Hemicycla (Hemicycla) fulgida, Alonso, María R. & Ibáñez, Miguel, 2007

Alonso, María R. & Ibáñez, Miguel, 2007, Anatomy and function of the penial twin papillae system of the Helicinae (Gastropoda: Helicoidea: Helicidae) and description of two new, small Hemicycla species from the laurel forest of the Canary Islands, Zootaxa 1482, pp. 1-23 : 9-15

Hemicycla (Hemicycla) fulgida sp. nov.

Type locality. Pista de Las Yedras, Anaga massif, Tenerife (UTM: 28 RCS 7456, 900 m altitude). Holotype ( Fig. 8 A). TFMC (MT 0394); leg. M.R. Alonso and M. Ibáñez, 15th January 1993.

Paratypes. 24 paratypes (4 preserved in ethanol specimens and 20 shells, collected between 1982 and 2006), TFMC (1 paratype: MT 0395) and AIT.

Etymology. The name “ fulgida ” derives from the feminine of the Spanish adjective “fúlgido” and refers to the brilliant, radiant appearance of the shell.

Distribution and habitat ( Fig. 1 ). The species is endemic to Tenerife. It occurs at an altitude of 650–980 m, living between the very abundant dead leaves of the laurel forest from the Anaga massif (northeast Tenerife).

Description. Body brown coloured ( Fig. 3 B), sole pale-brown. The shell (Table 2; Figs. 3 B, 8A) is imperforate, depressed globular but slightly conical in the first whorls, with 3¾–4¼ convex whorls and well marked sutures. The aperture is oblique and rounded, without angulations. The peristome is reflected in a white lip (corneous-yellowish above) which has a width of about 1 mm and covers the umbilicus. The shell has a small, weak and wide radial costulation combined in the body whorl with a malleate surface sculpture.

The shell surface ( Fig. 9 A,B) is glossy, brilliant and pale-brown to yellowish in colour. In some specimens there are four spiral, darker bands, two dorsal wide and frequently interrupted and two ventral narrower and more uniform. In many specimens the bands are wide, but interrupted forming irregular patches. These patches sometimes fuse with those of the neighbouring bands (dorsal or ventral), giving the appearance of irregular patches arranged radially.

Genital system ( Figs. 11 A, 12; 4 specimens dissected): Atrium short. The bursa copulatrix complex in the female genital system shows a moderately short diverticulum, shorter than the bursa copulatrix duct; the latter is also shorter than the slender, not swollen distally common stalk. The bursa copulatrix is rather small, globular. The female duct seemingly concludes in the common stalk duct ( Figs. 11 A, 12A) but in fact this duct and the vagina are close and they open up in the atrium, together with the dart sac, each independent of the others (Fig. 12B). The dart sac is accompanied by a pair of branched tubular mucus glands. The dart ( Fig. 13 C) is long (about 4.3 mm), slightly curved (almost straight), spear-head shaped, and has four lateral wings. Its transverse section resembles a normal cross (relationship width/depth = about 1.3) and is similar overall to that of some species of Helix , such as H. pomatia Linnaeus, 1758 , H. lucorum Linnaeus, 1758 and H. aperta Born, 1778 ( Meisenheimer 1912, Giusti & Lepri 1981, Giusti & Andreini 1988).

FIGURE 6. Genital system and details. A–C. Hemicycla laurijona sp. nov., paratypes from the type locality. D–F. Hemicycla perraudierei , from Las Casillas, El Hierro. A, B, D, E. The whole genital system. C, F. Anatomy of the distal genital system; co, contact organ; e, epiphallus; go, genital orifice; pp 1, proximal penial papilla; pp 2, distal penial papilla; ri, ring zone.

The male portion of the genital system shows a penial complex with a short flagellum, similar in length to the sum of the penis and epiphallus. The penis sheath is very thin, translucent and poorly visible. The retractor muscle has an epiphallar insertion and the penis has a system of twin papillae with a penial chamber between them (Fig. 12B). The “ring zone” is visible from the exterior ( Figs. 11 A, 12A). A well-developed contact organ is located between the distal penial papilla and the atrium (Fig. 12B).

A specimen had a spermatophore partially digested in the common stalk of the bursa copulatrix system ( Fig 13 A,B). This undigested part is a long, corneous sheet spirally rolled around the axis, forming a lengthwise open, filiform tube (diameter less than ½ mm) folded inside the receiving duct.

Another specimen everted the distal genital system during the fixation process (Fig. 14). Namely, the atrium and the entire penis were evaginated, whereas the distal end of the female part of the genital system was protruded. The boundary of the evagination has been studied by dissecting the penial evagination: the distal epiphallar folds are located immediately behind the hole of the proximal penial papilla, which is at the end of the evaginated penis (Fig. 14C,D). The contact organ is at the base of the evaginated penis, immediately adjacent to a protuberant ring which corresponds to the “ring zone” of the non-evaginated penis.

Remarks. Regarding the shell, the nearest species to Hemicycla fulgida are H. consobrina— also from the Anaga laurel forest and similar areas ( Figs. 8 C, 9E,F, 10)—and H. invernicata ( Figs. 8 B, 9C,D), whose type locality is: "Ténérife, environs de Sta-Cruz. Dans les creux d'arbres dans les bosquets à la Esperanza, près des Lagunes" [correct name: Las Lagunetas, about 1400 m altitude, including a pine forest; it is the area marked with the blue arrow in Figure 1 ]. The last two species are similar in appearance and Bank et al. (2002) grouped H. invernicata as a subspecies of H. consobrina . However, they differ in shell and genital characters. The aperture of the H. consobrina shell was described by Mousson (1872) as “obtusément triangulaire” ( Fig. 10 A), with a very small callosity ( Fig. 10 A–D, yellow arrows) in the same position as the smaller tooth-like callosity of the two present in the shell aperture of H. bidentalis ( Lamarck, 1822) , a well-known species living in the same area as H. fulgida and H. consobrina .

The H. fulgida shell dimensions are smaller than those of the other two species mentioned above, which also are more depressed (Figs. 7,8). The shell ornamentation of H. fulgida and H. invernicata are very similar ( Fig. 10 A–D), whereas the H. consobrina shell has a more developed malleation ( Fig. 9 E–F). Moreover, H. fulgida and H. invernicata differ in their habitat: humid laurel forest and dry pine forest, respectively.

The maximum diameter of the H. fulgida shell is similar to that of H. laurijona and H. perraudierei although the H. fulgida shell is higher than those of the other species ( Fig. 7 ).

Several other differences were found among H. fulgida , H. invernicata and H. consobrina regarding the genital system ( Fig. 11 ). The H. fulgida genital system ( Fig. 11 A) differs from that of H. invernicata ( Fig. 11 B) and H. consobrina ( Fig. 11 C) in the flagellum length. It is 1/3 longer than that of H. invernicata and about twice as long as that of H. consobrina . The atrium of the latter two species is longer than that of H. fulgida . The H. fulgida bursa copulatrix stalk is about twice as long, while the diverticulum is about 1/3 shorter than that of H. invernicata , in which the diverticulum is slightly longer than the bursa duct. The H. fulgida stalk and the bursa duct are about 1/3 longer than those of H. consobrina , while the diverticulae of both species are similar in length, and they are shorter than the respective bursa ducts.

The main difference between the H. fulgida genital system and that of H. laurijona and H. perraudierei is related to the flagellum length. The diverticulum of H. fulgida is also shorter than that of H. laurijona and H. perraudierei , in comparison with the respective bursa duct length.

Figures

FIGURE 1. Geographical distribution of Hemicycla laurijona sp. nov. and Hemicycla fulgida sp. nov. The blue arrow indicates approximately the area of the Hemicycla invernicata type locality. Symbols represent 1 x 1 km UTM squares.

FIGURE 7. Scatter plots of some shell measurements of the species studied. 1, Hemicycla consobrina; 2, Hemicycla invernicata; 3, Hemicycla fulgida sp. nov.; 4, Hemicycla perraudierei; 5, Hemicycla laurijona sp. nov. BP, body whorl frontal perimeter; BS, body whorl frontal surface (plane view); D 1, maximum shell diameter; D 2, shell diameter perpendicular to D 1; FP, shell frontal perimeter; FS, shell frontal surface (plane view); SH, shell height; SP, shell perimeter (dorsal plane view); SS, shell surface (dorsal plane view).

FIGURE 8. Shells from Tenerife. A. Hemicycla fulgida sp. nov., holotype. B. Hemicycla invernicata from Montaña Cabeza de Toro pine forest, near Las Lagunetas (La Esperanza forests). C. Hemicycla consobrina from Las Mercedes laurel forest.

FIGURE 9. Shell body whorl details. A, B. Hemicycla fulgida sp. nov., holotype. C, D. Hemicycla invernicata. E, F. Hemicycla consobrina. A, C, E, dorsal view. B, D, F, frontal view.

FIGURE 10. Shell aperture details of the Hemicycla consobrina specimen in different views (A – D), showing the “ small callosity ” (yellow arrows) and the form “ obtusément triangulaire ” described by Mousson. A. Aperture accurately in plane view.

FIGURE 11. Genital system. A. Hemicycla fulgida sp. nov., paratype from El Bailadero. B. Hemicycla invernicata from Montaña Cabeza de Toro. C. Hemicycla consobrina from Guamasa; ri, ring zone.

FIGURE 13. Hemicycla fulgida sp. nov., paratype from El Bailadero (Tenerife). A. Spermatophore in the stalk of the bursa copulatrix complex. B. An undigested part of the spermatophore. C. Dart; bd, bursa duct; c, crown; d, diverticulum; st, stalk.

FIGURE 3. A. Hemicycla laurijona sp. nov., paratype from Puntas Coloradas, La Gomera. B. Hemicycla fulgida sp. nov., paratype from El Bailadero, Tenerife.