Perinereis atlantica (McIntosh, 1885) McIntosh, 1885

Darbyshire, Teresa, 2014, Intertidal and nearshore Nereididae (Annelida) of the Falkland Islands, southwestern Atlantic, including a new species of Gymnonereis, ZooKeys 427, pp. 75-108 : 93-94

Taxon classification Animalia Phyllodocida Nereididae

Perinereis atlantica (McIntosh, 1885) comb. n. Figure 6

Nereis atlantica McIntosh, 1885: 219-221, Pl. XXXV, figs 1-3, Pl. XVIa, figs 10-11. - Pratt 1898: 16.

Nereis atlantica ?. - Hartman 1964: 99, Pl. XXX, figs 7-8.

Material examined.

St Vincent, Cape Verde Islands (NHMUK.1885.12.1.161), holotype, July 1873.

Description.

Examination of the holotype (Fig. 6 A–C), shows the description and illustrations by McIntosh to be quite accurate. The only refinements are as follows:

Body dorso-ventrally depressed, mostly of uniform width, gradually tapering in last 20-30 chaetigers to pygidium.

Paragnaths arranged as follows, all conical except for Area VI (Fig. 6 B–C): Area I = 1 large, Area II = 6-8, Area III = 8, Area IV = 15-16 arranged in 3-4 rows, Area V = 1 small, Area VI = 1 shield-shaped bar with rounded apex, Area VII–VIII = 3 rows with 6 (distal row), 9 (middle row) & 4 (proximal row) evenly-spaced cones, middle and proximal cones more flattened and blunt than those of the distal row. Jaws robust, dark brown with 4 teeth (Fig. 6B).

Dorsal ligule expanded posteriorly to a greater extent than figured by McIntosh but not as much as Perinereis falklandica .

Notochaetae all homogomph spinigers, neurochaetae homogomph and heterogomph spinigers and heterogomph falcigers (from observations of a limited number of chaetae, most broken so distribution between inferior and superior fascicles unknown). Falciger tips become shorter posteriorly but otherwise do not change in form along the body.

Pygidium terminal; 3 long, thin anal cirri of equivalent length to last 11 chaetigers (1 cirrus apparently lost as McIntosh’s original description states 4 anal cirri, 2 each side of anus). Pygidium and last 3 chaetigers with appearance of regeneration.

Remarks.

This species was described from a single specimen collected at Cape Verde Islands in the southeast Atlantic. McIntosh (1885) noted that the species appeared most closely related to Perinereis , however, the large, bar-shaped paragnaths characteristic of that genus were present in Area V not VI, Area VI being empty. He related the species most closely to Nereis floridana Ehlers, 1868, now Perinereis floridana (Ehlers, 1868) and would most likely have also placed Nereis atlantica into Perinereis if Perinereis floridana had already been placed there. The lack of notopodial falcigers would also now place it outside of Nereis . It is believed that the specimen is aberrant, with the large bars of Area VI here situated much closer together than would normally be expected and appearing to be in Area V instead (the aberration appears to be more than just an artifact of contraction). The additional cone behind one of the bars could be skewed out of position from Area V or may be an aberrant additional cone in Area VI (it is here assumed to be out of position from Area V due to an aberration). An additional sign of possible aberration is that of the 4 (currently 3) anal cirri on a regenerating pygidium. More material will be required from the type locality to determine the true form and validity of the species. Until then, Nereis atlantica is transferred to Perinereis based on the large, bar-shaped paragnaths and the lack of notopodial falcigers.

Since its description, the only other record of the species has been by Pratt (1898) from Hill Cove on West Falkland (southwest Atlantic) although Hartman (1964) cast doubt on the validity of this record due to the distance from its original locality. Unfortunately, both McIntosh and Pratt gave only general locality details for their specimens and no details of habitat or depth. However, as Pratt’s specimens generally came from shore or shallow water samples it is assumed that her Nereis atlantica were either intertidal or nearshore. Attempts to locate the specimens at Manchester (where she worked), Cambridge (where the other specimens she published on were loaned from) and the Natural History Museum, London have proved fruitless. The record from the Falkland Islands is therefore also considered doubtful in this paper. It is possible that, with Perinereis falklandica undescribed at that time and, as a student working on Bryozoa and not Annelida, Pratt mistakenly identified Perinereis falklandica as Nereis atlantica . Unfortunately, without the specimens no confirmation of this is possible. Certainly, aside from Pratt’s record, no other specimens like Perinereis atlantica have ever been reported from the Falkland Islands.

With the shield-shaped bars now re-described into Area VI, the species would fall into 'Group 1 A’ of Hutchings et al. (1991) along with Perinereis floridana : Perinereis species with 1 bar in Area VI and dorsal notopodial lobe not greatly expanded.

Habitat.

Unknown.

Distribution.

Cape Verde Islands,?Falkland Islands.