Ephemeroporus malaysiaensis, Sinev, Artem Y. & Yusoff, Fatimah M., 2016

Sinev, Artem Y. & Yusoff, Fatimah M., 2016, A new species of genus Ephemeroporus Frey, 1982 (Cladocera: Anomopoda: Chydoridae) from Peninsular Malaysia, Zootaxa 4117 (3), pp. 399-410 : 400-405

Ephemeroporus malaysiaensis sp. nov.

(Figs. 1–3).

Etymology. Species named after the country where it was found

Type locality. Chini lake, Johor province, Malaysia, specimens collected during 19.10.2013 by A. Y. Sinev, F.M. Yusoff, P. Kuppan and M. S. Abu Bakar.

Type material. Holotype: parthenogenetic female from type location, ZMMU Ml-145.

Paratypes: 6 parthenogenetic females from type location, ZMMU Ml-146; 3 parthenogenetic females from Bukit Merah reservoir, Perak province, Malaysia, сoll. A. Y. Sinev and M. S. Abu Bakar. (AYS-ML-103).

Eight more parthenogenetic females from type location were studied by SEM or dissected for analysis of appendages.

FIGURE. 1. Ephemeroporus malaysiaensis sp. nov. from Tasik Chini lake, Malaysia. A, juvenile female. B–N, adult parthenogenetic females. B–C, lateral view. D, pigmented spot of anteroventral portion of valves (setae on valve not shown). E, ventral margin of valves (from flattened valve). F, central part of ventral margin of valves. G–H, postroventral corner of valves. I, rostrum in frontal view. K–L, labrum. L, antennule. M–N, antenna.

FIGURE. 2. Ephemeroporus malaysiaensis sp. nov. from Tasik Chini lake, Malaysia, parthenogenetic female. A, lateral view. B–C, fronto-lateral view. D, posteroventral corner of valves. E, head shield. F, head. G–H, postabdomen. I, postabdominal claws. Scale bars: 0.1 mm for A–C, 0.05 mm for E–G, 0.01 mm for D, H–I.

Description. Parthenogenetic female. Body of preserved specimens (Fig. 1A–C, 2A–C) from weakly yellow to colorless, relatively opaque, with five distinctive pigmented spots on each side of valve, located: (1) at anterior margin of valve below articulation point; (2) at 2/3 of anterior half of ventral margin; (3) at the middle of posterior half of ventral margin; (4) at posterodorsal angle of valves; (5) at dorsal portion of valves, after midline of the body. Examination of the spots revealed that each of them was formed by four to ten strongly pigmented hypodermic cells (Fig. 1D). Position of pigmented spots was the same in all studied specimens, but number of cells in each spot varied. In lateral view body rounded (Fig. 1A–C, 2A); height/length ratio about 0.9, maximum height at midline. Body only weakly laterally compressed (Fig. 2B–C). Dorsal outline evenly curved, ventral margin of valves with bulge at the middle, convex in anterior half and straight or weakly concave in posterior half.

Valves. Anterior corner broadly rounded, with a submarginal flange at inner side. Ventral margin (Fig. 1E) with about 6–7 moderately short setae in anterior portion, followed by 7–8 tooth-like serrated expansions of seta bases with extremely short setae at the end (Fig.1F); followed by 10–12 short setae increasing in length posteriorly; and followed by 20–25 long, setulated setae attached to inner side of valve, length of setae in the group decreasing posteriorly. Postero-ventral corner (Fig. 1G–H, 2D) with single long, slender, slightly sinuous denticle; length of denticle about 3 widths of denticle base. Valves covered by polygonal sculpture, more prominent along ventral margin (Fig. 2F).

Head with short rostrum, protruding downward. Length of rostrum about 1.5 length of antennule. Ocellus 2–3 times smaller than eye. Head shield moderately large, with maximum width after mandibular articulation; posterior margin of headshield broadly rounded (Fig. 2E,). Rostrum blunt, broadly rounded in frontal view (Fig. 1I). Headshield sculpture as polygons, similar to that of valve, but less pronounced. Head pores absent in adult specimens.

Labrum with large labral keel (Fig. 1J–K) projecting far below the tip of rostrum. Labral keel of moderate width, with elongated apex with rounded tip. Anterior margin of keel irregularly convex, with 3–4 very short spinules, posterior margin concave.

Postabdomen (Figs. 2H–G, 3A–B) short, rather narrow, narrowing distally; maximum height at preanal angle. Length about three heights. Ventral margin straight, with clear break bearing small spinule at 1/4 length from the end. Basis of claws bordered from distal margin by clear incision. Distal margin very short. Distal angle rounded. Dorsal margin irregularly concave in distal portion, with distal portion only slightly longer than the preanal portion. Postanal and anal portion of similar length. Preanal angle extremely well expressed, prominent, postanal angle not defined. Preanal margin weakly concave. Dorsal margin with two distinctive groups of narrow sharp denticles, followed by two groups of short setulae. Distal group consists of 5–6 shorter denticles, whose lengths strongly decrease basally. Basal group consists of 4–5 longer denticles, with distalmost members longer than in the previous group. Postanal part with 3–4 clusters of 1–3 short thick setulae; anal portion with broad lateral fascicles of very short setulae; clusters of irregularly spaced setulae at preanal angle. Postabdominal claw (Fig. 2I) short, curved, two times shorter than preanal portion of postabdomen, with two basal spines: distal spine about 0.3 length of the claw, proximal spine three times shorter. A pecten of spinulae on dorsal side of claw; long spinule on its tip, 1.5 times longer than shorter basal spine.

Antennule (Fig. 1L) of moderate size; length about 2.5 widths. Antennular seta thin, about 2/3 length of antennule, arising almost at the middle of antennule. All aestetascs terminal, about 2/3 length of antennule.

Antenna relatively short (Fig. 1M–N). Antennal formula: setae 0-0-3/0-1-3; spines 1-0-1/0-0-1. Branches relatively short; exopodite basal segment 1.5 times longer than two others, exopodite basal segment 2 times longer than two others. Basal segment of endopodite without seta. Seta arising from middle segment of endopodite of similar size with apical setae. Apical segments of both branches with three apical setae. All antennal spines very short.

Thoracic limbs: five pairs.

Limb I of moderate size (Fig. 3D–E). Epipodite oval, with curved projection 2.5 times longer than epipodite itself. ODL with only one seta, small ODL seta absent. IDL with three slender setae. IDL setae 1 and 2 of about 1/ 3 and 2/3 length of ODL seta, seta 3 only slightly shorter than ODL seta. Endite 3 with four setae, inner seta (1) much shorter than outer setae (a–c). Endite 2 with two long distally setulated setae (e–f) of similar length; a shorter seta near their base (d) and an inner seta (2) armed with long setulae on anterior face of limb. Endite 1 with three 2- segmented setae of similar size (g–i), setulated in distal part and a naked inner seta (3) on anterior face of limb, and a flat seta (j) pointed to the limb base. Ventral face of limb with three thick setulae in basal part, followed by four rows of thin long setulae. Two long ejector hooks, one slightly shorter than other; a cluster of 4–5 long setulae near their base.

Limb II subtriangular (Fig. 3F). Exopodite elongated of irregular shape, with long seta as long as scraping spine 3. Eight scraping spines with fine denticles; three basalmost spines (6–8) subequal in length, the others increasing in length distally. Basalmost spine with longer and thicker denticles than others. A small sensillum located between spines 3 and 4. Distal armature of gnathobase with four elements. Filter plate II with eight setae, the posteriormost member two times shorter than others.

Limb III (Fig. 3G–I). Epipodite oval, without finger-like projection. Exopodite subrectangular, with three lateral (1–3) and four terminal (4–7) setae. Seta 4 being longest; setae 6 and 7 about 3/4 and 2/3 length of seta 4, respectively; seta 1 and 5 about 1/2 length of seta 4; setae 2 and 3 short. Setae 1–5 plumose; setae 6–7 naked. Distal endite with three slender scraping setae (1–3) without denticles; length of setae 2 and 3 about 2/3 and 1/3 length of seta 1, respectively. Two small sensillae located between their bases. Six inner setae (a–f) of similar size, slightly increasing in size basally, all setae unilaterally armed with thick long setulae. Three pointed inner setae increasing in size basally; a small sensillum near the distalmost seta. Distal armature of gnathobase with four elements: the first one very large, elongated, bottle-shaped sensillum; second strongly geniculated seta; third and fourth-spines with fused bases. Filter plate III with eight setae.

Limb IV (Fig. 3J–K). Pre-epipodite setulated; epipodite oval, with projection longer than epipodite itself. Exopodite of characteristic form, almost semicircular, with seven setae; setae 1–4 long, of similar length; seta 5 and 7 about 2/3 length of seta 1; seta 6 about 3/4 length of seta 4. Setae 1–5 flat, plumose; seta 6 setulated unilaterally in basal part, seta 7 naked. Inner portion of limb IV with four outer setae (1–4) and small bottle-shaped sensillum. Scraping seta (1) of moderate thickness, distalmost flaming-torch setae (2) with thick basal part and short distal part, two others (3–4) with thin basal portion and long, slender distal part, all three armed with about 10 very long setulae; small sensillum located near base of seta 2. Four inner setae (a–d) slightly increasing in size basally. Gnathobase with one 2–segmented setae, a small hillock distally, and a sensillum. Filter plate IV with six setae.

Limb V (Fig. 3L). Pre-epipodite setulated; epipodite oval, with finger-like projection as long as epipodite itself. Exopodite moderately large, oval, with four plumose setae, their length evenly decreasing basally. Two small hillocks with long setulae located on basal side of exopodite near seta 4. Inner lobe long, narrow, with setulated inner margin. At inner face, two setae of similar length: outer seta densely setulated in distal part; inner one with long thick setules unilaterally in distal part. A row of long thin setulae located between inner seta and filter plate. Filter plate V with four setae.

Ephippial female and male unknown.

Size: minimum length of female in studied material was 0.28 mm (but specimen was obviously not a juvenile female of instar I), minimum size of ovigerous female was 0.36 mm, maximum length of female was 0.42 mm.

Differential diagnosis. Unique features of E. malaysiaensis sp. nov. are presence of pigmented spots on the valves (it is unique character for the whole family Chydoridae ) and postabdomen with 4–5 marginal denticles in anal group (in all other species of the genus, this group consists of 2–3 denticles only). Presence of pigmented spots should not be used as a main character for species identification, as pigment tends to gradually disappear in preserved specimens. Also, E. malaysiaensis sp. nov. differs from E. hybridus and E. acanthodes in presence of denticles on anterior margin of labrum; from E. pinthonicus , E. tridentatus and E. archboldi , in presence of single denticle on posteroventral corner of valves ( E. pinthonicus and E. tridentatus lack such denticles, and in E. archboldi number of denticles varies from 4 to 8); from E. quasimodo in the absence of dorsal keel; and from E. margalefi , E. ephiaphantoii and E. barroisi in greater size (in these species length of adult female is less than 0.3 mm).

Distribution and ecology. E. malaysiaensis sp. nov. is so far known from Malaysia only. It is a rare species, not recorded by Idris (1983); it also was not found during our survey of Sabah State, Borneo ( Sinev & Yusoff, 2015). During our sampling trips in peninsular Malaysia, we sampled over 80 water bodies, and E. malaysiaensis sp. nov. was encountered only in two large and shallow water bodies: in natural swampy Chini lake and in Bukit Merah reservoir. Located at 3o 22’– 3o 28’ N and 102o 51’– 102o 58’ E, Chini lake is a swampy flood plain lake connected to the longest river in Peninsular Malaysia (Pahang river) through a 4.8 km Chini stream. It is the second largest natural freshwater lake in Peninsular Malaysia with an area of 3.82 km 2, a mean depth of 2.5 m and a maximum depth of 6.0 m (Mushrifah, 2010). The lake is covered by extensive beds of emergent, floating leaved and submerged macrophytes, mainly Pandanus helicopus , Scirpus grossus , Lepironia articulata , Nelumbo nucifera and Cabomba furcata . Bukit Merah reservoir, located at 5o 01’ N and 100o 39’ E, is the oldest reservoir in Malaysia (constructed in 1906) with a surface area of 33.3 km 2, a mean depth of 2.5 m and a maximum depth of 5.3 m. ( Hidzrami, 2010).

In both locations, E. malaysiaensis sp. nov. was found among the abundant submerged macrophytes (mainly Cabomba furcata ) in the vicinity of Pandanus helicopus stands. Cabomba furcata is an introduced species that seems to successfully replace the natural floating leaved Nelumbo nucifera in Chini lake ( Zati et al. 2012). Wan- Juliana et al. (2010) reported that C. furcata covered 95.1% of the lake area in 2009. The Pandanus helicopus seems to be the most dominant emergent species, probably due to its tall erect stand that can grow up to 6 m, which allows it to grow in both shallow and deep waters.

FIGURE. 3. Ephemeroporus malaysiaensis sp. nov. from Tasik Chini lake, Malaysia, parthenogenetic female. A, postabdomen. B, dorsal margin of postabdomen. C–M, thoracic limbs. C, limb I. D, endites 2–3 of limb I (inner seta of endite 2 not shown). E, IDL and ODL of limb I. F, limb II. G, exopodite of limb III. H–I, inner portion of limb III. J, exopodite of limb IV. K, inner portion of limb IV. M, limb V.