Intertidal and nearshore Nereididae (Annelida) of the Falkland Islands, southwestern Atlantic, including a new species of Gymnonereis

Abstract The intertidal and nearshore Nereididae of the Falkland Islands are detailed and a new species of Gymnonereis described. The new species, Gymnonereis tenera sp. n., is the first record of the genus for the Falkland Islands. It is, so far, only known from a few intertidal locations in fine and muddy sands. Main distinguishing characters are: jaw teeth absent (in adults), 3 papillae in Area V–VI, falcigers absent, second ventral cirrus present throughout. Nereis atlantica McIntosh, 1885, known only from the description of a single specimen and one doubtful record from the Falkland Islands, is reviewed and transferred to Perinereis on the basis of the presence of shield-shaped bars in Area VI of the proboscis and the absence of notopodial falcigers. A key to all seven species discussed is provided.


Introduction
The Nereididae is one of the largest polychaete families (Hutchings et al. 2000) and, intertidally, one of the most widespread and frequently encountered (Wilson 2000). Although not much literature exists on the intertidal polychaetes of the Falkland Islands, at least one species of Nereididae is recorded in each of the three papers (Pratt 1898(Pratt , 1901Fauvel 1916) published. Other records of Falkland Islands Nereididae have been from Antarctic/Southern Ocean research cruises that have also taken samples among and around the islands (Ramsay 1914;Monro 1930Monro , 1936Hartman 1953Hartman , 1967. In all, eight species of nereidid, in six genera, have previously been recorded from stations listed as being within the Falkland Islands region. However, two of these species, Platynereis australis (Schmarda, 1861) and P. magalhaensis Kinberg, 1865 have been controversially synonymized (e.g. Benham 1909Benham , 1921Hutchings and Reid 1990) or kept separate (e.g . Fauvel 1916;Augener 1932;Hartman 1953Hartman , 1964 many times historically. Most recently, Read (2007) maintained both names pending investigation of the epitokous stage of P. magalhaensis to help resolve the issue. All but one record (Ramsay 1914) of Platynereis for the islands are as P. magalhaensis and this name is therefore retained in this paper with a discussion of the current situation. Platynereis australis is considered unlikely to occur around the islands, hence a description is not included.
Only species that have previously been recorded from Falkland Islands samples taken in less than 30 m (where diving and shallow survey work are most likely to take place) are considered in this paper. For this reason, Nicon maculata Kinberg, 1865 is also excluded as it has not been recorded from less than 129 m in the area (Monro 1936;Hartman 1953Hartman , 1967. Eunereis patagonica (McIntosh, 1885), Nereis atlantica McIntosh, 1885 and Nereis eugeniae (Kinberg, 1865) were not collected by the survey but are included because they have previously been recorded from shallow depths and could feasibly be recorded from shallow samples taken in the area. The descriptions and reports of each species are considered and details specific to the Falkland Islands reported. Nereis atlantica McIntosh, 1885 is reviewed and newly transferred to Perinereis Kinberg, 1865. Most of the nereidids collected were found in mainly coarse or hard habitats, however, a new species of Gymnonereis Horst, 1919,a genus not previously recorded from Falkland Island waters, was identified from a small number of localities where it was almost entirely confined to intertidal, fine and muddy sands. Gymnonereis is a small genus of only six recognized species: G. sibogae Horst, 1918 (type locality: Strait of Makassar, Indonesia), G. crosslandi Monro, 1933 (type locality: Gorgona Island, Colombian Pacific), G. fauveli Hartmann-Schröder, 1962 (type locality: San Julián, Argentina), G. phuketensis Hylleberg & Nateewathana, 1988 (type locality: Andaman Sea, Thailand), G. minyami Hutchings & Reid, 1990 (type locality: Victoria, South Australia) and G. yurieli Hutchings & Reid, 1990 (type locality: Queensland, Australia). All members of the genus lack paragnaths, having only soft papillae on the oral ring and all, except G. crosslandi, exhibit highly vascularized dorsal cirrophores on median chaetigers. The new species is distinguishable from the other members of the genus using combinations of characters detailing the presence or absence of jaw teeth, falcigers and enlarged dorsal cirrophores, the number and distribution of the oral ring papillae, the occurrence of accessory dorsal cirri and the relative lengths of the neuropodial lobes.
A key to the seven species of Nereididae recognized from the near shore (< 30 m) waters of the Falkland Islands is provided.

Terminology
The parapodia of the Gymnonereidinae are more complex than those of the Nereidinae and a diagram is provided in Figure 1 to compare and standardize the terminology used in this paper when describing the different species. In reference to Gymnonereis, the terminology used by Hutchings and Reid (1990) has been mostly adopted, with some modification according to Santos et al. (2005), and is detailed further in the Remarks for that section.
The terminology used to describe paragnath forms was reviewed by Bakken et al. in 2009 and has been applied here also. Where necessary, generic diagnoses have been emended to reflect this, with changes highlighted in italics.

Methods
In 2011 and 2013, intertidal and diving survey work was undertaken around the Falkland Islands, covering the two main islands, East and West Falkland, as well as some of the smaller outer islands. Specimens were collected by a variety of methods on the shore and by SCUBA diving. Intertidal habitats were investigated by digging and collecting specimens by hand, by sieving sediment through a 0.5 mm sieve, turning over rocks and removing attached tubes, splitting open rock crevices and by inspecting algal holdfasts. Sampling while diving involved scraping epifaunal turf off rocks, turning over rocks and removing attached tubes, and taking sediment samples that would later be sieved as above.
Specimens were relaxed with a 7% magnesium chloride solution where possible and then fixed with 4% formaldehyde in seawater. After a period of at least 2 days, animals were rinsed with freshwater and preserved in 80% industrial methylated spirits with 2% propylene glycol added.
Morphological examinations and measurements were made using a Nikon Eclipse E400 binocular microscope and a Nikon Labophot-2 compound microscope. Microscope photographs were taken using AutoMontage™ software.
The holotype and most paratypes of Gymnonereis tenera sp. n. are accessioned in the zoological collections of National Museum Wales (NMW.Z). Paratypes are also deposited in the Australian Museum (AM), Natural History Museum, London (NHMUK), National Museum of Natural History, Smithsonian Institution, Washington D.C. (USNM) and the Zoological Museum, Hamburg (ZMH). All other specimens are accessioned in the National Museum Wales collections.
Eversible pharynx with jaws having cutting edge smooth or serrated, with papillae on the oral ring. Notopodia with accessory dorsal cirri attached to dorsal cirrophores in anterior region only, with prechaetal lobes and short, rounded postchaetal lobes. Median segments with dorsal cirrophores greatly elongated and highly vascularized (except in G. crosslandi) and lacking accessory cirri. Dorsal transverse ridges present or absent. Chaetae homogomph or sesquigomph spinigers and homogomph or sesquigomph falcigers may be present. Chaetae very numerous in anterior chaetigers.
Remarks. Hutchings and Reid (1990) used the term 'sesquigomph', in a review of Australian Gymnonereidinae, to describe those chaetae that have a 3:2 ratio between the boss and opposing prong of the shaft. Such chaetae were referred to as 'slightly hemigomph' by Fauchald (1977) or 'slightly heterogomph' by Hylleberg and Nateewathana (1988) in their descriptions of Gymnonereis. Terminology referring to the additional dorsal (=accessory dorsal) cirrus and ventral (=double ventral) cirri follow that of both Hutchings and Reid (1990) and Santos et al. (2005) in the first instance but only Santos et al. (2005) in the second. Finally, the parapodial projections referred to as 'prechaetal ligules' in both Hylleberg and Nateewathana (1988) and Hutchings and Reid (1990) are here termed prechaetal lobes, after Santos et al. (2005), who defined notopodial projections supported by aciculae as lobes and those without aciculae as ligules and found notopodial ligulae to be absent in Gymnonereis. This definition has also been applied here to the previously-termed 'neuropodial prechaetal ligules', referred to here as neuropodial prechaetal lobes (Fig. 1). Body depressed dorso-ventrally, widest anteriorly on chaetigers 8-10 (more pronounced in smaller specimens), then mostly uniform in width before tapering posteriorly. Colour pink/orange or grey/white in alcohol with black aciculae. Neurochaetae and subacicular notochaetae dark golden in anterior chaetigers, supracicular chaetae pale amber; all chaetae pale amber from chaetiger 14. Live animals bright red on each side of body, including the parapodia, in region of vascularized, enlarged cirrophores; rest of body often with bright white dorsal bands centrally either side of central blood vessel from end of vascularized cirrophore region, fading in posterior. Where white colouration absent, body transparent, coloured only by visible gut and blood vessels. Methyl green staining of preserved animals shows glandular areas on tips of cirri and parapodial lobes but not on cirrophores or main body. Cuticle very soft when animals alive as well as post-fixation, body breaks easily when handled. Prostomium with 2 pairs small, black (dark red when alive) eyes, often difficult to discern when preserved (Figs 2A, 9A). Anterior pair smaller, more laterally placed than posterior pair; crescent-shaped with additional small spot in far corners. Posterior pair darker, rounded. Prostomium subrectangular with deep cleft between antennae ( Fig. 2A). Palps with large squat palpophores and short triangular palpostyles (0.4 mm long, 0.27 mm wide). Antennae equal length to or slightly longer than palps, more slender in form. Four pairs tentacular cirri, ventral pairs of equal length, 2/3 to 1/2 length of dorsal pairs; 2 nd pair dorsal tentacular cirri marginally longer than 1 st pair, reaching to chaetiger 4.

Gymnonereis tenera
Peristomium dorsally more narrow than following segments. Jaws with smooth edges, teeth absent ( Fig. 2A-B). Oral ring with triangular papillae arranged as follows ( Double ventral cirri present throughout ( Fig. 2C-I), branches unequal, ventral branch reducing in size posteriorly. Dorsal branch 1.5 times as long as ventral branch in anterior region, 4-5 times as long posteriorly.
Chaetiger 3 ( Fig. 2D) with basally swollen, digitiform notopodial prechaetal lobe twice as long as broadly rounded notopodial postchaetal lobe; acicular lobe 1/4 length of latter. Notochaetae in 2 unequal bundles, arranged as a smaller semicircle above and larger semicircle below the notopodial prechaetal lobe. Neuropodium as for chaetiger 1, ventral ligule of same size and shape as neuropodial prechaetal lobe. Neurochaetae in 2 semicircular fascicles of greater density than notochaetae. Superior fascicle arranged around neuroacicular papilla with larger, inferior bundle ventral and posterior to neuropodial prechaetal lobe. Arrangement continues to start of vascularized cirrophores then number of chaetae reduces posteriorly, becoming bundles rather than semicircles. Greatest density of chaetae occurs in chaetigers 6-8.
Posteriorly, neuropodial prechaetal lobe reducing in size, ventral ligule even more so. Neuropodial postchaetal lobes also decrease in size proportionately, becoming more conical.
Noto-and neurochaetae consist of both homogomph and sesquigomph spinigers throughout, no falcigers observed. Accurate numbers of chaetae and distribution of homogomph versus sesquigomph chaetae on anterior chaetigers difficult to identify due to density.
Variation. Most characters varied with number of chaetigers and continued to change as the number increased. Accessory dorsal cirri were not observed on animals with less than 95 chaetigers (unless regenerating) although they were absent in one specimen of 103 chaetigers (62 complete specimens examined; 27 with less than 95 chaetigers, 35 with 95 or more chaetigers). As chaetiger number increases, additional anterior dorsal cirri have accessory cirri, with animals of more than 160 chaetigers with accessory dorsal cirri as far as chaetigers 10-14. The variation in this character means that it should not be used as diagnostic for the species on its own but only in conjunction with other characters.
The faint transverse ridges connecting parapodia were mostly visible from chaetiger 11 to 15 or 16 but were occasionally observed as far back as chaetiger 20 on the largest specimens.
Determination of the start and end of the expanded cirrophores was difficult, particularly the former, as the transition was not as abrupt as described for some species. The region generally occurred from around chaetigers 11-18 and continued to chaetigers 22-51 over the range of body sizes observed.
Presence and number of the oral papillae did not vary with size although papillae were occasionally lost and a single specimen was identified with 4 papillae in Area V-VI. Relative length of tentacular cirri was also stable with the longest cirri always reaching to chaetiger 4 in all body sizes.
Although jaw teeth were absent in the majority of specimens, juveniles of less than 80 chaetigers (jaws of 26 specimens were examined including 12 juveniles of 33-80 chaetigers in size) were found to have 4-5 small teeth on each jaw with jaws in larger animals becoming more roughly crenated until the largest jaws appeared almost completely smooth.
Etymology. The specific name tenera is derived from the latin adjective tener meaning 'soft, delicate', referring to the very soft nature of the worm when alive and its fragility when handled.

Chaetiger
Notochaetae Neurochaetae  1  0  30  3  20  90  9  39  108  20  19  40  30  20  40  50  10  12  100  8  19 Habitat. Found intertidally from mid to low shore in soft, fine, sand or mud sediments. Remarks. With 3 papillae in Area V-VI of the oral ring and the absence of jaw teeth, Gymnonereis tenera sp. n. can be distinguished from all other Gymnonereis species except for G. sibogae and G. phuketensis. Gymnonereis minyami and G. yurieli both have jaw teeth and only 1 papilla in each of Areas V and VI. Gymnonereis crosslandi and G. fauveli both lack jaw teeth but G. crosslandi has only 1 papilla in each of Areas V and VI, accessory dorsal cirri in only chaetigers 1 and 2 (chaetiger 1 to 12 or further in Gymnonereis tenera sp. n.) and no enlarged dorsal cirrophores, whilst G. fauveli has 5 papillae in Area V-VI and accessory dorsal cirri from chaetiger 3 (as opposed to chaetiger 1 in the new species).
Gymnonereis tenera sp. n. is most similar to both G. sibogae and G. phuketensis and can only be distinguished from each of these through combinations of characters. Although Hutchings and Reid (1990) listed G. sibogae as having sesquigomph falcigers, Horst (1918), in his original description, actually stated that "the neuropodial fascicle does not contain true setae falcigerae, but instead of these some faintly heterogomph setigerous bristles, with a short, lanceolate terminal piece", although his figures of the species (Horst 1924) did not illustrate this. Pettibone (1970) re-investigated and drew all of Horst's specimens and in her detailed description of the first two chaetigerous segments stated that "a few lower neurosetae of some anterior setigers may have blades which end bluntly" and this was figured accordingly (Pettibone 1970, fig. 30c-e). No such short, blunt chaetae were observed on any specimens of G. tenera sp. n. A more consistent character is that of the length of the anterior, neuropodial prechaetal lobe. In G. tenera sp. n., this lobe is consistently longer than both the neuropodial acicular and postchaetal lobes and of a similar length to the ventral ligule. In G. sibogae, the neuropodial prechaetal lobe (termed the prechaetal ligule by Pettibone 1970) is as long as or shorter than the postchaetal lobe and shorter than the ventral ligule for at least the first nine chaetigers (Horst 1924, pl. XXX, fig. 1;Pettibone 1970, fig. 30c-d, fig. 31a,d,e,f, fig. 33b), thereafter becoming only slightly longer. Unfortunately, all of Horst's specimens were incomplete with only 36-56 segments and the species does not appear to have been reported since, making further determination of differences between the two species difficult.
Apart from the character of presence or absence of jaw teeth, the new species is also very similar to G. phuketensis, although juveniles of the new species do have a small number of jaw teeth. Hutchings and Reid (1990) listed the character of jaw teeth as being present or absent for G. phuketensis, although the original description by Hylleberg and Nateewathana (1988) states only that they are present (adult specimens, no comments on the juvenile form) but that they can be weakly defined. Where jaw teeth are found in G. tenera sp. n., however, there are only up to 5 compared to 10 for G. phuketensis. Additionally, in G. phuketensis the dorsal cirrophores become "abruptly enlarged" from chaetiger 14 (Hylleberg and Nateewathana 1988) compared to a more gradual enlargement from chaetiger 12 for the new species and the second ventral cirrus is absent from around chaetiger 35 on G. phuketensis but present throughout on G. tenera sp. n.
Species builds tough-walled tubes coated in sand grains and other coarse particles. Remarks. The above description is based on McIntosh (1885), Monro (1930, 1936as N. hardyi), and Hartman (1953, 1967. However, there is some discrepancy between the original descriptions that can now be clarified following examination of the specimens from those accounts. All three authors agree that paragnaths are absent in Areas I and II and that Area VII-VIII has a single row of 7-8. In Area III, paragnaths are absent on the specimens of both Monro (1930Monro ( , 1936 and Hartman (1953Hartman ( , 1967, however there is a single conical paragnath present on McIntosh's specimen. Paragnaths are absent from Area IV on specimens of McIntosh and Monro as well as Hartman's (1953) Falkland Island specimens (SMNH 37894, 37902) but 3 conical paragnaths are present on her Uruguay specimens (SMNH 37888). The paragnaths described for Area V in Monro (1930Monro ( , 1936 are present in identical form on Hartman's (1953) Falkland Island specimens, although she placed them in Area VI in her description, however her Uruguay specimens from the same survey have 3 conical paragnaths in the same position. A single paragnath is present in Area V of McIntosh's specimen and it is assumed that the second paragnath has been lost or is absent through aberration as McIntosh states in his description that the single paragnath is "nearly, but not quite median".
It is clear that Hartman's (1953) Uruguay specimens are a different, currently unidentified species but that her Falkland Island specimens are identical to those of Monro (1930Monro ( , 1936). Hartman's 1967 description also agrees with Monro's and the modified description above reflects these specimens. The presence of the single paragnath in Area III of McIntosh's specimen requires further investigation as to whether this means that the species needs future re-assessment, as this would place the species in a different genus. Unfortunately, the specimen is in poor condition and a second, smaller specimen from the same location is even worse. However, a comparison of parapodia and what chaetae are available (the vast majority are broken on the McIntosh specimens) show them to be comparable. The paragnath arrangement above is therefore based on the specimens of Monro (1930Monro ( , 1936 and Hartman (1953Hartman ( , 1967) that were actually collected from the Falkland Islands. The designation of McIntosh's specimen requires further investigation although as it only deviates from the others in the presence of that single paragnath in Area III it is possible it is aberrant.
Eunereis patagonica was first recorded from the Falkland Islands by Pratt (1898) from samples that were probably from intertidal or shallow water samples, however no actual habitat, depth or locality details were given. The only other records from the Falkland Islands are those of Monro (as Nereis hardyi: 1930, 1936 and Hartman (1953Hartman ( , 1967 from offshore (106-150 m) samples, as well as an even deeper record at 1879-1886 m by Hartman (1967).
Outside of the region, the species was recorded by Hartman (1967) from 31 m (Cape Horn) to 300 m (South Shetland Islands) together with an additional record of a pelagic epitoke from the Pacific Antarctic Ridge at 3660 m considered to have been carried beyond its viable range.
The species is here believed unlikely to be found intertidally around the Falkland Islands but with potential to be found in the region's nearshore (< 30 m) waters; Pratt's 1898 record (if accurate), likely being from this region.
Habitat  Bakken and Wilson 2005). Prostomium with entire anterior margin, one pair of antennae, one pair of biarticulated palps with conical palpostyles, four pairs of tentacular cirri with distinct cirrophores. Eyes present or absent. One apodous anterior segment, greater than length of chaetiger 1. Maxillary ring of pharynx, conical paragnaths: Areas I−IV, present or absent; IV, smooth bar-like paragnaths present or absent. Oral ring, conical paragnaths: Areas V and VI present as distinct groups or not separated; V−VIII, present or absent. Dorsal notopodial ligule present, similar in size on anterior and posterior chaetigers or markedly reduced on posterior chaetigers. Prechaetal notopodial lobe present or absent, smaller than dorsal notopodial ligule on anterior chaetigers, usually reduced or absent posteriorly, present throughout all chaetigers or restricted to a limited number of anterior chaetigers. Acicular process present or absent; present on anterior chaetigers, reducing in size posteriorly. Dorsal cirrus basally or middorsally to subterminally attached to dorsal notopodial ligule on posterior chaetigers, lacking basal cirrophore. Neuropodial postchaetal lobe absent or present. Notoaciculae absent from chaetigers 1 and 2. Notochaetae: homogomph spinigers. Neurochaetae, superior fascicle: heterogomph spinigers present or absent, homogomph spinigers present, heterogomph falcigers on anterior chaetigers present, on posterior chaetigers present or absent. Neurochaetae, inferior fascicle: heterogomph spinigers present or absent, homogomph spinigers present or absent, heterogomph falcigers present. Colour pale cream in alcohol, some with dark brown, uniform shading remaining over anterior chaetigers.
Remarks. In a detailed study of Australian and sub-Antarctic specimens of N. kerguelensis, Wilson (1984) described a wide variation in the numbers of paragnaths in Areas II, III and IV. This, combined with the apparent widespread occurrence across both hemispheres and from intertidal to 5000 m depths, would suggest that records of this species may, in fact, represent a species complex. Greater investigation in each area is required to properly resolve this.
The variation in paragnath numbers exhibited by the Falkland Islands specimens is within the boundaries of that described by Wilson (1984), although it falls consistently at the lower end of those ranges. In addition, the majority of specimens had tentacular cirri that extended only to chaetigers 2-4 (Wilson 1984: 4-8 chaetigers) although some did extend up to chaetiger 7, and the neuropodial postchaetal lobe was present throughout the body as opposed to only the anterior 20-30 chaetigers (Wilson 1984).
There are currently no published genetic sequences for N. kerguelensis. However, a comparison of some of these different populations using molecular techniques may help resolve these discrepancies. Habitat. Wilson (1984) describes the habitat as "associated with fouling communities, intertidal in rocks and sand on sheltered and exposed coasts, soft bottom benthos to 115 m deep". Previous records from the Falkland Islands exist from intertidal to 197 m depth and from this survey from intertidal to 20 m depth in almost every habitat sampled (including algal holdfasts, epifaunal turf, coarse sand, gravel and under rocks), except for mud and fine-medium clean sands.
Distribution. Recorded widely across the southern hemisphere including Australia, New Zealand, Tasmania, Fiji, Taiwan, Antarctic Peninsula, sub-Antarctic Islands (incl. Kerguelen, Macquarie, South Shetlands, South Orkneys), Chile and the Falkland Islands. Previous records from the Falkland Islands exist from Pratt (1898), Fauvel (1916), Ramsay (1914), Monro (1930) and Hartman (1953) and the species was recorded from almost every location sampled during this survey.
Neanthes kerguelensis is also recorded from the Northern hemisphere from the Mediterranean and Azores (von Marenzeller 1902) and the UK (Comely 1973). The latter record, however, is discounted as the author describes his specimen as having 6-7 paragnaths in Area VI which would not identify it as this species.
Remarks. The above description is an amalgamation of the information provided by Ehlers (1897), Monro (1930) and Hartman (1964Hartman ( , 1967, although of these, only Monro published on specimens from the Falkland Islands. The type locality for the species is the Strait of Magellan, but Kinberg (1865) gave little detail about the animal itself. The species was later comprehensively re-described and drawn by Ehlers (1897). Descriptions by different authors are quite variable, particularly regarding the paragnaths arrangements. Ramsay (1914) gave no details about his specimens except to say that they "agreed in all respects" with Ehlers' description whereas Monro (1930) noted that, in contrast to Ehlers' description, the paragnaths of Areas VII-VIII "form a single very sparse irregular row and in a number of the larger examples they appear to be altogether absent" Nereis eugeniae was not collected by this survey, however it has been recorded from several offshore locations around the islands from 1-115 m (Ramsay 1914;Monro 1930) and Monro (1930) described the species as being "common off the Falkland Islands". There are no intertidal records for the area, however N. eugeniae has been recorded intertidally from Chile (Ehlers 1901;Hartman 1967). Although not recorded here, the species is known to be present in shallow water around the islands and could potentially be found intertidally also.
Dorsal ligule expanded posteriorly to a greater extent than figured by McIntosh but not as much as P. 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 P. floridana (Ehlers, 1868) and would most likely have also placed N. atlantica into Perinereis if P. 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 N. 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 P. falklandica as N. atlantica. Unfortunately, without the specimens no confirmation of this is possible. Certainly, aside from Pratt's record, no other specimens like P. 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 1A' of Hutchings et al. (1991) along with P. floridana: Perinereis species with 1 bar in Area VI and dorsal notopodial lobe not greatly expanded.

Material examined.
Body dorso-ventrally depressed, uniform width for most of length, tapering slightly over last few chaetigers. Head with prostomium longer than broad (Fig. 7A), antennae short, stout, 2/3 length of broad palps. Four pairs short, tentacular cirri, pale with dark cirrophores, reaching to chaetiger 2-4. Two pairs small, black eyes, equal size, anterior pair more laterally placed (Fig. 7A). Eyes difficult to discern once preserved due to dark prostomial colour, particularly anterior pair.
Habitat. In this study, all specimens were from intertidal, mid-low shore locations, in hard substrates such as coarse sand/gravel, under rocks, in crevices and under pink encrusting algae.
Of the handful of other records in the literature, the species is mostly found intertidally in hard, often exposed habitats. Ramsay (1914) collected his specimens from 15 fathoms (27.4 m), the deepest record of this species.
Distribution. Falkland Islands, Magellan region (Orange Bay), Tristan da Cunha, Chile Remarks. Perinereis falklandica has not been reported very widely in the literature since Ramsay described it from the Falkland Islands in 1914, although it was found to be quite common in coarse, intertidal habitats during this survey. Only one other record exists for the locality, being that of Hartman (1953), from a single intertidal sample at Port Louis. This is undoubtedly due to the fact that, other than Ramsay's original record, the species has rarely been identified from sublittoral samples and little intertidal work has been undertaken in the Falkland Islands. Outside of the Falkland Islands, with the exception of a single record from Tristan da Cunha (Day, 1954), it is mostly known from the coast of Chile (Fauvel 1941 (Magellan Strait);Wesenberg-Lund 1962;Hartmann-Schröder 1962, 1965Rozbaczylo and Castilla 1973;Rozbaczylo and Bolados 1980;Sampertegui et al. 2013).
The validity of the species has not been questioned and it is easily distinguishable from other species. Type material was therefore not examined.
Descriptions of the specimens from the different localities are mostly uniform with the only variation being in the number of paragnaths found in Area V of the proboscis. Most authors have reported a single, large cone in this region with the exception of Day (1954; 1-3 cones), Rozbaczylo and Castilla (1973;1-5 cones) and Sampertegui et al. (2013;1-3 cones). All of the specimens in the current study exhibited only a single cone with the exception of one aberrant specimen with 1 large and 27 small cones. The latter specimen agrees with the usual description of P. falklandica in all other respects and is considered aberrant. The number of paragnaths in Areas I-IV and VII-VIII are highly variable and the range exhibited by the specimens in the current study fall within the larger range reported by Sampertegui et al. (2013). Hutchings et al. (1991) placed P. falklandica into their 'Group 1B': Perinereis species with 1 bar in Area VI and dorsal notopodial lobe greatly expanded on posterior chaetigers.
Remarks. The above description is emended with respect to the paragnath terminology introduced by Bakken et al. (2009). However, it should be noted that Bakken et al. (2009) only confirmed the form of paragnaths as tight rows of rods, as opposed to the previously described pectinate bars, for 3 species of Platynereis that did not include P. magalhaensis. This is now, however, confirmed for P. magalhaensis below.
Proboscis with tight lines of rod-like paragnaths in Areas III, IV, VI, VII and VIII, absent in Areas I, II and V. Largest group in area IV with up to 9 long rows, innermost 3-4 rows incomplete. Area III with 3 small groups of up to 4 lines in each. Area VI, the smallest group, often faint, difficult to discern, with up to 3 short lines of rods (Fig.  9G, indicated by arrow). Area VII-VIII with 5 groups of up to 3 curved lines in each (Fig. 9I). Jaws dark brown with up to 12 teeth (Fig. 8G, I).
Pygidium terminal; two long, thin anal cirri inserted ventrally. Tube soft, with coarse grains of sand, shell and foraminifera adhered to it. Remarks. Platynereis magalhaensis was the most common nereidid collected by diving with most rocks turned over having tubes attached to the underside. It was also widespread intertidally, again in tubes attached to rocks or algal holdfasts.
The original description of P. magalhaensis by Kinberg (1865) was brief with little detail except a general description of the head, and a statement that the tentacular cirri reached to the 15 th segment and there were 12 teeth on the jaws. Several authors since then have expanded the description using either newly collected specimens (e.g. Ehlers 1897;Fauvel 1916) or by re-examining Kinberg's type material (Hartman 1948). The species can be distinguished from most other Platynereis species on a combination of the absence of paragnaths in Areas I, II and V and the absence of notopodial falcigers (in adults). However, P. magalhaensis remains difficult, if not impossible, to separate morphologically from the P. australis 'group' -P. australis (Schmarda, 1861), P. karaka Read, 2007, P. kau Read, 2007, P. mahanga Read, 2007resulting in a conflict of opinion with some authors synonymizing it with P. australis while others prefer to keep them separate.
Most recently, a detailed comparison of the P. australis group with P. magalhaensis was published by Read (2007), following which he concluded that while morphologically inseparable as atokes, as epitokes the species could be differentiated on the basis of characters such as number of pre-natatory segments and male pygidial form and thus P. magalhaensis should still be considered a valid species.
Unfortunately, no epitokous forms were among the specimens collected from the Falkland Islands so this aspect cannot be confirmed in this study. However, the few records of epitokes that do exist for this region (Ehlers 1897;Augener 1923;Monro 1930) indicate that the species is likely to be distinct from P. australis and Read (2007) additionally stated that records of P. australis outside of New Zealand should be reassessed. The species collected from the Falkland Islands is therefore viewed as being appropriately placed under the name P. magalhaensis. However, further study of the epitokous form from the islands is necessary to help clarify the situation.