Homalocantha Mörch, 1852

Merle, Didier & Garrigues, Bernard, 2011, Description of four new species of Muricidae (Mollusca, Gastropoda) from the Philippines and the Caribbean area, Zoosystema 33 (4), pp. 557-575 : 559

Genus Homalocantha Mörch, 1852

TYPE SPECIES. — Murex scorpio Linnaeus, 1758 by monotypy.

COMMENTS ON THE SUBFAMILIAL ASSIGMENT

The genus Homalocantha should be placed in incertae sedis in the subfamilies Muricopsinae and Muricinae (see Barco et al. 2010). We place here Homalocantha in the Muricopsinae as did Vokes (1994), but this placement is provisional, waiting for new phylogenetic data based on molecular studies.

COMMENTS ON THE SPECIES OF THE GROUP

OF H. SCORPIO (LINNAEUS, 1758)

The two new species described here belong to a group of close species including H. scorpio (Linnaeus, 1758) , H. pisori d’Attilio & Kosuge, 1989 , H. vicdani d’Attilio & Kosuge, 1989 and H. dondani d’Attilio & Kosuge, 1989 . Historically, H. scorpio was defined on the basis of adult specimens, but the three other species were defined only on the basis of juvenile specimens

( d’Attilio & Kosuge 1989). Consequently, juveniles of H. scorpio were not represented or figured by d’Attilio & Kosuge (1989) and adults of the other three species have not been described. Since d’Attilio & Kosuge (1989), no worker was interested to document better the ontogeny of these species. The opportunity to study new material allows relating juveniles to adults and then to understand and define these species better from a growth series. Thus, it is the first time that a growth series is presented for these species ( Figs 1-6 ). Our observations are based on 225 specimens of H. scorpio , 32 specimens of H. pisori , 25 specimens of H. vicdani , 4 specimens of H. dondani , 5 specimens of H. granpoderi n. sp. and 29 specimens of H. ninae n. sp. Considering only adults morphologies, morphological differences could be interpreted as intraspecific variations, but young morphologies appear poorly variable and more differentiated than adults. For example, juveniles of H. scorpio (e.g., Fig. 3A ) display few variations regarding their cords, their shape and their colour and differ clearly from the juveniles of H. granpoderi n. sp. ( Fig. 1 ). So, our experience based on numerous specimens suggests that, for this group of Homalocantha , young morphologies characterize species better than the adult morphologies do. On the evolutionary point of view, ontogenic changes affecting younger morphologies than adult morphologies correspond to a heterochronic process called early innovations ( Dommergues et al. 1986; Videt & Néraudeau 2003). On the other hand, the Philippines hotspot is identified as one of the world’s biologically richest areas and it is not surprising to find several muricid species of the same genus in this area. In comparison to the Philippines archipelago, the São Tomé and Principe Islands (West Africa), a smaller area with a lower species richness, contains no more than six species of Muricopsis ( Rolán & Fernandes 1991; Houart 1996, 2005; Rolán & Gori 2007; Houart & Gori, 2008): M. rutilus mariangelae Rolán & Fernandes, 1991 , M. matildae Rolán & Fernandes, 1991 , M. principensis Rolán & Fernandes, 1991 , M. delemarrei Houart, 2005 , M. hernandezi Rolán & Gori, 2007 and M. (s.s.) testorii Houart & Gori, 2008.

Figures

FIG. 1. — Homalocantha granpoderi n. sp. and H. ninae n. sp., primary cords in dorsal and apical views: A-D, H. granpoderi n. sp.; A, paratype MNHN.IM.24627 (H: 24 mm); B, Coll. GG, Palawan, Philippines (H: 39.9 mm); C, holotype MNHN.IM.24626 (H: 47 mm); D, paratype (apical view); E-H, H. ninae n. sp.; E, syntype 1 MNHN.IM.24628 (H: 25 mm); F, Coll. BG, Balicasag Island, Philippines (H: 26.6 mm); G, syntype 2 (H: 37.8 mm); H, syntype 1 MNHN.IM.24629 (apical view). Scale bars: 10 mm.

FIG. 2. — Homalocantha granpoderi n. sp. and H. ninae n. sp., primary cords in ventral view: A, B, H. granpoderi n. sp.; A, paratype MNHN.IM.24627 (H: 24 mm); B, holotype MNHN.IM.24626 (H: 39.9 mm); C, D, H. ninae n. sp.; C, syntype no. 1 MNHN.IM.24628 (H: 25 mm); D, syntype no. 2 MNHN.IM.24629 (H: 37.8 mm). Scale bars: 10 mm.

FIG. 3. — Homalocantha scorpio (Linnaeus, 1758) and H. pisori d’Attilio & Kosuge, 1989, primary cords in dorsal and apical views: A-D, H. scorpio; A, Coll. BG, 10 m, Bantayan Island, Cebu, Philippines (H: 24.7 mm); B, Coll. BG, 10 m, Calituban, Bohol, Philippines (H: 36.8 mm); C, Coll. BG, Calituban, Philippines (H: 51.6 mm); D, Coll. BG, Balut Island, Mindanao, Philippines (H: 28 mm) (apical view);E-H, H. pisori; E, Coll. BG,Philippines (H: 14 mm);F, H (apical view), Coll.BG, Davao at 80-120 m deep, Philippines (H: 29 mm); G, Coll. BG, Bohol at 20 m deep, Philippines (H: 40 mm). Scale bars: 10 mm.

FIG. 4. — Homalocantha scorpio (Linnaeus,1758) and H.pisori d’Attilio & Kosuge,1989, primary cords in ventral view:A, B, H.scorpio; A, Coll. BG, Balut Island, Mindanao, Philippines (H: 29 mm); B, Coll. BG, Calituban, Philippines (H: 51.6 mm); C, D, H. pisori; C, Coll. BG, Bantayan Island, Cebu, Philippines (H: 24.7 mm); D, Coll. BG, Mactan Island, Philippines (H: 44.2 mm). Scale bars: 10 mm.

FIG. 5. — Homalocantha vicdani d’Attilio & Kosuge, 1989 and H. dondani d’Attilio & Kosuge, 1989, primary cords in dorsal and apical views: A-D, H. vicdani; A, Coll. BG, Camiguin, at 30 m deep, Mindanao, Philippines (H: 20 mm); B, D (apical view), Coll. BG, Mactan Island at 12 m deep, Philippines (H: 23 mm); C, Coll. BG, Calituban Island, Philippines (H: 36.2 mm); E-H, H. dondani; E, Coll. BG, Philippines (H: 19.3 mm); F, H, apical view, Coll. BG, Philippines (H: 31.7 mm); G, Coll. BG, Calituban Island at 20 m deep, Bohol (H: 30 mm). Scale bars: 10 mm.

FIG. 6. — Homalocantha vicdani d’Attilio & Kosuge, 1989 and H. dondani d’Attilio & Kosuge, 1989, primary cords in ventral view: A, B, H. vicdani; A, Coll. BG, 120 m, Mactan Island, Philippines (H: 22.6 mm); B, Coll. BG, Palawan Island, Philippines (H: 36.5 mm); C, D, H. dondani; C, Coll. BG, Philippines (H: 19.3 mm); D, Coll. BG, Calituban Island at 20 m deep, Bohol (H: 30 mm). Scale bars: 10 mm.