Post by Cyberguppy on Aug 18, 2005 15:22:08 GMT 10
Article taken from : members.cox.net/newcomb1/endlers.html
Go to site for photo's maps, endlers collectors and bibliography.
Prof. John A. Endler collected Poecilia sp. now, "Endler's Livebearer" in 1975 in Laguna de Patos, Cumana, in northeastern Venezuela (see map above). He found these fish in warm (81 degrees F) , hard water which is very green with unicellular algae which, along with other plankton such as diatoms, nekton, and filamentous algae make up part of their food. See Armando's page for more information on the area and water.
Dr. Endler gave a stock of Poecilia sp. "Endler's" to Dr. Donn Eric Rosen, the then Curator of Ichthyology at the American Museum of Natural History, who was going to name it (but died a few years later). Dr. Rosen gave some of the stock to a mutual friend of Dr. Endler, Dr. Klaus Kallman, then of the New York Aquarium, and a famous fish geneticist. Dr. Kallman introduced it to the German aquarium community. Many of the European group are hybrids of Endler's mixed with guppies of various breeds. Dr. Endler noted the extreme variety of colors in the wild were eliminated by the time they reached the aquist's community. He also commented that my original pictures reflected this inbred characteristic of many kept groups of fish, homozygousity, that is, they breed true to one color pattern, or phenotype.
Dr. Kallman didn't tell Dr. Endler at the time, but he referred to the fish as "Endler's Livebearer." The name stuck.
From the German aquarists it spread throughout Europe and Dr. Endler didn't hear about it until about 1980 when an English colleague asked him about the "Endler's Livebearer". From Europe it spread to America, Japan and elsewhere.
Dr. Endler says that the "Endler's Livebearer" is it's own species, not a guppy (Poecilia reticulata), because, while it could be breed with the guppy (many livebearers will interbreed) but would only produce F1 hybrids. This separate speciation is appropriate. However, they will indeed breed with guppies and produce hybrids so they should be kept separate unless this is desired. In Europe there are a number of mixed lines of fish.
Country: Venezuela. State: Sucre. State Capital: Cumana. This was the first city founded on the American Continent. The area is desert and the climate is hot and dry. Additionally, with Endler's comments we understand that a little salt added to the water will be beneficial to the fish. Cumana is coastal and, like San Diego, is surrounded by mountains which capture the rain. Unlike San Diego, the city is on the leeward side of those mountains. Both San Diego receives approximately 10 inches of rain in a normal year, squeezed from the clouds before going over the mountains, Cumana gets slightly less as the tropical rain forests on the leeward side of the mountains get the majority of the rain. (We live in San Diego.) The fish seem to like some salt added to the water (so do the Java ferns). San Diego has hard water already. I have added other minerals to the water also to help fertilize the plants and provide improved nutrition to the fish through the algae and nekton, which can usually absorb minerals directly from the water, unlike the fish.
Description
The overall shape of the male fish is very much like the wild guppy males. The position of the tails and gonopodium are similar though the shape of the dorsal fins are significantly different and there are no fancy tails shapes as there are in guppies, though swords are know to appear in various populations from time to time. These have been reported in various populations with known heritage back to Endler's original group as well as recent wild caught populations. In my population they pop up infrequently for one generation with small or long sword extensions that last only one generation. The fish is slightly smaller than the guppy and the females are slightly smaller than the guppy female. Additionally, the females are a different color than guppy females, being a greenish gold opaque color as opposed to the silverish opaque color of guppies. The color of the females changes according to the conditions they are kept in, but this is common with tropical fish.
It would seem that virility has much to do with the color intensity of the fish. The more aggressive males are more brightly colored and the less dominant males are correspondingly less colorful. This is noted by other Endler keepers and is the usual case in many tropical fish. This is likely due to hormones in alpha males.
The fish has a variety of color patches that change according to the conditions around him, as far as the intensity of the colors. The most notable color (since it is the brightest and therefore strikes our eye first) is the color orange, which is on several areas of the males. The fish also seems to be divided into front and back with the dorsal fin being the dividing line. That is, for several of the color fields.
Finage (best seen in the first photo)
One unique aspect of this fish is that Endler described wild fish as having a variation in which the pectoral fins were black (about 10% of the wild population according to Endler). We have been unable to find any in the populations we have observed. The color of the pectoral fin is clear and quite hard to see most of the time.
The uniqueness of the finage is primarily found is two fins, the dorsal fin and the caudal fin.
Without the benefit of microscopic examination, the dorsal fin seems to be made up of seven to eight radiating spines, (perfect in the Actinopterygii and Acanthopterygii forms) some of which bifurcate (split) toward the end. They are typically black but so fine on this small fish that they are very hard to see. The overall shape is fan shaped with a blunt bottom, however, it is the coloration that makes each breed potentially unique.
Professor Endler visited my page when I have only one phenotype. He commented that the wild population had more variation in the color fields and colors. (Reflected in his e-mail to Richard Sexton as "polymorphic variable.") It seems that the domestic varieties have isolated phenotypes (became homozygous) and therefore breed true as long as the lines are not mixed. A homozygote organism is one which carries identical pairs of genes (or alleles) for a specific trait. If both of the two gametes (sex cells) that fuse during fertilization carry the same form of the gene for a specific trait, the organism is said to be homozygous for that trait. In a heterozygous organism, or heterozygote, the genes for a specific trait (phenotype) are different. One or the other will be displayed in the phenotype. One or the other will be passed to each of its offspring. Since this is true from the side of each parent, the chance of a specific trait being passed from one of the parents to one of the offspring is 1/4, or 25% or just .25 out of a possible 1. Now, if two homozygous fish, each having different color alleles breed, the chance of a specific color trait is 2x1/4 or 1/2, 50% or .5. The resulting fish however will have both color alleles, one from each parent and, therefore is heterozygous. In the wild, Endler's Livebearers are heterozygous, or heterozygote.
Homozygous fish can be developed after numerous generations of inbreeding which results in one phenotype. This is the important thing to remember. This is desirable if a certain characteristic is highly desired by the fish keeper, such as with the various varieties of guppies. However, I wanted to keep a fish that was as close to the wild type as possible, so I began a program that specifically focused on mixing the phenotypes to achieve a mixed gene pool that was, again, heterozygous.
Here is my reasoning:
1) Endler said the wild fish he saw in 1975 had large color and pattern variations (they are heterozygous).
2) Dominic Isla collected the wild fish and commented about the variety of colors and color patterns in the wild (confirming they are heterozygous in the wild).
3) Armando Pou collected them from the wild in 1997 and 1998 and commented on the wide variety of color and color patterns (confirming they are heterozygous in the wild).
4) Endler gave these fish to Donn Eric Rosen.
5) Donn Eric Rosen gave an unknown amount to Klaus Kallman of the New York Aquarium.
6) Klaus Kallman gave them to numerous people including aquists who started to trade them.
7) When Professor Endler saw those collected by aquists he commented in the mid 1980's (a decade later) that it was "a disappointment to see how much of the original color pattern variation has been lost through inbreeding and founder events." So, we know that a decade after Endler collected them, they had become heterozygous.
8) therefore hetrozygousity is the natural condition of these fish, homozygousity is not its natural condition.
How did this happen? It is easy if we tell a story about these events. In 1975 Endler collects heterozygous fish from the wild. He sends them to Rosen. Rosen sends some to Europe, and to Kallman, lets say in 1976. Kallman receives five to ten fish that are still heterozygous. He breeds them for nine years having a limited phenotype, they become inbreed and homozygous (with both available alleles transmitting the same phenotype information.) Kallman now has one phenotype and distributes them to the aquist community. The story is complete and a reasonable explanation of events.
Now we have two ideas on what should be called "Endler's livebearer." The first ideas is that they are only that narrow group distributed by Kallman a decade after Endler collected them. These are homozygous. The other idea is to mix phenotypes from trusted sources and after observation to reduce the risk of introducing a guppy hybrid.
Is there some risk to this? Yes. But it is equally unknown that Endler himself did not collect fish from the wild that guppies had already mixed with due to tropical storms or other unknown factors. If this was the case, then those currently distributed as "pure" Endler's are actually a guppy mix also, but this reduces us back to naming the fish for the particular person named in honor of the specific fish he collected (not those in the wild) regardless of what it is genetically as opposed to recognizing the fish as something different and, perhaps ignorantly, think that the fish currently in the original location are also "Endler's Livebearer."
2/4/02: In the few years since the other text on this page was written, Armando’s fish has transformed my tanks into a daily collage of color with variability I had hitherto not dreamed of. The wild caught brought with them enough variability that I regularly get short sword tails, either on the bottom or the top, I have lyre tails, one with a tear drop shape, elongated tails, and tails with almost 100% color coverage. There is also a fully colored one with a short tail. The variability keeps going. Some have almost no blues or green at all, others have 50% black coverage. It is really quite a fish.
Geology of Cumana
The condition of the lake that Endler extracted the livebearer from is of concern to us for several reasons. For those interested in the fish itself, it is helpful to understand degrees of hardness to use in keeping the fish and understanding why this livebearer outnumbered the guppies in the lake. To those of us interested in the wild breed in nature, it is important to understand why the preservation of the gene pool is important because of the potential for the fish to be extinct in the wild.
Geological Considerations
The lake the fish was found in was a ground water fed lake next to the city dump. The lake is about 100 yards from the ocean. The dump percolates nutrients and contaminants into the ground, and thus into the groundwater which feeds the lake. Salt also migrates several miles inland even in the wettest of environments such as Hawaii where brackish wells can be dug two miles from the ocean. (However, the type of lava Hawaii is made of is highly porous.)
Why does this happen?
Geologists classify soil types by the ability of the soil to percolate water and the amount of organic materials found in them. This is reduced to particle size since the particle size determines the permeability. Sand and gravel percolate quickly into (or from) the ground water. If the soil is finely textured, it passes less water, it is more clay like, and less permeable to water. Generally, the more subsurface soils water travels through to reach a given location, the greater the attenuation of contaminants and nutrients and, often, the greater saturation of minerals.
Some water percolates downward, accumulating in the so-called zone of saturation to form the groundwater reservoir, the upper surface of which is the water table. Under natural conditions, the water table rises in response to inflowing water and then declines as water drains into natural outlets such as wells and springs.
Precipitation absorbs oxygen, carbon dioxide, and other gases, as well as traces of organic and inorganic material from the atmosphere. Because water reacts with minerals in the soil and rocks, surface and groundwater contains many different dissolved substances that are specific to the route of the water.
This applies in two ways to this lake. First is the fact that the water travels a great distance to get to the lake, saturating it with minerals. Second, it travels very little distance from the dump where it picks up nutrients and possible contaminants before percolating upwards or sideways to the lake. Because of these factors, the lake is eutrophic, or "well fed" as well as holding the possibility of passing contaminants relatively quickly into the lake.
Cumana experiences low rainfall, about 10 inches each year. Living in such an area myself, you understand that there are few organic molecules left in the soil to attenuate inorganic contaminants or remove nitrogen from the water since the natural purification capacity of the soil is low and seepage is high and constant. This may be increased by macropores caused by earthworm channels which often occur in dumps because of the amount of organic materials in the dump. This cuts both ways, the organic material attenuates the damage by nutrients and chemical contaminants, but increases permeability.
Since this is a small ground fed lake, and the dump is next to it, we must conclude that the vertical distance from the surface of the dump to the ground water is minimal. (Reportedly, at times zero.) Thus, much of the nutrients and contaminants reach the lake.
Since this is close to the ocean and low lying, salt from the ocean can also work its way into the ground waters and into the lake. Endler noted that the water was hard and brackish. This is different from the brackish tidal marsh environment since it is not euryhaline, that is, the tidal range influences the salinity, at high tide, these are mostly salt water. These euryhaline marshes tend to range twice daily from a low of .5% saline (almost fresh water) to a high of 3%, or completely salt water.
This lake, being slightly inland from that environment receives salt only from the underground system which varies slightly on an annual basis, not on a daily basis. The two influences being the underground salt water entering the water table from downstream and the upstream fresh water flow. While the former varies daily, the latter varies from wet to dry season. Northern Venezuela has a distinct dry season.
It is interesting to note, however, that the lake is not riverine, or related to any river, but more of a palustrine, or marsh environment, but more brackish because of its close proximity to the ocean.
Classification of the Lake
Palustrine and Lacustrine Environments
The word "palustrine" comes from the Latin word "palus" or marsh. Wetlands categorized thusly include inland marshes and swamps as well as bogs, fens, tundra and flood plains. Palustrine systems include any inland wetland which lacks flowing water and contains ocean derived salts in concentrations of less than .05%, so this excludes this lake, however, the other categories apply.
The lacustrine wetland category does not quite apply for the same reason, though I would argue that the lacustrine category describes such an environment, again, save for the salinity.
Freshwater Marshes and Fens
Fens are a type of bog. These bogs are watered by alkaline, mineral rich water. Acidic growths of mosses are missing from fens since the water is so high in alkalizing agents. This is not conducive to the growth of acid loving mosses. Sphagnum moss which is usually found in these acid bogs is absent.
A fen differs hydrologically from a bog, which is usually a terminal point for the water entering it, and this water usually comes from nutrient and mineral poor ground water or rain run off.
Fens, on the other hand, usually receive water from a hillside run off or other nutrient rich run off such as mineral rich underground water such as this lake receives. Usually there is an exit for the water as well such as efficient percolation which changes the water periodically or from overflow which has the same result.
We should, therefore classify this as a brackish eutrophic persistent fen.
Eutrophication
In an underdeveloped third world environment such as the area surrounding Cumana, typically the city dump will have somewhat less chemical contaminant than in emergent economies that are utilizing chemical compounds to treat agricultural products. Also, the dump receives large amounts of processed organic materials such as discarded paper and wood products. Discarded animals are usually dumped into the dump as well. Animals that were accidentally killed, killed by disease, and parts of animals that are discarded as well as large amounts of animal waste. Additionally, large amounts of plant materials are dumped. There from discarded processed foods and unprocessed plant products. Concentrations of these and other nutrients are added to the rain water that percolates into the ground by the lake. This is the eutrophication of the lake.
Wetlands are typically able to withstand substantial increases in the concentration of available nutrients. The change of water helps to eliminate much of this nutrient source, bacterial and algae growth increase as well as copepods and other small organisms that can absorb nutrients directly through the external tissues. However, in this lake, unicellular algae have become the dominant responder to the increase in nutrients. At present we have been unable to contact anyone with an assessment of the photosynthetic environment to see if these are predominantly blue-green algae (photosynthetic bacteria) or if they are true algae. If they are blue-green algae, this would indicate increased nitrogen contents and this would put at risk the entire lake population of fish since one alga "bloom" would result in depletion of oxygen in the lake killing off all the fish and any other organism that cannot use surface gases as a source of oxygen. Why is this true? While blue-green algae produce oxygen, when they "bloom" they do so en masse and then die. The putrefaction of the biomass increased the biochemical oxygen demand to the point that other organisms cannot survive. The lake dies.
A dead lake invites mosquitoes to breed and soon diseases spread to the people in the area.
Biochemical Oxygen Demand (BOD) refers to the amount of oxygen that would be consumed if all the organics in one liter of water were oxidized by bacteria and protozoa and is a measure of the amount of living organisms in the lake. In the case of an alga bloom, the BOD increases so rapidly that the system is not capable of exchanging the gasses in order to keep up. When the BOD is not met, organisms begin to die. The decaying plant and animal life again increases the BOD since oxygen is required for the decay of the organisms, and further depletes the water dissolved oxygen killing more organisms.
On the other hand. if the primary growth in the lake is spawned by low nitrogen, and high potassium and/or phosphorus content, then the unicellular algae will grow en mass and this cycle does not occur. Instead, a more life friendly cycle begins where the algae increase the oxygen content of the water at night, depleting carbon dioxide from the water, and raising the pH (CO2 is stored as carboxylic acid which lowers pH). During the night, the CO2 level increases while the BOD of the fish also decreases, thus leaving the fish unscathed but slowing the growth of bacteria.
Thus, the continued existence of Endler's Livebearer in the wild may be a matter of the nitrogen content of the lake as well as the mix of bacteria. Photosynthetic bacteria (blue-green algae) combined with high nitrogen levels could cause the fish to become extinct in its native waters.
Go to site for photo's maps, endlers collectors and bibliography.
Prof. John A. Endler collected Poecilia sp. now, "Endler's Livebearer" in 1975 in Laguna de Patos, Cumana, in northeastern Venezuela (see map above). He found these fish in warm (81 degrees F) , hard water which is very green with unicellular algae which, along with other plankton such as diatoms, nekton, and filamentous algae make up part of their food. See Armando's page for more information on the area and water.
Dr. Endler gave a stock of Poecilia sp. "Endler's" to Dr. Donn Eric Rosen, the then Curator of Ichthyology at the American Museum of Natural History, who was going to name it (but died a few years later). Dr. Rosen gave some of the stock to a mutual friend of Dr. Endler, Dr. Klaus Kallman, then of the New York Aquarium, and a famous fish geneticist. Dr. Kallman introduced it to the German aquarium community. Many of the European group are hybrids of Endler's mixed with guppies of various breeds. Dr. Endler noted the extreme variety of colors in the wild were eliminated by the time they reached the aquist's community. He also commented that my original pictures reflected this inbred characteristic of many kept groups of fish, homozygousity, that is, they breed true to one color pattern, or phenotype.
Dr. Kallman didn't tell Dr. Endler at the time, but he referred to the fish as "Endler's Livebearer." The name stuck.
From the German aquarists it spread throughout Europe and Dr. Endler didn't hear about it until about 1980 when an English colleague asked him about the "Endler's Livebearer". From Europe it spread to America, Japan and elsewhere.
Dr. Endler says that the "Endler's Livebearer" is it's own species, not a guppy (Poecilia reticulata), because, while it could be breed with the guppy (many livebearers will interbreed) but would only produce F1 hybrids. This separate speciation is appropriate. However, they will indeed breed with guppies and produce hybrids so they should be kept separate unless this is desired. In Europe there are a number of mixed lines of fish.
Country: Venezuela. State: Sucre. State Capital: Cumana. This was the first city founded on the American Continent. The area is desert and the climate is hot and dry. Additionally, with Endler's comments we understand that a little salt added to the water will be beneficial to the fish. Cumana is coastal and, like San Diego, is surrounded by mountains which capture the rain. Unlike San Diego, the city is on the leeward side of those mountains. Both San Diego receives approximately 10 inches of rain in a normal year, squeezed from the clouds before going over the mountains, Cumana gets slightly less as the tropical rain forests on the leeward side of the mountains get the majority of the rain. (We live in San Diego.) The fish seem to like some salt added to the water (so do the Java ferns). San Diego has hard water already. I have added other minerals to the water also to help fertilize the plants and provide improved nutrition to the fish through the algae and nekton, which can usually absorb minerals directly from the water, unlike the fish.
Description
The overall shape of the male fish is very much like the wild guppy males. The position of the tails and gonopodium are similar though the shape of the dorsal fins are significantly different and there are no fancy tails shapes as there are in guppies, though swords are know to appear in various populations from time to time. These have been reported in various populations with known heritage back to Endler's original group as well as recent wild caught populations. In my population they pop up infrequently for one generation with small or long sword extensions that last only one generation. The fish is slightly smaller than the guppy and the females are slightly smaller than the guppy female. Additionally, the females are a different color than guppy females, being a greenish gold opaque color as opposed to the silverish opaque color of guppies. The color of the females changes according to the conditions they are kept in, but this is common with tropical fish.
It would seem that virility has much to do with the color intensity of the fish. The more aggressive males are more brightly colored and the less dominant males are correspondingly less colorful. This is noted by other Endler keepers and is the usual case in many tropical fish. This is likely due to hormones in alpha males.
The fish has a variety of color patches that change according to the conditions around him, as far as the intensity of the colors. The most notable color (since it is the brightest and therefore strikes our eye first) is the color orange, which is on several areas of the males. The fish also seems to be divided into front and back with the dorsal fin being the dividing line. That is, for several of the color fields.
Finage (best seen in the first photo)
One unique aspect of this fish is that Endler described wild fish as having a variation in which the pectoral fins were black (about 10% of the wild population according to Endler). We have been unable to find any in the populations we have observed. The color of the pectoral fin is clear and quite hard to see most of the time.
The uniqueness of the finage is primarily found is two fins, the dorsal fin and the caudal fin.
Without the benefit of microscopic examination, the dorsal fin seems to be made up of seven to eight radiating spines, (perfect in the Actinopterygii and Acanthopterygii forms) some of which bifurcate (split) toward the end. They are typically black but so fine on this small fish that they are very hard to see. The overall shape is fan shaped with a blunt bottom, however, it is the coloration that makes each breed potentially unique.
Professor Endler visited my page when I have only one phenotype. He commented that the wild population had more variation in the color fields and colors. (Reflected in his e-mail to Richard Sexton as "polymorphic variable.") It seems that the domestic varieties have isolated phenotypes (became homozygous) and therefore breed true as long as the lines are not mixed. A homozygote organism is one which carries identical pairs of genes (or alleles) for a specific trait. If both of the two gametes (sex cells) that fuse during fertilization carry the same form of the gene for a specific trait, the organism is said to be homozygous for that trait. In a heterozygous organism, or heterozygote, the genes for a specific trait (phenotype) are different. One or the other will be displayed in the phenotype. One or the other will be passed to each of its offspring. Since this is true from the side of each parent, the chance of a specific trait being passed from one of the parents to one of the offspring is 1/4, or 25% or just .25 out of a possible 1. Now, if two homozygous fish, each having different color alleles breed, the chance of a specific color trait is 2x1/4 or 1/2, 50% or .5. The resulting fish however will have both color alleles, one from each parent and, therefore is heterozygous. In the wild, Endler's Livebearers are heterozygous, or heterozygote.
Homozygous fish can be developed after numerous generations of inbreeding which results in one phenotype. This is the important thing to remember. This is desirable if a certain characteristic is highly desired by the fish keeper, such as with the various varieties of guppies. However, I wanted to keep a fish that was as close to the wild type as possible, so I began a program that specifically focused on mixing the phenotypes to achieve a mixed gene pool that was, again, heterozygous.
Here is my reasoning:
1) Endler said the wild fish he saw in 1975 had large color and pattern variations (they are heterozygous).
2) Dominic Isla collected the wild fish and commented about the variety of colors and color patterns in the wild (confirming they are heterozygous in the wild).
3) Armando Pou collected them from the wild in 1997 and 1998 and commented on the wide variety of color and color patterns (confirming they are heterozygous in the wild).
4) Endler gave these fish to Donn Eric Rosen.
5) Donn Eric Rosen gave an unknown amount to Klaus Kallman of the New York Aquarium.
6) Klaus Kallman gave them to numerous people including aquists who started to trade them.
7) When Professor Endler saw those collected by aquists he commented in the mid 1980's (a decade later) that it was "a disappointment to see how much of the original color pattern variation has been lost through inbreeding and founder events." So, we know that a decade after Endler collected them, they had become heterozygous.
8) therefore hetrozygousity is the natural condition of these fish, homozygousity is not its natural condition.
How did this happen? It is easy if we tell a story about these events. In 1975 Endler collects heterozygous fish from the wild. He sends them to Rosen. Rosen sends some to Europe, and to Kallman, lets say in 1976. Kallman receives five to ten fish that are still heterozygous. He breeds them for nine years having a limited phenotype, they become inbreed and homozygous (with both available alleles transmitting the same phenotype information.) Kallman now has one phenotype and distributes them to the aquist community. The story is complete and a reasonable explanation of events.
Now we have two ideas on what should be called "Endler's livebearer." The first ideas is that they are only that narrow group distributed by Kallman a decade after Endler collected them. These are homozygous. The other idea is to mix phenotypes from trusted sources and after observation to reduce the risk of introducing a guppy hybrid.
Is there some risk to this? Yes. But it is equally unknown that Endler himself did not collect fish from the wild that guppies had already mixed with due to tropical storms or other unknown factors. If this was the case, then those currently distributed as "pure" Endler's are actually a guppy mix also, but this reduces us back to naming the fish for the particular person named in honor of the specific fish he collected (not those in the wild) regardless of what it is genetically as opposed to recognizing the fish as something different and, perhaps ignorantly, think that the fish currently in the original location are also "Endler's Livebearer."
2/4/02: In the few years since the other text on this page was written, Armando’s fish has transformed my tanks into a daily collage of color with variability I had hitherto not dreamed of. The wild caught brought with them enough variability that I regularly get short sword tails, either on the bottom or the top, I have lyre tails, one with a tear drop shape, elongated tails, and tails with almost 100% color coverage. There is also a fully colored one with a short tail. The variability keeps going. Some have almost no blues or green at all, others have 50% black coverage. It is really quite a fish.
Geology of Cumana
The condition of the lake that Endler extracted the livebearer from is of concern to us for several reasons. For those interested in the fish itself, it is helpful to understand degrees of hardness to use in keeping the fish and understanding why this livebearer outnumbered the guppies in the lake. To those of us interested in the wild breed in nature, it is important to understand why the preservation of the gene pool is important because of the potential for the fish to be extinct in the wild.
Geological Considerations
The lake the fish was found in was a ground water fed lake next to the city dump. The lake is about 100 yards from the ocean. The dump percolates nutrients and contaminants into the ground, and thus into the groundwater which feeds the lake. Salt also migrates several miles inland even in the wettest of environments such as Hawaii where brackish wells can be dug two miles from the ocean. (However, the type of lava Hawaii is made of is highly porous.)
Why does this happen?
Geologists classify soil types by the ability of the soil to percolate water and the amount of organic materials found in them. This is reduced to particle size since the particle size determines the permeability. Sand and gravel percolate quickly into (or from) the ground water. If the soil is finely textured, it passes less water, it is more clay like, and less permeable to water. Generally, the more subsurface soils water travels through to reach a given location, the greater the attenuation of contaminants and nutrients and, often, the greater saturation of minerals.
Some water percolates downward, accumulating in the so-called zone of saturation to form the groundwater reservoir, the upper surface of which is the water table. Under natural conditions, the water table rises in response to inflowing water and then declines as water drains into natural outlets such as wells and springs.
Precipitation absorbs oxygen, carbon dioxide, and other gases, as well as traces of organic and inorganic material from the atmosphere. Because water reacts with minerals in the soil and rocks, surface and groundwater contains many different dissolved substances that are specific to the route of the water.
This applies in two ways to this lake. First is the fact that the water travels a great distance to get to the lake, saturating it with minerals. Second, it travels very little distance from the dump where it picks up nutrients and possible contaminants before percolating upwards or sideways to the lake. Because of these factors, the lake is eutrophic, or "well fed" as well as holding the possibility of passing contaminants relatively quickly into the lake.
Cumana experiences low rainfall, about 10 inches each year. Living in such an area myself, you understand that there are few organic molecules left in the soil to attenuate inorganic contaminants or remove nitrogen from the water since the natural purification capacity of the soil is low and seepage is high and constant. This may be increased by macropores caused by earthworm channels which often occur in dumps because of the amount of organic materials in the dump. This cuts both ways, the organic material attenuates the damage by nutrients and chemical contaminants, but increases permeability.
Since this is a small ground fed lake, and the dump is next to it, we must conclude that the vertical distance from the surface of the dump to the ground water is minimal. (Reportedly, at times zero.) Thus, much of the nutrients and contaminants reach the lake.
Since this is close to the ocean and low lying, salt from the ocean can also work its way into the ground waters and into the lake. Endler noted that the water was hard and brackish. This is different from the brackish tidal marsh environment since it is not euryhaline, that is, the tidal range influences the salinity, at high tide, these are mostly salt water. These euryhaline marshes tend to range twice daily from a low of .5% saline (almost fresh water) to a high of 3%, or completely salt water.
This lake, being slightly inland from that environment receives salt only from the underground system which varies slightly on an annual basis, not on a daily basis. The two influences being the underground salt water entering the water table from downstream and the upstream fresh water flow. While the former varies daily, the latter varies from wet to dry season. Northern Venezuela has a distinct dry season.
It is interesting to note, however, that the lake is not riverine, or related to any river, but more of a palustrine, or marsh environment, but more brackish because of its close proximity to the ocean.
Classification of the Lake
Palustrine and Lacustrine Environments
The word "palustrine" comes from the Latin word "palus" or marsh. Wetlands categorized thusly include inland marshes and swamps as well as bogs, fens, tundra and flood plains. Palustrine systems include any inland wetland which lacks flowing water and contains ocean derived salts in concentrations of less than .05%, so this excludes this lake, however, the other categories apply.
The lacustrine wetland category does not quite apply for the same reason, though I would argue that the lacustrine category describes such an environment, again, save for the salinity.
Freshwater Marshes and Fens
Fens are a type of bog. These bogs are watered by alkaline, mineral rich water. Acidic growths of mosses are missing from fens since the water is so high in alkalizing agents. This is not conducive to the growth of acid loving mosses. Sphagnum moss which is usually found in these acid bogs is absent.
A fen differs hydrologically from a bog, which is usually a terminal point for the water entering it, and this water usually comes from nutrient and mineral poor ground water or rain run off.
Fens, on the other hand, usually receive water from a hillside run off or other nutrient rich run off such as mineral rich underground water such as this lake receives. Usually there is an exit for the water as well such as efficient percolation which changes the water periodically or from overflow which has the same result.
We should, therefore classify this as a brackish eutrophic persistent fen.
Eutrophication
In an underdeveloped third world environment such as the area surrounding Cumana, typically the city dump will have somewhat less chemical contaminant than in emergent economies that are utilizing chemical compounds to treat agricultural products. Also, the dump receives large amounts of processed organic materials such as discarded paper and wood products. Discarded animals are usually dumped into the dump as well. Animals that were accidentally killed, killed by disease, and parts of animals that are discarded as well as large amounts of animal waste. Additionally, large amounts of plant materials are dumped. There from discarded processed foods and unprocessed plant products. Concentrations of these and other nutrients are added to the rain water that percolates into the ground by the lake. This is the eutrophication of the lake.
Wetlands are typically able to withstand substantial increases in the concentration of available nutrients. The change of water helps to eliminate much of this nutrient source, bacterial and algae growth increase as well as copepods and other small organisms that can absorb nutrients directly through the external tissues. However, in this lake, unicellular algae have become the dominant responder to the increase in nutrients. At present we have been unable to contact anyone with an assessment of the photosynthetic environment to see if these are predominantly blue-green algae (photosynthetic bacteria) or if they are true algae. If they are blue-green algae, this would indicate increased nitrogen contents and this would put at risk the entire lake population of fish since one alga "bloom" would result in depletion of oxygen in the lake killing off all the fish and any other organism that cannot use surface gases as a source of oxygen. Why is this true? While blue-green algae produce oxygen, when they "bloom" they do so en masse and then die. The putrefaction of the biomass increased the biochemical oxygen demand to the point that other organisms cannot survive. The lake dies.
A dead lake invites mosquitoes to breed and soon diseases spread to the people in the area.
Biochemical Oxygen Demand (BOD) refers to the amount of oxygen that would be consumed if all the organics in one liter of water were oxidized by bacteria and protozoa and is a measure of the amount of living organisms in the lake. In the case of an alga bloom, the BOD increases so rapidly that the system is not capable of exchanging the gasses in order to keep up. When the BOD is not met, organisms begin to die. The decaying plant and animal life again increases the BOD since oxygen is required for the decay of the organisms, and further depletes the water dissolved oxygen killing more organisms.
On the other hand. if the primary growth in the lake is spawned by low nitrogen, and high potassium and/or phosphorus content, then the unicellular algae will grow en mass and this cycle does not occur. Instead, a more life friendly cycle begins where the algae increase the oxygen content of the water at night, depleting carbon dioxide from the water, and raising the pH (CO2 is stored as carboxylic acid which lowers pH). During the night, the CO2 level increases while the BOD of the fish also decreases, thus leaving the fish unscathed but slowing the growth of bacteria.
Thus, the continued existence of Endler's Livebearer in the wild may be a matter of the nitrogen content of the lake as well as the mix of bacteria. Photosynthetic bacteria (blue-green algae) combined with high nitrogen levels could cause the fish to become extinct in its native waters.
