Setacheres portobarrensis, Borges & Neves & Johnsson, 2017

Borges, Camila C., Neves, Elizabeth G. & Johnsson, Rodrigo, 2017, A new Setacheres (Copepoda, Siphonostomatoida, Asterocheridae) associated with Ircinia felix (Duchassaing & Michelotti) (Porifera) from Brazil, Zootaxa 4363 (1), pp. 129-136 : 131-135

Setacheres portobarrensis sp. nov.

( Figs. 2–4 )

Material examined. Holotype adult female ( UFBA 3182 ) and paratype adult female ( UFBA 3183 ), Porto da Barra Beach (13°00'14.01"S, 038°32'3.14"W), Salvador city, Bahia State , Brazil, collected by C. Bahia and V. Queiroz on 4 August 2011. Both specimens found associated with Ircinia felix . Paratype ( UFBA 3183 ) dissected and mounted on slide. Holotype preserved in ethanol.

Description of female. Mean body length (excluding caudal setae) 687 µm (686–688 µm) and mean body width 393 µm (390–395 µm) (n = 2). Body ( Fig. 2a ) cyclopiform, dorsoventrally flattened, prosome longer than wide, urosome cylindrical. Pedigerous somite 1 completely fused with cephalothorax to form cephalosome. Pedigerous somites 2–4 with posterolateral margins not projected posteriorly and slightly rounded. Pedigerous somite 3 longer than pedigerous somite 2. Pedigerous somite 4 smaller than third somite and larger than fifth somite.

Prosome 470 µm long and 386 µm wide. Length: width ratio = 1.2:1. Urosome ( Fig. 2b ) 4-segmented. Fifth pedigerous somite 32 µm long and 116 µm wide. Genital somite 79 µm long and maximum width 104 µm, length: width ratio = 0.7:1, vestigial leg 6 located midlaterally with thin seta, close to genital openings; setules located posteriorly to leg 6. Two postgenital somites, both wider than long (36 × 56, 38 × 55 µm, respectively), epimera directed posterolaterally; first postgenital somite armed with 2 spinules on outer margin, anal somite with 4 spinules along lateral margin. Prosome: urosome ratio = 2.2:1. Caudal rami ( Fig. 2b ) longer than wide, 25×22 µm. Length: width ratio 1.1:1 µm, armed with 6 setae. All setae on specimens broken.

Rostrum ( Fig. 2c ) wider than long (72 × 224 µm), triangular with rounded apex. Antennule ( Fig. 2d ) 295 µm long (not including setae), 21-segmented. Lengths of segments in proximal to distal order: 35, 9, 9, 8, 9, 7, 9, 14, 10, 5, 8, 17, 20, 19, 13, 20, 23, 26, 9, 10 and 7 µm. Segmental homologies as follows: 1(I)-2; 2(II)-2; 3(III)-2; 4(IV)-2; 5(V)-2; 6(VI)-2; 7(VII)-2; 8(VIII)-2; 9(IX–XII)-6; 10(XIII)-2; 11(XIV)-I+2, 12(XV)-2; 13(XVI)-2; 14(XVII)-2; 15(XVIII)-2; 16(XIX)-2; 17(XX)-2; 18 (XXI)-2+ Aesthetasc; 19(XXII–XXIII)-3; 20(XXIV–XXV)- 1; 21(XXVI–XXVIII)-5. Aesthetasc 72 μm long. Both setae from segments 1–3 and one seta from segment 8 with sparse setules distally.

Antenna ( Fig. 3a ) 192 µm long (including distal claw); coxa 14 µm long; basis 62 µm long with spinules along inner margin. Exopod 1-segmented, 8 µm long, with 2 apical setae and small subdistal seta; all setae naked. Endopod 3-segmented; first segment 56 µm long, unarmed, inner margin ornamented medially with row of spinules and armed distally with 3 large spinules; second segment 6 µm long, armed with single robust seta covered with setules; third segment 10 µm long, armed with 2 subdistal spiniform setae and distal claw (36 µm).

Oral cone ( Fig.2a ) 172 × 94 µm (length × width), reaching to insertion of maxilliped bases. Mandible ( Fig. 3b ) with 2-segmented palp, both segments slender and naked, measuring 26 and 25 µm long, respectively; second segment with 2 naked distal setae, longer seta twice as long as shorter seta. Mandibular stylet 128 µm long, distally acuminate, posteriorly to a subterminal serrated portion with 7 teeth and triangular distal end. Maxillule ( Fig. 3c ) bilobed, both lobes laterally naked; inner lobe 50 µm long, with 5 naked distal setae, one seta much smaller than others. Outer lobe 18 µm long, armed with 4 naked distal setae, one more robust than the others. Maxilla ( Fig.3d ) 230 µm long, syncoxa 95 µm long, with small tooth-like projection on outer margin plus tubular extension of maxillary gland opening and strongly curved distally claw.

Maxilliped ( Fig.3e ) 6-segmented, 246 µm long; syncoxa 51 µm long with naked seta on inner margin and minute tooth-like projection on outer margin; basis 90 µm long, with subdistal row of setules and 2 small rows of spinules on inner and outer margins, respectively. Endopod 4-segmented, segments measuring 22, 9, 12 and 25 µm long, respectively; first and second segments naked, third segment with naked seta; fourth segment with spiniform serrate seta, close to distal curved claw-like element 46 µm long, with spinules on inner margin approximately reaching midlength.

Legs 1−4 ( Figs. 4a −d ) biramous, with 3-segmented rami. Armature formula as follows:

coxa basis exopod endopod

leg 1 0–1 1–1 I–1; I–1; III,4 0–1; 0–2; 1,2,3

leg 2 0–1 1–0 I–1; I–1; III,I,4 0–1; 0–2; 1,2,3

leg 3 0–1 1–0 I–1; I–1; III,1,4 0–1; 0–2; 1,2,3

leg 4 0–1 1–0 I–1; I–1; III,I,4 0-1; 0–2; 1,1+I,2

All legs with small spinules on outer margin of coxa, legs 2 and 3 each with a single spinule, leg 4 with 4 spinules and leg 1 with 2 rows of spinules. Legs 2 - 4 each with long setules along outer margin of endopod. Outer margins of most exopodal segments covered with small spinules. First exopodal segment of leg 1 bearing large spine reaching insertion of proximalmost spine of third exopodal segment. Second segment with tiny spine, smaller than adjacent tooth-like projection ( Fig. 4a ). Leg 3 with distal seta on third exopodal segment, instead of spine ( Fig. 4c ). Leg 4 with distal spine on third endopodal segment ( Fig. 4d ). Leg 5 ( Fig.4e ) with longer spinules on both margins, with 3 naked distal setae.

Male. Unknown.

Type locality. Porto da Barra Beach (13°0'14.01"S, 38°32'3.14"W), Salvador city, Bahia State, Brazil .

Etymology. The name “ portobarrensis ” refers to the type locality of the new species, Porto da Barra Beach, in Salvador city, Bahia State, Brazil.

Remarks. In a recent study, Johnsson et al. (2016) erected the new genus, Setacheres in order to accommodate some Asterocheres that were previously considered as species inquirendae ( Kim, 2010). The main character shared by the species included in the new genus is the presence of 2 distal setae on the third endopodal segment of leg 3, instead of a seta and a spine. Considering the new species described here, the genus Setacheres now contains 10 species; they can be separated into three different groups based on the number of free segments posterior to the ancestral antennulary segment XXI, which can range from 1 to 3. Setacheres portobarrensis sp. nov. possesses a 21-segmented antennule, with 3 free segments distally, after the aesthetasc. An identical condition is observed in S. eudistomus Johnsson, Bahia & Neves, 2016 and S. lunatus Johnsson, 1998 , while S. paraboecki Johnsson, 1998 , despite showing 3 free distal segments, has a 20-segmented antennule, resulting from a fusion of segments in the mid-region of the antennule ( Johnsson 1998; Johnsson et al. 2016). Setacheres portobarrensis sp. nov. also differs from these two Brazilian species in the third exopodal segment of leg 3, which has a distal seta (III,1,4) instead of a spine (III,I,4) (Johnsson 1 998; Johnsson et al. 2016). Some other species of the genus with the same distal pattern are S. spinopaulus Johnsson, 1998 , S. unicus Johnsson, 2001 , S. abrolhensis Johnsson, 1998 , and S. paraboecki Johnsson, 1998 but none of them has a 21-segmented antennule ( Johnsson 1998; Johnsson et al. 2001). In addition, S. portobarrensis sp. nov. shows many unique features such as: 1) spine-like setae close to the distal claw on the third endopodal segment of the antenna (arrows in Fig. 3a ); 2) mandibular stylet with subterminal serrated portion and triangular distal end (arrow in Fig. 3b ); 3) outer lobe of the maxillule with a very thick, claw-like bristle (arrow in Fig. 3c ).

Distribution. Setacheres portobarrensis , like the other known members of the genus ( Johnsson et al. 2016), occurs in the Tropical Southwestern Atlantic Province (TSA) (Spalding et al. 2007), as observed for S. abrolhensis , S. lunatus , S. aplysinus , and S. spinopaulus (Johnsson & Neves 2012) . Further studies may provide additional information about the range of the new species.

Figures

FIGURE 3. Setacheres portobarrensis sp. nov. female (paratype: UFBA 3183). a, antenna, arrows indicating spine-like setae close to distal claw on third endopodal segment; b, mandible, arrow indicating mandibular stylet with subterminal serrated portion and triangular distal end; c, maxillule, arrow indicating very thick, claw-like bristle on outer lobe; d, maxilla; e, maxilliped. Scale bars:a–e = 50 µm.

FIGURE 4. Setacheres portobarrensis sp. nov. female (paratype: UFBA 3183). a, leg 1; b, leg 2; c, leg 3; d, leg 4; e, leg 5. Scale bars:a–d = 50 µm; e = 40 µm.

FIGURE2. Setacheresportobarrensissp. nov. female(paratype:UFBA 3183).a, body, dorsalview; b, rostrum;c, urosome; d, antennule.Scale bars:a = 125 µm; b = 50 µm; c = 70 µm; d = 50 µm.