Phyllodicola Delamare Deboutteville & Laubier, 1961

Boxshall, Geoff A., O’Reilly, Myles, Sikorski, Andrey & Summerfield, Rebecca, 2019, Mesoparasitic copepods (Copepoda: Cyclopoida) associated with polychaete worms in European seas, Zootaxa 4579 (1), pp. 1-69 : 28

Genus Phyllodicola Delamare Deboutteville & Laubier, 1961

Syn: Phyllocola Delamare Deboutteville & Laubier, 1960 (preoccupied)

Non Phyllocola Gistl, 1848 (Coleoptera)

Diagnosis. Adult female body (ectosoma) highly transformed, unsegmented, attached via short broad stalk to endosoma embedded within host. Ectosoma ovoid, about 400 to 900 µm in length ( Fig. 9A ), varying with reproductive state (cf. Fig. 13 A–C). Anus lacking. Paired genital apertures present, located on ventral surface anterior to mid-level; each aperture with two strong tooth-like elements ( Fig. 11B ). Paired copulatory pores (arrowed in Fig. 11B ) located on ventral surface adjacent to genital apertures. Egg strings elongate, with large eggs attached to central axial filament (cf. Fig. 13A ). Antennule ( Fig. 9C ) located dorsal to stalk, unsegmented, tapering towards tip, armed with array of stout setal elements along anterior and apical margins. Antenna ( Fig. 11D ) with broad basal segment bearing, posteriorly, robust, indistinctly 2-segmented endopod armed with 4 apical claws; basal segment produced anteriorly into lobe ornamented with minutely spinulose lamellae. Maxilliped ( Fig. 11E ) subchelate, comprising robust basal segment plus subchela consisting of long proximal segment and compound apical segment armed with 3 strong claws on distal margin. Stalk originating on underside of ectosoma in oral region. Endosoma taking form of two elongate rootlets penetrating body cavity of host, with several short digitiform processes originating around base of primary rootlets. Male unknown. Nauplius lecithotrophic, with nauplius eye.

Type species: Phyllodicola petiti (Delamare Deboutteville & Laubier, 1960)

Remarks. The development of the ectosoma can be reconstructed by reference to Laubier (1961): in the very early stage a vestigial abdominal process is still visible ( Laubier 1961: Fig. 3b ) but this is absorbed during subsequent development so the mature adult female has an ovoid ectosoma lacking any trace of a defined abdomen.

We interpret the uniramous antenna slightly differently from Laubier (1961). We interpret the ramus as ornamented with claws that are flattened and very broad at the base so they are rather lamellate in form. The compound apical segment of the maxilliped shows bands of thickening ( Fig. 11E ) which appear to correspond to at least two incompletely expressed segments. It is this segmentation pattern that provides the evidence supporting the interpretation of these limbs as maxillipeds rather than maxillae, since the maxilla exhibits a maximum of two expressed segments in all members of the poecilostome lineage within the order Cyclopoida ( Huys & Boxshall 1991) .

Figures

FIGURE 3. Herpyllobius arcticus Steenstrup & Lütken, 1861 from Harmothoe antilopes. A, habitus of ovigerous female with male attached (arrowed), lateral view showing position of cement glands (dotted); B, ectosoma of female, posterior view showing attachment site of male (arrowed) dorsal to genital apertures; C, adult male containing paired spermatophores. Scale bars: A, 0.5 mm, B, 250 µm, C, 100 µm.

FIGURE 9. Eurysilenium sp. from Harmothoe fragilis. A, ectosoma of female, ventral showing male attached between ventrally-located genital apertures of female; B, adult male, dorsal. Scale bars: A, 0.5 mm, B, 100 µm.

FIGURE 11. Phyllodicola petiti (Delamare Deboutteville & Laubier, 1960), female. A, ectosoma and proximal part of endosoma; B, genital apertures and copulatory pores (arrowed); ventral; C, antennule; D, antenna; E, maxilliped. Scale bars: A, 200 µm, B, 100 µm, C–E, 25 µm.

FIGURE 13. Cyclorhiza megalova Gotto & Leahy, 1988, female. A, spent adult female with single egg string attached, ventral view showing egg string comprising central axis and large developing eggs plus empty egg membranes (arrowed); B, adult female showing length of intact egg sac relative to ectosoma length; C, adult female with ectosoma full of developing eggs; D, developing ectosoma; E, early stage female, lateral view showing paired limbs, genital apertures and finely striated dorsal surface integument; F, detail of developing female anterior end, showing spinules (arrowed) located lateral and medial to genital aperture; G, antennule; H, antenna; I, maxilliped. Scale bars A, C–D, 200 µm, B, 1 mm, E, 50 µm, F, 100 µm, G–I, 25 µm.