Mercuria lupiaensis Miller & Delicado, 2023

Miller, Jonathan P., Delicado, Diana, García-Guerrero, Fernando, Khalloufi, Noureddine & Ramos, Marian A., 2023, Morphology and taxonomic assessment of eight genetic clades of Mercuria Boeters, 1971 (Caenogastropoda, Hydrobiidae), with the description of five new species, European Journal of Taxonomy 866 (1), pp. 1-63 : 42-47

Mercuria lupiaensis Miller & Delicado sp. nov.

urn:lsid:zoobank.org:act:A3B189DF-8A84-46B5-82BD-A083F46F8CF9

Figs 26–28 ; Supp. file 2: Tables S14–S18

Diagnosis

Shell ovate-conic; aperture obliquely ovate; periostracum whitish to pale grey; central radular tooth formula 3-C-3/1-1; female genitalia with bursa copulatrix pyriform to elongate, ca 2 times as long as wide; seminal receptacle pyriform; penis darkly pigmented; penial appendix unpigmented, ovate, smaller than the distal end of the penis and medially positioned on the inner edge of the penis; nervous system pigmented, elongate (mean RPG ratio = 0.53); cerebral ganglia approximately equal in size, with small black spots.

Etymology

The specific epithet ‘ lupiaensis ’ refers to Lupia, the name of the city of Lecce during the time of the ancient Roman empire.

Type material

Holotype ITALY • sex unknown (preserved in ethanol 80%); Lecce, Frigole, Giammateo Creek ; MNCN 15.05/200123H .

Paratypes ITALY • 4 specs (preserved in ethanol 80%); same collection data as for holotype; MNCN 15.05/200123P • 13 specs (preserved in ethanol 80%, 7 dissected and 2 processed for DNA sequencing); same collection data as for holotype; UGSB 8015 .

Additional material examined

ITALY • 9 specs; Apulia, Nardò, San Isidoro, Palude del Capitano Pond ; UGSB 16236 • 7 specs; Apulia, Porto Cesareo, Ionian Coast , spring in Torre Castiglione ; UGSB 16237 .

Additional locality information provided in Supp. file 1: Table S1.

Type locality

Giammateo Creek, Frigole, Lecce, Italy. 44.9436° N, 12.0213° E.

Description

MEASUREMENTS. Holotype: SL = 3.73 mm, SW = 2.95 mm, SL/SW = 1.26, AH = 1.92 mm, SL-LBW = 0.94 mm, WBW = 2.27 mm, AL = 1.96 mm, AW = 1.32 mm, WPW = 1.29 mm, WAW = 0.63 mm.

SHELL. Ovate-conic, whorls 4–5, height 3.10–3.75 mm, width 2.50–3.00 mm ( Fig. 26A–F ; Supp. file 2: Table S14); periostracum whitish to pale grey; protoconch of 1.5 whorls, ca 300 µm wide, nucleus ca 150 µm wide; teleoconch whorls slightly convex, separated by a deep suture; body whorl large, convex, occupying about two-thirds of the total shell length; aperture obliquely broad ovate, complete; inner lip thicker than outer lip; aperture margin straight, inner lip attached to the body whorl; umbilicus narrow, not covered by the inner lip ( Fig. 26A, C–F ).

OPERCULUM. As for the genus, orange to brown, about two whorls; muscle attachment oval, located near the nucleus ( Fig. 26G–H ).

RADULA. Length intermediate, ca 800 µm long (35% of total shell length), containing about 60 rows of teeth ( Fig 27A ). Central tooth formula 3-C-3/1-1, central cusp V shaped, cutting edge slightly concave ( Fig. 27B ). Lateral tooth formula 3-C-3, central cusp V shaped and slightly longer than the central tooth one ( Fig. 27C ). Inner marginal teeth with 14–17 cusps; outer marginal teeth with 22–25 cusps ( Fig. 27D ). Radular data were collected from specimens from Giammateo Creek, Frigole, Lecce (UGSB 8015); Palude del Capitano Pond, San Isidoro, Ionian coast, Nardó, Apulia (UGSB 16236) and a spring in Torre Castiglione, Ionian Coast, Porto Cesareo, Apulia (UGSB 16237).

PIGMENTATION AND ANATOMY. Animal darkly pigmented ( Fig. 28E, I ); head and tentacles black pigmented, pigmentation lighter on eye lobes, snout and neck; snout about as long as wide, approximately parallel-sided, with medium distal lobation. Ctenidium occupying almost the total length of the pallial cavity; 23–27 gill filaments; filaments broad, triangular, fused at the base by an epithelium ( Fig. 28G ). Stomach almost as long as wide with two chambers almost equal in size (Supp. file 2: Table S16); style sac longer than wide, with the unpigmented intestine surrounding its distal part and continuing on as a straight rectum ( Fig. 28H ).

MALE GENITALIA. Prostate gland bean-shaped, about 2 times as long as wide (Supp. file 2: Table S18), connected by the posterior vas deferens to a convoluted seminal vesicle and the testis ( Fig. 28F ). Penis darkly pigmented, gradually tapering, attached to the central area of the neck; penial appendix unpigmented or slightly pigmented at the junction with the distal end of the penis. Penial appendix ovate, smaller than the penis, base narrow, medially positioned on the inner edge of the penis ( Fig. 28C–E ).

FEMALE GENITALIA. Glandular oviduct 2.5 times as long as wide; albumen gland and capsule gland about the same size ( Fig. 28A–B ); bursa copulatrix elongate, ca 2 times as long as wide (Supp. file 2: Table S17); bursal duct shorter than bursa copulatrix; renal oviduct unpigmented, highly coiled with three loops; seminal receptacle pyriform, with a short duct, positioned on the distal part of the renal oviduct just above the junction with the bursal duct ( Fig. 28B ).

NERVOUS SYSTEM. Pigmented, elongate (mean RPG ratio = 0.53; see Supp. file 2: Table S15); cerebral ganglia approximately equal in size ( Fig. 28I ).

Ecology and distribution

The species is only known from the three nearby localities in the Salento Peninsula in the region of Apulia, Italy. The ecology of the species is not well known. The species was found in very clear running waters, close to the coastal margins. Co-occurring species are Pseudamnicola conovula ( Frauenfeld, 1863) , Eupaludestrina stagnorum (Gmelin, 1791) and Bithynia leachii (Sheppard, 1823) .

Remarks

Mercuria lupiaensis sp. nov. now represents the easternmost species of the genus and potentially the second species reported in the Apennine Peninsula. The species M. similis has been documented from the Sale Basin ( Bodon et al. 2005; Cianfanelli & Bodon 2017), the first species of Mercuria described from the Apennine Peninsula. Despite that the new species and M. similis have a similar shell shape; they can be easily distinguished by differences in the penial appendix: in M. similis , it is large, triangular and highly pigmented, whereas in M. lupiaensis , it is small, sometimes very small, ovate and slightly pigmented or unpigmented. In the new species, the albumen and capsule glands are about the same size, whereas, in M. similis , the albumen gland is longer than the capsule gland. They also present differences in the bursa copulatrix: elongate and about 2 times as long as wide in M. lupiaensis and pyriform to elongate and 3 times as long as wide in M. similis .

Mercuria lupiaensis sp. nov. can be further distinguished from the phylogenetically closely related species M. veronicae sp. nov. by its smaller size, lighter dorsal pigmentation, similarly sized capsule and albumen glands (albumen gland longer than capsule gland in M. veronicae ), a penial appendix that is shorter than the distal end of the penis and a smaller number of cusps on the central teeth.

The sequence divergence estimates of COI showed that the species is most closely related to M. veronicae sp. nov. (mean divergence of 3.9%) and most distantly to M. midarensis (with a mean divergence of 9.3%) ( Miller et al. 2022).

Figures

Fig. 26. Shells and operculum of Mercuria lupiaensis Miller & Delicado sp. nov. A–B. Holotype (MNCN 15.05/200123H), frontal and lateral views. C–D. Paratypes (MNCN 15.05/200123P). C–D, G–H. Specimens from Giammateo Creek, Frigole, Lecce. E. Specimen from the spring in Torre Castiglione, Ionian Coast, Porto Cesareo, Apulia (UGSB 16237). F. Specimen from Palude del Capitano Pond, San Isidoro, Ionian coast, Nardò, Apulia (UGSB 16236). G. Operculum, inner side.H. Operculum, outer side.

Fig. 27. Radula of the Mercuria lupiaensis Miller & Delicado sp. nov. from Giammateo Creek, Frigole, Lecce. A. General view of the radular ribbon. B. Overview of radular teeth rows. C. Detailed view of the lateral and inner marginal teeth. D. Detailed view of the outer marginal teeth.

Fig. 28. Anatomy of Mercuria lupiaensis Miller & Delicado sp. nov. from Giammateo Creek, Frigole, Lecce. A–B. Female genitalia indicating the seminal receptacle (Sr). C–D. Penis. E. Head of a male. F. Prostate gland. G. Ctenidium and osphradium. H. Stomach. I. Head with perioesophageal ring attached.