Cryptopontius expletus, Neves, Elizabeth & Johnsson, Rodrigo, 2008

Neves, Elizabeth & Johnsson, Rodrigo, 2008, Three new species of Artotrogidae (Copepoda, Siphonostomatoida) from the southeastern coast of Pernambuco State, Brazil, Zootaxa 1932, pp. 47-60 : 56-60

Cryptopontius expletus sp. nov.

( Figs 8–10 )

Material examined. Holotype Ψ ( MNRJ 12912) and 7 Ψ paratypes ( MNRJ 12923), ex algae, Santo Aleixo Island, Serinhaem, Pernambuco, leg. P.S. Young, 15 March, 1995.

Description of female. Mean body length (excluding caudal setae) 1.19 mm (1.17–1.20 mm), mean body width 670 µm (661–682 µm) (based on 8 specimens). Body ( Fig. 8 a) cyclopiform, dorsoventrally flattened with moderately enlarged prosome and cylindrical urosome. Pedigerous somite 1 totally fused with cephalosome. Cephalothorax and pedigerous somites 2–4 with pointed epimera. Pedigerous somite 4 partially conceals pedigerous somite 5 and genital double-somite. Prosome length:width ratio 1.3:1. Urosome composed of 5 somites (first urosomite excluded in Fig. 8 b). Genital double-somite 155 µm long, length:width ratio 0.7:1, with well developed posterolateral expansions and serrated posterior margin. Three postgenital somites wider than long (48 × 107 µm, 34 × 100 µm, 72 × 97 µm, respectively). First and second postgenital somites with serrated posterior margin. Ratio of prosome length to urosome 2.7:1. Caudal rami ( Fig. 8 b) elongate, 66 × 41 µm, armed with 6 setae (seta I absent). Length of setae II–VII 34, 114, 335, 462, 190, and 90 µm, respectively; setae III–VI plumose, setae II and VII naked.

Antennule ( Fig. 8 c) slender, 327 µm long (not including setae), consisting of 8 segments. Length of segments: 62, 23, 73, 36, 11, 29, 37, and 55 µm, respectively. Setation as follows: 1, 2, 8, 4, 2, 2, 3, 8+ae. All setae simple; aesthetasc 148 µm long. Antenna ( Fig. 8 d) 151 µm long (including distal claw-like seta); basis 53 µm long. Exopod 1-segmented, 8 Μm long, with 2 distal setae; plumose seta extends beyond first endopodal segment. Endopod 2-segmented; first segment 25 µm long, unarmed; second segment 36 µm long, terminally covered with setules, and armed with proximomedial plumose seta and 3 apical setae (2 spiniform, 1 plumose).

Oral cone ( Fig. 8 a) 420 µm long, reaching insertion of P1. Mandibular stylet ( Fig. 8 e) with 8 distal teeth; mandibular palp absent. Maxillule ( Fig. 9 a) bilobed; both lobes elongated. Inner lobe 101 µm long, with 1 plumose and 1 naked setae and row of setules along inner margin. Outer lobe 70 µm long, with 2 long setae distally and row of setules along lateral margin. Maxilla ( Fig. 9 b) with 286 µm long syncoxa and 262 µm long, distally curved claw; claw unarmed. Maxilliped ( Fig. 9 c) 512 µm long, 4-segmented; syncoxa 68 µm long, with short distomedial seta; basis 171 µm long, with short distomedial seta and setules along outer margin. Endopod 2-segmented; segments 104 and 59 µm long, respectively. First endopodal segment armed with outer and inner setae. Second endopodal segment with 2 setae and 111 µm long, recurved claw.

P1-P3 ( Figs 9 d–e, 10a) biramous and trimerous. P4 ( Fig. 10 b) without endopod. Armature formula for P1- P4 as follows:

All coxal and basal setae naked. Outer margin of P2–P4 exopods serrated.

P5 ( Fig. 10 c) composed of protopodal segment fused to somite and free exopodal segment. Protopod with lateral naked seta. Exopod small, 23 µm long, with 3 distal naked setae. P6 ( Fig. 8 b) represented by naked seta on posterior margin of genital-double somite.

Male. Unknown.

Etymology. The specific name refers to the Latin word “ expletus ” which means complete and perfect, alluding to the fact that the new species possesses more elements on its legs than any known congener.

Remarks. Although C. expletus sp. nov. and C. aesthetascus sp. nov. were found in the same locality, they are not conspecific because: 1) each species occupies a different microhabitat (algae vs. sponge); 2) the number of antennulary segments proximal to fused ancestral segments IX–XII in C. aesthetascus sp. nov. and C. expletus sp. nov. is 7 and 3, respectively; 3) the relative lengths of the exopod and distal endopodal segment of the antenna between these two taxa are not congruent; 4) the mandibular stylet of C. aesthetascus sp. nov. and C. expletus sp. nov. bears 7 and 8 teeth, respectively; 5) the curved maxillary claw of C. aesthetascus sp. nov. is armed with 2 small setae instead of unarmed as in C. expletus sp. nov.; 6) the endopod of the maxilliped is composed of 3 segments in C. aesthetascus sp. nov. instead of 2 as in C. expletus sp. nov.; 7) the armature of the third exopodal segment of P1 differs between them (5 inner setae in C. expletus sp. nov. vs. 4 in C. aesthetascus sp. nov.); and 8) an inner coxal seta is present on P 4 in C. expletus sp. nov. but absent in C. aesthetascus sp.nov. None of these features can be attributed to sexual dimorphism.

The 8-segmented female antennule of C. expletus sp. nov. is a characteristic shared with C. ignotus (Brady, 1910) , C. latu s Nicholls, 1944, C. minor Stock, 1965 , C. ricinius Malt, 1991 , C. donghaensis Kim, 1996 , C. quinquesetus Kim, 1996 and C. digitatus Kim, 1996 . The new species can be distinguished from C. digitatus by the absence of P4 endopod ( Kim 1996). Cryptopontius expletus sp. nov. differs from C. quinquesetus , C. minor , C. ignotus , C. latus and C. ricinius by having 8 rather than 7 elements on the third exopodal segment of P1 ( Nicholls 1944; Eiselt 1961; Stock 1965; Kim 1996). Cryptopontius expletus sp. nov. differs from C. donghaensis by having 6 rather than 5 elements on the third endopodal segment of P1 and 3 rather than 2 setae on the free exopodal segment of P5 ( Kim 1996).

Figures

FIGURE 8. Cryptopontius expletus sp. nov., female holotype (MNRJ 12912). (a) habitus, dorsal view; (b) urosomites 2 – 5, dorsal; (c) antennule; (d) antenna; (e) distal end of mandibular stylet. Scale bars: a = 250 µm; b – c = 100 µm; d – e = 25 µm.

FIGURE 9. Cryptopontius expletus sp. nov., female holotype (MNRJ 12912). (a) maxillule; (b) maxilla; (c) maxilliped; (d) P 1; (e) P 2. Scale bars: a = 25 µm; b – e = 100 µm.

FIGURE 10. Cryptopontius expletus sp. nov., female holotype (MNRJ 12912). (a) P 3; (b) P 4; (c) P 5. Scale bars: a – b = 100 µm; c = 25 µm.