Arktourella margarethae, Gómez & Nazari, 2021

Gómez, Samuel & Nazari, Fatemeh, 2021, Proposal of Arktourella gen. nov., a new genus of the family Normanellidae Lang 1944 (Copepoda: Harpacticoida) from the Province of Cortez, Zootaxa 5057 (1), pp. 29-51: 37-46

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Arktourella margarethae

gen. et sp. nov.

Arktourella margarethae   gen. et sp. nov.

( Figs. 1-8 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 View FIGURE 8 )

Type locality. Urías estuary, Mazatlán , Sinaloa State, stn. 4 (23.1840°N, 106.3579°W; depth 0.7 m, organic carbon content 1.13%, organic matter content 1.94%, sand 82.44%, clay 8.27%, silt 9.29%.) (see also Gómez (2020: 43, figure 1). GoogleMaps  

Other localities. Urías estuary, Mazatlán   GoogleMaps , Sinaloa State, stn. 9 (23.1904°N, 106.4121°W; depth 5.4 m, organic carbon content 1.41%, organic matter content 2.43%, sand 64.81%, clay 8.09%, silt 27.11%.), stn. 10 (23.1815°N, 106.4214°W; depth 6.0 m, organic carbon content 1.2%, organic matter content 2.07%, sand 69.12%, clay 7.91%, silt 22.97%.) (see also Gómez (2020: 43, figure 1).

Material examined. From the type locality: female holotype dissected (ICML-EMUCOP-180119-192), male allotype partially dissected (both antennules dissected, the rest left intact and preserved in alcohol) (ICML-EMUCOP- 180119-195), one male paratype (ICML-EMUCOP-180119-193) and one CV female paratype (ICML-EMUCOP- 180119-194) preserved in alcohol. From other localities: one female paratype (ICML-EMUCOP-180119-197) and one male paratype (ICML-EMUCOP-180119-196) from stn. 9 and 10, respectively. 18 Jan. 2019. S. Gómez leg.

Description of the female. Total body length ranging from 410 µm to 465 µm (n= 2; holotype, 465 µm) measured from anterior tip of rostrum to posterior margin of caudal rami.

Habitus ( Fig. 1A, C View FIGURE 1 ) semi-cylindrical, without clear demarcation between prosome and urosome.

Prosome ( Fig. 1A, C View FIGURE 1 ) consisting of cephalothorax, P1-bearing somite fully incorporated to the latter, and three free-pedigerous somites bearing P2–P4. Rostrum ( Figs. 1A, C View FIGURE 1 , 3A View FIGURE 3 ) well-developed, discrete, triangular, with wide base and pointed tip recurved upwards, reaching tip of second antennulary segment, covered with minute denticles and with two subdistal sensilla. Cephalothorax covered with minute denticles, with surface sensilla, pores, and with areolated surface pattern as shown, posterior margin serrated, lateral margin plain. P2–P4-bearing somites covered with minute denticles, with pores and tube-pores, and posterior sensilla as shown; posterior margin serrated, of P4- bearing somite comparatively coarser.

Urosome ( Figs. 1A–D View FIGURE 1 , 2A View FIGURE 2 ) comprising fifth pedigerous somite, genital double-somite, two free abdominal somites, and anal somite, all of which with minute surface denticles dorsally and laterally. P5-bearing somite largely as in previous somite. Second (genital somite) and third urosomites separated dorsolaterally but fully fused ventrally forming genital double-somite; both halves with tube-pores and posterior sensilla as shown, with posterior margin coarsely serrated; ventral surface of anterior half —genital somite— with P6, and one patch of small spinules close to lateral margin and one outer distal pointed projection on each side; each side of ventral surface of posterior half —third urosomite— with patch of small spinules at the base of outer distal projection, and short row of long slender spinules between pair of sensilla as depicted, medially with transverse row of small spinules between innermost pair of sensilla. Fourth urosomite largely as posterior half of genital double-somite dorsally and laterally; ventrally with additional pair of tube-pores and pattern of four crescentic sets of spinules between innermost pair of sensilla. Fifth urosomite largely as previous somite but without medial tube-pore dorsally, without sensilla; ventrally without tubepores or sensilla, with pattern of surface minute spinules on posterior half, and with pattern of long posterior spinules as shown. Anal somite slightly wider than long; with one dorsolateral tube-pore on each side; with well-developed semicircular anal operculum ornamented with small denticles on surface and along posterior margin giving a serrated appearance and flanked by pair of sensilla; ventrally cleft medially, with pair of tube-pores medially and subdistally close to joint with caudal rami, with inner small spinules along inner margin of medial cleft and larger ones close to joint of caudal rami. Caudal rami twice as long as wide; dorsally with inner row of small spinules medially and at base of seta III, and with subdistal tube-pore; ventrally with comparatively longer spinules along posterior margin, and with two tube-pores as shown; with seven setae as follows: setae I and II aligned, issuing midway lateral margin, the former ventral to and about half as long as the latter; seta III displaced ventrally, slightly posterior to setae I and II, visibly longer than the latter; seta IV about half the length of seta V, slightly longer than supporting ramus; seta V nearly as long as anal somite and caudal ramus combined, posterior half rat-tail-like; seta VI issuing at inner distal corner, as long as seta II; dorsal seta VII triarticulated, as long as seta III.

Antennule ( Fig. 3A View FIGURE 3 ) five-segmented; all segments smooth except for spinular row on first segment; all setae smooth except for one and three bipinnate setae on first and second segments, respectively, for one unipinnate strong element on third and fourth segments, and one unipinnate strong seta and one bipinnate distal element, the latter fused basally to slender seta and to short aesthetasc. Armature formula as follows: 1[1], 2[8], 3[7+(1+ae)], 4[3], 5[7+(2+ae)].

Antenna ( Fig. 3B View FIGURE 3 ) with small coxa furnished with few outer spinules. Allobasis with short row of spinules proximally, armed with one abexopodal seta, with outer and inner remainder of original division between basis and first endopodal segment. Free endopodal segment as long as allobasis, with outer spinules and two subdistal inner frills; with two inner lateral spines, distally with two inner spines, two medial geniculate setae, and one outer spinulose element fused basally to outer small seta. Exopod one-segmented, armed with four setae —two lateral and two distal.

Mandible ( Fig. 4A View FIGURE 4 ) with well-developed coxa; gnathobase well-developed, with two bicuspidate teeth, set of four spines, and one long ventral unipinnate seta. Palp biramous. Basis with spinules proximally and at base of endopod, with two strong bipinnate setae. Endopod one-segmented, with one lateral and three distal elements. Exopod one-segmented, elongate, with slender long outer spinules and armed with one distal seta.

Maxillule ( Fig. 4B View FIGURE 4 ) with robust praecoxa ornamented with spinules proximally and at base of coxal endite; arthrite with short rows of surface spinules as shown, with one surface seta, seven distal elements —five strong and two thinner spines—, and one lateral element. Coxal endite with two setae. Basis with few spinules distally, with two endites of which distal with three, proximal with two setae. Endopod fully incorporated to basis and represented by two setae. Exopod one-segmented, with two setae.

Maxilla ( Fig. 4C View FIGURE 4 ) with syncoxa ornamented with small proximal inner, outer small subdistal, and outer medial long slender spinules; with three endites of which proximal with one, medial with two, distal with three elements. Allobasis drawn out into claw accompanied by one posterior and one anterior accompanying seta, additionally with strong proximal claw. Endopod completely incorporated to basis, represented by three setae.

Maxilliped ( Fig. 4D View FIGURE 4 ) subchelate. Syncoxa unornamented, with two distal setae. Basis with longitudinal row of small spinules, and with few subdistal outer spinules, unarmed. Endopod one-segmented, with long claw accompanied by short seta.

P1 ( Fig. 5A View FIGURE 5 ) with elongate bare intercoxal sclerite, the latter with distal outer short extension on each side. Praecoxa triangular, with distal row of spinules. Coxa rectangular, with one medial transverse and one outer longitudinal row of anterior spinules, and with one outer longitudinal row of posterior spinules. Basis largely triangular, with one proximal pore, with long slender outer spinules proximally, with stronger shorter ones at the base of inner and outer spines, and with longer spinules between rami. Exopod situated at a lower level than the endopod and reaching proximal third of first endopodal segment, three-segmented; segments subequal in length, spinular ornamentation as shown; first segment without, second segment with inner seta, third segment with four elements —two outer spines, and two distal geniculate setae of which innermost displaced to inner margin. Endopod two-segmented; first segment elongate, about five times as long as wide —widest part measured proximally— with inner slender and outer strong spinules longitudinally, with one subdistal inner seta; second segment short, three times as long as wide and 0.25 times as long as first segment, with one inner short seta, and two distal elements —one distal inner geniculate seta and one distal outer unipinnate spine.

P2–P4 ( Figs. 5B View FIGURE 5 , 6A, B View FIGURE 6 ) with elongate smooth intercoxal sclerites, the latter with distal outer extension on each side, U-shaped; of P2 thickest, of P4 slenderest. Praecoxa triangular, with transverse row of medial spinules distally. Coxa rectangular, with anterior and posterior spinules as shown. Basis trapezoid; of P2 and P3 with spinules medially, at base of outer element, and between rami, of P4 with spinules at the base of outer element and between rami, and P2 and P4 seemingly without, of P3 with long slender inner spinules; outer element of P2 a unipinnate spine, of P3 and P4 a slender naked seta. Exopods three-segmented; first and third segments subequal in length, second segment shortest; first and second segments with, third segment without inner distal frill; spinular ornamentation of segments as shown; first segment without, second segment with inner well-developed seta; third segment with two outer spines, two distal setae, and one (P2), and two (P3 and P4) inner setae of which proximal inner seta of P4 EXP3 visibly thicker. Endopods two-segmented, of P2 and P3 reaching slightly beyond, of P4 reaching middle of EXP2; first segment shorter than second one, of P2 and P3 with long slender inner spinules and comparatively stronger outer ones, of P4 with long slender inner spinules only, with one inner seta; second segment with outer spinules as shown, with one outer subdistal and two distal elements —outermost of which at a lower level—, and three (P2 and P3) and two (P4) inner setae.

P1–P4 armature formulae as follows:

P5 ( Fig. 2B View FIGURE 2 ) with baseoendopod and exopod distinct, elongate and narrow, ornamented with spinules as depicted. Baseoendopod with outer seta arising from setophore; endopodal lobe with tube-pore close to exopod, with two inner —one medial, one subdistal—, two distal, and one outer seta. Exopod with three outer setae of which proximal very short, and three distal setae.

Genital field ( Fig. 2A View FIGURE 2 ) with median copulatory pore on first half of genital double-somite; each P6 represented by one bipinnate seta.

Description of the male. Total body length ranging from 330 µm to 360 µm (mean= 341.6 µm, n= 3; allotype, 360 µm) measured from anterior tip of rostrum to posterior margin of caudal rami. Habitus (not shown) as in female. Sexual dimorphism expressed in separated genital somite and third urosomite, antennule, P2 and P3 ENP, P5 and P6.

Antennule ( Fig. 7A, B View FIGURE 7 ) subchirocer, seven-segmented, with geniculation between fourth and fifth, and fifth and sixth segments, with two segments distal to second geniculation. Armature formula difficult to define, most probably as follows: 1[1], 2[11], 3[6], 4[2], 5[7+(1+ae)], 6[1], 7[5+ (1+ae)].

Mandible, maxillule, maxilla and maxilliped (not shown) as in female.

P1 (not shown) as in female.

P2 EXP (not shown) as in female; ENP ( Fig. 7C View FIGURE 7 ) as in female except for comparatively shorter inner seta of ENP1, and comparatively shorter distal, subdistal outer and outer setae of ENP2.

P3 EXP (not shown) as in female; ENP ( Fig. 8A View FIGURE 8 ) as in female except for comparatively shorter inner seta of ENP1, comparatively shorter distal inner and outer seta of ENP2, and for outer apophysis of ENP2.

P4 (not shown) as in female.

P5 ( Fig. 8B View FIGURE 8 ) with baseoendopod and exopod distinct; both baseoendopods fused medially; outer seta arising from setophore. Endopodal lobe reaching proximal third of exopod, with two setae. Exopod elongate, about three times as long as wide, with two outer setae —one medial, one subdistal—, and two distal setae of which innermost displaced to inner margin.

P6 ( Fig. 8B View FIGURE 8 ) asymmetrical, only one leg functional, the other fused to somite; each leg with three setae.

Variability. No variability was detected in the specimens inspected.

Etymology. The species is named after the senior author’s godmother Margarita Noguera Farfán for her 73 rd birthday. The binomen is for the 49 th wedding anniversary of the senior author’s godfather Arturo Villanueva Robertson with the senior author’s godmother Margarita Noguera Farfán. It is a noun in the genitive case, gender feminine.