Zilchistrophia shiwiarorum Pall-Gergely

Pall-Gergely, Barna & Asami, Takahiro, 2014, Description of two new Ecuadorian Zilchistrophia Weyrauch, 1960, with the clarification of the systematic position of the genus based on anatomical data (Gastropoda, Stylommatophora, Scolodontidae), ZooKeys 453, pp. 1-17 : 3-9

Taxon classification Animalia Stylommatophora Scolodontidae

Zilchistrophia shiwiarorum Pall-Gergely sp. n. Figs 1D, F, 2 I–M, 3 C–D, 4A, C, E

Type material.

Ecuador, Pastaza Province, near Nuevo Corrientes, transect 5 (sample 141), leg. Hilary Kingston, 08.09.2000., NHMUK 20020382/1 holotype; Ecuador, Pastaza Province, near Nuevo Corrientes, transect 5 (sample 137), leg. Hilary Kingston, 08.09.2000., NHMUK 20020381/1 paratype; Ecuador, Pastaza Province, near Nuevo Corrientes, transect 5 (sample 101), leg. Hilary Kingston, 08.09.2000., NHMUK 20020378/1 paratype; Ecuador, Pastaza Province, near Nuevo Corrientes, transect 5 (sample 128), leg. Hilary Kingston, 08.09.2000., NHMUK 20020380/1 paratype; Ecuador, Pastaza Province, near Nuevo Corrientes, transect 5 (sample 125), leg. Hilary Kingston, 08.09.2000., NHMUK 20020379/1 paratype; Ecuador, Pastaza Province, near Nuevo Corrientes, transect 5 (sample 143), leg. Hilary Kingston, 08.09.2000., NHMUK 20020383/1 paratype; Ecuador, Pastaza Province, valley south of Nuevo Corrientes, transect 3, 02°00.365'S, 076°45.933'W, 321 m asl. (sample 37), leg. Hilary Kingston, 01.09.2000., NHMUK 20020368/1 paratype; Ecuador, Pastaza Province, valley south of Nuevo Corrientes, transect 3, 02°00.365'S, 076°45.933'W, 321 m asl. (sample 39), leg. Hilary Kingston, 01.09.2000., NHMUK 20020377/1 paratype; Ecuador, Pastaza Province, Nuevo Corrientes (sample 90), leg. Hilary Kingston, 05.09.2000., NHMUK 20020376/1 paratype; Transect 3, forest floor near Nuevo Corrientes, Pastaza, Ecuador, sample 33, leg. Hilary Kingston, 01.09.2000., NHMUK 20020421 (dissected, ethanol-preserved animal).

Diagnosis.

A small Zilchistrophia species with regularly growing whorls, angled body whorl, narrow umbilicus and two palatal plicae approximately half a whorl behind the aperture.

Description of the shell.

Shell dextral, whitish, glossy and translucent, smooth, only irregular, very fine growth lines can be seen; shell shape discoid, with domed apical surface; whorls 6.5 (n=2), regularly growing, only the apertural part is slightly wider than the penultimate whorl; body whorl with blunt but conspicuous upper keel; whorls are separated by relatively deep suture; umbilicus narrow, regular funnel-shaped; aperture deformed crescent-shaped (because of the upper keel), with thickened peristome; parietal callus not conspicuous, present as slight, blunt thickening, its sculpture is extremely finely granulated, rather matt.

One, two or three sets of horizontal, short plicae are situated behind the aperture (Fig. 2 I–M). Both plicae are simple, horizontal thickenings on the parietal wall (Fig. 1F). These plicae can be observed in the case of fresh, translucent shells only. A juvenile shell had three sets of plicae, whereas all adult shells had one or two sets of plicae only. In this species as well, we assume that the previous sets of plica are in most cases dissolved during growth. See also remarks under Zilchistrophia hilaryae sp. n.

Measurements (in mm). D: 3.5-3.9, H: 2.2-2.5 (n=4).

Description of the anatomy.

One specimen was anatomically examined (Transect 3, forest floor near Nuevo Corrientes, Pastaza, Ecuador, sample 33, leg. Hilary Kingston, 01.09.2000., NHMUK 20020421).

Body. The part of the body which filled the last whorl of the ethanol-preserved specimen had an intensive pink/orange colour, whereas the ethanol was slightly pinkish. The remaining parts of the animal were brown. It is unknown whether this was the original colour of the living specimen, or it is the result of a secondary chemical reaction. Foot clearly aulacopod (Fig. 4C); caudal horn absent, but there is a seemingly inflated thickening above the tail in the ethanol-preserved animal (probably glandula, see Fig. 4A); jaw absent; buccal mass conspicuously long (Fig. 4E); the pallial complex could not be examined due to the decay of the body.

Radula. Indistinguishable from that of Zilchistrophia hilaryae sp. n.

Genitalia (Fig. 3 C–D). The right ommatophoral retractor runs between penis and vagina; penis long, slender, simple thin-walled tube, without any notable inner structure; penis surrounded by a thick, fibrous tunica; the end point of the penis is considered where the tunica narrows; epiphallus is approximately half of the size of the penis, and it is more slender than the penis including the tunica; the proximal end of the epiphallus forms a loop before the insertion of the retractor muscle; the long retractor muscle is thickened distally, and inserts on the epiphallus-vas deferens transition; vas deferens slender, enters epiphallus subapically, it is attached to the epiphallus almost along the complete length of the epiphallus; vagina very short, it is attached to the body wall with a few fibres; the thickened part of the spermoviductus is in fact a cavity which joins the rest of the inner space through a narrowing; no embryos were found within the uterus; the bursa copulatrix and the posterior part of the spermoviductus could not be investigated because the decayed condition of the body.

Differential diagnosis.

Zilchistrophia shiwiarorum sp. n. can be distinguished from the other four species by the small shell size and the angled body whorl. See also the differential diagnosis under Zilchistrophia hilaryae sp. n.

Etymology.

Zilchistrophia shiwiarorum sp. n. is named after the Shiwiar tribe, which inhabits the area where both new species live.

Type locality.

Ecuador, Pastaza Province, near Nuevo Corrientes.

Distribution

(Fig. 6). Zilchistrophia shiwiarorum sp. n. is known only from the vicinity of Nuevo Corrientes, Pastaza Province.

Ecology.

Same as in Zilchistrophia hilaryae sp. n.

Conservation status.

See under Zilchistrophia hilaryae sp. n.