Cnidaria , Hydrozoa : latitudinal distribution of hydroids along the fjords region of southern Chile , with notes on the world distribution of some species .

The coast of continental Chile extends over almost 4,200 km and covers a large part of the southeast Pacific. While the coastline between Arica (18°20' S) and Chiloé Island (ca. 41°30' S) is more or less straight, the region between Puerto Montt (ca. 41°30' S) and Cape Horn (ca. 56° S) is highly structured and presents a large number of islands, channels and fjords. This extension is formed by two parallel mountain ranges, the high Andes on Chile’s eastern border, and the coastal mountains along its western edge which, in the area of Puerto Montt, drop into the ocean with their summits, forming the western channels and islands, while the Andes mountain range constitutes the continental fjords. The Chilean oceanographic institute SHOA calculated that the thousands of islands, channels and fjords enlarge the coast of this region to a length of almost 90,000 km (map scale).

The coast of continental Chile extends over almost 4,200 km and covers a large part of the southeast Pacific.While the coastline between Arica (18°20' S) and Chiloé Island (ca.41°30' S) is more or less straight, the region between Puerto Montt (ca.41°30' S) and Cape Horn (ca.56° S) is highly structured and presents a large number of islands, channels and fjords.This extension is formed by two parallel mountain ranges, the high Andes on Chile's eastern border, and the coastal mountains along its western edge which, in the area of Puerto Montt, drop into the ocean with their summits, forming the western channels and islands, while the Andes mountain range constitutes the continental fjords.The Chilean oceanographic institute SHOA calculated that the thousands of islands, channels and fjords enlarge the coast of this region to a length of almost 90,000 km (map scale).
During the last three decades, an important number of papers dealt with the biogeography of Chilean benthic invertebrates.While most studies treated a single taxon (e.g.Moyano 1991;Desqueyroux-Faúndez 1994;Ojeda et al. 2000;Häussermann and Försterra 2005;Montiel et al. 2005;Häussermann 2006), some summarize available data on biogeography and oceanographic processes (e.g.Viviani 1979;Brattström and Johanessen 1983;Castilla et al. 1993;Lancellotti and Vasquez 1999;Fernandez et al. 2000;Camus 2001).Most studies have proposed two main biogeographic regions within Chile, the Peruvian or warm-temperate Province between the Peninsula Illescas (or Bayovar) (ca.6° S) and Chiloé Island, and the Magellanic or cold-temperate Province, between Chiloé Island and Cape Horn.Viviani (1979) and Pickard (1971) subdivided the Magellanic Province into three regions: the Northern Patagonian Zone, from Puerto Montt to the Peninsula Taitao (ca.46°-47° S), the Central Patagonian Zone to the Straits of Magellan (ca.52°-53° S), and the Southern Patagonian Zone south of the Straits of Magellan.A recent study, including a wide set of invertebrates from the intertidal to 100 m depth (Lancellotti and Vasquez 1999), negates the widely assumed faunal break at 42° S, and proposes a Transitional Temperate Region between 35° and 48° S, where a gradual but important change in the species composition occurs.
Since 2005, in the framework of an inventory of the benthic biodiversity of the Chilean fjords region, we have organized a series of four, mainly vessel-based expeditions ("Huinay Fiordos 1 to 4") with three to seven participants each (Försterra et al. 2006;Willenz et al. 2007): the first focused on Chiloé Island and Guaitecas Archipelago, while the second and third took us to the fjords and channels of the Central Patagonian Zone (48°-52° S), and the fourth again to the Northern Patagonian Zone (encompassing the Chiloé Island, Chaitén, and Raul Marin Balmaceda).Due to the remoteness and inaccessibility of the more exposed channels and islands of the Northern and Southern Patagonian Zone, no or a very few sampling could be carried out in these areas.Additional hydroid samples were collected during a continuous survey of the benthic invertebrate fauna of fjord Comau, and some results are already available in Galea et al. (2007).A map of the studied area with the location of collection sites for hydroids is available in Figure 1.A total of 57 species of hydroids were found.They were assigned to six families of athecates and thirteen families of leptothecates.A list of species and their biogeographical distribution are summarized in Table 1.The latitudinal distribution along the studied area is presented in Figure 2. The lesser known species are illustrated in Figures 3-4.
Four species are likely to have a bipolar distribution, including the sub-polar to temperate waters of both hemispheres: Hydractinia cf.borealis, Egmundella gracilis (Figure 3B), Grammaria abietina and Halecium fraseri (Figure 3H).Both the polyp and medusa stages of H. borealis were previously recorded from the British Isles, Iceland, North Sea, and the Atlantic coasts of North America (Schuchert 2001b).
Egmundella gracilis was for instance recorded from the Pacific coast of Canada (Stechow 1923) and southern Chile (Galea 2007).Grammaria abietina is a circumpolar species, ranging southward to the North Sea in the eastern Atlantic, and to southern New England in the Western Atlantic.In the southern hemisphere, it was recorded near Crozet, Kerguelen and Falkland Islands, Tierra del Fuego, and Patagonia (Schuchert 2001b).Halecium fraseri was found from the eastern Pacific from Moresby Island to San Juan Archipelago (Ralph 1958) and southern Chile (Leloup 1974;Galea et al. in press); it was equally reported from the northwestern Atlantic, from Narragansett Bay, south of Hope Island (Fraser 1944).
The records of the following eleven species are relatively scattered around the world.Both the polyp and medusa stages of Bougainvillia muscoides were previously found in the boreal waters of the Atlantic and Pacific Oceans, the Arabian Gulf and off Mozambique (Buecher et al. 2005).Galea (2007) assigned abundant material of a Bougainvillia species to B. pyramidata, mainly based on the morphology of the mature medusa.However, it is now recognized that, in both the polyp and medusa stages, intermediate forms between B. muscus and B. pyramidata may occur (Schuchert 2007), and the distinction between the two is sometimes very difficult using morphological criteria.It is therefore possible that the present material assigned to B. pyramidata may correspond instead to B. muscus, a widespread species found in tropical and temperate waters of the world oceans (Schuchert 2007).There are records of B. muscus from the southern Pacific (Schuchert 1996), while Bougainvillia pyramidata was mainly recorded from the Atlantic, on the western coast of British Isles (Russell 1953).Besides the present record from Chile, Eudendrium cf.nambuccense was initially reported from eastern and south-eastern Australia (Watson 1985), but there are additional records from the Pacific coast of Brazil (Nogueira et al. 1997;Marques 2001).Hybocodon chilensis, initially described from Chile (Hartlaub 1905), was also reported from New Zealand (as H. prolifer in Schuchert 1996, see also Galea 2006b).
Campanulina pumila was mainly recorded from the northern hemisphere, e.g.North Sea, North Atlantic, Pacific coasts of North America (Cornelius 1995a), and Greenland (Schuchert 2001b).The present record from southern Chile may suggest a bipolar distribution of this species.Hebella cf.dispolians, is here only tentatively identified based on its parasitic habit (hydrothecae arising from the hydrothecal apertures of Symplectoscyphus subdichotomus); both its occurrence and taxonomic status are poorly known, with only two previous records, one from India (Warren 1909) and another from South Africa (Millard 1975).The chief area of distribution of Hebella striata is represented by the seas around South America, with records from Argentine Patagonia (Vervoort 1972;El Beshbeeshy 1991), Crozet (Millard 1977), Kerguelen (Vanhöffen 1910), and Falkland Islands (Hartlaub 1905;Blanco 1982), Burdwood Bank (Jäderholm 1905;Ritchie 1907), Magellan Strait (Allman 1888;Hartlaub 1905;Vervoort 1972), Pacific coast of Chile (Hartlaub 1905;Leloup 1974;Galea 2007), and the adjacent Antarctic seas (Totton 1930).Sertularella fuegonensis (Figure 4A) was originally found from Tierra del Fuego (El Beshbeeshy 1991;Vervoort 1972, as S. picta, p. 114, fig 35A-B), but additional records are from New Zealand (Vervoort and Watson 2003).Sertularella gayi is widely distributed in the Mediterranean and eastern Atlantic (Bouillon et al. 2004), but also on the Pacific coast of Argentina (Blanco 1982); it is presently recorded from southern Chile.Symplectoscyphus subdichotomus is widely distributed along both Atlantic and Pacific coasts of South America, e.g.Argentina (Blanco 1967a;El Beshbeeshy 1991;Genzano and Zamponi 2003), Chile (Hartlaub 1904;Leloup 1974;Galea 2007), Magellan Strait (Hartlaub 1905;Vervoort 1972), south-western Atlantic from an area situated between Tierra del Fuego, Isla de Los Estados and the Falkland Islands (Vervoort 1972), Kerguelen, Crozet (Millard 1977;Stepanjants 1979), and Falkland Islands (Jäderholm 1905).This species also penetrates into the Antarctic seas (Blanco 1967b).Additional records of S. subdichotomus are mentioned from Australia (Ralph 1961) and New Zealand (Vervoort and Watson 2003).Campanularia mollis has a complicated synonymy and was found on the Pacific coast of North America ( Some authors (Pickard 1971;Viviani 1979;Lancellotti and Vasquez 1999;Häussermann and Försterra 2005) hypothesized a faunal break at the Peninsula Taitao and the Golfo de Penas (ca.48° S), at least for shallow water species of the inner fjords, accompanied by a significant change in the species composition.This hypothesis seems to be verified for a certain number of hydroids, e.g.E. cf.scotti, L. longitheca, G. abietina, S. magellanicus, K. magellanica, P. repens and C. agas, which presently have not been found northerly to 48° S along the Pacific coast of Chile.These species are known to have a sub-Antarctic and/or Antarctic distribution, so they were not expected to be found north of this limit.Conversely, the temperate species C. caspia and C. eximia seem to be present only north of the Golfo de Penas.
Additionally, a transition was presently observed in two members of the genus Symplectoscyphus: S. filiformis was widely found between 42-44° S, while S. subdichotomus totally replaced the former southerly to 47-48° S.However, S. filiformis was originally described from Puerto del Hambre (ca.53° S, Allman 1888), and Leloup (1974)  fjordlandicum, H. fraseri) were so scantly reported in the literature, that their geographical distribution is poorly known.
However, the absence of sampling between 43°50' and 47°50' S, and the very few records of several species, prevent us to associate with certainty the faunal-break hypothesis to the hydroids.
No typical representatives of the Antarctic hydroid fauna were recorded during the present study, i.e. members of the genera Schizotricha, Oswaldella, Antarctoscyphus and Staurotheca (see Peña Cantero and García Carrascosa 1999).
In conclusion, numerous hydroid species show affinities partly with the cold-temperate Magellan region, and partly with Antarctica.The remaining species have either a scattered distribution around the world or are (near) cosmopolitan.

Figure 1 .
Figure 1.Map of the explored areas during "Huinay Fiordos 1-4" Expeditions and the fjord Comau, showing location of collection sites for hydroids.

-Figure 2 .
Figure 2. Latitudinal distribution of hydroid species within the studied area.No sampling has been carried out between 43°50' and 48°10' S.