Asterocheres tarifensis, Conradi, Mercedes & Bandera, Eugenia, 2011

Conradi, Mercedes & Bandera, Eugenia, 2011, Asterocherids (Copepoda: Siphonostomatoida) associated with marine invertebrates in the Strait of Gibraltar, Zootaxa 2925, pp. 1-18 : 2-8

publication ID	https://doi.org/ 10.5281/zenodo.203417
DOI	https://doi.org/10.5281/zenodo.6187047
persistent identifier	https://treatment.plazi.org/id/413687BB-FFF2-B95A-AB87-F9ADFB9FFE59
treatment provided by	Plazi
scientific name	Asterocheres tarifensis
status	sp. nov.

Treatment

Asterocheres tarifensis , n. sp.

( Figs. 1–4 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 )

Material examined. (a) holotype female ( MNCN 20.04/8570) and one paratype female ( MNCN 20.04/8571) associated with the scleractinian coral Astroides calycularis (Pallas) from Tarifa Island (southern Spain, 36º 01N, 5º 36W) at 12 m depth collected in 1999; (b) 2 females and 2 males with the same sampling data as the holotype deposited in BEIM ( COP –513).

Description. Adult female: Body ( Fig. 1 View FIGURE 1 A) cyclopiform, slender with an oval cephalothorax and a cylindrical urosome. Mean body length 558 µm (510–625 µm) and greatest width 266 µm (240–310 µm), based on 3 specimens. Ratio of length to width of prosome 1.36:1. Ratio of length of prosome to that of urosome 2.18:1. Prosome comprising cephalothorax, fully incorporating first pedigerous somite, and 3 free pedigerous somites. Somite bearing leg 4 with posterolateral angles rounded ( Fig. 1 View FIGURE 1 A).

Urosome 4-segmented, comprising leg 5-bearing somite, genital double-somite and 2 free abdominal somites. Genital double-somite and following somites provided with large epicuticular scales arranged in overlapping pattern all around ( Figs. 1 View FIGURE 1 B, 4A). Posteroventral margins of urosomites ornamented with hyaline frills with more or less serrated margins ( Fig. 1 View FIGURE 1 C). Genital double-somite (95x 98 µm) slightly wider than long; paired genital apertures bipartite, comprising lateroventral copulatory pore and dorsolateral gonopore (oviduct opening); lateral margins with a spinule row (about 9–10 spinules) in distal third (posterior to genital apertures) ( Figs. 1 View FIGURE 1 B–C, 4A). Genital area armed with two setae ( Figs. 1 View FIGURE 1 B, 4B). Integumental pores and sensilla present on urosomites.

Caudal rami ( Fig. 1 View FIGURE 1 B–C) about 25x20 µm (length measured along outer margin); covered by overlapping epicuticular scales; armed with 6 setae, seta I absent, setae II and VII slightly offset onto dorsal surface.

Antennule ( Fig. 1 View FIGURE 1 D) 21-segmented, about 230 µm long. Segmental homologies (expressed segment given first followed by ancestral segments in brackets) and setation pattern 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)-7, 10 (XIII)-1+spine, 11 (XIV)-2, 12 (XV)-2, 13 (XVI)-2, 14 (XVII)-2, 15 (XIII)-2, 16 (XIX)-2, 17 (XX)-2, 18 (XXI)-2+ae, 19 (XXII)-2, 20 (XXIII-XXIV)-4, 21(XXV-XXVIII)-7. All setae smooth.

Antenna ( Fig. 1 View FIGURE 1 E) biramous, 170µm long, including terminal claw. Coxa and basis unarmed; basis ornamented with fine spinule rows. Exopod 1-segmented, with one small subterminal seta and one long terminal seta. Endopod 3-segmented; proximal segment elongated; middle segment protruded distally on medial side but articulating with distal segment proximally on lateral side, bearing one distal seta; distal segment with distal claw (35 µm long), one subterminal and one terminal seta, all setae smooth.

Siphon, about 120 µm long, reaching to insertion of maxillipeds.

Mandible ( Fig. 2 View FIGURE 2 A) comprising stylet-like gnathobase and slender 2-segmented palp. Stylet located in oral cone formed by anterior labrum and posterior labium, with 5 large teeth subapically. First segment of palp ornamented with distal spinules; second segment armed with 2 apical setae, the shorter smooth and the longer pinnate.

Maxillule ( Fig. 2 View FIGURE 2 B) bilobed; praecoxal endite (inner lobe, 45x15 µm) larger than palp (outer lobe, 16x7 µm). Praecoxal endite armed with 4 barbed distal setae, ornamented with spinules on lateral margin and a row of long setules medially. Palp armed with 4 barbed, distal setae.

Maxilla ( Fig. 2 View FIGURE 2 C) 2-segmented; with unarmed coxa. Claw-like basis recurved in its end; armed with a few setules on the proximal inner lateral margin.

Maxilliped ( Fig. 2 View FIGURE 2 D) 5-segmented, comprising short syncoxa, long basis and distal subchela consisting of 3 free endopodal segments armed with distal claw-like element. Syncoxa with one short seta distally. Basis with a spinule on medial inner margin. First endopodal segment bearing two short medial setae and one distal seta; second endopodal segment with one medial seta and third endopodal segment bearing curved terminal claw (45 µm long) plus additional apical barbed seta.

Swimming legs 1–4 ( Figs. 3 View FIGURE 3 A–D) biramous, with 3-segmented rami. Intercoxal sclerite present in legs 1–4, ornamented with patches of spinules in legs 1 and 2. Spine and seta formula as follows:

Coxae ornamented with spinule rows laterally in legs 3 and 4. Outer spines of exopodal segments in legs 1–4 bilaterally serrated. Lateral margins of exopodal segments in legs 1–3 with minute serrations; lateral margins of endopodal segments with rows of setules ( Fig. 3 View FIGURE 3 A–D). Second and third endopodal segments in legs 1–4 with a small beak-shaped spiniform process distally.

Fifth leg ( Fig. 1 View FIGURE 1 B) with protopod incorporated into somite and one outer seta displaced to dorsal surface. Free segment slender (50x20 µm), armed with one subterminal and two terminal smooth setae and ornamented with few spinules.

Sixth leg represented by paired opercular plates closing off gonopores on genital double somite; each armed with two smooth setae ( Figs. 1 View FIGURE 1 B; 4B).

Adult male: Unknown.

Etymology. The specific name tarifensis refers to Tarifa Island where the species was collected.

Remarks. With regards to the antennule, the species of the genus Asterocheres fall into two groups: females having a 18 to 20-segmented antennule and females with a 21-segmented antennule. The latter group contains a total of 20 species (Bandera & Conradi 2009) and can be subdivided into two subgroups: (1) species with a 1-segmented mandibular palp and (2) species with a 2-segmented mandibular palp. The new species described above belongs to the second subgroup. Together with Asterocheres tarifensis n.sp., 16 asterocherid species have a 21-segmented antennule in females and a 2-segmented mandibular palp: A. astroidicola Conradi et al., 2006 ; A. ellisi Hamond, 1968 ; A. flustrae Ivanenko & Smurov, 1997 ; A. hirsutus Bandera et al., 2005 ; A. jeanyeatmanae Yeatman, 1970 ; A. kervillei Canu, 1898 ; A. latus (Brady, 1872) ; A. lilljeborgi Boeck, 1859 ; A. lunatus Johnsson, 1998 ; A. reginae Boxshall & Huys, 1994 ; A. simulans (Scott T, 1898) ; A. suberitis Giesbrecht, 1899 ; A. tenerus (Hansen, 1923) ; A. tenuicornis Brady, 1910 ; A. uncinatus (Kritchagin, 1873) and A. urabensis Kim, 2004 . However, A. intermedius (Hansen, 1923) also has to be included since there is no available information about its mandibular palp. Asterocheres tarifensis n.sp. can be separated from A. ellisi , A. jeanyeatmanae , A. lilljeborgi , A. lunatus ; A. simulans , and A. reginae by its body shape. While these species have a dorsoventrally flattened prosome ( Marcus & Por 1960; Hamond 1968; Yeatman 1970; Ivanenko & Ferrari 2003; Johnsson 1998; Ivanenko 1997; Boxshall & Huys 1994), A. tarifensis shows an oval cephalothorax and a cylindrical urosome ( Fig. 1 View FIGURE 1 A). Like the majority of Asterocheres species, the new species possesses three terminal setae in the free segment of the fifth leg ( Fig. 1 View FIGURE 1 B). However, A. uncinatus and A. latus differ from this species by the possession of only two terminal setae (for A. uncinatus , see Marcus & Por 1960) or two terminal seta and one hyaline setule (not a genuine seta) in the exopod of this leg (for A. latus , see Bandera & Conradi 2009b). Asterocheres tarifensis n.sp. has a siphon which reaches up to the insertion of the maxillipeds, whereas A. astroidicola , A. hirsutus , A. intermedius and A. urabensis possess siphons which exceed this length ( Kim 2004; Bandera et al. 2005; Conradi et al. 2006; Bandera & Conradi 2009a). The new species is easily separated from A. tenuicornis , A. kervillei , A. suberitis and A. tenerus by the length of the caudal rami which is, almost 6 times longer than wide in A. tenuicornis , twice longer than wide in A. kervillei , slightly more than 1.5 times longer than wide in A. suberitis and only just longer than it is wide in A. tenerus , in comparison with that of A. tarifensis n. sp., in which the caudal rami is as long as it is wide ( Bandera & Conradi 2009a; b).

Although A. flustrae also possesses caudal rami as long as its width, some characteristics such as the two setae of the antennary exopod ( Fig. 1 View FIGURE 1 E), the inner lobe of the maxillule with four setae ( Fig. 2 View FIGURE 2 B), the absence of an aesthetasc on the maxilla ( Fig. 2 View FIGURE 2 C), the 5-segmented maxilliped ( Fig. 2 View FIGURE 2 D) and the two setae of the genital area separate A. tarifensis n.sp. from A. flustrae , since, A. flustrae has three setae on the antennary exopod; the inner lobe of the maxillule has five setae; the maxilla bears an aesthetasc on syncoxa; each genital area is armed with two elements, one seta and one spine and the maxilliped is 6-segmented (according to the illustrations of Ivanenko & Smurov 1997).

Host. Astroides calycularis is an azooxanthellate dendrophylliid colonial coral, typically inhabiting shallow waters down to a depth of about 30 m, and preferring shaded places and strong water movement ( Zibrowius 1980; 1995). This coral, protected by the Convention on International Trade in Endangered species of Wild Fauna and Flora (CITES), is essentially endemic to the south-western Mediterranean, with a few outliers beyond the Strait of Gibraltar in the west and the Straits of Sicily in the east.

The colonies of A. calycularis harbour an abundant associated fauna, including both mobile and sedentary species. At least two uncommon gastropods are now known to live and feed on this coral: Epitonium dendrophylliae Bouchet and Warén and the coralliophilid Babelomurex cariniferus (Sowerby) ( Richter & Luque 2004) . Various isopod species such as Carpias stebbingi (Monod) ; Cymodoce emarginata Leach ; C. truncata Leach , Dynamene edwardsi (Lucas) ; Gnathia illepida (Wagner) ; G. inopinata Monod ; G. venusta Monod , and G. v o r a x (Lucas) have also been recorded living on this coral ( Castellanos et al. 2003). Recently two copepod species have been described living in association with A. calycularis : the cyclopoid Doridicola helmuti Conradi, et al., 2006 ; and the siphonostomatoid Asterocheres astroidicola Conradi et al., 2006 . These species were found together with the siphonostomatoid Acontiophorus scutatus (Brady & Robertson, 1873) and an undetermined harpacticoid species ( Conradi et al. 2006). Furthermore, the collection of some specimens of Asterocheres mucronipes in association with this coral serves to redescribe the species and accommodate it into a new genus, Stockmyzon Bandera and Huys, 2008 ( Bandera & Huys 2008) .