Pomacea occulta, Salazar-Vallejo, 2023

Yang, Qian-Qian & Yu, Xiao-Ping, 2019, A New Species of Apple Snail in the Genus Pomacea (Gastropoda: Caenogastropoda: Ampullariidae), Zoological Studies 58 (13), pp. 1-7 : 3

Pomacea occulta nov. sp.

( Fig. 1 ) urn:lsid:zoobank.org:act:95B8BA21-C410-4135-B743-FC1C8698D6F2

Holotype: FG 609800 in NZMC, male, collected from a cultivated Zizania latifolia (wild rice) field, Hemudu town, Yuyao city, Zhejiang Province, 121°10'22"E, 30°02'35"N, 29 August 2018. Collectors: Qian-Qian Yang, Xiao-Ping Yu, and Ai-Zhong Qian.

Paratypes: 5 females, FG 609801, YYHMD 18082920, FJFZ 18082007, TZWL 17070922, and TZWL 17070924; 5 males, YYHMD 18082903, YYHMD 18082917, YYHMD 18082918, HMD19, and FJFZ 18082009. The FG and YYHMD specimens had the same collection data as the holotype. The FJFZ specimens were collected from lotus ponds in Fuzhou city, Fujian Province (119°14'E, 26°05'N), by Bao- Zhen Tang and Cheng-Jun Ma on 20 August 2018. The TZWL specimens were collected from a paddy field in Wenling city, Zhejiang Province (121°21'E, 28°26'N), by Su-Wen Liu and Qian-Qian Yang. FG 609801 is stored in NZMC, and all other paratypes are stored in BIQ.

Seven egg clutches with the same collection data as the holotype were examined.

Mitochondrial COI sequences for the type specimen and hatchlings from each of the clutches deposited into GenBank under the accession numbers MK756260 - MK756277 .

Description: The following description is modeled on the descriptions of P. maculata and P. canaliculata of Hayes et al. (2012) to facilitate comparison of P. occulta nov. sp. with those two species.

Adult shell: Thick, generally smooth with an uneven surface of channeled sutures and spiral, lined, shallow malleation, axial growth lines and frequent periodic growth arrests, adult shell height ranging from 54 to 63 mm, width from 45 to 58 mm. Periostracum thick, variable in color from reddish to dark brown. Spiral bands thick with interphase colors of greenish and brown or reddish. Shoulder angulate. Spire height low, with ratios of spire height to overall shell height ranging from 0.08 to 0.12. Aperture ovoid to kidneyshaped. Inside of pallial lip pigmented with variable colors from yellow to reddish.

Operculum: Corneous, moderately thick, flexible, thinning towards the parietal edge. Color variable from yellow to dark brown, lightening from the nucleus to the edge. Sexually dimorphic, uniformly concave in females, concave at nucleus and convex towards the margins in males.

Radula : 8.8-12.8 mm long, 3.4 mm wide, with ~23-33 rows of teeth (mean = 28; N = 6 adults). Each row with one central tooth, one lateral tooth and two marginal teeth (tooth type: 2·1·1·1·2). Central tooth elongated, approximately 2 times broader than tall, with a main trapezoidal cusp. Rachidian base is slightly concave. Three smaller cones present on each side of central cone. Width of first cusp of central tooth 0.44- 0.52 mm. Lateral tooth with sharp central cusp of straight edges located on each side of central tooth, flanked by three small cones. One of these small cones faces central tooth. The other two small cones face marginal teeth, with outer one very small and nonobvious. Two elongated triangular marginal teeth are located on each side of lateral teeth, ending in two sharp tips each. Outer marginal teeth approximately one third the breadth of inner marginal teeth.

Kidney: Kidney consisting of larger posterior chamber and smaller anterior chamber. Posterior chamber broad semicircle shaped, interconnected with anterior chamber on straighter edge at nearly two-thirds on the right. Left tip of the straight edge forms narrow intersection angle. Arc-wise edge with narrow cleft on right side. Anterior chamber triangular.

Penis sheath: Penis sheath tapering from base. Apical and medial sheath glands present. Apical gland large, comprising distal half of sheath dorsal surface, with top elliptical protuberance and stratified folds below. Medial sheath channel starts at base and terminates at base of apical gland on dorsal surface. Medial gland ovoid, located in medial sheath channel between base and tip.

Eggs: Eggs are laid individually and form a clutch above the water line. The eggs are bright pink-reddish with calcareous shells, which harden after a couple of hours. The color eventually turns pale pink before hatching. It takes ~14 days from oviposition to hatching at 25 ± 1°C and a relative humidity of 65 ± 5% under a 16:8 h light: dark cycle. Egg number per clutch varies from 87 to as many as ~1000, with an individual egg diameter of 2.38 mm on average based on measurement of 60 individuals. The height of one-day-old hatchlings is ~ 2.23 mm; the first whorl ~ 2.11 mm in diameter.

Etymology: The specific epithet occulta is a Latin adjective meaning hidden, concealed, or secret, which was chosen in reference to the misidentification and cryptic invasion of this species in the past.

Distribution: Presently widely distributed in the southern provinces of China. However, as an invasive species, the native distribution range of P. occulta nov. sp. in South America remains unknown.

Figures

Fig. 1. Key morphological characteristics of Pomacea occulta nov. sp. (A) Shell morphology of FG 609800 (upper) and FG 609801 (lower). (B) Opercula external and internal surfaces of FG 609800 (left) and FG 609801 (right). (C) Radular morphology of FG 609800. (D) Male reproductive morphology of YYHMD 18082917. (E) Outline of kidney morphology. (F) Egg morphology of two clutches. (G) Apertural view, apical view, and embryonic whorl close-up of the shells of 1-day-old hatchlings. Abbreviations: apsg, apical penis sheath gland; mpsg, medial penis sheath gland; ak, anterior kidney; pk, posterior kidney. Scale bars: A, B = 1 cm; C = 100 µm; D = 1 mm; E = 2 mm; F = 5 mm; G = 300 µm.