Nanaphora verbernei (Moolenbeek & Faber, 1989)

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 : 30-33

Nanaphora verbernei (Moolenbeek & Faber, 1989)

Figs 2G , 19–20

Material examined

BRAZIL – Rio de Janeiro State • [4, 1 d] specs; Campos Basin , 22°42´S, 40°40´W; 2006; MNRJ 18756 • [1, d] spec.; same data as for preceding; MNRJ 33139 . – São Paulo State • [2, 1 d] specs; Ilha da Queimada Pequena , Itanhaém; 0–12 m depth; MZSP 85022 . – Santa Catarina State • [1] spec.; Praia da Sepultura, Bombinhas ; 27°08´26″ S, 48°28´43″ W; 17 Dec. 2016; M.R. Fernandes leg.; MNRJ 28936 • [2] specs; Praia da Tainha, Bombinhas ; 27°12´59″ S, 48°30´40″ W; 21 Dec. 2016; M.R. Fernandes leg.; MNRJ 28951 • [5, 2 d] specs; same data as for preceding; MNRJ 28956 .

Description of basic anatomy

EXTERNAL MORPHOLOGY. Body cream-yellowish, head-foot reddish, but the vivid pigmentation on headfoot vanishes after fixation; pedal slit covering about 68% of foot length; some black encapsulated fecal pellets present along intestine, with a vesicular shape and 82–100 µm long.

OPERCULUM. Rounded, flat, moderately thin, semi-transparent, multispiral, 4.75 whorls, nucleus subcentral, dislocated 15% from center toward margin; diameter of operculum exceeds diameter of opercular pouch in 13–23%.

RADULA. Formula 8-1-1-1-8; teeth row arranged in a ‘V-shape, with adjacent teeth aligned in a somewhat diagonal position to each other; central tooth with three main broad and triangular cusps, outer cusps 1.1–1.3× more elongated than median one, in addition to two marginal cusps very reduced in size; in one radula ( Fig. 20 A–D), lateral teeth with three (left of central tooth) or four (right of central tooth) main broad and triangular cusps, in addition to two marginal cusps reduced in size, resulting in lateral teeth with five (left) or six (right) cusps; left lateral teeth with cusps 1 and 5 with length 39–63% of cusps 2 and 4, cusp 3 with length 70–88% of cusps 2 and 4; right lateral teeth with cusps 1 and 6 with length 29–47% of remaining cusps, which are similarly sized; in another radula ( Fig. 20 E–F), lateral teeth always with four cusps; left M1 with three broad and triangular cusps, median one 1.3–1.5× more elongated than outer cusps; right M1 with four triangular cusps, cusp 1 much reduced, with length 49–60% of remaining cusps, which are similarly sized; M2–M6 with three main triangular, claw-like and equally-sized cusps in a posterior portion of radula, in addition to a fourth small cusp (cusp 1) that gradually strengthens towards the anterior portion of radula and may become equal in size to remaining cusps (at least in M3–M6), with right M5 being supposedly the first tooth to show a fully developed cusp 1; an additional fifth cusp may appear in M3 and M4 as an abnormal local asymmetry; M7 with four triangular, curved and similarly-sized cusps in a posterior region of radula, with cusp 1 gradually reducing in size and finally disappearing in the anterior region of radula, resulting in M7 with three cusps; M8 very narrow, with three finger-like cusps (median one 1.3–1.5× more elongated than outer cusps), fully formed only in the anterior region of radula; central tooth 3.6–3.8 µm wide, lateral teeth 3.8–4.1 µm wide, M1–M2 2.4–2.8 µm wide, M3–M6 (with three main cusps) 2.6–3.1 µm wide, M3–M6 (with four main cusps) 6.6–9.2 µm wide, M7 (with four cusps) 2.7–3.2 µm wide, M7 (with three cusps) 4.4–4.8 µm wide, fully developed M8 2.9–3.3 µm wide.

Remarks

Figured specimens show a gradual loss of coloration of the reddish-pigmented soft parts in N. verbernei after many years conserved in ethanol, from fresh specimens ( Fig. 19 A–B) to old ones ( Fig. 19 C–D). Rolán & Fernández-Garcés (1994) described the external morphology of N. verbernei and N. decollata ( Rolán & Fernández-Garcés, 1994) from Cuba as being translucent white with milk-white spots distributed on the dorsum. This could be a result of long-time storage of animals and consequent loss of pigmentation, or even suggest that N. verbernei from Brazil constitutes a different species than the Caribbean one (see below).

Rolán & Fernández-Garcés (1994) briefly described, but did not illustrate, opercula of N. verbernei and N. decollata , which are similar to those herein illustrated ( Fig. 19 E–F) by being multispiral and having a subcentral nucleus. The operculum of N. albogemmata Laseron, 1958 , illustrated by Marshall (1983), possesses a remarkably prominent peg accessory, which was not observed in N. verbernei from Brazil.

The radula of N. verbernei from Brazil has a variable number of cusps in some teeth, in addition to an abnormal local asymmetry. The peculiar arrangement of teeth rows in a distinct ‘V-shape’ generates a pattern in which one tooth is exactly situated in the center of the six teeth adjacent to it ( Fig. 20D ). Other genera of Triphoridae also seem to present a slight level of ‘V-shape’ arrangement of rows, but apparently never like the observed herein.

The most surprising feature of the radula of N. verbernei from Brazil is its radically different tooth morphology when compared to N. verbernei from Cuba and other species ( N. decollata , N. albogemmata and N. aff. albogemmata ). Main differences comprise the central tooth of N. verbernei from Brazil bearing three main cusps (instead of two, four, six or nine cusps), lateral teeth with up to five or six cusps (instead of seven or more cusps in remaining species) and the main three claw-like cusps of marginal teeth (which completely differ from the several elongated cusps of the hand-shaped marginal teeth in other species). The radular formula of N. decollata is 7-1-1-1-7 ( Rolán & Fernández-Garcés 1994), similar to the eight marginal teeth observed in N. verbernei from Brazil, whereas the radula of N. albogemmata and N. aff. albogemmata is 1-1-1-1-1 (as argued by Marshall 1983) or 2-0-1-0-2 (as argued by Nützel 1998). This extreme variation in the composition of the radula indicates that Nanaphora shows an atypical evolutionary flexibility in order to colonize new sponge hosts or, alternatively, it is constituted by different monophyletic lineages that are masked by a convergence of inflated and reduced shells ( Marshall 1983).

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. 19. Nanaphora verbernei (Moolenbeek & Faber, 1989). A–B, F. MNRJ 28956. C. MZSP 85022. D–E. MNRJ 33139. A–D. External morphology. E–F. Operculum. Scale bars: A–D = 500 µm; E–F = 100 µm.

Fig. 20. Nanaphora verbernei (Moolenbeek & Faber, 1989), radula. A–D. MNRJ 28956. E–F. MZSP 85022. Scale bars: A, E–F = 5 µm; B = 10 µm; C–D = 2 µm.