Notodiaptomus nelsoni Previattelli, Perbiche-Neves & Rocha

Previattelli, Daniel, Perbiche-Neves, Gilmar & Rocha, Carlos E. F. da, 2017, A new species of Notodiaptomus from the Amazon basin (Crustacea, Copepoda, Calanoida, Diaptomidae), ZooKeys 678, pp. 11-30 : 11-14

Notodiaptomus nelsoni Previattelli, Perbiche-Neves & Rocha sp. n. Figures 1, 2, 3, 4, 5, 6, 7, 8, 9

Material examined.

Holotype. One male, entire, alcohol + glycerine (MZUSP30604), Arapujá Lake, 3°12'54"S, 52°11'28"W, Xingu River Basin, in front of Altamira, Pará State, 21 October 1997, Jansen Zuanon col. Paratypes. Ten males and ten females, entire, alcohol + glycerine (MZUSP30605), one male and one female dissected and mounted on slides in glycerine (MZUSP30606), Arapujá Lake, Xingu River, Altamira city, Pará State, 21 October 1997, Jansen Zuanon col. Additional material. Males, females and copepodids from Ressaca Lake, Tocantins River Basin, 5°11'36"S, 49°15'45"W, June 1983, Pedro Mera col.

Etymology.

Named in honour of Dr. Edinaldo Nelson dos Santos Silva (Instituto Nacional de Pesquisas da Amazônia, INPA, Manaus, Brazil), for his invaluable contributions to taxonomy and ecology of the Diaptomidae .

Diagnosis.

Male (Figures 2B, 10A). Length excluding caudal setae (mean ± SD of ten specimens: 907 ± 60 µm from Ressaca Lake; 859 ± 18 µm from Arapujá Lake). Transverse, narrow nuchal organ ahead cephalic suture, with pair of small sensilla internally and another larger pair of sensilla adjacent to suture (Figure 2B). Rows of fine dorsal spinules along posterior margins of Th2 to Th6 (Figure 2B). Pair of lateral wings symmetrical, with curved row of spinules on each wing. First segment of left A1 with patch of spinules. Segment 13 of right geniculate antennule produced into well-developed, spinous process. Segments 15 and 16 with small process each. Pair of P5 asymmetrical, both with rudimentary, unarmed praecoxae and coxae bearing posterior conical process projecting over basis. Right P5 bearing outgrowth on posterior basal surface with deep oblique groove with minute tubercles along edge; semicircular lamella on inner margin of basis covered with fine setae; exopod 2-segmented, exp-1 with posterior distal margin produced into pair of conical outgrowths ending as blunt tip; Exp-2 with lateral outer spine basally placed at the distal third and terminal claw strong and curved in two planes. Right P5 endopod one-segmented partially fused to the basis, anteriorly.

Female (Figure 2A). Length excluding caudal setae (mean of ten specimens: 1,063 ± 35 µm from Ressaca Lake; 933 ± 31 µm from Arapujá Lake). Rows of dorsal spinules along posterior margins of Th2 to Th6 (Figure 2A, C). Posterolateral wings of Th5 asymmetrical; left wing produced into a semicircular expansion with sensilla at tip. GS slightly asymmetrical. Left spiniform sensilla with bifid apex (Figure 2A, C). P5 with fused intercoxal plate, making legs be closely placed. Dorsal expansions of coxa symmetrical and less than ¼ of segment; strong spiniform sensilla at apex of expansions. Lateral seta of basis reaching from half and 2/3 of length of Exp1; Exp three-segmented, Exp 1 unarmed, Exp2 with stout inner process bearing short setules and outer small spine, not fused to segment. Exp3 reduced, with two unequal spines, the outer smallest and reaching more than 1/2 length of inner spine. Enp one-segmented, with no sutures; length reaching 2/3 of Exp1 at least (Figure 9D, E).

Description - male

(Figure 2B). Length of holotype, excluding caudal setae, 1,075 µm.

Prosome . Male shorter than female. Maximum width of prosome (275 µm) at Th1. Rostrum asymmetrical (Figure 8E). Cephalosome with nuchal organ just anterior to suture level; two pairs of sensilla next to lateral borders. Prosome 5-segmented. Th5 and Th6 fused, with suture line represented by rows of spinules (Fig. 2B). Lateral wings little developed, each with small spiniform sensilla at apex, similar in size and shape to spinules composing a dorsal row (Figure 2B).

Urosome (Figures 2B, 10A). Consisting of four somites plus anal segment, genital somite asymmetrical, with left genital aperture at the middle portion; pair of sensilla at similar regions on both sides of the segment. Ur1 to 3 longer than wide, with small pores laterally; small anal operculum at Ur4.

Caudal rami (Figure 2B). Symmetrical, longer than wide, with six plumose setae at posterior portion; innermost setae slender and smooth; two dorsal sensilla and setules along inner margin.

Antennules (Figures 3A, B, 4 A–C). Asymmetrical, extending beyond prosome but not extending past the distal portion of the Ur3. Ancestral segments II–IV, XXI–XXIII, XXIV–XXV and XXVII–XXVIII completely fused. Tip of setae on segments 3 (V), 7 (IX), 9 (XI) and 14 (XVI) blunt.

Right antennule (Figures 3A, 4 A–C). Composed by 22 segments; fusion pattern and armature presented in Table 1. Sensilla present at segments 2 (III), 3 (V), and 5 (VII). Conical seta of segment 8 (X) longer and more robust than the one at segment 12 (XIV). Modified seta on segment 10 1/3 smaller than modified seta on segment 11. Seta-like aesthetasc present at segments 17 and 18 (XIX, XX). Tips of large setae on segments 3, 7, 9 and 14 blunt. Segment 19 with one very long and one short setae. Modified seta forming strong process on segment 13. Segments 15 and 16 with small spinous process.

Left antennule (Figure 3B). 25-segmented; armature of segments presented in Table 1. Tips of large setae on segments 3, 7, 9 and 14 blunt, as in right antennule. Seta inserted ventrally on segment 24 (XXVI).

Antenna (Figure 5A). Biramous; coxa presenting one inner seta. Basis with two setae inserted posteriorly. Exopod 8-segmented; second ( II–IV) and penultimate ( IX–X) segments compounded with regions of discontinuous cuticle surface; penultimate segment elongated; distal segment small, with three long, apical setae. Endopod 2-segmented; outer margin of first segment ornamented with one patch of spinules (approx. 15); inner margin with two setae and pore between patch of spinules and setae; second segment bilobed, with groove between lobes; outer lobe with seven (eight visible on Fig. 5A) marginal setae and one group of spinules on dorsal/outer margin; inner lobe with eight distal setae.

Mandible (Figure 5B, C, D). Gnathobase strongly sclerotized; gnathal blade with six multicuspid teeth and distal sub-triangular tooth. Basis with inner seta. Mandibu lar palp biramous. Basis of the palp with four inner setae (three distal). Exp with four segments, setal formula 1, 1, 1, 3. Enp 2-segmented; first segment with distal lobe bearing four setae; second segment with nine distal setae and three rows of spinules on posterior margin.

Maxillule (Figures 6B, 7A). Coxal epipodite with nine setae and row of spinules on distal surface. Coxal endite with four distal setae. Outer seta representing basal exite present; four setae on proximal basal endite, distal basal endite with four setae. Endo pod two-segmented; with three setae on margin of proximal segment, and five distal setae on second segment. Exopod with six distal setae.

Maxilla (Figure 6A). Proximal praecoxal endite with five setae and one spine (setules present on these setae but not figured here); distal praecoxal endite with three setae: proximal and distal coxal endites each with three setae; allobasis with four setae; free endopod with five setae in total.

Maxilliped (Figures 6C, D). First syncoxal endite represented by one seta with row of spinules at base; second to fourth syncoxal endites from proximal to distal with 2, 3, 3 setae, distal angle of syncoxa extended into lobe with row of small spinules; basis with three setae, double row of setules proximally; endopod six-segmented, with 2, 3, 2, 2, 1+1, 4 setae.

P1 (Figure 7A). Coxa with inner seta inserted distally, adjacent to a small round expansion ornamented with setules; outer margin bearing one patch of setules and one line of spinules. Basis with setules line at outer margin. Exp 3-segmented; setules along inner margin of the first segment, and outer margin of the second and third segments. Exp-3 spine with serrate margin at external side, and internal surface of Exp-3 without line of spinules. Enp 2-segmented; setules present along all outer margins.

P2 (Figures 7 B–D, 8B, C). Coxa with inner seta inserted distally. Posterior surface ornamented with a patch of spinules. Basis with no setal element or ornaments. Exp 3-segmented, with one outer spine each; setules along inner margin of the first, inner and outer of the second segment. Anterior surface of Exp-3 with distal row of spinules. Enp 3-segmented. Schmeil’s organ present on posterior surface of segment 2. Setules along outer margin of all segments. Enp-3 anterior surface with two distal rows of spinules.

P3 (Figure 7E, F, G). Coxa with inner seta inserted distally. Posterior surface ornamented with small spinules patch. Basis with no setal element or ornaments. Exp with setules along inner margin of the first and second segments. Anterior surface of Enp-3 with one line of spinules at distal part. Remaining characters like P2.

P4 (Figures 7 H–J, 8D). Coxa with inner seta inserted distally. Posterior surface ornamented with small patch of spinules. Basis with one seta inserted at the posterior/outer margin. Exp without setules along inner or outer margins. Anterior surface of Exp-3 and Enp-3 with one and two lines of spinules at distal part, respectively. Armature formula of all legs represented in Table 2.

P5 (Figures 9 A–C, 10). P5 asymmetrical and biramous; rudimentary praecoxa present; intercoxal plate (coupler) longer than wide.

Right P5 (Figures 9 A–C, 10A). Coxa with conical process projecting over basis with spiniform sensilla acute at tip (Figure 7C). Basis with lateral seta inserted at distal part. Outgrowth on posterior basal surface with deep oblique groove ornamented with minute tubercles along edge, Enp one-segmented, as endopodal lobe with comb of spinules on inner anterior surface. Exopod2-segmented; first segment with acute sclerotized outgrowth on distal margin, posteriorly; second segment with curved ridge on posterior surface, lateral spine on distal third of segment; terminal claw strong and curved proximally, with row of spinules along inner margin. Endopodal lobe with comb of spinules on inner anterior surface.

Left P5 (Figures 9 A–C, 10). Well developed, reaching distal margin of right Exp-1. Coxa with conical process projecting over basis with spiniform sensilla at tip, very similar to the one at right. Basis with seta on outer margin; inner margin slightly curved; Exopod bisegmented. Exp-1with convex outer margin; inner margin with rounded process bearing setules. Exp-2 with semicircular process bearing setules proximally on inner margin, inner small spine and apical spiny process.

Description - female

(Figure 2A). Length, excluding caudal setae 1,670 µm. Maximum width at distal margin of the Th1, with 510 µm. Body larger than male. Prosome . Rostrum symmetrical, with paired filaments, right broader in mid part than left. Prosome with incomplete dorsal suture separating Th5 and Th6, suture marked by spinules dorsally and laterally. Posterolateral wings of Th6 small and slightly asymmetrical; left wing slightly larger than right and with semicircular shaped protrusion on distal margin; right wing elongate; both lateral wings with spiniform sensilla (Figure 2A, C).

Urosome (Figure 2A, C). Ur3-segmented; GS inflated anteriorly and nearly symmetrical, longer than all the other somites combined; anal segment with weakly de veloped operculum; caudal rami symmetrical with setules along inner margin; genital area, located centrally with prominent lateral processes on opercular pad.

A1. Symmetrical, 25-segmented; similar to left A1 of male (Figure 3B); extending beyond half of the GS.

P5 (Figure 9D, E). Symmetrical, coxa with conical process with sensilla at tip, basis subtriangular with long seta reaching beyond half of Exp-1 and bearing a small row of setules on anterior surface (Figure 9E). Exp-1 larger than second, Exp2 with stout terminal claw with denticles along lateral margins bearing short setules and outer small spine, not fused to segment. Exp-3 with two terminal setae, lateral smaller; enp 1-segmented with two setae and oblique comb of spines sub terminally on anterior surface. Number of armature elements as in Table 2.