Cerithidea moerchii
Creators: name: Reid, David G.
Publisher: name: Zenodo
Year: 2014
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Potamididae
Cerithidea
Cerithidea moerchii

description: Cerithidea moerchii (A. Adams in G.B. Sowerby II, 1855)
(Figures 2 E, 14B, 15J–AA)
Cerithium mörchii A. Adams in G.B. Sowerby II, 1855: 888, pl. 186, fig. 283
(no locality, here corrected to Yaeyama Is, Okinawa Pref., Japan; 2 syntypes NHMUK 20060321, Fig. 15 U, seen).
Cerithidea moerchii — Sowerby, 1866: sp. 18, pl. 3, fig. 18. Kuroda, 1928: 38 (as mörchii). Hirase, 1934: 53, pl. 84, fig. 8 (as mörchii). Kuroda & Habe, 1952: 44 (as morchii). Higo et al., 1999: 87 (as morchii). Reid et al., 2013: figs 1 (phylogeny), 2 (map).
Potamides (Cerithidea) moerchii — Tryon, 1887: 163, pl. 33, fig. 68 (as mörchi). Iwakawa, 1919: 76 (as morchi).
Cerithium (Cerithidea) moerchii — Kobelt, 1893: 154, pl. 29, fig. 3 (Cecalupo 2005: pl. 32, fig. 12).
Cerithidea (Cerithidea) moerchii — Oyama, 1959: figs 4, 11 (as mörchii).
Cerithidea rhizophorarum moerchii — Habe & Kosuge, 1967: 34, pl. 13, fig. 16 (as morchii). Habe, 1968: 38, pl. 11, fig. 19 (as rhizoghorarum morchi). Higo, 1973: 59 (as morchii). Okutani, 1986: 80, fig. (as morchi). Higo & Goto, 1993: 105 (as morchii).
Cerithidea obtusa var. β rhizophorarum — Crosse & Fischer, 1864: 332 (not A. Adams, 1855).
Cerithidea rhizophorarum — Dautzenberg & Fischer, 1905: 134 –135 (in part, includes C. rhizophorarum; as rhizoporarum). Hirase, 1934: 53, pl. 84, fig. 7 (as rhizoporarum). Kuroda & Habe, 1952: 44. Habe & Kosuge, 1967: 34, pl. 13, figs 13–15. Habe, 1968: 38, pl. 11, fig. 23. Kuroda et al., 1971: 101, pl. 16, figs 1, 2. Higo, 1973: 59. Wells, 1985: 145, pl. 1 H. Okutani, 1986: 80, figs. Fan 1989: 38, pl. 5, fig. 25. Choe, 1992: 309 –310, pl. 64, fig. 101a, b. Higo & Goto, 1993: 105. Higo et al., 1999: 87. Lee & Min, 2002: 103. Ma, 2004: 37, pl. 016C (not 016A). Min et al., 2004: 129, fig. 217-1, 217-2. Kojima et al., 2006: 525 –535, fig. 2c, d. Reid et al., 2008: 680 –699, figs 1, 2 (phylogeny). Zhang, 2008: 59, text fig. Li & Huang, 2012: 152, text fig. (All not A. Adams, 1855.)
Potamides (Cerithidea) rhizophorarum — Iwakawa, 1919: 76 (not A. Adams, 1855).
Cerithidea (Cerithidea) rhizophorarum — Oyama, 1959: figs 5, 12. Fukuda, 1996: 21 –22. Fukuda, 2000: 106 –110, 135, fig. 5.4a (shell), fig. 5.5a (living animal). Hasegawa, 2000: 133, pl. 66, fig. 1a, b. Cecalupo, 2006: 136 (in part, includes C. rhizophorarum, C. decollata, C. weyersi). Thach, 2007: 60, pl. 9, fig. 183. Hong et al., 2010: 258, fig. 4c. Kimura & Fukuda, 2012: 29, text figs. a, b, d, e (shells), c (living animal). (All not A. Adams, 1855.)
Cerithidea rhizophorarum var. freytagi — Dautzenberg & Fischer, 1905: 135 (in part, includes C. rhizophorarum; as freitagi; not Kobelt, 1893).
Cerithidea obtusa — Grabau & King, 1928: 223 –224, pl. 9, fig. 95 (not Lamarck, 1822).
Cerithidea (Cerithideopsis) scalariformis — Cecalupo, 2005: 318, pl. 32, fig. 12 (not Say, 1825). Cecalupo, 2006: 104 (in part, includes C. balteata; not Say, 1825).
Cerithidea ornata — Li & Huang, 2012: 152, fig. (as ornate; not Sowerby, 1855).
Taxonomic history. For more than a century this species has been most familiar under the incorrect name C. rhizophorarum (here shown to be a distinct species, endemic to the Philippines). The name C. moerchii was not, however, forgotten. In the Ryukyu Islands and Taiwan the shells are small with coarse ribs, and C. moerchii was based on this form. Early Japanese authors identified the larger mainland form as C. rhizophorarum and used C. moerchii for the smaller island form, considering it to be a distinct species (Iwakawa 1919; Kuroda 1928; Hirase 1934; Kuroda & Habe 1952; Oyama 1959; Higo et al. 1999) or subspecies (Habe & Kosuge 1967; Habe 1968; Higo 1973; Okutani 1986; Higo & Goto 1993). More recently, C. moerchii has been considered only a “geographical form” (Hasegawa 2000: 133) and this was supported by the lack of genetic differentiation between samples from mainland Japan and the Ryukyu Islands (Kojima et al. 2006; Reid et al. 2008, 2013). The name C. rhizophorarum has since been widely applied in Japan, China, Korea and Vietnam (e.g. Ma 2004; Min et al. 2004; Thach 2007; Zhang 2008; Kimura & Fukuda 2012; Li & Huang 2012), but C. moerchii has now been reinstated as the valid name for this species (Reid et al. 2013).
The name moerchii first appeared in Sowerby’s (1855) monograph of Cerithium, with its authorship attributed to A. Adams. In his introduction, Sowerby (1855: 848) acknowledges Adams “for his kindness in permitting me the full use of his manuscripts on the present genus, of which he was preparing a monograph”. As noted earlier (see Taxonomic history of C. balteata), Sowerby employed only the single genus Cerithium for all members of the modern families Cerithiidae, Potamididae, Batillariidae and others, whereas Adams employed a finer division, including the genus Cerithidea. Adams’ (1855) monograph of Cerithidea was in fact published just before Sowerby’s work appeared (Petit 2009). It is unclear whether Sowerby saw this completed text or only its manuscript, but he certainly relied on Adams’ work, because he used most of Adams’ new names and copied some of his descriptions. It is curious, therefore, that Cerithium moerchii, attributed to Adams, appears only in Sowerby’s monograph and not in that of Adams. In one other case (see discussion of Cerithium ornatum in Taxonomic history of C. balteata) Sowerby apparently replaced one of Adams’ names to avoid homonymy in the genus Cerithium, but this does not apply to Cerithium moerchii. The text does not disclose why this name was chosen, honouring Mörch. The two syntypes are from the Cuming Collection (NHMUK) and Cuming and Mörch are known to have exchanged specimens from the Philippines (Dance 1986: 158), which may provide an explanation. Authorship of this species is here attributed to ‘Adams in Sowerby’ (as also by Petit 2009). The original description gave no locality, but simply noted that it was “a northern species” (Sowerby 1855: 888), yet in a subsequent monograph the locality of the same sample was given as Mindanao, Philippines (Sowerby 1866). No original label survives with the type material and the species is not known to occur in the Philippines. Shells exactly similar to the distinctive syntypes have been seen only from Ishigaki and Iriomote Islands in the Yaeyama group, so the type locality is here corrected accordingly. The change from mörchii to moerchii is a mandatory correction of an incorrect original spelling (ICZN 1999: Art. 32.5.2.1).
Diagnosis. Shell: periphery rounded, spire whorls well rounded; spire profile straight; aperture slightly thickened and flared, sinuous apertural margin; 14–34 rounded axial ribs on penultimate whorl, ribs usually weak or absent after ventrolateral varix; ventrolateral varix a wide rib at 170–230(150–330)°; 0–6 varices on spire; 5–10 spiral cords above periphery, often producing cancellate effect; banded or lined pattern. Southern Japan, South Korea, China, Vietnam. COI GenBank HE680239 – HE680293, AM932773 – AM932775.
Material examined. 68 lots.
Shell (Fig. 15 J–AA): H = 16.1–46.6 mm. Shape elongated conical (H/B = 2.08–2.94; SH = 3.0–4.04); decollate, 5–8(13) whorls remaining; spire whorls moderately to well rounded, suture distinct; spire profile straight; 0–6 thick pale varices on spire; periphery rounded; moderate thickness. Adult lip slightly thickened and flared; apertural margin sinuous in side view; weak anterior projection adjacent to canal. Sculpture on spire of straight to slightly opisthocline axial ribs, becoming slightly curved (opisthocyrt) on last whorl, ribs rounded, interspaces1–1.5 times width of ribs, 14–23(34) ribs on penultimate whorl; axial ribs usually weak or absent after ventrolateral varix, but rarely up to 8 are present; spiral sculpture of 5 primary cords on spire whorls, of which anterior cords usually divide on later whorls to give 6–9 cords on penultimate whorl and up to 10 above periphery on final whorl, posterior cord adjacent to suture strongest and bearing small nodules (corresponding with, or up to twice as numerous, as axial ribs); intersection of axial ribs and spiral cords often giving cancellate effect; base with 8–10 ridges, merging with cords above rounded periphery. Ventrolateral varix a wide rib at 170–230(150–330)°; 0– 6 wide varices on spire. Surface with fine spiral microstriae on periostracum; surface dull when worn. Colour: white, fawn or pale brown, usually with dark brown spiral lines and bands; often a dark band at shoulder and on base, or single broad band from shoulder to periphery, or only spiral grooves dark brown, varices white; bands show through in aperture.
Animal (Fig. 2 E): Head pale brown with cream spots; snout brown to black with cream spots, darker towards tip; tentacles fawn with dark rings, black at base, pinkish around eye; sides of foot grey to blackish brown with cream spots; sole of foot grey; mantle cream (ethanol-preserved specimens similar).
Range (Fig. 14 B): S Japan to Vietnam. Records: Japan: Matsushima Bay, Miyagi Pref. (ANSP 241064); Yokohama (ANSP 49910); Yoshida R., Oiehama, Kasaoka city, Hiroshima Pref. (NHMUK 20130265); Imaizumi, Kagoshima Pref. (USNM 363689); Jigyo, Chuo-ku, Fukuoka Pref. (ANSP 418823); Ura, Tatsugou-cho, Amami city, Kagoshima Pref. (NHMUK 20130271); Waku-gawa, Gabui, Nakijin-son, Okinawa (NHMUK); Funaura Bay, Iriomote I. (NHMUK 20130270). S Korea: Suncheon Bay (Hong, Choi & Tsutsumi 2010); Jeju I. (Noseworthy et al. 2007). China: “throughout Chinese coasts” (Ma 2004: 37); Tolo Harbour, Hong Kong (NHMUK 20130263); Hainan (ZMSP). Taiwan: Tamshui R., Bali (NHMUK 20070387); Kenting National Park (Lee & Chao 2004). Vietnam: Tuan Chau I., Ha Long Bay (NHMUK); Lo R., Nha Trang (NHMUK); Long Hai (Thach 2005).
An old record from Hakodate, in the south of Hokkaido (USNM unregistered) is unconfirmed. The localities Borneo and Labuan [Sabah] on specimens in NHMUK are considered to be incorrect.
Habitat and ecology. On firm or sandy mud and stones of tidal flats, in the open or under mangroves; often at river mouths and in tidal creeks; among salt-tolerant grasses and Phragmites reeds behind mud flats; sometimes on trunks of mangroves including Kandelia and Rhizophora.
A number of authors have described the habitat and habits of this species. In Hong Kong it has been reported as common throughout mangrove stands from seaward to landward, both on the substrate and up to 1.0 m on trunks, where it attaches by mucus when dry (McMahon 1985); at upper tidal levels it also occurs on grasses, sand and rocks in the absence of mangroves (Wells 1985). In Korea, Hong et al. (2010) found it on mud flats among Suaeda bushes. Most observations have been made in southern Japan. The northernmost mangrove forest in the western Pacific is situated at Atago River in southern Kyushu, where the snails are distributed both on trunks of Kandelia and on the tidal flats of sandy mud. The animals feed on the substrate during low tide (Maki, Ohtaki & Tomiyama 2002), but climb trees to avoid submersion at high tide, especially from August to January or in the winter (Ohtaki et al. 2002; Takeuchi, Ohtaki & Tomiyama 2007). The snails not only climb mangroves trees, but also on reeds and rocks (Matsumura 2009). The smallest snails occur only on unvegetated mud flats seaward of salt marsh and mangroves, while adults are more widely distributed (Ohtaki, Maki & Tomiyama 2001; Wada & Nishikawa 2005; Takeuchi et al. 2007). In a population at Matsushima Bay, beyond the northern limit of mangroves, isotopic analyses showed that the major food source was detritus from macroalgae and seagrass, not benthic microalgae (Doi et al. 2009).
In Japan, pseudocopulation takes place from June to August during daytime and nighttime low tides and occurs by males mounting the shells of females (Ohtaki et al. 2001; Takeuchi et al. 2007; Ota, Kawai & Hashimoto 2013). During the process a 3-mm long, spindle-shaped spermatophore is transferred (Onoda et al. 2010). Spawning has been observed from June to August (Wada & Nishikawa 2005; Ota et al. 2013) and was described in detail by Habe (1955). A mass of gelatinous egg strings, about 20 mm wide and 15 mm deep, is deposited in an excavation in the mud. Individual eggs are 0.35 mm in diameter. Houbrick (1984: 12) interpreted this relatively large egg size as “suggesting direct development”, but Kimura et al. (2002) mentioned the existence of planktonic larvae. Kojima et al. (2006) claimed a ‘planktotrophic stage’ of 12–20 days (quoting Kimura et al. 2002 and unpublished work). Ota et al. (2013) also observed that swimming larvae hatched from the eggs. (In a more detailed account of the western Atlantic potamidid Cerithideopsis pliculosa, Miura, Frankel & Torchin 2011 described a shell diameter of 0.3 mm at hatching and observed swimming-crawling, planktotrophic larvae that metamorphosed after 6–13 days, lending indirect support to this claim.)
Ota et al. (2013) described the population dynamics of C. moerchii on a bare tidal flat in E Shikoku, where density varied from 14–79 /m2 over 3 years. Recruitment occurred in late summer and early autumn, and thickened apertural lips (implying reproductive maturity) developed after the third year. Older cohorts occupied lower positions (around mean tide level) in summer; recruitment occurred at these lower levels and was followed by a gradual upward shift.
Remarks. This species has a wide distribution from the temperate zones of central Japan, Korea and northern China to the tropical areas of Vietnam (Fig. 14 B). Correspondingly, it has a wide range of size and shell morphology. Several distinctive regional forms can be recognized, but there are intergradations between them:
(1) Southern China, Vietnam (Fig. 15 J–N): less rounded whorls; numerous narrow axial ribs (usually 19–27); white varices often present on spire.
(2) Mainland Japan (Fig. 15 O–T): large shell; rounded whorls; strong relatively broad axial ribs (usually 19–23); spire varices usually absent; dark or banded pattern.
(3) Amami Islands, Okinawa, Yaeyama Islands, Taiwan (Fig. 15 U–AA): small shell; rounded whorls; strong relatively broad axial ribs (14–18); spire varices usually absent; most primary cords become divided, giving 7– 10 fine spiral ridges on last whorl; axial ribs continue after ventrolateral varix; unbanded but often with dark spiral grooves.
In twentieth century literature, forms (2) and (3) have usually been distinguished as separate species (or subspecies), respectively C. ‘rhizophorarum’ and C. moerchii (see Taxonomic history, above). Despite the distinctive appearance of shells from the southern islands, molecular investigation has failed to find any significant differentiation in COI sequences between these and samples from mainland Japan (Kojima et al. 2006, Reid et al. 2008, 2013). Likewise, Kamimura et al. (2010) found no significant differentiation of this gene among four populations from mainland Japan and Korea. Examination of large series of shells from throughout the range also shows that there is intergradation among the forms (Fig. 15 J–AA).
The larger forms of C. moerchii from China, Korea and Japan are very similar in appearance to C. rhizophorarum, which is restricted to the Philippines, explaining the longstanding confusion of these taxa. Cerithidea moerchii has more rounded whorls, a straight spire profile and shows a wider range of shell patterns, including forms with narrow spiral bands. Forms from China and mainland Japan are more distinctly cancellate than C. rhizophorarum, especially when axial ribs are narrow, and the broad axial ribs of shells from the Ryukyus give a rugose appearance unlike any specimens of C. rhizophorarum. The latter species has flattened whorls, a pupoidal outline, the axial ribs are always narrow, and narrowly banded colour forms have not been seen (Fig. 15A–I). It is predicted that these two will prove to be sister species when their status is tested with molecular data from C. rhizophorarum. In the COI phylogenetic tree (Reid et al. 2013; Fig. 1) C. rhizophorarum was not represented, so C. moerchii appears as sister to C. tonkiniana.
Occasional specimens show an unusually elongate shell with slightly irregular whorls (Fig. 15 S); such shells appear to be the result of abnormal growth, possibly associated with parasitism by trematodes or other environmental influence. Similar malformations have been seen in Cerithideopsilla species from the northwestern Pacific region.
Owing to habitat loss, this species is listed as ‘vulnerable’ in Japan by Fukuda (1996) and as ‘near threatened’ by Kimura & Fukuda (2012).
description: Published as part of Reid, David G., 2014, The genus Cerithidea Swainson, 1840 (Gastropoda: Potamididae) in the Indo-West Pacific region, pp. 1-65 in Zootaxa 3775 (1) on pages 52-55, DOI: 10.11646/zootaxa.3775.1.1, http://zenodo.org/record/285731