Pseudamnicola megastomus Delicado, Khalloufi & Hauffe, 2025

Pseudamnicola megastomus Delicado, Khalloufi & Hauffe sp. nov.

( Figs 11 View Figure 11 , 12 View Figure 12 )

Pseudamnicola sp. 2 — Delicado et al. 2015 [in part] Pseudamnicola sp. 2 — Delicado et al. 2018

Pseudamnicola sp. 2 — Boulaassafer et al. 2020

ZooBank registration: urn:lsid:zoobank.org:act:0DD397BA-5997-4FF8-8E42-A3A4EB495D83

Etymology

From Greek megastome, referring to the large shell aperture of this species.

Type material

Holotype ( MNCN 15.05 About MNCN /200501H) and ~ 30 paratypes ( MNCN 15.05 About MNCN /200501P) in the MNCN collection. Type locality: Wedi El Garâa Stream, Bizerte, Tunisia.

Material studied

Wedi El Garâa Stream , Bizerte, Tunisia, 37.2426°N, 9.7185°E, leg. N.K. and D.D., May 2009, MNCN 15.05 About MNCN /200501 (70% ethanol). GoogleMaps A well in the Ennkhilet region, north of Ichkeul, Tunisia, 37.2055°N, 9.6677°E, leg. N.K. and D.D., May 2009, MNCN 15.05 About MNCN /95107 (70% ethanol) GoogleMaps .

Diagnosis

Shell ovate-conic, with a relatively wide aperture (AW/AL ratio>.75); protoconch microsculpture pitted; central radular tooth formula (4)3-C-3(4)/1-1; bursa copulatrix large, pyriform, with a duct slightly longer than bursal length; SR1 elongate, with a short duct; penis large, gradually tapering, unpigmented, with many folds over the entire surface and a moderately wide base; nervous system darkly pigmented, elongate (mean RPG ratio =.52).

Description

Shell ovate-conic, whorls 4–4.5, height 3–4 mm ( Fig. 11A, C, D View Figure 11 ; Supporting Information, Table S3). Periostracum yellowish. Protoconch ~450 µm wide, whorls 1.5; nucleus ~120 µm wide; protoconch microsculpture pitted ( Fig. 11F View Figure 11 ). Teleoconch whorls moderately convex, with deep sutures; body whorl large, occupying about three-quarters of total shell length. Aperture almost as wide as long, slightly oval; inner lip thicker than outer lip; peristome margin simple, straight ( Fig. 11B View Figure 11 ). Umbilicus narrow, not covered by the inner lip. Holotype: SL = 3.75 mm, SW = 2.75 mm, AL = 2.04 mm, and AW = 1.62 mm.

Operculum oval, brownish, about two and a half whorls; muscle attachment area oval and located near the nucleus ( Fig. 11E View Figure 11 ).

Radular length intermediate, ~750 µm (~25% of total shell length), with ~55 rows of teeth ( Fig. 11G View Figure 11 ). Central tooth formula (4)3-C-3(4)/1-1 ( Fig. 11H View Figure 11 ); basal tongue V-shaped, length about equal to lateral margin. Lateral tooth formula 2-C-2 (rarely with three lateral cusps). Inner marginal teeth having 16–17 tapered cusps, shortening towards the base. Outer marginal teeth with ~22 sharp cusps ( Fig. 11I View Figure 11 ).

Animal black-pigmented except for neck and tentacles ( Fig. 12F View Figure 12 ). Snout as long as wide, with medium distal lobation; foot size intermediate, with dorsal pigmentation. Ctenidium with 16–19 well-developed gill filaments, occupying ~50% of pallial cavity length and posteriorly positioned. Osphradium of intermediate width and opposite middle of ctenidium ( Fig. 12A View Figure 12 ). Stomach as long as wide, with two chambers almost equal in size and a medium-sized posterior caecum; style sac longer than wide, surrounded by an unpigmented intestine ( Fig. 12B View Figure 12 ; Supporting Information, Table S4). Nervous system elongate (mean RPG ratio =.52), darkly pigmented, darker on ganglia than on connectives and commissures; cerebral ganglia approximately equal in size ( Fig. 12C View Figure 12 ).

Female glandular oviduct approximately three times as long as wide. Albumen gland shorter than capsule gland. Bursa copulatrix pyriform, longer than wide. Bursal duct longer than bursal length. Renal oviduct black-pigmented until the insertion of seminal receptacle or the area above, relatively straight. Seminal receptacle elongate, with a short duct, joining renal oviduct at the insertion point with bursal duct ( Fig. 12D, E View Figure 12 ; Supporting Information, Table S5).

Male genitalia with a prostate gland approximately three times as long as wide, bean-shaped; seminal duct entering the middle-posterior region; pallial vas deferens emerging close to its anterior edge ( Fig. 12H View Figure 12 ). Penis longer than head, gradually tapering, unpigmented, with many folds over the entire surface ( Fig. 12F, G View Figure 12 ; Supporting Information, Table S6); base narrower than central area of penis; attached well behind the right eye; penial duct narrow, curved, coursing close to outer edge.

Habitat

Known from two different habitat types in southern Bizerte. The species was found in the muddy bottom of a stream (Wedi El Garâa) near Bizerte and attached to the walls of a well in the Ennkhilet region north of Ichkeul. In the first locality, aquatic plants are sparse, and the water temperature and conductivity are 22°C and 2.6–2.9 mS, respectively. In the second locality, aquatic plants ( Ranunculus sp. and Lemna minor Linn. ) and filamentous algae ( Spirogyra sp. ) are dense. The temperature and conductivity of the water are high (24°C and 1.6–2.4 mS, respectively). Snails were found in low abundance at the two localities. Co-occurring mollusc species are Galba truncatula , Physella acuta , Gyraulus parvus (Say, 1817) , and Pisidium sp.

Remarks

Pseudamnicola megastomus View in CoL has an unusually large shell aperture, comparable to that of Pseudamnicola algeriensis Glöer, Bouzid & Boeters, 2010 View in CoL ( Glöer et al. 2010: fig. 14). However, specimens of P. megastomus View in CoL are slightly smaller and have a narrower last body whorl and a wider aperture than in the latter species. Its shell morphology is similar to that of a paratype of Pseudamnicola ghamizii Glöer, Bouzid & Boeters, 2010 View in CoL ( Glöer et al. 2010: fig. 39), but differs in its higher shell and larger aperture. The species was recorded from north-eastern Tunisia, where another accepted species of Pseudamnicola View in CoL , P. meluzzii View in CoL , is distributed. The former can be distinguished easily by having a larger shell, a wider aperture, fewer cusps on the lateral and central radular teeth, and a longer bursa copulatrix. The features of the penis of both species are very similar. The newly discovered species in north-western Tunisia, P. araujoi View in CoL , differs from P. megastomus View in CoL in having a smaller and more globose shell, a shorter penis, and a less concentrated nervous system. Pseudamnicola megastomus View in CoL and P. conovula View in CoL were depicted as closely related species in previous studies ( Delicado et al. 2015, 2018, Boulaassafer et al. 2020) and by all our phylogenetic analyses ( Fig. 2 View Figure 2 ; Supporting Information, Figs S4–S View Figure 4 6 View Figure 6 ). However, this relationship has always

Gastropod species delimitation • 23 been poorly supported. A population of P. conovula View in CoL living at Toute Stream (Bizerte Region) and its conspecific populations differ from P. megastomus View in CoL according to their different shell features and female reproductive anatomy. The average sequence divergence among these four species was 2.5%–7.4% for COI.