Cosmotriphora melanura (C.B. Adams, 1850)

Fernandes, Maurício Romulo & Pimenta, Alexandre Dias, 2019, Basic anatomy of species of Triphoridae (Gastropoda, Triphoroidea) from Brazil, European Journal of Taxonomy 517, pp. 1-60 : 15-18

Cosmotriphora melanura (C.B. Adams, 1850)

Figs 2C , 7–8

Material examined

BRAZIL – Espírito Santo State • [1, d] spec.; Ilha Escalvada, Guarapari ; 20°42´00″ S, 40°24´28″ W; 10–15 m depth; 12 Dec. 2014; M. R. Fernandes and L. S. Souza leg.; MNRJ 33980 . – Rio de Janeiro State • [3, 2 d] specs; Campos Basin ; 22°42´ S, 40°40´ W; 2006; MNRJ 18750 • [3, 2 d] specs; same data as for preceding; MNRJ 33138 .

Description of basic anatomy

EXTERNAL MORPHOLOGY. Body mainly white, but a distinct, sinuous, black stripe occupies the upper-mid portion of the whorl during a little less than half whorl of length, one to two whorls posteriorly to the operculum; roof of mantle cavity can be yellowish in fresh specimens.

OPERCULUM. Yellowish, ovate-elliptical, thin, semi-transparent, membranous, poorly distinct whorls, nucleus subcentral, dislocated 14% to 23% from center toward margin; denticles in the inner border of operculum; diameter of operculum exceeds diameter of opercular pouch in 22% to 30%.

JAW. Wing-shaped; outer side with scales rectangular, rectangular-bilobed or acute-lanceolate; scales with micro-pores up to 260 nm in diameter; inner side with hexagonal scales, surface smooth; outer side with rectangular scales 12.1–12.3 µm long, 2.7–2.9 µm wide, ratio length/width 4.2–4.4, acutelanceolate scales 21.0– 26.7 µm long, 6.9–7.9 µm wide, ratio length/width 3.0–3.7; scales of inner side 13.7–17.3 µm long, 3.9–5.0 µm wide, ratio length/width 2.9–3.8.

RADULA. Formula not discernible because of overcrowded outer marginal teeth; central and lateral teeth head-fork shaped with four triangular cusps, inner ones 1.3–1.6× more elongated than outer ones; inner marginal teeth (i.e., M1 to M5) with three cusps, width of teeth gradually decreasing towards outer marginal teeth, median cusp more prominent and elongated, 1.2–2.1× longer than outer cusps, becoming increasingly elongated towards outer marginal teeth; outer marginal teeth (i.e., after M6) with two elongated and filiform cusps, somewhat hook-shaped, inner cusp much shorter (usually 2.2–2.9× shorter than outer cusp, but even 4.5–5.0× shorter in teeth under development); central tooth 2.9–3.5 µm wide, lateral teeth 2.9–3.6 µm wide, inner marginal teeth 1.7–2.7 µm wide, outer marginal teeth 6.0– 10.6 µm long.

Remarks

Rolán & Fernández-Garcés (1994) described the external morphology of C. melanura as having numerous white/yellowish spots in the anterior portion of the body, which was not observed in the present study probably due to a faint coloration after a long storage in ethanol. However, all specimens had a distinct and previously unnoticed black stripe situated at one to two whorls posteriorly to the operculum ( Fig. 7 A–B), not present in any other triphorid studied so far; this stripe is continuous and does not seem to be related to fecal pellets. Opercula of specimens from Brazil ( Fig. 7 C–D) are identical to those of Caribbean specimens ( Bouchet 1985: fig. 2).

The radula of specimens from Brazil ( Fig. 8 ) is almost identical to that of Caribbean specimens ( Bouchet 1985; Rolán & Fernández-Garcés 1994), with the exception that the central tooth of Brazilian specimens is more similar to the lateral teeth of Caribbean ones (outer cusps considerably shorter than inner ones), but lateral teeth of Brazilian specimens are more similar to the central tooth of Caribbean ones (outer cusps not so shorter than inner ones). Although not illustrated, Bouchet (1985) noted differences in the marginal teeth of a juvenile from the eastern Atlantic when compared to the pattern seen in adults from the western Atlantic, warning for the necessity of fine radular comparisons from adult specimens from both sides of the Atlantic. After examining several specimens from Cuba (Caribbean) and Ghana (eastern Atlantic), Rolán & Fernández-Garcés (1994) concluded that there were no significant differences in their radulae, despite not having illustrated those from the eastern Atlantic.

Figures

Fig. 2. Specimens studied. A. Metaxia excelsa Faber & Moolenbeek, 1991 (MZSP 122353). B. Metaxia rugulosa (C.B. Adams, 1850) (BMSM 56034). C. Cosmotriphora melanura (C.B. Adams, 1850) (MNRJ 33980). D. Iniforis pseudothomae Rolán & Fernández-Garcés, 1993 (MZSP 100957). E. Latitriphora albida (A. Adams, 1854) (BMSM 55442). F. Monophorus olivaceus (Dall, 1889) (MNRJ 34615). G. Nanaphora verbernei (Moolenbeek & Faber, 1989) (MZSP 85022). H. Nototriphora decorata (C.B. Adams, 1850) (MNRJ 28941). I. Sagenotriphora osclausum (Rolán & Fernández-Garcés, 1995) (MNRJ 35061). J. Similiphora intermedia (C.B. Adams, 1850) (MNRJ 29763). K. Strobiligera gaesona (Dall, 1927) (MZSP 53685). L. “Inella” harryleei Rolán & Fernández-Garcés, 2008 (FLMNH 450495). Scale bars: 1 mm.

Fig. 7. Cosmotriphora melanura (C.B. Adams, 1850). A, E, G. MNRJ 33138. B–D, F. MNRJ 18750. A–B. External morphology, different specimens. C–D. Operculum. E–G. Jaw, outer (E–F) and inner (G) sides. Scale bars: A–B = 1 mm; C–D = 100 µm; E, G = 5 µm; F = 2 µm.

Fig. 8. Cosmotriphora melanura (C.B. Adams, 1850). A–G. Radula (MNRJ 18750). Scale bars: A = 10 µm; B–G = 5 µm.