Strobiligera gaesona (Dall, 1927),

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: 43-46

publication ID

https://doi.org/10.5852/ejt.2019.517

publication LSID

lsid:zoobank.org:pub:CAC6F8AF-ED37-4989-9672-68316920750B

persistent identifier

http://treatment.plazi.org/id/426387C8-B456-FFC1-FD8F-FB9198CBFD9B

treatment provided by

Plazi

scientific name

Strobiligera gaesona (Dall, 1927)
status

 

Strobiligera gaesona (Dall, 1927) 

Figs 2KView Fig, 28–29View FigView Fig

Material examined

BRAZIL – Ceará State: [2, 1 d] specs; Canopus Bank ; 02°14´25″ S, 38°22´50″ W; 240–260 m depth; 2005; MZSP 53685GoogleMaps  [1, d] spec. same data as for preceding; MZSP 53697GoogleMaps  .

Description of basic anatomy

EXTERNAL MORPHOLOGY. Body yellowish-white, covered by minute white dots in the posterior whorl adjacent to head-foot.

OPERCULUM. Yellowish, elliptical, moderately thin but rigid, semi-transparent, 3.25 distinct whorls, nucleus slightly eccentric, dislocated ~32% from center towards margin; diameter of operculum does not significantly exceed diameter of opercular pouch.

JAW. Outer side with robust scales, rhombus-shaped, rectangular or rectangular-lanceolate, covered by micro-pores up to 380 nm in diameter; scales of outer side 14.9–21.2 µm long, 7.9–9.5 µm wide, ratio length/width 1.6–2.4 (rhombus-shaped), 10.3–11.3 µm long, 4.4–4.8 µm wide, ratio length/width 2.3–2.4 (rectangular), 11.8–17.6 µm long, 4.2–6.4 µm wide, ratio length/width 2.7–3.3 (rectangular/lanceolate).

RADULA. Formula not discernible, without clear differentiation of central, lateral and marginal teeth, but at least 30 scissor-like teeth per row, frequently overcrowded in its central portion; teeth typically with three cusps, two elongated/curved ones and a smaller marginal cusp positioned sometimes on the left margin, other times on the right margin, with the change of side of the marginal cusp being prone to occur more than once in the same row; the length of marginal cusp greatly varies, often 25–70% of length of main cusps, but it can be reduced until totally disappear or even reach same size of other cusps; rare teeth with two cusps have one cusp longer than the other; rare teeth with four cusps have inner cusps more elongated than outer ones (which reach 43–85% of length of inner cusps), in some cases with an internal diastema between inner cusps; abnormal teeth of three cusps with a much reduced size may be present in a central portion of row; teeth with three cusps typically 2.0– 3.9 µm wide, but abnormally reduced teeth as little as 1.5 µm wide may occur; teeth with two cusps 1.1–1.5 µm wide; teeth with four cusps 2.3–3.5 µm wide.

Remarks

Even being an upper bathyal species, S. gaesona  possesses distinct eyes ( Fig. 28AView Fig). The elliptical operculum seems to be a common feature of the genus, with the nucleus of S. gaesona  being apparently not as eccentric as in S. lubrica ( Bouchet & Warén, 1993)  . The operculum of S. gaesona  is yellowish ( Fig. 28BView Fig), similar to the ‘light tan’ color described for S. lubrica ( Bouchet & Warén 1993)  .

The scissor-like tooth morphology of S. gaesona  is peculiar, with undifferentiated teeth and a typical tooth bearing three claw-like cusps, two longer and one external (right or left) smaller cusp, with rare variations of two or four cusps ( Fig. 29View Fig). This radula is nearly identical to those of S. brychia ( Bouchet & Guillemot, 1978)  and S. lubrica  , although the total number of teeth per row could not be determined in S. gaesona  . The radula of S. brychia  also shows teeth with two to four cusps, and teeth with three cusps having the smaller cusp positioned to the left or to the right ( Bouchet 1985), although the reduced cusp in S. brychia  seems to be even shorter than in S. gaesona  . The radula of S. lubrica  was described as possessing teeth mainly with two claw-like cusps, but outer marginal teeth with a third cusp; however, teeth with two and three cusps (two long, one small cusp) can be found together ( Bouchet & Warén 1993: fig. 1284).

The great similarities of operculum and radula between species of Strobiligera  with paucispiral ( S. gaesona  ) and multispiral ( S. brychia  and S. lubrica  ) protoconchs eliminate any suspicion that both groups could belong to different genera ( Fernandes & Pimenta 2014).