Neoasterocheres serrulatus (Humes, 1996) Humes, 1996

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 : 108-111

Neoasterocheres serrulatus (Humes, 1996) n. comb.

( Figs. 4–5 )

Madacheres serrulatus Humes, 1996

Asterocheres serrulatus (Humes, 1996)

Material examined. Female holotype ( USNM 268463 ), in 2m, associated with Galaxea fascicularis (L.), west of Pte. Mahatsinjo , Nosy Bé, northwestern Madagascar, January 31 th 1964.

Description of the female. Body length (excluding caudal setae) 1147 µm, width 853 µm. Body cyclopiform ( Fig. 4 A), prosome slightly wider than long with sensiles on dorsal surface, urosome cylindrical. First pedigerous somite completely fused to cephalosome to form cephalothorax and showing epimera projected. Pedigerous somite 2 to 4 with rounded epimera and gradually reducing on width. Pedigerous somite 4 partially overlapped by third somite, almost entirely covering fifth pedigerous somite. Prosome length: width ratio = 0.9:1. Prosome: urosome ratio of length = 1.8:1.

Urosome ( Fig. 4 B) 4-segmented. Genital double-somite as long as wide, with widest portion located medially on region of genital pores. Genital apertures ventral, with two short setae, lateral margins with row of setules close to genital pores. First post-genital somite as long as wide. Anal somite 1.5 times wider than long. Both post-genital somites showing posterior margin serrated and lateral margins covered with setules. Caudal rami slightly longer than wide with posterior margin serrated and bearing tooth-like projection ( Fig. 4 C), armed with six setae, seta I absent, setae II to VII present. All setae plumose.

Antennule ( Fig. 4 D) 519 µm long (not including setae), 19-segmented. Length of segments: 50, 13, 17, 17, 10, 13, 10, 13, 13, 20, 23, 27, 47, 57, 47, 37, 67, 33 and 47 µm respectively. Segmental homologies and armature 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-XIII)-6; 10(XIV)-1+spine; 11(XV)-2; 12(XVI)-1; 13(XVII)-2; 14(XVIII)-2; 15(XIX)-1; 16(XX)-1; 17(XXI)-1+ae; 18(XXII–XXIII)-2; 19(XXVI–XXVIII)-6; all setae smooth. Aesthetasc 167 µm long.

Antenna ( Fig. 4 E) 290 µm long (including distal claw). Coxa and basis unarmed. Basis 84 µm long. Exopod one-segmented, 14 µm long, with two short apical and one lateral setae. Endopod 3-segmented, first segment 79 µm long, unarmed, with row of setules on outer margin; second segment 14 µm long, with medial naked seta; third segment 9 µm long, with two distal setae near thin claw distally curved (73 µm long).

Oral cone ( Fig. 4 A) 247 µm long, siphon-like, reaching to maxillipedal basis. Mandible ( Fig. 4 F) with slender 2-segmented palp; measuring 98 and 34 µm long, respectively, both with setules covering outer margins; second segment with two distal smooth setae. Mandibular stylet 229 µm long, proximally stout, tapering distally into a narrow sharpened ending.

Maxillule ( Fig. 4 G) bilobed; outer lobe, 40 µm long, armed with three smooth setae; inner lobe 107 µm long, armed with four distal smooth setae. Maxilla ( Fig. 5 A) 340 40 µm long, consisting of long and narrow syncoxa and long narrow curved claw, with 156 and 190 µm long, respectively.

Maxilliped ( Fig. 5 B) 5-segmented, 440 µm long; syncoxa 110 µm long, armed with inner smooth seta; basis 150 µm long, unarmed. Endopod three-segmented, segments measuring 8, 14 and 58 µm, respectively; each segment armed with one seta distally. Third segment with distal seta located close to straight claw-like element, 100 µm long.

Legs 1–4 ( Fig. 5 C–F) biramous, with 3-segmented rami. Armature formula as follows:

Spine of first exopodal segment of leg 1 reaching distal margin of second exopodal segment. Third exopodal segment of leg 1 armed distally with spine and seta. Third endopodal segment of legs 2 to 4 with seta and spine distally. Distal spine of third exopodal segment of leg 4 with setules on inner margin. Fifth leg ( Fig. 5 G) with free segment armed with two setae and rows of setules on lateral margins. Fifth pedigerous somite with single seta near insertion of free segment.

Male. Unknown.

Discussion. The redescription show some inconsistences between the characteristics observed here and the original description of Neoasterocheres serrulatus made by Humes (1996a). The first concerning the second endopodal segment of the antenna that has only a seta instead three cited by Humes (1996a). In the original description, Humes (1996a) mentioned the siphon reaching near insertion of leg 1, however the siphon is little short, reaching the maxilliped. The maxilliped possesses a seta on the coxa, not observed by Humes (1996a). Humes (1996a) also misinterpreted the maxilla when quoted a suture on the median portion of claw, which was not observed. Humes (1996a) described the third exopodal segment of leg 1 as having two distal setae instead a seta and a spine observed here. According Humes (1996a) the third segment of leg 2 has two setae on distal portion but this segment show a seta and a spine distally. Humes (1996a) depicted this species as possessing two terminal spines on third endopodal segments of legs 3 and 4. However, the reported armature setation for the swimming legs, these segments appeared as having a seta and a spine distally, a condition observed in this revision. Another difference observed regards the number of setae on leg 5, which has two setae instead three as described by Humes (1996a).

Among the major problems related previously with the original description of the genus by Humes (1996a) is the fact that the characters used to justify the status of Madacheres as a genus does not support it, because it is not possible to effectively differentiate Madacheres from Neoasterocheres . This situation has been observed by Ivanenko (1999) and confirmed by Kim (2010).

Distribution. Neoasterocheres gen. nov. is cosmopolitan, although restricted to the tropical region. Its members are known to occur in the Indian, Indo-Pacific and Atlantic Oceans. Neoasterocheres enewetakensis , N. dysidea and N. rotundus are recorded from the Marshall Island, Mollucas and Indonesia, respectively. Neoasterocheres serrulatus occurs in Madagascar and N. scutatus occurs in the Gulf of Aqaba, both in the Indian Ocean. Both Neoasterocheres humesi and N. breviseta n. sp. occur in the Western Atlantic Ocean, the first in the North Atlantic and the latter in the South Atlantic. It is not evident the existence of a biogeographic distributional pattern of the Neoasterocheres n. gen.

Figures

FIGURE 4. Neoasterocheres serrulatus (Humes, 1996) n. com., female (holotype: USNM 268463). A, habitus, dorsal view; B, urosome; C, left caudal rami, dorsal view; D, antennule; E, antenna; F, mandible; G, maxillule. Scale bars: A = 200 µm; B, D, G = 100 µm; C = 25 µm; E— F = 50 µm.

FIGURE 5. Neoasterocheres serrulatus (Humes, 1996) n. com., female (holotype: USNM 268463). A, maxilla; B, maxilliped; C, leg 1; D, leg 2; E, leg 3; F, leg 4; G, leg 5. Scale bars: A— G = 50 µm.