Alpinalona fornshelli Sinev 2020, sp. nov.
Creators: name: Sinev, Artem Y.
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Branchiopoda
Diplostraca
Chydoridae
Alpinalona
Alpinalona fornshelli

description: Alpinalona fornshelli sp. nov.
(figs 1–3)
Etymology. The species is named after my friend and colleague, Dr. John Fornshell. His assistance and hospitality was crucial for my work during my visits to the National Museum of Natural History, USA.
Type locality. Black Lake at east side of Highway 1226, 3.1 miles north from junction with Highway 84, Natchitoches Parish, Louisiana, USA, 20.03.1978, coll. by D.G. Frey, original sample DGF 4657F.
Type material. Holotype. Parthenogenetic female from the type locality deposited in the National Museum of Natural History, Washington DC, USA (accession number USNM 1558272).
Allotype. Adult male from the type locality deposited in the National Museum of Natural History, Washington DC, USA (accession number USNM 1558273).
Paratypes. 5 parthenogenetic females, 5 ephippial females, deposited in the National Museum of Natural History, Washington DC, USA (accession number USNM 1558274).
Other material studied. Several poorly preserved specimens and exuviae from the type location, including one juvenile male of instar II and one adult male, were dissected for the analysis of appendages and did not kept afterwards.
Description. Parthenogenetic female. In lateral view body regularly ovoid (Fig. 1 A–B), moderately high; maximum height at middle of body; height/length ratio 0.60–0.62 in adults; juvenile females with lower body than adult females. Body moderately compressed laterally. Dorsal margin uniformly curved; postero-dorsal and posteroventral angles broadly rounded; posterior margin weakly curved; ventral margin almost straight; antero-ventral angle rounded.
Valves with well-developed linear sculpture in dorsal and posterior portions. Ventral margin of valves (Fig. 1C) with 50–60 setae, about 15 anterior setae long, next 10 setae very short, followed by setae of moderate length, evenly decreasing in length posteriorly. Postero-ventral angle (Fig. 1 D–E) bearing about 40 short setulae unequal of length, organized into 5–6 groups. A row of about 200 setulae unequal of length, with very long setulae separated by shorter ones, along the posterior margin on inner side of valve.
Head triangle-round in lateral view. In lateral view, rostrum short, pointed downward. Ocellus and eye of similar size.
Head shield with maximum width behind the mandibular articulation. Rostrum short, broadly rounded. Posterior part with broadly rounded distal angle. Two main head pores of similar size with narrow connection between them (Fig. 1F); PP = 0.8–1.2 IP in adults. Lateral head pores minute, located at about 0.7 IP distance from midline, at level between main head pores.
Labrum (Fig. 2 A–B) of moderate size; labral keel moderately wide; height-to-width ratio of about 1.5, with rounded or blunt apex; anterior margin of keel convex, posterior margin without setulae.
Thorax two times longer than abdomen. Middle abdominal segment not saddle-shaped, no abdominal joint.
Postabdomen (Fig. 2 C–D) moderately short and broad, subrectangular; maximum height before the middle of postanal margin. Length of about 2.3–2.4 height. Ventral margin straight or convex. Distal margin conveх. Distal angle broadly rounded. Dorsal margin convex in postanal part and concave in anal part, with distal part about 1.7–1.8 times longer than preanal one; postanal portion slightly longer than anal one. Preanal angle well-defined; postanal angle not defined. Preanal margin almost straight. 4–5 very short composite postanal marginal denticles, each denticle with 2–5 spinules, followed by 7–8 groups of very short elementary denticles and setulae; anteriormost group located at significant distance from preanal angle. 12–14 well-developed lateral fascicles of setulae; posteriormost setae of postanal fascicles very thick and long, about 1.5–2 width of postabdominal claw base. Distal postanal fascicles narrow, consisting of 4–6 setulae only, other fascicles of moderate width. Postabdominal claw (Fig. 2E) weakly curved, slender, as long as preanal margin of postabdomen. Several distal elements in basal pecten of claw consisting in thick spinules; length of distalmost spinule same as the width of the claw at its beginning. Basal spine thin, about 0.3 length of claw itself. Four-five small spines located near the base of claw before the basal spine.
Antennule (Fig. 2F) long and slender, length about 3 width, with three-four clusters of setulae on inner face. Antennular sensory seta slender, two times shorter than antennule, arising at 2/3 distance from the base. Nine aesthetascs of similar size, about 2/3 length of antennule, projecting beyond anterior margin of the head shield.
Antenna (Fig. 2G) with antennal formula setae 0-0-3/1-1-3, spines 1-0-1/0-0-1. Basal segment massive; branches of moderate length; basalmost segments of both branches 1.5 times longer than distal segments. Seta arising from basal segment of endopodite thin, reaching after the tip of distal segment. Seta arising from middle segment of endopodite of similar size with smaller apical setae. Apical setae of similar size and thickness. Spine on basal segment of exopodite slightly shorter than middle segment. Apical spines longer than apical segments.
Thoracic limbs: five pairs.
Limb I (Fig. 3 A–B) of moderate size. Epipodite oval, with a finger-like projection longer than epipodite itself. Accessory seta short. ODL seta with very short setulae in distal part. IDL with 3 setae; seta 1 sharp, about 1/4 length of ODL seta; setae 2 and 3 of slender, armed with thin setulae in distal part; seta 3 as long as ODL seta; seta 2 slightly shorter than ODL seta. Endite 3 with four setae subequal in length. On endite 2 there are three outer setae of different length and inner naked seta (2) on anterior face. Seta “e” much longer than seta “f”, almost as long as limb itself. Endite 1 with two 2-segmented setae (“g–h”), a flat, geniculated seta (“i”) shifted to the limb base, and inner naked seta (3) on anterior face. Five–six rows of long setulae on ventral face of limb. Two slender ejector hooks, one of them slightly longer than other.
Limb II triangle-rounded (Fig. 3 C–D). Exopodite elongated, of irregular shape, with short seta. Inner portion of limb with eight scraping spines increasing progressively in length distally, armed with denticles of similar size. No inner seta near base of scraper 1. Distal armature of gnathobase with four elements. Filter plate II with seven setae, two posteriormost considerably shorter than others.
Limb III. (Fig. 3 E–G). Epipodite oval. Exopodite subquadrangular, with seven setae. Seta 3 longest; setae 6 about 1/3 length of seta 3; other setae short, more than two times shorter than seta 6. Setae 1–5 plumose; seta 6 armed bilaterally with hard setulae. Distal endite with 3 setae and two small sensillae located between their base; two distalmost setae (1–2) scraping, slender, sharp, with denticles in distal part; basalmost seta (3) shorter, flattened, geniculated, bilaterally provided with setulae. Basal endite with 4 setae (a–d). Four slender sharp inner setae; a small sensillum near the basalmost of them. Gnathobase with sensillum, small spine and a geniculated seta. Filter plate III with seven setae.
Limb IV (Fig. 3 H–I). Pre-epipodite setulated. Epipodite with finger-like projection as long as epipodite itself. Exopodite subquadrangular, with six plumose setae. Seta 3 being longest; setae 1–2 slightly shorter than seta 3; setae 4–6 about 1/2 length of seta 3. Inner portion of limb IV with four setae and small bottle-shaped sensillum. Scraping seta (1) slender, sharp, flaming-torch setae (2–4) of similar shape, decreasing in size basally; a small sensillum located between bases of setae 3 and 4. Three inner setae increasing in size basally. Gnathobase with two-segmented setae, sensillum and a small hillock distally. Filter plate IV with five setae.
Limb V (Fig. 3J). Preepipodite setulated; epipodite oval, with finger-like projection as long as epipodite itself. Exopodite of moderate size, separated into two lobes, with four plumose setae evenly decreasing in length basally; seta 4 short three times shorter than seta 1. Inner lobe moderately broad, widening distally. At inner face, two setae; distal seta 1.5 times longer than basal seta; large triangular hillock and a small sensillum-like structure are located near its base. Filter plate V absent.
Ephippial female. Body (Fig. 1G) similar in shape to parthenogenetic females; ephippium in preserved specimens weakly yellow-brown; sculpture of ephippium as longitudinal lines, same as on the rest of the valves.
Male. Body of both juvenile male of instar II (Fig. 1H) and adult male (Fig. 1I) slightly lower than in female; height/length ratio about 0.6. Both eye and ocellus of size as in female, eye larger than ocellus.
Postabdomen in juvenile male of instar II (Fig. 2H) similar to that of female. Gonopores located at ventral margin at 2/3 length from the base. Armament of postabdomen and postabdominal claws same as in female. In adult male (Fig. 2J), postabdomen more narrow than in female, with parallel margins in anal portion, narrowing distally in postanal portion, with maximum height at postanal angle; length about 2.7–2.8 maximum heights. Gonopores located at the end of postabdomen above the base of postabdominal claws. Ventral margin straight. Distal margin convex; distal angle broadly rounded. Preanal angle well-defined; postanal angle not defined. Distal part of postabdomen two times longer than preanal; anal and postanal portions of similar length. Wide clusters of short setulae in place of marginal denticles; setulae in 3–4 distalmost clusters longer than in others. Lateral fascicles of setulae same as in female. Postabdominal claw (Fig. 2K) short, shorter than preanal portion of postabdomen. Several distal elements in basal pecten of claw being thick spinules; length of distalmost spinule slightly less than the width of the claw at the spot. Basal spine straight, about 0.25 of claw length.
Antennule (Fig. 2L) short and moderately broad, length about two widths. Twelve terminal aesthetascs, most of them slightly shorter than antennule itself. Male seta arising at 1/3 length from tip, and about 2/5 of antennule length.
Thoracic limb I in juvenile male of instar II (Fig. 3 K–L) with curved copulatory hook, about 2/3 length of limb itself, and massive anlage of copulatory brush seta. IDL with anlage of male seta; IDL seta 1 absent; setae 2–3 similar to those of female. Ventral face of the limb under the copulatory brush seta with row of about 5 stiff setulae of moderate length. Inner seta (1) of endite 3 similar to that of female. In adult male, limb I (Figs. 3 M–N) more massive than in female; copulatory hook U-shaped; its distal portion 1.5 times longer than basal one. A row of about 20 thick, moderately long setulae located under copulatory brush on ventral face of limb. Inner seta (1) of endite 3 thinner and much longer than in female, 1.5 times longer than other setae of endite 3, armed with thin setules. IDL without seta 1; setae 2 and 3 of similar length, much thinner and shorter than in female; male seta large, hook-like, almost as long as seta 3.
Size. Adult females length 0.51–0.66 mm, height 0.31–0.4 mm. Adult males length 0.42–0.44 mm, height 0.26–0.27 mm. Length of single studied juvenile male of instar II was 0.4 mm, height 0.25 mm.
Differential diagnosis. Alpinalona fornshelli sp. nov. differs from other species of the genus in having: (1) over 35 setulae on posteroventral angle of the valves, organized into 5–6 groups; (2) a long basal spine of female postabdominal claw (about 0.3 claw length); and (3) thick long distalmost spines in basal pecten of postabdominal claw of both male and female. Both A. cajasi (see Alonso & Sinev, 2017) and A. manueli (see Fig. 1J, 2 M–N) have less than 25 setulae on the posterior-ventral angle of valves, organized into 2–3 groups; basal spine of about 0.2 postabdominal claw length; and basal pecten of claw consisting of thin setules, length of basalmost ones less than half width of the claw at the spot. A. fornshelli sp. nov. also clearly differs from A. cajasi in broadly rounded, not prominent, posterodorsal angle of valves and IP/PP ratio about 1 (PP/IP is about 2 in the latter species). Other differences between species are summarized in Table 1.
Distribution. Louisiana, USA, so far known from type locality only. Populations of A. manueli from lowland water bodies of South Carolina (Zokan & Drake, 2015) and of Central America (Wojewódka et al. 2016) probably belong to A. fornshelli sp. nov. instead, as environmental conditions here are clearly different from these of mountain lakes typical for A. manueli and A. cajasi.
description: Published as part of Sinev, Artem Y., 2020, New species of Alpinalona Alonso & Sinev, 2017 (Cladocera: Anomopoda: Chydoridae) from South-East USA, pp. 567-576 in Zootaxa 4750 (4) on pages 568-573, DOI: 10.11646/zootaxa.4750.4.7, http://zenodo.org/record/3708874