Drilonereis cf. logani Crossland, 1924

Zanol, Joana & Ruta, Christine, 2015, New and previously known species of Oenonidae (Polychaeta: Annelida) from Lizard Island, Great Barrier Reef, Australia, Zootaxa 4019 (1), pp. 745-772 : 758-760

Drilonereis cf. logani Crossland, 1924

( Fig. 7 )

Drilonereis logani Crossland, 1924: 64 –70

Drilonereis .— Gallardo 1968: pl. 37; Mohammad 1973: 16 –17; Kirkegaard 1995: 52.

Material examined. AM W.44971, MI QLD2440 (1), fixed in formalin, few median chaetigers fixed in ethanol.

Measurements. Table 2.

Description. Live specimens whitish with internal red hues due to blood ( Fig. 7 A). Specimens fixed in formalin anterior beige ( Fig. 7 B–D), median region dark brown.

Body long, slender, widest until chaetiger 20, about the same width along the remaining of the fragment ( Fig. 7 A); dorsoventrally rounded, dorsal side as convex as ventral. Chaetigers longer and narrower towards posterior region, some longer than wide, all with a transverse median groove, appearing to be double ringed.

Prostomium longer, narrower and as half as deep as peristomium; triangular, anteriorly tapering, dorsoventrally flattened; median longitudinal groove present on dorsal and ventral sides, dorsal groove extends to first peristomial ring ( Fig. 7 B, D). Eyes absent. Peristomium double ringed, first around 1/3 longer than second; longer dorsally than ventrally ( Fig. 7 B–D). Margin between prostomium and peristomium inconspicuous dorsally ( Fig.7 B).

Mandibles absent. Maxillae dorsal carrier narrower at anterior end than beginning of the furcula ( Fig. 7 E); ventral carrier tapering; shorter than half of dorsal carriers. Maxillae with four pairs of plates symmetrical regarding shape and size ( Fig. 7 E–F). MxI falcate with 4 conspicuous teeth at the base and around 25 minute teeth at the inner surface of the fang ( Fig. 7 F). Maxillary formula: (1,4) + (1,4) (minute teeth not included), 6 + 7, 1 + 1, 1 + 1.

Parapodia absent in 9 anteriormost chaetigers, inconspicuous in anterior region, becoming more conspicuous towards posterior end. Pre-chaetal shorter than chaetal lobe. Post-chaetal tapering to digitiform, twice as long as chaetal lobe.

Notopodial cirri absent. Neuroaciculae 3 present; mucronate. Chaetae present in all chaetigers, but inconspicuous in anteriormost. Limbate capillary present in supra and subacicular position; 3–4 present per neuropodia ( Fig. 7 G). Acicular spine chaeta equally tapering on both sides or straight on one side and tapering on the other, in neuropodia ventralmost position, longer than post-chaetal lobe ( Fig. 7 H).

Pygidium not observed.

Remarks. This specimen differs from the original description in the length of the acicular spine chaetae relative to the post-chaetal lobe and shape of maxillae ventral carrier. Acicular spine chaetae are as long as postchaetal lobe, while they are longer in the specimen examined here. Most chaetae along the body of D. logani types were broken ( Crossland 1924), thus number, shape and length of chaetae may vary from that described. In one of the types, maxillae ventral carrier tapers anteriorly and posteriorly and has rounded lateral margins, differing from the specimen examined here, which has ventral carrier widest at the anterior end and evenly tapering to a round posterior end. To the best of our knowledge, this is the first record of this species as endoparasite.

The wide distribution of this species as well as the differences between the specimen examined here and the original description may suggest that there is more than one species identified as D. logani . However, with the current poor knowledge on the species, on its biology and on morphological characters variation within the genus, we are not confident that the observed differences are enough to describe a new species. Therefore, we identify the specimen as D. cf. logani . In order to clearly understand the distribution range and intraspecific variation of the species, further studies using morphological and molecular tools are necessary.

Biology. Free-living and endoparasite of polychaetes.

Habitat. Inside an Arenicolidae gen. sp. collected in sand mud sediment, 14 m deep.

Distribution. Coral Sea, Ocean Pacific off Australia and New Zealand, Persian Gulf, Red Sea, South China Sea, West Indian Ocean.

Figures

FIGURE 7. Drilonereis cf. logani Crossland, 1924. A. Whole body of live specimen in host; B. Anterior end, dorsal view; C. Anterior end, ventral view; D. Anterior end, lateral view; E. Maxillae and carriers, MxI, ventral and dorsal carriers broke during mounting, arrow at beginning of the furcula; F. Maxillae, MxI broke during mounting, G. Left parapodium 135; H. Chaeta acicular spine, left parapodium 135. A – H, AM W. 44971.