Achelidelphys reducta ( Lafargue and Laubier, 1977 ) Lafargue and Laubier, 1977

Boxshall, Geoff A. & Marchenkov, Andrey, 2007, A revision of the Brementia - group of genera (Copepoda: Notodelphyidae), with descriptions of a new genus and four new species, Zootaxa 1459, pp. 37-68 : 63

Achelidelphys reducta ( Lafargue and Laubier, 1977) n. comb.

Syn: Syndelphys reducta Lafargue and Laubier, 1977

Material examined: Holotype female, reg. no. ZMA CO. 106.632.

Differential Diagnosis: Body highly transformed, stellate in appearance due to laterally-directed legs; segmentation indistinct with segmental boundaries marked by superficial folds. Cephalosome with broad convex frontal margin merging laterally into large antennulary lobes ( Fig. 12 E). Rostrum not defined. Post-rostral median lobe absent. Labrum forming rounded hemispherical lobe. Lateral margin of cephalosome not produced into ridge-like swellings. Antennomedial swellings also absent. Metasome truncated, with urosome hardly extending posterior to origin of leg 4. Legs 1–4 transformed, originating laterally, each occupying entire margin of somite; produced laterally. Mid-ventral metasomal processes between legs lacking. Urosome reduced but apparently 2-segmented, located terminally; incorporating caudal rami ( Fig. 12 F). Surface of body, labrum, cephalosomic processes, and legs densely ornamented with surface setules.

Antennules represented by large, rounded lobe on either side of strongly convex frontal margin of cephalosome. Oral region lacking any trace of mouthparts. Legs 1 and 2 biramous; rami represented by unsegmented, rounded lobes; exopodal lobe laterally-directed, with broad base, carrying smaller endopodal lobe ventrally. Legs 3 and 4 uniramous, each comprising short, posterolaterally-directed lobe representing exopod. Exopodal lobes of legs 3–4 each housing internally expansion of uterus, containing eggs visible through body wall. Leg 5 absent.

Body length of female approximately 3.05 mm. Male unknown.

Remarks: This species is characterised by the strongly convex frontal margin of the cephalosome lacking a rostrum, combined with the loss of the endopodal lobe of leg 3. The phylogenetic analysis also places this species within the Achelidelphys -group ( Fig. 14 ) and does not support the retention of Syndelphys as a separate genus. Achelidelphys reducta ( Lafargue and Laubier, 1977) n. comb. is placed as the sister species of Achelidelphys stellata ( Lafargue and Laubier, 1977) n. comb. in the analysis primarily because they share the derived, convex form of the frontal margin of the cephalosome.

Figures

FIGURE 12. Achelidelphys reducta (Lafargue and Laubier, 1977) n. comb., holotype female (ZMA CO. 106.632). A, Habitus, ventral; B, Cephalosome, dorsal; C, Tip of exopodal lobe of leg 1, showing surface ornamentation. Achelidelphys stellata (Lafargue and Laubier, 1977) n. comb., holotype female (ZMA CO. 106.630). D, Cephalosome, dorsal; E, Tip of antennulary lobe, showing cluster of setae representing apex of limb; F, Urosome, dorsal; G, Post-rostral lobe, ventral view with surface removed showing internal support network of fibres. Scale bars: A – B = 500 μm, C = 100 μm, D = 200 μm, E – G = 100 μm.

FIGURE 14. Majority rule consensus tree showing estimated relationships between genera of Brementia - group with the family Notodelphyidae. The tree is the consensus of 10 equally parsimonious trees (branch length = 34). Values given above line are bootstrap values. Numbers below the line indicate the characters supporting the main clades. * Anoplodelphys incertae represents three taxa: A. incertae, A. galli and A. cf. galli, all of which have identical scores for the characters used in the analysis. Similarly, Achelidelphys chengae also represents Achelidelphys papuensis n. sp. which has identical scores for the characters used.