Phreatodrobia embossa Perez, 2025

Phreatodrobia embossa Perez, 2025 sp. nov.

Figs 5 D, H View Figure 5 , 6 C View Figure 6 , 7 C View Figure 7

Diagnosis.

Shell minute, glassy, clear, ovately conic. Elevated protoconch and teleoconch with regular rows of spirally arranged nodules. Broadly ovate aperture. Penis simple, tapering, with little muscular ridging.

Type locality.

USA, Texas, Terrell County, Caroline Springs hyporheic zone (30.46622, - 101.79429).

Material examined.

Holotype and Paratypes – Terrell County • Caroline Springs near Sheffield, 2 nd pool of raceway , hyporheic sample, collected by K. E. Perez, H. Glover, P. Sprouse (30.46622, - 101.79429), 7 December 2020 ( ANSP 506746 About ANSP , ANSP 506747 About ANSP ) GoogleMaps .

Description.

Shell minute, clear, glassy, with regular rows of sculpture, ovately to globosely conic with rounded whorl outlines and impressed sutures (Figs 5 D & H View Figure 5 ). First whorl of protoconch elevated, separated from the whorls that follow. Protoconch sculpture is a uniform network of raised wrinkles giving an irregular malleated appearance. Teleoconch sculpture is distinctive and includes regularly spaced (~ 10 µm apart), spirally arranged rows of raised nodules (Fig. 5 H View Figure 5 ) and transverse growth lines. Nodules resemble irregularly sized knots on a string. Aperture broadly ovate, usually appressed to body whorl at upper parietal corner. Outer margin of aperture straight, slightly thickened and reflected, stronger at apex and base. Outer lip straight, simple, slightly prosocline. Umbilicus deep and open. Average shell measurements for adults (n = 8): shell height = 1.07 mm (SD = 0.09), shell width = 0.80 mm (SD = 0.08), aperture height = 0.53 mm (SD = 0.06), aperture width = 0.44 mm (SD = 0.04), number of whorls = 4.75 (SD = 0.38). Operculum clear, thin, pliable. Shape ellipsoidal, nucleus submarginal, strongly convex. Growth lines not distinct or frilled. Muscle attachment scar oval, nuclear area with raised thickening inside.

Tissue unpigmented, tentacles longer than snout, unpigmented, no visible eyes, snout short, deeply lobate, foot short with no lateral wings. Ctenidium across pallial roof, ~ 10 elongate, low-triangular lobes, filling 50 % of pallial roof. Osphradium large, ovate, near posterior end of the ctenidium. Intestine winds in U shape through pallial cavity, filled with small round fecal pellets, rectum ends near edge of the mantle. Esophagus muscular, enters stomach below, smaller anterior chamber and larger posterior chamber. Penis small, attached above right tentacle, lightly furrowed along narrow, muscular base, narrowing to a short neck about half the width of the base before widening to a lobe on the distal 1 / 3, followed by a tapering tip. Female reproductive anatomy and radula not described due to a lack of material.

Taxonomic remarks.

Phreatodrobia embossa is placed sister to Phreatodrobia in the phylogenetic analyses of both genes with strong support, and in a clade with Phreatodrobia and Antrorbis with weak support in the COI - only analysis. We were not able to obtain LSU sequence data for Phreatodrobia embossa . In COI, Phreatodrobia embossa has an average p-distance of 17.5 % from Phreatodrobia . The sculpture is distinctive among the Cochliopidae , and the genetic distance is close to what we would expect for genera in the family (which averaged 17.2 %). Phreatodrobia embossa shares aspects of penial morphology with other Phreatodrobia and Phreatoceras species with a simple, slender penis tapering at the distal end, but with less muscular ribbing and no coiling. We chose to include Phreatodrobia embossa in Phreatodrobia to reflect the relatively close phylogenetic relationship with members of that genus, though we acknowledge that further understanding of the relationships among Cochliopidae might result in reassignment in the future.

Etymology.

The name “ embossa ” refers to the teleoconch sculpture pattern similar to embossed designs on leather or paper.

Ecology and habitat.

Caroline Springs (previously T 5 springs), located at The Nature Conservancy’s Independence Creek Preserve, has a discharge of 189–315 L / s ( TNC website), emanating from the early Cretaceous Edwards Limestone ( Barnes et al. 1992; Brune 2002; Brown 2003). The spring run at Caroline springs is heavily modified and impounded. There are several elongate pools forming a raceway immediately downstream from the large main spring pool. Phreatodrobia embossa was found in hyporheic samples taken from gravels in the 2 nd pool of the raceway. This pool is the site discussed and figured as the type locality of Tryonia oasiensis Hershler, Liu, Landye, 2011 . Water chemistry values were as follows: temperature = 15.5 ° C, pH = 9.52, conductivity = 863.6 μS / cm, and dissolved oxygen = 8.26 mg / L. Species found in the sample with Phreatodrobia embossa included Turbellaria and freshwater Annelida. Other molluscs included Physidae , Cochliopina riograndensis and Ferrissia sp. Other hyporheic samples taken at the same site included ostracods, Gammarus seideli Cannizzaro, Walters, Berg, 2017 , Hyalella sp. , Seborgia hershleri Holsinger, 1992 , and Lirceolus sp. We did not encounter Phreatodrobia embossa from numerous drift net samples which were taken at the springs.