INTRODUCTION
The genus Opaliopsis Thiele, Reference Thiele1928 comprises a group of deep-water marine microgastropods belonging to the family Nystiellidae Clench & Turner, Reference Clench, Turner and Clench1952. It was originally described as a section of the genus Scala, to include Scala (Opaliopsis) elata Thiele, 1925 and diagnosed as small turriculate shells with a brown, densely ribbed protoconch and with a teleoconch with strong ribs (Thiele, Reference Thiele1929).
The genus is represented in the western Atlantic by five species. All were originally described from northern localities, in the USA: Alabama: Opaliopsis rabalaisi García, 2005; Georgia: Opaliopsis opalina (Dall, Reference Dall1927) and Opaliopsis canium (Dall, Reference Dall1927); Florida: Opaliopsis concava (Dall, Reference Dall1927); and Cuba: Opaliopsis atlantis (Clench & Turner, Reference Clench, Turner and Clench1952). From other regions of the world, Weil et al. (Reference Weil, Brown and Neville1999) listed O. meiringnaudeae Kilburn, Reference Kilburn1985 from South Africa, O. elata from East Africa, and O. hiranoi (Shikama, Reference Shikama1962) from Japan. In addition, Bouchet & Warén (Reference Bouchet and Warén1986) stated that several undescribed species occur in the Indo-Pacific, while Kiel (Reference Kiel2001) and Krüger (Reference Krüger2002) reported fossil taxa from Mexico, Spain and Germany.
Clench & Turner (Reference Clench, Turner and Clench1952), based on the western Atlantic species created the genus Nystiella, diagnosed very similarly to Opaliopsis. In addition, they proposed the subfamily Nystiellinae for the family Epitoniidae, to include Nystiella and Solustiscala, based on the radula and on the presence of strong axial ribs in the protoconch.
Kilburn (Reference Kilburn1985), based on the similarity of general characters between the type species, proposed the synonymy of Nystiella and Opaliopsis. His proposal was followed by Bouchet & Warén (Reference Bouchet and Warén1986), who demonstrated the validity of the subfamily name Nystiellinae, also including Eccliseogyra (=Solustiscala), Narrimania, Iphitus and Papuliscala. Finally, Nützel (Reference Nützel1998) raised the Nystiellinae to family rank, and this proposal was followed by Bouchet & Rocroi (Reference Bouchet and Rocroi2005).
Recently, species of Opaliopsis were recorded from localities in Brazil, which considerably enlarged the known latitudinal range of the genus. However, these records are somewhat imprecise, since they were established in malacological lists or catalogues, without descriptions or illustrations, and based on doubtful determinations. Miyaji (Reference Miyaji, Amaral and Rossi-Wongtschowski2004) recorded Opaliopsis cf atlantis and Opaliopsis sp. from the southern coast of Brazil. Benkendorfer & Soares-Gomes (Reference Benkendorfer and Soares-Gomes2009) listed Opaliopsis aff. nitida (Verrill & Smith, 1885) from eastern Brazil. Rios (Reference Rios2009) recorded Nystiella atlantis from Pernambuco and Campos (state of Rio de Janeiro; [sic]), providing a photocopy of the holotype illustration by Clench & Turner (Reference Clench, Turner and Clench1952).
Therefore, knowledge of this genus in Brazil is still fragmentary. Recent collections in different localities on the Brazilian coast revealed three species of Opaliopsis, which are the subject of this revision.
MATERIALS AND METHODS
This study is based on empty shells collected at different localities on the north-east and south-east coasts of Brazil, in depths of 240–610 m. The identification of the taxa was based on Dall (Reference Dall1927), Clench & Turner (Reference Clench, Turner and Clench1952), Kilburn (Reference Kilburn1985) and Bouchet & Warén (Reference Bouchet and Warén1986). In the material lists, the number inside square brackets indicates the amount of shells in each lot.
Abbreviations used: IBUFRJ: Instituto de Biologia/Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil; MCZ: Museum of Comparative Zoology, Cambridge, USA; MNRJ: Museu Nacional/Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil; MZSP: Museu de Zoologia/Universidade de São Paulo, São Paulo, Brazil; USNM: National Museum of Natural History, Washington, DC, USA.
Opaliopsis Thiele, Reference Thiele1928: 92. Type species by original designation: Scala elata Thiele, 1925.
Nystiella Clench & Turner, Reference Clench, Turner and Clench1952: 337. Type species by original designation: Epitonium opalinum Dall, Reference Dall1927. Synonymized by Kilburn (Reference Kilburn1985).
Figs 1–3. Opaliopsis atlantis. MNRJ 13615. (1) Whole shell (8.15 mm); (2) last whorl; (3) detail of sculpture on last whorl. Scale bars: (2) 500 µm; (3) 100 µm.
Nystiella atlantis Clench & Turner, Reference Clench, Turner and Clench1952: 343, pl. 168; Rios (Reference Rios2009: 186, figure 454, holotype photograph reproduced).
Opaliopsis atlantis: Bouchet & Warén (1986: 489, figures 1133, 1151–1152); Weil et al. (Reference Weil, Brown and Neville1999: 26, figure 67); Ardovini & Cossignani (Reference Ardovini and Cossignani2004: 140); Segers et al. (Reference Segers, Swinnen and Prins2009: 107).
TYPE MATERIAL
Holotype: MCZ 187988, off Bahía de Cochinos, Cuba (22°09′ N 081°10′W), 420–484 m.
Paratypes: T. McGuinty collection (Clench & Turner, Reference Clench, Turner and Clench1952) and USNM 417386 (Weil et al., Reference Weil, Brown and Neville1999).
MATERIAL EXAMINED
Brazil: Ceará State: off Canopus Bank (02°14′25″S 38°22′50″W, 240–260 m), November 2005: MNRJ 13617, [1]; MZSP 67621, [1]. Pernambuco State: MNRJ 15499, [1]. Santa Catarina State: off Itajaí (26°38′44.9″S 46°51′54.2″W, 150 m), February 2004: MNRJ 13615, [2]; MNRJ 13616, [3].
CHARACTERIZATION
Shell turriculate; imperforate; opaque; spire angle about 28°; maximum length/width 8.15 mm/3 mm (8th teleoconch whorl). Protoconch conical; dark brown; partly broken, up to two remaining whorls (400 µm wide); with strong orthocline axial riblets (about 27 on last protoconch whorl), interspaces with about 18 microscopic spiral striae. Teleoconch with up to nine convex whorls; cream-coloured; suture impressed and distinctly sinuous, subsutural spiral band with axial lines only. Sculpture consisting of strong non-lamellar axial ribs, some forming varices, 14–15 ribs per whorl (7th–9th whorls), crossed by 13 strong spiral cords somewhat darker than overall shell colour, forming nodules on intersections; interspaces about same width as ribs; entire teleoconch surface with microscopic axial lines. Periphery of last whorl with spiral basal ridge crossed by the axial ribs. Base pattern same as palatal area, with about five strong spiral cords forming nodules at the intersections with the axial ribs. Aperture subcircular, slightly pointed below, peristome thickened by the last axial rib, columella arcuate.
DISTRIBUTION
Eastern Atlantic Ocean: Azores, Strait of Gibraltar (Bouchet & Warén, Reference Bouchet and Warén1986: 489); Canary Islands, Madeira (Segers et al., Reference Segers, Swinnen and Prins2009: 107); western Atlantic Ocean: USA: Florida; Cuba: Bahía de Conchinos (Clench & Turner, Reference Clench, Turner and Clench1952: 344); Brazil: Rio de Janeiro (Rios, Reference Rios2009); Ceará, Pernambuco and Santa Catarina (this study).
Figs 4–9. Opaliopsis opalina. MNRJ 13964. (4–5) Whole shell (9.4 mm); (6) protoconch; (7) detail of sculpture in last protoconch whorl; (8) last whorl; (9) detail of sculpture on last whorl. Scale bars: (6–7 & 9) 100 µm; (8) 500 µm.
Epitonium opalinum Dall, Reference Dall1927: 61.
Epitonium lavaratum Dall, Reference Dall1927: 62. Synonymized by Clench & Turner (Reference Clench, Turner and Clench1952).
Opalia ? dromio Dall, Reference Dall1927: 63. Synonymized by Clench & Turner (Reference Clench, Turner and Clench1952).
Nystiella opalina: Clench & Turner (Reference Clench, Turner and Clench1952: 337, pls 163–164).
TYPE MATERIAL
Holotype USNM 108368 (Clench & Turner, Reference Clench, Turner and Clench1952), off Georgia, USA, Albatross Station 2415, 804 m.
MATERIAL EXAMINATED
Brazil: Ceará State: off Canopus Bank (02°14′25″S 38°22′50″W, 240–260 m), November 2005: MNRJ 13688, [1]; MZSP 70304, [2]. São Paulo State: off Santos: MNRJ 13694, [3].
CHARACTERIZATION
Shell turriculate; imperforate; translucent; spire angle about 23°; maximum length/width 11.7 mm/3.5 mm (apex broken, with eight remaining teleoconch whorls, estimated 6th–13th by comparison with other specimens). Protoconch conical; dark brown; with 3.5 whorls (650 µm height, 400 µm width), nuclear one smooth, remaining with strong orthocline axial riblets (about 25 on last protoconch whorl); interspaces with about 20 microscopic spiral striae. Teleoconch with up to probably 13 convex whorls (largest specimen with apex broken); cream-coloured, with a narrow subsutural light brown band; suture straight impressed, with a low suprasutural spiral cord more conspicuous from the sixth whorl on and a somewhat irregular subsutural band where growth lines are more contrasting. Sculpture consisting of tiny, low, rounded axial ribs (about 25 on the body whorl), some of them forming discrete varices; interspaces about twice the ribs width, crossed by numerous very tiny spiral striae, irregularly spaced, that surpass the axial ribs; spiral sculpture absent on initial six whorls. Periphery of the last teleoconch whorl with spiral base ridge. Base is somewhat flat and smooth except for growth lines. Aperture subquadrate, inner lip reflected on parietal region, outer lip thin and somewhat rounded, columella arcuate.
DISTRIBUTION
USA: from Georgia to Florida; West Indies: off St Cristopher Island (Clench & Turner, Reference Clench, Turner and Clench1952); Brazil: Ceará and Rio de Janeiro (this study).
Figs 10–16. Opaliopsis new species. (10) Holotype (6.4 mm length); (11–16) paratypes (MNRJ 13347); (11) whole shell (5.7 mm); (12) protoconch; (13) first protoconch whorl; (14) detail of sculpture on last protoconch whorl; (15) last whorl; (16) detail of sculpture on last whorl. Scale bars: (12–14 & 16) 100 µm; (15) 500 µm.
TYPE MATERIAL
Holotype: MNRJ 15500, Canopus Bank, 96 miles off Ceará State, Brazil (02°14′25″S 38°22′50″W, 240–260 m).
Paratypes (all from type locality): MNRJ 13347, [3]; MZSP 70329, [6]; IBUFRJ 18945, [1].
DIAGNOSIS
Shell with numerous regularly spaced spiral sculpture on teleoconch, surpassing the axial ribs, without nodule formation, and distinct axial growth striae covering entire surface of teleoconch whorls.
DESCRIPTION
Shell turriculate, spire angle about 27°, maximum length/width 6.4 mm/2.15 mm; imperforate. Protoconch conical, dark brown, with about five whorls, earliest two globose and smooth, the remainder subpyriform in profile, sculptured with strong orthocline axial riblets; about 22 riblets on last protoconch whorl; interspaces with about 23 microscopic spiral striae, not surpassing the axial riblets. Teleoconch somewhat translucent, colour light cream; with up to eight whorls of strongly convex profile; suture impressed, slightly sinuous, with a very thin spiral cord above. Sculpture consisting of strong non-lamellar axial ribs; holotype with 18, 16, 14, 13, 12, 11, 11 and 13 ribs on whorls 1–8 respectively; two to three varices per whorl, slightly developed and fairly distinct from axial sculpture; interspaces approximately twice the ribs width, crossed by 12–15 spiral cords of regular width and spacing surpassing the axial ribs, not forming nodules; entire teleoconch surface with very thin axial lines. Periphery of last teleoconch whorl with a spiral basal ridge. Base sharply angled, somewhat flattened, sculptured with about 10 undulating spiral cords and microscopic axial lines; teleoconch axial ribs do not continue over the base, except for evanescent varices. Aperture is circular, slightly projected below, columella slightly oblique, outer lip thin.
Dimensions: holotype with eight teleoconch whorls; total length: 6.4 mm; length up to 7th teleoconch whorl, 4.0 mm; length up to 6th teleoconch whorl, 3.2 mm; total width: 1.9 mm; width of 7th teleoconch whorl: 1.3 mm; width of 6th teleoconch whorl: 1.4 mm. Protoconch: 580 µm height, 360 µm width.
ETYMOLOGY
‘Cearense’ is the designation for people who were born in Ceará State.
TYPE LOCALITY
Found in Canopus Bank, 96 miles off Ceará State, Brazil (02°14′25″S 38°22′50″W, 240–260 m).
DISTRIBUTION
This species is known from type locality only (Figure 17).
Fig 17. Map of South America, with detail of Canopus Bank (56 m depth), off Fortaleza City, type locality of Opaliopsis cearense (black arrow indicates site of collecting, in the isobath of ~250 m depth). Approximate sites of occurrence of the other species also shown (see Materials list for details): (1) off Pernambuco State; (2) off Santos, São Paulo State; (3) off Itajaí, Santa Catarina State.
DISCUSSION
Opaliopsis cearense (Figures 10–16) exhibits the distinguishing shell characters of Opaliopsis. The protoconch (Figures 12–14) is typical for the family Nystiellidae, as described by Clench & Turner (Reference Clench, Turner and Clench1952) and Bouchet & Warén (Reference Bouchet and Warén1986). The teleoconch whorls have strong axial ribs (Figures 10–11 & 15), in a similar pattern to O. opalina (Figures 4–5 & 8), O. rabalaisi (Garcia, Reference Garcia2005), and O. cania, this last one the most similar western Atlantic species, as also in the turriculate shell shape. In O. opalina (Figures 4–9) the spiral sculpture is very tiny (Figure 9), whereas in O. cania and to a lesser extent in O. rabalaisi the spirals are much stronger, forming small nodules when crossing the axials. In O. cearense, the spiral riblets cross the axial ribs but do not form nodules (Figure 16). Additionally, the spiral riblets are more numerous (about 16 per whorl) (Figures 15–16) than in O. cania (about six per whorl) and O. rabalaisi (about eight).
There is some variation among species of Opaliopsis regarding the expression of the basal ridge and sculpture. Opaliopsis opalina (Figure 8), O. cania, O. rabalaisi, and O. cearense (Figure 15), as well as the type species O. elata, have a well-marked perypheric spiral ridge. Opaliopsis atlantis (Figure 2) and O. meiringnaudeae, in contrast, lack such a ridge. The type species O. elata has a smooth base (Weil et al., Reference Weil, Brown and Neville1999). In O. opalina, the base is almost smooth (Figure 8); in O. cania, O. rabalaisi and O. cearense (Figure 15) the base has better-defined spiral lines, while in O. atlantis (Figure 2) and O. meiringnaudeae, the base has the same sculpture pattern as the last whorl, with the axial ribs and spiral cords continuing over it as a strong sculpture.
Clench & Turner (Reference Clench, Turner and Clench1952) recognized thread-like axial ridges covering the surface of the shell of O. cania, particularly in the intercostal spaces. The same sculpture is found in O. atlantis (Figure 3) and O. cearense (Figure 16).
Previous records of Opaliopsis from Brazil should be considered dubious. The first record of the genus was reported by Miyaji (Reference Miyaji, Amaral and Rossi-Wongtschowski2004) in a list of molluscs species collected in southern localities off Brazil. The author listed Opaliopsis cf atlantis and Opaliopsis sp. The taxonomic list has no illustration or comment about the specimens that gave rise to the record, and the specimens could not be found in Brazilian collections. Benkendorfer & Soares-Gomes (Reference Benkendorfer and Soares-Gomes2009) listed Opaliopsis aff. nitida (Verrill & Smith, 1885) from south-east Brazil; this taxon is currently allocated to a different genus, Eccliseogyra, according to Bouchet & Warén (Reference Bouchet and Warén1986). Rios (Reference Rios2009) listed Opaliopsis atlantis from Pernambuco and Rio de Janeiro. However, the figure presented was not of a specimen from Brazil, but a reproduction of the photograph in Bouchet & Warén (Reference Bouchet and Warén1986).
The results presented herein confirm the occurrence of Opaliopsis atlantis in Brazil. This is the only amphi-Atlantic species reported for this genus. Amphi-Atlantism seems to be rare in the Nystiellidae, with only an additional known record in Eccliseogyra nitida (Bouchet & Warén, 1985).
The depth-ranges of the three species studied herein, indicate the lowest depth (240 m) record of Opaliopsis, a deep-water taxon, whose bathymetry varies from 460 m (Shikama, Reference Shikama1962) to 804 m (Clench & Turner, Reference Clench, Turner and Clench1952). Bouchet & Warén (Reference Bouchet and Warén1986) stated that although this is a small genus with few species, there are several undescribed species of Opaliopsis from Indo-Pacific deep waters. The records of the three species from the south-western Atlantic presented herein are additional evidence that the richness and range of occurrence of this genus may be greater than presently known, and that additional deep-water surveys may help to better understand its biogeography.
ACKNOWLEDGEMENTS
We are grateful to MSc Silvio Lima, for supplying new information about Opaliopsis taxonomy; Mr Elivaldo de Lima, for scanning electron microscopy operation; Dra Janet Reid, for revising the English text; Mr Antonio Gil Bezerra and Ms Elisa Gradvohl Bezerra, owners of INACE Shipyard (Indústria Naval do Ceará) for the loan of the fishing boat and Mr José Coltro and Mr Marcos Coltro, for help during the field trip to Canopus Bank; the two anonymous referees, for their constructive criticisms and contributions; Conselho de Aperfeiçoamento de Ensino Superior (CAPES), for the fellowship to B. Andrade; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) provided a PROTAX post-doctoral grant to P.M. Costa; and CENPES/PETROBRAS, for the financial support for the development of the Center for Scanning Electron Microscopy of the Museu Nacional/UFRJ.
