Pseudamnicola (Pseudamnicola) meloussensis, ALTABA, 2007

Delicado, Diana, Machordom, Annie & Ramos, Marian A., 2014, Vicariant versus dispersal processes in the settlement of Pseudamnicola (Caenogastropoda, Hydrobiidae) in the Mediterranean Balearic Islands, Zoological Journal of the Linnean Society (Zool. J. Linn. Soc.) 171 (1), pp. 38-71 : 57-59

PSEUDAMNICOLA (PSEUDAMNICOLA) MELOUSSENSIS ALTABA, 2007

Type locality

Stream at Macarella Creek, Minorca, Balearic Islands ( Altaba, 2007).

Type material

Holotype ( CRA- -1) and paratypes ( CRA-) in Altaba’s personal collection.

Other populations studied

To assess the localities from Minorca published by Boeters (1988), we returned to the island and found most of them destroyed, mainly as a result of the construction of pipes and irrigation systems. Nevertheless, localities in the south, including the type locality, were conserved and hence, they were the populations examined in this study (see Supporting Information Appendix S 1) .

Specimens examined for morphometry

Shell, anatomical, operculum, and radular measurements (Appendix S 2: Tables S1–S 7) were carried out on male and female specimens collected from a stream at Macarella Creek (type locality), Minorca in December 2007 .

New diagnosis

Shell with a bulging, inflated body whorl occupying around four-fifths of shell length; central radular tooth with five lateral cusps decreasing in size; bursa copulatrix pyriform and bursal duct about 75% of the length of bursa copulatrix; elongate seminal receptacle; black-pigmented renal oviduct with pigment fading from loop to insertion of seminal receptacle; penis shape between triangular and tapered with rounded tip, small patch of pigmentation on distal section and folds over entire inner surface; in most of the cases, with a constriction in the beginning of the distal region; brown-pigmented nervous system with darker cerebral ganglia, and supraoesophageal connective more than eight times longer than suboesophageal one.

Description

Shell ovate-conic, yellowish periostracum with 3.75– 4.50 spire whorls and a height between 2.5 and 3.5 mm ( Fig. 10A–C , Appendix S2: Table S1); body whorl well developed, about four-fifths of shell length; deep suture and convex spire whorls; protoconch with approximately 1.3 whorls; protoconch and nucleus width around 450 and 125 μm, respectively ( Fig. 10E, F ); protoconch microsculpture granulated ( Fig. 10G ); oval aperture with thin outer lip and slightly thicker inner lip; wide umbilicus; edge of peristome straight ( Fig. 10D ).

Operculum with around 2.5 spire whorls and an oval muscle attachment area near the nucleus ( Fig. 11A, B , Appendix S2: Table S2).

Radula length medium (25%) relative to maximum shell dimension ( Fig. 11C , Appendix S2: Table S3); with approximately 50 rows of teeth; central tooth with a large median cusp followed on each side by five small cusps decreasing in size ( Fig. 11D, E ); lateral teeth with three sharp lateral cusps; inner marginal teeth with approximately 18 tapered cusps and outer marginal teeth with around 12 tapered cusps smaller than inner marginal cusps ( Fig. 11F ).

Pigmentation and anatomy

Head brown pigmented, less pigmentation on tentacles and neck; lack of pigmentation on edge of snout and ocular area ( Fig. 12F ); foot intermediate in size and with dark brown pigment on its dorsal side. Ctenidium well developed with 18–20 gill filaments longer than wide, occupying the middle section of pallial cavity; osphradium in opposite middle region of ctenidium ( Fig. 12C , Appendix S2: Table S4). Stomach slightly longer than wide (Appendix S2: Table S4); oesophagus and intestine lack pigmentation ( Fig. 12E ); rectum S-shaped in pallial cavity.

Female genitalia with capsule gland longer than albumen gland ( Fig. 12G , Appendix S2: Table S5); bursa copulatrix pyriform and bursal duct about 75% of the length of bursa copulatrix; elongate seminal receptacle without duct, situated on renal oviduct above the insertion of bursal duct; black-pigmented renal oviduct, pigment fading from loop to insertion of seminal receptacle; renal oviduct lies over bursa copulatrix making one or two loops ( Fig. 12H ).

Male genitalia with a bean-shaped prostate gland approximately four times longer than wide ( Fig. 12D , Appendix S2: Table S6); penis shape between triangular and tapered with rounded tip and folds over entire surface, folds thicker near the tip; it is attached to the central area of the head; in most specimens, there is a constriction at the beginning of the distal region; small patch of pigmentation on distal section of penis ( Fig. 12F ); penial duct runs straight (although wavy in some specimens), near the outer edge of the penis.

Nervous system with darker cerebral ganglia than connectives and commissures; cerebral ganglia approximately equal in size; supraoesophageal con- nective eight times longer than suboesophageal one ( Fig. 12B , Appendix S2: Table S7); RPG ratio 0.60 (elongate); oesophagus runs straight underneath nervous system ( Fig. 12A ).

Remarks

The type locality presents two shell morphotypes, one that is smaller with a more rounded aperture ( Fig. 10A ) and the other that has a larger last body whorl and wider umbilicus and aperture ( Fig. 10C ). The first morphotype is similar to the one in the original description ( Altaba, 2007). However, both morphotypes from S. Juan de Carbonell, Minorca were figured by Boeters (1988: figs 53, 54). Anatomically, only minor differences are found between the morphotypes, mainly in penis features: the penis of the second morphotype is more slender and tapered. The greatest genetic distance amongst individuals of this population is 2% for COI, which is insufficient to consider them different species.

The general shapes of the shell and penis for the other examined localities are a smaller shell and less tapered penis. However, the penis tip is less pointed than that of Boeters’ descriptions for specimens from Minorca ( Boeters, 1988: fig. 77). The female genitalia are similar to figure 84 of Boeters (1988). There is low anatomical variability within and amongst populations; however, a certain level of genetic divergence exists amongst them. Specimens collected from Ses Penyes are genetically the most divergent of the Minorcan specimens (the greatest genetic distance observed was 2.58% for COI). This locality is geographically the most isolated compared to the other localities, which may decrease gene flow.

Boeters (1988) assigned some populations from Minorca to P. (P.) subproducta , claiming that some intraspecific variability existed for this group. However, despite sharing shell dimensions and the number of spire whorls, we conclude that the studied populations from Minorca belong to a different species group, namely P. (P.) meloussensis . This species differs from P. (P.) subproducta in a number of characters as follows: (1) longer stomach style sac; (2) larger capsule gland and bursa copulatrix; (3) longer penis; (4) elongate nervous system ( RPG ratio of 0.60); and (5) genetically, having divergences of 5.6% for COI, 1.5% for 16S, and 1.1% for 28S.

Figures

Figure 10. Shells of Pseudamnicola (Pseudamnicola) meloussensis from a stream at Macarella Creek, Minorca. A–D, frontal and lateral views of the observed morphotypes. E–G, protoconch and details of protoconch microsculpture. Scale bar: 1 mm.

Figure 11. Operculum and radula of Pseudamnicola (Pseudamnicola) meloussensis from a stream at Macarella Creek, Minorca. A, internal side of the operculum. B, external side of the operculum. C, radula. D, rows of teeth of the radula. E, central teeth. F, outer marginal teeth.

Figure 12. Anatomy of Pseudamnicola (Pseudamnicola) meloussensis from a stream at Macarella Creek, Minorca. A, B, partial nervous system. C, ctenidium and osphradium. D, prostate gland. E, stomach. F, head and penis of a male. G, female genitalia. H, bursa copulatrix and seminal receptacle.