Parastenocaris joi, Brancelj, Anton, 2015

Brancelj, Anton, 2015, Two new stygobiotic copepod species from the Tibesti area (Northern Chad) and a re-description of Pilocamptus schroederi (van Douwe, 1915), Zootaxa 3994 (4), pp. 531-555 : 549-553

Parastenocaris joi sp. nov.

(Figs. 9–10)

Type locality. Chad, Tibetsi area; groundwater in dry channel of river Uet Duar near village Totous, northern Chad; 19 o26'22'' N 17o31'47'' E; altitude: 585 m ( Fig. 1 ).

Material examined. Holotype: adult female (length 390 µm), completely dissected, mounted on one slide; collected on 14 March 2014 from ground water on the bottom of 1.5 m deep Karaman-Chappuis pit; access No.: PMSL-Copepoda-Brancelj-1362.

Paratypes: 4 adult females stored in 70% alcohol; collected on the same date and location as holotype; access No.: PMSL-Copepoda-Brancelj-1363.

Etymology. The new species is named after Jo Vermeir, a member of the Chad expedition. I dedicate this species to him in a honour of our long-lasting friendship and his reliability during many expeditions in remote places.

Description. Female, body length, measured from tip of rostrum to posterior margin of caudal rami, 384–409 µm (mean: 388 µm; n = 5); elongated, slightly compressed in dorsoventral direction; largest body width on fourth pedigerous somite; preserved specimens colourless (Figs. 9A, B). Naupliar eye not discernible. Rostrum very small, triangular; no sensilla observed. Integumental window not discernible on any somite. Posterior margins of prosomites and urosomites smooth dorsally (Figs. 9A, B). Genital double-somite as long as wide. Genital complex with single copulatory pore, poorly sclerotized, broadly rounded; seminal receptacles small, simple. Fused plate with reduced P6 positioned well above seminal receptacles (Fig. 10E). Anal segment on ventral side with 2 groups of minute spinules mediolaterally (Figs. 9 B, C). Anal operculum large; 2 sensilla positioned anteriorly; free margin almost straight, not reaching distal end of anal somite (Figs. 9A, B, C).

Caudal rami slightly conical, slightly curved, diverging; each ramus about 3.5-times as long as wide, with few small spines at the distal inner corner (Fig. 9C). Anterolateral external accessory seta (I) slightly shorter than width of furcal ramus, inserted at about 2/3 of its length. Anterolateral external accessory seta (II) about 1.5-times longer than seta I, positioned close to it. Posterolateral seta (III) positioned close to seta II, about twice as long as seta I. Outer apical seta (IV), about 0.5 length of caudal ramus, spiniform, smooth. Inner apical seta (V) straight, with several minute spines on both sides, about 5-times as long as caudal ramus. Inner accessory seta (VI) as long as outer apical seta, soft, smooth. Dorsal seta (VII) slightly longer than caudal ramus, inserted on internal side of it, at about 2/3 of its length (Figs. 9A, B, C).

Antennule (Fig. 9D) as long as cephalothorax, 7-segmented. Aesthetasc (ae) on fourth segment cylindrical, with rounded tip, overreaching tip of seventh segment. Setal formula: 0.4.3.2+ae.1.1. 8+ae.

Antenna (Fig. 9E) with allobasis; small, 1-segmented Exp; robust 1-segmented Enp. Exp with one seta apically. 3 strong spines on outer margin of Enp, increasing in length distally; apical armature consisting of one short and one long robust spine on outermost locations; 3 geniculate setae between both spines.

Mandible (Fig. 9F) short, robust, with 3 strongly chitinised teeth on cutting edge. Dorsal seta near gnathobase. Mandibular palp relatively long, 1-segmented; apically 2 long setae, similar in length.

Maxillule (Fig. 9G) with 3 strong, long spines on praecoxal arthrite. Coxa with 2 setae unequal in length. Basis with one seta.

Maxilla (Fig. 9H) 2-segmented; syncoxa with 2 endites, each with 2 elements apically. Basis with strong beaklike outgrowth. Enp small, with 2 setae unequal in length.

Maxilliped (Fig. 9I) comprising syncoxa, basis, 1-segmented Enp. Syncoxa with no seta distally. Basis 5-times as long as wide. Enp drawn out into strong, acutely curved claw; about half of basis length; additional armature represented by a short seta.

FIGURE 9. Parastenocaris joi sp. nov., holotype female: A, habitus dorsal view; B, urosome, lateral view; C, 5th urosomal and anal somite with furcal rami, dorsal view; D, antennule; E, antenna; F, mandible; G, maxillule; H, maxilla; I, maxilliped.

FIGURE 10. Parastenocaris joi sp. nov., holotype female: A, P1; B, P2; C, P3; D, P4; E, P5 & P6 and genital field.

P1 (Fig. 10A): basis with row of spinules on anterior margin distally. 3-segmented Exp, 2-segmented Enp; equal in length. Exp-1 with one strong outer spine; Exp-2 with no spine or seta; Exp-3 with one strong spine subapically; 3 setae apically, increasing in length, longer 2 genicualte. Longest geniculate seta longer than Exp. Enp-1 with no seta or spine; row of spines along outer margin. Enp-2 with 2 setae apically, longer one geniculate and longer than End.

P2 (Fig. 10B): basis with one spiniform outer seta. 3-segmented Exp, 1-segmented Enp. Enp about 1/2 length of Exp-1. Exp-1 about 4-times as long as wide, with 2 spines along outer margin. Proximal spine smooth, at 1/4 of Exp-1 length; distal one with small spinules, at the distal corner. Exp-2 about 3-times as long as wide, with few spinules along outer margin. Exp-3 as long as Exp-2, with 2 outer spines; proximal very sort, distal about 1/3 longer than Exp-3; 2 spiniform setae apically; shorter one with spinules unilaterally, longer one bipinnate. Enp-1 4.5- times as long as wide; with 4 elements apically: 3 short spiniform setae, one long smooth seta, about 1.5-times longer than Enp-1.

P3 (Fig. 10C): basis with one long, thin, smooth seta on outer margin. 2-segmented Exp, 1-segmented Enp. Enp about 0.5 length of Exp-1. Exp-1 similar to Exp-1 of P2. Exp-2 with one long spine subapically, one long spiniform seta apically. Enp-1 about 6-times as long as wide; with 3 spines unequal in length apically; one very short, the longest about 0.5 length of Enp-1.

P4 (Fig. 10D): basis with one long, thin, smooth seta on outer margin. 3-segmented Exp, 1-segmented Enp. Enp about 1/2 length of Exp-1. Exp-1 with 3 spines, increasing in length; proximal shortest, distal longest; proximal spine at 1/3 of outer margin length; middle spine at 2/3 of margin length; distal one subapically. Exp-2 with 2 small spines; one at 2/3 of margin length, second one subapically. Exp-3 4.5-times as long as wide, with 2 relatively weak spines on outer margin; proximal at 3/4 of margin length, distal one subapically; two elements apically: one spiniform seta as long as Exp-3, one about 3-times longer than Exp-3. Enp-1 5-times as wide as long, about 0.5-times length of Exp-1. 3 elements apically: 2 very short spines, one spiniform seta about 1.5-length of Enp.

P5 (Fig. 10E) well separated, each half triangular in shape, with sharply pointed tip. Outer margin with 2 short spines distally, one long smooth seta proximally. Inner margin smooth.

P6 (Fig. 10E) reduced to small, fused plate, with pointed tip on each side.

Male. Not known.

Variability. Except slight differences in body length, no variability was observed.

Remarks. Since only females were collected, it is not possible to allocate the new species accurately to any of the many new genera recently described or resurrected ( Karanovic & Lee 2012). For that reason this species should be provisionally included into the genus Parastenoscaris Kessler, 1913, sensu lato, until males are found enabling precise allocation of the species into its definitive genus status.

So far only five species of parastenocaridids have been recorded from the Sahara ( Table 1 ). From Mali, Chappuis (1959) reported Parastenocaris nigerianus Chappuis, 1959 and Monodicaris monodi ( Chappuis, 1959) . A further three species have been reported from Algeria: Parastenocaris kabyla Chappuis, 1954 ; Parastenocaris ahaggarica Božić, 1978 ; and Cotarellicaris numidiensis ( Rouch, 1987) (see Chappuis 1954; Božić 1978; Rouch 1987).

More detailed analysis of possible differences between those five species and the new species is difficult as the previous descriptions were frequently incomplete. In fact, there are no figures for P. kabyla , which was collected close to the coast, and only males were found. Chappuis (1954) reported that P4 and P5 of the male of P. kabyla are similar to those in P. fontinalis Schnitter & Chappuis, 1915 . As figured in Janetzky et al. (1996), P 5 in the female of P. fontinalis is quite different from those in P. joi sp. nov.

For P. nigerianus and M. monodi , only figures of males are presented and there are not enough details in the text to make any concise conclusions on taxonomic relations between those two species and the new one. However, the shape and armature of furcal ramus in males, and especially the position of lateral and dorsal setae, are quite different from those observed in the female of the new species. In M. monodi furcal ramus is longer, straight, conical, with width/length ratio of about 1:6 (about 1: 3.5 in the new species) and with only one external lateral seta (anterolateral external accessory seta (II)?) vs. three relatively long setae (I-III) in the new species. Outer apical seta (IV) in M. monodi looks long and soft, but short and spiniform in the new species. Only insertion of dorsal seta (VII) at 1/2 of inner margin length is similar to those in P. joi .

In P. nigerianus width/length of furca is about 1:4; divergent and slightly curved outward, like in the new species. In P. numidiensis one single external seta is figured (anterolateral external accessory seta (II)?) at about 1/ 3 of external margin length, compared to three setae in the new species: anterolateral external accessory seta (I), anterolateral external accessory seta (II) and posterolateral seta (III); all inserted at about 2/3 of external margin length (Fig. 9C). Shape and position of outer apical seta (IV) is similar in both species. Insertion of dorsal seta (VII) in P. nigerianus is at the distal middle part of furcal rami, while in the new species is at internal side of it, at about 2/3 of its length.

For two species enough detailed description exists to make more firm conclusions on taxonomic relations between them and the new species. In P. ahaggarica End P 2–P4 of the female have one apical element each and thus are different from those in P. joi , with 3 or 4 elements of different lengths on each End. Also P 5 in both species differ in shape and number of elements. P 5 in P. joi has three elements laterally and a pointed distal end while P. ahaggarica has four elements; two of them apically and with no distinct tip.

There are some similarities between P. numidiensis and P. joi in the armatures of P2 and P4, but not of P3. End P3 of P. joi has three elements apically, while in P. numidiensis , the distal part of End ends with a sharp point. The distal end of P 5 in both species ends with a sharp point, but on the outer margin there are 3 elements in P. joi and four in P. numidiensis . In P. numidiensis there is a very obvious incision in the middle of the outer margin, just next to the longest seta on P5, while in P. joi there is only slight depression. There are also differences on the anal operculum, which is short, and with straight free margin in P. joi , but longer and semicircular in P. numidiensis . The two species also differ considerably in the shape of the furcal rami and their armature. In P. numidiensis the furcal ramus is curved inward, while in P. joi it is curved outward. The lateral setae and dorsal seta in P. joi are positioned at 2/3 of caudal ramus length, while in P. numidiensis they are positioned at about 3/4 of the caudal ramus length. The inner apical seta (V) is swollen at the base in P. numidiensis , while in P. joi it tapers evenly from its base to tip.

On consideration of the above listed differences between the six species from the Sahara it is evident that the collected specimens belong to the new species, P. joi . At the same time the existence of several characters in common between P. numidiensis and the new species also indicates that the new species belongs to the genus Parastenocaris Kessler, 1913 , sensu stricto.

Figures

FIGURE 1. Locations for sampling of groundwater fauna in the Ounianga-Tibesti region (northern Chad). White arrows: shore of the lakes Ounianga Kebir and Bokou; white circles: the river bank near the village Yebi Bou, a spring near the village Gonoa and the river bed of the Uet Duar at the village Totous.