Vestalenula carinata, Pinto, Ricardo L., Rocha, Carlos E. F., Rossetti, Giampaolo & Martens, Koen, 2013

Pinto, Ricardo L., Rocha, Carlos E. F., Rossetti, Giampaolo & Martens, Koen, 2013, Contribution to the knowledge of the genus Vestalenula Rossetti & Martens, 1998 (Crustacea, Ostracoda, Darwinulidae), with the description of a new species, V. carinata n. sp., from the island of Florianópolis, Brazil, Zootaxa 3666 (1) : -

Vestalenula carinata n. sp.

( Figs. 1–2 )

Type material. Holotype: a dissected ovigerous female. Valves stored dry in a micropaleontological slide and soft parts mounted in a permanent slide with CMC-9AF mounting media (Masters Company Inc., Bensenville, Illinois, USA). (MZUSP28271)

Paratypes: ovigerous female prepared and stored like the holotype, but with valves coated for scanning electron microscopy (MZUSP28272); ovigerous female dry, coated for scanning electron microscopy and stored in a micropaleontological slide (MZUSP28273).

Type locality. Costão do Santinho, Morro das Aranhas, Municipality of Florianópolis, Santa Catarina State, Brazil. GPS coordinates: 27°28’17,4”S 48°22’38,1”W.

Wet leaves collected manually by the margin of a small stream that runs through the forest and crosses, near the top of the hill, the track that goes from Santinho beach up to the summit. Material collected on 26 October 2004 by CEFR and RLP.

Etymology. This species is named on account of its characteristic long ventral keel. From the feminine Latin word carinata (masculine carinatus), meaning keeled.

Diagnosis. Small to medium sized darwinulid (c. 400 µm), with carapace elongated in lateral view (Le/H = 2.17). RV with very long ventral keel (c. 40% of the valve length) and LV with long antero-ventral tooth. Cms anteriorly positioned, consisting of 8 spots arranged in circular rosette. A1 with long seta on the third segment (without ventro-apical seta). A2 exopodite with one seta and a lateral spine; first endopodal segment with one ventro-apical seta. Penultimate segment of Md-palp with seta y short and seta z extending beyond the tip of last segment; this latter only with setae b and c present (seta a absent). CR consisting of a conical base bearing a seta. Pabd absent.

Description of female. Cp ( Fig. 1 G–I). Elongated in lv (Le/H = 2.17), medium sized, with whitish surface, sparse sensilla and shallow pits, the latter concentrated mainly on the medio-ventral area; LV overlapping RV on all sides; dorsal and ventral margins straight, running parallel to each other along most of their lengths; caudal margin broadly rounded; anterior margin rounded, slightly produced towards the ventral side; in dorsal and ventral views, quite long and narrow, slightly constricted in the middle; dorsal margin straight in dorsal view; overlapping ventral margin of left valve sinuous in ventral view. Hinge adont.

LV ( Fig. 1 A, C, E). With elongated antero-ventral tooth; in internal view, caudal margin evenly rounded; anterior margin broadly rounded, slightly produced towards the ventral side; ventral and dorsal margins straight, running parallel to each other along most of their lengths; cms nearer to the anterior margin, consisting of 8 spots arranged in an approximately circular patch: seven elongate scars arranged biserially (three anterior to an approximately vertical centre-line, four posterior to it) with an eighth rounded-triangular one inserted ventrally.

RV ( Fig. 1 B, D, F). With very long ventral keel (c. 40% of the valve length); in internal view, caudal margin evenly rounded; anterior margin slightly pointed, produced towards the ventral side; ventral and dorsal margins straight, running parallel to each other along most of their lengths; cms nearer to the anterior margin, consisting of 8 spots arranged in an approximately circular patch: seven elongate scars arranged biserially (three anterior to an approximately vertical centre-line, four posterior to it) with an eighth rounded-triangular one inserted ventrally.

A1 ( Fig. 2 A). First segment with dorsal seta; second segment with two ventral seta, one approximately three times as long as the other one; third segment with a long dorso-apical seta (S1); fourth segment with a long dorsoapical seta (S2) and a small α-seta; penultimate segment with a small α-seta, with three medium sized and one long setae; terminal segment with two apical setae (the most dorsal twice as long as the most ventral one), one α-seta and one dorsal aesthetasc sub-apically inserted.

A2 ( Fig. 2 B). First segment of protopodite with two setae; second segment of protopodite with a long seta; exopodite with one seta and a lateral spine; first endopodal segment with a group of four ventral aesthetascs proximally inserted and with a long ventro-apical seta; second endopodal segment a with medio-ventral aesthetasc (y1) and a ventro-apical aesthetasc (y2), a short seta z3, a medium sized claw z2 and a long claw z3, claw G2 small, claw G1 long and claw G3 a medium sized slender seta; last endopodal segment with long claw Gm and short claw GM, the latter more dorsally inserted than the first one.

Md coxa similar to other species in the genus. Md-palp ( Fig. 2 C) first segment with 8 rake setae, penultimate segment with medium sized setae w and x (both equally long), seta y short and seta z very long; terminal segment externally with a subapical seta b and apically with five claws and a small seta c.

Mx 1 ( Fig. 2 D–F). Medially with a long seta and three endites, the distal one carrying three stout and pilose setae and five slender setae; externally with a well developed respiratory plate bearing 26 long rays and four setae reversed towards the front; palp distally widened, subdivided in two segments, the proximal one with a mediolateral seta, four apical setae and a medial seta just below the insertion of last segment; terminal segment small, with two long and one short setae.

T1 ( Fig. 2 G). Endopodite three segmented: first segment with two ventro-apical setae; second segment with an apical seta; terminal segment with two lateral setae, one ventral and one dorsal, and a long terminal claw.

T2 ( Fig. 2 H). Protopodite with three ventral setae, one proximal and two apical; endopodite four segmented: first segment with two ventro-apical and a medial setae; second segment with a stout ventro-apical seta; penultimate segment with a slender ventro-apical seta; terminal segment with two lateral setae, one ventral and one dorsal, and a long apical claw.

T3 ( Fig. 2 I). Protopodite with two ventro-apical setae; endopodite four segmented: first, second and third segments with a long ventro-apical seta each; last segment with a long apical claw and two lateral setae, one short, dorsally inserted, and one long, ventrally inserted.

End of the body ( Fig. 2 J). CR consisting of a small conical base bearing a seta; P-abd absent.

Males unknown.

Measurements. Specimen MZUSP28273: Cp: Le = 398 µm; H = 183 µm; W = 191 µm.

Specimen MZUSP28272: LV: Le = 419 µm; H = 195 µm.

RV: Le = 409 µm; H = 193 µm.

Remarks. Vestalenula carinata n. sp. can be easily differentiated from other species in the genus by its small size (c. 400 µm) combined with a very long ventral keel on the right valve (c. 40% of the valve length). Remarkably, however, V. c ar i n at a n. sp. perhaps shares characters with the enigmatic marine darwinulid Semidarwinula terraenuxforma Choe, 1988 and this potential affinity will be further developed in the discussion.

Figures

FIGURE 1. Vestalenula carinata n. sp., scanning electron microscopy of carapace and valve details. A. Left valve, internal view (paratype, MZUSP 28272). B. Right valve, internal view (idem). C. Left valve, internal view, detail of anterior tooth (idem). D. Right valve, internal view, detail of posterior keel (idem). E. Left valve, internal view, detail of central muscle scars (idem). F. Right valve, internal view, detail of central muscle scars (idem). G. Carapace, right lateral view (paratype, MZUSP 28273). H. Carapace, dorsal view (idem). I. Carapace, ventral view (idem). Scale bars: A – B, G – I = 100 µm; C – D = 50 µm; E – F = 20 µm.

FIGURE 2. Vestalenula carinata n. sp., line drawings of appendages, holotype (MZUSP 28271). A. Antennula. B. Antenna. C. Mandibular palp. D. Maxillula. E. Maxillula, first endite. F. Maxillular palp. G. First thoracopod. H. Second thoracopod. I. Third thoracopod. J. End of body. Scale bars: A – C, F – G = 20 µm; D, H – I = 30 µm; E = 10 µm.