Prenda, Francisco Diogo R. Sousa, Lourdes M. A. Elmoor-Loureiro & Sandro Santos, 2016

Francisco Diogo R. Sousa, Lourdes M. A. Elmoor-Loureiro & Sandro Santos, 2016, New findings of Hexalona-branch representatives in Brazil, with a description of Prenda gen. nov. (Crustacea: Anomopoda: Aloninae), Journal of Natural History 50 (43), pp. 1-42 : 28-34

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 pores 3 2 3/2 3 2 2 Lateral head pores Minute Minute Slit or rounded, with underneath Minute Minute Minute sack Labral keel Setulae on posterior Setulae on posterior Setulae on posterior margin Setulae on posterior Spinulae on anterior Notch on anterior margin margin margin margin margin A1 – aesthetascs length Subequal Two longer Subequal Subequal Two longer Subequal A2 – second segment Longer than apical Shorter than apical Shorter than apical Shorter than apical Longer than apical Shorter than apical Length Valves – denticles 0 0–3 0 0 0 0 Valves – groups of setulae Present Present Absent Absent Present Pbsent posteroventral corner PA – shape of postanal Elongated, distal Elongated, distal Relatively elongated, distal portion Short, distal portion Short, distal portion Short, distal portion portion rounded portion rounded rounded or truncated rounded or truncated broadly rounded truncated PA – marginal denticles Composite Composite Composite Composite or single Composite Composite PA – basal spine/ About 0.25–0.35 About 0.2–0.35 About 0.15–0.25 About 0.18–0.25 About 0.25–0.30 Up to 0.25 postabdominal claw P1 – IDL seta 1 Slender, well- Claw-like, well- Well-developed Short Well-developed Well-developed developed developed P1 – seta (i) en1 Well-developed Well-developed Short, flat Absent Developed Rudimentary P1 – anterior setae soft Present Present Present Absent Absent Absent P1 – setulae on ventral face Not organised in Organised in groups Organised in groups Organised in groups Organised in groups Organised in groups clusters P2 – seta soft, base of first Present/absent Absent Absent Absent Absent Absent scraper P2 – seta on exopod Well-developed Well-developed Developed Short Short Short P3 – setae on exopod 7 7 7 7 7 7 P3 – seta 2 setulation From middle portion

, Hard setulae

Short setuale or naked

Short setulae From middle portion, From middle heterogeneous plumose portion, short setulae P3 – setae 3–4 on exopod Similar length Similar length Similar or different length Different length Similar length Similar length P4 – setae 3 on exopod, Similar to 2 Similar to 2 Similar to or shorter than 2 Shorter than 2 Much shorter than 2 Similar to 2 length P5 – exopod Not bilobed Bilobed Bilobed Bilobed Bilobed Bilobed P5 – seta 1 exopod Very short and thin Relatively longer Relatively longer Relatively longer Relatively longer Relatively longer P5 – filter comb Absent Present Present Present Present Present P6 Absent Present Present Present Present Present

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

Figures

Figure 9. Prenda arvensis gen. nov. and sp. nov. from type locality. (A) Habitus; (B) anteroventral corner of carapace; (C) posteroventral corner of carapace; (D – E) head pores; (F) labral keel; (G) antennule; (H) antenna; (I – J) postabdomen; (K) ventral view from terminal claw and basal spines. Scale bars = 50 µm.

Figure 10. Prenda arvensis gen. nov. and sp. nov. from type locality. (A) Maxilla; (B) limb I; (C) idem, third endite; (D) idem – ODL and IDL; (E) limb II; (F) idem, exopod; (G) limb III, exopod; (H – I) idem, endites; (H) distal endite; (I) basal endite; (J) limb IV, exopod; (K – L) idem, endites; (L) filtercomb; (M) limb V; (N) idem, iternal lobe; (O) limb VI. For abbreviations, see Material and methods. Scale bar = 50 µm.

Figure 11. (A – C) Alona cf. guttata: (A) habitus from parthenogenetic female; (B) labral keel; (C) postabdomen. (D – G) Alona elisae sp. nov., holotype: (D) habitus from parthenogenetic female; (E) labral keel; (F) postabdomen; (G) idem, lateral fascicles; (H) habitus from male; (I) male, labral keel and hook; (J) male, postabdomen. (K – N) Alona isabellae sp. nov., holotype: (K) habitus from parthenogenetic female; (L) labral keel; (M) postabdomen; (N) idem, lateral fascicles. (O – R) Prenda arvensis gen. nov. and sp. nov., holotype: (O) labral keel; (P) postabdomen; (Q) limb I; (R) limbs IV, V and VI. For abbreviations, see Material and methods. Scale bars: B, C, E, F, I, J, M, O – R = 25 µm; A, D, H, K = 50 µm.

Tables

Table 1. Main diferences and similarities between Alona quadrangularis - group (Alona sensu stricto) and core groups of Hexalona - branch: Alona a ffi nis - group,

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 pores	3	2	3/2	3	2	2
Lateral head pores	Minute	Minute	Slit or rounded, with underneath	Minute	Minute	Minute
			sack
Labral keel	Setulae on posterior	Setulae on posterior	Setulae on posterior margin	Setulae on posterior	Spinulae on anterior	Notch on anterior
	margin	margin		margin	margin	margin
A1 – aesthetascs length	Subequal	Two longer	Subequal	Subequal	Two longer	Subequal
A2 – second segment	Longer than apical	Shorter than apical	Shorter than apical	Shorter than apical	Longer than apical	Shorter than apical
Length
Valves – denticles	0	0–3	0	0	0	0
Valves – groups of setulae	Present	Present	Absent	Absent	Present	Pbsent
posteroventral corner
PA – shape of postanal	Elongated, distal	Elongated, distal	Relatively elongated, distal portion	Short, distal portion	Short, distal portion	Short, distal portion
	portion rounded	portion rounded	rounded or truncated	rounded or truncated	broadly rounded	truncated
PA – marginal denticles	Composite	Composite	Composite	Composite or single	Composite	Composite
PA – basal spine/	About 0.25–0.35	About 0.2–0.35	About 0.15–0.25	About 0.18–0.25	About 0.25–0.30	Up to 0.25
postabdominal claw
P1 – IDL seta 1	Slender, well-	Claw-like, well-	Well-developed	Short	Well-developed	Well-developed
	developed	developed
P1 – seta (i) en1	Well-developed	Well-developed	Short, flat	Absent	Developed	Rudimentary
P1 – anterior setae soft	Present	Present	Present	Absent	Absent	Absent
P1 – setulae on ventral face	Not organised in	Organised in groups	Organised in groups	Organised in groups	Organised in groups	Organised in groups
	clusters
P2 – seta soft, base of first	Present/absent	Absent	Absent	Absent	Absent	Absent
scraper
P2 – seta on exopod	Well-developed	Well-developed	Developed	Short	Short	Short
P3 – setae on exopod	7	7	7	7	7	7
P3 – seta 2 setulation	From middle portion , Hard setulae	, Hard setulae
	heterogeneous				plumose	portion, short
						setulae
P3 – setae 3–4 on exopod	Similar length	Similar length	Similar or different length	Different length	Similar length	Similar length
P4 – setae 3 on exopod,	Similar to 2	Similar to 2	Similar to or shorter than 2	Shorter than 2	Much shorter than 2	Similar to 2
length
P5 – exopod	Not bilobed	Bilobed	Bilobed	Bilobed	Bilobed	Bilobed
P5 – seta 1 exopod	Very short and thin	Relatively longer	Relatively longer	Relatively longer	Relatively longer	Relatively longer
P5 – filter comb	Absent	Present	Present	Present	Present	Present
P6	Absent	Present	Present	Present	Present	Present