Biapertura kendallensis
Creators: name: Sinev, Artem Y.
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Branchiopoda
Diplostraca
Chydoridae
Biapertura
Biapertura kendallensis

description: Biapertura kendallensis (Henry, 1919).
Henry 1919: 474–475, Pl. XII, Fig. 9–10 (Alona), 475–476, Fig. 11–12 (Alona longirostris); Henry1922: 41, pl. VIII, Fig. 7 (Alona); Smirnov 1971: 474, Fig. 591–592; Smirnov & Timms 1983: 57, Fig. 66; Sinev 1997: 55, Fig. 4G (Alona).
Type locality. Kendall, New South Wales, Australia.
Type material. Holotype at Australian Museum, access number P4331.
Material studied here. Over 50 parthenogenetic females, 21 ephippial females, 14 adult males, 1 juvenile male of instar I, 5 juvenile males of instar II from roadside pond near road to Ryan’s II Billabong, Bonegilla, 10 km east of Wodonga, Victoria, Australia, 36º06’40.4”S, 146º58’31.7”E, 6.12.1986, coll. D.G. Frey, DGF–8926; over 20 parthenogenetic females from Jibbon Lagoon, Royal National Park, New South Wales, Australia, 34°05’12’’S, 151°09’53’’E, 12.11.2011, coll. T. Kobayashi; 6 parthenogenetic females, several exuvia Ellis F.D, 6 km W Stratford, New South Wales Australia, 32°06’30.315’’S, 151°52’57.291’’E, 19.03.1976, coll. B. V. Timms.
Material studied earlier. See Sinev (1997) for the list of material from Australia. Morphology of this species was never completely studied before, so a full description is provided. Male and ephippial female of B. kendallensis are described for the first time.
Description. Parthenogenetic female. In lateral view, body oval, low in juvenile females (Fig. 6 A–B, 7A); oval, of moderate height in adults (Fig. 6C, 7 B–D); moderately compressed laterally. Maximum height at the middle of the body. In adults height/length ratio about 0.6.
Carapace. Dorsal margin convex; postero-dorsal and postero-ventral angles broadly rounded. Posterior margin convex. Antero-ventral angle rounded. Ventral margin (Fig. 6D) weakly convex to straight, with 75–90 setae. About 25 anteriormost setae very long (Fig. 6E), next 15 seta short, posterior 40–50 setae of moderate length (Fig. 6F), decreasing in length posteriorly. Postero-dorsal angle (Fig. 6 G–H) with 5–6 groups of long thin setulae, with 4–7 setulae in each; length and thickness of setulae in groups increasing posteriorly. A row of about 100 setulae of variable length along posterior margin on inner side of carapace, these setulae not organized into groups. Carapace ornamentation as weakly developed longitudinal lines and dense longitudinal striae between them.
Head relatively small, low triangular-rounded in lateral view. In lateral view rostrum relatively narrow, protruding downwards. Ocellus of moderate size; in adults eye of similar size to ocellus. Distance from tip of rostrum to ocellus 1.5 times greater than that between ocellus and eye. Head shield (Fig. 6 I–J) with maximum width behind mandibular articulation, covered by fine striae as on valves. Rostrum short and rounded. Posterior margin of head shield as prominent, acute distal angle. Two major head pores (Fig. 6K, 7F, 8F) of same size, with a narrow connection between them. PP about 2.5 IP in adults. Lateral head pores located in small depressions about 1 IP distance from midline, at level before anterior major head pore. Striae absent around head pores. Dorsal pore of typical for genus shape, not studied in detail.
Labrum (Fig. 9A,B) of moderate size. Labral keel moderately wide, with a blunt apex. Anterior margin of keel convex, posterior margin weakly convex to straight, with two clusters of short setulae.
Thorax two times longer than abdomen. Dorsal surface of abdominal segments not saddle-shaped. Abdominal joint not developed.
Postabdomen (Fig. 7G, 9 C–D) large, subrectangular, moderately high, with parallel margins, weakly narrowing at the end. Length about 2.5 height. Ventral margin straight. Basis of claws bordered from distal margin by clear incision. Distal margin almost straight; distal angle rounded, sometimes weakly protruding. Dorsal margin weakly convex to straight in postanal portion and weakly concave in anal one; with distal part about 2.5 times longer than preanal one; with postanal portion 2.5–2.8 times longer than anal one. Preanal angle well expressed, postanal angle not defined. Preanal margin almost straight. Postanal margin (Fig. 7H, 9E) with 12–14 well-developed, sharp composite denticles, each with 1–7 (usually 3–5) spinulae along anterior margin; size of denticles increasing distally. Length of longest denticles about 1.5 the width of base of postabdominal claw, more than 3 times exceeding the width of the denticle base. Postanal portion with 10–12 broad lateral fascicles; posteriormost setula of each fascicle longest, thicker than others, slightly shorter than neighboring marginal denticles. Anal portion with several smaller fascicles, spaced irregularly. Postabdominal claw (Fig. 7I, 9F) of moderate length, slightly longer than preanal portion of postabdomen. Basal spine long and slender, about 0.3–0.35 length of the claw. A row of 7–10 long setules between basal spine and the base of postabdomen.
Antennule (Fig. 9G) of moderate size, length about 3x width, with a cluster of 3–4 long setulae about one third the length of antennule at anterior face, and 2–3 transverse rows of very short setulae below it. Antennular seta thin, more than 1/2 length of antennule, arising terminally. Nine terminal aesthetascs, two of them long and thin, little shorter than antennule itself; all others much shorter, about 1/2–1/3 the length of antennule.
Antenna relatively short (Fig. 8 A–B, 9H). Antennal formula, setae 0-0-3/1-1-3, spines 1-0-1/0-0-1. Basipodite robust, with very short seta between branches; branches relatively short; all segments cylindrical, slender; middle segment in each branch shorter than others, 1.5 times shorter than basal segment. Seta arising from basal segment of endopodite thin, reaching above the end of endopodite. Seta arising from middle segment of endopodite, of similar size to apical setae. Two shortest apical setae of both exopodite and endopodite with a very long spinule at the point of articulation. Spine on basal segment of exopodite longer than middle segment. Spines on apical segments much shorter than apical segments.
Limb I of moderate size (Fig. 10 A–B). Epipodite oval, with very short projection. Accessory seta long, only slightly shorter than ODL seta, with long setulae in distal part. ODL with one seta. IDL with three setae and several clusters of hard setules. IDL seta 1 large and broad, claw-like, strongly curved, slightly longer than seta 2; IDL setae 2 and 3 with thin setulae in distal part, seta 3 slightly shorter than ODL seta, seta 2 about 2/3 the length of seta 3. Endite 3 with four setae subequal in length. Endite 2 (Fig. 10A) with two long distally setulated setae (e–f), a shorter seta near their base and a naked inner seta and small sensillum on anterior face of limb; seta e long, two times longer than seta f, about 2/3 lengths of limb itself. Endite 1 with two 2-segmented setae (g–h), both setulated in distal part; a flat plumose seta pointed the limb base, and a naked inner seta 3 two times longer than inner seta 2. Seven–eight rows of thin long setulae on ventral face of limb. Two ejector hooks, one slightly shorter than other. Maxillar process elongated, with short setulated seta in distal part.
Limb II subtriangular (Fig. 10D). Exopodite elongated, of irregular shape, with slender seta as long as exopodite itself and cluster of very long setulae in distal part. Eight scraping spines, three basalmost spines subequal in length, others increasing in length distally. Size of denticles on basal part of spines decreasing from basal to distal spines. Distal armature of gnathobase with four elements. Filter plate II with seven setae, the posteriormost member shorter than others.
Limb III (Fig. 10 E–G). Epipodite oval, without projection. Exopodite of irregular shape, with seven setae. Seta 3 being longest, setae 6 about 1/2 length of seta 3, seta 7 two times shorter than seta 6, other setae very short. Setae 1–5 plumose, seta 6 with three rows of hard setulae in distal part, seta 7 with thin setulae in distal part. Distal endite with 3 setae, two distalmost members (1–2) scraping, slender, sharp, with denticles in distal part; short bottle-shaped sensillum located between their bases, seta 2 shorter than seta 1; seta 3 flattened, as long as seta 2, bilaterally armed with long setulae. Basal endite with 4 plumose setae increasing in size basally. Four pointed soft setae increasing in size basally, a small bottle-shaped sensillum near the distalmost seta. Distal armature of gnathobase with four elements; the first one elongated, narrowing distally sensillum, second strongly geniculated seta, third and fourthspines. Filter plate III with seven setae.
Limb IV (Fig. 10 H–I). Pre-epipodite setulated; epipodite oval, with finger-like projection shorter than exopodite itself. Exopodite subquadrangular, with six setae. Seta 1 and 2 being longest, equal in length; seta 3 slightly shorter, bending toward inner portion of limb; seta 4 about 2/3 length of seta 1, bending toward inner portion of limb; setae 5–6 subequal in length, slightly shorter than seta 4. Setae 1–4 plumose, setae 5–6 with short setulae. Inner portion of limb IV with four setae and bottle-shaped sensillum. Scraping seta slender, three flaming-torch setae decreasing in size basally, with 7–9 long setulae each. Small sensillum between the base of middle and basal flaming-torch setae. Three soft setae slightly increasing in size basally. Gnathobase with one long 2-segmented setae, a small hillock distally and a sensillum. Filter plate IV with five setae.
Limb V (Fig. 10 J–K). Pre-epipodite setulated; epipodite oval, with finger-like projection as long as epipodite itself. Exopodite divided into two lobes, with four plumose setae: setae 1–3 long, subequal in length; seta 4 three times shorter. Inner lobe broad, rounded with setulated inner margin. At inner face, two setae densely setulated in distal part, one of them very long, slightly longer than exopodite setae; the other two times shorter. Filter plate V with three setae, two broad-based sensilla-like structures between inner face setae and filter plate.
Limb VI (Fig. 10L) as elongated lobe with setulated margin.
Ephippial female (Fig. 6L, 8C,D). Body slightly higher than in parthenogenetic female, dorsal margin almost straight in posterior half of the body, posterior margin less convex than in parthenogenetic females. Ephippium (Fig. 8E) with well-developed egg locules, with weakly expressed polygonal sculpture, covered by same longitudinal striae as rest of valves, yellow-brown in preserved specimens.
Male. Juvenile males of instar I and II similar in shape to respective female juvenile instars. In adult male, body (Fig 6O) low oval, with maximum height at the middle, height/length ratio about 0.54.
Postabdomen in juvenile males (Fig. 9 I–J) similar to that of female; gonopores located laterally near ventral margin, at 1/3 distance from the base in instar I, at 2/3 distance from the base in instar II. In adult male, postabdomen (Fig. 9M) of moderate size, with parallel margins. Length about 3 heights. Ventral margin straight in distal half. Postabdominal claw situated on small protrusion in ventral portion of convex distal margin. The sperm ducts open above the protrusion; posteroventral and posterodorsal angles rounded. Dorsal margin almost straight in postanal portion and weakly concave in anal one. Preanal angle weakly defined; postanal angle not defined. Preanal margin almost straight. Distal portion of postabdomen two times longer than preanal one; postanal portion two times longer than anal one. Clusters of thin setulae in place of female marginal denticles on postanal margin (Fig. 9N), no spinelike denticles near the postanal angle. Lateral fascicles of setulae as in female. Postabdominal claw (Fig. 9O) weakly curved, shorter than in female, as long as preanal margin. Basal spine about 0.25–0.3 length of claw.
Antennule in juvenile male of instar I same as in female; in juvenile male of instar II (Fig. 9L) slightly more massive than in female, with 9 terminal aesthetascs, with anlage of male seta about 1/6 length of antenna. In adult (Fig. 9P) broader than in female, with 12 long terminal aesthetascs, two longest almost as long as antennule itself, others about 2/3 length of antennule. Male seta subterminal, about 1/3 length of antennule.
Thoracic limb I in juvenile male of instar I with short anlage of copulatory hook (Fig. 10M); IDL and endite 3 same as in female. In juvenile male of instar II, limb with curved copulatory hook curved, about 2/3 length of limb itself, with anlage of copulatory brush seta and smaller triangular seta, absent in adult male, about it (Fig. 10N). IDL with anlage of male seta; IDL setae 1–3 similar to these of female. Ventral face of the limb under the copulatory brush seta with row of about 15 stiff setulae of variable length. Inner seta (1) of endite 3 same as in female. In adult male, limb (Fig. 10 O–Q) with U-shaped copulatory hook, half as long as limb itself. The IDL has four setae namely IDL seta 1 not hook-like, but still well-developed, as long as male seta; IDL setae 2 and 3 much thinner and two times shorter than in female; the male seta curved, as long as seta 1. Copulatory brush seta about 2/3 length of IDL seta 2. Ventral face of the limb under the copulatory brush with row of 20 stiff setulae of moderate length; outer face of endite 3 with row of about 15 shorter setulae, with no gap between these two rows (Fig. 10P). Inner seta (1) of endite 3 thinner than in female, with long setulae distally.
Size. In females of first juvenile instar, length 0.50–0.56 mm, height 0.26–0.30 mm; in females of second juvenile instar, length was 0.59–0.65 mm, height 0.33–0.35 mm. In adult females length 0.70–0.94 mm, height 0.45–0.52 mm. In single studied male of first juvenile instar, length 0.55 mm, height 0.29 mm; in males of second juvenile instar, length was 0.59–0.62 mm, height 0.31–0.33 mm. Length of adult male was 0.64–0.67 mm, height 0.32–0.34 mm.
Differential diagnosis. B. kendallensis differs from B. affinis, B. sibirica and B. ossiani in greater IP/PP ratio (2.5–3 instead of 1.5–2 in adult); from B. martensi and B. elliptica in female postabdomen with parallel margins; from B. lepida in claw-like IDL seta 1. B. kendallensis also clearly differs from B. affinis and B. sibirica in shape of male postbdomen.
Distribution. Australia and Tasmania (Smirnov & Timms 1983; Shiel & Dickson 1995).
description: Published as part of Sinev, Artem Y., 2020, Re-evaluation of the genus Biapertura Smirnov, 1971 (Cladocera: Anomopoda Chydoridae), pp. 301-335 in Zootaxa 4885 (3) on pages 311-318, DOI: 10.11646/zootaxa.4885.3.1, http://zenodo.org/record/4296625