Review Artemia (Crustacea, Anostraca) in Chile: a review of basic and applied biology

. The brine shrimp Artemia in Chile has been studied since the 1980s, initially on populations inhabiting shallow coastal and inland mountain ponds, and saltworks in northern and central Chile. Based on morphometric and molecular evidence, these populations were identified as A. franciscana . In the 1990s, A. persimilis was recorded from southern Patagonia, a species previously considered endemic to Argentina. Recently, two new populations of A. franciscana have been recorded, from one saline coastal pond in northern Chile and from a saltwork in central Chile. The scope for further research to increase both understanding of the strain characterization and basic population ecology descriptions of the Chilean brine shrimps and improve their conservation status is discussed. It is suggested that future studies should investigate first the management of local brine shrimp population for local aquaculture or conservation resources, other direction would be the effects of ultraviolet radiation (UVR) exposition that is notoriously high in brine shrimp habitats. This last factor is very important because the UVR is an important mutagen on the genetic structure of the populations. In this scenario, it is suggest a carefully management for introduced brine shrimp populations for local aquaculture for avoid alterations in native populations that due their genetic isolation would need conservation procedures for avoid local extinctions.


STRAINS CHARACTERIZATION
The two species in South America, A. franciscana and A. persimilis, were first recognised by Amat (1980) and Hontoria & Amat (1992).Gajardo et al. (1995), in a series of studies using allozymes and/or cytogenetics, investigated the genetic structure of A. franciscana (Gajardo et al., 1992(Gajardo et al., , 1995;;Gajardo & Beardmore, 1993), and A. persimilis as well (Gajardo et al., 2000(Gajardo et al., , 2001) ) from Torres del Paine National Park in Chilean southern Patagonia.Gajardo et al., (1995) concluded that genetic differences between the strain affecting the individuals from all known Chilean populations of A. franciscana are correlated with the inter-population extent of its geographical distribution and ecological isolation.Later, Gajardo et al. (2001) showed that the chromocentre numbers of A. franciscana populations from Chile and other Central and South American localities relate directly with the latitude of the habitats (Table 2).Most recently Gajardo et al. (2004) have assessed the pattern of variation of mitochondrial DNA of Chilean brine shrimps by restriction fragment length polymorphism (RFLP) analysis.They have confirmed that the species A. franciscana occurs between latitudes 20º to 33°S and the species A. persimilis is distributed between latitudes 34º to 51°S.There is some uncertainty concerning the species identity of the Salar de Atacama and Pichilemu populations.Gajardo et al. (1995) in a study of nine populations concluded that the individuals of brine shrimp at Pichilemu (38°48'S, 72°10'W) belong to A. franciscana.However, the results from subsequent morphological (Gajardo et al., 1998), cytogenetic (Colihueque & Gajardo, 1996;Gajardo et al., 2001), where chromosome and chromocentre complements of 2n = 44 and 0 to 6 respectively have been recorded), and mitochondrial DNA (Gajardo et al., 2004) studies all yield evidences indicating that Pichilemu brine shrimps belong to A. persimilis.Gajardo et al. (2004) have suggested that the presence of A. persimilis at this locality is possibly indicative of an hybrid zone.The morphological study done by Gajardo et al. (1998), provides further evidence for the presence of both A. franciscana and A. persimilis in Chile.The size of the male frontal knob is an important distinctive character to distinguish A. franciscana from A. persimilis (De los Ríos & Zúñiga, 2000).The average diameter of the frontal knob in A. franciscana is 200 μm and in A. persimilis is 300 μm (De los Ríos & Zúñiga, 2000; Table 2).This structure is used in sexual coupling; with differences in shape allowing the reproductive isolation (Mura, 1989;Mura et al., 1989).
Artemia (Crustacea, Anostraca) in Chile 71°25'W) (Amat et al., 1994b;Gajardo et al., 1998;Zúñiga et al., 1999).The habitats in each of these areas are similar in being located in ephemeral habitats at the upper high tidal level of rock beaches and with chemical characteristics similar to seawater (Amat et al., 1994b;Gajardo et al., 1998;Zúñiga et al., 1999, Table 3).The hydrological conditions of the shallow coastal ponds are an important factor regulating reproductive cycles of the brine shrimp.The brine shrimp reproduce oviparously, producing cysts in natural conditions of a strong salinity increase (Amat et al., 1994b;Gajardo et al., 1998;Zúñiga et al., 1999).No ecological studies of brine shrimp have been undertaken in this habitat, but it is probable thatthe shrimps graze on bacteria and microalgae and simultaneously they would be prazed by occasional sea birds.
A population of A. franciscana described by Crespo & De los Rios ( 2004) from a previously permanent pond near Antofagasta is a noteworthy example of how changeable shallow ponds habitats may be.This habitat initially was described as hypersaline, and the halophilic microalgae Dunnaliella salina Teodoresco and Halobacterium were recorded from the site (Gomez-Silva et al., 1990).However, following a strong earthquake that affected the area in 1995, the pond was flooded with fresh water.A. franciscana was subsequently recorded from the pond in the years 2000 and 2003 (Crespo & De los Rios, 2004) probably as a resulted from artificial inoculation.A. franciscana probably has been introduced by human intervention into artificial saltworks (Gajardo et al., 1995;De los Ríos & Zúñiga, 2000).Although neither saltwork population has been the subject of detailed ecological studies, according to Zúñiga et al. (1994).Both salt works have been operating during the last ninety years (De los Ríos & Zúñiga, 2000) and detailed studies into the dynamics of their resident brine shrimp populations, population succession and community structures are warranted.
The brine shrimp populations of inland saline lakes occur in shallow mountain ponds located mainly between 18º to 23°S (Zúñiga et al., 1999).Northern Chile is markedly arid, experiencing weak rains during the "Bolivian winter" of January and February.The ponds of the mountain and plains are all associated with saline deposits of volcanic origin (Chong, 1984) and brines of these saline lakes have relatively high sulphate concentrations (Zúñiga et al., 1991(Zúñiga et al., , 1994(Zúñiga et al., , 1999;;Gajardo et al., 1992, Table 3).The salinities of these ponds vary widely.In waters with salinity concentrations <90 g L -1 , the calanoid copepod Boeckella poopoensis is the dominant member of zooplankton (De los Ríos & Crespo, 2004;De los Ríos & Gajardo, 2010a, 2010b; De los Ríos-Escalante 2010).In lakes with water salinity concentrations >90 g L -1 , members of the genus Artemia are the dominant member of the zooplankton (Hurlbert et al., 1986;Williams et al., 1995).Predation by adult B. poopoensis on Artemia nauplii is probably the main factor reducing the abundance of the brine shrimps with salinity concentrations <90 g L - 1 (Hurlbert et al., 1986;Hammer & Hurlbert, 1992).Where Artemia do occur abundantly, the crustacean would play a key ecological role as the main grazer, through non selective filter feeding on the producer organisms (which includes halobacteria, cyanobacteria, diatoms and halophilic microalgae such as Dunaliella salina (Zúñiga et al., 1991(Zúñiga et al., , 1994;;Demergasso et al., 2003).These upland Artemia habitats are sites for feeding and nesting of aquatic birds such as Chilean flamingo (Phoenicopterus chilensis), Andean flamingo (Phoeni-coparrus andinus), James flamingo (Phoenicoparrus jamesi) and Wilson Phalarope (Phalaropus tricolor).The three species of flamingos are important for Artemia populations, because two of these species (P.andinus and P. jamesi) graze on phytoplankton and bacteria, and therefore probably compete directly with the brine shrimp for food sources.However, Chilean flamingos potentially would predate on brine shrimp because these waterfowl feed non selectively on zooplankton (López, 1990).Brine shrimp reproduce ovoviviparously only in permanent lakes with very high salinity concentrations.In these situations there is no cyst production and the population numbers decline over time with increasing salinity.The affected populations regenerate under optimal environmental conditions of low salinity concentrations from a few surviving individuals (Zúñiga et al., 1994(Zúñiga et al., , 1999)).Regarding dispersal, the inland saline lakes are located east and west of the Andes mountains between 18º to 23°S, an area within the migration route of flamingos.Flamingos have been implicated as an agent capable of dispersing brine shrimp.Indeed, dispersal by flamingos may explain the presence of A. franciscana in saline lakes of northern Chile (Gajardo et al., 1998, De los Ríos & Zúñiga, 2000), Argentina (Papeshi et al., 2000) and adjacent areas of Peru and Bolivia (Triantaphyllidis et al., 1998).
A. persimilis: the Chilean populations of A. persimilis occur mainly in southern Patagonia (Gajardo et al., 1998;De los Rios & Zúñiga, 2000;De los Ríos, 2005;De los Ríos & Gajardo, 2010a, 2010b), with biological studies having focused on Amarga lagoon, inside Torres del Paine National Park.The water bodies in this area inhabited by A. persimilis have high chloride and sulphate concentrations (Campos et al., 1996).According to Campos et al. (1996), the biotic components are mainly cyanobacteria and a few diatoms grazed by rotifers and brine shrimp.Again, the predator of Artemia is probably the Chilean flamingo P. chilensis (Soto, 1990;Campos et al., 1996).In the Patagonian sites, brine shrimp and copepods can coexist in spite of the different salinity tolerances of both groups (De los Ríos & Gajardo, 2010, De los Ríos-Escalante & Gajardo, 2010).The presence of A. persimilis in southern Patagonia may be due to dispersal via water birds migrating from central Argentina to southern Chile (Gajardo et al., 1998;De los Ríos & Zúñiga, 2000).Certainly, the very low altitude of the Andes mountains in the region would not constitute a barrier to migrating water fowl, and therefore to dispersal of brine shrimp.Further, A. persimilis probably shows optimal survival and fecundity in lower salinity concentrations and temperatures than A. franciscana (Sorgeloos et al., 1986).Lakes with low salinity concentrations and low temperatures are typically observed in southern Patagonia, and these conditions presumably suit better the presence of persimilis.

FUTURE DIRECTIONS
This review is concluded by discussing directions for future studies on Chilean brine shrimps, mainly with respect to their ecology and management.At present time the ecological information available is restricted or relies on inferences.Also, little published information is available concerning the management and use of these biological resources (Zúñiga & Wilson, 1996).The effects of exposure to ultraviolet radiation (UVR) (Cabrera et al., 1995;Villafañe et al., 2001) needs to be investigated, particularly the impacts regulating zooplankton communities and affecting mutation rates (Hebert et al., 2002;Friedberg, 2003).
Management: the increasing demand of Artemia cysts for aquaculture has caused high levels of cysts harvesting from the main source, Great Salt Lake, Utah, USA.A flow-on effect has been the artificial inoculation of cysts in saltworks in Brazil, Vietnam and other countries, and also the search for alternative brine shrimp strains and species to culture (Lavens & Sorgeloos, 2000).The increase of aquaculture activities had led to an increase in the importation of brine shrimp cyst into Chile.However, the uncontrolled use of exotic strains and species, may potentially pose a significant threat to many Chilean Artemia populations by displacement of native strains (De los Ríos & Gajardo, 2004).Unfortunately insufficient information is available on the use of Chilean brine shrimp populations for aquaculture, although some populations have relative good growth and survival response in controlled and semicontrolled conditions (Zúñiga & Wilson, 1996;De los Ríos, 2001).Nevertheless, the best results in studies of mass culture of Chilean brine shrimp were obtained using populations from coastal shallow ponds, because shrimp from these sources produce cysts in natural conditions (Zúñiga et al., 1999).Also, the brines of these habitats have ionic composition similar to seawater (Amat et al., 1994b;Zúñiga et al., 1999), representing favourable conditions for marine aquaculture because they do not need to divert energy to cope with different chemical conditions, and thereupon should grow and reproduce efficiently (Bowen et al., 1985).The opposite situation was reported for populations from the sulphate-enriched brines of inland lakes.Shrimp from these sources have low fecundity and growth rates when reared in seawater (Zúñiga & Wilson, 1996).
Consequently, local aquaculture activities based on brine shrimp will, in all likelihood, use stock from habitats with high chloride concentrations, such as A. franciscana from coastal ponds or saltworks, or A. persimilis from southern Patagonian lakes.In the case of A. persimilis from southern Patagonia, the shrimp inhabit regions with difficult weather conditions, namely heavy rainfall in winter and strong 100 km h -1 winds in summer (Soto et al., 1994;Campos et al., 1996).Aquaculture under such conditions may be economically difficult.Similar difficulties may apply for brine shrimp aquaculture based on saltworks in central Chile because the area sometimes experiences strong rains in winter (Niemeyer & Cereceda, 1984) that would generate considerable losses for aquaculture producers.
Finally, northern Chile presents at least two important advantages for brine shrimp aquaculture: low rainfall, and an environment rich in natural nitrate and phosphorus fertilizers (Chong, 1988).Another important advantage includes the abundance of native, high quality live foods for Artemia such as the halophilic microalgae D. salina (Gómez-Silva et al., 1990;Araneda et al., 1992aAraneda et al., , 1992b)).High yields have been achieved using shallow coastal strains in outdoor culture at intermediate production scales (Zúñiga & Wilson, 1996).The results from studies to date indicate that future directions for research into Chilean brine shrimp aquaculture must focus on achieving economical and technical advances for establishing intensive and extensive production scales.
Ultraviolet effect on brine shrimp: in recent years, levels of ultraviolet radiation (UVR) have been increasing substantially, in Chile (Cabrera et al., 1995) mainly in southern Patagonia (Villafañe et al., 2001) but also in the tropical Andes (Villafañe et al., 1999;Helbling et al., 2002).Ultraviolet radiation is an important mutagen, changing the molecular structure of DNA (Friedberg, 2003).Consequently, the biota of shallow aquatic habitats lacking photoprotective strategies to avoid or repair the damage caused by exposure to UVR, may be particularly susceptible to UVR-induced damage (Villafañe et al., 2001;Helbling et al., 2002).Since brine shrimp have many advantages for use in culture and in genetics (Gajardo & Beardmore, 2001), three lines of study into effects of UVR on brine shrimp are likely to produce useful results.
a) Studies at the cellular scale into the mutagenic effects of UVR on the nucleotide sequence of DNA may reveal genetic changes in successive generations.Such changes are known to occur in halophilic crustaceans (Hebert et al., 2002).Gajardo & Beardmore (1993) and Gajardo et al., (1995Gajardo et al., ( , 2004) ) described genetic isolation and differentiation of Chilean brine shrimp populations.It may be important, with respect to conservation issues, to ascertain whether populations with year-round exposure to high UVR levels, for example in tropical zones, have substantially higher mutation rates compared with populations from areas with exposure to low UVR levels.
b) A second line of studies would investigate the effects of UVR on individual organisms.The shallow ponds inhabited by brine shrimps typically have a maximum depth between 1-15 m (Zúñiga et al., 1999), and UVR penetrates to the bottom of the water column (Villafañe et al., 2001).Consequently, the resident zooplankton is exposed to high levels of UVR against which the organisms require protection, such as provided by photoprotective photorepair or antioxidant substances such as melanin, carotenoid pigments or ascorbic acid (Villafañe et al., 2001;Hessen et al., 2002).For example, freshwater Arctic daphnid crustaceans are exposed to high levels of UVR during summer, and synthezise and accumulate substances which provide protection against high levels of UVR.Boeckella titicacae (= B. gracilipes) from Lake Titicaca, in the tropical Andes (Helbling et al., 2002) synthezise a micosporine-like amino acid, and calanoids from shallow ponds in southern Patagonia also synthezise protective pigments (Rocco et al., 2002), for example.
Although the response of Artemia to UVR has not been studied, it is likely that marked red or orange coloration of juveniles and adult specimens of tropical latitudes (Zúñiga & De los Ríos, personal observations) have a photoprotective or photorepairing function.Thick chorionic membranes of cysts of brine shrimp from inland mountain habitats (Zúñiga et al., 1999) may also constitute evidence of exposure to high levels of UVR.These inland shrimp does not produce cysts under natural conditions, but under extreme controlled conditions they can produce a few cysts with a thick chorionic membrane (Zúñiga et al., 1999).This feature may be an adaptative response to high levels of insolation exposure and UVR, since similar results were described for cysts from tropical populations of brine shrimp (Amat, 1982).Elucidation of the effects of UVR on Artemia would seem to be a fruitful line of investigation to follow.c) A third line of studies would investigate the effects of UVR on the population structure and dynamics of Chilean brine shrimp.In marked contrast to the information concerning the effects of UVR on brine shrimp, much information has been published concerning daphnid exposure to UVR from northern hemisphere freshwaters.
Presumably, exposure to high levels of UVR radiation involves individuals affected in expending energy and metabolites to produce photoprotective substances (Hessen, 1996;Hessen et al., 1999).Given this possibility, exposure to UVR would cause mortality in different life stages, lower fecundity in adults, and slow growth rate of individuals.However, dissolved organic carbon (DOC) may be providing protection against UVR (Morris et al.,1995;De los Ríos, 2003).Many of the saline and brackish aquatic ecosystems of the Atacama desert and in southern Patagonia have a wide gradient of concentrations of DOC (De los Ríos, 2003).Consequently, it is reasonable to predict that there would be marked differences in the energy spent by individuals in developing photo-protection that would affect fecundity, individual growth, and absolute abundance of various populations (Rautio, 1998;Winder, 2001;Rautio & Korkhola, 2002a, 2002b).Indeed, integrated laboratory and field studies involving an array of brine shrimp natural sites and investigating the effect of variation in levels of protection provided by different concentrations of DOC protection against UVR damage, may be an important line of research to pursue in Chile from the sandpoint of conserving natural stocks of brine shrimp at a time of major changes in atmospheric conditions of planet Earth.
data No data No data No data No data No data No data Salar de Llamara 167 No data No data No data No data No data No data No data No data Plata Yape pools (data No data No data No data No data No data No data Pampilla pools 45 No data No data No data No data No data No data No data No data Colorado pools data No data No data No data No data No data No data Pichilemu saltworks 115 No data No data No data No data No data No data No data No data Amarga Lagoon (Torres del Paine) data No data No data No data No data No data No data References: 1) Amat et al. (1994b), 2)

Table 1 .
List and geographical location of sites in Chile with presence of Artemia populations in according to the literature.Tabla 1. Lista y localización geográfica de sitios en Chile con presencia de poblaciones de Artemia según la literatura.