Liloa porcellana ( Gould, 1859 )

Too, Chin Chin, Carlson, Clay, Hoff, Patty Jo & Malaquias, Manuel António E., 2014, Diversity and systematics of Haminoeidae gastropods (Heterobranchia: Cephalaspidea) in the tropical West Pacific Ocean: new data on the genera Aliculastrum, Atys, Diniatys and Liloa, Zootaxa 3794 (3), pp. 355-392 : 385-386

Liloa porcellana ( Gould, 1859)

Atys porcellana Gould, 1859: 138 . Sowerby 1870: pl. 5, sp. 30. Johnson 1964: 130, pl. 12, fig. 13.

Atys (Alicula) porcellana — Pilsbry 1895: 268, pl. 28, fig. 23. Kobelt 1896: 26, pl. 8, fig. 11.

Haminoea olopana Pilsbry, 1921: 369 , fig. 8b.

Liloa porcellana — Habe 1952: 151, pl. 21, figs 20, 22, 25. Lin 1997: 106, pl. 10, fig. 3. Qi 2004: 147, pl. 83, fig. O.

Type locality. Kagoshima Bay , Japan .

Material examined. Kagoshima, Japan, 1 shell examined (holotype), USNM 1357 , H = 12 mm . Mariana Islands, Guam, 3 spcs dissected, UF 299895, H = 9.7–10 mm; the Philippines, 1 spc. dissected, MNHN, Paris (S6/ OT926 ), H = 7.8 mm. Maui, Hawaii, 1 spc dissected, ZMBN 89712 , H = 4.2 mm. Maui, Hawaii, 1 shell examined, ZMBN 89712 , H = 2.8 mm .

Animal ( Figs 1K, L ): Body whitish-translucent, white dots scattered over the body, more dense at cephalic shield; eyes visible.

Shell ( Fig. 3E–G , 18A ): Maximum height 19 mm; whitish translucent; fragile, thin, elongated-cylindrical, both anterior and posterior ends truncated, anterior end narrower; spire sunken, outer lip thin; spiral grooves covering entire shell in adults (which become closer towards the ends) and only visible at shell ends in juveniles; faint axial lines present irregularly.

Jaws ( Fig. 18B ): Present, crescent shape, jaw rodlets with 6-10 denticles.

Radula ( Figs 18C–F ): Radular formula at mid-point 18–20 x 7–4.1.1.1.4–7; median tooth with broad base, triangular central cusp prominent, small triangular lateral cusp; inner lateral tooth hook-shaped, base with semicircular projection outwardly, groove along outer margin, weak denticulation along groove; outer lateral teeth hook-shaped, base with semi-circular projection outwardly, weak groove along outer margin, size decreases outwardly.

Gizzard plates ( Figs 19A, B ): Three gizzard plates; almost equal size from anterior to posterior, 10–11 ridges, covered by rods with pointed tips along top edge of ridges, dense tiny rods with pointed tips on both anterior and posterior sides of ridges, gaps between ridges smooth.

Male reproductive system ( Fig. 19C ): Total length 4.2 mm (H = 10 mm). Formed by three parts: prostate, seminal ducts and penial region; prostate oval, bilobed, proximal lobe smaller, opaque-brownish, distal lobe lightyellowish; translucent duct connects prostate to creamy-yellowish striated (?)glandular region, which opens distally to first seminal duct that possesses hook-like posterior end, and proximally opens to second seminal duct, translucent, coils twice before connecting to penial region; penial region oval, translucent, with convoluted opaqueyellowish inner glandular duct connecting to genital opening.

Ecology. Sandy bottom below 29 m deep ( Lin, 1997; present study).

Geographical distribution. Japan, China, Taiwan, the Philippines, Guam, Big Island, Maui, Oahu and French Frigate Shoals of Hawaii ( Qi 2004; present study).

Remarks. There are a few conflicting features about the description of this species. Some authors referred to Liloa porcellana with spiral grooves only at both ends of shell ( Pilsbry 1895; Habe 1952; Lin 1997). However, the original description states that spiral grooves are more visible at both ends, which does not imply that the middle part of the shell is smooth ( Gould 1859). The study of the holotype (USNM 1357) confirmed the presence of spiral grooves throughout the shell but they are in fact faint in the middle part of the shell. Larger specimens that we examined (H ≥ 4.2 mm) have spiral grooves along the entire shell, with distance between grooves decreasing towards both ends; whereas the small specimen (H = 2.8 mm) have spiral grooves only at both ends of the shell ( Figs 1K–L , 2E–G ). The holotype of Liloa porcellana has a narrower posterior end compared to its anterior end. However, this was not exactly the case for the shells examined during this study, but differences in shell height may explain this phenotypic difference, since none of our specimens was as large as the holotype (H = 12 mm). The anatomical features of our specimens match those described by Habe (1952).

This species can be distinguished from Liloa curta by a slender-elongated shell shape and spiral grooves that become closer towards the ends of the shell, although the latter feature may vary ontogenetically. Also, Liloa porcellana only has spiral grooves in the mid-region of the shell in adult specimens; in juveniles, those can be faint or absent. Both species have similar radula. The gizzard plates of Liloa porcellana have fewer and far apart ridges than Liloa curta where the ridges are numerous and tight together. Moreover, the male reproductive system of Liloa porcellana has a longer and twisted secondary seminal duct ( Fig. 19C , sd 2) and a conspicuous duct connecting the prostate to a globose glandular region whereas in Liloa curta the prostate almost sits on top of the globose glandular region.

Figures

FIGURE 1. Live images. A. Aliculastrum cylindricum (Koumac, northern New Caledonia; H = 28 mm, MNHN, Paris), B. Aliculastrum debilis (Maui, Hawaii; ZMBN 81658; H = 9 mm), C. Aliculastrum parallelum (Guam; UF 374138; H = 19 mm), D. Atys multistriatus (Guam; UF 374136; H = 7 mm), E. Atys pittmani nov. sp. (Maui, Hawaii; ZMBN 81673; H = 10 mm), F. Atys semistriatus (Maui, Hawaii; ZMBN 81656; H = 6 mm), G. Atys ukulele nov. sp. (Maui, Hawaii; ZMBN 89710; H = 5.4 mm), H. Diniatys dentifer (Guam; UF 374130; H = 9 mm), I. Diniatys dubia (Guam; UF 299907; H = 12.7 mm), J. Liloa curta (Guam; UF 374131; H = 15 mm), K. Liloa porcellana (Maui, Hawaii; ZMBN 89712; H = 4.2 mm); L. Liloa porcellana (Maui, Hawaii; ZMBN 89712; H = 2.8 mm). Image A, courtesy of W. B. Rudman; Images B, E–G, K, L, courtesy of C. Pittman.

FIGURE 2. Shells. A. Aliculastrum cylindricum (the Philippines; MNHN, Paris (S3/ OT236); H = 22 mm), B. Aliculastrum cylindricum (New Caledonia; MNHN, Paris; H = 13.7 mm), C. Aliculastrum debilis (the Philippines; MNHN, Paris (OT834); H = 4.5 mm), D. Aliculastrum parallelum (Guam; UF 374138; H = 10 mm), E. Atys multistriatus (Guam; UF 374136; H = 5.3 mm), F. Atys pittmani nov. sp. (Maui, Hawaii; ZMBN 81673; H = 10 mm); G. Atys semistriatus (Tahiti; ZMBN 87082; H = 4.1 mm). Scale bar: 1 mm.

FIGURE 3. Shells. A. Atys ukulele nov. sp. (Maui, Hawaii; ZMBN 89711; H = 4.6 mm), B. Diniatys dentifer (the Philippines, MNHN, Paris (B17/ OT793); H = 3.5 mm), C. Diniatys dubia (Guam; UF 299907; H = 7.5 mm), D. Liloa curta (the Philippines; MNHN, Paris (S12/ OT575); H = 3.1 mm), E. Liloa porcellana (Guam; UF 299895; H = 6.7 mm), F. Liloa porcellana (Maui, Hawaii; ZMBN 89712; H = 4.2 mm), G. Liloa porcellana (Maui, Hawaii; ZMBN 89712; H = 2.8 mm). Scale bar: 1 mm.

FIGURE 18. Shell and anatomy of Liloa porcellana. A. Detail of middle part of shell. B. Detail of jaw. C. Front view of anterior part of radula. D. Detail of median tooth at the middle part of radula. E. Denticulation on inner lateral tooth at right side of radula. F. Detail of outer lateral teeth at left side of radula. Scale bars: A = 100 µm; B = 2 µm; C, F = 20 µm; D, E = 20 µm. A, B: UF 299895, H = 9.8 mm; C–F: UF 299895, H = 10 mm.

FIGURE 19. Anatomy of Liloa porcellana. A. Top view of gizzard plate. B. Rods on middle ridges of gizzard plate. C. Male reproductive system. go, genital opening; (?) gd, (?) glandular duct; pr, prostate; ps, penial sheath; sd 1, first seminal duct; sd 2, second seminal duct. Scale bars: A = 100 µm; B = 20 µm; C = 1 mm. A–C: UF 299895, H = 10 mm.