Leydigia (Neoleydigia) korovchinskyi, Kotov & Alonso, 2010

Kotov, Alexey A. & Alonso, Miguel, 2010, Two new species of Leydigia Kurz, 1875 (Chydoridae, Cladocera) from Spain, Zootaxa 2673 (1), pp. 39-55 : 45-53

publication ID	https://doi.org/ 10.11646/zootaxa.2673.1.2
persistent identifier	https://treatment.plazi.org/id/039C87F2-FF85-A078-27EC-FBEBFA8F7136
treatment provided by	Felipe
scientific name	Leydigia (Neoleydigia) korovchinskyi
status	sp. nov.

Treatment

Leydigia (Neoleydigia) korovchinskyi View in CoL sp. nov.

( Figs 4–8 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 View FIGURE 8 )

Etymology. The species is named in honor of Dr. N. M. Korovchinsky, renowned recent investigator of the Cladocera , who proposed to apply the hypothesis of “ejected relicts” to the Cladocera ( Korovchinsky 2006) . Our finding of this new taxon seems to be a new evidence confirming this idea.

Type locality. Chaparral Lagoon , Millanes, Cáceres, Extremadura, Spain (39º51’16”N, 5º33’38”W). Date of collection: May 2010 GoogleMaps .

Type material. Holotype. Undissected parthenogenetic female preserved with 4% formaldehyde in a vial deposited in the MNCN (accession number: 20.04/8555).

Allotype. Undissected mature male preserved with 4% formaldehyde in a vial deposited in the MNCN (accession number: 20.04/8556).

Paratypes. Ten parthenogenetic females, ten mature males and two ephippial females preserved with 4% formaldehyde in a vial deposited in the MNCN (accession number: 20.04/8557) . 15 females in males in the personal collection of A. A. Kotov, Moscow, Russia, AAK 2010-027 .

Diagnosis. Parthenogenetic female. Body subovoid, postero-dorsal angle ill-defined. Coarse striation on valves absent, a fine striation well-expressed. Ocellus slightly larger than compound eye. PP = 3–4 IP, lateral head pores semi-lunar, about 0.7–0.8 IP distance from midline. Labral keel triangular-ovoid, with rounded apex, its anterior margin with fringe of relatively short setules not reaching apex; on sides of keel there are 4 or 5 lateral groups of somewhat longer setules. In middle of ventral margin rudimentary denticles (remainders of setules) between bases of setae. Submarginal setules in middle portion of posterior margin located sparsely and far from the margin. “Setules” of marginal membrane very small. Postabdomen subovoid, preanal margin shorter than anus, somewhat undulated, preanal and postanal angles well defined, neither distal margin nor dorso-distal angle on postabdomen. Postanal marginal denticles in about 20–24 clusters, about 6 or 7 fascicles of stout lateral setae, 3–5 setae in each fascicle on distal portion. Postabdominal claw with a basal spine about 1/3–1/2 of claw diameter at base.

Antenna I not reaching tip of rostrum, with 4 transverse rows of long setules on anterior face, stout setules at its end; sensory seta arising at distance of 1/5–1/6 of appendage length from distal end. Largest aesthetasc about half as long as appendage, reaching tip of rostrum. Antenna II with 3 stout spine-like setules on first and on second endopod segments. Trunk limb I with ODL seta with distal segment unilaterally armed with short, sparce setules; IDL with three clusters of short marginal setules, three medial clusters of short setules, and three bisegmented setae, shortest seta naked, two longer setae with long setules, on limb corm seta 1 of size similar to that of soft setae a–c, seta 2 short, seta 3 rudimentary. On trunk limb II, distalmost scraper 1 without setules on basal segment, located on a distal lobe. Trunk limb III with exopodite bearing seven setae, distal seta 1 with long setules, seta 2 with distal segment armed by setules alternated in size, lateral setae 3–7 armed in similar manner, but setae 3–4 short; filter plate III with eight setae. Trunk limb IV with subovoid exopodite bearing six setae, seta 1 and 2 short, armed by short setules. Inner face of limb V, two setulated setae of unequal length, distal armature of gnathobase a setulated lobe, 'filter plate' with two small setae.

Ephippium. All surface of ephippium covered by a fine striation as in parthenogenetic female, but within reticulation polygons there are rows of minute depressions along each line of the striation, forming a pattern more similar with that on a beetle wing cover.

Adult male. Body low, elongated. Postabdomen elongated, remarkably narrowing distally, with almost straight ventral margin; preanal margin short, slightly undulated; distal margin not defined. Penis slightly thicker and shorter than claw, each gonopore opening on short, somewhat narrowing projection. Antenna I with sensory seta as in female, male seta located distally, 12 aesthetascs. Limb I copulatory hook bears three ridges at its tip; ODL seta shorter than that in female, armed by fine setules; IDL with three setae of unequal size and two small hillocks. Portion of limb near the copulatory hook inflated and supplied with copulatory brush of rather short, strong setules; copulatory brush seta short, with inflated basal part.

Size. Parthenogenetic females up to 0.99 mm, ephippial females 0.94 mm, adult males 0.64 mm.

Description. Parthenogenetic female. General. In lateral view body subovoid, maximum height in middle ( Fig. 4A View FIGURE 4 ). Dorsal margin slightly convex in posterior part, postero-dorsal angle ill-defined. Posteroventral angle completely rounded; ventral margin regularly convex. Coarse striation on valves absent, valves with an obscure polygonal reticulation, a well-expressed fine striation present within the reticulation cells ( Fig. 4B View FIGURE 4 ).

Head relatively small, triangle-round in lateral view, with short, blunt, downward pointing rostrum ( Fig. 4C View FIGURE 4 ). Ocellus slightly larger than compound eye, distance from tip of rostrum to ocellus significantly more than that between ocellus and eye.

Head shield relatively narrow, covered by fine striation, in posterior portion three closely located major head pores of subequal size, with connection between them, PP = 3–4 IP ( Fig. 4D–F View FIGURE 4 ). Lateral head pores semi-lunar, located at about 0.7-0.8 IP distance from midline, somewhat posterior to level of central major head pore, all head pores located on a plate without striation ( Fig. 1E View FIGURE 1 ).

Labrum with large medial labral keel, triangular-ovoid, with widely rounded apex ( Fig. 4G View FIGURE 4 ). Posterior margin straight, without setules, anterior margin regularly convex, with fringe of relatively short setules not reaching apex; on sides of keel there are 4 or 5 lateral groups of somewhat longer setules.

Valves large, subovoid, with numerous setae on ventral margin, longest in middle and posteriormost portions ( Fig. 4A, H View FIGURE 4 ). In middle of ventral margin bases of setae located slightly submarginally, rudimentary denticles (remainders of setules) between them ( Fig. 4I View FIGURE 4 ). Posteriorly to the last marginal seta, a row of submarginal setules starts on inner valve face of valve posterior margin, not organized into groups, in middle portion of posterior margin they located sparsely and far from the margin. “Setules” of marginal membrane very small.

Thorax relatively long. Abdomen short, distal edges of segments with transverse rows of setules, basal abdominal segment with a distinct abdominal projection ( Fig. 4A View FIGURE 4 ).

Postabdomen subovoid, robust, with maximum height in middle ( Fig. 5A, B View FIGURE 5 ). Ventral margin slightly convex, with rows of minute setules. Preanal margin shorter than anus, somewhat undulated, preanal and postanal angles well defined, while distal margin and dorso-distal angle of postabdomen not expressed. Postanal marginal denticles in about 18–20 clusters. On postanal margin, about 6 or 7 fascicles of stout lateral setae, 3–5 setae in each fascicle on distal portion, two marginalmost setae of each fascicle subequal in size, other setae much shorter ( Fig. 5C View FIGURE 5 ). About 15–18 fascicles of lateral setules on basal half of postanal and anal margin ( Fig. 5D View FIGURE 5 ). In atypical specimen some groups of lateral setae were absent and marginal denticles were stronger and protruding distally ( Fig. 5B View FIGURE 5 )

Postabdominal seta slightly longer than anal plus preanal margin; its distal segment markedly shorter than basal one.

Postabdominal claw robust, almost straight, as long as preanal plus anal portion of postabdomen. On lateral side, two successive series of slender setules along the dorsal margin. Basal spine about 1/3–1/2 of claw diameter at base.

Antenna I not reaching tip of rostrum, with 4 transverse rows of long setules on anterior face, stout setules at its end ( Fig. 5F–G View FIGURE 5 ). Sensory seta particularly long, slender, arising at distance of 1/5–1/6 of appendage length from distal end. Nine aesthetascs of slightly varied size, largest about half as long as appendage, reaching tip of rostrum.

Antenna II relatively short. Basal segment robust, with transverse series of fine, long setules, rudimentary distal spine and short setules at distal margin ( Fig. 5H View FIGURE 5 ). Antennal branches elongated, exopod slightly shorter than endopod, all segments cylindrical, 3 long and stout spine-like setules on first and second endopod segment. Antennal formula, setae 0–0–3/1–1–3, spines 1–0–1/0–0–1. On both exopod and endopod three long apical swimming setae of different size, basal and distal lateral setae unequal in size, both shorter than longest apical setae (fig. 5I). Spine on basal segment of exopod long, projecting beyond middle of apical segment. Apical spines of exopod and endopod of subequal length, obviously longer than apical segments.

Trunk limb I ( Fig. 6A View FIGURE 6 ), without accessory seta, ODL large, elongate, very slightly narrowing distally, with a long seta with distal segment unilaterally armed with short, sparce setules ( Fig. 6B–C View FIGURE 6 ). IDL with three clusters of short marginal setules, three medial clusters of short setules, and three bisegmented setae, shortest seta naked, two longer setae with long setules. Endite 3 with soft setae a–c of subequal size, and a stiff seta 1 of comparable size, armed with minute setules ( Fig. 6A View FIGURE 6 ). On endite 2 feathered setae d–f, seta d short, setae e– f subequal in length, a small, naked seta 2 with a sensillum near its base. Endite 1 with 2-segmented setae g–i, and a rudimentary seta 3. Fascicles of thin setules on inner face of limb, plus groups of longer, more robust setules on ventral margin. Two ejector hooks of unequal size. A maxillar process not found.

Trunk limb II with exopodite ovoid, small, without setae, but with a tuft of short setules ( Fig. 6D View FIGURE 6 ). Inner portion of limb with eight scrapers ( Fig. 6D View FIGURE 6 : 1–8). Distalmost scraper 1 without setules on basal segment, located on a distal lobe. Two projections posterior to scrapers 2–3, a sensillum near scraper 4. Portion of gnathobase bordering “endopodite” somewhat inflated, and densely setose. Distal armature of gnathobase with four elements ( Fig. 6E View FIGURE 6 ). Filter plate with seven setae, distalmost somewhat shorter than rest, with inflated basal segment and fully setulated, while others armed bilaterally.

Trunk limb III with sub-globular epipodite, exopodite trapezium-shaped with seven setae, distal seta 1 with long setules, seta 2 with distal segment armed by setules alternated in size, lateral setae 3–7 armed in similar manner, but setae 3–4 short ( Fig. 6F View FIGURE 6 ). Distal endite with three stiff setae, 1 and 2 with minute setules, 3 armed distally by longer setules ( Fig. 6G View FIGURE 6 ). Basal endite with stiff setae 4–7, armed with fine, short setules distally, small bottle-shaped sensillum near seta 4. On posterior limb face, four soft setae ( Fig. 6G View FIGURE 6 : a–d), seta a longest, all armed with long setules distally. Distal armature of gnathobase with four elements. Filter plate with eight bilaterally setulated setae, basalmost seta and distalmost seta shorter than rest.

Trunk limb IV with setulated pre-epipodite and globular epipodite ( Fig. 7A View FIGURE 7 ). Exopodite wide, subovoid, with six setae, seta 1 and 2 short, armed by short setules ( Fig. 7B View FIGURE 7 ), all other setae with similar armature of long, fine setules. Inner portion of limb IV with four marginal setae, seta 1 stout, with small, strong setules distally, 2–4 with inflated basal segments and slender, unilaterally setulated distal segments. On posterior limb face, three soft setae ( Fig. 7C View FIGURE 7 : a, c–d) and a curved sensillum (b). Distal armature of gnathobase with four elements. Filter plate with five setae, distalmost with inflated basal segment and fully setulated.

Trunk limb V with large setose pre-epipodite, and globular epipodite of similar size ( Fig. 7D View FIGURE 7 ). Exopodite large, with four setae. Inner limb portion an elongate, flat lobe, with setose inner margin. On inner face, two setulated setae of unequal length. Distal armature of gnathobase a setulated lobe, two setae in 'filter plate'.

Ephippium. Slightly pigmented in brown (except of egg locula which is almost un-pigmented), dorsal margin almost straight in posterior 5/6 of its length, where dorsal wall of carapace additionally chitinised ( Fig. 7F View FIGURE 7 ). All surface of ephippium covered by a fine striation as in parthenogenetic female, but within reticulation polygons there are rows of minute depressions along each line of the striation ( Fig. 7G View FIGURE 7 ), forming a pattern more similar with that on a beetle wing cover.

Adult male. Body low, elongated

Head relatively larger and rostrum longer than in female ( Fig. 8B View FIGURE 8 ). Anterior margin of labrum undulated, with relatively stort fringe of short setules; few lateral setules near fringe, 3–5 additional small groups of setules on sides of keel.

Valve with posterior margin ( Fig. 8D–E View FIGURE 8 ) as in female.

Postabdomen elongated, remarkably narrowing distally, with almost straight ventral margin; preanal margin short, slightly undulated; anal margin straight, postanal margin slightly convex; distal margin not defined ( Fig. 8G View FIGURE 8 ). Marginal denticles short, form clusters on postanal and anal regions, lateral setae long, form few groups of 2 or 3 members. Postabdominal claws straight. Penis almost straight, slightly thicker and shorter than claw, with pair of gonopores at tip, each opening on short, somewhat narrowing projection.

Antenna I proportions ( Fig. 8H–I View FIGURE 8 ), as in female, sensory seta as in female, male seta located distally, near numerous (12) aesthetascs.

Limb I with slender, U-shaped copulatory hook, bearing three ridges at its tip. ODL seta shorter than that in female, armed by fine setules. IDL with three setae of unequal size and two small hillocks. Portion of limb near the copulatory hook inflated and supplied with copulatory brush of rather short, strong setules. A copulatory brush seta short, with inflated basal part.

Size. Holotype 0.92 mm; Allotype 0.64 mm; juvenile and adult parthenogenetic females 0.53 – 0.99 mm, ephippial females 0.94 mm, adult males 0.59–0.64 mm.

Differential diagnosis. It is well-known that most of the Cladocera investigators avoid characters of the thoracic limbs and do not make specimen dissections. But the most characteristic trait of this taxon is its possession of seven setae on limb III exopodite, a character visible even without dissection of the animal. This trait is characteristic of only two species of the subgenus Leydigia (Neoleydigia) , namely L. propinqua and L. microps (Kotov, 2009) . L. korovchinskyi sp. nov. differs from both these taxa in: (1) absence of the “coarse” striation; (2) rounded apex of labral keel and (3) longer setae 3–4 of exopodite III. L. korovchinskyi sp. nov. also differs from L. propinqua in: (1) better expressed “fine” striation; (2) remarkably smaller distance between lateral head pore and midline of head shield; (3) more numerous lateral groups of setules on labral keel; (4) expressed setules between marginal setae; (5) setules in middle of posterior margin only somewhat longer than setules near posteriormost seta; (6) absence of a marginal membrane on posterior valve margin; (7) undulated preanal margin of postabdomen; (8) strongly narrowing postabdomen of male; (9) longer penis of male. L. korovchinskyi sp. nov. also differs from L. microps in: (1) larger compound eye; (2) several groups of setules on sides of labral keel located far from marginal fringe of setules; (3) absence of setules on posterior keel margin; (4) presence of both submarginal setules and “marginal membrane” at posterior valve margin; (5) absence of a distal margin of postabdomen; (6) longer preanal margin of postabdomen; (7) slightly convex, non concave, male postabdomen.

Distribution and ecology. This species has been found in only a single locality in the peneplain of central-western Spain (Extremadura). This Chaparral lagoon is a manmade shallow temporary pond for cattle drinking located among pastures and evergreen oaks (a landscape known locally as "dehesa"). Water was low mineralized (176 µS of water specific conductance) and clear, its brownish colour could be regarded as a sign of the water body dystrophy. The bottom was muddy, the submerged aquatic vegetation was scarce. Accompanying crustacean species were: the cladocerans Daphnia pulicaria Forbes, 1893 , Ceriodaphnia sp (undescribed species), Moina micrura Kurz, 1875 and Ilyocryptus agilis Kurz, 1878 ; the copepods Lovenula (Neolovenula) alluaudi (Guerne & Richard, 1890) and Megacyclops viridis Jurine, 1820 ; and the ostracods Potamocypris arcuata Sars, 1903 and Herpetocypris chevreuxi (Sars, 1896) . All these species are characteristic of temporary slightly mineralised waters without inorganic turbidity ( Alonso 1998).