Ceratocephale Malmgren, 1867

Ceratocephale Malmgren, 1867

Ceratocephale sp. 1

Voucher. LOLIGO: station L11FB.

Diagnosis.  Voucher specimen posteriorly incomplete 4.0 mm long and 1.0 mm wide (including parapodia), for 22 chaetigers. Alcohol preserved material, pale yellow in colour with golden setae and black aciculae. Prostomium rectangular, with pair of long, thin, triangular antennae lying closely against palps. Palps tapering, about the same length as antennae, with large palpophores. Eyes absent.  Two pairs of tentacular cirri with the longest extending to the beginning of chaetiger 3.  Pharynx inverted (not observed).

Parapodia bi-ramous, with notopodia slightly shorter than neuropodia. Dorsal cirrus slender tapering, longer than other parapodia appendages, their cirrophores expand, becoming fully expanded from around chaetiger 10. Notopodia with elongate prechaetal ligule and short, blunt postsetal lobe. Neuropodia (mid body) with bluntly rounded postchaetal lobe and elongate digitiform precheatal ligule. Ventral neuropodial ligule conical (subequal in length to primary ventral cirrus). Ventral cirri bifid throughout (present from chaetiger 1 till end of the fragment), with ventralmost cirri about half the length of primary cirri.

Notopodial chaetae arranged in 2 bundles on either side of prechaetal ligule. Neuropodial chaetae similarly arranged. Chaetae consist of mostly homogomph and few sesquigomph spinigers with finely serrated blades. Chaetae far more numerous on chaetigers 3-9 than on subsequent chaetigers; chaetae straw coloured.  Narrow transverse dorsal ridges connecting the notopodia present from chaetigers 14 till end of the fragment. The rest of the body and pygidium uknown.

Remarks. Genus Ceratocephale is characteristic by bifid ventral cirri (this character is also shared with genus Gymnonereis, which additionally also has bifid dorsal cirri). The appearance of the double ventral cirrus together with characters such as – presence or absence of eyes, appearance of expanded dorsal cirriophores, presence of dorsal ridges, form of chaetae and characters derived from proboscis. The differences appear to be rather subtle (see Table 1. for comparison).  Currently we prefer to assign Falkland Island specimens to morphoscpecies Ceratocephale sp. 1, as differences from known species were observed as are summarised in Table 1. below.

Table. 1 Comparison of some known species of Ceratocephale with Ceratocephale sp. 1 from Falkland Islands (adapted from Hutchings and Reid, 1990).

ho=homogomph; ses=sesquigomph; sp=spingers; f=falcigers