Semisulcospira reticulata Kajiyama & Habe, 1961

Sawada, Naoto, Fuke, Yusuke, Miura, Osamu, Toyohara, Haruhiko & Nakano, Takafumi, 2024, Redescription of Semisulcospira reticulata (Mollusca, Semisulcospiridae) with description of a new species from Lake Biwa, Japan, Evolutionary Systematics 8 (1), pp. 127-144 : 127-144

Semisulcospira reticulata Kajiyama & Habe, 1961

Table 4 , Figs 7 A – Y , 8 A – D , 9 C Japanes name: Kagome-kawanina (Kajiyama and Habe 1961 )

Semisulcospira decipiens reticulata Kajiyama & Habe, 1961: 171–173, 175–176, figs 6, 6 a; Habe 1965: 57, unnumbered figure; Kawase et al. 2012: 37, figs 2–11.

Semisulcospira reticulata – Burch and Davis 1967: 36–37; Burch 1968: 6, 26–29, fig. 1 D, pl. 4, figs 4, 5, pl. 5, fig. 8; Davis, 1969: 249, 255, pl. 5, figs 1, 2, pl. 6, figs 1, 2, pl. 10, figs 10, 11, pl. 11., figs 1–4; Watanabe 1970 a: 17 –23, fig. 15-3, 8, 9; Habe 1986: 322, fig. 17-1 - 17; Köhler 2016: fig 4 L – N; Sawada and Fuke 2022: fig. 11 bq – bu.

Biwamelania decipiens – Habe 1978: 94; Minato 1991: 79, unnumbered fig.

Semisulcospira (Biwamelania) reticulata – Matsuoka 1985: 190; Watanabe and Nishino 1995: app. pl. 1, fig. 8, app. pl. 2, figs 22, 23; Nishino and Watanabe 2000: fig. 2–12; Matsuda 2000: 8–9, unnumbered fig.; Kihira et al. 2009: 26–27, 33, unnumbered figs; Miura et al. 2019: fig. S 1 p – r; Nishino 2021: 618.

Biwamelania reticulata – Kihira and Matsuda 1990: 22–23, 25, unnumbered figs; Nishino and Tanida 2018: 60, 253, unnumbered figs.

Semisulcospira decipiens multigranosa – Kawase et al. 2012: 37, figs 2–10.

Material examined.

Holotype. NSMT - Mo 39770, adult female, collected from “ Off Okinoshima in Lake Biwa ” ( Lake Biwa , offshore of Oki-shima Island , Okishima-cho, Omi-hachiman City, Shiga Prefecture, Japan).

Additional materials.

KUZ Z 4926 , 15 females, Z 4927, 9 males, collected from 6–8 m water depths at Hannoura on 26 June 2022 ; KUZ ZZ 4930 , 15 females, Z 4931, 5 males, from 5–8 m depths at Kitafunaki on 10 July 2022 ; KUZ Z 4925 , 15 females, from 10–15 m depths offshore at Oki-shima Island on 28 April 2019 ; KUZ Z 4229 , 4 females, Z 4286, 4 males, from 6–12 m depths at Mano on 12 October 2021 .

Amended diagnosis.

Viviparous. Teleoconch elongated, large in the genus [SH 36.4 ± 3.7 (mean ± SD) (female), 27.2 ± 3.1 (male) mm; BWL 18.4 ± 1.8, 14.2 ± 0.8 mm]; spires laterally broadened (SA 18.0 ± 2.3, 18.8 ± 3.3 degrees), axially compressed (WER 2.4 ± 0.2, 2.7 ± 0.6); outer lip of aperture simple, smooth; aperture rounded (ASR 1.6 ± 0.1, 1.6 ± 0.1); basal cords few (BCN 3.3 ± 0.7, 3.4 ± 0.9); longitudinal ribs distinct, granulated, in large number on penultimate whorl, (RN 26.4 ± 3.2, 21.6 ± 2.2); spiral cords in medium number (SCN 6.2 ± 0.8, 5.3 ± 0.8); color in light brown background. Protoconch large in the genus (SLP 5.0 ± 1.1 mm, WNP 3.8 ± 0.4); longitudinal ribs distinct; spiral cord weak or absent; color in yellowish-brown, with or without 1–3 dark brown bands.

Description of holotype

( NSMT - Mo 39770; Fig. 7 A – F ). Teleoconch. AH 9.9 mm, AL 10.4 mm, ASR 1.54, AW 6.8 mm, BCN 4, BWL 17.9 mm, FWL 3.8 mm, PWL 7.1 mm, RN 24, SA 19.5 degrees, SCN 6, SH 35.7 mm, SW 12.8 mm, TWL 4.6 mm, WER 2.60, WN 7.00; shell elongated; spires moderately broadened laterally, slightly convex; suture almost straight; outer lip of aperture simple, smooth; aperture rounded; apex of shell eroded; longitudinal ribs distinct, oblique, opisthocyrt, prominently granulated at intersection with spiral cords; shell surface brown to blackish-brown with deposits.

Protoconchs. RNP 14, SLP 5.8 mm, SWP 4.1 mm, WNP 4.00; shell globose; suture slightly undulating; longitudinal ribs remarkable, with rounded nodes in 2 rows; spiral cord weak on lower part of whorls; shell colored light beige in background, without color band.

Variation.

Teleoconchs (Fig. 7 G, J, K, N, P, S, U, X ). Measurements and counts shown in Table 4 . Spires slightly to moderately broadened, slightly to strongly convex; suture typically slightly undulating, sometimes almost straight; longitudinal ribs distinct, oblique, typically orthocline to opisthocyrt on upper whorls, opisthocyrt on lower whorls, sometimes opisthocline on upper and lower whorls, rarely fade in body whorl; spiral cords rarely distinct; shell colored yellowish-brown to light brown, with dark brown longitudinal stripes; color bands dark brown or dark olive, sometimes present on central part of upper whorls.

Opercula (Fig. 7 H, L, O, Q, T, V, Y ). 5.8–8.9 mm in long diameter; nearly egg-shaped subcircular, paucispiral, comprising around 3 whorls; nucleus subcentral.

Protoconchs (Fig. 7 I, M, R, W ). Measurements and counts shown in Table 4 . Shell globose or slightly elongated; suture slightly to moderately undulating; longitudinal ribs distinct, smooth, rarely granulated on central part of whorls in 1–2 rows; spiral cords weak or absent on lower part of whorls; shell colored beige to light beige in background; color bands olive or dark brown, thick, sometimes present on upper and lower parts of whorls and basal part.

Radulae (Fig. 8 A – D ). Taenioglossa. Rachidian teeth consisting of central denticle and 2–4 small pointed triangular cusps on each side; tip of rachidian central denticle narrow, pointed, triangular, 2.0–3.5 times longer than other triangular cusps. Lateral teeth consisting of large central denticle and 2–4 inner and outer pointed cusps; central cusp of lateral teeth narrow, pointed, triangular, 2.0–3.0 times longer than other triangular cusps. Interior and exterior marginal teeth spoon-shaped, with 4–6 rounded denticles.

Reproductive organs: Female (Fig. 9 C ). Oviduct long, narrow, emerging from ovary entering near seminal receptacle on ventral side of soft body; protrusions of seminal receptacle long or short. Sperm gutter extending from spermatophore bursa towards mantle cavity, curved inward along whorls. Brood pouch extending along dorsal side of spermatophore bursa and sperm gutter, dorsally inflated, separated into many chambers, including eggs and embryos; eggs colored beige to orange, radially developing from base of brood pouch near seminal receptacle.

Male. Vas deferens long, narrow, emerging from testes, entering posterior end of prostate. Prostate without penis elongated, inflated in posterior ventral side, with deep groove, forming U-shape in transverse section, anterior narrowly opening to mantle cavity.

Distribution and ecology.

Semisulcospira reticulata has been recorded from the northern and southern basins of Lake Biwa ( Watanabe and Nishino 1995: fig. 5 e; Fig. 1 ). However, this species has not been collected from the southern basin of the lake in recent years ( Nishino and Tanida 2018). Semisulcospira reticulata was found on sandy mud to mud bottoms at depths of 4–30 m (Watanabe 1970, 1980; Table 1 ). The species was collected with other congeners: S. niponica - group, S. decipiens at Hannoura, Kitafunaki, and Mano, S. nishimurai sp. nov. at Hannoura and Kitafunaki; S. nakasekoae - group, S. cryptica and S. ourensis at Hannoura, S. arenicola at Kitafunaki, S. elongata at Kitafunaki, Oki-shima Island, and Mano, S. davisi at Hannoura, Kitafunaki, and Oki-shima Island. Semisulcospira reticulata was found with S. reiniana at Kitafunaki.

Remarks.

Genetic differentiation among specimens from Kitafunaki and the other localities were clarified in this species (Figs 2 , 3 ) whereas morphological distinctiveness were not observed in the Kitafunaki specimens (Table 4 ). The teleoconch of S. reticulata resembles that of S. nishimurai sp. nov. However, S. reticulata represents a greater number of axial ribs on the teleoconch, and the protoconch size of S. reticulata is prominently larger than that of S. nishimurai sp. nov. Although the protoconch size and shape of S. reticulata are similar to those of S. davisi , larger SH, BWL, and SA values of S. reticulata discriminate the two species.

Figures

Figure 1. Map representing seven localities where Semisulcospira reticulata (purple) and S. nishimurai sp. nov. (red) were collected in Lake Biwa, Japan. The detailed localities are shown in Table 1.

Figure 2. The maximum likelihood tree of 11 Semisulcospira niponica - group species calculated based on 19,767 SNPs. The numbers associated with the nodes represent values of SH-aLRT (left) / ultrafast bootstrap (right). Values of SH-aLRT higher than 80.0 and that of ultrafast bootstrap greater than 95 are indicated.

Figure 3. SVDquartets tree of Semisulcospira niponica - group populations calculated based on 19,767 SNPs. The numbers associated with the nodes represent bootstrap values.

Figure 7. Shells and opercula of Semisulcospira reticulata (A – Y) and S. nishimurai sp. nov. (Z – BF). A – F. Holotype of S. reticulata from Oki-shima Island (offshore), NSMT - Mo 39770; G – J. Hannoura, KUZ Z 4926, Z 4927; K – O. Kitafunaki, KUZ Z 4930, Z 4931; P – T. Oki-shima Island (offshore), KUZ Z 4925; U – Y. Mano, KUZ Z 4229, Z 4286; Z – AF. Holotype of S. nishimurai sp. nov. from Hannoura, KUZ Z 4935; AG – AQ. Paratypes of S. nishimurai sp. nov. from Hannoura, KUZ Z 4936 – Z 4939; AR – AT. Oura Port, KUZ Z 4945; AU – AY. Minamihama, KUZ Z 4946, Z 4947; AZ – BD. Kitafunaki, KUZ Z 4952, Z 4953; BE – BG. Oki-shima Island (coast), KUZ Z 4957. Scale bars: 10 mm (1), female teleoconch (A – C, G, K, P, S, U, Z – AB, AG, AJ, AM, AR, AU, AZ, BE), male teleoconch (J, N, AP, AX, BC), operculum (H, L, O, Q, T, V, Y, AC, AH, AK, AN, AQ, AS, AV, AY, BA, BD, BF); 2 mm (2), protoconch (D – F, I, M, R, W); 1 mm (2), protoconch (AD – AF, AI, AL, AO, AT, AW, BB, BG).

Figure 8. Radulae of Semisulcospira reticulata (A – D) and S. nishimurai sp. nov. (E – I). A. Hannoura, KUZ Z 4926; B. Kitafunaki, KUZ Z 4930; C. Oki-shima Island (offshore), KUZ Z 4925; D. Mano, KUZ Z 4229; E. Holotype of S. nishimurai sp. nov. from Hannoura, KUZ Z 4935; F. Oura Port, KUZ Z 4945; G. Minamihama, KUZ Z 4946; H. Kitafunaki, KUZ Z 4952; I. Oki-shima Island (coast), KUZ Z 4957. Scale bars: 100 μm.

Figure 9. Schematic drawings indicating generalised external features of the soft body and reproductive organs of Semisulcospira reticulata and S. nishimurai sp. nov.: A, B. Dorsal and ventral views of organs in visceral mass of mature female of S. nishimurai sp. nov. without operculum; C. External, right lateral view of pallial oviduct of S. reticulata; D. External, view of pallial oviduct of S. nishimurai sp. nov.; E. External, right upper lateral view of the prostate of S. nishimurai sp. nov.; F Internal folding structures of the prostate of S. nishimurai sp. nov. Abbreviations: bp, brood pouch; ct, ctenidium; dg, digestive gland; eg, egg; em, embryo; f, foot; inn, inner wall of brood pouch; int, intestine; kd, main kidney chamber; os, osphradium; ov, ovary; ovi, renal oviduct; pr, prostate; rcs, seminal receptacle; sg, sperm gutter; sn, snout; spb, spermatophore bursa; ss, style sac; sto, stomach; t, cephalic tentacle; vd, vas deferens. Scale bars: 5 mm.