Hyalella carstica, Bastos-Pereira, Rafaela & Bueno, Alessandra Angélica De Pádua, 2012

Bastos-Pereira, Rafaela & Bueno, Alessandra Angélica De Pádua, 2012, New species and new report of Hyalella S. I. Smith, 1874 (Crustacea: Amphipoda: Dogielinotidae) from Minas Gerais state, Southeastern Brazil, Zootaxa 3350, pp. 58-68 : 60-65

Hyalella carstica n. sp. BASTOS-PEREIRA and BUENO

( Fig. 1–31 )

Material examined: Holotype male, Brazil, Minas Gerais, Arcos, Ribeirão dos Patos and São Miguel River, High São Francisco River tributary, São Francisco River hydrographic basin, near Corumbá community (9km from Arcos/MG) (20°19’59.6” S 45°36’25.3”W) ( MNRJ 23052); allotype female ( MNRJ 23053), June 24th, 2010, Bastos-Pereira, R. and Torres, S. H. S. colls.

Paratypes: MNRJ 23054 (2 males; 2 females; 2 juveniles), UFLA 0 178 (10 males; 10 females). All these samples with same data as the holotype.

Type-locality. Brazil, Minas Gerais, Arcos, Ribeirão dos Patos and São Miguel River, tributary São Francisco hydrographic basin, Corumbá (20°19’59.6” S 45°36’25.3”W), 740m high.

Diagnosis. Body surface smooth. Eyes pigmented. Antenna 1 suqequal in size to antenna 2. Antenna 2 more than half body length. Mandibular incisor toothed. Maxilla 1 palp short, reaching to less than half the distance between base of palp and tip of setae on outer plate; inner plate slender, with two strong, pappose apical setae. Maxilla 2 with one strong pappose seta on inner margin. Gnathopod 1 propodus length less than twice maximum width, hammer shape, inner face with five pappose setae, comb scales on disto-posterior and disto-anterior borders. Gnathopod 2 propodus ovate, palm shorter than posterior margin, slope oblique. Pereopods 3 and 4 merus and carpus posterior margin with five hind marginal clusters of short one to two setae; propodus posterior margin five to eight groups of setae. Uropod 1 inner ramus of male with a curved seta. Uropod 3 peduncle slender, wider than ramus, with three strong distal setae, basal width two times or less tip of ramus. Telson longer than wide, apically rounded, with two widely apart strong setae symmetrically distributed on the apical margin, without additional setae present. Sternal gills present on segments 2 to 7.

Description of male ( Fig.1 and 25 ). Mean body length: 5.65 ± 0.79mm, mean cephalothorax length 0.55 ± 0.16; ten paratypes were measured. Body surface smooth. Epimeral plates not acuminate. Coxae 1–4 sub-equal in size and shape, slightly overlapping. Acumination in coxae absent. Coxa 1 with the same size and shape than 2. Coxa 3 shorter than coxa 4. Coxa 4 deeper than wide. Coxa 5 posterior lobe deeper than anterior. Coxa 6 anterior lobe small.

Head smaller than first two thoracic segments, rostrum absent. Eyes pigmented, medium size, round, located behind insertion of antenna 1.

Antenna 1 ( Fig. 2 ) more than half body length, sub-equal in size to antenna 2, longer than peduncle of antenna 2; peduncle longer than head, sub-equal in length to article 2, article 3 is the shortest; flagellum with 12–13 articles, longer than peduncle, basal article not elongated; aesthetascs ( Fig. 3 ) occurring distally on flagellum after article 9.

Antenna 2 ( Fig. 4 ) more than half body length; peduncle slender, longer than head, triarticulate, article 1 is the shortest; flagellum of 14–16 articles, longer than peduncle; basal article elongated.

Basic amphipodan mandible ( Fig. 5 ): incisor toothed; left lacinia mobilis with five teeth; setae row on left mandible with three main pappose setae, right mandible with two pappose setae; molar large cylindrical and triturative; accessory seta present.

Upper lip ( Fig. 6 ) ventral margin round. Lower lip ( Fig. 7 ) outer lobes distally notched, mandibular projection of outer lobes round.

Maxilla 1 ( Fig. 8 ) palp uniarticulate, short, reaching less than half length the distance between base of palp and tip of setae on outer plate, distal setae strong; inner plate slender, smaller than outer plate, with two pappose apical setae, several simple setae on inner margin; outer plate with less than nine serrate setae.

Maxilla 2 ( Fig. 9 ) plates sub-equal in length, inner plate slightly wider than outer plate, bearing several pappose setae on upper and inner margin oh inner plate, outer and inner plates with abundant setules.

Maxilliped ( Fig. 10 ) inner plates apically rounded, with three connate setae, pappose setae only apically; outer plates larger than inner plates, apically rounded, apical, medial and facial simple setae; palp longer than outer plate, four articles; article 2 longer than wide, medial margin with long simple setae; article 3 outer and inner distal faces with several long simple setae; dactylus unguiform, shorter than third article, distal setae simple and as long as or longer than nail, inner border with simple setae.

Gnathopod 1 ( Fig. 11 ) subchelate; carpus longer than wide, longer and wider than propodus, with strong and wide posterior lobe produced and forming a scoop-like structure, open to the inside; border pectinate with several serrate setae, with denticles in their basis; propodus ( Fig. 12 ) width 3/4 of maximum length, hammer-shaped, without setae on anterior border, inner face with five pappose setae, less than five small triangular setae, comb scales on disto-posterior and disto-anterior borders, palm slope transverse, margin slightly concave, posterior distal corner with connate setae; dactylus claw-like, no endal setae, with comb scales on disto-posterior margin, congruent with palm.

Gnathopod 2 ( Fig. 13 ) subchelate, basis hind margin with one to three groups of setae; merus with less than seven setae on posterior margin, postero-distal margin concave, distal corner rounded; carpus posterior lobe ( Fig.

26 and 27) elongated produced between merus and propodus, border pectinate with several serrate setae ( Figs. 29 and 30 ); propodus ( Fig. 14 ) ovate, with comb scales on the lobe, palm shorter than posterior margin of propodus, slope oblique, margin concave with few short fine setae, palm with several cuspidate setae with an accessory seta and simple setae( Fig. 28 ), posterior distal corner with cuspidate setae and with a cup for dactyl; dactylus claw-like, congruent with palm, with several endal setae and a plumose seta on distal margin.

Pereopods 3 ( Fig. 15 ) and 4 ( Fig. 16 ) merus and carpus posterior margin with five hind marginal clusters of 1–2 setae, posterior margin with long setae; propodus posterior margin with five to eight groups of setae; dactylus less than half-length of propodus. Pereopods 5 to 7 slightly longer successively; dactylus less than half-length of propodus. Pereopod 5 ( Fig. 17 ) sub-equal than pereopod 4; coxa posterior lobe as wide as deep. Pereopod 6 ( Fig. 18 ) coxa posterior lobe deeper than wide, larger than posterior lobe of pereopod 5. Pereopod 7 ( Fig. 19 ) longer than pereopod 6; coxa posterior lobe as wide as deep.

Pleopods ( Fig. 20 ) not modified, with coupling spines on peduncle.

Uropod 1 ( Fig. 21 ) longer than uropod 2; peduncle as long as inner ramus; outer ramus shortened, three dorsal cuspidate setae with an accessory seta and three distal setae; inner ramus with two dorsal setae and more than four distal setae, two of them longer, male with curved setae on inner side of the ramus ( Fig.31 ); peduncle setation present.

Uropod 2 ( Fig. 22 ) inner ramus with two dorsal setae and five distal setae; outer ramus with two dorsal and three distal setae; peduncle setation present.

Uropod 3 ( Fig. 23 ) shorter than peduncle of uropod 1, longer than peduncle of uropod 2; inner ramus absent; outer ramus uniarticulate, longer than peduncle, two times or less tip of ramus; five distal setae and no marginal setae; peduncle wider than ramus, setation present.

Telson ( Fig. 24 ) longer than wide, entire, apically rounded, with two widely apart strong setae symmetrically distributed on the apical margin.

Coxal gills sac-like, present on pereonites 2 to 7. Sternal gills tubular, present on pereonites 2 to 7.

Female. Body length: 4.96 ± 0.45 mm (n=10), cephalothorax length 0.49 ± 0.06 (n=10) ( Figs. 32–36 )

Antenna 1 flagellum with 11–12 articles ( Fig. 32 ).

Antenna 2 similar in shape to male; flagellum with 12–14 articles ( Fig 33 ). Gnathopod 1 ( Fig. 34 ) similar in size and different in shape to gnathopod 2; propodus of gnathopod 1 narrower and longer than in male.

Gnathopod 2 ( Fig. 35 and 36 ) different to male gnathopod 2 in shape and smaller; propodus length two to three times maximum width, subchelate, palm transverse; carpus, propodus and dactylus with several comb scales.

Habitat. Freshwater, epigean.

Etymology. The specific name refers to the site where the specimens were collected, in the karstic province of Arcos, Minas Gerais, Brazil.

Remarks. The new species, H. carstica , resembles the H. gracilicornis , H. longistila and H. meinerti especially in the inner distal margin of gnathopod 2, all of them presenting lobe and similar setation, and absence of flanges on peraeon and pleonites. It differs from them by the presence of curved seta on inner ramus of uropod 1, telson shape, the number of coxal gills and inner face setae of the gnathopod 1 propodus.

Figures

FIGURES 1 – 9. Hyalella carstica n. sp. male. (1) Habitus (holotype male: body length = 5.64 mm, cephalotorax length = 0.49 mm); (2 – 9) Paratype male (body length = 5.56 mm, cephalotorax length = 0.51); (2) Antenna 1; (3) Antenna 1 article, the arrow indicates an aesthetasc; (4) Antenna 2; (5) Mandible; (6) Upper lip; (7) Lower lip; (8) Maxilla 1; (9) Maxilla 2. Scales: (1) represents 0.0206 mm, (2) 0.206 mm, (3) 0.103 mm, (4) 0.206 mm, (5 – 9) 0.103 mm.

FIGURES 10 – 14. Hyalella carstica n. sp. paratype male (body length = 5.56 mm, cephalotorax length = 0.51). (10) Maxillipod; (11) Gnathopod 1; (12) Gnathopod 1 propodus and dactylus; (13) Gnathopod 2; (14) Gnathopod 2 propodus and dactylus Scales: (10) represents 0.103 mm; (11) 0.206 mm; (12) 0.103 mm; (13) 0.206 mm; (14)) 0.206 mm.

FIGURES 15 – 19. Hyalella carstica n. sp. paratype male (body length = 5.56 mm, cephalotorax length = 0.51). (15) Pereopod 3; (16) Pereopod 4; (17) Pereopod 5; (18) Pereopod 6; (19) Pereopod 7. Scales: (15 – 19) represents 0.206 mm.

FIGURES 20 – 24. Hyalella carstica n. sp. paratype male (body length = 5.56 mm, cephalotorax length = 0.51). (20) Pleopodos; (21) Uropod 1; (28) Uropod 2; (29) Uropod 3; (30) Telson. Scales: (20 – 24) represents 0.103 mm.

FIGURES 25 – 31. Hyalella carstica n. sp. paratype male (body length = 5.56 mm, cephalotorax length = 0.51); (25) Alive specimen; (26 – 27) Picture from photonic microscope - Gnathopod 1 carpus; (26) PL: Posterior lobe; (27) T 1: Comb-scales and D: denticles on posterior lobe; (28 – 29) Scanning Electron Microscopy of Gnathopod 2 carpus posterior lobe; (28) Posterior lobe, F 3 setae; (29) T 1: Comb-scales and D: denticles; (30) Palm of gnathopod 2 propodus; (31) Curved setae on inner ramus of Uropod 1. Scales: (26 – 27) 0.026 mm, (28 – 29) 10 µm, (30) 30 µm; (31) 20 µm.

FIGURES 32 – 36. Hyalella carstica n. sp. allotype female (body length = 4.92 mm, cephalotorax length = 0.49 mm). (32) Antenna 1; (33) Antenna 2; (34) Gnathopod 1; (35) Gnathopod 2; (36) Gnathopod 2 propodus and dactylus. Scales: (32 – 36) represents 0.206 mm.