Prenda gen. nov.

(Figures 9 – 11)

Type species

Prenda arvensis gen. nov. and sp. nov.

Etymology

The genus name honours the regional culture from Rio Grande do Sul state, where the word ‘ Prenda ’ is used in reference to a young woman.

Diagnosis

Female. Carapace oval, with posterior margin slightly elongated; maximum height at middle of body, body height/length ratio about 0.63; not laterally compressed. Head with ocellus and eye of different size; two main pores connected; connection relatively wide; PP about 0.5 IP; lateral head pores tiny. Labrum presenting anterior margin armed with large notch, posterior margin with two clusters of setulae. Carapace armed with longitudinal fine lines; ventral margin almost straight, with 36 plumose setae per valve, posterior setae long; inner proximal spinulae not arranged in groups, projected beyond the margin. Antennule about 2 times longer than wide; antennular sensory seta short, about 3 times smaller than the antennular body; nine aesthetascs shorter than length of the antennular body. Antenna: antennal formula: spines 001/101, setae 113/003; median segment of exopod and endopod shorter than apical segments; seta on first segment of exopod thin, not exceeding the length of branches of antenna. Postabdomen about 2.8 times as long as wide; postanal margin slightly concave, truncated; preanal and postanal angles evident; seven robust merged marginal denticles increasing in length towards the distal portion; 8 – 10 lateral fascicles armed with thin setulae which are poorly developed. Postabdominal claw armed with 3 – 4 short spinulae on the base; pecten armed with one row of inner and outer spinulae; outer row with spinulae of similar length; distal spinulae on inner row longer than others. Basal spine similar in length to the width of the claw at its base, naked. Limb I with IDL with two groups of spinulae on its face, three setae present; seta 1 relatively developed, about 3.5 times shorter than setae 2 – 3, naked; setae 2 – 3 armed with short and slight setulae. Seta 1 of third endite slender, setae (a – b) longer than seta 1. Setae (e – f) similar in lengths, one element present on the endite; endite 1 armed with one reduced seta (i). Limb II with elongated exopod, one setulated seta present; setae 1 – 2 on the inner portion long, of similar lengths; filter comb armed with seven setae, first seta shorter than others. Limb III with seven setae on the exopod; setae 6 – 7 of different lengths; setae 3 – 4 similar in lengths; first seta naked, shorter than midlength of second seta. Gnathobase armed with four elements, one not acute. Limb IV with six setae on the exopod, of which 3 – 6 are plumose; seta 4 slightly longer than setae 5 – 6; third seta long, similar in length to second seta; first seta naked. Limb V with relatively shallow incursion between lobes, armed with four setae; filter plate bearing three naked setae and one element. Limb VI present, 1.3 times longer than width; only one lateral margin is totally setulated.

Male. Unknown.

Ephipial female. Unknown.

Differential diagnosis

Prenda gen. nov. belongs to the Hexalona -branch, but has exclusive morphological traits that differentiate it from other species-groups that compose the aforementioned lineage. From Alona a ffi nis -group it differs in its short size and lower number of marginal denticles on the postabdomen. From A. costata -group it differs in the absence of lateral head pores pocket-shaped. From Alona guttata -group, Prenda gen. nov. is distinguished by presenting two main head pores, distal marginal denticles on the postabdomen about 1.4 – 1.6 longer than the width at base (in A. guttata this is 2.5 – 3), a long seta 1 on the IDL, rudimentary seta on endite 1 of the first limb, long third seta on the exopod of the fourth limb and wide lobe of the sixth limb. From A. intermedia -group, Prenda gen. nov. is differentiated by the short length of the second segment of the branches of the antenna, postabdomen shape, labral keel and organisation of setae on the valves. In the limbs of Prenda gen. nov., the main differences when compared to A. intermedia -group are related to a rudimentary seta on the first endite of the first limb, second seta on the exopod of the third limb not plumose and long third seta on the exopod of the fourth limb. Similarities and differences between species group related to the Hexalona -branch are presented in Table 1. In the near future the members of A. guttata -group, A.

Alona costata -group, Alona guttata -group, Alona intermedia -group and Prenda gen. nov. quadrangularis -group a ffi nis -group costata -group guttata -group intermedia -group Prenda gen. nov.Main head pores323/2322Lateral head poresMinuteMinuteSlit or rounded, with underneathMinuteMinuteMinutesackLabral keelSetulae on posteriorSetulae on posteriorSetulae on posterior marginSetulae on posteriorSpinulae on anteriorNotch on anteriormarginmarginmarginmarginmarginA1 – aesthetascs lengthSubequalTwo longerSubequalSubequalTwo longerSubequalA2 – second segmentLonger than apicalShorter than apicalShorter than apicalShorter than apicalLonger than apicalShorter than apicalLengthValves – denticles00–30000Valves – groups of setulaePresentPresentAbsentAbsentPresentPbsentposteroventral cornerPA – shape of postanalElongated, distalElongated, distalRelatively elongated, distal portionShort, distal portionShort, distal portionShort, distal portionportion roundedportion roundedrounded or truncatedrounded or truncatedbroadly roundedtruncatedPA – marginal denticlesCompositeCompositeCompositeComposite or singleCompositeCompositePA – basal spine/About 0.25–0.35About 0.2–0.35About 0.15–0.25About 0.18–0.25About 0.25–0.30Up to 0.25postabdominal clawP1 – IDL seta 1Slender, well-Claw-like, well-Well-developedShortWell-developedWell-developeddevelopeddevelopedP1 – seta (i) en1Well-developedWell-developedShort, flatAbsentDevelopedRudimentaryP1 – anterior setae softPresentPresentPresentAbsentAbsentAbsentP1 – setulae on ventral faceNot organised inOrganised in groupsOrganised in groupsOrganised in groupsOrganised in groupsOrganised in groupsclustersP2 – seta soft, base of firstPresent/absentAbsentAbsentAbsentAbsentAbsentscraperP2 – seta on exopodWell-developedWell-developedDevelopedShortShortShortP3 – setae on exopod777777P3 – seta 2 setulation From middle portion, Hard setulae, Hard setulaeShort setuale or nakedShort setulaeFrom middle portion,From middleheterogeneousplumoseportion, shortsetulaeP3 – setae 3–4 on exopodSimilar lengthSimilar lengthSimilar or different lengthDifferent lengthSimilar lengthSimilar lengthP4 – setae 3 on exopod,Similar to 2Similar to 2Similar to or shorter than 2Shorter than 2Much shorter than 2Similar to 2lengthP5 – exopodNot bilobedBilobedBilobedBilobedBilobedBilobedP5 – seta 1 exopodVery short and thinRelatively longerRelatively longerRelatively longerRelatively longerRelatively longerP5 – filter combAbsentPresentPresentPresentPresentPresentP6AbsentPresentPresentPresentPresentPresent

intermedia -group, A. costata -group and A. a ffi nis -group will be transferred to other genera, different from Alona .