A limnological reconnaissance of the Falkland Islands; with particular reference to the waterfleas (Arthropoda: Anomopoda)

Forty‐eight freshwater bodies on the Falkland Islands, including 33 lakes and pools, and 12 rivers and streams, were sampled for freshwater invertebrates. This study yielded 129 species of invertebrates (79 Rotifera, 34 Arthropoda, six Platyhelminthes, three Gastrotricha, two Nematoda, two Annelida, two Mollusca, and one Tardigrada) plus two fish species bringing the known Falkland Islands freshwater fauna to more than 170 species. While the presence of fishes, molluscs, amphipods, caddis larvae, waterboatmen, parasitic cercaria, and truly planktonic rotifers make the Falkland Islands fauna markedly richer than any subantarctic, or maritime Antarctic island, it is nevertheless sparse when compared with other temperate and tropical locations.


Introduction
This paper describes a limnological survey of the South Atlantic Falkland Islands between 30 January and 10 March 1993. This represents the first ''comprehensive'' survey of the Falklands simply because many potential workers have been seduced away to the nearby and ''more attractive'' Antarctic and have made only perfunctory collections on their way through. Furthermore, some published reports are far from encouraging. The Falkland Island field guide (Strange 1992) makes no mention of freshwater invertebrates. The freshwater vegetation section states ''although ponds are common to most areas, many appear sterile, supporting little or no animal life and devoid of any form of vegetation''; and although mention is made that ''ponds associated with coastal greens and those fed by streams are more fertile, often supporting aquatic vegetation'', the fauna is not mentioned. These statements are at odds with the islands' aquatic avifauna which includes an impressive list of ducks and waders, and at least two, possibly four, native fishes as well as an introduced species of trout that has successfully colonized many areas. Sea Lion Island is the most isolated of the Falklands where samples were taken from the four shallow (,3 m deep) extant ponds ( Figure 5). They are acidic (pH 4.9-6.8) and enriched by a variety of water birds.
Twelve water bodies on the eastern half of Pebble Island were sampled ( Figure 6). These included one very small (only 8 cm deep and barely 30 cm 2 ) rock pool on a cliff face close by a cormorant colony at Cape Tamar. All the other sampling locations are close to the sea,  indeed most of the lakes have outflow pools and streams that drain through the coastal sand dunes.
Six streams and eight lakes were sampled in and around Fox Bay on West Falkland (Figure 7). Here the principal objective was Lake Sulivan, the largest expanse of freshwater in the Falkland Islands comprising two substantial basins-North and South Lake Sulivan, separated by a low ridge. Although South Lake Sulivan is .6 km long, at the time of sampling it was barely 2 m deep. The lakes and streams at Fox Bay were sampled with plankton and hand nets.

Materials and methods
Three different habitat-specific sampling methods were employed. In large lakes plankton nets (53 mm mesh) were thrown into deep water and allowed to sink before being slowly retrieved. In streams and vegetated areas hand nets (53 mm mesh) were swept through the  water and dense vegetation. In very shallow water or highly vegetated sites, plunge pots (125 ml plastic bottles) were used either as scoops or hand-filled with aquatic plants.
Water pH was measured in the laboratory where samples were then concentrated by filtration (20 mm mesh) and examined using dissection and compound microscopes. Drawings were made from (1) live, free-swimming specimens held under slight compression of a coverslip mounted on petroleum jelly, (2) specimens permanently mounted in polyvinyl-lactophenol, and (3) preserved specimens. Selected specimens were preserved in a formaldehyde-based preservative for subsequent specialist examination.

Platyhelminthes
At least four species of freshwater flatworms (Turbellaria) were observed: (1) a common, eyed vermiform species with a short thin tail; (2) another eyed species without a tail, (possibly two species as those at Fox Bay were particularly large); (3) a small eyeless species (similar to Species No. 3 at South Georgia;Dartnall 2005a); and (4) a larger eyeless species, with a slightly bulbous head. In addition, two types of trematode cercariae were observed-one with a forked tail and one with a single tail. The life cycle of these parasitic flukes involves freshwater snails, fishes, and aquatic birds.

Gastrotricha
Three taxa were recognized: a scaly Leptoderma species; and two Chaetonotus species, including one ''short-haired'' and one ''long-haired''. Although Gastrotrichs are uncommon, represented by only solitary specimens, they are probably ubiquitous.

Tardigrada
Tardigrades were surprisingly uncommon and only one species, a Dactylobiotus sp., was collected (S. McInnes, personal communication). Tardigrades usually occur in benthic sediments or on aquatic vegetation and the failure to secure large numbers of specimens or species may in part be explained by sampling techniques, though plankton nets similarly deployed at South Georgia (Dartnall 2005a) yielded six species from four genera.

Nematoda
Two morphotypes distinguished by size were recognized in the field: a small species with a whip-like action, a ?Monhystera sp., and much larger specimens, probably several genera. Those from Pebble Island have been identified as a Eutobrilus sp. (R. Maslen, personal communication).

Rotifera
Seventy-nine species of rotifer (73 Monogononta and six Bdelloidea) were recognized, all of which are new records for the Falkland Islands. Twenty-three (nearly a third) were represented by single specimens and a further 13 were only found at one of the six sampling regions. Only one species, Notholca squamula, was present at every collecting centre. Keratella heywoodi, a large planktonic rotifer that was also found on South Georgia, is new to science (Dartnall 2005b).

Annelida
A few oligochaete specimens, subsequently identified as Nais variabilis and N. communis (Erséus and Grimm 2002), were found at every sampling location except Sea Lion Island. Although both are common and cosmopolitan neither has been reported from the Falkland Islands before. Their precise Falkland distributions are unknown though Nais variabilis was the more common.

Mollusca
Two aquatic pulmonates were collected, Chilina falklandica and Lymnaea diaphana. Both are intermediate hosts for avian trematodes.

Arthropoda
Thirty-four species of arthropod were collected during this survey including 24 crustaceans, eight insects and two mites.
Crustacea Anomopoda. Thirteen species, including four new records for the Falkland Islands, were found of which only seven were positively identified in the field with the remaining six, all small cladoceran species, being consigned to two taxa. Thus in the tables the term ''Alona sp.'' may refer to any combination of Alona affinis, A. guttata, and A. weinecki, while ''Chydorinae gen. sp.'' may refer to any combination of Chydorus sphaericus, Paralona pigra, and Pleuroxus scopuliferus. Wherever these species are named in full they are confirmed as being present at that particular location.
Alona affinis (Leydig, 1860) Several characteristics agree with the known morphology of the species: namely size 0.8 mm, valve height maximal in the middle; ocellus smaller than eye, labium with convex anterior margin; post-abdomen ( Figure 8) broad, distally rounded, with 14-15 anal denticles, basal spine of post-abdominal claw with setae on concave margin. The position of the two main head pores clearly distinguishes A. affinis from the similar A. quadrangularis. This cosmopolitan species has recently been reported from the Falkland Islands (Brooks et al. 2005).
Alona guttata Sars, 1862Vávra (1900 found this species near Stanley but gave no description of his specimens, only stating ''Die mir vorliegenden Exemplare stimmen mit der genannten Art ü berein''. Smith and Sayers (1971) and Brooks et al. (2005) have also recorded this species from the Falkland Islands. Smirnov (1974) lists six subspecies, two of which are known from South America, namely A. guttata tuberculata whose valves and head are covered with pits, and A. guttata guttata, which is supposedly cosmopolitan. Our specimens were of average size, 0.45 mm (slightly larger than European specimens); valves with longitudinal lines; length:height51.5; antennules do not reach tip of rostrum; ocellus in the middle between tip of rostrum and eye, smaller than the latter; dorsal margin of post-abdomen variable, more curved than European specimens from Lake Dü mmer, Germany (Hollwedel and Poltz 1985), 9-12 denticles with distally increasing length. Several of our specimens were noticeably different. They possessed a distally rounded post-abdomen and additionally bore two to three smaller denticles (Figure 9). These are referred to as Alona cf. guttata.

Alona weinecki Studer, 1878
Originally described from Kerguelen (Studer 1878), Rü he (1914 showed that Ekman's (1905) Falkland Island record of Alona bukobensis v. subantarctica was in fact A. weinecki. Similarly, the records of A. rectangula from South Georgia and the South Orkney Islands  refer to A. weinecki (Paggi 1987;Frey 1988). It was then supposed that this species was restricted to the subantarctic islands, but Dumont and Martens (1996) have subsequently recorded it from Easter Island, and South Island, New Zealand. The morphology of the specimens examined in this study, especially the shape and armature of the post-abdomen ( Figure 10) and size, 0.5 mm, corroborate that they do belong to this species.
Bosmina (Neobosmina) chilensis (Daday, 1902) Vávra (1900) reported this species (as Bosmina obtusirostris) from a locality near Stanley. Deevey and Deevey (1971) and Korínek (1971) considered B. chilensis and B. hagmanni to be synonyms, but Paggi (1979) concluded that they are different species and documented separate distributions, and the occurrence of B. chilensis on the Falkland Islands. It is quite distinct from the other small anomopodans found there ( Figure 11). The females averaged 0.6 mm. The position of the lateral head pore ( Figure 12) and the serrations on the dorsal side of the mucro are morphological characteristics of the subgenus Neobosmina (Lieder 1983;U. Leider, personal communication).  Ekman, 1900 Originally reported from Patagonia (Ekman 1900), this species has also been recorded from South Georgia (Pesta 1928;Dartnall 2005a) so its presence on the Falkland Islands is not surprising. Our female specimens (0.6 mm) conform with Ekman's description exhibiting the main characteristics that separate C. aloniceps from the other congeners: head keel and denticles on the postero-ventral corner of the valve absent, dots between longitudinal lines of the valves, concave side of post-abdominal claw with a basal spine and a row of small spines with a long one nearly in the middle of the claw ( Figure 13).

Ceriodaphnia dubia Richard, 1894
Although Ceriodaphnia dubia is regarded as a cosmopolitan (Alonso 1996) or polytypic species (Flö ssner 2000), it has not been previously reported from the Falkland Islands nor indeed from any of the subantarctic islands. The species is closely related to C. quadrangula, with which it has often been confused (Flö ssner 1972).
Female: size of adults 0.7-0.85 mm, valves broad oval, head separated by deep notch, post-abdomen before anal teeth slightly concave. The distinctive feature is a row of small spines, one-third of which are longer, on the concave margin of the post-abdominal claw, visible under high magnification on most of our specimens. The specimens from Pebble Island represent a polymorph population, have a proximal pecten comprising 13-14 denticles twice the length of the spines and becoming shorter distally ( Figure 14). The variability of this characteristic has been confirmed (D. Berner, personal communication).
Male: size 0.55 mm, valves dorsally not oval, posterior-dorsal angle pointed, antennulae rather long, post-abdomen similar to female, claw with setules, but no pecten.
Chydorus sphaericus (O. F. Mü ller, 1785) This species is supposedly cosmopolitan (Smirnov 1996) but is most probably a species group. It has been recorded from the Falkland Islands (Vávra 1900;Ekman 1905) and from  several of the subantarctic islands (Frey 1993). Dartnall and Heywood (1980) recorded C. sphaericoides Sars, 1909 from the Falklands, a species name that Frey (1993) ascribed to C. sphaericus, whereas Smirnov (1996) believes it to be a synonym of C. patagonicus Ekman, 1900, a species recently reported from Macquarie Island (Dartnall et al. 2005). Our specimens are most probably C. sphaericus as suggested by the variable labral plate which in some specimens has an elongated and rounded tip, while in those from the Brown Pond are bent posteriorly. The post-abdomen is short and broad with 9-11 denticles, though two specimens from Moody Brook has 13 denticles. Ekman (1905) noted several similarities between the females of C. sphaericus and C. patagonicus. We did not find any males in the samples that would enable us to verify the diagnosis. Both C. sphaericoides and C. sphaericus have been reported from the Falkland Islands by Smith and Sayers (1971). Paggi, 1999 Daphnia dadayana is restricted to non-tropical South America where it is regarded as endemic (Villalobos 1994), and has not been previously recorded from the Falkland Islands.

Daphnia (Ctenodaphnia) dadayana
Adult female: 2.5-3.25 mm; valves oval with a depression between head and dorsal margin. The latter and posterior half of ventral margin with small denticles, the central third of inner ventral margin with a row of longer setae directed inward and posteriorly. Shell spine short or completely reduced. Head high, anterior rounded, ventral margin straight or slightly concave; rostrum pointed, antennulae do not reach the tip of rostrum; ocellus extremely small. First abdominal process double the length of the second, the former curved anteriorly and covered with setules, the latter curved posteriorly and thinly covered with setules, the third and fourth processes are small protruberances. Postabdomen ( Figure 15) long and broad, narrowing distally, dorsal margin slightly concave with 16-19 post-anal denticles, post-abdominal claw stout with two pectens, a proximal one with seven to nine smaller denticles, and a distal one with 9-12 longer denticles ( Figure 16).
Juvenile female: ventral margin of valves broadly rounded, the whole length covered with denticles, dorsal margin straight, and denticulate, passing over a dorsally directed shell spine, nearly as long as body. Ventral margin of head equally convex, no rostrum, eye near  Figure 9) and Paggi's drawing (1999, p. 32, Figure 45). Villalobos (1994) mentions that some of her juvenile specimens from South America have ''a little helmet''. A similar horn seems to occur in other species. Rane (1986) describes and illustrates juveniles of Daphnia sarojae Rane with a helmet that is similar to the Falkland D. dadayana, but note that Sharma and Sharma (1990) believe Daphnia sarojae to be a helmeted morphotype of D. lumholtzi.

Daphnia pulex Leydig, 1860
Although Ekman (1905) emphasized the similarities between the specimens he found on the Falkland Islands with Daphnia obtusa from Tierra del Fuego by Vávra (1900), our specimens are definitely D. pulex, not D. obtusa.  Female: 1.42-1.65 mm, valves broad and oval, dorsal and ventral margin with denticles, inner ventral margin without setae, shell spine short or absent, all juveniles with spines; ventral margin of head concave; antennulae do not reach tip of rostrum. Post-abdominal claw with a pecten of eight to nine denticles.
Juvenile male: 0.62-0.95 mm; anterior ventral margin with long spines; rostrum short; antennulae nearly as long as flagellum, not on a curved projection. Second abdominal projection relatively short, not reaching the root of abdominal setae; dorsal margin of postabdomen straight as in D. obtusa. Daphnia pulex was reported from the Falkland Islands by both Smith and Sayers (1971) and Brooks et al. (2005). According to Benzie (2005) the occurrence of D. pulex in South America is doubtful, suggesting our specimens may belong to a different species. This needs clarification. Ekman, 1905 Originally described from the Falkland Islands and South Georgia (Ekman 1905), this species has subsequently been recorded many times from South Georgia (Sars 1909;Dartnall and Heywood 1980;Hansson et al. 1996;Dartnall 2005a) as well as from the South Orkney Islands (Heywood 1967(Heywood , 1970Heywood et al. 1979;McInnes and Ellis-Evans 1990). Kotov et al. (2002) published a redescription of the species, recording it from the southern-most portion of Argentina and Chile. The specific name refers to the short denticles of the secondary armament of the post-anal section of the post-abdomen. In our specimens these denticles are slightly longer than those of both Ekman's and Sars' illustrations, with their tip reaching beyond the post-abdominal margin (Figure 18), as shown by Kotov et al. (2002, Figures 41-43). They are of different lengths, proximally four small ones curved proximally, followed by two groups of 5 + 3 long ones; between these and the post-abdominal claw is a row of setae. The preanal section of the post-abdomen bears 19 denticles; the first three proximal ones are somewhat longer, the next 11 are of medium size followed by five long ones, the last three of which are the shortest, post-anal portion with two short and seven long denticles. Adult females are 0.65 mm long. Although Verkhov (1993) states I. brevidentatus is an inhabitant of the southern circum-polar district, Green (1981) lists it from tropical South America.

Macrothrix hirsuticornis Norman and Brady, 1867
Recorded from the Falkland Islands as M. ciliata by Vávra (1900), and M. propinqua by Ekman (1905) and Sars (1909). We regularly encountered juvenile and fertile females. Our specimens averaged 0.62 mm, a similar size to that reported by Vávra but only half that of specimens from German islands in the southern North Sea (Hollwedel and Scharf 1988). Ekman's (1905) specimen range was 0.85-0.92 mm. Sars (1909) points out that his M. propinqua (1.14 mm) from South Georgia has less curved antennulae which are ''less densely hirsute'', with a smaller ocellus nearer to the tip of the rostral projection. Both characteristics are found in our specimens ( Figure 19). Smirnov (1992) states that no other distinctive differences are known and claims that those ''features correspond with the present-day understanding of M. hirsuticornis''. The late David Frey considered all Antarctic identifications of Macrothrix hirsuticornis to be dubious as this is a boreal northern hemisphere species. A. A. Kotov (personal communication) thinks that the Falkland Island  Macrothrix is Vávra's M. ciliata, but it must be checked against Ekman's Patagonian species M. oviformis to see which has priority as both species were described in 1900.
Paralona pigra (Sars, 1861) This cosmopolitan species has been reported from the Falkland Islands (Brooks et al. 2005). It is identified by the long setae on the postero-ventral angle of the valves and the long denticles at the distal end of the post-abdomen (Figures 20, 21). Ekman, 1900 This species, described from South America (Ekman 1900), was only found on Pebble Island. Kotov and Gololobova (2005) found Ekman's (1900)   (1993) study on Pleuroxus from the subantarctic islands we could easily identify our juvenile and parthenogenetic female specimens.

Pleuroxus scopuliferus
Female: 0.6 mm, brown colour, valve with ridge, one denticle at the postero-ventral angle, rostrum longer than labrum, tip of rostrum rounded, anal and post-anal segments of post-abdomen equally long ( Figure 22), but both longer than pre-anal region, postabdominal claw stout with two basal spines, the longer one nearly as long as width of claw, shorter one half as long.
Copepoda: we found three calanoid, and three cyclopoid copepods. The calanoids include Parabroteas sarsi and two Boeckella spp., B. michaelseni and B. poppei, which were familiar from earlier studies on South Georgia (Dartnall 2005a) and the South Orkney Islands (Heywood et al. 1979. Parabroteas sarsi is a powerful swimmer that can avoid plankton nets and is probably more widespread on the Falkland Islands than suggested here. The specimens of Boeckella poppei, though ''exceptionally variable so that one might suspect at least two species'' are in fact conspecifics (Hessen et al. 1989;G. Boxshall, personal communication).
Two cyclopoid copepods were identified in the field. One of these, a stream-dwelling species from Fox Bay, thought to be Tropocyclops meriodionalis, is sometimes treated as a subspecies of T. prasinus (G. Boxshall, personal communication). The other cyclopoid was subsequently determined to be two species including a larger Acanthocyclops michaelseni and a smaller Diacyclops sp. possibly D. (Acanthocyclops) mirnyi (G. Boxshall, personal communication, who considers the original descriptions of both taxa inadequate and in need of revision).
Harpacticoida: a few small specimens were observed. These have been assigned to two (unidentified) Canthocamptidae one of which was also present at South Georgia (G. Boxshall, personal communication). Attheyella trigonura (Ekman) has been reported from the Falkland Islands (Ekman 1905;.
Ostracoda: only one species, Newnhamia patagonica, a new record for the Falkland Islands, was observed.
Amphipoda: freshwater amphipods were regularly encountered and were present at every location except Mount Pleasant. According to Stock and Platvoet (1991) four species are known from the Falkland Islands. Both Falklandella obtusa Schellenberg and Praefalklandella cuspidata (Schellenberg) are eyeless, colourless species and may be emergent-subterranean species though the former has been found in Moody Brook (Stock and Platvoet 1991). There are also two eyed species, Hyalella curvispina Shoemaker and Hyalella neomoma Stock and Platvoet. All specimens found in this survey were brown and eyed and thus ascribed to the genus Hyalella.
Hexapoda. Diptera: unidentified specimens of a larval midge (Chironomidae) were regularly encountered from all locations except Sea Lion Island. A second species was recognized in the field from three Fox Bay locations. Weller (1975) recorded four families in his survey of Falkland Island ponds, while Brooks et al. (2005) consider there to be at least 15 species present from 12 taxa, though none were identified to species. These include carnivorous genera Ablabesyia, Macropelopia, and Apsectrotanypus; Parochlus, Podonomus, Podonomopsis, and Rheotanytarsus from cool water, the blood worms Chironomus, Phaenopsectra, and Parapsectrocladius, along with two Tanytarsini spp. and three Cricotopus.
Trichoptera: two types of caddis fly larvae were recognized in the field: (1) those that make their protective tubes from reeds and other detritus pieces, and (2) a smaller larva with a transparent flattened cone-shaped tube, open at both ends. The reed-cased specimens comprise two Magellomyia spp., including M. appendiculata (Ulmer), with a uniformly coloured head and a slightly curved tube, and Magellomyia stenoptera Schmid, which has a banded head and straight tube. This distinction was not known at the time of the collection when specimens were pooled. The transparent-cased caddis is an Oxyethira spp. Coleoptera: two species of diving beetle were found, Lancetes falklandicus and a much smaller bidessine (G. Foster, personal communication). Both are powerful swimmers able to avoid slowly trawled plankton nets but were collected in hand nets and are probably more widespread than indicated.
Hemiptera: unidentified specimens of waterboatman were observed at both Pebble Island and Fox Bay. These powerful swimmers can avoid nets and are probably more widespread than indicated. These records represent the first report of waterboatmen from the Falkland Islands.
Chelicerata. Acarina: only two specimens were found, in the Felton Stream near Stanley and in a stream by the Hawk's Nest Shanty pond. They have been identified as Soldanellonyx monardi Walter and Mucronothrus nasalis (Willmann), both of which are ''cosmopolitan'' freshwater species (P. J. A. Pugh, personal communication).

Vertebrata
Two species of fish were found in this survey, the Falkland Island minnow Galaxias maculates (Jenyns) and the Falkland Island trout Aplochiton zebra Jenyns. Both are diadromous though landlocked populations are known (McDowall et al. 2001). Neither was particularly common and solitary individuals were usually obtained in hand net sweeps but were noticeably absent from the very small water bodies around Stanley and from Sea Lion Island.

Limnological reconnaissance of the Falkland Islands
Nais variabilis Pinguet and/or N. communis Piguet -

Locations
The occurrences of the various aquatic taxa found on the Falkland Islands are summarized in Tables I-VI. No real significance is attached to the observation that the streams and ponds around Stanley (Table I) contained a greater variety of rotifer species, as these sites were sampled most frequently and more intensely. The Moody Brook with its series of dammed pools was particularly productive in this context, being slightly acidic whilst lacking both predatory fish and arthropod competitors. This was confirmed at Duck Pond which was teeming with anomopodans virtually to the exclusion of the other groups. Small and temporary puddles, including the very alkaline roadside drainage ditch on Stanley Common, appear to be very poor habitats. The fauna of the Mount Pleasant ponds and small river were all very similar (Table II), comprising ubiquitous species. Bodie Creek (Table III) was notable for the presence of two pulmonates and accompanying free-swimming cercaria. Chilina falklandica, which generally inhabits streams, is known to be a host for a forked-tailed cercaria so it is tempting to assign the straight-tailed cercaria to the other Falkland snail, Lymnaea diaphana. Both schistosome cercaria are likely avian parasites.
The small ponds on Sea Lion Island were shallow and appear ephemeral, which may explain their limited diversity (Table IV). Long Pond was the most productive with large numbers of anomopodans. Fishes, oligochaetes, gastropods, amphipods, corixidae, and dipteran larvae were notably absent and this may reflect the relative isolation of this island. Most major taxa (caddis flies excepted) are present in the larger and deeper ponds on Pebble Island (Table V) which supported large numbers of planktonic rotifers. The Cape Tamar rock-pool fauna was very limited, comprising a marine harpacticoid and two rotifer species including Colurella colurus compressa which is usually associated with brackish water.
Fox Bay harboured all major Falkland freshwater taxa but in low numbers (Table VI). Planktonic rotifers and crustaceans were scarce with both Daphnia dadayana and D. pulex notably absent. Clearly the West Falkland water bodies are less productive than their East Falkland counterparts.

Additional records
While 129 species of aquatic invertebrates and two species of fish were recorded in this survey, a number of additional species are known from the islands, including one hirudinean, six Mollusca, nine Crustacea, 16 insects (including the 15 diptera already mentioned), and possibly three species of fish. This is in addition to the two species of eyeless amphipods (Weller 1975;Stock and Platvoet 1991;Brooks et al. 2005).
The 2001 Falkland Islands-Biodiversity Research in Lakes project (FI-BRIL) (Brooks et al. 2005) examined 28 lakes and streams on the two main islands. It focused on cladocerans (anomopodans), chironomids, and copepods and is complementary to our Leptoderma ''scaly'' sp. -

Platyhelminthes
No. 1-common eyed sp. with a short thin tail
Likewise, we did not observe a number of FI-BRIL taxa including Bosmina longirostris, previously reported from the Falklands (Smith and Sayers 1971), Bosmina kessleri (Uljanin), Ceriodaphnia rotunda Sars, Daphnia longispina O. F. Mü ller, Eubosmina longispina Leydig, Leptodora kindti (Focke), and Kurzia latissima (O. F. Mü ller). These were a considerable surprise to us and while ''several taxa were not identified confidently'', thereby leaving some room for taxonomic realignment, it is difficult to see how, for example, the large distinctive predator Leptodora kindti, can be questioned. Brooks et al. (2005) suggested that some of their anomopodans had very limited distributions and indeed only four water bodies, Swan Inlet Pond, Bodie Creek, Lake Sulivan, and Hawk's Nest Pond, were sampled by both surveys. This is clearly an area for further investigation. We suspect that many of these extra species have inadvertently been introduced with the brown trout and have subsequently become established on the island.
The review by  lists two species of anomopodans, Ceriodaphnia silvestrii Daday and Macrothrix laticornis (Fischer), and three copepods Acanthocyclops lobulosus (Ekman), A. skottsbergi Lindberg, and Boeckella vallentini (Scott) not found by either FI-BRIL or us that also require clarification. Other previously recorded species not found in this survey include two species of ostracod, Candonopsis falklandica Vávra and Chlamydotheca symmetrica Vávra (K. Martens, personal communication). Note that the FI-BRIL survey lists Candona spp. and other ostracods from non-acid environments (Simpson and Nolan 1994). McLellan (2001) described two species of stoneflies (Plecoptera) from the Falkland Islands, one Falklandoperla kelper McLellan, with an aquatic nymph, and an other which is probably terrestrial. The FI-BRIL survey also reported rare mosquito larvae and pupae, but no adults from Dan's Shanty Pond, a small peaty pool on East Falkland. They also reported mayflies from near the Hawk's Nest Pond (R. M. McDowell, personal communication) but consider they may have been imported on the sampling equipment.
Finally, three additional fish species, two native species and an introduced one, should be discussed. The pouched lamprey Geotria australis Gray has been recorded at sea to the south of the Falkland Islands (Potter et al. 1979), and although there has been one mainland sighting (Gorham 1977) it is considered to be marine. The record for the other native fish, Galaxias platei Steindachner, originally described as G. smithii (Regan 1905), is of questionable provenance (McDowell 2002). Finally the brown trout, Salmo trutta L., has been stocked in the Falkland Island lakes and rivers on a number of occasions since the 1940s and so must be included as part of the freshwater fauna even though it was not observed in this survey. This fish is now widespread, and specimens of ,10 kg are known from major estuaries, which we did not sample.   Monommata sp. - - Nais variabilis Pinguet and/or N. communis Piguet ''Chydorinae gen. sp.''

Cladoceran dispersal
Cladocera produce small resting eggs, which can be transported by wind and birds. In recent years passive dispersal may have been increased by tourism and military activities, as the ephippia can adhere to boots, clothes, and equipment and thus get into new water bodies. The Falkland Islands, which are only 600 km from South America, are inhabited by a number of common neotropica species including Alona affinis, A. guttata, Ceriodaphnia dubia, Daphnia pulex, and Paralona pigra, which do not occur on any of the south Atlantic islands. Only two neotropical species have been dispersed farther eastward, Camptocercus aloniceps to South Georgia, and Ilyocryptus brevidentatus to South Georgia and Signy Island, while three, Bosmina chilensis, Daphnia dadayana, and Pleuroxus scopuliferus, are restricted to the Falkland Islands and South America. Most of our Falkland records relate to species originally described from Europe and are supposedly cosmopolitan. Further study, including detailed comparative anatomy and molecular methods, will be necessary to verify if these are truly cosmopolitan or part of larger species groups.

The Scotia Arc
This survey is the final phase of a long-term project that set out to determine the freshwater fauna of the Scotia Arc islands that link the Antarctic Continent via the Antarctic Peninsula to South America. Earlier investigations have shown a diversity decrease with increasing latitude Dartnall 2005a), a trend noted in other non-marine invertebrates. The Falkland Islands' fauna includes fishes, molluscs, hemipterans, amphipods, planktonic rotifers, and helminths that do not occur further south. The fauna lacks many insects with aquatic larvae including dragonflies and damselflies (Odonata), stoneflies (Plecoptera) and mayflies (Ephemeroptera), as well as amphibians and a wide range of fishes that typically occur in temperate and tropical freshwaters, reinforcing this premise.
The freshwater fauna of the Antarctic region is primarily benthic and planktonic species are generally uncommon (Dartnall 2005b). The Falkland Islands' fauna includes a considerable number of planktonic rotifers including Asplanchna, Brachionus, Filinia, Keratella, Polyarthra, and Synchaeta spp. that are either absent or poorly represented further south. Parasitic species with their complicated life cycles are unknown in Antarctic and subantarctic freshwaters but two cercariae and a freshwater leech are present on the Falkland Islands. Of particular interest is the distribution of the copepod Diacyclops mirni which is absent on all of the Scotia Arc islands but present on the Antarctic continent, where it was originally described from the Bunger Hills (Borutski and Vinogradov 1957) and subsequently found in the Vestfold Hills (Korotkevich 1958;Borutski 1962;Dartnall 2000), and Larsemann Hills (Dartnall 1995).
Further surveys on the Falkland Islands will undoubtedly increase the species tally, particularly for tardigrades and nematodes, though both groups are poorly documented in Antarctic freshwaters. The Falkland fauna has greater affinities with that of South America than that of South Georgia and the islands of the Maritime Antarctic.