Biologi & Ekologieng
Ecology and distribution Most of the examined specimens were found in waters with very high conductivities (592 – 28 900 µS / cm, average 6364 µS / cm). These localities are affected by the Keuper facies, Mesozoic evaporitic deposits that contain high levels of NaCl and CaSO 4, among others, that dissolve into the superficial waters inhabited by the species. Specimens were most often found in the mud among the lower parts of the shoreline vegetation. Co-occurring gastropod species are Melanopsis spp., Theodoxus spp., Belgrandia gibba (Draparnaud, 1805), Hydrobia acuta (Draparnaud, 1805), Pseudamnicola subproductus (Paladilhe, 1869), Diegus gasulli (Boeters, 1981) and Potamopyrgus antipodarum (Gray, 1843). The species is distributed in springs, streams, small rivers, coastal lakes (étangs) and ditches near the Mediterranean coast of southern France, the Iberian Peninsula and North Africa (Boulaassafer et al. 2018) and on the island of Majorca (Fig. 1). It has also been reported near the Atlantic coast of the Iberian Peninsula, northern France, Apennine peninsula, Great Britain and various Atlantic islands (Wollaston 1878; Kerney 1999; Bodon et al. 2005; Kadolsky 2011). We were unable to confirm previous records of the species for Great Britain (Baker et al. 1999; Abrehart & Forster 2012), the Azores islands (Wollaston 1878) and North Africa (Taybi et al. 2017). Some of these citations may have been incorrectly attributed to M. similis instead of M. tachoensis, which is found in, at least, Great Britain (see below).
Sumber: Morphology and taxonomic assessment of eight genetic clades of Mercuria Boeters, 1971 (Caenogastropoda, Hydrobiidae), with the description of five new species
Deskripsieng
Description SHELL. Ovate-conic, whorls 4 – 5, height 3.5 – 5.7 mm, width 1.5 – 3.3 mm (Fig. 4 A – O; Supp. file 2: Table S 2); periostracum whitish to grey; protoconch of 1.5 whorls, ca 400 µm wide, nucleus ca 200 µm wide (Fig. 5 A – B); protoconch microsculpture granulated (Fig. 5 C); teleoconch whorls very 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 touching the shell wall; umbilicus narrow, not covered by the inner lip. OPERCULUM. As for the genus, orange to brown, sometimes yellowish, about two whorls; muscle attachment oval, located near the nucleus (Fig. 4 P – Q). RADULA. Length intermediate, ca 800 µm long (35 % of total shell length), containing about 65 rows of teeth. Central tooth formula (2) 3 - C- 3 (2) / 1 - 1, central cusp V shaped, cutting edge slightly concave (Fig. 5 D – F). Lateral tooth formula (3) 2 - C- 2 (3), central cusp V shaped and slightly longer than the central tooth one. Inner marginal teeth with 11 – 15 cusps (Fig. 5 E); outer marginal teeth with 12 – 25 cusps (Fig. 5 F). Radular data were collected from the following specimens: MNCN 15.05 / 94760 – Spring Pilar de los Playeros, Prado del Rey, Cádiz, Spain; MNCN 15.05 / 94767 – Las Negras ravine, Almería, Spain; MNCN 15.05 / 94768 – Cordovilla Saltings, Albacete, Spain; MNCN 15.05 / 94776 – Fonte Dame Spring, Salses-le-Château, Aude, France; MNCN 15.05 / 94777 – Estramar Spring, Salses-le-Château, Aude, France; MNCN 15.05 / 94778 – pond in La Palme, Aude, France; MNCN 15.05 / 94791 – La Foux-de-Draguignan Spring, France and 15.05 / 94804 – Font de Son Sant Joan, Muro, Majorca, Spain. PIGMENTATION AND ANATOMY. Animal darkly pigmented, although unpigmented specimens were also found (Fig. 4 E); head and tentacles black, pigmentation lighter on eye lobes, snout and neck; snout about as long as wide, approximately parallel-sided, with medium distal lobation (Fig. 7 F). Ctenidium occupying almost the total length of the pallial cavity; 22 – 27 gill filaments; filaments broad, triangular, fused at the base by an epithelium (Fig. 6 E). Pallial tentacle present. Osphradium elongate, more than 3 times as long as wide (Supp. file 2: Table S 3), positioned opposite middle of ctenidium. Stomach almost as long as wide with two chambers almost equal in size; style sac longer than wide (Supp. file 2: Table S 3), with the unpigmented intestine surrounding its distal end before continuing on as a straight rectum (Fig. 6 F). FEMALE GENITALIA. Glandular oviduct 2.5 times as long as wide; albumen gland longer than capsule gland (Fig. 6 A – D; Supp. file 2: Table S 4); bursa copulatrix pyriform to elongate, ca 3 times as long as wide; bursal duct shorter than bursa copulatrix; renal oviduct unpigmented, highly coiled with three loops; seminal receptacle elongate, with a short duct, positioned at the distal end of the renal oviduct just above the junction with the bursal duct (Fig. 6 A – D). MALE GENITALIA. Penis darkly pigmented, gradually tapering, attached to the neck behind the right eye; penial appendix longer (Fig. 7 A – C) or shorter (Fig. 7 D – F) than the distal end of the penis, triangular, strongly pigmented at the junction with the penis, pigmentation gradually weakens from the junction to the middle of the penial appendix where it is very weak. Penial appendix base narrow, medially positioned on the inner edge of the penis. Prostate gland bean-shaped, about 2 times as long as wide, connected by the posterior vas deferens to a convoluted seminal vesicle and the testis (Fig. 7 G – H; Supp. file 2: Table S 5). NERVOUS SYSTEM. Pigmented, elongate (mean RPG ratio = 0.63; Supp. file 2: Table S 15); cerebral ganglia approximately equal in size; pleuro-supraoesophageal connective ca 9 times as long as pleuro-suboesophageal one (Fig. 6 G).
Sumber: Morphology and taxonomic assessment of eight genetic clades of Mercuria Boeters, 1971 (Caenogastropoda, Hydrobiidae), with the description of five new species
