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I examine the natural barriers to distribution and colonization that have shaped the Galapagos marine invertebrate biota. While diversity is high for some groups, such as hydroids and bryozoans, it is low for many others. Porcelain crabs and molluscs are examples with reduced or unbalanced representation in Galapagos, resulting from their dependenc...
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... 11 non-endemic Galapagos porcellanids is over- whelmingly with the Panamic province, which extends from the Gulf of Tehuantepec (southern Mexico) to the Gulf of Guayaquil (southern Ecuador) or Paita in northern Peru (Briggs 1974) ( Fig. 4). Seven of these 11 are shared with the Cortez–Mexican province and one is shared with the Peruvian province. None of them occurs north of the Cortez–Mexican province. Of the 92 species of porcellanids in the east Pacific, 32 occur in Ecuador and 41 in Pacific Colombia (Table 3). If we accept these as the major source pool for the Galapagos fauna, with a combined 42 species, we can ask why only 14 species occur in Galapagos. Harvey (1991) describes two principal elements that could have contributed. One is the short dispersal phase during larval development; compared to other decapod crustaceans, porcellanids produce few large eggs with accelerated larval development and are thus poorly suited for long-distance oceanic transport. Second, dispersal of porcellanid larvae, like any planktonic larvae, is wholly dependent on the pattern of oceanic currents. Porcellanid larvae hatched in the central Pacific would have to be transported at least at 10 times the rate of the NEC to reach Galapagos or any other islands in the east Pacific (Harvey 1991). For porcelain crabs, the East Pacific Barrier is complete: no Indo-Pacific porcellanids have established populations in the east Pacific and no east Pacific porcellanids are known to have successfully established populations in the Indo-Pacific. Additional barriers are the north and south current- temperature barriers (Fig. 2). From California southwards, the current is unfavorable most of the year and the water too cold for tropical porcelain crabs. From the south, the only Galapagos porcelain crab with Peruvian affinity, Petrolisthes armatus, is known from a single record and considered “extralimital” by Haig (1960). It has not appeared in recent collections. A possible explanation for the absence of porcellanids of Peruvian affinity is that the POC, which gives rise to the SEC that flows directly through Galapagos, is separated from the PCC by the Peru Coastal Countercurrent (Fig. 1), which acts as a barrier to larval dispersal northward from coastal Peru (Fig. 2). Also, because the continental shelf along Peru is narrow and strong currents sweep offshore, pelagic larvae would be swept out to sea beyond a site for ...
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... 11 non-endemic Galapagos porcellanids is over- whelmingly with the Panamic province, which extends from the Gulf of Tehuantepec (southern Mexico) to the Gulf of Guayaquil (southern Ecuador) or Paita in northern Peru (Briggs 1974) ( Fig. 4). Seven of these 11 are shared with the Cortez–Mexican province and one is shared with the Peruvian province. None of them occurs north of the Cortez–Mexican province. Of the 92 species of porcellanids in the east Pacific, 32 occur in Ecuador and 41 in Pacific Colombia (Table 3). If we accept these as the major source pool for the Galapagos fauna, with a combined 42 species, we can ask why only 14 species occur in Galapagos. Harvey (1991) describes two principal elements that could have contributed. One is the short dispersal phase during larval development; compared to other decapod crustaceans, porcellanids produce few large eggs with accelerated larval development and are thus poorly suited for long-distance oceanic transport. Second, dispersal of porcellanid larvae, like any planktonic larvae, is wholly dependent on the pattern of oceanic currents. Porcellanid larvae hatched in the central Pacific would have to be transported at least at 10 times the rate of the NEC to reach Galapagos or any other islands in the east Pacific (Harvey 1991). For porcelain crabs, the East Pacific Barrier is complete: no Indo-Pacific porcellanids have established populations in the east Pacific and no east Pacific porcellanids are known to have successfully established populations in the Indo-Pacific. Additional barriers are the north and south current- temperature barriers (Fig. 2). From California southwards, the current is unfavorable most of the year and the water too cold for tropical porcelain crabs. From the south, the only Galapagos porcelain crab with Peruvian affinity, Petrolisthes armatus, is known from a single record and considered “extralimital” by Haig (1960). It has not appeared in recent collections. A possible explanation for the absence of porcellanids of Peruvian affinity is that the POC, which gives rise to the SEC that flows directly through Galapagos, is separated from the PCC by the Peru Coastal Countercurrent (Fig. 1), which acts as a barrier to larval dispersal northward from coastal Peru (Fig. 2). Also, because the continental shelf along Peru is narrow and strong currents sweep offshore, pelagic larvae would be swept out to sea beyond a site for ...
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... has long been recognized that the flora and fauna of the Galapagos terrestrial environment are unbalanced compared to South American mainland biota. While some animal groups, such as reptiles, seabirds, marine mammals and land snails are well represented, others, such as amphibians, song birds, land mammals, aquatic insects, and freshwater fish are poorly represented or absent (Jackson 1993). Groups with obvious adaptations for dispersing long distances tend to be disproportionately common. Is this disharmonic representation also present in the marine environment of Galapagos? Answering this is hampered by uneven taxonomic investigations in the marine environment of the equatorial east Pacific, where some invertebrate groups have received much more attention than others. Before the introduction of scuba diving in the 1950s, explorations of subtidal life depended mainly on dredging, a notoriously clumsy and non-selective way to collect marine invertebrates. Nevertheless, the extensive collections of earlier expeditions, together with more recent surveys, allow us to begin to compare the marine biota of Galapagos with that of the South American mainland coast. Diversity is high for groups with good dispersal, such as hydroids (Calder et al 2003), bryozoans (Banta 1991), cirripedians (Zullo 1991) and caridean shrimps (Wicksten 1991, Wicksten & Hendrickx 2003), but considered low for many other groups, such as molluscs (Finet 1991, 1994), echinoderms (Maluf 1991), benthic polychaetes (Blake 1991), hermatypic corals (Glynn 2003), and porcelain crabs (Haig 1960, Harvey 1991). Table 1 sum- marizes the number of species and degree of endemism in Galapagos marine groups. The proportion of both shore- dwelling and deep-water endemic marine organisms totals about 18%; this is comparable to other oceanic islands and archipelagoes, which range from 0 to 20% (Bustamante et al. 2002). Trans-oceanic dispersal is heavily influenced by oceanic currents and the distribution of islands that may act as stepping stones. The Galapagos archipelago lies at the confluence of three oceanic currents (Fig. 1). The main current is the South Equatorial Current (SEC) which is fed principally by the cool (20–24°C) Peru Oceanic Current (POC). The Peru Coastal Current (PCC) carries cold water (as low as 13°C) but is separated from the POC by the Peru Coastal Countercurrent. When the POC reaches Galapagos its temperature is 18–22°C. The SEC is supported throughout the year by southeasterly trade winds that vary in strength seasonally. It is a strong current during much of the year, traveling 80–160 km per day. The Equatorial Undercurrent upwells along the western wall of the Galapagos Platform, bringing cold water (14–16°C) to the western islands. It is also nutrient rich, producing great productivity in this area. The Panama Current, a composite of the California Current and the North Equatorial Countercurrent, is a slow-moving current bringing to Galapagos warm water (26–29°C), low in salinity and low in nutrients, usually in January when the southeasterly trade winds slacken (Banks 2002, Chavez & Brusca 1991, Wyrtki 1985). During El Niño years, this current is believed to transport Panamic species to the Galapagos. A consequence of this complex current system is marked variation in oceanographic conditions across the archipelago. During El Niño years, regional variation in conditions disappears as water temperatures rise above 25°C. Oceanic currents make possible the dispersal of species between widely separated areas, especially species cap- able of long-distance larval transport. Currents also serve as barriers to dispersal. The principal barriers to east– west distribution are the Central American land barrier to the east and the E Pacific Barrier to the west (Fig. 2). ...
Citations
... Finally, the TEaP province includes continental (e.g., MTP, Nic) and oceanic (e.g., Rev, Cli) ecoregions, whereas Gala is an entirely oceanic province. Gala province is mainly influenced by the South Equatorial Current, fed principally by the cool (SST = 20-24 • C) Peru Oceanic Current and the Equatorial Undercurrent upwells, bringing cold water to the western islands and producing great productivity in this area (Fiedler and Talley, 2006;Hickman, 2007). The average temperature of Gal province is within the average ranges of the TEaP province (Fiedler and Talley, 2006), and for this reason, they share a high number of species (72%). ...
... The ecoregions within WTNP and Gala cover a minor geographical extension compared to those in TEaP. For this reason, the environmental conditions (i.e., SST) and the environmental heterogeneity within these provinces remain relatively homogeneous (Fiedler and Talley, 2006;Hickman, 2007;Lluch-Cota et al., 2007), promoting β Is . On the other hand, TEaP has variable environmental conditions and heterogeneity due to its extensive geographic coverage. ...
... The higher β RCs between CIs-EGI may be related to the low number of shared species (15) and faunistic uniqueness since several species are restricted to EGI but absent in other ecoregions (Amphiophiura irregularis, Amphiura verticillata, and Ophiophragmus disacanthus). The Galapagos archipelago has been recognized as an area with a high degree of endemism of marine invertebrates, including echinoderms (8% of total shallow echinoderms) as a result of allochthonous and autochthonous endemics (Hickman, 2007). More thoughtful sampling has overturned the pattern, and some Ophiuroidea species considered ''endemic'' to Galapagos are now recognized to have a wider distribution. ...
Despite the high relevance of echinoderms in the Southern Mexican Pacific coral reef systems, there is no detailed analysis of
their regional diversity. Based on records from field surveys and literature, this work analyzed for the first time the echinoderm
species composition in coral reef systems in the Southern Mexican Pacific, evaluating their richness and distribution patterns. Fifty-two species represent the region (six Asteroidea, eight Echinoidea, 15 Ophiuroidea, and 23 Holothuroidea), a more
significant number than other coral reef systems in the Mexican Pacific and Central America. New records are presented at
the region, zone, and site level. At the zone level, the highest species richness occurred in Huatulco (52 species), followed by
Ixtapa (45), Acapulco and Puerto Ángel (33), and Puerto Escondido (23). At the site level, La Entrega had the highest number of species (32), while various sites in Acapulco had <10 species. The species richness in the region showed considerably high representativeness since the non-parametric estimators suggested a potential increase of ~10% more species; a more significant percentage is expected in the Acapulco zone (47.5%). All echinoderms had 100% representativeness at the class level, except for Holothuroidea. It is recommended to use as many sampling methods and as many substrates as possible during different seasons and time days to contribute to increasing representativeness. Acapulco had an average taxonomic distinctness different from that predicted by regional models and an echinoderm assemblage more dissimilar from the other areas. The latter may be the product of the scarce sampling effort carried out in Acapulco and probably because it has one of the most degraded coral reef systems within the study area.
... Unhindered colonization of free substratum and increased overgrowth and competition with corals may change the dynamics of Darwin benthic ecosystems and may result in profound habitat alterations on the only framework coral reef of the Galapagos [47]. This alga increased in abundance and overgrew corals on the reef since 2012, ultimately raising fears that a phase-shift from coral to algae [4,[48][49][50][51] might be imminent. However, from 2019 onwards algae populations strongly contracted and while not having returned to baseline level, there is currently low risk of corals being displaced. ...
Coral reefs are rare in the Galapagos and there is concern that, like in many areas around the world, they may be degrading due to increasing anthropogenic pressure, which can cause changes and reorganizations of structure and function with associated phase shifts. Algae of the genus Caulerpa J.V. Lamouroux, 1809 are known as widespread and persistent marine invaders. They grow rapidly, particularly in disturbed areas where they can opportunistically monopolize substratum and compete with native species, thus reducing biodiversity. Caulerpa chemnitzia increased in abundance and overgrew corals on the reef since 2012, ultimately raising fears that a phase-shift from coral to algae might be imminent. However, from 2019 onwards algae populations strongly contracted and while not having returned to baseline level, there is currently low risk of corals being displaced. Visual censuses were conducted on a yearly basis since 2004 using sample quadrats (0.5 x 0.5m) every 5 m along a 50-m-long transects at a depth of 6–15 m at 5 permanent subtidal ecological monitoring sites around Darwin. In addition, 10 m photo-transects were taken using a graduated meter-long measuring stick in the centre of the frame in 2012, 2014, 2016, 2017, 2018 and 2021 at a depth of 15m at Wellington reef. The authors hypothesize that this species could have expanded its distribution over Wellington Reef because of its known morphological plasticity due to a response to change in the environment, in this case high temperature and low nutrients. As ENSO events are predicted to increase in intensity and frequency due to the impact of climate change it is important to develop and implement a functional alert system. Early Detection Rapid Response (EDRR) protocols are recommended to avoid climate driven Non-Indigenous Species (NIS) entering the GMR or for native species becoming invasive due to warming-related phase shifts.
... [47,48]. This assumption contrasts with the latter study by Hickman, who stated that octocorals have a wide range of colonization niches and are not limited to shallow waters [49], as many of them thrive under rocks, in ledges, and in caves where sunlight is absent or minimal. ...
The Equatorial Front, in the southern part of the Tropical Eastern Pacific (TEP) region, has been characterized as a hotspot of functional biodiversity due to the mixing of warm and cold waters. Nevertheless, the biogeographic patterns for some organisms, such as octocorals, remain unknown in some coastal regions. Therefore, we aimed to assess the distribution of two common octocoral genera in this area, Muricea and Leptogorgia, including 14 species based on museum specimen records, along the mainland coast of Ecuador. Statistical analyses were performed on the environmental and geographical patterns (Sea Surface Temperature (SST), bathymetry, chlorophyll (CHL-a), and Photosynthetic Active Radiation (PAR)) that influence the Equatorial Front, which is subdivided into five biogeographic regions. Our results showed two hotspots of octocoral biodiversity. The SST was found to be the main environmental factor related to octocoral distribution along the Equatorial Front. Finally, the highest abundance of Muricea over Leptogorgia suggests the former species' higher resilience to thermal fluctuations. We discuss the possible role of substrates at suitable depths, active photosynthetic radiation, and temperature in the occurrence of octocorals in the two hotspots.
... data). This appears in contrast at least to the invertebrate macrofauna of the Galapagos Islands, which instead shows very strong Panamian affinities (Hickman, 2009). We are indeed far from understanding the patterns of distribution and dispersal of meiobenthic Platyhelminthes, and more in general, of the biogeographical patterns of meiofaunal taxa. ...
Eight new species of Duplominona (Platyhelminthes, Proseriata, Monocelididae) are described from the Pacific coast of Panama. They differ from their congeners in the detailed morphology of hard structures associated with the copulatory organ. Duplominona basidilatata n. sp. has a cirrus provided with 5–6 rows of triangular spines, 3–8 μm long, with a large, flat, poorly sclerotized basis. D. hystricina n. sp. has 10–12 rows of needle-shaped spines, 3.5–15 μm long, with a swollen basis. The cirrus of D. hyperhystricina n. sp. is provided with 20–25 rows of slender spines 1.5–9 μm long, with a recurved distal tip. In D. veracruzensis n. sp., cirrus spines increase abruptly in size, from 1.5–2 μm to 6–7 μm. D. uniserta n. sp. has a very long seminal vesicle and a small cirrus, provided with one girdle of hook-shaped spines, 3–5 μm long. D. macrodon n. sp. has one girdle of large, triangular spines, 8–18 μm long. Both D. trimera n. sp. and D. pseudotrimera n. sp. have a tripartite tail, and their cirrus is provided with a stylet. In D. trimera n. sp., the stylet is surrounded by 15–20 rows of spines, 6.5–10 μm long, while D. pseudotrimera n. sp. has 6–8 rows of large spines, 7–22 μm long. D. uniserta n. sp. and D. aduncospina Curini-Galletti, 2019 from the Caribbean coast of Panama have few rows of morphologically nearly identical spines, and are possible candidates as trans-isthmian geminate species. The presence of species with a tripartite tail on both sides of the Isthmus of Panama suggests the possibility of further geminate species pairs; however, no support could be obtained on the basis of the morphology of their hard structures. Five of the eight new species of Duplominona have been found in a single locality, and the diversity of genus along the Pacific coast of Panama may be far higher than present contribution suggests.
... It is possible that the association of the Pacific Ocean currents and the sea surface temperature (SST) of the region are enough to act like genetic barrier and to delimit two O. mimus populations. The Panama tropical current moving southward contrasts with the cold Humboldt current moving northward; thus, the SST in the Panamanian province typically exceed 20°C while in the Peruvian province the temperature is, usually, lower than 20°C (Hickman Jr. 2009;Montecinos et al. 2003). ...
The population genetic structure of a species is frequently shaped by biogeographic barriers that prevent the movement of individuals from one genetic population to another. Although Octopus mimus Gould, 1852 was reported to inhabit the shallow marine waters of the Peruvian province, recent studies suggest its synonymy with O. hubbsorum Berry, 1953 from the Panamanian and the Cortez provinces where it is the main octopus species caught in the artisanal fishery. The aim of the present study was to assess the genetic variability of O. mimus and to determine the presence of population structure across three sampled regions of the eastern Pacific Ocean using the mitochondrial marker cytochrome c oxidase subunit I. The hypothesis that the biogeographic boundary between the Panamanian and Peruvian provinces acts as a genetic break was further tested and recognized by the conformation of two phylogenetic clades and two haplogroups. Results indicate that these lineages are demographically independent populations of O. mimus and do not represent different species as evidenced by the Generalized Mixed Yule Coalescent method. The oceanographic processes have apparently allowed enough genetic flow along the Pacific coast yielding low but significant levels of genetic structure (FST = 0.16, p < 0.05) as seen in some fish populations.
... The GMR is influenced by the convergence of three major currents that contribute to its unique environmental conditions favouring its high biodiversity (Muromtsev 1963, Banks, 2002, Hickman 2009). The South Equatorial Current flows westward and shows a marked seasonality. ...
The genus of benthic dinoflagellates Ostreopsis is of particular interest because some species negatively impact human health and coastal marine ecosystems. Ostreopsis populations from a remote area, such as the Galapagos Marine Reserve with its unique biodiversity, can provide significant data. Samples of epibionthic dinoflagellates were collected from two islands (Santa Cruz and Santa Fé) in 2017. Species of the genera Gambierdiscus, Amphidinium, Coolia and Ostreopsis were found. Ostreopsis strains were isolated to characterize their morphology, molecular biology and toxicity. Three different morphotypes of Ostreopsis based on dorsoventral and width diameters (n=369) were distinguished. The small cell morphotype was dominant in ten samples, with abundances of up to 33405 cells g-1 fresh weight of macroalgae. A total of 16 strains were isolated from field samples with subsequent polymerase chain reaction amplifications of rDNA, 5.8S rDNA and internal transcribed space regions; 13 strains (small cell morphotype) clustered in the O. cf. ovata Atlantic/Indian/Pacific clade; and 3 strains (large cell morphotype) clustered in the Ostreopsis lenticularis genotype from the type locality. The strains proved to be non-toxic. The presence of these genera/species represents a potential threat to marine ecosystems, and it is thus important to consider benthic species in the surveillance of harmful algae blooms in the reserve.
... The zone between these two currents is called the equatorial undercurrent (Crumwell Current) and it is characterized by a strong thermal and salinity gradient which goes through considerable seasonal variations. (Figure 10) [59]. ...
... Currents affecting the Ecuadorian coast [59]. ...
This thesis describes the isolation and identification of marine natural products from five zoantharian species collected off the Marine Protected Area El Pelado located in Santa Elena, Ecuador. A new family of 2-aminoimidazole alkaloids named terrazoanthines A-C were identified from Terrazoanthus patagonichus. Terrazoanthines A and B are characterized by the presence of the 2-aminoimidazole ring fused to a cyclohexane. Additionally, two zoanthoxanthin derivatives named zoamides E and F were isolated from the sister species Terrazoanthus cf. patagonichus. Then, four ecdysteroids derivatives named ecdysonelactones were obtained from Antipathozoanthus hickmani. These compounds feature a γ-lactone ring fused to ring A of the ecdysteroid skeleton. Further investigations on this organism led to the identification of four halogenated tyrosine derivatives named valdiviamides A-D and characterized by the presence of iodine and bromine atoms in the phenol ring. The bioactivity study revealed valdiviamide B to have moderate activity against the liver cancer cell line (HepG2) with an IC50 value of 7.8 µM. Additionally, two halogenated tyramine derivatives containing iodine and bromine atoms were identified from Parazoanthus darwini. The chemical investigation of Zoanthus cf. pulchellus allowed the identification of two members of the bioactive family of zoanthamine alkaloids. These compounds revealed neuroinflammatory activity in microglia BV-2 cells with high inhibitory effects in reactive oxygen species (ROS) and nitric oxide (NO) generation.
... Its zoning scheme has been recently reviewed and updated to include larger no-take zones. It consists of a mix of temperate, upwelling and tropical environments yielding a diverse assemblage of marine species with endemism ranging from 8 to 67% (Bustamante et al. 2000;Hickman 2009) in five distinctive bioregions (Edgar et al. 2004). Both introduced species and fishing activities pose threats to the overall health of the reserve and increased maritime traffic may lead to further introductions (Campbell et al. 2015;Keith et al. 2016). ...
Galápagos is one of the most pristine archipelagos in the world and its conservation relies upon research and sensible management. In recent decades both the interest in, and the needs of, the islands have increased, yet the funds and capacity for necessary research have remained limited. It has become, therefore, increasingly important to identify areas of priority research to assist decision-making in Galápagos conservation.
This study identified 50 questions considered priorities for future research and management. The exercise involved the collaboration of policy makers, practitioners and researchers from more than 30 different organisations. Initially, 360 people were consulted to generate 781 questions. An established process of preworkshop voting and three rounds to reduce and reword the questions, followed by a two-day workshop, was used to produce the final 50 questions. The most common issues raised by this list of questions were human population growth, climate change and the impact of invasive alien species. These results have already been used by a range of organisations and politicians and are expected to provide the basis for future research on the islands so that its sustainability may be enhanced.
... Isla del Coco is located at an area seasonally influenced by the Pacific North Equatorial Countercurrent (NECC) from May to October, which intensifies during El Niño phenomena (Lizano, 2008). A stronger Pacific NECC can enhance the eastward dispersal of marine larvae, including those of tropical reef fishes (Glynn & Ault, 2000;Robertson, 2001;Hickman, 2009;Acuña-Marrero & Salinas-De-León, 2013). Craig (2008) associated eastward dispersal of a surgeonfish species from the western Indian Ocean to Chagos via direct larval transport during El Niño phenomena. ...
Acanthurus guttatus is distributed from the Maldives to the Hawaiian Archipelago and the Pitcairn Islands, and as north as Ryukyu Islands and as south as New Caledonia. The only known locality in the Eastern Tropical Pacific is Clipperton Atoll where three vagrant specimens have been observed. On June 2016 and April 2017 small groups of A. guttatus were observed and photographed during SCUBA diving and snorkeling surveys for touristic suitability at Isla del Coco National Park, Costa Rica. Six specimens of A. guttatus were observed swimming over shallow rocky reefs at Isla del Coco, a volcanic island located in the Eastern Tropical Pacific. This study represents the first record of A. guttatus at Isla del Coco, the second known location of occurrence in the Eastern Tropical Pacific, and the easternmost known range for the Whitespotted surgeonfish.
... Its zoning scheme has been recently reviewed and updated to include larger no-take zones. It consists of a mix of temperate, upwelling and tropical environments yielding a diverse assemblage of marine species with endemism ranging from 8 to 67% (Bustamante et al. 2000;Hickman 2009) in five distinctive bioregions (Edgar et al. 2004). Both introduced species and fishing activities pose threats to the overall health of the reserve and increased maritime traffic may lead to further introductions (Campbell et al. 2015;Keith et al. 2016). ...
Galápagos is one of the most pristine archipelagos in the world and its conservation relies upon research and sensible management. In recent decades both the interest in, and the needs of, the Islands have increased, yet the funds and capacity for necessary research have remained limited. It has become, therefore, increasingly important to identify areas of priority research to assist decision-making in Galápagos conservation.This study identified 50 questions considered priorities for future research and management. The exercise involved the collaboration of policy makers, practitioners and researchers from more than 30 different organisations. Initially, 360 people were consulted to generate 781 questions. An established process of preworkshop voting and three rounds to reduce and reword the questions, followed by a two-day workshop, was used to produce the final 50 questions. The most common issues raised by this list of questions were human population growth, climate change and the impact of invasive alien species. These results have already been used by a range of organisations and politicians and are expected to provide the basis for future research on the Islands so that its sustainability may be enhanced.
