Prendalona arvensis (Sousa, Elmoor-Loureiro & Santos, 2016)

Sinev, Artem Y., Sousa, Francisco Diogo Rocha & Elmoor-Loureiro, Lourdes M. A., 2023, Revision of the guttata-group of Alona s. lato leads to its translocation to Prendalona Sousa, Elmoor-Loureiro & Santos, 2018 (Cladocera: Anomopoda: Chydoridae), Zootaxa 5293 (1), pp. 95-121 : 99

Prendalona arvensis (Sousa, Elmoor-Loureiro & Santos, 2016)

( Fig.1 )

Sousa, Elmoor-Loureiro & Santos, 2016: 34–37, fig. 9–10, 11Q–R ( Prenda )

Type locality. A temporary pond located in a high-altitude field (aproximately 1200 m), Bom Jesus , Rio Grande do Sul, Brazil (28°36ʹ57ʺS, 50°22ʹ11ʺW) .

Type material. Holotype: Dissected parthenogenetic female deposited at the Museum of Zoology of the State University of Bahia, accession number UFBA2168 . Paratypes: Four parthenogenetic females from type locality, deposited at Laboratório de Taxonomia Animal, Universidade Federal de Jataí, accession number FDRS216-219 .

Material examined earlier: see Sousa et al. (2016) for list of material from type locality.

Diagnosis. Parthenogenetic female. General ( Fig. 1A ) oval in lateral view, strongly compressed laterally, of moderate height, maximum height at middle of body, in adults height/length ratio about 0.63. Dorsal margin uniformly curved; postero-dorsal and postero-ventral angles broadly rounded; posterior margin uniformly curved; ventral margin almost straight; antero-ventral angle rounded. Valve with a well-developed pattern of longitudinal lines. Ventral margin ( Figs. 1B–C ) with about 35 setae. Postero-ventral angle ( Fig. 1C ) bears about 60 short, thin, hair-like setulae.

Head. Eye larger than ocellus. Head shield without sculpturing, posterior margin of head shield broadly rounded ( Fig. 1D ). Two major head pores. PP about 0.5 IP. Lateral head pores located at about 1.5 IP distance from midline, at the level between major head pores. Labral keel ( Fig. 1E ) with a blunt prominence in upper portion of anterior margin, without clusters of setulae on posterior margin.

Postabdomen ( Fig. 1F ) short, of moderate width, narrowing distally, with a rounded, prominent distal angle; length about 2.8 height. Ventral margin straight. Distal margin convex. Dorsal margin with distal part 2 times longer than preanal one, anal and postanal portion of similar length. Postanal portion of dorsal margin straight to weakly concave, anal portion concave. Postanal margin with 6–7 well-developed composite marginal denticles, three distalmost denticles significantly larger than others, most bearing spinules on anterior margin; length of distal denticles equal to the width of the postabdominal claw base. Anal margin with 3 clusters of thick spinulae. Postanal margin with 8–10 lateral groups of setulae, six–seven distalmost groups narrow, consisting of 5–7 thin setulae decreasing in length anteriorly, posteriormost seta being longest, of same thickness as others. Postabdominal claw curved, of moderate length, as long as preanal portion of postabdomen. Basal spine short, weakly curved, about 0.2 of claw length.

Morphology of antennule and antenna typical for the genus. Morphology of thoracic limbs typical for the genus. Thoracic limb I ( Figs. 1G–H ) with a rudimentary seta i on endite 1. Thoracic limb III with setae 4 and 5 of similar length, two times shorter than seta 6.

Ephippial female and male unknown.

Size: length of adult parthenogenetic female up to 0.37 mm.

Differential diagnosis. P. arvensis clearly differs from all other species of the genus in (1) two main head pores, and (2) labrum with a blunt prominence at its anterior margin.

Distribution and ecology. To date known from the type locality only, a temporary pond covered by Sphagnum at a high-altitude field, with acid water (pH<5).

Figures

FIGURE 1. Prendalona arvensis (Sousa, Elmoor-Loureiro & Santos, 2016), parthenogenetic female.A, lateral view. B–C, anterior and posterior parts of ventral margin of valve. D, posterior portion of head shield in lateral view. E, labrum. F, postabdomen. G, thoracic limb I. H, ODL and IDL of thoracic limb I (after Sousa et al. 2016a).