Setacheres portobarrensis, Borges & Neves & Johnsson, 2017

Setacheres portobarrensis sp. nov.

( Figs. 2–4 View FIGURE2 View FIGURE 3 View FIGURE 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 GoogleMaps , 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 View FIGURE2 ) 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 View FIGURE2 ) 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 View FIGURE2 ) 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 View FIGURE2 ) wider than long (72 × 224 µm), triangular with rounded apex. Antennule ( Fig. 2d View FIGURE2 ) 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 View FIGURE 3 ) 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 View FIGURE2 ) 172 × 94 µm (length × width), reaching to insertion of maxilliped bases. Mandible ( Fig. 3b View FIGURE 3 ) 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 View FIGURE 3 ) 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 View FIGURE 3 ) 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 View FIGURE 3 ) 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 View FIGURE 4 ) 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 View FIGURE 4 ). Leg 3 with distal seta on third exopodal segment, instead of spine ( Fig. 4c View FIGURE 4 ). Leg 4 with distal spine on third endopodal segment ( Fig. 4d View FIGURE 4 ). Leg 5 ( Fig.4e View FIGURE 4 ) 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 GoogleMaps .

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 View FIGURE 3 ); 2) mandibular stylet with subterminal serrated portion and triangular distal end (arrow in Fig. 3b View FIGURE 3 ); 3) outer lobe of the maxillule with a very thick, claw-like bristle (arrow in Fig. 3c View FIGURE 3 ).

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.