Canariella giustii Ibáñez & Alonso, 2006

Ibáñez, Miguel, Siverio, Felipe, Alonso, María R. & Ponte-Lira, Carmen E., 2006, Two Canariella species (Gastropoda: Helicodea: Hygromiidae) endemic to the Northwest Tenerife (Canary Islands), Zootaxa 1258, pp. 33-45 : 37-42

Canariella giustii Ibáñez & Alonso new species

Type locality. Barranco de Masca (Tenerife; UTM coordinates: 28 RCS 1831, 250 m altitude).

Holotype ( Fig. 4 B): TFMC (MT 0387); leg. M. Ibáñez, 14­11­1983.

Paratypes. 256 paratypes (49 alcohol specimens and 207 shells, leg. between 1982 and 2005). TFMC (MT 0277/1), CGH (1 paratype), CFS (20 paratypes) and AIT (235 paratypes).

Etymology. The specific name derives from the family name of Dr. Folco Giusti (University of Siena), to whom we dedicate this species for his remarkable contributions to the knowledge of land and freshwater snails.

Distribution and habitat ( Fig. 1 ): The species is endemic to Tenerife, occupying a range of habitats, from dry open areas through to humid laurel forests (“laurisilva”), between 40 to 1050 m altitude. In the area in which it co­occurs with C. pontelirae , both species are also found subfossil to depths of 15 m.

Diagnosis: A medium­sized Canariella with a depressed, dorso­ventrally flattened, discoidal, umbilicate shell, angular at the periphery; 4¾–5½ whorls. Epiphallus opening laterally on the proximal side of the broadened penis. Two epiphallar folds extending in the proximal part of the penial cavity without forming the penial papilla that is present in other species.

Description: Shell ( Fig. 4 B) dextral, depressed, dorso­ventrally flattened, angular at periphery, with a small to medium­sized diameter and a spire of 4¾–5½ slightly convex whorls and a marked suture; umbilicus about 14% of shell diameter, slightly obscured by the reflected lip. Mouth rounded­ovate with a discontinuous peristome, slightly expanded as a pale lip at the basal­columellar edge. Colour uniform matt brown. Protoconch with small granulations; teleoconch densely, regularly, radially ribbed, ventral ribs slightly smoother than dorsal ones. Thin periostracal hairs present on periphery (up to 800 μm long) but only up to 140 μm long on the umbilicus.

TABLE 1. Data of known living Canariella species.

La Gomera C. discobolus (Shuttleworth, 1852) , Shuttleworth (1852b),

Helix afficta A. Férussac , in Férussac & Deshayes, Ibáñez et al. (1995)

1832

La Gomera C. tenuicostulata Alonso, Ibáñez & Ponte­Lira, 2003 Alonso et al. (2003) Genital system (7 specimens dissected; Figs. 5 D, 6B): Atrium short. Distal male duct between atrium and penis retractor muscle insertion almost twice as long as the epiphallar proximal portion and 5–6 times longer than flagellum. Flagellum and epiphallus tubular, the latter opening laterally on the proximal side of the broadened penis, whose diameter is twice than that of the epiphallus.

Epiphallus with two internal, distally expanded, longitudinal folds which extend in the penis tilting towards the proximal penial concavity opposite the epiphallar insertion, ending separately but very close to each other, not merged into a penial papilla. Each epiphallar fold distally has a transverse constriction, forming a small, terminal papilla (indicated by arrows in the Fig. 5 D–a,c). The penis has 7–8 longitudinal internal pilasters ( Fig. 5 D–c).

Short vagina proximally widened, with numerous irregular longitudinal folds, some of them anastomosed, and 3–8 crown­shaped, finger­like vaginal glands, which open near the orifice connecting the vagina to the oviduct ( Fig. 5 D–a).

Remarks. C. giustii differs from all the other living Canariella species by its broadened penis. The penis diameter of C. giustii is twice than that of the epiphallus, with an eccentric, lateral­proximal epiphallar opening; the distal male duct broadens rapidly in the proximal part of penis. All the other living Canariella species have the penis about 1–1½ times broader than the epiphallus, with a central epiphallar opening, and the distal male duct broadens gently in the proximal part of penis.

Moreover, C. giustii differs from all the other living Canariella species in its penial anatomy. It is the only Canariella species in which the two epiphallar folds extend together in the penis, tilting towards the proximal penial concavity opposite to the epiphallar insertion and ending very close but independent of each other, not merged into a penial papilla.

The species most similar to C. giustii ( Fig. 4 B) in shell dimensions are C. hispidula ( Fig. 4 C) and C. pontelirae ( Fig. 4A ). The C. giustii shell measurements ( Fig. 3 ) occupy an intermediate position between the other two, but with a broad overlap, although the shell height and frontal surface of C. giustii are bigger than the others in relation to the maximum diameter and frontal perimeter, respectively. C. giustii has a narrower umbilicus than those of the other two species ( Fig. 4 ). The C. giustii teleoconch is angular at periphery and densely, regularly, radially ribbed, whereas the C. pontelirae teleoconch is keeled and has prominent and regularly spaced radial ribs separated by 4–5 small ribs. The C. hispidula shell is the most similar to that of C. giustii in shape and ornamentation, but has a more angular periphery and it is shaggy, whereas that of C. giustii is almost hairless, the adult live specimens only having well­developed hairs at the periphery.

Figures

FIGURE 1. Geographic distribution of Canariella pontelirae and C. giustii sp. nov.; symbols represent 1 x 1 km UTM squares.

FIGURE 3. Scatter plots of some shell measurements for Canariella pontelirae, C. giustii sp. nov. and C. hispidula. Abbreviations same as in Fig. 2.

FIGURE 5. Drawings of genital systems and details of distal portions. A. Canariella bimbachensis from Las Lajas (El Hierro; taken from Ibáñez et al. 2002, Fig. 1 B). B. C. discobolus from Barranco de La Rajita (La Gomera; taken from Ibáñez et al. 1995, Fig. 34). C. C. hispidula from Tabaiba Alta (Tenerife; taken from Ibáñez et al. 1995, Fig. 28). D. C. giustii sp. nov. from La Punta (Teno massif, Tenerife). a, general appearance of the whole genital system; at, atrium; ag, albumen gland; b, detail of the distal female duct; bc, bursa copulatrix; c, detail of the distal male duct; d, epiphallus­penis diagram (without scale); e, vaginal cross­section diagram with arrangement of vaginal glands (without scale); ef, epiphallar fold; ep, epiphallus; f, flagellum; go, genital orifice; o, free oviduct; p, penis; pi, pilaster; pp, penial papilla; r, retractor muscle; s, sheath; t, body tegument; v, vagina; vd, vas deferens; vg, vaginal gland.

FIGURE 4. A. Canariella pontelirae living specimen and shell, from La Punta (Teno massif, Tenerife). B. C. giustii sp. nov., holotype shell. C. C. hispidula shell, from Las Caletillas (Tenerife).