Asterocheres bimbarrensis, Bispo, Ricardo, Johnsson, Rodrigo & Neves, Elizabeth, 2006

Bispo, Ricardo, Johnsson, Rodrigo & Neves, Elizabeth, 2006, A new species of Asterocheres (Copepoda, Siphonostomatoida, Asterocheridae) associated to Placospongia cristata Boury-Esnault (Porifera) in Bahia State, Brazil, Zootaxa 1351, pp. 23-34 : 25-32

Asterocheres bimbarrensis sp. nov.

Figures 2–5

Material examined. Holotype: female ( UFBA 0 0 12 CRU), paratype (i.e. allotype): male ( UFBA 0 0 13 CRU), paratypes: 27 females ( UFBA 0 0 20 CRU) and 15 males ( UFBA 0 0 21 CRU) associated with P. cristata from Bimbarra Island, Madre de Deus, Bahia. Collected by R. Johnsson and R. Bispo, 0 1 August 2004.

Description of female. Body length (excluding caudal setae) 750 Μm (650–840 Μm), greatest body width 400 Μm (340–460 Μm), body length 1.65 times width (based on 28 specimens). Body shape cyclopiform ( Fig. 2 a), with prosome enlarged, dorsoventrally flattened and urosome cylindrical. Pedigerous somite 1 totally fused with cephalosome, with epimera moderately pointed. Pedigerous somites 2–4 with epimera slightly pointed. Pedigerous somite 4 partially covered by preceding somite. Prosome length:width ratio, 1.2:1. Ratio of prosome length to urosome, 2.3:1.

Urosome 4-segmented ( Fig. 2 b). Genital double-somite 113 Μm long, length:width ratio 1:1, rounded anterolaterally and with setae located close to genital area uncommonly long, compared to other Asterocheres species. Two postgenital somites, with posterior corners pointed and both wider than long (39 x 70 Μm, 44 x 65 Μm), length:width ratios, 0.56:1 and 0.68:1, respectively. Caudal rami subrectangular (35 x 29 Μm), length 1.2 times width, armed with 6 setae. Length of setae II to VII: 52, 157, 324, 289, 142, and 106 Μm, respectively; all setae plumose.

Antennule ( Fig. 2 c) slender, 332 Μm long (not including setae) and consisting of 20 segments. Length of segments measured along their posterior margins: 13, 12, 10, 9, 9, 10, 10, 11, 10, 6, 10, 18, 24, 24, 22, 27, 29, 35, 12, and 31 Μm, respectively. Segmental homologies and setation as follows: I-1; II-1; III-1; IV-1; V-1; VI-1; VII-2; VIII-2; IX-XII- 4; XIII-1; XIV-1+spine; XV-2; XVI-2; XVII-2; XVIII-1; XIX-2; XX-1; XXI-1+ae; XXII- XXIII-2; XXIV-XXVIII-7. Aesthetasc on segment XXI, 137 Μm long. Setation of III–VI based on insertions.

Antenna ( Fig. 2 d) 225 Μm long (including distal claw), basis 70 µm long. Exopod 1- segmented, 10 Μm long, with 2 setae located distally and subdistally. Endopod 3- segmented; first segment 61 Μm long, unarmed; second segment 12 Μm long, with apical setae; third segment 22 Μm long, with short lateral seta and terminal claw slightly curved and 60 Μm long with seta close to it. Oral cone ( Fig. 2 e) 84 Μm, reaching between maxilliped and leg 1. Mandible stylet-form ( Fig. 2 e–f) 70 Μm long, slender; 2-segmented palp (Fig. 3a): first segment 40 Μm long, ornamented with lateral setules; second segment 19 Μm long, armed with 2 apical, smooth setae.

Maxillule (Fig. 3b) bilobed; inner lobe 68 Μm, with 4 distal setae and ornamented with patches of setules: 1 basal, 1subapical. Outer lobe 27 Μm long, with 3 setae. Maxilla (Fig. 3c) with syncoxa 104 Μm long and claw, 166 Μm long, distally curved and with patch of subapical setules.

Maxilliped (Fig. 3d) 194 Μm long, 5-segmented; syncoxa 42 Μm long, with small seta on inner margin; basis 85 Μm long, with apical tooth; endopod 3-segmented, segments 19, 14, and 34 Μm long, respectively. First and second endopodal segments unarmed. Third segment with 2 setae medially on inner margin, indicating a possible fusion between 2 endopodal segments, and apical seta close to claw-like element 83 Μm long, slightly curved distally.

P1-P4 (Figs 3e–f, 4a–b) biramous, all rami 3-segmented. P2 and P3 endopod-3 with seta and spine distally, P4 endopod-3 with 2 serrate spines. Armature formula for P1-P 4 in Table 1.

P5 ( Fig. 2 b) 62 µm long, exopod with 3 distal setae, inner and outer margins covered with setules. Somite 5 bearing seta near insertion of exopod.

Description of male. Body similar to female but smaller ( Fig. 5 a). Length (excluding caudal setae) 650 Μm, greatest body width 332 Μm, body length 1.96 times width. Cephalosome and pedigerous somite 2 with epimera slightly pointed. Pedigerous somite 3 slightly rounded and partially covering pedigerous somite 4. Prosome length:width ratio 1.3:1. Ratio of length of prosome to urosome 2:1.

Urosome ( Fig. 5 b) 5-segmented. Genital somite 124 x 95 Μm, pointed post-laterally with 1 distal and 1 terminal seta on each side. Three abdominal somites, all wider than long (22 x 65, 23 x 55, 33 x 52 Μm); length:width ratios 0.34:1, 0.42:1 and 0.63:1, respectively. Caudal rami 28 x 22 Μm, length 1.26 times width, with 6 plumose setae.

Antennule ( Fig. 5 c) 249 Μm long (not including setae) and consisting of 18 segments. Length of segments measured along their posterior margins: 20, 11, 8, 9, 9, 8, 8, 9, 8, 11, 9, 6, 5, 17, 24, 22, 12, 38, and 26 Μm, respectively. Segmental homologies and setation as follows: I-2; II-2; III-2; IV-2; V-1; VI-2; VII-2; VIII-2; XI-XII-5; XIII-1; XIV-1; XV-2; XVI-2; XVII-2; XVIII-2; XIX-XXI-3+ae; XXII-XXIII-2; XXIV-XXVII-7. All setae smooth. Aesthetasc on segment XXI 121 Μm long.

All other appendages as for female.

Etymology. The specific name refers to the type locality of the specimen.

Remarks. Although A. bimbarrensis has been found on the same host species as A. neptunei both species have some marked differences. Asterocheres neptunei has a siphon, which reaches between the insertions of P1 and P2, the P5 exopod has two setae and the antennal exopod has three setae ( Johnsson et al. 2001). The siphon of A. bimbarrensis is only slightly longer than the maxilliped insertion while the P5 exopod has three setae and the antennal exopod has only two setae.

In addition, the following characteristics of A. bimbarrensis further distinguish it from A. neptunei : outer lobe of the maxillule with three setae, P4 endopod-3 with two spines distally, instead of a seta and a spine, the caudal rami longer than wide, the postgenital somite of the female only slightly longer than anal somite and the maxilliped at least twice as long as the preceding segment. These last three characteristics are also shared with the following species of Asterocheres : A. lunatus Johnsson, 1998 ; A. bacescui Marcus, 1965 ; A. maxillatus Stock, 1987 ; A. minutus (Claus, 1889) ; A. suberites Giesbrecht, 1897 and A. echinicola (Norman, 1868) .

Asterocheres bimbarrensis and A. echinicola have another apparent similarity: the 20- segmented antennule ( Sars 1918). However, the position of the aesthetasc on the antennule differs with A. echinicola having three segments posterior to the aesthetasc while A. bimbarrensis only has two. Such difference is due to different segmental fusions in both species. These species have the caudal rami longer than wide, however, in A. echinicola it is almost three times longer than wide ( Sars 1918) and in the new species it is only slightly longer than wide. Besides these differences, A. bimbarrensis also has a patch of setules distally on the maxilla claw and the siphon slightly longer than in A. echinicola .

In A. lunatus and A. bacescui the antennal exopod is armed with a single seta ( Johnsson 1998a; Marcus 1965), in A. suberites there are three setae ( Giesbrecht 1899), while in A. bimbarrensis there are two setae on the exopod. The genital somite of A. bacescui is wider than long, while in the new species it is as long as wide. The length of the caudal rami of A. bacescui is 1.7 times the width but in A. bimbarrensis it is slightly wider than long. Endopod segments 2 and 3 of the antenna of A. bacescui are fused, which is not the case in the new species. Finally, the mandibular palp of A. bacescui has a single segment ( Marcus 1965), a condition also present in A. minutus and A. suberites (cf. Giesbrecht 1899; Bocquet et al. 1963), in contrast to the 2-segmented palp of A. bimbarrensis .

Asterocheres minutus has both maxillule lobes almost identical in length ( Bocquet et al. 1963) and the maxilla claw without a distal patch of setules as observed in the new species. In A. bimbarrensis the maxillule inner lobe is more than twice the length of the outer lobe.

Asterocheres suberites and A. lunatus have a 21-segmented antennule with three segments distal to the aesthetasc and the maxilliped endopod is 4-segmented ( Johnsson 1998a; Giesbrecht 1899) while A. bimbarrensis has 20 segments on the antennule, maxilliped endopod is 3-segmented.

Among all these closely related species, A. lunatus is the only one found along the Brazilian coast, with its range from southern Bahia to Pernambuco. It is always found in association with sponges. However, the cephalosome and second pedigerous somite have pointed epimera and the third pedigerous somite covers not only entirely the fourth somite but also partially the fifth ( Johnsson 1998a). In A. maxillatus , pedigerous somite 3 entirely covers pedigerous somites 4 and 5 and partially covers the genital double-somite ( Stock 1987). The epimera of A. bimbarrensis are not projected and the third somite does not cover the posterior pedigerous somites.

Among the asterocherids mentioned above A. bimbarrensis is the only species with three setae on the outer lobe of the maxillule and two spines distally on the P4 endopod-3 instead of a seta and a spine.

Figures

FIGURE 2. Asterocheres bimbarrensis sp. nov. female (holotype: UFBA 0 0 12 CRU). a, habitus, dorsal view; b, urosome (left long setae of the genital somite were omitted); c, antennule; d, antenna; e, oral cone; f, distal end of mandibular stylet. Scale bars: a = 100 µm; b – d = 50 µm; e – f = 20 µm.

FIGURE 4. Asterocheres bimbarrensis sp. nov. female (holotype: UFBA 0 0 12 CRU). a, P 3; b, P 4. Scale bars: 50 µm.

FIGURE 5. Asterocheres bimbarrensis sp. nov. male (paratype: UFBA 0 0 20 CRU). a, dorsal view; b, urosome; c, antennule. Scale bars: a = 100 µm; b – c = 50 µm.

Tables

TABLE 1. P 1 – P 4 armature formula for Asterocheres bimbarrensis male and females.

	Coxa	Basis	Exopod	Endopod
P1	0–1	1–I	I–1; I–1; III–2–2	0–1; 0–2; 1–2–3
P2	0–0	1–0	I–1; I–1; III–I–4	0–1; 0–2; 1–1+I–3
P3	0–0	1–0	I–1; I–1; III–I–4	0–1; 0–2; 1–1+I–3
P4	0–1	1–0	I–1; I–1; III–I–4	0–1; 0–2; 1–II–2