Pseudechinopsyllus andrei, George & Wandeness & Santos, 2025

George, Kai Horst, Wandeness, Adriane P. & Santos, Paulo J. P., 2025, A new species of Pseudechinopsyllus George, 2006 (Copepoda, Harpacticoida, Cletodidae) from Campos Basin, Brazil (southwest Atlantic Ocean), with remarks on the phylogeny of the genus, ZooKeys 1241, pp. 325-357 : 325-357

publication ID	https://doi.org/10.3897/zookeys.1241.153012
publication LSID	lsid:zoobank.org:pub:D538C646-9DF7-45C3-B50E-509A90A3073B
DOI	https://doi.org/10.5281/zenodo.15699528
persistent identifier	https://treatment.plazi.org/id/1DA1BC46-6426-5043-B1CF-AB9A215EBBE3
treatment provided by	ZooKeys by Pensoft
scientific name	Pseudechinopsyllus andrei
status	sp. nov.

Treatment

Pseudechinopsyllus andrei sp. nov.

Locus typicus.

Grussaí Canyon GoogleMaps , Campos Basin, Brazil, geographic position 21°55'S, 39°50'W, 1,300 m depth.

Type material.

Syntypes (ST) 1: female, put on 16 slides, MOUFPE collection no. 22056 / 1–16 GoogleMaps ; ST 2: female, put on 1 slide, MOUFPE collection no. 22057 GoogleMaps ; ST 3: female, put on 1 slide, MOUFPE collection no. 22058 GoogleMaps ; ST 4: male, put on 1 slide, MOUFPE collection no. 22059 GoogleMaps ; ST 5: male, put on 1 slide, MOUFPE collection no. 22060 GoogleMaps ; ST 6: female, put on 1 slide, MOUFPE collection no. 22061 GoogleMaps ; ST 7: female, put on 1 slide, MOUFPE collection no. 22062 GoogleMaps ; ST 8: female, put on 1 slide, MOUFPE collection no. 22063 GoogleMaps ; ST 9: female, put on 1 slide, MOUFPE collection no. 22064 (used for CLSM) GoogleMaps ; ST 10: male, put on 3 slides, MOUFPE collection no. 22065 / 1–3 GoogleMaps ; ST 11: copepodid CIV, put on 1 slide, MOUFPE collection no. 22066 GoogleMaps .

Note.

Because all representatives of the type material show damage to different parts of the body or appendages, the description was not based on one but on several individuals. The figure captions refer to the syntype on the basis of which an appendage or body section was drawn.

Description of female.

Habitus (Figs 2 A View Figure 2 , 3 A, B View Figure 3 ) long and slender, mean body length (R to end of FR) 1,255.9 µm (range 1,155.9 – 1,400.0 µm; n = 5). Cphth frontally with strongly developed peak, lacking FLH but bearing ACST, and four pairs of long tube pores. CLVPa (Figs 2 A View Figure 2 , 3 A, B View Figure 3 , 4 A View Figure 4 ) and CLVPp (Figs 2 A View Figure 2 , 3 A, B View Figure 3 ) well developed. Rostrum (exemplified in Fig. 5 A View Figure 5 ) small, constricted and almost squarish, apically with pair of sensilla, long tube pore, and RST; previous to the sensillar pedestals, with hyaline outgrowths. CLDP absent. Free thoracic somites bearing P 2 – P 5 laterally with TST 1 – TST 4 and long, unarmed DP 1 – DP 4 that carry sensilla at their tips; somites dorsally and dorsoventrally bearing long tube pores.

Females with last thoracic and first abdominal somite fused to GDS; former separation still indicated by dorsal suture; GST developed. GDS and remaining abdominal somites except telson also carrying dorsal and dorsoventral tube pores.

Abdominal somites with AST 1 – AST 3, whilst AST 4 are missing. Telson (Figs 2 A View Figure 2 , 3 A, B View Figure 3 , 4 B View Figure 4 ) at the most as large as the previous somite, laterally with two pairs of tube pores; anal operculum with dense row of fine long spinules on apical margin. FR (Fig. 4 C View Figure 4 ) reaching up to 1 / 3 of the body length, ~ 15 × longer than wide, with long tube pore ventrally, close to proximal margin.

Seven setae present: I and II standing closely together laterally in the middle of FR, III subapically at the outer margin. IV, V and VI terminally, being IV as long as III, VI smaller; V longest and bipinnate. VII biarticulated, inserting dorsally.

A 1 (Fig. 5 B View Figure 5 ) four-segmented, all segments covered with long slender spinules. First, third, and fourth segments of nearly the same length, second segment somewhat shorter. First segment apically with one bipinnate seta. Second segment with eight setae (two broken and two bipinnate). Third segment bearing five bare setae at its anterior margin and an acrothek consisting of one aes and two bare setae. Fourth segment with ten bare setae (1 broken), of which two are fused at their bases and arising from a knob together with a small aes. Setal formula: I – 1, II – 8, III – 5 (+ 2 and aes), IV – 8 (+ 2 and aes).

A 2 (Fig. 6 A, B View Figure 6 ) lacking exp. Allobasis with two abexopodal setae (1 seta broken in Fig. 6 A View Figure 6 ). Enp (Fig. 6 B View Figure 6 ) anteriorly with row of spinules, medially with two pinnate and one smaller bare seta. Terminally with six setae, at least three of which long, unipinnate and geniculated, the anterior ones short and bipinnate, the posterior seta bare.

Md (Fig. 6 C, C View Figure 6 *) gnathobase strong, with two strongly sclerotised teeth that vary in their shape, one broad brush-like element and one small bare seta. Md palp (Fig. 6 C View Figure 6 ) formed by fused basis, enp, and exp; long and slender, with basal seta no. 2 and endopodal setae nos. 3–5; basal seta no. 1 and exopodal seta no. 6 completely reduced.

Mxl (Fig. 7 A View Figure 7 ) praecoxal arthrite basally with row of spinules; terminally with four bare and two unipinnate strong spines; subapically with two bare setae; additionally, with two bare surface setae, and on the other side with curved row of long spinules. Coxal endite with one bare small seta. Basis fused with enp and exp, forming a single segment that carries two lateral and two apical setae.

Mx (Fig. 7 B View Figure 7 ) syncoxa with two distinct endites, few long spinules along outer basal edge, and row of spinules along other distal margin.

Proximal endite stronger than distal one, with few spinules and two spines, the proximal one biplumose and fused to the endite, the distal one with one single ruffle; the distal endite apically with three small bare setae. Allobasis distinct, produced into strong claw that carries one strong spinulose ruffle; additionally, with two bare setae. Endopod small and knob-like, equipped with two bare setae.

Mxp (Fig. 7 C View Figure 7 ) prehensile, syncoxa and basis densely covered with long spinules, syncoxa lacking seta. Enp produced into long bare claw, accompanied by slender seta at its base.

P 1 (Fig. 8 A, B View Figure 8 ) with transversely elongate basis and two-segmented exopod, both covered with long spinules; endopod absent.

Basis with one bipinnate outer and one bare inner seta, the latter arising from protruding pedestal. Tube pore inserting proximally close to anterior margin. Exp 1 ~ 1 / 2 as long as exp 2, with one bipinnate outer seta; exp 2 with one bipinnate outer spine and four (sub) apical geniculate setae, which present a very fine serration previous to the geniculation. Subapically on anterior surface with tube pore.

Pseudechinopsyllus andrei sp. nov. exhibits a remarkable intraspecific variability that is expressed in the abnormal development of supernumerary setae or even segments on some swimming legs in single individuals. For example, the left P 1 exp 2 on syntype 1 bears an inner seta (arrow in Fig. 8 A View Figure 8 ), which is missing on the right exp 2 (Fig. 8 B View Figure 8 ). We interpret this additional seta as abnormal because it is not present in any other species of the Ceratonotus group. Further abnormal setal and segment formation was found on the P 2 and the P 5 (see below).

P 2 – P 4 (Figs 9 A, B View Figure 9 , 10 A View Figure 10 , 11 A, B View Figure 11 ) with laterally elongated, bow-like intercoxal sclerites as exemplified for P 4 (Fig. 11 B View Figure 11 ) and transversely elongate bases that are covered with several long spinules and carry one outer seta (bipinnate in P 2, bare in P 3 and P 4) and one very long tube pore. Exopods three-segmented; exp 1 with one bipinnate outer seta, exp 2 with one bare inner seta and one bipinnate outer spine; in P 2 additionally with long tube pore. In Syntype 1, however, like the left-hand P 1 exp 2 also the left-hand P 2 exp 2 bears an additional inner seta (arrow in Fig. 9 B View Figure 9 ). Exp 3 with two outer spines and two apical setae, the innermost of which narrower and shorter than the outermost one; P 2 and P 4 exp 3 additionally with one inner, P 3 exp 3 with two inner setae. P 3 laterally, P 4 subapically at outer margin with tube pore. P 2 (Fig. 9 A View Figure 9 ) lacking enp. P 3 and P 4 (Figs 10 A View Figure 10 , 11 A View Figure 11 ) each with small knob-like enp carrying one bare seta. Setal formula shown in Table 1 View Table 1 .

P 5 (Fig. 12 A View Figure 12 ) Basoendopod and exopod not fused. Endopodal lobe of basoendopod with long spinules, one tiny bare and one long bipinnate seta, accompanied by three tube pores. Outer basoendopodal seta arising from extremely long setophore (see asterisk *), which is almost twice the length of the exopod and accompanied by one tube pore. Exp also equipped with long spinules, and with two outer, one subapical, one apical and one inner bipinnate setae, as well as with long slender tube pore distally.

GF (Fig. 12 B View Figure 12 ) P 6 strongly reduced in size, each lobe bearing one tiny bare apical seta; margin on the inner side of the setae grown out into two small but distinctive spikes. Gonopore only indistinctly recognisable, ovoid in shape, and opening into two distal sclerotised formations.

Male. The male resembles the female in most characters, with the exception of the (sexually dimorphic) body size, development of the segments between thorax and abdomen, and in the likewise sexually dimorphic shapes of the A 1, the P 3 and P 4 endopods, the P 5, and the P 6.

Habitus almost identical to that of the female but clearly (up to 1 / 3) smaller (mean 944.6 µm; range 908.8 µm – 979.4 µm; n = 3) and lacking GDS (cf. Fig. 2 B View Figure 2 ).

A 1 (Figs 13 A View Figure 13 , 14 View Figure 14 ) eight-segmented, haplocer. First segment longest, with several long spinules, and with one bipinnate distal seta (Fig. 14 View Figure 14 ); second segment smaller than first one, with eight bare setae and several long spinules posteriorly (Fig. 14 View Figure 14 ); third segment much smaller than preceding segments, with five bare setae (Fig. 14 View Figure 14 ); fourth segment smallest, no setae discernible (Fig. 14 View Figure 14 ). Fifth segment very slightly swollen, with rows of spinules, and bearing ten setae (all broken in Fig. 14 View Figure 14 ) plus acrothek formed by two setae and one aes arising from long protrusion; sixth segment slender, with two setae (broken in Fig. 14 View Figure 14 ); seventh segment small, with one seta (broken in Fig. 14 View Figure 14 ); eighth segment enlarged, distally acute, with seven bare setae (1 broken in Fig. 14 View Figure 14 ) and a subapical acrothek formed by aes and two additional setae. Segment apically spatulate (arrowed in Fig. 14 View Figure 14 ). Setal formula: I- 1; II- 8; III- 5; IV- 0; V- 12 + aes; VI- 2; VII- 1; VIII- 9 + aes.

P 3 exopod as in female; endopod (Fig. 10 B View Figure 10 ) three-segmented, enp 1 small, with some spinules at outer margin; enp 2 longest segment, with a slender outwardly curved apophysis that is longer than the whole endopod; enp 3 minute, with one long bare apical seta.

P 4 exopod as in female; endopod (Fig. 11 C View Figure 11 ) small, two-segmented, enp 1 with few spinules on inner margin, enp 2 with two bare apical setae.

P 5 (Fig. 13 B, C View Figure 13 ) of similar shape as that of female but without spinulose coverage. Endopod also fused to the basis (= basoendopod), exopod distinct. The outer basal setophore (Fig. 13 B View Figure 13 ) is shorter than in the female, only reaching the length of the exopod. Endopodal lobe (Fig. 13 C View Figure 13 ) of syntypes 4 and 5 apically with two short bare setae and two tube pores. In contrast, the endopodal lobe of syntype 10 is divided into two segments (Fig. 13 B View Figure 13 ; arrow indicating boundary), armouring of second segment as in syntypes 4 and 5.

P 6 not even rudimentarily recognisable, apparently completely reduced.

Etymology.

The epithet andrei is given in fondly and grateful memory of Prof. Dr André M. Esteves (Federal University of Pernambuco ( UFPE), Brazil), who passed away on 30 April 2025.