Mercuria felixi Miller, García-Guerrero & Ramos, 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 : 38-42

Mercuria felixi Miller, García-Guerrero & Ramos sp. nov.

urn:lsid:zoobank.org:act:798D1589-DD36-4893-9FEB-8BF7026FF008

Figs 23–25 ; Supp. file 2: Tables S14–18

Diagnosis

Shell ovate-conic; aperture obliquely ovate; protoconch microsculpture granulated; periostracum dark brown to blackish; central radular tooth formula 3(4)-C-(4)3/1-1; female genitalia with bursa copulatrix pyriform to elongate, ca 3 times as long as wide; seminal receptacle elongate; penis darkly pigmented; penial appendix ovate, darkly pigmented at the junction with the penis, about the same length or slightly shorter than the distal end of the penis and medially positioned on the inner edge of the penis; nervous system pigmented, elongate (mean RPG ratio = 0.60). Cerebral ganglia are approximately equal in size.

Etymology

Named after Félix Ríos Jiménez, who provided us with valuable samples of the new species.

Type material

Holotype SPAIN • sex unknown (dry preserved); Cádiz, stream in Canuto de la Tala ; MNCN 15.05/200176H .

Paratypes SPAIN – Cádiz • 27 specs (preserved in ethanol 80%); same collection data as for holotype; MNCN 15.05/94754 • 22 specs (preserved in ethanol 80%); same collection data as for holotype; MNCN 15.05/94756 • 1 spec. (dry preserved); same collection data as for holotype; MZB 2021-2798 • 2 specs (dry preserved); same collection data as for holotype; NHMW 113528 • 1 spec. (dry preserved); same collection data as for holotype; RMNH.MOL.507926 • 2 specs (dry preserved); same collection data as for holotype; JPM-586 • 1 spec. (dry preserved); same collection data as for holotype; MCP.

Additional material examined

SPAIN – Cádiz • 30 specs; stream in Canuto del Zapato ; MNCN 15.05/94755 , MNCN 15.05/94757 .

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

Type locality

Stream in Canuto de la Tala, Cádiz, Spain. 36.477025° N, 5.592611° W, 673.97 m a.s.l.

Description

MEASUREMENTS. Holotype: SL = 3.78 mm, SW = 2.87 mm, SL/SW = 1.31, AH = 1.77 mm, SL-LBW = 0.90 mm, WBW = 2.25 mm, AL = 1.75 mm, AW = 1.36 mm, WPW = 1.33 mm, WAW = 0.60 mm.

SHELL. Ovate-conic, whorls 4–5, height 2.4–3.8 mm, width 2–2.9 mm ( Fig. 23A–F ; Supp. file 2: Table S14); periostracum dark brown to blackish; protoconch of 1.5 whorls, ca 270 µm wide, nucleus ca 125 µm wide ( Fig. 24A ); protoconch microsculpture granulated ( Fig. 24B–C ). Teleoconch whorls slightly convex, separated by a deep suture; body whorl large, convex, occupying more than two-thirds of the total shell length; aperture obliquely broad ovate, complete; inner lip thicker than outer lip; outer margin straight, inner lip touching the body whorl; umbilicus narrow, not covered by the inner lip ( Fig. 23A, C–F ).

OPERCULUM. As for the genus, orange to brown, sometimes yellowish, with about two whorls; muscle attachment oval, located near the nucleus ( Fig. 23G–H ).

RADULA. Length intermediate, ca 700 µm long (35% of total shell length), containing about 60 rows of teeth. Central tooth formula 3(4)-C-(4)3/1-1, central cusp V shaped, cutting edge slightly concave ( Fig. 24D ). Lateral tooth formula 3-C-3, central cusp V shaped and slightly longer than the central tooth one. Inner marginal teeth with 15–18 cusps; outer marginal teeth with 23–27 cusps ( Fig. 24E–F ). Radular data were collected from specimens from the type locality.

PIGMENTATION AND ANATOMY. Animal weakly pigmented ( Fig. 25E ); head and tentacles unpigmented to weakly pigmented; eye lobe unpigmented; snout and neck weakly pigmented; snout longer than wide, approximately parallel-sided, with medium distal lobation. Ctenidium occupying almost the total length of the pallial cavity; 21–25 gill filaments; filaments broad, triangular, fused at the base by an epithelium ( Fig. 25F ). Osphradium elongate, more than 3 times as long as wide, positioned opposite middle of ctenidium. 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 then continuing on as a straight rectum ( Fig. 25G ).

MALE GENITALIA. Prostate gland bean-shaped, about 3 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. 25C ). Penis darkly pigmented, gradually tapering, attached to the neck behind the right eye; penial appendix ovate, darkly pigmented at the junction with the penis, about the same length or slightly shorter than the distal end of the penis and medially positioned on the inner edge of the penis ( Fig. 25D–E ).

FEMALE GENITALIA. Glandular oviduct 3 times as long as wide; albumen gland ca 2 times as long as capsule gland; bursa copulatrix pyriform to elongate, ca 3 times as long as wide ( Fig. 25A–B ; Supp. file 2: Table S17); bursal duct shorter than bursa copulatrix; renal oviduct unpigmented, highly coiled with three loops; seminal receptacle elongate, with a short duct, positioned on the distal part of the renal oviduct just above the junction with the bursal duct (position SR1).

NERVOUS SYSTEM. Pigmented, elongate (mean RPG ratio = 0.60; see Supp. file 2: Table S15); cerebral ganglia approximately equal in size, pleuro-supraoesophageal connective ca 11 times as long as pleuro-suboesophageal one ( Fig. 25H ).

Ecology and distribution

This species was collected from two streams in southern Spain: the stream in Canuto de la Tala (type locality) and the stream in Canuto del Zapato. The ecology of the species is not well known. The species inhabits streams of very clear running waters with relatively low conductivities (75–292 mS/cm 2). The specimens collected from the stream in Canuto del Zapato were found in very low abundance. Co-occurring species are Ancylus fluviatilis and Galba truncatula in low abundance and Pisidium sp. in high abundance (Félix Ríos Jiménez pers. com.).

Remarks

Mercuria felixi sp. nov. differs from the phylogenetically closely related species M. tensiftensis and M. balearica by having a narrower aperture (wider in M. balearica ); a more globose shell (high-spired in M. tensiftensis ); a granulated protoconch microsculpture (grooved in M. tensiftensis ); an ovate, pigmented penial appendix that is about the same length or slightly shorter than the distal end of the penis (rounded, unpigmented and shorter than the distal end of the penis in M. balearica and darkly pigmented and shorter than the distal end of the penis in M. tensiftensis ); a thin, filiform, pigmented distal end of the penis (broad, triangular, and strongly and darkly pigmented in M. balearica , and triangular and pigmented in M. tensiftensis ); a prostate gland that is 3 times as long as wide (2 times as long as wide in M. tensiftensis and M. balearica ) and a smaller radular ribbon. The species also has one more cusp on the central teeth than in M. tensiftensis .

The shell shape of M. felixi sp. nov. resembles that of M. carrillorum sp. nov. and M. tachoensis ; however, our PCA ( Fig. 3 ) showed that M. felixi can be differentiated from the rest of the Mercuria species. The penile morphology of M. felixi further differentiates it from the Iberian congeners: it has a very thin, pigmented penial appendix and a long, filiform and pigmented distal penis.

According to DNA-sequence analyses ( Miller et al. 2022), this species forms a clade with M. balearica (5.3% of mean COI divergence) and M. tensiftensis (5.1% of mean COI divergence). It is most distantly related to M. midarensis and M. saharica , diverging from these species by 8% and 8.6%, respectively.

Figures

Fig. 23. Shells and operculum of Mercuria felixi Miller, García-Guerrero & Ramos sp. nov. from the stream in Camuto de la Tala, Cádiz, Spain. A–B. Holotype (MNCN 15.05/200176H), frontal and lateral views. C–H. Paratypes (MNCN 15.05/94754). G. Operculum, inner side. H. Operculum, outer side.

Fig. 24. Protoconch and radula of Mercuria felixi Miller, García-Guerrero & Ramos sp. nov. from the stream in Canuto de la Tala, Cádiz, Spain. A. Protoconch. B. Details of the protoconch. C. Protoconch microsculpture. D. Overview of radular teeth rows. E–F. Detailed view of the inner and outer marginal teeth, respectively.

Fig. 25. Anatomy of Mercuria felixi Miller, García-Guerrero & Ramos sp. nov. from the stream in Canuto de la Tala, Cádiz, Spain. A–B. Female genitalia. C. Prostate gland. D. Penis. E. Animal and penis. F. Ctenidium and osphradium. G. Stomach. H. Perioesophageal ring.

Fig. 3. Principal components analysis plot for species of Mercuria Boeters, 1971 based on 21 coordinates (9 landmarks and 12 semilandmarks). Each dot on the plot represents the consensus of the shape of each of the sampled populations. Warp grid deformations (TPS) show expansion (in red colour) and contraction (in blue) of the shell shape.