Disparalona (Leptorhynchus) hamata

Disparalona (L.) hamata (Birge, 1879) (Figs. 1–4) Material examined. 15 parthenogenetic females, 8 ephippial females, 8 males from a sole sample AAK 2008-147. Description of bromeliad population. Parthenogenetic female. General. In lateral view, body oval (body height/ length ratio about 0.58 in all investigated females), maximum height at the middle of body (Fig. 1A). Body compressed laterally, lacking dorsal keel and lateral processes on valves (Figs. 1A, C–D, 2A). Dorsal margin broadly curved, depression between head and rest of body absent (Fig. 1A). Posterodorsal and posteroventral angles rounded, posterior margin convex (Fig. 1A). Surface of valves and head covered by numerous short sometimes wavy lines (Figs. 2 A–C). Anterior and posterior portions of valves with long prominent parallel lines (Figs. 1A, C–D, 2A). Head small, triangular, with relatively long rostrum (Figs. 1A, 2 A–B). Compound eye larger than ocellus, distance between centre of eye and ocellus almost in two times shorter than distance between centre of ocellus and tip of rostrum (Fig. 1A). Number and position of head pores are typical for subfamily Chydorinae: two minute pores located between two major head pores asymmetrically to midline of body (closer to anterior major head pore than to posterior one) (Figs. 1C, E). Labrum large. Labral keel short, triangular (Figs. 1A, F). Its anterior margin is almost straight, distal angle is acute. Valve broadly ovoid (Figs. 1A, G, 2A), with a row of numerous fine setulae on posterior margin (Fig. 1H) and long setae on ventral (Fig. 1I) and anteroventral margins. Thorax relatively long, abdomen short (Fig. 1A). Postabdomen subrectangular (postabdomen length/height ratio about 2.8) (Figs. 1A, J, 2A, D). Ventral margin almost straight, preanal and anal margins equal in length, postanal margin two times longer than preanal and anal margins and parallel to ventral margin (Figs. 1A, J, 2A, D). Preanal and postanal angles expressed. Distal angle of postabdomen straight (Figs. 1A, J, 2A, D–E). Each side of postanal portion with a row of thin and long postanal composite teeth, increasing in size distally. Lateral surfaces of postanal and anal portion covered by bunches of fine setulae. Transverse rows of fine setulae located on ventral margin of postabdomen. Postabdominal claw long (subequal in length to anal margin), slightly curved (Figs. 1J, 2A, D–F). Dorsal edge of claw armed with a row of fine spinulae decreasing in size distally. Two basal spines located at claw base (Fig. 1J). Distal basal spine longer than proximal one. Postabdominal seta relatively long, almost two times longer than preanal margin (Fig. 1A). Antenna I cylindrical, not reaching tip of rostrum (Figs. 1K, 2B, G). Antennular sensory seta slender, subequal in length to antennular body. Nine aesthetascs, subequal in size. Antenna II relatively short (Fig. 1L). Antennal formula: setae 0–0–3/1–1–3, spines 1–0–1/0–0–1. Basal segment covered by transverse rows of setulae, with a small spine between exopod and endopod branches. Antennal branches subequal in length, all their segments cylindrical, covered by transverse rows of fine setulae. Apical setae long. Seta arising from proximal endopod segment thin and relatively long (subequal in length to endopod branch with apical spine). Seta of the middle endopod segment long, reaching tips of apical setae. Spine of proximal exopod segment short (reach 1/4 portion of the middle exopod segment length). Spines of both apical segments long. Endopod apical spine longer than exopod one. Thoracic limbs: five pairs (Figs. 3 A–G). Limb I large (Fig. 3A). ODL conical, with two setae: long seta and short one. IDL with three setae, two of them slender, third seta represented by thick, curved hook. In lateral view, limb corm almost rectangular. Endite 4 with three soft posterior setae (a–c) subequal in size and a stiff anterior seta 1. Endite 3 with three posterior setae (a short posterior seta “d”, especially long seta “e”, shorter seta “f”) and a stiff anterior seta 2. Endite 2 with three posterior long setae (g–i), short seta “j” (not shown on the figure), and anterior stiff seta 3. Rows of long and robust setulae located between seta 2 and seta 3. Endite 1 with a short seta not shown. Two slender long ejector hooks unequal in length. Limb II triangular (Fig. 3B). Exopodite ovoid, with a long seta. Inner portions of limb with eight scrapers. A series of small projections posteriorly to distal setae, and a long sensillum between scraper 3 and 4. Distal side of gnathobase (= endite 1 sensu Kotov (2013)) with a row of fine long setulae. Distal armature of gnathobase with four elements, one of them represented by minute sensillum. Filter plates with eight setae. Limb III with ovoid epipodite (Fig. 3C). Exopodite almost rectangular, with three lateral seta and four distal setae differing in size and armature. Distal endite (in terms of Kotov (2013)) with three anterior setae (Fig. 3C: 1, 2, 3). Proximal endite with four small anterior setae. Six (a–f) soft setae on posterior surface of limb setae (Fig. 3C). Distal armature of gnathobase with four elements: thick bottle-shaped sensillum and three small setae (Fig. 3D). Filter plate with eight setae. Limb IV bears seven setae of different size and armature (Fig. 3E). Inner distal portion of limb IV with four setae (1–4) (Fig. 3F). Four soft setae (a–d) located on posterior surface of limb IV (Fig. 3E). Distal armature of gnathobase with four elements: three small sensillae and a long bisegmented seta (Fig. 3F). Filter plate with six setae. Limb V with ovoid preepipodite and epipodite (Fig. 3G). Exopodite large, oval, with a single short distal seta and three long lateral setae. Inner limb portion represented by oval flat lobe with setulated margin. Near this lobe located two setae (1–2). Filter plate with four long setae. Ephippial female. Shape of body of ephippial female (Fig. 1B) almost identical to parthenogenetic female (Fig. 1A). Ephippium dark brownish, not bordered via demarcation line from the rest of body. A single large egg in the ephippium. Adult male. General. Body oval, elongated (height/length ratio about 0.50) (Figs. 4 A–B). Maximum height almost at the middle of body. Dorsal margin convex, posterodorsal angle expressed, posteroventral angle broadly rounded. Ventral margin straight (Figs. 4 A–B). Head elongated (Figs. 4 A–B), similar with females. Labrum with triangular labral keel (Fig. 4C). Postabdomen long, typically narrowing distally (Figs. 4D, G). Postabdomen length/height ratio about 3.7 (Fig. 4G). Ventral and preanal margins straight. Anal and postanal margins slightly concave. Postanal two times longer than preanal and anal margins. Postanal and preanal angles smooth. Distal angle rounded. Postanal margin armed by bunches of setulae. Postanal and anal lateral surfaces covered by bunches of fine setulae. Gonopores open near bases of claws (Fig. 4G). Postabdominal claw almost straight, with two basal spines unequal in length (Figs. 4 D–F) or only with single basal spine (Figs. 4 G–H). In the last case it seems that the proximalmost spine is reduced. Postabdominal seta long (Fig. 4A). Antenna I cylindrical, with nine aesthetascs (Fig. 4I). Male seta thick, located near sensory seta. Antenna II similar to females (Fig. 4J), antennal formula: setae 0–0–3/1–1–3, spines 1–0–1/0–0–1. Limb I with prominent copulatory U-shaped hook (Fig. 4K). Copulatory brush seta short, slender. IDL with four setae. Among them two setae slender, one seta represented by massive hook. Their armature similar with parthenogenetic females. Male seta slender, curved in distal portion, about 2/3 length of seta 1 (Fig. 4K). Size. Maximum length of adult parthenogenetic females up to 0.56 mm. Maximum length of ephippial females up to 0.53 mm. Maximum length of adult males up to 0.44 mm. Variability. In T. aguascalentensis we found males with two basal spines on postabdominal claw and males with single basal spine. Therefore we re-examined material with males from Canada (a sample with accession number AAK M-1192, see details in Neretina et al. (2018)) (Fig. 5A). There apart from males with two basal spines on postabdominal claw (Figs. 5 B–D), we found males only with single basal spine as well (Figs. 5 E–F). Thus the number of basal spines on claw of male postabdomen is variable, even within the same population. Also, in males from water accumulated in bromeliads some minor variability concerns proportions of rostrum (Fig. 4B) and shape of distalmost portion of postabdomen (Fig. 4F). But these deviations were observed only occasionally.

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