Flavalona bicolor ( Frey, 1965 ) Sinev & Dumont, 2016

Sinev, Artem Y. & Dumont, Henri J., 2016, Revision of the costata-group of Alona s. lato (Cladocera: Anomopoda: Chydoridae) confirms its generic status, European Journal of Taxonomy 223, pp. 1-38 : 25-27

Flavalona bicolor ( Frey, 1965) comb. nov.

Fig. 6 A–F

Alona bicolor Frey, 1965: 169–170 , fig. 23–29.

Alona bicolor – Frey 1969: 380–386, fig. 1–6. — Smirnov 1971: 363–365, fig. 421 — Sinev 2009: 60–65, fig. 1–3.

Diagnosis

Female

Length of adult 0.50–0.62 mm. Body ( Fig. 6A ) regular oval, maximum height at the middle of body, height/length ratio about 0.65–0.72. Valves from previous molts often retained. Posteroventral angle

without setules protruding beyond valve margins. Ventral margin with ca 60 setae. Valves without sculpture.

Eye smaller than ocellus. Rostrum elongated, about 1.5–2 length of antennule, with rounded apex. Posterior margin of head shield ( Fig. 6B ) triangular with rounded apex. Three major head pores ( Fig. 6C ) of similar size, middle pore located closer to posterior pore. Connection between pores narrow. PP about 2 IP. Lateral head pores of about 0.4 IP length, lateral pore pockets shallow, with depth about ¼ of pore length. Labral keel ( Fig. 6D ) with 1–2 denticles on anterior margin.

Postabdomen ( Fig. 6E ) truncated, length less than 2.5height.Distal margin convex, distal angle prominent, rounded. Dorsal margin weakly convex in preanal part, concave in anal part, and almost straight in postanal part. Distal part of dorsal margin 3 times longer than preanal one, anal and preanal portions of similar length. Preanal and postanal angles weakly defined. Postanal margin of postabdomen provided with 6–7 marginal denticles. Anal margin with 3–4 more slender denticles and 3–4 clusters of marginal setules. 10–14 lateral fascicles of setules, central setules in fascicle being longest. Postabdominal claw 1.5–1.7 times longer than preanal portion of postabdomen. Basal spine short, robust, about 0.15 length of claw itself.

Antennule with longest aesthetasc as long as antennule. Limb II with scrapers 3 and 7 thicker and armed with more robust denticles than other. Exopodite III with seta 6 of about ⅔ length of seta 3. Exopodite IV with seta 3 being longest, setae 1–2 slightly shorter, setae 4–6 about half length of seta 3, seta 4 longer than setae 5–6. Epipodites IV–V without processes. Exopodite V oval.

Male

Length 0.51–0.53 mm. Body low oval, height/length ratio ca 0.55–0.59. Ocellus larger than eye. Postabdomen ( Fig. 6F ) evenly truncated. Preanal and postanal angles not defined. Distal part of postabdomen 3.5 times longer than preanal. Distal process long, ca ⅔–¾ length of claw. Distal clusters of marginal setules long, about two widths of postabdominal claw base. Postabdominal claw short, basal spine short, about 0.1 length of claw.

Differential diagnosis

Flavalona bicolor comb. nov. differs from all other species of the rustica -clade by an elongated rostrum, an ocellus larger than the eye, labral keel with blunt denticles and large IP/PP ratio (about 2). Males differ by their large size and long distalmost marginal setules at the end of the postabdomen.

Type material

Holotype

Parthenogenetic female, British Museum (Nat. Hist.), London, 1963.6.24.1.

Material studied earlier

See Sinev (2009) for list of material from the U.S.A.

Type locality

UNITED STATES OF AMERICA: Goodwill Pond, Barnstable County, Massachusetts.

Distribution and ecology

Flavalona bicolor comb. nov. inhabits East Canada and North-East U.S.A. ( Sinev 2009). According to Chengalath (1982, 1987), it is not found west of the Ontario- Manitoba border. It is found only in areas with rocky or sandy bottom, and is more rare than F. cf. rustica and F. cf. costata .

Figures

Fig. 6. Flavalona bicolor (Frey, 1965) comb. nov. A–E. Parthenogenetic ♀. A. Lateral view (specimen retaining valves from previous moult). B. Head shield. C. Head pores. D. Labrum. E. Postabdomen. F. Postabdomen of adult ♁. — G–J. Flavalona hudeci (Sinev, 1999) comb. nov., parthenogenetic ♀ G. Lateral view. H. Head pores. I. Posteroventral corner of valves. J. Thoracic limb V. — K–O. Flavalona iheringula (Sinev & Kotov, 2004) comb. nov. K–M. Parthenogenetic ♀. K. Lateral view. L. Head pores. M. Thoracic limb V. N–O. Adult ♁. N. Lateral view. O. Postabdomen. — P. Flavalona sphagnophila (Van Damme & Eggermont, 2011) comb. nov., parthenogenetic ♀, head pores. Figures A–F from Sinev (2009), G–J redrawn from Hudeč (1998), K–M from Sinev (2001), N–O from Kotov & Sinev (2004) and P redrawn from Van Damme & Eggermont (2011).