Sarsilatona fernandoi Rane 1983
Creators: name: Korovchinsky, Nikolai M.
Publisher: name: Zenodo
Year: 2011
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Branchiopoda
Diplostraca
Sarsilatona
Sarsilatona fernandoi

description: Sarsilatona cf. fernandoi (Rane, 1983)
Description. Parthenogenetic female. Size 1.31–1.73 mm. Body massive, high, oval-elongated with a rather large and high head (28.7–35.2% of body length) (Fig. 1 A). Eye comparatively small (7.0–8.1% of body length), situated closer to dorsal head margin and contains 55 ommatidia. Ocellus large, situated near base of antennules. Antennules (Fig. 1 B) of moderate size (18.3–21.6% of body length) with nine aesthetascs at the end of basal part near sensory seta which is thick, without setules but bearing small denticles along its sides (Fig. 1 C).
Swimming antennae long (60.2–67.1% of body length) with massive basipodite, having a small rounded outgrowth on posterior side (Figs. 1 A, H) and long, distally setulated seta on dorsal side of its base (Fig. 1 I). Distal part of antennal basipodite bears rather long and stout spine on its outer side in front of lower branch, small prominence in front of upper branch, and stout curved thorn dorsally (Fig. 1 D). Inner side of basipodite distal end bearing long feathered seta (Fig. 2 A). Proximal segment of upper two-segmented antennal branch (exopodite) with rather long stout spine, thicker curved thorn inside of it, and small triangular outgrowth in more ventral position (Fig. 1 E). Distal segment of the branch clearly articulates with previous one externally while internally these two segments seem more fused. Distal segment bears two small prominences proximally in front of thick curved thorn of proximal segment (Fig. 1 E) while apically it has two large spines, and small prominences near them (Figs. 1 F, G). All lateral setae of both segments (20.4–22.2% of body length) armed uniformly with rather stout setules of swimming type especially densely setulated distally. Two slightly longer apical setae armed proximally with similar setules but distally with thin, more sparcely situated setules of sensory type (Fig. 1 M). In lower three-segmented antennal branch (endopodite) small proximal segment clearly articulates with the following one externally but seems fused with them internally (Fig. 2 A). Second segment of the branch is more developed, long and stout, bearing apically one seta of moderate length (27.7% of body length) and strong spine (Fig. 1 J). Distal segment of this branch is small and bears four setae, the ventralmost of which is stronger than others (26.9% of body length), and two small thorns situated internally near its base (Fig. 1 J, K). These two stouter setae occupy most ventral position; they are setulated almost up to their ends, which are naked and terminally supplied with hooks (Fig. 1 L). Three other setae of distal segment are thinner and almost of the same length as previous ones, distally they bear setules of sensory type (Figs. 1 J, M). Formula of antennal setae (6–7) – (9–11)/ 0–1–4.
Mouth parts consist of labrum (Fig. 2 B), maxillules (mx I) each with eight densely setulated feathered setae in one row incurved forward and one larger seta near them terminally (Fig. 2 C), small maxillae (mx II) (Fig. 2 D) situated just near base of tl I and having short seta near its apical end, and mandibles. Molar surface of right mandible (Fig. 3 B) rather wide, concaved dorsally, with a group of four-five terminally branched outgrowths (pegs Pe) posteriorly. A long row of 12–13 sharply delineated laterally but generally poorly expressed pales (Pa) densely fused with diagonals (D) marginally. The latter ones occupy most of molar surface being supplied with numerous pores. Fishbones (Fb) are poorly developed posteriorly being also mostly fused with diagonals; anteriorly there are three large rounded outgrowths. Molar surface of left mandible (Fig. 3 A) with a small group of pegs, consisting of two large and some small ones between and near them, at its posterior angle. A row of three pales with finger-like prominences, which is hardly delineated further anteriorly. A group of long forked fishbones (Fb) between pegs and pales, and probably another group of them situates ventrally. 12–13 diagonals (D), diminishing in size anteriorly, occupying most part of molar surface.
Shell with arched dorsal side and rather short ventrally prominent posterior margin smoothly connected with ventral margin (Figs. 1 A). Anterior valve margin with eight–ten setulated setae directed outwards (Fig. 2 E). The uppermost of them, five or six in number, are especially long and sit on developed conical bases. The following 13–14 setae on the postero-ventral margin appear directed forward (Fig. 2 E) and ventral margin bears only thin densely situated setules (Figs. 2 E, F). On the posterior part of ventral valve margin, long feathered setae appear again with setules between them (Fig. 2 G). Inner side of postero-ventral valve margin with four–five feathered setae, two especially long naked setae (they were broken in all specimens) set on massive and curved bases, and two–three clusters of spinules (Figs. 2 H, I). Inner row(s) of spinules goes along posterior valve margin.
Six pairs of thoracic limbs, all with epipodites. Their structure and armament are shown in Table 1. Exopodite of tl I is comparatively narrow at its end (Fig. 5 A) while from tl II to tl VI it is widened terminally (Figs. 2 J, 5C), especially in tl IV, which bears one seta more than previous ones, and tl V. Endopodites from tl I to tl V are more or less clearly subdivided in four parts (“segments”), the proximal of which (I) is largest, bearing numerous filtering setae, while three terminal segments bear from three to six such setae. Terminal part (IV) from tl I to tl V and subterminal part (III) from tl II to tl V bear also outer setae each, similar with those of exopodite, of which the former one is especially long (Figs. 5 A, C, arrows). Large proximal part of endopodite (I) of tl I also possesses terminally two naked setae, the anterior of which is longer than posterior one (Fig. 5 A, “ns”). A row of comparatively long rough setules along outer side of endopodite (Figs. 5 A, C) and a group of long spines on inner anterior basal side of tl I (Fig. 5 B). Gnathobase of tl I (Fig. 5 A) has outer row of 13 filtering finely setulated setae, inner long two-segmented setae near distal corner with rough setules distally and fine setules proximally, and another much smaller seta, curved downwards near the previous one. Gnathobases from tl II to tl V (Fig. 5 D) with row of 21–23 very finely setulated filtering setae, ending with one naked setae (p), and distally with two setae of different type, one of which is long and two-segmented (I), resembling that one of tl I, and another one is strongly modified, being hooked terminally and denticulated laterally (J) (Fig. 5 E). Tl VI (Fig. 2 J) is small and strongly modified. Its exopodite has been reduced up to terminal plate, arming with five marginal setae and two large thorns near bases of two of these setae. Endopodite is almost entirely fused with exopodite, bearing seven similar setae and one thorn between them. Gnathobase (Fig. 2 J, K) with two long setae and thorns of different shape.
I 6 + 5 (n 5 + 1) + (( n 4) + (n 4) + (n 22−24 + 2 distal naked setae) n 12−13 + (I + i)* + Postabdomen comparatively short (16.3–20.5% of body length) and high (9.2–11.4% of body length) with long setae natatoriae (about 50% of body length) sitting on two separate bases (Figs. 4 A, C, E, F). Row of 11–14 clusters of anal teeth along each lateral side, mostly with 3–4, rarely 2, 5 or 6 teeth in each cluster. A row of spinules below the row of clusters of anal teeth. Groups of comparatively large spines and clusters of spines near bases of postabdominal claws and anal opening (Fig. 4 D). Postabdomen bears dorsally three large conical outgrowths, the distalmost of which may be double or terminally subdivided (possibly this may be a deformity) (Fig. 4 A, C, E, F). Much smaller poorly developed outgrowth is present distally, closer to base of claws (Fig. 4 C, F, arrows), in another case, it looks lacking (Fig. 4 A, B). Postabdominal claws with three long basal spines of almost equal size, rows of spinules below them, and a long row of spinules along outer lateral side (Fig. 4 B). A row of comparatively large denticles along their inner proximal side (Fig. 4 D).
Juvenile females. They differ from adults in smaller body length (0.72–1.14 mm), fewer antennal setae (minimal number 4–8/0–1–4, more frequently (4–6)–(8–9)/0–1–4, which sometimes are accompanied by setae rudiments, and fewer clusters of anal teeth (8–10 with 2–3 teeth in each cluster).
Male. Unknown.
Remarks. The studied Vietnamese specimens are generally similar to S. fernandoi originally described from Central India (Rane, 1983), especially in presence of the characteristic dorsal outgrowths of postabdomen as well as small number of clusters of spinules near the ventro-posterior valve margin, and similar number of anal teeth in each cluster. Thus, the conspecificity of Indian and Vietnamese specimens seems to be highly probable. At the same time, some important features of the former ones remain unknown.
The Indian specimens are larger (up to 2.34 mm) and consequently have more numerous setae of upper antennal branch (9–10 /12), clusters of anal teeth (14–16), and dorsal postabdominal outgrowths (up to five ones proximally). Few other features—if adequately imaged in previous descriptions (see Rane 1983 and Sharma & Sharma (1990) —like presence of larger distal outgrowth of postabdomen and the conspicuous difference in size between basal claw’s spines seem also distinguish these specimens from those from Vietnam but have no substantial significance.
Differential diagnosis. S. cf. fernandoi differs from all others species of the genus in presence of only small denticles, not setules, on the sensory seta of antennules.
From S. papuana (Daday, 1900) it differs also in presence of dorsal outgrowths of postabdomen, thinner spine on the distal, dorsal side of antennal basipodite, and thinner and longer spine on the apical end of proximal segment of upper antennal branch.
It especially resembles S. serricauda (Sars, 1901) in presence of large dorsal postabdominal outgrowths but differs from the latter in shorter antennules (18.3–21.6% instead of 24.0–25.8% of body length), presence of setules, not small denticles, on the ventral valve margins, more numerous anal teeth in each cluster (> 4), and less numerous (max. 3 instead of 4–5) and thicker clusters of spinules near ventro-posterior valve margins.
In comparison with S. behningi Korovchinsky, 1985, it has longer antennules, thinner dorsal spine on the basipodital distal end, and thinner and longer spines on the distal end of proximal segment of upper antennal branch. Dorsal postabdominal outgrowths of the latter species are more developed as well as clusters of anal teeth (3–6 teeth instead of 2–3 in each of them), and clusters of spinules near the postero-ventral valve margins, which however are less numerous (max. 3 instead of 3–7).
description: Published as part of Korovchinsky, Nikolai M., 2011, Description of Sarsilatona cf. fernandoi (Rane, 1983) (Crustacea: Cladocera: Sididae) found in the south of Vietnam, pp. 29-38 in Zootaxa 3129 on pages 30-37, DOI: 10.5281/zenodo.205477