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Bibliographic Details
Main Authors:	Cobo, M. Carmen, Marques, Antonio C., Tweedt, Sarah M., Strong, Ellen E.
Format:	Recurso digital
Language:
Published:	Zenodo 2026
Subjects:	Biodiversity Taxonomy Animalia Mollusca Solenogastres Pholidoskepia Dondersiidae Nematomenia Nematomenia quattriniae
Online Access:	https://doi.org/10.5281/zenodo.19136845
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Nematomenia quattriniae Cobo & Strong sp. nov.Type material.Holotype • USNM 1716720, serial sections (20 slides), DNA extraction, and sclerite preparations (one SEM stub, two light microscopy slides); Paratype 1 • USNM 1720103, fragment in 96 % ethanol, DNA extraction, and sclerite preparations (one SEM stub); Paratype 2 • USNM 1716719, whole specimen in 96 % ethanol. Jeanerette Hill Louisiana continental slope (USA); 27.65009°N, 91.78699°W. 581 m depth.Etymology.The species is named in honor of Dr. Andrea Quattrini, in recognition of her leadership and significant contributions to deep-sea biology and biodiversity exploration.Diagnosis.Body long and narrow, with pointed posterior end. Light yellow in color. Scaly appearance. Two types of sclerites: leaf-shaped scales (four variations) and oar-shaped scales; oar-shaped scales less abundant than leaf-shaped scales. With few solid acicular sclerites. Single pedal fold. Bulky anterior pedal glands. Atrium with simple digitiform papillae. Ventrolateral foregut glands of type A with short and wide ducts (blister-shaped). Dorsal foregut gland. Monoserial radula. Subradular pouch and bipartite radular sac. Midgut without caecum or lateral constrictions. With one dorso-terminal sensory organ. With seminal receptacles and seminal vesicles. Without accessory copulatory structures. Without respiratory folds.Description.External morphology: Body long and narrow with rounded anterior end and a narrow, pointed posterior end (10.5–14.4 mm long, 0.35–0.4 mm wide in the mid-body region) (Fig. 2 A, E). Scaly appearance (Fig. 2 D). Light yellow and slightly translucent (Fig. 3 A); dorsal sinus visible by transparency (pink line; Fig. 3 B). Color fades to white after fixation in 95 % ethanol (Fig. 2 A – D). Pedal groove and opening of the atrio-buccal cavity (Fig. 2 B, C) externally evident.Mantle: Mantle epidermis very thin (1.2–1.4 μm), lacking papillae, and with a thin cuticle (8–24 μm thick ventral region, 20–40 μm dorsal region) with four leaf-shaped and one oar-shaped scale types (Fig. 4). Leaf-shaped scales: 1) Type 1, the most common type: asymmetrical, 80–110 μm long, 30–38 μm wide, with a slightly pointed distal end and a rounded (Fig. 4 D 1) or flatter base (Fig. 4 E 1); 2) Type 2, almost as abundant as the previous type: symmetrical, 70–120 μm long, 30–38 μm wide, with very straight sides and a pointed tip, and a rounded (Fig. 4 D 4) or flatter base (Fig. 4 E 2; 3) Type 3: asymmetrical, 90–95 μm long, 34–38 μm wide, with one flat side and a flat base; 4) Type 4: nearly tongue-shaped, 90–95 μm long, 38–44 μm wide, with a broad flat base and a rounded distal end. Oar-shaped scales: 55–70 μm long, 8–9 μm wide, interspersed among leaf-shaped sclerites (Fig. 4 B). Isolated solid, circular, sclerites, approx. 95 μm in diameter, 4 μm thick.Nervous system and sensory organs: The atrium (86 μm long, 98.5–150 μm wide, 96–180 μm high) opens ventrally (125 μm long) and has eight to ten simple digitiform papillae (50–80 μm long, 0.8–20 μm wide) (Fig. 5 A). Cerebral ganglion rounded in cross-section (Fig. 4 C) (110 μm long, 42–83 μm in cross-section) (Fig. 5 C). With a dorso-terminal sensory organ in the mid-posterior region, the characterization of which was complicated by its small size.Pedal groove and mantle cavity: The pedal groove contains a flat pedal fold (10–12.5 μm wide, 2–3 μm high) that continues until the mantle cavity (Fig. 5). Pedal glands of a single type that discharge laterally in a simple, ciliated pedal pit (130 μm long, 80 μm wide, 25–40 μm high) (Fig. 5 B). The pedal glands are bulky and surround the foregut (Fig. 5 C) in its anterior and mid regions. The mantle cavity opening is ventro-terminal and straight (100 μm long; 25–40 μm wide) (Fig. 5 L). The cavity lacks respiratory folds and is divided into two regions: a posterior region where the rectum discharges and a highly glandular anterior region that continues as an internal pouch where the spawning duct discharges.Digestive system: The mouth opens dorsally at the end of the atrium and continues as the narrow foregut, rounded in cross-section (45 μm long, 30–35 μm diameter), surrounded by a thin muscular layer (2–4 μm) (Fig. 5 B). The foregut enlarges and flattens slightly (120 μm wide, 50 μm high) where it receives the discharge of the dorsal gland (70 μm long, 80 μm wide, 80–84 μm high) (Fig. 5 C, D). The foregut continues posteriorly as a narrower, rounded tube (approx. 80 μm diameter) where it receives the ducts of the ventrolateral foregut glands. The ventrolateral foregut glands are blister-shaped (Fig. 5 E) and consist of two short and wide, simple ducts (50 μm in length, 20–30 μm in diameter) with inner musculature and extraepithelial gland cells (type A). No posteriorly bent necks of the glandular cells were observed (Pararrhopalia - type; Handl and Todt 2005). The foregut continues to narrow to the radular region (43–40 μm diameter), bearing a thicker layer of musculature (both longitudinal and circular; 10 μm) (Fig. 5 F). The radular apparatus consists of a monoserial radula (Fig. 6) of approximately seven rows, a posteriorly bipartite radular sac (45 μm long, 14–18 μm diameter), and a sub-radular pouch (30 μm long, 10 μm diameter) (Fig. 5 F). Each tooth is composed of a broad (approx. 10 μm wide), non-serrated base (Fig. 6 D) bearing two long denticles (8–12 μm high, <1 to 2 μm wide) that are directed inwards (Fig. 6 C, E). The esophagus (> 400 μm long, 35 to 40 μm in diameter) joins the midgut centrally. The midgut has no caecum or lateral constrictions. The analysis of the serial sections revealed presence of food in the digestive tract, including hydrozoan cells (Fig. 6 F, G). The rectum (30–50 μm wide, 50–100 μm high) discharges dorsally into the posterior region of the mantle cavity (Figs 5 L, 6 B).Gonopericardial system: The gonads are well formed in the holotype, with numerous spermatocytes (Fig. 5 I). The pericardium (500 μm long, 25–100 μm diameter) is rounded in cross-section with a centrally placed heart (Fig. 5 K). With seminal vesicles in the anterior region of the pericardioducts (Fig. 5 K). The pericardioducts (250 μm long, 7.5 μm diameter) connect laterally in the posterior region of the pericardium and dorsally with the spawning duct in its mid-posterior region. The spawning duct has a paired region much shorter and smaller (80 μm in length; 20–40 μm diameter) (Fig. 5 I) than the fused part (225 μm in length; 130–250 μm in diameter), which is very glandular and terminates in the anteroventral pouch of the mantle cavity (Fig. 5 J, K).Taxonomic remarks.The new species is unequivocally placed in the family Dondersiidae based on the following diagnostic characters: the presence of at least two types of scales (leaf- and oar-shaped), a non-serrated, monoserial radula, and type A ventrolateral foregut glands. The scleritome, body shape, and coloration align with diagnostic features of the genus Nematomenia (Cobo and Kocot 2021). Although the radula was only partially observed in serial sections of the holotype, its structure is consistent with Nematomenia. The presence of seminal receptacles and blister-type foregut glands further supports its placement within Nematomenia. A notable distinguishing feature of Nematomenia quattriniae sp. nov. is the presence of a dorsal foregut gland shared only with N. ptyalosa and N. brasiliensis (Table 3). This feature clearly distinguishes the new species from N. flavens, which is also yellow but brighter in color. The new species differs from N. ptyalosa by possessing a subradular pouch and dorsal keel. Nematomenia quattriniae sp. nov. shares the dorsal foregut gland, dorsal keel, and other diagnostic characters with N. brasiliensis (Table 3), but possesses seminal receptacles and seminal vesicles, whereas N. brasiliensis has only seminal receptacles (Table 3). Moreover, the scleritome of the two species differs in both the shape (Cobo and Kocot 2021: fig. 5) and number of sclerite types: the new species possesses four types of leaf-shaped scales and one type of oar-shaped scale, whereas N. brasiliensis has six types of leaf-shaped scales and two types of pallet-shaped scales.DNA barcoding and phylogenetic analysis.COI sequences were obtained for USNM 1716720 and USNM 1720103. Phylogenetic analysis (Fig. 7) based on COI sequences resolved Nematomenia quattriniae sp. nov. as the sister taxon of N. banyulensis (bootstrap support, bs = 90). Nematomenia was recovered within a clade that included other dondersiids but also Macellomenia (Macellomeniidae), suggesting a non-monophyletic relationship among these families.

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