duct, opening far pre-radularly through pouch provided with ductile-lesscone. Radula apparatus with distinct support of turgescent cells. Radula teeth with two longhorn-like lateral denticles. Anterior midgut caecum short. Heart running freely. Distal-most portion of pericardioduct with single small sacculation (receptacula seminis?). Paired spawning duct
repeatedly winding, opening terminally united by single, narrow outleading duct.
Description. Animal large, elongate, 82 mm long × 13 mm wide at mid-body (Fig. 2A)(164 mm × 17 mm in NSMT-Mo 78543), without warts or dorsal keel, often with transverse wrinkles, rounded at both ends; mid-body almost round in cross-section. Pedal groove distinct,
extending to the mantle cavity. Color in life dark reddish brown (brown with reddish tint in larger
specimens: NSMT-Mo 78543, 78544; reddish orange in smaller specimens: NSMT-Mo 78545,
78546) (Fig. 2). Color in preserved specimen uniformly beige.
Cuticle thick, 290–330 μm at dorsum, 220–270 μm ventral of anterior body, densely penetrated by long stout epidermal papillae. Epidermis low, 7–10 μm, underlain by 250–700 μm“spongy” layer of lacunate connective tissue provided with scattered circular muscle ﬁbres; it isfollowed medially by more compacted circular musculature and a not very promenant longitudinal muscle layer. Sclerites in mantle cuticle of two types of hollow needles (Fig. 3): (1) small,slightly S-shaped needle, 125–130 μm in length × ca. 7 μm in diameter (Fig. 3C) rather sparsely
arranged tangentially to obliquely in several irregular, not intercrossing layers; (2) large, straightA New Species of Deep-sea Solenogastres from the Sea of Japan

43

Fig. 2. Alexandromenia marisjaponica n. sp. Habitus in life or just after the death. A, holotype, NSMT-Mo
73240; B-F, paratypes: B, NSMT-Mo 73241; C, NSMT-Mo 78545; D, NSMT-Mo 78546; E, NSMT-Mo
78543; F, NSMT-Mo 78544. All scales: 10 mm.

to distally slightly curved needles, 260–315 μm in length × 18–20 μm in diameter (Fig. 3A, B)
arranged in fairly radial orientation. Sclerites along pedal groove similar to small needles, butslightly thicker, ca. 9.5 μm in diameter and smaller hollow (ca. 60% of entire sclerite length)(Fig. 3D).
Ciliary pedal pit anteriorly elongate (Figs. 4, 5B) with 24–26 heavily ciliated pedal folds

44

Hiroshi Saito and Luitfried von Salvini-Plawen

which enter the pedal groove. Pedal folds thendecreasing to 19 in posterior body at portion
below anterior pericardium, among which threefolds enter the pallial cavity (splitting here to
ﬁve folds). Pedal glandular organ of a mass of
irregularly arranged, fairly small packages ofgland cells with dense, ﬁnely granulated content(Fig. 7A). Sole glands with same histologicalstructure as pedal glandular organ, which arearranged in paired latero-dorsal mass above thepedal groove (sparing the differently-shaped
ventral sinus) but open in all parts of the foot.
Dorso-posterior end of pallial cavity drawn
out, forming extended pallial cavity roof, thus
cavity opening located obliquely towards ventral (Fig. 9). Dorso-anteriorly pallial cavity atboth sides of hindgut extended and formingsome diverticula up to pericardium. Dorsal, central and posterior walls with numerous, radiallyarranged respiratory folds, which are 1.6–
1.7 mm in height, 90–96 in number in middle
portion of dorsal area (Figs. 9, 10, 11D: rf).
Hindgut opening into pallial cavity from dorsofrontal. Unpaired secondary genital opening(unpaired outlet of spawning duct) (Figs. 9, 10:
Fig. 3. Alexandromenia marisjaponica n. sp. Man- sdo) emptying centrally into pallial cavity above
tle sclerites, holotype. A, B, large dorsal sclerites; beginning of cavity opening. All space between
C, small dorsal sclerites; D, ventral sclerites,
dorsal body wall and respiratory folds, as wellalong pedal groove. Scale: 100 μm.
as anteriorly as far as behind pericardium, ﬁlledwith dense mass of suprapallial glands (Figs. 9,
10B, 11D: spg).
Circular and longitudinal musculature of body wall indistinct, medially of “spongy” layer
about equal thickness (35–50 μm), but longitudinal layer pairedly thickened to ca. 900 μm at ventral wall (Figs. 5B, 6A: bw). Paired dorso-ventral muscle bundles fairly prominent, outer ones
intercrossing each other midventrally above longitudinal muscle bundles of ventral wall, providing deep midgut constrictions (Figs. 5A). Foregut with thin inner circular muscle and outer longitudinal muscle layers in pharynx, which increase in thickness toward radula region, then decreasing thickness towards posterior end of the esophagus. No distinct sphincter around opening ofesophagus into midgut. Unpaired portion (outlet) of spawning duct with thick layer of circular
musculature.
Atrium located in front of but laterally ﬂanking mouth area (Fig. 4: at). Sensory area of
atrium as usual bordered by horseshoe-shaped ciliated tract, of which the anterior-most ventral
tracts, however, do not unite frontally; they rather form a pair of folds intruding the cavity. Anterio-dorsally, in addition to middorsal ciliated fold which diminishes posteriorly, horseshoeshaped tract beginning as pair of folds; the atrium itself is thus frontally subdivided by ﬁve ciliated folds; the two dorsal folds posteriorly delimit the lateral atrial pouches which are subdivided

A New Species of Deep-sea Solenogastres from the Sea of Japan

45

Fig. 4. Alexandromenia marisjaponica n. sp. Reconstructed organization of the anterior body from the left, holotype. Scale: 5 mm.

by another ventro-posterior fold; the middorsal area between the folds leads to the fairly separated mouth opening. Numerous atrial papillae almost single (ca. 150 μm long, 50 μm in diameter). All common atrio-buccal area surrounded by wide zone of ciliated epithelium.
Single dorsoterminal sense organ small, located either above anterior-most or middle regionof pallial cavity (Figs. 9, 10B, 11C: dts). Several pit- to tube-like infoldings in terminal body epithelium, which may resemble dorsoterminal sense organs, but are covered with cuticle.
Unpaired cerebral ganglion small compared to body size, positioned above anterior pharynx(1000 μm in width, 250 μm in thickness, 570 μm in length) (Figs. 4, 5B, 6A, B). Cerebral connectives (lateral and ventral cords) emerging separately but closely adjoining each other from bothsides of cerebral ganglion, running together posteriorly along pharyngeal wall: in distance of
1.2–1.3 mm from cerebral ganglion, lateral cords forming ﬁrst ganglia (ca. 190 μm in width,
160 μm in thickness, 100 μm in length); ventral cords getting distance from lateral cords behindﬁrst lateral ganglia, directing ventrally in pedal glandular organ, and forming behind pedal pit
ﬁrst ventral ganglia (ca. 350 μm × 150 μm across, 300 μm in length). Buccal connectives emerging at dorso-lateral portion of cerebral ganglion and extending to radula region, forming single
pair of buccal ganglia behind radula sheath (ca. 180 μm × 120 μm across, 150 μm in length); they
are interconnected by a ca.150 μm long commissure behind the radula apparatus. Two pairs offrontal nerves rising from ventral side of cerebral ganglion extending towards atrium.
All larger tracks (lateral and ventral cords) more or less medullary, though with serial
arrangement of fairly distinct lateral and ventral swellings with nuclei; latero-ventral connectives
and ventral commissures likewise possess nuclei. Posterior-most ganglia of lateral cords (ganglia
posteriora superiora: gps; ca. 300 × 190 μm in maximum size) located adjacent to opening of
pericardium into pericardioducts (holotype). Medullar, long suprarectal commissure (5 mm ×
120 μm in diameter) emerging from gps, extending along dorsal wall of terminal pericardium

46

Hiroshi Saito and Luitfried von Salvini-Plawen

Fig. 5. Alexandromenia marisjaponica n. sp. A, dissected anterior body, NSMT-Mo 78543; B, close up of pharynx, slightly dyed with Safranin. Scales: 5 mm.

(Fig. 9: sc), rather than above hindgut below pericardium (below pericardium above beginning ofpallial cavity in NSMT-Mo 78545). Posterior-most ganglia of ventral cords (ganglia posteriora
inferiora: gpi; ca. 350 × 300 μm in maximum diameter, 400 μm in length) located at both sides ofoutlet of spawning duct and interconnected by ventral as well as dorsal strong commissure.
Shortly behind gpi, another pair of smaller swellings formed likewise at both sides of unpaired
spawning duct.

A New Species of Deep-sea Solenogastres from the Sea of Japan

Fig. 6. Alexandromenia marisjaponica n. sp. Cross sections of anterior body, holotype. A, region of anterior
foregut, showing cerebral ganglion; B, close up of A; C, slightly posterior to section A; D, close up of C,
showing outlet duct of ventro-lateral foregut glandular organ, and the cone. Scales: 1 mm for A and C, 100 μm
for B and D.

47

48

Hiroshi Saito and Luitfried von Salvini-Plawen

Fig. 7. Alexandromenia marisjaponica n. sp. Cross sections of anterior body, holotype. A, region of radula apparatus; B, close up of A, showing radula; C, packages of latero-ventral foregut glandular organ with ductules
encircled by musculature; D, esophagus surrounded by pharyngeal glands. Scales: 1 mm for A and D, 200 μm
for C, 100 μm for B.

A New Species of Deep-sea Solenogastres from the Sea of Japan

49

Mouth opening and atrium forming common atrio-buccal cavity (Figs. 4, 5). Mouth opening
located immediately behind folded dorsal tract of peri-atrial ridge. Inner surface of anterior pharynx with numerous, irregular transverse folds, that of posterior pharynx with thick longitudinalfolds; both with scattered, subepithelially arranged pharyngeal glands. Inner surface of esophagus with ﬁner longitudinal folds provided with numerous minute sub-folds, thus forming villous
appearance. Posterior-most part of esophagus protruding into midgut ventro-frontally as free
tube. Paired latero-ventral foregut glandular organs opening laterally far anterior to radula apparatus (Figs. 4, 6C, D), as it typical for Amphimeniidae (type D in Salvini-Plawen, 1978 or
Amphimenia type according to Handl and Todt, 2005). Out-leading duct of paired organ and alltheir ramiﬁcations with median ridge encircled by musculature (Fig. 7C). Anterior-most portionof each out-leading duct curving medially and widening into pouch where the median ridge isenlarged to form a cone protruding into the pouch (Fig. 6D). No ductule within cone and no
opening papilla (as described and ﬁgured
for Alexandromenia gulaglandulata Salvini-Plawen, 2008: Fig. 20A); rather, thepouch at each side distally connecting
directly to the lateral wall just behind thearea of irregular transverse folds of theanterior pharynx. Each lateral out-leading
duct continuous with dorsally curved collecting duct (Fig. 4). This duct receivingfrom anterior ductules which have theopenings of the glands in their package;
posteriorly, the opening ductules of thegland packages are ramiﬁed. All together
extending from region of out-leading duct
opening to middle portion of esophagus.
These globular to egg-shaped packages (upto 1300 μm in height, 700–1300 μm in
Fig. 8. Alexandromenia marisjaponica n. sp. Raddiameter) arranged more or less circularly
ula tooth, NSMT-Mo 78547. Scale: 1 mm.

Fig. 9. Alexandromenia marisjaponica n. sp. Reconstructed organization of the posterior body from the left,
holotype. Scale: 5 mm.

50

Hiroshi Saito and Luitfried von Salvini-Plawen

Fig. 10. Alexandromenia marisjaponica n. sp. A, dissected posterior body, NSMT-Mo 78543; B, close up of posterior most part. Scales: 5 mm.

around foregut (Fig. 7A); each package is surrounded by a thin layer of musculature. Esophagus
behind latero-ventral glandular organs surrounded by a 300–500 μm thick layer of subepithelial
multicellular glands (Figs. 4, 7D) which open intercellularly (esophageal glands) and are of similar structure as pharyngeal glands.
Monoserial radula (Fig. 7B) with distinct support of many turgescent (“chondroid”) cells,
located almost perpendicularly to foregut. At least 28 transverse rows of teeth counted (NSMTMo 78543). Each tooth with horn-like denticle at both lateral borders, measuring 234 μm in
width and 215 μm in height (NSMT-Mo 78547), being somewhat larger with longer denticles

A New Species of Deep-sea Solenogastres from the Sea of Japan

51

Fig. 11. Alexandromenia marisjaponica n. sp. Cross sections of posterior body, holotype. A. section throughjoining portion of pericardioduct and spawning duct; B, section through pericardium and spawning duct; C,
section through unpaired part of spawning duct, and suprarectal commissure; D, pallial cavity, showing respiratory folds and suprapallial glands. Scales: 1 mm for A and C, 100 μm for B and D.

posteriorly (Fig. 8). In radula sheath, median edge between two denticles with weak interconnection.
Midgut with anterior dorsal caecum extending to area above radula. Posteriorly, midgut
increasing in volume, encompassing posterior esophagus and its subepithelial multicellular
glands, thus protruding into midgut lumen (Figs. 4, 5). Midgut epithelium 100–200 μm thick andfairly uniform. It strongly creased by up to 3 mm long folds towards lumen, resulting in enormous surface enlargement. Gonadial pouches dorsally intruding midgut. Hindgut opening,

52

Hiroshi Saito and Luitfried von Salvini-Plawen

accompanied by some irregular anterior sacculations of mantle cavity, in dorso-frontal wall of
pallial cavity.
Anteriorly, paired gonad extending up to opening of esophagus to above midgut (up to anterior esophagus in NSMT-Mo 78543). Paired gonad voluminous, forming ventral pouches intruding midgut (Figs. 5A, 9, 10A). Eggs up to diameter of 250 μm (same diameter in NSMT-Mo
78543). Gonad tapering in posterior body, continued by about 3 mm long gonopericardioducts,
which have a high, folded ciliary epithelium and open into antero-dorsal portion of the pericardium with distance of 580 μm between the ducts. Paired lateral ciliary tracts extending along
entire length of pericardium. Heart, with ventricle and unpaired atrium/auricle, extending freely
within pericardial cavity; atrium invaginated ventral side of pericardium.
Each pericardioduct emerging from ventro-lateral wall near posterior end of pericardium(Fig. 9) and lined by somewhat folded, ciliated epithelium surrounded by circular musculature.
Near distal end of pericardioducts with small sacculation (seminal receptacle?) (Fig. 9, 11A: sr);
pericardioducts then bending ventrally, connected within short distance with spawning ducts.
Each spawning duct lacking circular musculature and sinuously wound in entire length. Bothducts surrounded by dense mass of spawning duct glands packed into slender groups of up to1500 μm in length (Fig. 9, 11B). Glands occupying entire lateral body space, from proximal pericardioducts to distal end of pericardioducts. In region below suprarectal commissure or gps, bothterminal spawning ducts passing over to short medially joined common portion which opens
ventrally into unpaired out-leading duct (Fig. 9, 11C: sd, sdo). These bends, as well as unpaired
out-leading duct, receiving distinctly different type of small, subepithelially arranged glands,
which are packed into dense groups (Fig. 9: og). Unpaired outlet itself surrounded by circular
musculature and opening, accompanied by a short pouch, below anus centrally into pallial cavity,
already inmidst of respiratory papillae. No copulatory stylets or other accessory genital organs
present.
Biological Remarks. The present species appears to feed on a hexacorallian sea anemone.
In the midgut contents scattered nematocysts including spirocysts are present. Dr. Hisanori Kotsuka, a staff of Misaki Marine Biological Station, University of Tokyo kindly informed us that hehad found a large, approximately 10 cm long, reddish solenogastres clung to a sea anemone,
which was incidentally caught by a gillnet operated near the type locality of the present species,
at the depth from 400–500 m off Noto Peninsula, the Sea of Japan (personal observation). In thegenus Alexandromenia, highly possible feeding on a hexacorallian sea anemone, Glyphoperidium bursa Roule, 1909 (Anthozoa: Hexacorallia: Actiniidae) has been reported for A. heteroglandulata by Salvini-Plawen and Schwabe (2012). Hexacorallia are prey for quite a number of different Solenogastres (see Salvini-Plawen, 1981), such as Sasaki and Saito (1999) reported inJapanese waters the feeding habit on a sea anemone for a giant solenogastres, Neomenia yamamotoi Baba, 1975.
Comparison. In the genus Alexandromenia, ten valid species have been recognized to date
(Salvini-Plawen, 2008 and present paper) among which four species were described from Antarctic/Subantarctic waters: A. acuminata Salvini-Plawen, 1978; A. antarctica Salvini-Plawen,
1978; A. latosoleata Salvini-Plawen, 1978; A. heteroglandulata Salvini-Plawen and Schwabe,
2012, four species from the North Atlantic: A. crassa Odhner, 1921; A. grimaldii Leloup, 1946;
A. pilosa Handl and Salvini-Plawen, 2002; A. gulaglandulata Salvini-Plawen, 2008, two fromthe East Paciﬁc: A. agassizi Heath, 1911; A. valida Heath, 1911. The poorly described A. crassa
Odhner, 1921 has been doubted as concerns the generic assignment because it was describedwith a “pair of small salivary glands opening into the radula sac” (Salvini-Plawen, 2008: 895).

A New Species of Deep-sea Solenogastres from the Sea of Japan53

In comparison, the present species collected from the Northwest Paciﬁc differs in its zoogeographical provenance from all other species. Among these, the present species most resembles A.
heteroglandulata described from off Queen Maud Land, Antarctica, 2084–2163 m, by its large
body size and the internal organization, especially by the ductule-less cone of the out-leading
ducts of the latero-ventral foregut glandular organs, by the conﬁguration of the atrium, which
extends posteriorly around the pharynx, and by the arrangements of alimentary tract and the
gonopericardial organs with a separate set of glands associated to the outlet. However, it differsfrom this species by having a larger number of pedal folds, by much larger radula teeth with longer denticles, by a shorter anterior midgut caecum which encompasses smaller part of alimentarytract and its glandular organs, by the beginning of pericardioducts (lateral, not at posterior extension or “horn” of the pericardium), and by less developed diverticula of the pallial cavity.
The present species also differs from the other two North Paciﬁc species, A. agassizi and A.
valida. A. agassizi described from near Revillagigedo Islands, East Paciﬁc, Mexico, at 840 m, hasa smaller size (25 mm in length), no “spongy” body wall, larger number of radula teeth (45–53), a
prominent and different set of pharyngeal glands, as well as the common origin of the cerebral
connectives. A. valida described from off California at 1100–2500 m has a smaller size (32 mm inlength) and smaller spicules, no “spongy” body wall, a thick sheath of pharyngeal glands, as well
as a radula with tall basal plate with denticles which are re-curved somewhat outwardly near thetips.
The differences between the present species and the remaining six species are as follows: A.
acuminata from the Scotia Sea, Antarctica, 2886–3040 m, has a smaller size (40 mm in length),which is rather rapidly narrowing towards both ends, fewer pedal folds (maximum eight), coneof foregut glandular organ opening with ductule, different conﬁguration of the pallial cavity. A.
antarctica from the Bransﬁeld Strait, Antarctica, at 662–1120 m also has a smaller size (20 mm inlength), and smaller number of pedal folds (seven), which do not enter the pallial cavity, radulateeth with several small denticles at the inner edge between the horn-like denticles, and the conewith a ductule of the out-leading ducts of the latero-ventral foregut glandular organs. A. latosoleata from the South Paciﬁc at 459 m has a smaller size (35 mm in length), pallial cavity withfewer respiratory folds (16–18), cone of foregut glandular organ opening with ductule and short
but palmular seminal receptacle. A. grimaldii from off the Azores Islands 1250 m, has a smaller
size (20 mm in body length), thicker layer of the pharyngeal glands, U-shaped radula plates with
one pair of latero-medial denticles (Salvini-Plawen, 1972), and a straight paired portion of thespawning ducts which lack seminal receptacle. A. pilosa from the Trondheimsfjord, Norway, at
180–240 m, has a much smaller size (9 mm in length), a second pair of small denticles on the
inner edge between the horn-like radula denticles, and the out-leading ducts of the latero-ventral
foregut glandular organs open fairly close to the radula. A. gulaglandulata from the West European Basin at 1050 m has a smaller size (21 mm in length), an additonal set of foregut glands,
high radula base with thinner horn-like denticles and a simple outlet of the straight, terminally
fused spawning ducts.
Acknowledgements
We thank the following persons for their kindest cooperation in sampling and/or providing
specimens at our disposal: Captains and crews of R/V Tansei-maru and T/S Tanshu-maru, Dr.
Tsunemi Kubodera and Dr. Kazunori Hasegawa, NSMT, Dr. Hideki Numanami, Tokyo Kasei
Gakuin University. We also thank Dr. Hisanori Kotsuka, Misaki Marine Biological Station, Uni-

54

Hiroshi Saito and Luitfried von Salvini-Plawenversity of Tokyo for providing us the biological information on the present new solenogastres.
References
García-Álvarez, O. and L. v. Salvini-Plawen, 2007. Species and diagnosis of the families and genera of Solenogastres(Mollusca). Iberus, 25: 73–143.
Gil-Mansilla, E., O. García-Álvarez and V. Urgorri, 2011. A new genus and two new species of Cavibelonia (Mollusca,
Solenogastres) from the Abyssal Angola Basin. Cahiers de Biologie Marine, 52: 233–244.
Gil-Mansilla, E., O. García-Álvarez and V. Urgorri, 2012. Three new species of Kruppomenia (Solenogastres, Simrothiellidae) from the abyssal Angola Basin. The Journal of Marine Biological Association U.K., 92: 349–359.
Handl, C. and L. v. Salvini-Plawen, 2002. New records of Solenogastres-Cavibelonia (Mollusca) from Norwegian fjords
and shelf waters including three new species. Sarsia, 87: 423–450.
Handl, C. and C. Todt, 2005. Foregut glands of Solenogastres (Mollusca): Anatomy and revised terminology. Journal ofMorphology, 265: 28–42.
Heath, H. 1911. Reports on the scientiﬁc results of the expedition to the tropical Paciﬁc. XIV. The Solenogastres.
Memoirs of the Museum of Comparative Zoology at Harvard College, 45: 1–182.
Leloup, E., 1946. Alexandromenia grimaldii sp. nov., solénogastre bathypelagique. Bulletin du Musée royal dʼHistoire
naturelle de Belgique, 22: 1–12.
Odhner, N. J., 1921. Norwegian Solenogastres. Bergens Museums Aarbok 1918–19, Naturvidenskabelig raekke, 3: 1–86.
Salvini-Plawen, L. v., 1972. Revision der monegassischen Solenogastres (Mollusca, Aculifera). Zeitschrift für zoologische Systematik und Evolutionsforschung, 10: 215–240.
Salvini-Plawen, L. v., 1978. Antarktische und subantarktische Solenogastres (Eine Monographie: 1898–1974). Zoologica(Stuttgart), 128: 1–315.
Salvini-Plawen, L. v., 1981. The molluscan digestive system in evolution. Malacologia, 21: 371–401.
Salvini-Plawen, L. v., 2008. Contributions to West European Cavibelonia (Mollusca, Solenogastres) with two new species. Zoosystema, 30: 873–897.
Salvini-Plawen, L. v. and E. Schwabe, 2012. A new deep-sea Solenogastres (Mollusca) from the Antarctic. Marine Biodiversity, 42: 25–35.
Sasaki, T and H. Saito, 1999. Feeding of Neomenia yamamotoi Baba, 1975 (Mollusca: Solenogastres) on a sea anemone.
Venus, 64: 191—194.
Zamarro, M., O. García-Álvarez and V. Urgorri, 2012. Three new species of Pruvotinidae (Mollusca: Solenogastres) from
Antarctica and NW Spain. Helgoland Marine Research, 67: 423–443.