INTRODUCTION
The superfamily Conoidea (=Toxoglossa) is one of the most speciose groups of marine molluscs (Bouchet, Reference Bouchet1990; Tucker, Reference Tucker2004; Puillandre et al., Reference Puillandre, Samadi, Boisselier, Sysoev, Kantor, Cruaud, Couloux and Bouchet2008). These include small to medium (3–50 mm on average) sized species of marine snails that are specialist predators on annelids, other molluscs, and even fish, and occupy all marine habitats from the tropics to the poles, from shallow to deep water, and from hard to soft substrates (Puillandre et al., Reference Puillandre, Samadi, Boisselier, Sysoev, Kantor, Cruaud, Couloux and Bouchet2008). The members of the family Conidae are carnivorous marine gastropods typically found in warm and tropical seas worldwide inhabiting a wide array of benthic environments from lower intertidal to subtidal zones (Abbott, Reference Abbott1974; Rios, Reference Rios1994). The genus Mitromorpha Carpenter, 1865 (=Mitrolumna Bucquoy, Dautzenberg & Dollfus, 1882) was originally described off the west coast of North America and currently about seven species are known from the western Atlantic Ocean (Tucker, Reference Tucker2004; Rosenberg, Reference Rosenberg2005). It is a characteristic genus of the continental shelf and insular environments (Smith, Reference Smith1890; Abbott, Reference Abbott1974; Leal, Reference Leal1991; Mifsud, Reference Mifsud2001; Faber, Reference Faber2006). In the south-eastern Atlantic, Mitromorpha biplicata (Dall, Reference Dall1889) is the only species recorded from Brazil (Leal, Reference Leal1991; Mello & Barros, Reference Mello and Barros1994; Rios, Reference Rios1994).
During the REVIZEE Program (Live Resources of the Exclusive Economic Zone), Absalão et al. (Reference Absalão, Pimenta and Caetano2005) identified seven Mitromorphinae, five of which were Mitromorpha spp. (including the species illustrated by Leal (Reference Leal1991: plate 23, figure c)) from Vitoria Seamount and Abrolhos Reef Complex), showing our poor understanding of the real diversity of this group.
This is the second record of the genus Mitromorpha for the South Atlantic based on the description of a new species for the continental slope of Brazil.
MATERIALS AND METHODS
During exploratory work on the continental slope of Rio Grande do Norte State (04°50′60″–04°51′40″S 35°06′01″–35°06′46″W) carried out by the research ship ‘Natureza’ from the Research and Management Center of Fishing Resources of the Northeastern Coast (CEPENE/IBAMA) in 2001, a large amount of micro-molluscs were dredged up and picked out using a stereomicroscope. Photographs were made with a Nikon COOLPIX885 (8–24 mm) digital camera. Scanning electron micrographs (SEM) were made using a Jeol JSM 6360 scanning electron microscope at the Electron Microscope Laboratory of the Instituto Tecnológico de Pernambuco (ITEP).
Abbreviations: Academy of Natural Sciences of Philadelphia (ANSP), Philadelphia, USA; Laboratório de Malacologia, Universidade Federal Rural de Pernambuco (LMUFRPE), Recife, Brasil; Museu Nacional, Universidade Federal do Rio de Janeiro (MNRJ), Rio de Janeiro, Brasil; Museu Oceanográfico Prof. Eliezér de Carvalho Rios (MORG), Rio Grande, Rio Grande do Sul, Brasil; Museu de Zoologia, Universidade de São Paulo (MZSP), São Paulo, Brazil.
TYPE SPECIES
Daphnella filosa Carpenter, 1864 by original designation (monotypy). Recent, Santa Barbara, California.
REMARKS
Usually the genus Mitrolumna has been classified in the family Turridae (Abbott, Reference Abbott1974; Bouchet & Warén, Reference Bouchet and Warén1980; Rios, Reference Rios1994; Rolán & Boyer, Reference Rolán and Boyer2001; Faber, Reference Faber2006). Taylor et al. (Reference Taylor, Kantor and Sysoev1993), based partly on a cladistic analysis, considered Mitrolumna a synonym of Mitromorpha Carpenter, 1865 and transferred it to Conidae Rafinesque, 1815, producing a radical shift from the traditional suprageneric systematics of Turridae. According to Taylor et al. (Reference Taylor, Kantor and Sysoev1993), Turridae would be both diphyletic and paraphyletic, with genus and species-level classifications also remaining problematic. Rosenberg (Reference Rosenberg1998) reinterpreted these data and found flaws and alternative interpretations, stressing that it would be premature to make any radical changes to systematics of Turridae. Mifsud (Reference Mifsud2001) discussed the turrid genus Mitromorpha and several genus level taxa that might be synonymous, including Mitrolumna. Recently, Faber (Reference Faber2006) assigned the genus Mitrolumna to Turridae (sensu lato) showing the uncertainty of the correct systematic arrangement, and it remains debatable whether the genera Mitromorpha and Mitrolumna are synonymous. Puillandre et al. (Reference Puillandre, Samadi, Boisselier, Sysoev, Kantor, Cruaud, Couloux and Bouchet2008) confirmed with the molecular data that the older interpretation of the family Turridae is erroneous and the so-called ‘higher’ turrids belong to the family Conidae, as was suggested by Taylor et al. (Reference Taylor, Kantor and Sysoev1993).
Consequently, we decided to follow suprageneric systematics based on Taylor et al. (Reference Taylor, Kantor and Sysoev1993) and Puillandre et al. (Reference Puillandre, Samadi, Boisselier, Sysoev, Kantor, Cruaud, Couloux and Bouchet2008), additional to considering Mitromorpha a valid genus (Taylor et al., Reference Taylor, Kantor and Sysoev1993; Mifsud, Reference Mifsud2001).
Photographs and scanning electron micrograph (SEM) of Mitromorpha santosi sp. nov. and congeners occurring along the Brazilian coast. Mitromorpha santosi sp. nov: (A) Ventral view, holotype (length: 5.4 mm); (B) dorsal view, holotype; (C) lateral view, paratype—ANSP (length: 5.2 mm); (D) ventral view, paratype—MZSP (length: 4.8 mm); (E) view of aperture (Figure 1D); (F–G) protoconch, paratype—LMUFRPE; (H) enlarged view from paratype protoconch; (I) Mitromorpha biplicata (Dall, Reference Dall1889) (of Leal (Reference Leal1991: pl. 23, figure A)): ventral view; (J) Mitromorpha sp. 1 (of Leal (Reference Leal1991: pl. 23, figure C)): ventral view; (K) Mitromorpha sp. 3 (of Absalão et al., Reference Absalão, Pimenta and Caetano2005: figure 59 (IBUFRJ 11876: 4.2 mm)). Scale bars: E, I–J, 500µm; F–G, 100µm; H, 50µm.
TYPE MATERIAL
Holotype (MZSP 78935—length 5.4 mm, width 2.9 mm), off Rio Grande do Norte, Brazil, ‘Natureza’ (Station 23, 04°51′40″S 35°06′01″W, 384 m, 24.XI.2001).
1 paratype (ANSP 413551), off Rio Grande do Norte, Brazil, ‘Natureza’ (Station 22, 04°50′60″S 35°06′46″W, 375 m, 24.XI.2001); 1 paratype (MZSP 78936), off Rio Grande do Norte, Brazil, ‘Natureza’ (Station 22, 04°50′60″S 35°06′46″W, 375 m, 24.XI.2001); 2 paratypes (MORG 50687), off Rio Grande do Norte, Brazil, ‘Natureza’ (Station 23, 04°514′0″S 35°06′01″W, 384 m, 24.XI.2001); 2 paratypes (LMUFRPE 049), off Rio Grande do Norte, Brazil, ‘Natureza’ (Station 23, 04°51′40″S 35°06′01″W, 384 m, 24.XI.2001); 2 paratypes (MNRJ 10717), off Rio Grande do Norte, Brazil, ‘Natureza’ (Station 22, 04°50′60″S 35°06′46″W, 375 m, 24.XI.2001).
DIAGNOSIS
Shell white with yellowish-brown spiral bands. Penultimate whorl with 3–4 spiral cords. Body whorl with 5 spiral cords, the second of which is a bit more pronounced. Body whorl with 10–11 strong axial ribs and large interspaces between them. Inner side of outer lip with 5–7 lirae.
DESCRIPTION
Shell small, biconical and white. Size ranging from 4.69–5.42 mm (Figure 1A–D; Table 1). Protoconch with 1(3/4) whorls, globular, granulated (Figure 1H) and nucleus depressed (Figure 1F–G). Transition proto-teleoconch marked by strong opistocline axial ribs (Figure 1G). Suture well marked. Apex angle 53°–55°. Teleoconch with 4 whorls. Whorls slightly convex, with yellowish-brown spiral bands on fresh specimens. First one ornamented by strong axial ribs and obscure spiral cords. Subsequent whorls with spiral ornamentation increasing progressively. Penultimate whorl with 3–4 spiral cords. Body whorl large, about 2/3 of total length with 4–5 spiral cords, forming strong beads where they cross the axial ribs. Usually the second spiral cord is a bit more projected. Axial sculpture with raised ribs invading the base and vanishing toward aperture. Interspaces with about 2× the width rib and equally spaced. Second whorl with 14 axial ribs. Penultimate whorl with 12 ribs. Body whorl with 10–11 ribs. There is a strong suprasutural yellowish-brown spiral band, plus an additional 1 or 2 very weak yellowish-brown spiral bands over the whorl. Base conical, slightly convex with 3–4 strong yellowish-brown spiral bands. Fasciole with 4–5 spiral cords. Aperture elongated, narrower abapically. Parietal wall thin. Columella with two median folds, the uppermost of which is slightly larger. Outer lip thin, with 5–7 lirations inside. Siphonal canal short (Figure 1E).
Linear measurements of Mitromorpha santos i sp. nov. specimens.
N, number; M, mean; R, range; SD, standard deviation.
ETYMOLOGY
Named after our friend, the malacologist Franklin Noel dos Santos who first sorted specimens of the new species for study.
TYPE LOCALITY
Continental slope off the State of Rio Grande do Norte (04°51′40″S 35°06′01″W), 384 m.
DISTRIBUTION
Restricted to continental slope off Rio Grande do Norte State, Brazil.
DISCUSSION
Mitromorpha santosi sp. nov. differs from all western Atlantic species of Mitromorpha by the presence of strong axial ornamentation, yellowish-brown spiral bands and a granulated protoconch surface. Also, it is one of the few Mitromorpha collected in the deep sea in the Atlantic Ocean, which suggests a bathymetric isolation from the remaining unnamed species from south-eastern Brazil (Absalão et al., Reference Absalão, Pimenta and Caetano2005). Off the Brazilian coast there are sporadic records of M. biplicata on the continental slope (Dall, Reference Dall1889; Abbott, Reference Abbott1974).
Based on the shell morphology, Mitromorpha santosi sp. nov. and M. usta (Smith, Reference Smith1890: plate 23, figure 4) (eastern Atlantic: St Helena) share strong axial cords and weak spiral cords, which is not a common pattern for most species occurring in the Atlantic Ocean. Mitromorpha santosi sp. nov. have larger size (total length: 4.69–5.42 mm) with four whorls on the teleoconch, 1(3/4) whorls on the protoconch, 10–11 ribs on the body whorl, while M. usta presents smaller size (total length: 2.75 mm), five whorls on the teleoconch, 1(1/2) whorls on the protoconch and 12–14 oblique ribs on the body whorl with a more granular appearance and white spots on dark shells.
Mitromorpha santosi sp. nov. resembles M. dalli (Dautzenberg & Fischer, 1896) (north-eastern Atlantic, in Bouchet & Warén (Reference Bouchet and Warén1980: figure 160)) by the presence of strong axial sculpture, columellar folds and aperture shape, being easily distinguished by the presence of lirations on the inner side of the outer lip, no prominent and more spaced spiral sculpture, having three or four spiral cords on the penultimate whorl.
In the southern Atlantic the only named Mitromorpha is M. biplicata (Dall, Reference Dall1889) (Leal, Reference Leal1991: 182, 340, plate 23, figures A–B, Figure 1I (here); Rios, Reference Rios1994: 170, figure 779; Absalão et al., Reference Absalão, Pimenta and Caetano2005: 29, 42, figure 56). Mitromorpha santosi sp. nov. resemble M. biplicata in presenting an elongated aperture of nearly half of the shell length, two weak columellar folds, the adapical being stronger and lirations on the inner side of the outer lip. Mitromorpha santosi sp. nov. is distinguished from M. biplicata by having four whorls on the teleoconch, non-cancellate ornamentation, colour white with yellowish-brown spiral bands, protoconch with 1(3/4) whorl, 10–11 strongly beaded axial ornaments on the body whorl, subsutural spiral cord weaker and the lower cord stronger with no formation of a groove between them.
Mitromorpha santosi sp. nov. and M. popeae (Faber, Reference Faber2006) (West Indies) share two fairly strong plicae midway the columella and aperture about half the height of the whole shell. But M. santosi sp. nov. differ considerably from M. popeae by having predominately white postnuclear whorls with yellowish-brown spiral bands, 3–4 spiral cords on the last whorl, forming strong beads where they cross the axial ribs, outer lip with internal lirae and not crenulate appearance. Mitromorpha popeae has a predominately brown teleoconch, 19 spiral ribs on the last whorl, the intersections of spiral and axial ribs a bit elevated giving the shell a weakly crenulate appearance. Inside of outer lip weakly crenulate.
Mitromorpha santosi sp. nov. and M. undulata Dall, Reference Dall1927 are similar in presenting a small and white shell, second spiral cord a bit more projected, penultimate whorl with four and body whorl with about six spiral cords, aperture narrowed, elongated with outer lip thin and lirate within. Mitromorpha santosi sp. nov. is distinguished from M. undulata to present a granulated protoconch, suture well marked, body whorl with only the second prominent spiral cord and axial sculpture with raised ribs (12 on the penultimate whorl). Mitromorpha undulata has a smooth nuclear whorl, undulated and appressed suture, first and second thickened spiral cord and a bit more projected, slightly swollen where they cross the ribs and nine axial ribs on the penultimate whorl.
The original description of Mitromorpha undulata Dall (Reference Dall1927:50) provides the measurements of a single specimen, and states that this species is based on one specimen from off Fernandina (USNM 107995). An examination of this lot revealed three specimens to be present, all under the same catalogue number and from the same locality. The catalogue ledger confirmed that three specimens were present in this lot when the USNM catalogue number was assigned. Whether the error in the published number of specimens is due to a lapsus calumni on the part of Dall, or to a typographical error, it is clear that the type series of Mitromorpha undulata Dall consists of three syntypes (Article 72.4.1.1, International Commission on Zoological Nomenclature, 1999). The specimen that conforms to Dall's published measurements (Figure 2B) is here designated as the lectotype of Mitromorpha undulata in order to provide an objective standard that is consistent with Dall's original concept of this taxon.
Scanning electron micrograph (SEM) of Mitromorpha undulata (USNM 107995): (A) Ventral view, paralectotype; (B) ventral view, lectotype; (C) dorsal view, paralectotype. Scale bar: A–C, 1 mm.
Besides that, Mitromorpha santosi sp. nov. were compared with two unnamed Brazilian congeners (M. sp. 1 of Leal (Reference Leal1991) and M. sp. 3 of Absalão et al. (Reference Absalão, Pimenta and Caetano2005)) as the single taxa reported for the region is M. biplicata. Strong similarity of some characters, in contrast to the singular shell morphology of these taxa, is not seen in other Atlantic Mitromorpha, which soon will be described, increasing significantly the richness of Brazilian species.
Mitromorpha santosi sp. nov. and M. sp. 1 (Leal, Reference Leal1991: 183; 340, plate 23, figure C, Figure 1J (here)) have similar denticles on the inner side of the outer lip. Mitromorpha santosi sp. nov. develop spiral cords and axial ribs, while M. sp. 1 has only spiral cords on the teleoconch.
Mitromorpha santosi sp. nov. is strongly correlated to Mitromorpha sp. 3 (Absalão et al., Reference Absalão, Pimenta and Caetano2005: 29; 42, figure 59, Figure 1K (here)) collected in south-eastern Brazil in the biconical contour of the shell with a spire of a relatively constricted appearance, a robust body whorl and whitish coloration. Mitromorpha santosi sp. nov. differs from Mitromorpha sp. 3 which has axial sculpture dominant, the second spiral cord more pronounced on the body whorl, with no depression either below or above it. Mitromorpha sp. 3 is dominated by spiral cords cut by relatively fine axial ribs; the first subsutural cord is more developed, forming a concavity below it.
ACKNOWLEDGEMENTS
We thank Mr Richard E. Petit for correction on the text and generous assistance in obtaining the literature; Mr Marien J. Faber (The Netherlands), Emilio Rolán (Spain) and Dr Alexandre D. Pimenta (Museu Nacional, Universidade Federal do Rio de Janeiro) for his generous assistance in obtaining the literature; Dr José H. Leal (The Bailey-Matthews Shell Museum, Sanibel, Florida) for the critical review of the work and making the SEM of his book available; Dr Ricardo S. Absalão (Instituto de Biologia, Universidade Federal do Rio de Janeiro) for the critical review of the work and improvement of the text; Dr M.G. Harasewych (Curator of Marine Mollusca, Department of Invertebrate Zoology, National Museum of Natural History, Smithsonian Institution) for providing SEM and preparing the text of the designation of Mitromorpha undulata; two anonymous referees for their corrections and suggestions to the paper.
