Alona elisae, 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 : 12-23

Alona elisae sp. nov.

( Figures 4 – 6 , 11 )

Type locality

Rock pool near Rosário Waterfall, Pirenópolis, Goiás (15°42 ʹ 34 ʺ S, 48°59 ʹ 33 ʺ W).

Type material

Holotype: undissected, adult parthenogenetic female in a tube with 92% ethanol deposited at the Museum of Zoology of the State University of Bahia under accession number UFBA3180 . The label of the holotype is: ‘ Alona elisae sp. n., 1 parth. ♀ from the rock pool near Rosário Waterfall, Pirenópolis , Goiás Distrito Federal, Brazil. Holotype ’.

Material examined

Paratypes: Thirty-eight adult parthenogenetic females, two ephipial females and 11 males from a rock pool near Rosário Waterfall, Pirenópolis, Goiás (15°42 ʹ 34 ʺ S, 48° 59 ʹ 33 ʺ W), material collected by Lourdes M.A. Elmoor-Loureiro on 6 July 2009 (EL02226; FDR0384).

Etymology

Species name honours Elisa Alvim, wife of FDRS.

Diagnosis

Female. Maximum height at the middle of the body, body height/length ratio about 0.67, moderate lateral compression. Head with ocellus and eye of similar sizes. Two main pores connected; PP about same length as IP; lateral head pores tiny. Labrum with 10 – 11 short spinulae of similar sizes at anterior portion, posterior margin armed with two clusters of setulae. Carapace armed with longitudinal lines; ventral margin almost straight, with 56 plumose setae forming three groups; inner proximal spinulae longer and thicker than others and projected beyond the margin. Antennule about 3 times longer than wide. Antenna: antennal formula: spines 001/101, setae 113/003; median segment of the exopod and endopod long, similar in length to apical segments; seta on first segment of the exopod thin, not exceeding the length of branches of the antenna. Postabdomen relatively long, about 2.7 times as long as wide; distal portion broadly rounded; first spinule of distalmost fascicles thicker than others and exceeding the postabdomen margin but not the level of the marginal denticles; 8 – 9 marginal denticles, proximal merged and organised in groups. Postabdominal claw about 0.3 of the length of the postabdomen, with one group of 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 about 1.4 – 1.6 times longer than the width of base of the claw, armed with spinulae. Limb I with IDL with three groups of spinulae on its face, three setae present; seta 1 relatively short, about half the length of other setae and armed with spinulae. Limb II with elongated exopod, one setulated seta present; inner limb portion armed with one element; scraper 4 longer than 5; scrapers 6 – 8 of different sizes, decreasing in length towards gnathobase. Limb III with seven setae on the exopod; setae 6 – 7 of different length. Limb IV with six setae on the exopod, setae 3 – 6 plumose; second and first seta armed with short setulae. Limb V with incursion between lobes relatively shallow, armed with four setae; filter plate bearing three setae armed with lateral spinulae. Limb VI present, 2.6 times longer than width.

Male. Smaller than female, body height/length ratio about 0.58. Head with short rostrum; main head pores connected; PP about 0.6 IP; lateral head pores tiny, located between main head pores. Carapace with longitudinal lines, armed with 36 plumose setae forming three groups. Antennule about 2.3 times as long as wide; aesthetascs of different length; male seta about 2.7 times shorter than length of antennular body. Postabdomen with dorsal and ventral margin almost parallel; short marginal spinulae that occupy whole margin, not arranged in groups; first spinule of distalmost fascicles thicker than others and exceeding the postabdomen margin; gonopores opening ventrally, subapically to postabdominal claw. Postabdominal claw smaller and thicker than in female. Basal spine slightly longer than width of the base of the claw, naked. Limb I with U-shaped copulatory hook, arms of different length; IDL with three setae, of which one is a male seta.

Ephipial female. Ephipium with punctuate ornamentation and covered by longitudinal lines, brownish.

Description

Parthenogenetic females. Habitus ( Figures 4 A – C, 11D). In lateral view, the carapace is oval, maximum height at middle of body, body height/length ratio about 0.67, moderate lateral compression. Dorsal margin convex. Dorsal keel absent.

Head ( Figure 5 A – D). Ocellus and eye of similar sizes. Head shield with maximum width behind the mandibular articulation, line of posterior margin straight and angular. Rostrum short, rounded, in lateral view projected towards ventral margin of carapace. Two connected main pores of similar size, connection relatively wide; PP about same length as IP; lateral head pores tiny, located at level between main head pores, distance from midline slightly shorter than IP. Labrum ( Figures 5 E, 11E). Anterior margin convex armed with 10 – 11 short spinulae of similar size; posterior margin with two clusters of setulae; apex rounded.

Carapace ( Figures 4 A – B, D, 11D). Covered with longitudinal lines; ventral margin almost straight, with 56 plumose setae per valve forming three groups, groups with long setae (anterior and posterior) separated by a group of short setae. Posterior margin straight, armed with long internal spinulae: spinulae at posteroventral corner longer and thicker than others and projected beyond the margin.

Antennule ( Figure 5 F). Not exceeding the tip of rostrum, about 3 times longer than wide; four rows of short setulae on antennular body. Antennular sensory seta slender, about 1.3 times smaller than antennular body, inserted in last third of antennule from its base. Nine aesthetascs projecting beyond the tip of rostrum, two long aesthetascs present. None of the aesthetascs exceeds the length of the antennules.

Antenna ( Figure 5 G). Two coxal setae of equal length. Basal segment thick, armed with a short spine and spinulae. Antennal formula: spines 001/101, setae 113/003. Median segment of exopod and endopod long, similar in length to apical segments. Seta on first segment of exopod thin, armed with fine setulae, not exceeding the length of branches of antenna. Seta on second segment of exopod bisegmented, similar in length to shorter apical seta. Spine on first segment of endopod short, exceeding half the length, but not reaching the end of second segment. Apical spines of endopod and exopod shorter than apical segments of antenna. Apical setae bisegmented and setulated. All segments have spinulae at terminal portion; setulae on the second segment of the exopod long.

Abdomen about 3 times shorter than thorax, armed with two rows of abdominal setae.

Postabdomen ( Figures 4 F – G, 11F – G). Relatively long, about 2.7 times as long as wide, ventral margin slightly rounded, with two rows of short spinulae. Distal portion broadly rounded. Anal margin very long, occupying about 60% of postabdomen length. Nine to 10 lateral fascicles armed with thin spinulae; first spinule of distalmost fascicles thicker than others and exceeding the postabdomen margin, but not the level of the marginal denticles; 8 – 9 marginal denticles increasing in length towards the distal portion; distalmost denticles bear spinulae on the anterior margin; proximalmost denticles grouped. Postabdominal seta ( Figure 4 G). About 1.5 times shorter than postabdomen length, bisegmented; setulae on the first segment short when compared to setulae of the second segment. Postabdominal claw ( Figure 4 G – H). About 0.3 of the length of the postabdomen; implanted at the projected short base from the postabdomen, uniformly curved, with one group of short spinulae on base itself; 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 ( Figure 4 G – H). About 1.4 – 1.6 times longer than length of width of claw at its base; basal spines armed with spinulae that reach the distal portion.

Mandibles not studied. Maxilla ( Figure 6 A). Armed with two setulated setae. Six pairs of limbs.

Limb I ( Figure 6 B – C). Epipod oval with long projection. ODL with thin seta serrated at distal part, longer than length of IDL (en4) setae; accessory seta not studied. IDL with three groups of spinulae on its face, three setae present; seta 1 relatively short, about half the length of other setae and armed with short spines; setae 2 and 3 of different sizes, bisegmented and armed with setulae. Endite 3 with four setae; posterior setae (a – b) of similar length to anterior seta 1. Endite 2 with two rows of spinulae; three posterior setae present (d – f), seta (f) 0.3 times shorter than seta (e), both setae have thick spinulae on the lateral face; seta (d) setulated and exceeding half the length of seta (e). Endite 1 with three posterior setae (g – i); setae (g) and (h) bisegmented and densely setulated in distal part, of similar length; seta (i) relatively short, about 0.2 of setae (g) and (h) lengths. Ejector hooks of different lengths and armed with short denticles. Ventral face of the limb with seven groups of setulae organised in clusters, decreasing in length towards the distal portion. Gnathobase elongated; setulae were not observed on the gnathobase.

Limb II ( Figure 6 D – E). Exopod elongated, with two rows of setulae; one seta present, setulated at distal portion, about 2 times shorter than exopod itself. Inner limb portion armed with eight scrapers and a sensilum; scraper 3 shorter than 2 and 4; scraper 4 longer than 5; scrapers 6 – 8 of different size, decreasing in length towards gnathobase. Scrapers 1 – 4 armed with fine spinulae; scrapers 5 – 8 armed with fine spines. Proximal portion of the gnathobase short, apex armed with setulae; distal portion armed with four elements, first as a robust sensillum, second as element with distal portion acute and slightly geniculated, third element armed with denticles, fourth element long. Filter comb with seven setae; first and second setae short; other setae long and slightly setulated (setulae not showed on the figures).

Limb III ( Figure 6 F – H). Epipod not studied. Exopod subquadrangular, with five distal and two lateral setae. Seventh seta setulated and about 1.6 times longer than sixth seta; sixth seta setulated. Fifth seta long, armed with short setulae, about 1.7 times longer than second seta. Fourth and third seta setulated and similar in length. Second seta about 2.8 times longer than first seta; armed with long setulae from to median portion. First seta naked. Distal endite armed with a sensillum and three setae (1 – 3), two scraper-like of different length (1 – 2); third seta curved and armed with many setulae bilaterally implanted (3); four plumose posterior setae similar in length (a – c). Basal endite with four soft anterior setae increasing in length towards the gnathobase. Gnathobase armed with four elements, the first being a cylindrical sensillum, the second a geniculated seta and third and fourth elements with tip acute, naked. Filter comb with seven setae (setulae not showed on the figures).

Limb IV ( Figure 6 I – K). Pre-epipod rectangular and densely setulated. Epipod oval with a long projection. Exopod subquadrangular with six marginal setae; setae 3 – 6 plumose; seta 6 slightly longer than setae 4 – 5; setae 4 – 5 similar in length; third seta short, about 3 times shorter than second seta; second seta about 1.2 times longer than first seta; second and first setae armed with short setulae. Distal endite with a sensillum and four setae (1 – 4), one scraper-like (1), three flaming torch-like (3 – 4); the first flaming torch relatively robust, with long setulae (2). Basal endite with three soft setae slightly setulated increasing in length proximally (a – c). Gnathobase armed with one globular sensillum and one setulated seta implanted on a robust base. Filter plate with five setae (setulae not showed on the figures).

Limb V ( Figure 6 L). Pre-epipod oval and densely setulated, epipod with a long projection. Exopod divided into two lobes, incursion between lobes relatively shallow; four plumose setae present; setae 3 – 4 similar in length, about 1.4 times longer than seta 2; first seta about 3 times shorter than seta 2. Internal lobe wide, oval and with long setulae; two setulated setae on the inner face of the lobe, first seta longer than length of the lobe. Filter plate armed with three setae that bear spinulae; an element present.

Limb VI ( Figure 6 M). An elongated lobe, about 2.6 times longer than width of lobe; apical margin of the lobe with long setulae; lateral margin not totally setulated.

Male. Habitus ( Figures 4 I, 11H): Smaller than female, body about 1.5 times as long as height, elongated, without lateral compression; less arched than female.

Head ( Figures 4 I, 11H). Rostrum short, ocellus and eye of similar sizes. Two main pores connected of similar sizes; PP about 0.6 IP; lateral head pores tiny, located between main head pores. Labrum ( Figure 11 I) as described for females.

Carapace ( Figures 4 I, 11H). With evident longitudinal lines; with 36 plumose setae per valve forming three groups, groups with long setae (anterior and posterior) separated by a group of short setae.

Antennule ( Figure 5 I). Not exceeding tip of rostrum, about 2.3 times as long as wide. Aesthetascs of different length and not exceeding the length of antennule. Sensory seta about 1.7 times shorter than antennular body. Male seta thick, about 2.7 times shorter than length of antennular body, inserted near to apex of antenullar body.

Antenna as described for females. In one individual, the exopod of left antenna had the second and third segments modified in more slender structure; the apical segment was sharp and densely setulated; no apical setae were observed ( Figure 5 J).

Postabdomen ( Figures 4 J – K, 11J). Smaller in length than female, dorsal and ventral margin almost parallel; anal margin long as in female; short marginal spinulae that occupy whole margin, not arranged in groups; 10 lateral fascicles armed with thin spinulae; first spinule of distalmost fascicles thicker than others and exceeding the postabdomen margin; gonopores opening ventrally, subapically to postabdominal claw. Postabdominal seta as in females. Postabdominal claw smaller and thicker than in female, tip acute, armed with a group of short spinulae on the base. Basal spine slightly longer than claw at its base, naked.

Limb I ( Figure 5 K – L). Smaller than that of the female, copulatory hook U-shaped, arms of different lengths; projections on tip present. Copulatory brush armed with many setulae, copulatory brush seta longer than seta (g) on the endite 1; ODL with a long seta, accessory seta not studied. IDL with three setae of which one is a male seta, male seta robust and slightly shorter in length than other setae on IDL.

Ephipial female ( Figure 4 E). With body about 0.69 longer than height. Ephipium with punctuate and longitudinal lines ornamentation, brownish.

Size. The length of the adult parthenogenetic females was 0.35 – 0.39 mm. In juveniles the length was 0.29 – 0.36 mm. The length of adult males was 0.26 – 0.29 mm. In juvenile male, the length was up to 0.24 mm. The length of the ephipial female was 0.39 mm.

Remarks. Alona elisae sp. nov. differs from Alona isabellae sp. nov. in the proportion of length/height of body; presence of one group of proximal spinulae on the posterior margin of carapace; morphology of labral keel that bears 10 – 11 spinulae on the anterior margin; PP about same length as IP; setulae of distalmost lateral fascicles not exceeding the level marginal denticles on postabdomen; first seta on IDL that bears short spines; setae on filter comb of fifth limb armed with visible lateral spinulae. There are two descriptions of A. intermedia from specimens of the Paleartic zone ( Alonso 1996; Flössner 2000) and drawings of Neartic individuals ( Chengalath 1987) that suggest some differences and similarities when compared to A. elisae sp. nov.: the labral keel and the first seta of IDL present in Flössner (2000) are naked; the description of Alonso (1996) resembles A. elisae sp. nov. in many morphological traits, including the armature of labral keel, postabdomen, and first and fourth limbs. However, in this description there is no mention of spines on the first seta of IDL or spinulae on the filter comb setae of the fifth limb; also, setae 6 – 7 of the third limb have similar lengths. Regarding the adult male, the postabdomen shape of A. elisae sp. nov. is more rectangular, with a parallel margin ventral and dorsal, while in Flössner (2000) and in drawings of Chengalath (1987) it is more conical.

Geographical distribution. So far, A. elisae sp. nov. has only been observed in the locality studied here (15°42ʹ34ʺS, 48°59ʹ33ʺW). This population was observed in a lateral rock pool formed from a waterfall. Alonaelisae sp. nov. is an endemic species.

Figures

Figure 4. Alona elisae sp. nov. from a rock pool near Rosário Waterfall, Pirenópolis Goiás. (A – B) Habitus from parthenogenetic female; (C) frontal view; (D) posteroventral corner of carapace; (E) ephipial female; (F – G) postabdomen; (H) ventral view from terminal claw and basal spines; (I – K) male: (I) habitus from adult; (J) postabdomen, juvenile; (K) idem, adult. Scale bars = 50 µm.

Figure 5. Alona elisae sp. nov. from a rock pool near Rosário Waterfall, Pirenópolis Goiás. (A – F) Parthenogenetic females: (A) head shield; (B – C) head pores; (D) head; (E) labral keel; (F) antennule; (G) antenna. (H – M) Male: (H) head pores; (I) antennule; (J) abnormal antenna; (K – L) limb I, adult; (M) idem, juvenile. For abbreviations, see Material and methods. Scale bars = 50 µm.

Figure 6. Alona elisae sp. nov. from a rock pool near Rosário Waterfall, Pirinópolis Goiás. (A) Maxilla; (B) limb I; (C) idem – ODL and IDL; (D) limb II; (E) idem, exopod; (F) limb III, exopod; (G – H) idem, endites; (G) distal endite; (H) basal endite; (I) limb IV, exopod; (J – K) idem, endites; (J) distal endite; (K) basal endite; (L) limb V; (M) 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.