Chalarosthrix bisetosa Gómez & Nazari 2022, sp. nov.
Creators: name: Gómez, Samuel
name: Nazari, Fatemeh
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Hexanauplia
Harpacticoida
Cletodidae
Chalarosthrix
Chalarosthrix bisetosa

description: Chalarosthrix bisetosa sp. nov.
(Figs. 1–6)
urn:lsid:zoobank.org:act: E104BC81-3793-4BD3-A42A-D5737DCE25E3
Type locality. Urías estuary, Mazatlán, Sinaloa State, Mexico (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 pp. 43, figure 1).
Material examined. Female holotype dissected and mounted onto nine slides (ICML-EMUCOP-180119-180); 18 Jan 2019. S. Gómez leg.
Description. Female. Total body length 625 µm measured from anterior tip of rostrum to posterior margin of caudal rami.
Habitus (Fig. 1A, C) semi-cylindrical, without clear demarcation between prosome and urosome. Rostrum (Fig. 1A, C) well-developed, fused to cephalothorax, with pointed tip recurved upwards, with two subdistal sensilla.
Prosome (Fig. 1A, C) consisting of cephalothorax with P1-bearing somite incorporated, and three free-pedigerous somites bearing P2–P4. Cephalothorax with dorsolateral surface sensilla as shown; postero-dorsal small chitinous extension with four sensillum-bearing socles; additionally, with one dorsolateral sensillum-bearing socle on each side. P2- and P3-bearing somites with four postero-dorsal sensilla, one dorsolateral and one lateral sensillum-bearing socle on each side, and with two lateral sensilla; with one dorsolateral tube pore on each side, but P3- bearing somite with additional medial tube pore dorsally; with lateral row of posterior slender spinules on each side. P4-bearing somite as previous somite but with two posterodorsal sensilla only.
Urosome (Figs. 1A, C, 2A) comprising fifth pedigerous somite, genital double-somite, two free abdominal somites, and anal somite. P5-bearing somite as in previous somite but with only one dorsolateral sensillum-bearing socle on each side. Second (genital somite) and third urosomites completely fused, original division indicated by lateroventral internal rib; both halves with two dorsal sensilla, and one dorsolateral and one lateral sensillum-bearing socle, of which each dorsolateral socle with one tube pore and lateral socle with row of spinules; posterior half with two dorsal pores and dorsolateral row of slender spinules along posterior margin; ventral surface of anterior half with P6, genital field and two tube pores as shown, posterior half with two tube pores, and two sensilla and row of slender spinules along posterior margin. Fourth urosomite as previous somite but dorsolateral socles less developed; ventrally with two sensilla and posterior spinules as shown. Fifth urosomite without socles or sensilla, with spinular ornamentation as in previous somite. Anal somite (Figs. 1A–D, 2A) with ventral cleft medially; with lateral, dorsal and ventral tube pores as shown; with posterior spinules close to caudal rami and on posterior margin of ventral cleft; anal operculum semicircular, posterior margin with row of minute spinules. Caudal rami slightly divergent, elongate, about 5x as long as wide (maximum width measured at proximal part); with seven setae as follows: lateral seta I in proximal third, very small; seta II 3x as long as seta I, issuing close to joint with anal somite, somewhat displaced dorsally; seta III lateral, posterior to seta I and as long as seta II; seta IV shorter than seta III, fused basally to seta V, the latter longest and sparsely pinnate; seta VI issuing at inner distal corner, as long as seta III; dorsal seta VII triarticulated, arising in the middle of ramus, somewhat displaced inwards.
Antennule (Fig. 3A) five-segmented; all segments smooth except for two spinular rows on first one; all setae smooth except for one and three setulose setae on first and second segments, respectively, and for two strong thick spinulose elements on last segment. Armature formula as follows: 1[1], 2[7], 3[6+(1+ae)], 4[1], 5[9+acrothek]; acrothek of last segment consisting of two slender setae fused basally to aesthetasc.
Antenna (Fig. 3B) with allobasis armed with two abexopodal setae (one proximal, one medial), with outer remainder of original division between basis and first endopodal segment. Free endopodal segment as long as allobasis, with proximal and subdistal strong outer spinules and two subdistal inner frills; with two inner lateral spines, distally with three spines one of which bipinnate, one single geniculate seta, and one geniculate element fused basally to small slender seta. Exopod one-segmented, ornamented with few subdistal spinules, armed with one lateral and two distal setae as shown.
Mandible (Fig. 4A) with well-developed coxa ornamented with short spinular row; gnathobase well-developed; distally with seven spines as depicted, and one long ventral element. Palp one-segmented, with two lateral and three apical setae.
Maxillule (Fig. 4B) with praecoxal arthrite armed with two surface setae one of which displaced subdistally, and five distal spines. Coxal endite with one seta. Basis with two endites, distal endite with three, proximal endite with two setae. Exopod and endopod fused to basis, the former represented by two, the latter by one seta.
Maxilla (Fig. 4C) with syncoxa ornamented with small proximal inner and outer subdistal spinules; with two endites, each with one spinulose and one slender seta. Allobasis drawn out into claw, the latter with one posterior and one anterior accompanying seta. Endopod completely incorporated to basis, represented by two setae.
Maxilliped (4D) subchelate. Syncoxa ornamented with few subdistal outer spinules, unarmed. Endopod one segmented, with long claw accompanied by long slender seta.
P1 (Fig. 5A) with elongate bare intercoxal sclerite. Praecoxa triangular, unornamented. Coxa rectangular, with few subdistal outer spinules. Basis with spinules at base of outer and inner setae and at base of endopod; outer seta setulose, inner spine strongly spinulose. Exopod three-segmented; segments subequal in length and ornamented with long outer spinules as shown; first and second segments without inner armature, outer spines very long; third segment without inner armature, with two outer spines (proximal visibly shorter that subdistal), and two distal setae without setulose distal tufts (distal inner shorter than distal outer, longer than subdistal outer spine, not inclined outwardly, and not intersecting base of distal outer element). Endopod two-segmented, reaching proximal third of EXP3; first segment about one third the length of second segment, with inner and outer spinules as shown, unarmed; second segment elongate, about 4x as long as wide, with inner and outer spinules as depicted, with two distal elements (one inner distal seta and one outer distal spine).
P2–P4 (Figs. 5B, 6A, B) with elongate bare intercoxal sclerites. Praecoxa triangular; with transverse row of small spinules. Coxa with inner and outer short spinular rows, of P2 with two, of P3 with one, of P4 without medial minute spinules. Basis with outer long plumose seta, with spinules at base of outer seta and at base of endopod. Exopod three-segmented; segments with outer spinules as shown, EXP1 and EXP2 with inner distal frill, without inner armature, outer spines elongate; P2 EXP3 with four (two apical setae, and two outer spines), P3–P4 EXP3 with five elements (one inner and two apical setae, and two outer spines). Endopod two-segmented; segments ornamented with spinules as shown; first segment small, unarmed; second segment elongate, of P2 with two apical setae, of P3 and P4 with two apical setae and one outer spine.
P1–P4 armature formulae as follows:
P5 (Fig. 2B) with baseoendopod and exopod distinct, elongate and narrow, ornamented with spinules as depicted. Baseoendopod with outer seta arising from long setophore; endopodal lobe with two inner (one medial, one subdistal) and one distal seta, and with one medial tube pore subdistally. Exopod with two outer (one medial, one subdistal) and one distal seta, and one proximal tube pore.
Genital field (Fig. 2B) with median copulatory pore; each P6 represented by one small seta.
Male. Unknown.
Variability. No variability was observed in the only female inspected.
Etymology. The specific epithet comes from the Latin sufix bi, two, and from the Latin adjective sētōsa, setaceous, and refers to the presence of two setae only on the P1 ENP2. It is in the nominative singular, gender feminine.
description: Published as part of Gómez, Samuel & Nazari, Fatemeh, 2022, Chalarosthrix gen. nov., a new taxon of the Sphingothrix-Triathrix clade (Harpacticoida: Cletodidae) from the Province of Cortez, Eastern Mexican Pacific, pp. 410-428 in Zootaxa 5116 (3) on pages 418-425, DOI: 10.11646/zootaxa.5116.3.6, http://zenodo.org/record/6372244