Valiguna semicerina Mitchueachart & Panha, 2024

Mitchueachart, Bowornluk, Sutcharit, Chirasak, Tongkerd, Piyoros & Panha, Somsak, 2024, Morphological and molecular evidence uncovers hidden species diversity in the leatherleaf slug genus Valiguna (Systellommatophora, Veronicellidae) from Thailand, ZooKeys 1212, pp. 79-107 : 79-107

Valiguna semicerina Mitchueachart & Panha sp. nov.

Figs 2 , 3 C , 4 B , 7 B , 8

Type material.

Holotype • CUMZ 16087 (length 34 mm, width 13 mm; Figs 4 B , 8 A ) . Paratype • CUMZ 16092 (2 specimens in ethanol) .

Type locality.

Huang Nam Keaw Waterfall , Koh Kood, Trat Province, Thailand, 11 ° 39 ' 19.2 " N, 102 ° 34 ' 53.3 " E.

Other material examined.

Cambodia: • Recreational area near Sanker river , Traeng, Rotanak Mondol, Battambang Province; 12 ° 49 ' 51.4 " N, 102 ° 55 ' 44.3 " E; CUMZ 16088 ; Myanmar: • Dhammatat Cave , Mawlamyine Township, Mon State; 16 ° 30 ' 23.0 " N, 97 ° 48 ' 36.3 " E; CUMZ 16089 ; Thailand: Sa Kaeo: • Khao Chakan , Khao Chakan; 13 ° 39 ' 42.6 " N, 102 ° 05 ' 22.5 " E; CUMZ 16090 ; Chonburi: • Wat Khao Chalak , Sriracha; 13 ° 11 ' 49.3 " N, 100 ° 56 ' 56.6 " E; CUMZ 16091 ; Trat: • Suanya Koh Kood Resort & Spa , Koh Kood; 11 ° 39 ' 58.9 " N, 102 ° 32 ' 05.6 " E; CUMZ 16093 .

Diagnosis.

Notum pale to dark brown with random tiny blackish spots, and median dorsal line visible. Hyponotum and foot paler in colour with or without scattered blackish spots. Penis rounded lanceolate with honeycomb-like glans on one side and smooth surface on opposite side; vas deferens opens at peak near basal part of honeycomb-like glans. Penial tubules consist of 18–22 tubules of varying lengths (short, intermediate, and long).

External characteristics.

Preserved specimen. Notum pale to dark brown with scattered tiny blackish spots. Body elongated ovate, 32–45 mm (39.6 ± 5.1 mm) long, and 11–16 mm (13.4 ± 1.7 mm) wide. Median dorsal line thin and narrow, and paler colour than notum. Hyponotum white, beige to pale brown and with or without numerous tiny blackish spots. Foot white, pale yellow to beige, and narrower (width 2.0–4.0 mm) than right hyponotum width. Male genital pore located close to base of right lower tentacle. Female genital pore located approximately midway of body on right hyponotum (Fig. 8 A ).

Live specimen. Notum pale to dark brown and with scattered tiny blackish spots. Median dorsal line thin and pale colour. Hyponotum varies from white to pale beige or pale brown, and with or without pale blackish spots. Foot white to pale beige (Fig. 4 B ).

Genital organs. Penis acropleurocaulis type; penis base (pb) cylindrical and relatively short. Penis glans (gn) an elongated conical shape with honeycomb formation on peak side and smooth surface on opposite side. Vas deferens (vd) opens at tip of peak. Peak (pk) triangular shaped and located somewhat near penis base (Fig. 8 B ). Penial gland with conical papilla (pa). Penial tubules 18–22 tubules: comprised of four short tubules (st), six intermediate tubules (it), and 8–12 long tubules (lt); sometimes around five bifurcating tubules appeared on intermediate and long tubules (Fig. 8 C ).

Bursa copulatrix duct (db) bottle shaped, slightly enlarged cylindrical near genital pore and tapering to short and narrow near bursa copulatrix. Bursa copulatrix (bc) almost circular shaped and connected to bursa copulatrix duct. Oviduct (ov) and albumen gland (ag) extremely enlarged, soft lobulated and tufted; oviduct opened at female genital pore (fg). Distal (dd) and proximal (pd) posterior deferens inserted into triangular-shaped prostate gland (pr). Middle deferens (md) penetrates into thick muscular right hyponotum then emerges near male genital pore (mg) before inserting into penis. Canalis junctor (cj) penetrates almost at middle of bursa copulatrix duct. Fertilisation complex (fc) short and small tube; seminal vesicle (sv) thin and curly, and attached to albumen gland with thin connective tissue. Spermioduct (sd) thin, unconvoluted, and contracts into numerous small globular hermaphroditic gland subunits. Hermaphroditic gland (hg) consists of many medium-sized subunits (Figs 3 C , 8 D, E ).

Radula. Teeth arranged in nearly straight rows, each row containing ~ 70 teeth with half row formula 1–35 +. Central teeth very small and unicuspid. Lateral and marginal teeth not differentiated, monocuspid, large triangular shaped, and with slightly pointed cusp. From inner to outer, lateromarginal teeth gradually narrower, smaller, and rather pointed cusp, and outermost teeth relatively small and irregular shaped (Fig. 7 B ).

Etymology.

The specific name semicerina is from the Latin words semis meaning half and cera meaning honeycomb, which refers to the shape of the penis of this new species.

Distribution.

Valiguna semicerina sp. nov. is known to distributed in eastern Thailand, the Batttambang Province in Cambodia, and the Mon State in Myanmar (Fig. 1 ).

Comparative diagnosis.

Valiguna semicerina sp. nov. can be distinguished from V. siamensis and V. flava in having an elongated conical shape and honeycomb structure on peak side of penis glans surfaces, and with 18–22 unequal length (four short, six intermediate, and 8–12 long) and five bifurcation penial tubules. In comparison, V. siamensis possesses a cylindrical penis and honeycomb-like glans, and with 21–31 unequal length (two short and 19–29 long) and two bifurcation penial tubules, whereas V. flava possesses a cylindrical penis, tapering, and bends with dentate and serrate glans. Moreover, V. flava has 15 short penial tubules (Table 4 ; Gomes et al. 2008).

In addition, this new species also differs from V. crispa sp. nov. and F. bleekeri in having a honeycomb structure on penis glans, and with 18–22 unequal length and five bifurcation penial tubules. In comparison, V. crispa sp. nov. possesses a wavy-like structure on penis glans, and 11 equal length penial tubules without bifurcation (Table 4 ), whereas F. bleekeri possesses an acrocaulis cylindrical penis with submedial annular ridge, and with 12–18 short penial tubules (see Hoffmann 1925: pl. 5, fig. 45 c 4).

Remarks.

This new species is superficially similar to V. siamensis . However, after examining lots of specimens of various sizes from several localities, V. semicerina sp. nov. generally has no tiny blackish spots on hyponotum, while V. siamensis tended to have many tiny pale blackish spots spread on the hyponotum.

Figures

Figure 1. Geographic distribution of Valiguna siamensis, V. semicerina sp. nov., and V. crispa sp. nov. based on the specimens examined herein.

Figure 2. Phylogenetic tree showing the relationships among species of Valiguna based on the COI gene sequences. Numbers by the nodes are the ML BS (left) and BI PP (right) values. Note, SH-aLRT ≥ 80 %, aBayes ≥ 0.95, BS ≥ 95 %, and PP ≥ 0.95 for each node were determined to be well supported. (*) indicates the holotype and (**) indicates the topotype.

Figure 3. A schematic drawing showing an arrangement of the reproductive system of Valiguna B – D female reproductive system of B V. siamensis, specimen CUMZ 16054 from Chanthaburi C V. semicerina sp. nov., holotype CUMZ 16087 from type locality, and D V. crispa sp. nov., holotype CUMZ 16094 from type locality.

Figure 4. Living slugs A Valiguna siamensis, specimen CUMZ 16038 from Khon Kaen (length ~ 60 mm) B V. semicerina sp. nov., holotype CUMZ 16087 from type locality (length ~ 34 mm), and C V. crispa sp. nov., holotype CUMZ 16094 from type locality (length ~ 28 mm). Dorsal view (left) and ventral view (right).

Figure 7. SEM images of radula A Valiguna siamensis, specimen CUMZ 16054 from Chanthaburi B V. semicerina sp. nov., holotype CUMZ 16087 from type locality, and C V. crispa sp. nov., holotype CUMZ 16094 from type locality. Central tooth indicated by ‘ C’.

Figure 8. Valiguna semicerina sp. nov., holotype CUMZ 16087 from type locality A dorsal and ventral views B penis C penial gland and penial tubules D dorsal and ventral views of female genitalia, and E inset of female genitalia.