Notodiaptomus cannarensis, Alonso, Miguel, Santos-Silva, Edinaldo N. dos & Jaume, Damia, 2017

Alonso, Miguel, Santos-Silva, Edinaldo N. dos & Jaume, Damia, 2017, A new species of Notodiaptomus from the Ecuadorian Andes (Copepoda, Calanoida, Diaptomidae), ZooKeys 697, pp. 59-71 : 59

Notodiaptomus cannarensis sp. n. Figs 1, 2, 3, 4, 5

Material examined.

Mazar reservoir (River Paute, Cañar Province, southern Ecuador). Coordinates 2°35 ’53.08” S; 78°37 ’32.16” W. Altitude: 2127 m a.s.l. Holotype: male 1.2 mm long, preserved in formalin vial. Paratypes: Ten males and ten females, preserved in formalin vial. Holotype and paratypes registered under same registration number [MECN-SI-Cal-0001]. Collected by Verónica Ordóñez, April 2013.

Diagnosis.

Female urosome reduced to only two somites due to incorporation of abdominal somites III and IV into composite genital double-somite; resulting composite somite with symmetrical, hypertrophied wing-like (in dorsal aspect) extensions at each side. Male right fifth leg with outer spine of second exopodal segment recurved and implanted proximally on margin.

Etymology.

Species name refers to the Ecuadorian province where it was found ( Cañar Province; southern Ecuador).

Distribution.

Known only from Mazar reservoir, located on the River Paute (Amazon Basin, Cañar Province, southern Ecuador), 2127 m a.s.l.

Description of adult female.

Body up to 1.4 mm long. Prosome 5-segmented, comprising cephalosome plus first to third free pedigerous somites, and partially-fused fourth and fifth pedigerous somites (Fig. 1 B–D); epimeral plates of latter extended backwards and displaying two pointed processes at each side, oriented as figured. Rostrum (Fig. 1A) bifid, with paired short rostral filaments. Urosome (Fig. 1 B–D) 2-segmented, with genital somite incorporating all abdominal somites except anal somite; resulting composite genital somite displaying pair of hypertrophied ventrolateral ovoid swellings extended backwards, each with pointed tip. Genital field not fully resolved, with paired gonoporal plates placed medially on ventral surface of composite genital somite, partially covered with short genital operculum (Fig. 1E). Caudal rami symmetrical, slightly longer than broad with setulose margins; caudal setae symmetrical, short, all plumose except dorsal seta, simple and more slender than rest; anterolateral accessory seta absent.

Antennules (Fig. 1F, G) symmetrical, each 25-segmented, with fusions affecting ancestral segments II-IV and XXVII-XXVIII; segmentation pattern and armature formula as follows: segment 1 (corresponding to ancestral segment I), 1 seta + aesthetasc; segment 2 (fused ancestral segments II-IV), 3 setae + aesthetasc; segment 3 (V), 1 seta + ae; segment 4 (VI); 1 seta; segment 5 (VII), 1 seta + ae; segment 6 (VIII), 1 seta; segment 7 (IX), 1 seta + ae; segment 8 (X), 2 setae, of which distal most reduced; segment 9 (XI), 2 setae + ae; segments 10 (XII) and 11 (XIII), 1 seta each; segment 12 (XIV), 2 setae + ae, with distal seta reduced; segment 13 (XV), 1 seta; segment 14 (XVI), 1 seta + ae; segment 15 (XVII), 1 seta; segment 16 (XVIII), 1 seta+ ae; segments 17 (XIX) and 18 (XX), 1 seta each; segment 19 (XXI), 1 seta+ ae; segments 20 (XXII) and 21 (XXIII), 1 seta each; segments 22 (XXIV) to 24 (XXVI), 1 + 1 setae each; segment 25 (fused XXVII-XXVIII), 5 setae + ae. Sensilla present on anterodorsal surface of segments 2, 3, 5 and 6.

Antenna (Fig. 2D, E) biramous. Coxa with one seta on medial margin. Basis with two setae on distomedial margin. Exopod 8-segmented, setal formula 1, 3, 1, 1, 1, 1, 1, 3. Endopod 2-segmented with compound second segment bilobed; setal formula 2, 7+6 (see Fig. 2E).

Labrum (Fig. 1A) with concave distal margin. Paragnaths (Fig. 1A) globose, each with two rows of setae as figured.

Mandible coxal gnathobase (Fig. 3A) cutting edge 9-denticulate and with simple distal seta; innermost denticle broadly separated from rest. Palp (Fig. 3B) biramous, basis with four medial setae; exopod 5-segmented, setal formula 1, 1, 1, 1, 2; endopod 2-segmented, distal segment bilobed, with row of setules along outer margin and transverse row of setules about midway, setal formula 4, 5+5.

Maxillule (Fig. 3C) praecoxal arthrite with 15 armature elements ornamented and distributed as figured. Coxal epipodite with nine setae; coxal endite with four setae. Basal exite seta present; basal endites each with four setae. Exopod with six setae. Endopod 2-segmented, setal formula 4, 5.

Maxilla (Fig. 3D) syncoxal endites armature formula: 5 + reduced spine, 3, 3, 3. Allobasis basal endite with three setae; allobasis endopodal endite with single seta. Free endopod 3-segmented, setal formula 1, 1, 3.

Maxilliped (Fig. 3E) praecoxal endite with single seta. Coxal endites with 2, 3, and 4 setae, respectively; distal endite with spinulose swelling. Basis with three medial setae. Endopod 6-segmented, armature formula 2, 3, 2, 2, 1+1, 4.

Swimming legs 1-4 (Fig. 4) each biramous with 3-segmented rami except for 2-segmented endopod on leg 1 (Fig. 4A). Second endopodal segment of leg 2 with smooth rounded swelling ( “Schmeil’s organ") on posterior surface (Fig. 4B). Outer exopodal spines reduced in all limbs. Armature formula as follows:

Fifth legs (Fig. 1H) symmetrical, biramous, coxa and basis separate, outer basal seta simple and implanted on socle. Exopod 3-segmented, proximal segment unarmed, longer than middle segment; distomedial angle of middle segment prolonged into stout spinous process fringed with short setules, distolateral angle with tiny smooth spinous process; distal segment reduced, with two unequal setae distally, innermost longer and setulose, but not as long as inner spinous process of middle segment–, outermost seta much shorter and smooth. Endopod unsegmented, subrectangular with three tiny spinous processes and transverse row of setules distally.

Description of male.

Body up to 1.22 mm long. Differing from female in fifth legs, modified right antennule, asymmetrical epimeral plates of composite last prosomal somite, and segmentation and asymmetry of urosome, including caudal rami. Thus, the extensions of the epimeral plates corresponding to the partially fused fourth and fifth pedigerous somites are directed laterally instead of backwards, with the pointed processes present on each side less marked than in the female (Fig. 5A, B). The urosome is 5-segmented, with the genital somite asymmetrical, slightly protruding on the right side; the third abdominal somite is also asymmetrical, showing a dorsolateral hump crowned with a tiny spine on the right side. In addition, the caudal rami are slightly asymmetrical and comparatively more elongated than in female, with proportionally longer caudal setae except for dorsal seta, that is shorter.

Right antennule (Fig. 2 A–C) 22-segmented, geniculate, with geniculation located between segments 18 (corresponding to ancestral segment XX) and 19 (corresponding to fused ancestral segments XXI-XXIII). Other fusions involving ancestral segments II-IV, XXIV-XXV and XXVII-XXVIII. Segmentation pattern and armature formula as follows: segment 1 (ancestral I), 1 seta + aesthetasc; segment 2 (II-IV), 3 setae + ae; segment 3 (V), 1 seta + ae; segment 4 (VI), 1 seta; segment 5 (VII), 1 seta + ae; segment 6 (VIII), 1 seta; segment 7 (IX), 1 seta + ae; segment 8 (X), 2 setae, of which distal reduced, conical; segment 9 (XI), 2 setae + ae; segments 10 (XII) and 11 (XIII), each with 1 stout truncate spiniform process + 1 seta; segment 12 (XIV), 2 setae + ae, with distal seta reduced, conical; segment 13 (XV), 1 stout truncate spiniform process plus seta; segment 14 (XVI), 2 setae + ae; segments 15 (XVII) and 16 (XVIII), each with 1 slender truncate spiniform process proximally and 1 seta + ae distally; segment 17 (XIX), 1 striated hyaline seta proximally + reduced truncate spiniform process distally; segment 18 (XX), 1 striated hyaline seta proximally plus tiny seta distally; segment 19 (XXI-XXIII), 2 striated hyaline setae plus short blunt seta midway of margin plus distal seta; segment 20 (XXIV-XXV), 2 + 2 setae; segment 21 (XVI), 1 + 1 setae; segment 22 (XVII-XXVIII), 5 setae + ae. Segments 13 to 18 swollen. Anterodorsal sensilla present on each segments 2, 3, 5 and 6.

Fifth leg (Fig. 5C) biramous, highly asymmetrical, each with coxa fused to intercoxal sclerite. Coxa and basis separate on both sides, each with tiny posterolateral seta implanted on socle. Right leg largest, basis with simple seta on posterolateral margin; Exopod 3-segmented, proximal segment with large rectangular lamella implanted on posterior surface (see Fig. 5B, C), second segment expanded and armed with recurved spine proximally on outer margin; distal segment of exopod modified as curved claw with inner margin finely serrated distally. Endopod (Fig. 5F) unsegmented, short -not surpassing distal margin of proximal exopodal segment–, subrectangular with tiny terminal spine on each side; distal margin of segment finely denticulate. Left leg (Fig. 5D, E) basis unarmed. Exopod 2-segmented, distal segment shortest, bifid with distal spine and subdistal conical robust seta, densely covered with short setules; proximal segment with micro-denticulate rounded outgrowth about midway of inner margin. Endopod unsegmented, implanted on produced distomedial angle of basis, with pointed tip wearing tiny spine subdistally at each side plus transverse row of setules in between as figured.