Mixtacandona Klie, 1938

Mazzini, Ilaria, Marrone, Federico, Arculeo, Marco & Rossetti, Giampaolo, 2017, Revision of Recent and fossil Mixtacandona Klie 1938 (Ostracoda, Candonidae) from Italy, with description of a new species, Zootaxa 4221 (3), pp. 323-340 : 328-335

Genus Mixtacandona Klie, 1938

Diagnosis of the genus (after Danielopol & Cvetkov 1979; Meisch 2000; Karanovic & Pesce 2000, Karanovic 2012): carapace 0.50–0.80 mm long, W<1/ 3 L. Fused zone of valves narrow, marginal pore canals rare. Valve shape in lateral view trapezoidal, triangular or elongated, surface smooth or slightly ornamented. A2 of male with or without male bristles, aesthetasc Y conspicuously long (±60% of first endopodal segment). Mxp-respiratory plate with three filaments. Male clasping organs only slightly asymmetrical. Cleaning leg 4- or 5-segmented; protopodite with three setae (d1, d2, and d p), seta f often present, distal segment with one long (h3) and two very short setae (h1 and h2). CR with short posterior seta. Hemipenis with a finger-shaped distal lobe, M-process absent. Eye pigment absent.

Mixtacandona idrisi n. sp. ( Figs 3–7 )

Note: authorship of the new species is attributed to IM and GR and should be cited as "Mazzini and Rossetti” in “Mazzini et al. " ( ICZN 2000, Recommendation 51E).

Type locality. Grotta degli Spiriti, Contrada Petrazzi, province of Palermo, Italy. Coordinates: 13°18’13”E, 38°08’54” N. Elevation: 130 m a.s.l. (Cimino et al. 2016). Karst cave with a development of 90 m in length, situated at the foot of the Cozzo Santa Croce carbonate rock relief, in the area of Mount Castellaccio. Collected by FM on February 0 7, 2012. Sample consisting of c. 40 adults and juveniles. No other fauna was found.

Type material. Holotype: ♂ (GR.731): soft parts dissected in glycerine in a sealed slide, valves stored dry in a micropalaentological slide (used for SEM imaging).

Paratypes: one ♀ (GR.729) dissected and stored as the holotype; valves used for SEM imaging; one ♂ (GR.730) with damaged RV; 5 adult ♀♀ stored in toto in ethanol (no numbers).

Derivatio nominis. We take pleasure in naming this species after the given name of Idris Amal, GR’s son. Moreover, since this species was found near Palermo, by a lucky coincidence its name can also be associated with Muhammad al-Idrisi (1100–1165), a preeminent geographer who worked at the court of the Norman king Roger II of Sicily. The kingdom had its capital in Palermo, and was renowned for its multi-ethnic character, religious tolerance, and as a centre for the flourishing of arts and sciences. In 1154 al-Idrisi published the Tabula Rogeriana ("The Book of Roger" in Latin), containing a description in Arabic of the world and a world map. It is regarded as one of the most important scientific findings of the Middle Ages. For the following three centuries geographers copied al-Idrisi’s maps without substantial changes.

Measurements (in µm). GR.729 (♀): LV: L = 500, H = 230; RV: L = 480, H = 230.

GR.731 (♂): LV: L = 510, H = 230; RV: L = 500, H = 220.

Diagnosis. Small sized Mixtacandona with an elongated, low trapezoidal lateral outline (♀: H/L = 0.47; ♂: H/ L = 0.44). Valve surface smooth. Fifth segment of A1 with a long ventral seta largely exceeding distal tips of terminal claws. Aesthetasc Y on A2 as long as the first endopodal segment. A2 of male without bristles. Seta f on T2 present. T3 with a four-segmented endopodite.

Description. Carapace and valves. Cp in lateral view ( Figs 3 , 4 a–c) with elongate sub-trapezoidal shape. Greatest H slightly less than ½ L and located slightly behind mid length. LV: Dorsal margin with the central part gently arched, anteriorly slightly sloping more steeply than posteriorly. Greatest length just below mid-height. Anterior and posterior margins rounded. The antero-dorsal margin more pronounced than the postero-dorsal one. Ventral margin with a slight but distinct convexity in the middle. Calcified part of the inner lamella wide anteriorly. RV ( Fig. 4 c, d): general outline as in LV, but less high. Ventral margin concave. LV overlaps RV ventrally. Simple hinge, with smooth hinge bar ( Fig. 4 e) and groove ( Fig. 4 c, d). Surface of valves smooth. Central muscle scar arrangement as characteristic for the tribe Candonini ( Fig. 4 f).

Appendages. 1 ( Fig. 5 A): first segment with two long dorsal setae, a short seta at about 2/3 of the ventral margin, and a ventral-apical spine; second segment with a ventral seta in sub-apical position; third segment with one apical, ventral seta; fourth segment with a dorsal and a ventral seta, the latter about three times as long as the former one; fifth segment with a dorsal seta and a long ventral seta greatly exceeding distal ends of terminal claws of next segments; sixth segment with two ventral setae, the longest slightly surpassing the distal end of claws on next segment, and two shorter, sub-equal setae inserted dorsally. Terminal segment with three sub-equal, apical setae of which the intermediate one (G) weakly sclerotized, and an aesthetasc (y a) of about the length of the shortest seta on the same segment. Rome and Wouters organs not seen.

A2. Male ( Figs 5 B,C): Protopodite two-segmented (not figured). Exopodite with one long seta roughly reaching the distal end of the next segment and two tiny, lateral setae. Endopodite three-segmented, second segment subdivided. First segment with a long, ventral seta inserted proximally, an aesthetasc (Y) as long as the segment placed at c. 1/4 of the ventral margin, and two ventro-apical setae having a length ratio of 1:2.5; proximal part (2A) of second segment bearing a sub-apical dorsal seta, three apical setae more centrally of which one very short (t1) and two sub-equal, not bristle-like setae with folded ends (t2-3), and in ventro-apical position a long seta and an aesthetasc (y1); distal part of second segment (2B) with two stout, sub-equal apical claws (G1 and G3), more dorsally another claw (G2) about 1/3 as long as the previous ones, three tiny setae (z1-3) in sub-apical position, and a ventro-apical aesthetasc (y2); third segment with two claws, one (G m) about 70% the length of the other (G M), and an apical aesthetasc (y3) ventrally. Female ( Figs 7 A, B): Endopodite three-segmented, second segment undivided. Second segment with unfolded, unequal setae t1-4, all exceeding the distal margin of the next segment; seta z3 about twice as long as setae z1-2.

T1 ( Fig. 6 A, B): male prehensile palps slightly asymmetrical; gooseneck-like processes distally expanded in rounded projections carrying small setae; left process more bumped than right one.

T2 ( Figs 6 C; 7C): protopodite two-segmented (not figured) with no setae. Endopodite four-segmented. First segment with no setae; second and third segments with short setae (f and g) inserted apically and sub-apically, respectively; fourth segment with a stout, terminal claw (h2) slightly longer than the three distal endopodial segments, flanked by two tiny, sub-equal setae (h1 and h3) inserted apically.

T3 ( Fig. 6 D; 7D): protopodite with one interior seta (d p) and two exterior setae (d1-2), and a short spine (see arrow) along the distal margin. Endopodite four-segmented; first two segments without setae, third segment with a tiny seta (g); fourth segment with three apical setae, the first one (h1) very tiny, the second one (h2) shorter than the distal endopodial segment, and the third one (h3) robust and slightly shorter than the endopodite.

CR ( Fig. 6 E; 7E): posterior margin with a short spine (see arrow) inserted proximally and a seta (S p) at about 3/ 4 of its length; anterior seta (S a) strongly reduced; anterior distal claw (G a) slightly longer than the posterior one (G p), about half the length of the ramus.

Hemipenis ( Fig. 6 F): peniferum with fingerlike outer lobe (a), thinner and S-shaped distally; distal part of median lobe (h) with gently rounded outer margin and crooked inner margin; inner lobe (b) thumblike, the distal end with an inner margin more curved than the outer one and bent toward the lateral side. M-process absent.

Zenker organ (not figured) with seven whorls of spines (see remark below).

Eye pigment absent.

Other appendages as typical for the genus.

Remarks. i —For its valve shape and size, Mixtacandona idrisi n. sp. cannot be unambiguously placed in any of the described species-groups of the genus, since it presents a combination of characteristics found in the hvarensis and riongessa groups.

ii —The holotype GR.731 has four whorls of spines in the Zenker organ. This has to be considered as a malformation: although in the Candoninae most of the formation process of the Zenker organ takes places after the moult to adulthood, the number of whorls remains constant in adults ( Yamada et al. 2014). The paratype GR.730 bears seven whorls, as typical for the subfamily.

iii —The sex ratio in the collected sample is highly female biased (approximately 1:5).

Differential diagnosis. Mixtacandona idrisi n. sp. can be easily distinguished from its congeneric species by its valve outline, in particular from those assigned to the laisi-chappuisi, hvarensis and riongessa species-group all displaying a smooth valve surface. The species belonging to the laisi-chappuisi species group have a rectangular to trapezoidal surface [as M. laisi , M. chappuisi (Klie, 1943) , M. stammeri (Klie, 1938) , M. transleithanica (Löffler, 1960) , M. botosaneanui Danielopol, 1973 and M. loeffleri Danielopol, 1973 ]. The species belonging to the hvarensis species-group have a triangular outline [ M. hvarensis (Danielopol, 1969) and M. pietrosanii Danielopol and Cvetkov, 1979 ] and a medium size (maximum length> 0.7 mm) whereas the species belonging to the riongessa group have a triangular outline and a small size (maximum length <0.7mm). In addition, almost all species belonging to the above-mentioned species groups have greater valve lengths (± 0.56 mm). In particular, M. peliaca (Schäfer, 1945) is slightly longer (0.52 mm) with straight dorsal and ventral margins. M. pseudocrenulata (Schäfer, 1945) (length = 0.54 mm) exhibits a more elongated outline and a symmetrical curved dorsal margin (see also Fig. 10 I in Danielopol 1980b). M. transleithanica (Löffler, 1960) (length = 0.55 mm) displays a rounded dorsal margin and a straight ventral margin. Mixtacandona idrisi n. sp. can be also differentiated by the combination of chaetotaxic character details reported above.

Distribution. The species is known from its type locality only.

Figures

FIGURE 3. Optical microscope image (right lateral view) of an adult ♀ of Mixtacandona idrisi n. sp. stored in ethanol. Scale bar: 50 µm.

FIGURE 4. Mixtacandona idrisi n. sp., GR 731, adult ♂: A) LV, exterior lateral view (0.51 / 0.23); B) RV, exterior lateral view (0.50 / 0.22); GR 729, adult ♀: C) LV, interior lateral view (0.50 / 0.23); D) RV, interior lateral view (0.48 / 0.23); E) LV, detail of the hinge; f) LV, detail of the central muscle scar. Scale bars: 100 µm for A – D; 50 µm for E, F.

FIGURE 5. Mixtacandona idrisi n. sp., GR 731, adult ♂: A) A 1; B) A 2; C) detail of distal part of A 2 endopodite. Scale bar: 50 µm for A, B; 29 µm for C.

FIGURE 6. Mixtacandona idrisi n. sp., GR 731, adult ♂: A) right T 1 prehensile palp; B) left T 1 prehensile palp; C) T 2; D) T 3; E) CR; F) hemipenis. Scale bar: 65 µm for A, B; 55 µm for C; 50 µm for D, E; 85 µm for E.

FIGURE 7. Mixtacandona idrisi n. sp., GR 729, adult ♀: A) A 2; B) detail of distal part of A 2 endopodite; C) T 2; D) T 3; E) CR. Scale bar: 65 µm for A; 32 µm for B; 50 µm for C; 76 µm for D, E.