Pseudunela espiritusanta, Neusser & Schrödl, 2009

Neusser, Timea P. & Schrödl, Michael, 2009, Between Vanuatu tides: 3 D anatomical reconstruction of a new brackish water acochlidian gastropod from Espiritu Santo, Zoosystema 31 (3), pp. 453-469 : 455-462

publication ID	https://doi.org/ 10.5252/z2009n3a4
persistent identifier	https://treatment.plazi.org/id/7C218781-B002-FFD6-0925-EE84FF44634A
treatment provided by	Marcus
scientific name	Pseudunela espiritusanta
status	sp. nov.

Treatment

Pseudunela espiritusanta View in CoL n. sp.

TYPE MATERIAL. — Holotype: ZSM 20080115, 3.5 mm preserved body length, stored in 75% EtOH. Paratypes: ZSM 20070968 and 20080791 (two serially sectioned specimens), ZSM 20080116 (head removed for radula analysis, stored in 96% EtOH), ZSM 20080117 and 20071118 (used for molecular studies).

TYPE LOCALITY. — Vanuatu, Espiritu Santo Island, leaving Luganville to Palikulo Bay. Expedition SANTO 2006, stn VM 53, 15°30’58”S, 167°11’52”E.

ETYMOLOGY. — Pseudunela espiritusanta n. sp. is named according to the type locality on the island of Espiritu Santo.

DISTRIBUTION. — Known only from the type locality.

DESCRIPTION

Habitat

Intertidal zone of type locality characterized by rocks, dead coral pieces and coarse sand ( Fig. 1A View FIG ). During high tide, seawater reaches the bank beside the road. Pseudunela espiritusanta n. sp. inhabits lower intertidal in brackish environment. It lives underside of rocks deeply embedded into coarse sand ( Fig. 1B View FIG ); interstices filled with mixture of sea and emerging fresh subsoil water. Habitat keeps wet during low tide. Despite further sampling, the new species could not be found in neighbouring sand and gravel patches. Other molluscan species associated with P. espiritusanta n. sp. in the same habitat were at least Neritilia littoralis Kano, Kase & Kubo, 2003 and two undescribed Neritilia spp. (Kano pers. comm.).

External morphology

Body divided into anterior head-foot complex and posterior elongated visceral hump (vh) ( Fig. 1C, D View FIG ). Head-foot complex partially retractable into temporary cavity of visceral hump. Length of crawling specimen, 9 mm. Body colour of living specimens translucent-whitish, digestive gland yellowish.Labial tentacles (lt) broad at base ( Fig.1D View FIG ), tapering to distal end, usually held at 45° to mid line. Rhinophores (rh) slightly shorter and narrower, tapering ( Fig. 1D View FIG ). Pigmented eyes, only clearly visible laterally.Densely ciliated foot (f) broader than anterior head-foot complex ( Fig. 1D View FIG ), tail extending about two-thirds of visceral hump; tip pointed. Visceral hump in living specimens usually curved ( Fig. 1D View FIG ). Heart visible within prominent bulb at anterior right side of visceral hump. Subepidermal spicules (sp) bean-shaped ( Figs 1C View FIG ; 8A View FIG ), small (70-135 µm) in tentacles, larger (200-300 µm) in foot and around cns and pharynx (Fig. 3D).

Microanatomy

Central nervous system. cns euthyneurous. Paired rhinophoral (rhg), cerebral (cg), pedal (pg), pleural (plg), optic (og), buccal (bg) and gastro-oesophageal (gog) ganglia; three distinct separated ganglia on visceral nerve cord, plus presumed osphradial ganglion (osg) ( Fig. 2 View FIG ). All ganglia excluding buccal and gastro-oesophageal ganglia pre-pharyngeal (Fig. 3C, D). Large cerebral ganglia (c. 130 µm in diameter) with short commissure ( Figs 2 View FIG ; 3A, B). Labiotentacular nerve (ltn) emerging anteroventrally from cerebral ganglion, ramifying into (at least) 6 branches within labial tentacles ( Figs 2 View FIG ; 3A). Rhinophoral ganglion (c. 40 µm in diameter) anterodorsal to each cerebral ganglion ( Figs 2 View FIG ; 3A); short, single cerebro-rhinophoral connective. Rhinophoral nerve (rhn) emerging from rhinophoral ganglion ( Figs 2 View FIG ; 3A). Th in nerve arising at base of rhinophoral nerve ( Fig. 2 View FIG ), extending towards ciliated ridge posterior to rhinophore. Optic ganglion ( Figs 2 View FIG ; 3A, B) (c. 35 µm in diameter) situated posterior to rhinophoral ganglion, attached to cerebral ganglion. Th in optic nerve (on) ( Figs 2 View FIG ; 3B) innervating pigmented eye (ey) ( Figs 2 View FIG ; 3A, B) (c. 45 µm in diameter). Anterior accessory ganglia absent.

Pedal ganglia (c. 100 µm in diameter) connected by thin, long commissure ( Figs 2 View FIG ; 3B). Statocyst (st) ( Figs 2 View FIG ; 3B) posterior to each pedal ganglion. Four pedal nerves (pn) per ganglion (Fig. 3A), extending anteriorly, posteriorly and ventrally. Pleural ganglion ( Figs 2 View FIG ; 3A, B) (c. 55 µm in diameter) posterior to and equidistant from cerebral and pedal ganglion, connected to both by short connectives forming pre-pharyngeal nerve ring. Visceral nerve cord short with three distinct ganglia: left parietal (pag) ( Figs 2 View FIG ; 3B) (c. 55 µm in diameter), fused subintestinal/visceral (subg+vg) ( Figs 2 View FIG ; 3B) (c. 75 µm in diameter) and fused right parietal/supraintestinal (pag+supg) ganglia ( Figs 2 View FIG ; 3B) (c. 70 µm in diameter). Left pleuro-parietal, parietal-subintestinal/visceral and right pleuroparietal/supraintestinal connectives short, subintestinal/visceral-parietal/supraintestinal connective longer. Left parietal ganglion producing one nerve. Robust nerve emerging from subintestinal/visceral ganglion extending to visceral hump (Fig. 3A, B). Tentative osphradial ganglion ( Figs 2 View FIG ; 3A, B) (c. 45 µm in diameter) with one bifurcating nerve linked to parietal/supraintestinal ganglion. Buccal ganglion (c. 65 µm in diameter) posterior to pharynx (ph) ( Figs 2 View FIG ; 3D; 7B), thin buccal commissure situated ventral to oesophagus. Radular nerve (rn) thin, branching from buccal commissure ( Fig. 2 View FIG ). Thin cerebro-buccal connective emerging anteriorly from each buccal ganglion, not traceable along entire length. Small gastro-oesophageal ganglion ( Figs 2 View FIG ; 3D; 7B) (c. 30 µm in diameter) slightly dorsally to each buccal ganglion, innervating oesophagus (oe). Th in nerve innervating the salivary gland (sgl), branching from buccal-gastro-oesophageal connective ( Fig. 2 View FIG ).

Digestive system. Mouth opening ventrally between labial tentacles. Anterior pedal gland (apg) ( Fig. 8A View FIG ) opening ventral to mouth. Oral tube (ot) long, unciliated (Fig. 3C). Paired oral glands (otg) flanking oral tube ( Fig. 8A View FIG ). Pharynx (ph) bulbous and muscular (Figs 3C, D; 7A). Jaws absent. Radula (r) c. 575 µm long, hook-shaped

ndd rpd

ndv np

C meg alg

rs bc vd

s mug do

(Fig. 3C, D) and asymmetric with formula 67 × 1.1.2; upper ramus with 48 rows (c. 410 µm long), lower ramus with 19 rows (c. 165 µm long). Rhachidian tooth triangular (21 µm high, 18 µm wide) with prominent central cusp (cc) and 4-7 thinner denticles (d) per side ( Fig. 4 View FIG A-C). Lateral teeth plate-like ( Fig. 4A View FIG ). Left lateral tooth (ltl) (5-7 µm high, 29 µm wide) with prominent, cuspid denticle on anterior margin 6 µm in length; deep triangular notch (n) on posterior margin of tooth ( Fig. 4E View FIG ) receiving denticle of subsequent tooth. First/inner right lateral tooth (ltr1) similar to left lateral but slightly smaller (5-6 µm high, 25 µm wide), with small blunt protrusion at inner side of denticle ( Fig. 4D View FIG ). Outer margin of left lateral tooth rounded; outer margin of first right lateral tooth straight ( Fig. 4A View FIG ). Second/outer right lateral tooth (ltr2) small and quadratic plate (8 × 8 µm) ( Fig. 4D View FIG ).

Ciliated oesophagus (oe) long, emerging posterodorsally from pharynx (Figs 3C, D; 7B), flanked by longitudinal muscles. Paired, large salivary glands (sgl) (Figs 3C; 7B) discharging into posterior pharynx via salivary gland ducts (sgd) ( Fig. 7B View FIG ).

Digestive gland (dg) sac-like (Fig. 3C), inner surface heavily folded, lumen empty, situated dorsally of ovotestis (ov), extending to end of visceral hump ( Fig. 1C View FIG ). Stomach continuous with broad, anterior, lobed part of digestive gland. Intestine (i) short (Fig. 3C), densely ciliated ( Fig. 8C, D View FIG ). Anus (a) (Fig. 3C) ventrolaterally on right side of visceral hump, slightly anterior to nephropore.

Circulatory and excretory systems. Circulatory and excretory systems situated at right of body ( Fig. 1C View FIG ), at anterior end of visceral hump. Heart (h) (c. 160 µm) with one well-developed muscular ventricle (Figs 5A; 8D), thin valve at posterior end ( Fig. 8D View FIG ). Atrium not apparent. Aggregations of discrete cells in lumen of ventricle (v) ( Fig.8D View FIG ). Aorta (ao) (Figs 5A; 8C) emerging anteriorly from ventricle, extending to anterior head region. Heart surrounded by thin-walled pericardium (pc) (Fig. 5A); thick layer of blue stained epicardial cells of unknown function embracing ventricle ( Fig. 8D View FIG ). Kidney (k) elongated (Fig. 5A), internally divided into narrow lumen (kn) defined by tissue with small vacuoles, and wide lumen (kw) bordered by highly vacuolated tissue ( Fig. 8C, D View FIG ). Both lumina joining in posterior part of kidney.Renopericardial duct (rpd) well developed and densely ciliated (Figs 5A; 8C). Connection between kidney and nephroduct narrow and ciliated ( Fig. 8B View FIG ). Nephroduct long; dorsal branch (ndd) extending posteriorly, continuing anteriorly via ventral branch (ndv) (Fig. 5A); distally looped. Nephropore (np) ventrolateral at right side of visceral hump, slightly posterior to anus.

Reproductive system. Simultaneously hermaphroditic, androdiaulic. Ovotestis (ov) sac-like ( Figs 1C View FIG ; 5B; 6), extending over almost entire visceral hump, ventral to digestive gland; not separated into follicles, but spermatocytes situated more anteriorly and ventrally, oocytes dorsally and posteriorly. Details of individual oocytes obscured by large amount of yolk. Anterior to ovotestis sac-like ampulla (am) filled with unorientated autosperm in disorder (Figs 5B, C; 6; 7D). Small receptaculum seminis (rs) with orientated allosperm (Figs 5C; 6; 7D). Sperm heads short. Th ree female nidamental glands: tubular albumen (alg), sac-like membrane (meg) and tubular mucus gland (mug) (Figs 5B, C; 6). Membrane gland branching offin middle of mucus gland. Albumen gland characterized by cells containing dark blue-stained granules; cells of mucus and membrane glands with violet-staining contents. All nidamental glands densely ciliated. Distal part of mucus gland extending to right side of body wall where hermaphroditic duct separates into vas deferens (vd) and oviduct (do) (Figs 5C; 6). Oviduct short, narrow (Fig. 5C; 6), dividing into long slender, blind duct (bc) (bursa copulatrix or bursa stalk) (Fig. 5B, C; 6) and distal gonoduct extending to female gonopore (fgo). Large muscular sphincter (s) surrounding female gonopore (Figs 5B, C; 6; 7C). Female gonopore ventrolateral at right side of visceral hump, anterior to anus and nephropore.

Subepidermal, ciliated vas deferens (Figs 5C; 6; 7C) extending along right body side to opening at base of right rhinophore. Anterior male copulatory organs cephalic. Posterior-leading vas deferens (vdp) connecting to large tubular prostate (pr) (Figs 5D; 6; 7A). Ejaculatory duct (ed) connecting to elongated, muscular penial papilla (p) (Figs 5D; 6; 7A). Curved hollow penial stylet (pst) (c. 80 µm long) partially retractable into muscular penial bulb (Figs 5D; 6). Blind glandular paraprostate (ppr) (Figs 5D; 6) considerably smaller than prostate, connected by paraprostatic duct (ppd) to muscular basal finger (bf) (Figs 5D; 6; 7A, B). Paraprostatic duct entering basal finger subapically and opening apically via a long hollow, slightly curved stylet (st) (c. 340 µm long). Penis and basal finger not connected, surrounded by common penial sheath (ps) ( Fig. 6 View FIG ).