Neoasterocheres breviseta, Canário, Roberta, Rocha, Carlos Eduardo Falavigna Da, Neves, Elizabeth & Johnsson, Rodrigo, 2017

Canário, Roberta, Rocha, Carlos Eduardo Falavigna Da, Neves, Elizabeth & Johnsson, Rodrigo, 2017, A new asterocherid genus (Copepoda: Siphonostomatoida) associated with Callyspongia Duchassaing & Michelotti and reassessment of six species of Asterocheres Boeck, Zootaxa 4247 (2), pp. 101-113 : 104-107

Neoasterocheres breviseta sp. nov.

( Figs. 2–3 )

Material examined. Holotype female ( UFBA 3178 ) and paratype female ( UFBA 3179 ), Yacht Club Bay (12o59’975’’S, 38o31’851’’W), located in Todos-os-Santos Bay , Salvador city, in Bahia State , Brazil, on November 25th, 2014. All specimens were found associated with Callyspongia sp.

Description of the female. Mean body length (excluding caudal setae) 393 µm and mean body width 202 µm. Body ( Fig. 2 A) cyclopiform with prosome slightly enlarged and dorso-ventrally flattened; urosome cylindrical. Pedigerous somite 1 completely fused to cephalosome to form cephalothorax with pointed epimera. Pedigerous somite 2 with slightly pointed epimera. Pedigerous somites 3 and 4 with rounded epimera.

Prosome 253 µm long and 200 µm width. Length: width ratio = 1.2:1. Prosome: urosome ratio of length 1.4:1. Urosome ( Fig. 2 B) 4-segmented. Genital double-somite 72 µm long, maximum width 50 µm, length: width ratio = 1.5:1, rounded anterolaterally, with posterior epimera pointed. Two postgenital somites, both wider than long (25 × 31 µm, 18 × 31 µm, respectively), length: width ratio 0.8:1 and 0.6:1 respectively, lateral margins naked, with pointed epimera. Caudal rami slightly longer than wide, 17 × 12 µm armed with six setae (seta I absent); setae II, VI and VII naked and setae III, IV and V plumose.

Antennule ( Fig. 2 C) 125 µm long (not including apical setae), 19-segmented. Length of segments: 19, 8, 3, 6, 4, 4, 5, 6, 6, 5, 3, 7, 6, 5, 6, 8, 9, 10 and 4 µm, respectively. Segmental homologies and armature as follows: 1(I)-2; 2(II)-2; 3(III)-2; 4(IV)-2; 5(V)-1; 6(VI)-2; 7(VII)-2; 8(VIII)-2; 9(IX–XIII)-7; 10(XIV)-2; 11(XV)-2; 12(XVI)-1; 13(XVII)-1; 14(XVIII)-1; 15(XIX)-1; 16(XX)-0; 17(XXI)-1+ae; 18(XXII–XXV)-3; 19(XXVI–XXVIII)-5; all setae smooth. Aesthetasc 45 µm long. Segments 9 and 18 with marks indicating fusions of ancestral segments IX– XII and XIII and XXII–XXIII and XXIV–XXV.

Antenna ( Fig. 2 D) 97 µm long (including distal claw), with basis 16 µm long and totally naked. Exopod 1- segmented, 4 µm long with two short apical setae. Endopod 3-segmented, first segment 21 µm long, unarmed; second segment 6 µm long, armed with small distal naked seta; third segment 7 µm long with two setae, one distal and other subdistal near curved claw (25 µm long).

Oral cone 88 µm long, reaching to maxillipedal basis. Mandible ( Fig. 2 E) with slender 2-segmented palp; measuring 16 and 10 µm long, respectively; second segment with two distal smooth setae. Mandibular stylet 66 µm long, proximally stout, tapering distally into a narrow sharpened ending.

Maxillule ( Fig. 2 F) bilobed; both lobes armed with three setae and with row of setules on inner margins. Inner lobe, 23 µm long armed with short, distally plumose setae. Outer lobe 15 µm long with two long setae and a shorter one. Maxilla ( Fig. 2 G) 180 µm long, consisting of syncoxa and long curved claw, with 42 and 138 µm long, respectively.

Maxilliped ( Fig. 3 A) 6-segmented, 107 µm long; syncoxa 30 µm long, unarmed; basis 45 µm long with long setules on inner margin and few setules on distal outer margin. Endopod 4-segmented, segments measuring 7; 4; 8 and 13 µm, respectively; first and second segment unarmed; third segment with small seta medially; fourth segment with distal seta near straight claw-like element distally curved, 26 µm long.

Legs 1–4 ( Figs. 3 B–E) biramous, with 3-segmented rami. Armature formula as follows:

Spine of first exopodal segment of leg 1 longer than others, reaching beyond insertion of first spine of third exopodal segment. Distal inner margin of third endopodal segment with long tooth, setation 1–5 ( Fig. 3 B). Second endopodal segments of legs 2–4 with lateral margin bifurcate. Coxa of leg 4 with very small naked seta, basis of leg 4 unarmed. Outer setae and distal setae of third endopodal segments of all swimming legs reduced in size.

Fifth leg ( Fig. 2 B) with free segment armed with three smooth setae. Fifth pedigerous somite with small seta near insertion of free segment.

Male. unknown.

Type locality. Yacht Club Bay (12o59’975’’S, 38o31’851’’W), located in Todos-os-Santos Bay , Salvador city, in Bahia State , Brazil.

Etymology. The specific name ‘ breviseta’ is a combination of Latin words ‘brevis’ (= short) and ‘seta’ (= bristle), referring to the small size of the endopodal setae of the third endopodal segments of legs 1–4.

Discussion. Neoasterocheres breviseta sp. nov. has 19-segmented antennule as its congeners but can be distinguished from N. dysidea, N. eniwetakensis, N. humesi , N. rotundus and N. serrulatus by having of a 6- segmented maxilliped, thus diverging from the 5-segmented condition found in these other species ( Malt 1991; Humes 1996a, 1996b, 1997; Varela 2012). In addition, N. breviseta sp. nov. differs from N. scutatus by having 3 setae on both maxillary lobes instead 4 as observed in both maxillary lobes of N. scutatus ( Stock 1966b) . The reduced size of the setae of the third endopodal segment of legs 1–4 and the reduction of the body length are also other unique features of the new species. Neoasterocheres breviseta sp. nov. has body length of less than 400 µm, clearly the smallest species of the genus; the body size of its congeners is over 720 µm (as in N. humesi ).

Figures

FIGURE 2. Neoasterocheres breviseta n. sp., female (paratype: UFBA 3179). A, habitus, dorsal view; B, urosome; C, antennule; D, antenna; E, mandible; F, maxillule; G, maxilla. Scale bars: A = 100 µm; B— G = 25 µm.

FIGURE 3. Neoasterocheres breviseta n. sp., female (paratype: UFBA 3179). A, maxilliped; B, leg 1; C, leg 2; D, leg 3; E, leg 4. Scale bars: A— E = 25 µm.