Pomacea penai, Ampuero & Ramírez, 2023

Ampuero, André & Ramírez, Rina, 2023, Description of two new species of apple snail (Ampullariidae: Pomacea) from Peruvian Amazonia, Zootaxa 5258 (1), pp. 76-98 : 78-85

Pomacea penai sp. nov.

Figs. 3 , 4A, 4B , 5A , 6A, 6C , 7A, 7D , 8 , 9 , 10A, 10B, 10C , 11

Synonymy: Pomacea sp. 2 — Ramírez et al. 2022, fig 2B.

Type material: PERU. Holotype male MUSM 5692H . Paratypes: MUSM 5692 P, SMF 348816 (ex MUSM 5692P ), MZSP 122665 (ex MUSM 5692P ). LORETO, Maynas prov., Iquitos, flooding area of Nanay River , Nueva BellavistaNanay , 03°42'35.0”S, 73°14'55.2”W, leg. R. Chujutalli, 25/vi/2018, 8 specimens; MUSM 5709P , LORETO, Ucayali prov., Lake Huimbacocha, near Santa Rosa hamlet, Cruz Muyuna Lake , Ucayali River , 6°43'60”S 75°05'60”W, leg. I. Carrillo, 17/ii/2018, 5 specimens; MUSM 5624P , LORETO, Loreto prov., Saramuro Island in Marañon River , 4°43'18.5”S 74°57'58”W, A. Ampuero and V. Borda, 14/iii/2011, 2 specimens; MUSM 5713P , LORETO, Loreto prov., Pahuachiro Creek near Mullaca oxbow lake, Marañon River , 4°35'10.93”S 73°36'32.24”W, leg. J. Lomas, 11/vii/2021, 5 specimens; MUSM 5703P , LORETO, Maynas prov., Timicurillo near Amazon River-Indiana , 3°31'54.5”S 73°03'45.2”W, leg. R. Chujutalli, 05/i/2020, 2 specimens; MUSM 5695P , LORETO, Maynas prov., Iquitos Island in Itaya River , 03°46'20.4”S 73°14'17.4”W. Leg. J. Mozombite, 23/x/2019, 3 specimens; MUSM 5708P , LORETO, Ucayali prov., Contamana , in flooded areas by Ucayali River , 07°20'52.6”S 75°0'49.3”W, R. Ramírez et al., 08/ii/2018, 5 specimens .

Mitochondrial COI sequences are deposited into GenBank under the accession numbers MZ 351334– MZ 351346, as well as 16S rRNA, MZ 354657– MZ 354662.

Etymology: This species is named after Dr. Mario Peña, a prolific Peruvian malacologist, to honor his work on marine Mollusca in northern Peru.

Additional material examined: PERU. MUSM 5702 , SAN MARTIN, San Martin prov., fish farming pond near San Juan de Cumbaza , 06°32'06.5''S 76°22'14.3''W, leg. B. Mera & Y. Saavedra, 15/vi/2018, 5 specimens; MUSM 5698 , LORETO, Maynas prov., Allpahuayo-Mishana National Reserve-IIAP pond used for fish farming, 03°58'02.7''S 73°25'05.8''W, leg. K. Mejia & E. Aquituari, 14/v/2018, 5 specimens; MUSM 5623 , LORETO, Maynas prov., Belen Market in Iquitos , 03°46'01''S, 73°14'48''W, A. Ampuero & V. Borda, 18/iii/2011, 1 specimen; MUSM 5690 , LORETO, Maynas prov., Iquitos, Bellavista Market , 3°42'12''S 73°14'54''W, R. Ramírez, 19/ix/2017, 5 specimens; MUSM 5696 , LORETO, Maynas prov., Model market, 3°44'26.6''S 73°14'34.4''W, leg. R. Chujutalli, 12/v/2019, 1 specimen; MUSM 5693 , LORETO, Maynas prov., Moronillo oxbow lake, near Nanay River , 03°43'15.1''S 73°15'55.0''W, leg. R. Chujutalli, 09/iv/2018, 4 specimens; MUSM 5694 , LORETO, Maynas prov., Cocha in tributary of Nanay River , 03°40'0''S 73°17'06''W, leg. J. Mora, 18/ix/2017, 2 specimens; MUSM 5697 , LORETO, Maynas prov., Ushpa Caño near Itaya River , 3°46'34.16''S 73°14'12.22''W, leg. J. Pacayo & R. Chujutalli, 12/v/2019, 1 specimen; MUSM 5701 , LORETO, Alto Amazonas prov., Pampa Poza near Huallaga River , El Naranjal community, 5°13'29.58''S 75°40'21.58''W, leg. J. Sucumbio & R. Chujutalli, 21/iv/2019, 1 specimen; MUSM 5704 , LORETO, Maynas prov., Santa Victoria Community , 3°35'1.1''S 73°7'4.3''W, leg. E. Andi & R. Chujutalli, 04/ ix/19, 2 specimens; MUSM 5705 , LORETO, Maynas prov., Yanayacu Ravine near Amazonas River , 3°33'36.46''S 73°3'42.59''W, leg. R. Chujutalli, 28/iv/2018, 5 specimens; MUSM 5706 , LORETO, Maynas prov., Choro Chico oxbow lake near Los Invencibles rural village, mouth of Napo River , 3°26'15.71''S 72°42'7.12''W, leg. O. Noriega & R. Chujutalli, 20/vi/2019, 2 specimens; MUSM 5707 , LORETO, Requena prov., Carachama community near Ucayali River, 5°44'26.52''S 74°33'17.27''W, leg. R. Chujutalli, 05/vii/2019, 5 specimens; MUSM 5710 , UCAYALI, Coronel Portillo prov., Chanajao village in Yarinillal Cocha , near, Ucayali River , 8°30'43''S 74°26'20''W, leg. L. Cirano, 17/ii/2018, 5 specimens; MUSM 5712 , MADRE DE DIOS, Tambopata prov., ITA Inkaterra in "El Tubo" trail, 12°31'58.2''S 69°03'01.3''W, leg. R. Ramírez, C. Ihuaraqui, 23/xii/2017, 6 shells; MUSM 5700 , LORETO, Loreto prov., Mullaca oxbow lake, Nauta, Marañon River , 04°35'10.93''S 73°36'32.24''W, leg. J. Lomas & J. Icomena, 23/x/2019, 3 specimens.

Type locality ( Fig. 2A ): PERU. LORETO, Maynas prov., Iquitos, flooding area of Nanay River , Nueva Bellavista-Nanay (03°42'35.0''S, 73°14'55.2''W).

Diagnosis: Prostate broad proximally. Basal penis gland elongated, in dorsal sheath surface, covers medial and basal regions of the penis sheath.

Shell ( Fig. 3 ): Shell globose, medium to large (70–110 mm), solid, varied from depressed to elevated body whorls, this latter more noticeable in smaller individuals. Suture channel slightly pronounced. Sculpture marked by fine growth lines, often alternated by growth arrests, and with malleations in some specimens. Elliptical to ovate aperture, inner lip and columella ochre to orange, with interior ochre iridescent. Periostracum greenish brown to dark brown, with light brown spiral bands. Umbilicus wide and deep. Measurements in mm. Holotype, height: 77.76, width: 63.68, aperture height: 58.14, aperture width: 43.32. N=182, (average±standard deviation, minimum– maximum) height: 73.9±17.4, 43.6–114.4; width: 62.1±15.8, 35.0–98.4; aperture height: 53.7±12.6, 33.5–83.0, aperture width: 37.9±10.1, 21.9–61.7.

Operculum ( Figs. 4A, 4B ): Operculum horny and reniform, covering entire opening. Outer surface with concentric growth lines left to marginal central area. Smooth inner surface, insertion mark elliptical, close to central left margin; occupying ~3/5 of the inner surface.

External anatomy ( Figs. 5A , 8B ): Dark to light grey foot and sole, some specimens with beige sole. Cephalic tentacles elongated; ommatophores with wide base ~1/6 length of tentacles, short with dark eyes. Snout broad, with pair of lateral labial palps, with half of length of cephalic tentacles. Right lobe wide and short, left lobe about 4 times longer than previous one, with margins folded dorsally (siphon). Foot dorsoventrally flattened. Glandular furrow, with fine edges, occupying ~3/5 of anterior pedal margin. Columellar muscle covering ~1/4 of body whorl.

Mantle cavity ( Figs. 6A , 8A, 8C ): Mantle ( Figs. 6A , 8A ) border thick with undulations.Mantle cavity occupying almost half of body whorl. Osphradium ( Fig. 8C ) elongated and laterally compressed, base broad and elevated at its proximal region. Lung sac long and wide, occupying ~1/3 of mantle cavity, with muscular walls, and internal walls highly vascularized. Ctenidial vein between gill and lung sac, thickening near pericardial region. Ctenidial filaments triangular, distal region slightly curved to left. Rectum lateral to ctenidium. Anterior kidney on posterior region of mantle cavity. Gonoduct parallel to rectum, under urinary gutter. Right margin of mantle cavity in males occupied by penis sheath ( Fig. 9 ). In females, a bulging portion located on right margin, corresponding to pallial oviduct.

Circulatory and excretory systems ( Figs. 6A , 8A, 8D ): Ctenidial vein, short with thin walls ( Fig. 8A ). Pericardium cavity small. Auricle short and slender. Ventricle triangular with wall thicker than the auricle. These two with a dull orange coloration and connected by a short vessel. Bulbous aorta emerging from posterior ventricular region, bifurcating to the posterior and anterior aorta. Anterior aorta broad, connecting to the light-yellow ampulla. Esophageal artery originating from ampulla, close to anterior aorta. Dark brown posterior kidney ( Fig. 8D ), slightly concave and highly vascularized, with acute curvature and narrow and blunt anterior region. Anterior kidney beige colored, broad and triangular, connected to posterior kidney by duct located in left of latter. Two sets of lamellae inside anterior kidney. Nephropore in posterior region of anterior kidney.

Digestive system ( Figs. 6C , 7A, 7D , 8A, 8E, 8F ): Buccal bulb pyriform with red musculature ( Figs. 6C , 8E ). Radula (N=4) taenioglossate, with ~26–41 rows ( Figs. 7A, 7D ). Rachidian tooth rectangular with concave base and lateral margins; central cusp rounded with protruding pointed tip; lateral cusps rounded and of ~2/7 length of central peak. Lateral teeth, with triangular central cusp, and 2 small outer lateral cusps around it. Inner marginal teeth with two triangular cusps, internal cusp of ~1/5 length of outer cusp; outer marginal cusps with bulged tips. After dorsal folds, lateral to esophagus, two broad and short esophageal pouches, slightly rounded at its distal region ( Figs. 6C , 8E ). Pair of salivary glands alveolate and compacted, lateral to digestive tract. Salivary ducts inserted into bulb dorsal surface, ending in anterior region of longitudinal folds. After these pouches, esophagus widening forming crop, bulged in right side. Gastric muscle ( Fig. 8F ) elongated. Stomach divided into dorsal and ventral chambers by reduced septum.Ventral chamber twice size of dorsal one, receiving two ducts of digestive gland in its ventral surface. Walls of ventral chamber with red muscles, possess series of transverse folds. Stomach pouch divided internally by transverse folds posterior to dorsal chamber. Intestinal groove whose left and right margins show major and minor typhlosole respectively. At its origin, major typhlosole distinguishable by having small and rectangular fold. Reduced sorting area lateral to this, slightly expanded. Distal region of intestinal groove with elongated caeca bordering sphincter. Intestine U-turned and bordering kidney cavity to enter by left margin. Within cavity, intestine with 4 loops connected to right side of posterior kidney wall by connective tissue. Rectum ( Fig. 8A ) running longitudinally along right side of the mantle cavity, parallel to urinary gutter and gill, ending close to rectal papillae, located near left lobe of mantle.

Reproductive system: Female ( Figs. 6A , 8A ). Ovary ivory-white, with agglomerated acini. Acini join forming visceral oviduct, connected to pallial oviduct in its ventral anterior third. Pallial oviduct ( Fig. 6A ) embedded in light olive parenchymal tissue of albumen gland-capsule gland complex. Visceral oviduct connecting seminal receptacle ( Fig. 8A ), reniform and large. Albumen gland lumen flattened, expanded proximally and distally. Copulatory bursa, ~1/3 of volume of seminal receptacle, adjacent to this and joining it by narrow channel. Ventral channel joins seminal receptacle and running through capsule gland. Seminal receptacle and albumen gland lumen connected to proximal lumen of capsule gland. This latter presents spiral disposition, occupying ~2/3 of pallial oviduct. Capsule gland lumen tapering distally. Vagina ( Figs. 6A , 8A ) narrow, thick-walled and red muscular folds inside, with small dorsal channel throughout its length, running longitudinally along right side of mantle cavity and passes beneath urinary gutter. Female opening small, adjacent to rectal papilla. In some specimens, vestigial penis sheath, elongated, with small groove, and penis like structure occurs in mantle cavity.

Male ( Fig. 9 ). Testis beige colored, occupying approximately first 2 ½ whorls. Spermiduct in basal region of testis, near pericardium region, connected to proximal region of cylindrical and flattened seminal vesicle at its left margin. Prostate ( Fig. 9C ) broad in its anterior region, running longitudinally along mantle cavity, decreasing its diameter toward posterior region. Prostate inserted below anal papilla, continues with small outgrowth of tissue. Penis pouch ( Figs. 9A, 9B ) composed of translucent membrane, and penis rolled seen through. Penis bulb solid, occupies ~2/3 of penis pouch. Penis cylindrical and long, slightly decreasing diameter at distal portion. Penis pouch losing its thickness and forms membrane at base of penis sheath, which occurs in left anterior region of mantle cavity. Penis sheath elongated, slightly curved to right, with bulged base. Two glands in dorsal region of sheath: apical gland, ~1/3 of length of sheath, with rough surface; basal gland elongated, covering also middle region. Basal ventral gland embedded in sheath, with small opening slit on outer sheath face. Notch in middle of penis sheath. Throughout penis sheath occurs groove covered by thin membrane originating on its left side.

Eggs ( Figs. 10A, 10B, 10C ): Clutch (N=4) elongated, calcareous eggs disposed in a tight cluster, with polygonal shapes, similar to honeycomb, light to lime green colored newly hatched, turning with the time to pale green; laid on vegetation or substrate above water; number of eggs approximately 400, average egg diameter ~ 4.24 mm.

Shell variability ( Fig. 11 ): Observed shells (N=200) varied from an elongated body whorl morphotype to a compressed one. PCA for the 19 landmarks did not show geographical differentiation, with all groups overlapping in the morphospace. These did not group by locality, where every locality contained most of the shell shapes, a case of extreme intrapopulation variability. First and second principal components explained together 38.32% of the variation. Shape variation across the first principal component showed an expanded aperture relative to the body whorl and a less pointed shell at the positive end of the axis; towards negative end of axis, shells have higher spires and elongated apertures. Meanwhile, second principal component displayed a rounded aperture, depressed body whorl and immersed spire at the positive end of the axis, and an elongated aperture and body whorl at the end of the negative axis. From here, we can categorize two types of shells: one group with pointed spires and other one with immersed spires.

Procrustes ANOVA showed significant differences among localities (F: 4.2457, p<0.001). Pairwise comparisons found non-significant differences in most cases, except for following pairs: Amazonas /High Ucayali, Amazonas / San Juan de Cumbaza, High Ucayali /Nanay, Nanay/ San Juan de Cumbaza (p<0.05) (Supplementary Table 1 provides the pairwise results).

Distribution and habitat: Commonly found in temporary flooded areas near Amazon River tributaries, and oxbow lakes. Snails found at the bottom of water bodies, even near populated areas. Fishers find them in their fish traps left overnight at an approximate depth of one meter in small rivers.

Remarks: Pomacea penai sp. nov. has been identified as Pomacea haustrum ( Reeve, 1856) since Weyrauch’s collections (1940s) from Ucayali River (NMW.Z.1981.118.03479) ( Pain 1960); Haas (1947) identified them as P. haustrum immersum (MUSM 520). Rawlings et al. (2007) sequenced one specimen from Ucayali River (16S rRNA) housed in the Field Museum (FMNH 223530) and found it to cluster with specimens of one of the introduced species from Florida, USA, which laid green eggs. The following authors highlighted the latter apple snail as a different species from P. haustrum ( Hayes et al. 2012; Cowie et al. 2017). Ramírez et al. (2022) found in a COI phylogeny a monophyletic group formed by Rawling’s specimen along with samples of P. penai sp. nov. from around Iquitos, Peru.

Furthermore, P. penai sp. nov. internally differs from P. haustrum in possessing a longer penis sheath gland that occupies middle and basal region, a bulged proximal region of prostate, and laying green eggs, in contrast with the pink ones of P. haustrum described by Lopes (1955).

Pomacea penai sp. nov. could be confused with Pomacea maculata Perry, 1810 as it shares many conchological characters, mainly in large specimens. Pomacea penai sp. nov. shells usually have a higher spire than P. maculata . Here we should add that the immersed spire morphotype is not a condition only found in P. penai sp. nov., due to its presence in other species, as P. reevei sp. nov., described in this work, and also P. maculata ( Hayes et al. 2012) . In addition to the anatomical characters mentioned below, P. penai and P. maculata were separated by a genetic distance ranging from 13.4 to 14.6% (COI).

Regarding the internal anatomy, P. penai sp. nov. has developed apical and basal penis sheath glands, whereas in Pomacea bridgesii ( Reeve, 1856) group species such as Pomacea scalaris (d'Orbigny, 1835) and Pomacea diffusa Blume, 1957 ( Hylton-Scott 1957; Cowie et al. 2006), apical gland is absent and basal gland is reduced. P. maculata and Pomacea curumim Simone, 2004 penis sheath glands arrangement resembles P. penai sp. nov. ( Simone 2004; Hayes et al. 2012), from which it differs in the elongated basal sheath gland, compared with the smaller basal and medial glands in P. maculata and P. curumim respectively. Pomacea penai sp. nov. has similarities with the proximal region of prostate and the curved penis sheath of specimen determined as P. haustrum illustrated by Lopes (1955) but differing in the proximal bulky region of the prostate. Polygonal eggs also have been reported in other Pomacea species from P. bridgesii group, such as P. scalaris and P. diffusa , but differ in their orange to brown colors ( Cowie et al. 2006). Green colored eggs are described for Pomacea glauca (Linnaeus, 1758) , Pomacea pyrum (Philippi, 1851) , Pomacea decussata (Moricand, 1836) , Pomacea nais Pain, 1949 ( Cowie 2002) , and Pomacea nobilis ( Reeve, 1856) ( Ramírez et al. 2022) .

Circulatory and excretory system of P. penai sp. nov. resembles Pomacea canaliculata (Lamarck, 1822) , both with a broad anterior kidney and the independent origin of esophageal artery from ampulla; anterior kidney of P. penai sp. nov. is similar in shape to P. curumim . Concerning radula, concave rachidian base of P. penai sp. nov. is similar to P. maculata , and stout central cusp and lateral denticles to P. canaliculata . Compared to P. maculata , P. penai sp. nov. has a reduced stomach septum.

Figures

FIGURE 2. Type localities of Pomacea penai sp. nov. and Pomacea reevei sp. nov. Flooding area of Nanay River, Nueva Bellavista—Nanay in Loreto department, during (A) wet and (B) dry season. (C) Map showing collection sites in Iquitos city, that includes type locality (asterisk), Bellavista Market (circle), Moronillo (triangle), and Isla Iquitos (square); collection sites included areas near and within populated areas, surrounded by flood zones and wetlands. (D) Kichwa Cocha, near Rango Isla populated center, Maynas province, Loreto department.

FIGURE 3. Frontal and dorsal views of Pomacea penai shells. (A) MUSM 5692H (h=77.76 mm); (B) MUSM 5692P (h=70.32 mm); (C) MUSM 5709P (h=70.98 mm); (D) MUSM 5702M (h=66.50 mm); (E) MUSM 5624P (h=93.42 mm); (F) MUSM 5704M (h=109.02 mm).

FIGURE 4. Outer and inner views of Pomacea spp. nov. opercula: Pomacea penai: (A) holotype MUSM 5692H and (B) paratype MUSM 5692P; Pomacea reevei: (C) holotype MUSM 5723H and (D) paratype MUSM 5723P. Scale bars = 10 mm.

FIGURE 5. Living specimens of (A) Pomacea penai MUSM 5713P and (B) Pomacea reevei MUSM 5723P.Scale bars = 20 mm.

FIGURE 6. Visceral mass showing pallial cavity roof, and foregut in lateral view of (A, C) Pomacea penai and (B, D) Pomacea reevei. Abbreviations: am, ampulla; ct, ctenidium; dg, digestive gland; ed, esophageal diverticulum; es, esophagus; in, intestine; ls, lung sac; mb, mantle border; os, osphradium; po, pallial oviduct; pk, posterior kidney; rct, rectum; rs, radular sac; sg, salivary gland; st, septum; ve, ventricle; v, vagina. Scale bars = 10 mm.

FIGURE 7. Radulae of (A) Pomacea penai MUSM 5692P, and Pomacea reevei (B) MUSM 5715P, (C) MUSM 5627P in SEM. Drawings of the radular row of P. penai (D) and P. reevei (E). Abbreviations: R: rachidian tooth; L, lateral tooth; M1, inner marginal tooth; M2, outer marginal tooth. Scale bars = 500 μm.

FIGURE 8. Anatomy of female Pomacea penai: (A) ventral view of female pallial cavity roof, pericardic cavity opened, pallial oviduct turned aside and schematic view showing internal structures; (B) frontal view of head–foot; (C) osphradium morphology detailed; (D) outline of kidney morphology; (E) lateral right view of foregut; (F) stomach dorsally opened. Abbreviations: agl, albumen gland; ak, anterior kidney; am, ampulla; an, anus; au, auricle; bc, copulatory bursa; cgl, capsule gland; ce, cephalic tentacle; dd, digestive gland ducts; ed, esophageal diverticulum; es, esophagus; ey, eye; fo, female opening; gv, wall of gastric ventral chamber; gm, gastric muscle; ic, intestinal caecum; ig, intestinal groove; in, intestine; la, labial palp; lnl, left nuchal lobe; ls, lung sac; mb, mantle border; mo, mouth; om, ommatophore; op, operculum; os, osphradium; pa, parenchymal tissue of albumen gland-capsule gland complex; pgf, pedal glandular furrow; pk, posterior kidney; pn, pneumostome; rcs, seminal receptacle; rct, rectum; rnl, right nuchal lobe; rs, radular sac; sa, sorting area; sg, salivary gland; sn, snout; so, sole; sp, stomach pouch; st, septum; t1, major typhlosole; t2, minor typhlosole; t1f, major typhlosole fold; t2f, minor typhlosole fold; ug, urinary gutter; ve, ventricle; vp, vestigial penis sheath; v, vagina. Scale bars = 5 mm.

FIGURE 9. Male reproductive system of Pomacea penai: penis sheath externally deflected of (A) fresh MUSM 5700M and (B) fixed specimen MUSM 5692H, and (C) mantle deflected showing prostate and seminal vesicle (marked with dashed lines). Abbreviations: an, anus; asg, apical sheath gland; bsg, basal sheath gland; ct, ctenidium; os, osphradium; pb, penis bulb; pe, penis; pp, penis pouch; prs, prostate; ug, urinary gutter; vs, seminal vesicle. Scale bars = 10 mm.

FIGURE 10. Oviposition and eggs in Pomacea spp. (A) Female Pomacea penai and (D) Pomacea reevei laying eggs; egg clutches of (B) P. penai and (E) P. reevei; habitats where egg clutches of (C) P. penai and (F, G) P. reevei were found. Scale bar = 20 mm.

FIGURE 11. Shell shape variation of Pomacea penai across localities based on principal component analysis (PCA) of 19 landmarks. Most extreme individuals and shape deformation associated with components are illustrated near the respective