Pseudolepetodrilus costaricensis, Betters & Cortés & Cordes, 2024

Betters, Melissa J., Cortés, Jorge & Cordes, Erik E., 2024, New species and records of limpets (Mollusca, Gastropoda) from the Pacific Costa Rica Margin, ZooKeys 1214, pp. 281-324 : 281-324

Pseudolepetodrilus costaricensis sp. nov.

Fig. 9

Type material examined.

Holotype: Costa Rica • whole organism; ethanol-fixed; Original label: “ Pseudolepetodrilus costaricensis holotype, 1, whole organism, AD 4989 , Costa Rica Margin, Jaco Scar , 9.11785, - 84.8407, 1760 m, from tubeworms. ”; SIO-BIC M 22534 . Paratypes: Costa Rica • 1 specimen; same data as for holotype; Original label: “ Pseudolepetodrilus costaricensis paratype, 1, whole organism, AD 4989 , Costa Rica Margin, Jaco Scar , 9.11785, - 84.8407, 1760 m, from tubeworms. ”; MZCR 10673-01 .

Type locality.

Costa Rica • Costa Rica Margin, Jaco Scar , 9.11785, - 84.8407; hydrocarbon seep; tubeworms; 1,760 m; 4 November 2018; AT 42-03 ALVIN Dive 4989 leg .

Other material examined.

Costa Rica • 4 specimen (s); Costa Rica Margin, Jaco Scar ; 9.11785, - 84.8407; 1,760 m; 4 November 2018; AT 42-03 ALVIN Dive 4989 leg.; Tubeworm; EC 10483 .

Diagnosis.

Pseudolepetodrilus costaricensis sp. nov. can be diagnosed by their unique “ wing-shaped ” first major lateral tooth on their radula and through genetic characterization of the mitochondrial CO 1 gene.

Description.

Shell (Fig. 9 G, H ): Specimens exhibit patelliform shells with very small, truncated whorl at the posterior end of the shell. Holotype measures 3.7 mm in length, 2.8 mm in width, and 1.3 mm in maximum height. Shell roundness (width ÷ length) is ~ 0.75. Sinuous, concentric radial sculpturing present on shell with fine axial striations which intersect the radial sculpture to form very small, raised bumps. The aperture opening is ovate and unornamented. The aperture lip is thick and unornamented. The shell margin is flat. Posterior shell slope is flattened while the anterior shell slope is rounded. Shell apex is posteriorly shifted. Shell is robust with a thick, greenish brown periostracum covering the outer shell and wrapping over the aperture lip.

Soft parts (Fig. 9 I, M ): Soft tissue is light greenish-to-yellowish in color. Mantle margin is thick and irregular and envelopes the body tissue. Three pairs of posterior epipodial tentacles are present. These tentacles descend in length, with the most anterior one being the longest and the most posterior one being the shortest. Posterior tentacles do not extend past the mantle margin. Two broad, fleshy, anterior tentacles are located approximately midway up and on either side of the foot margin. Two cephalic tentacles are present that are fleshy and triangular in shape and thicker than the epipodial tentacles. The mouth has a distinctive Y-shaped opening lacking thickened tissue. Elongated oral lappets are present. The penis originates from below the right cephalic tentacle. Operculum is absent.

Radula (Fig. 9 N, O ): Rhipidoglossate radula. Rachidian teeth have very short shafts and sharp, triangular cusps. The anterior end of each cusp is flat while the pointed ends lack denticles. Rachidian teeth are flanked by one major lateral tooth on each side. Major laterals have broad, wing-shaped cusps that extend higher than the rachidian teeth. The outer edges of these cusps are serrated with ~ 16 short denticles. Three minor laterals follow which have long, sharp, triangular cusps whose outer edge is serrated with short denticles, but whose inner edges are not. The anterior edge of these minor laterals is slightly convex. The fourth, minor lateral teeth also have long, sharp, triangular cusps like the preceding three, but with serrations along both their inner and outer edges. Marginal teeth number ≥ 15 and exhibit rounded, spatulate cusps that are lined with ~ 40 denticles each. Denticles on each marginal tooth are elongated posteriorly and shorten as one moves anteriorly. Marginal cusps are located at the anterior end of a long, thin tooth shaft which connects to the radular ribbon at its base. Morphological transitions between major laterals, minor laterals, and marginal teeth are continuous.

Distribution.

Pseudolepetodrilus costaricensis sp. nov. is confirmed from the hydrocarbon seep sites “ Jaco Scar ” (9.12, - 84.84) at the Pacific Costa Rica Margin. This species was sampled from tubeworms at 1,760 m depth.

Remarks.

Shells of this species notably do not narrow at their anterior ends, similar to L. shannonae ( Warén and Bouchet 2009) . Radulae most closely resembled those of L. guaymasensis . However, unlike this species, the central teeth of P. costaricensis are larger and lack denticles on their cusps. Further, their first lateral teeth have a shape that is distinct from L. guaymasensis , exhibiting an even, sloping outer ridge.

Etymology.

The species name costaricensis refers to the Pacific Costa Rica Margin, the geographic location where this species, and its genus, was first discovered.

Figures

Figure 9. Specimens of Lepetodrilus guaymasensis and Pseudolepetodrilus costaricensis gen. et sp. nov. A – C sequenced L. guaymasensis specimen (GenBank Accession # OQ 644591) from Mound 12, 998 m, AD 4917, 1 June 2017 D – F additional L. guaymasensis specimen from Jaco Scar, 1,811 m, AD 4912, 27 May 2017 G – I Pseudolepetodrilus costaricensis sp. nov. holotype (G – I) and sequenced specimen (J – L) (GenBank Accession # OQ 644586), both from tubeworms, Jaco Scar, 1,760 m, AD 4989, 4 November 2018 M close up view of P. costaricensis epipodial tentacles, with tracing N – P radula morphology representative of this new genus O isolated marginal lateral tooth. Scale bars: 1 mm (A – M); 300 µm (N); 50 µm (O); 30 µm (P).