fish

Nature Nugget – Troglomorphic Fishes

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There are 81 known species of subterranean fishes in the world. Some travel back and forth between the darkness underground and the light above, but many spend their entire lives in the pitch-blackness of subterranean rivers, streams, lakes, and springs. These are the troglomorphic species, and they have adapted to this harsh environment by the loss of their eyes and the development of numerous large sensory papillae on various parts of their bodies. These sensory papillae are sensitive to vibrations and touch and compensate for their lack of sight, permitting them to carry on life functions, such as finding food and avoiding predators, in total darkness. They also lack pigment in the skin and look pinkish because of blood vessels showing through their translucent skin.

There are two groups of troglomorphic fishes in the United States, the cavefishes of the family Amblyopsidae and the blindcats of the family Ictaluridae. The cavefishes are less than five inches in length and are found in the eastern United States. They have a large branchial cavity, which allows them to carry and incubate their eggs in the gill chamber. Because the cave systems they live in are energy poor, cavefishes eat infrequently and conserve energy by having slow metabolisms and remaining motionless most of the time. They are slow-growing and long-lived. Cavefishes feed on copepods, isopods, amphipods, crayfish, small salamanders, and even their own young.

The Alabama Cavefish is found only in Key Cave in Lauderdale County, Alabama. Its total known population is numbered at less than 100, making it one of the most endangered fishes in the world. In contrast, the Southern Cavefish is uncommonly found in caves over a fairly large area involving seven states. The two remaining troglomorphic species in this family are the Ozark Cavefish of the Springfield Plateau and the Northern Cavefish of south-central Indiana and central Kentucky. Both are considered rare, with the Ozark Cavefish being classified as a threatened species.

The blindcats consist of four species, of which two occur in the United States. These are known from five artesian wells penetrating the San Antonio Pool of the Edward’s Aquifer in and near San Antonio, Texas. They have been found to occur together in three of these wells. Both species are abundant in their habitat and occur in these subterranean waters at depths of 900–2,000 feet. The Toothless Blindcat, at four inches, feeds on fungal growths and detritus, while the Widemouth Blindcat, at five inches, is an opportunistic predator, feeding on shrimp, amphipods, and isopods.

Just as these subterranean fishes have lost their eyesight from living in total darkness, so the Christian is in danger of losing his spiritual eyesight by living in the darkness of sin. “In following the path of Satan’s choosing, we are encompassed by the shadows of evil, and every step leads into deeper darkness and increases the blindness of the heart. The same law obtains in the spiritual as in the natural world. He who abides in darkness will at last lose the power of vision. He is shut in by a deeper than midnight blackness; and to him the brightest noontide can bring no light. He ‘walketh in darkness, and knoweth not whither he goeth, because that darkness hath blinded his eyes.’ 1 John 2:11.

“Through persistently cherishing evil, willfully disregarding the pleadings of divine love, the sinner loses the love for good, the desire for God, the very capacity to receive the light of heaven. The invitation of mercy is still full of love, the light is shining as brightly as when it first dawned upon his soul; but the voice falls on deaf ears, the light on blinded eyes.” Thoughts From the Mount of Blessing, 92.

David Arbour writes from his home in DeQueen, Arkansas. He may be contacted by e-mail at incadove@ipa.net.

Nature Nugget – Fish Cleaning Stations

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Fishes have thousands of scales for parasites to get under and create annoyance, but no fingers with which to scratch themselves. Cleaning stations provide that service for them. Cleaning stations are places on the coral reef where various species of fish and shrimps, known as cleaners, provide the services of parasite removal and grooming for other species. The relationship between these cleaners and their patients is a symbiotic relationship, which is beneficial to both parties involved. The cleaners benefit by feeding on the parasites and dead tissue, and the patients benefit by having these things removed from their bodies. Fish literally line up to wait their turn at these stations, and ocean-going species travel long distances to the reefs to receive this service. Species as large as sharks and Manta Rays and even sea turtles and Moray Eels visit these stations. Even the most voracious predators are careful not to harm a cleaner, allowing it to nibble everywhere and freely explore mouth and gills. The service provided at the cleaning stations is so important that the whole coral reef community would die without it.

Of the approximately fifty species of fish that are known to perform the service of cleaners, none are as well known and represented as members of the wrasse family. Cleaner wrasses or doctorfish, as they are sometimes called, are boldly marked with blue, white, black, and sometimes yellow longitudinal stripes. The cleaner wrasses advertise their services with a dance routine. The flash of their electric-blue stripe acts as a beacon to attract fish in need of cleaning. Orderly queues soon form. By rushing forward, turning sideways, and then retreating, it draws each patient into an abnormal but most accessible position. The patient then spreads its fins, opens its mouth, and lifts its gill covers. The wrasse’s tweezer-like teeth then get to work removing ectoparasites, dead skin, and tissue from old wounds. They have been known to clean up to 300 fish in a six-hour period and remove as many as 1,200 parasites a day.

Cleaner shrimp, of which there are six species, are identified with bold red bands or markings. They mate for life and work in pairs, usually at night or in crevices. Cleaner shrimp attract patients by doing a tap dance with their spindly legs. Like the cleaner wrasses, the shrimps clean the whole surface of the fish including inside the mouth and gills, picking off ectoparasites and dead tissue with their pincers. When superficial surgery is required, it is left to the cleaner shrimp, which makes small incisions in the skin with their sharp claws to remove hidden parasites. During this procedure, the patient may wince with pain, but it still remains motionless. Cleaner shrimp will even clean plaque from the teeth of scuba divers who remove their mouthpieces and open their mouths, allowing the shrimp in.

Just as the fish in the sea have to come to the cleaning stations on the coral reefs to be cleansed of their parasites, so we as sinners need to come to Christ and repent to be cleansed from the parasites of sin. “If we confess our sins, he is faithful and just to forgive us [our] sins, and to cleanse us from all unrighteousness.” 1 John 1:9. “If you are condemned, there is but one course for you to pursue: you must repent toward God because of the transgression of His law, and have faith toward our Lord Jesus Christ as the one who only can cleanse from sin.” Selected Messages, Book 1, 317.

David Arbour writes from his home in DeQueen, Arkansas. He may be contacted by e-mail at: landmarks@stepstolife.org.

Nature Nugget – Salmon Migration

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Along the Pacific Coast of North America lives a group of fishes that are famous for their long-distance travel. There are five species of Pacific salmon: Chinook, Chum, Coho, Pink, and Sockeye. Pacific salmon are anadromous, meaning they spend part of their lives in freshwater and part in saltwater. They begin their lives in the headwaters of rivers and streams where their eggs hatch and small fry emerge carrying a yoke sac attached to their bellies. The young remain in the gravel and the yoke sac feeds them until they are strong enough to swim in the current and feed on aquatic organisms.

The smaller species of salmon start migrating downstream toward the sea when they have grown to about three inches. The larger species remain in freshwater for one to two years before heading out to sea. As the current carries them downstream toward the Pacific Ocean, their bodies undergo physical and chemical changes that will enable them to survive in saltwater. Once they enter the Pacific Ocean, they disperse in all directions. Pink Salmon usually stay within 150 miles of the mouth of their home river or stream, while Chinook Salmon may travel as far as 2,500 miles from theirs.

When they reach sexual maturity, the salmon return to the exact freshwater stream of their origin to lay their eggs. They are able to do this by their unparalleled sense of smell. Each river and stream has its own, unique, chemical composition that sets it apart from all others.

The upstream journey of migrating salmon is often long and strenuous, with numerous predators and obstacles, such as waterfalls and dams to maneuver. Salmon do not feed once they enter freshwater, and their condition gradually deteriorates as they journey upstream. Pacific salmon may migrate hundreds or even thousands of miles to reach their spawning grounds, but only a small percentage make it all the way back and spawn. In the Columbia River system, the Snake River strains of salmon travel up to 900 miles from the sea to spawn in the high mountain streams of Idaho. In the Yukon River of Alaska, Chinook Salmon travel over 2,000 river miles, during a 60-day period, to spawn in the Yukon Territory of Canada. When the salmon reach the spawning grounds, they are bruised and battered from the journey and must now battle each other for nesting places and mates with which to spawn. Once a pair have formed and established a territory, the female builds a nest, called a redd, with her tail. The pair then spawns, and afterward, the female covers the eggs with loose gravel. The pair then move upstream a short distance and repeat the process. One pair of salmon may have several redds. All Pacific salmon die within a few days after spawning.

Just as the salmon must perseveringly follow the scent of their home stream to reach their spawning grounds, so the Christian must follow the light from the Word of God to reach Heaven. “Thy word [is] a lamp unto my feet, and a light unto my path.” Psalm 119:105. And like the salmon migration, only a small percentage make it. “Enter ye in at the strait gate: for wide [is] the gate, and broad [is] the way, that leadeth to destruction, and many there be which go in thereat: Because strait [is] the gate, and narrow [is] the way, which leadeth unto life, and few there be that find it.” Matthew 7:13, 14. Unlike the salmon, the Christian will not die at the end of his journey but will live for eternity! “He shall receive . . . in the world to come eternal life.” Mark 10:30.

David Arbour writes from his home in DeQueen, Arkansas. He may be contacted by e-mail at: landmarks@stepstolife.org.

Nature Nugget – The Fat Sleeper

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Sleepers are goby-type fishes that are members of the family Eleotridae, but they differ from most gobies by having widely spaced pelvic fins that are never joined or modified into a sucking disk. Sleepers are named such because most have eyes that tend to have a “glassy” look, as if the fish is unconscious, and because the behavior of many is to lie still on the bottom or in vegetation waiting to ambush prey.

Sleepers are found in habitats varying from pure freshwater to seawater (marine) and in numerous brackish habitats in-between. They can move or be moved between these varying degrees of salinity without showing any indications of stress. This ability of sleepers to live in and move between freshwater, brackish, and marine water is linked to an enzyme in the fishes’ gill epithelium called “sodium-potassium-activated ATPase,” the activity of which is triggered by immersion in salt-containing water. The enzyme promotes the discharge of sodium ions from the gills, allowing the fish to maintain osmotic balance in seawater. The enzyme activity turns off when the fish moves into freshwater.

There are several species of sleepers in the United States coastal areas, the most common one being the Fat Sleeper (Dormitator maculatus). Fat Sleepers are common in vegetated fresh, brackish, and occasionally marine habitats along the Atlantic and Gulf coasts from North Carolina to Brazil and including the Bahamas and West Indies. Their preferred habitats are freshwater ponds, fresh and brackish marshes, low salinity tide pools, and coastal mangrove swamps. Adaptation to variations in coastal habitats has made this fish very resistant to low oxygen and changing water quality. The Fat Sleeper is large—up to 12 inches—and stocky (hence its name). It is mostly benthic (bottom dwelling) where it occurs in weed beds and areas of debris where it feeds on aquatic invertebrates such as copepods, ostracods, and insects.

Fat Sleepers will only breed in freshwater. When it comes time to breed, they undergo a change in body color, and after a complex mating “dance,” they spawn and lay eggs on a flat surface such as a rock. Both parents guard the eggs until they hatch. The eggs hatch within 24 hours and the young travel to saltwater to spend the first stage of their lives.

Does the name Fat Sleeper describe many of us today who claim to be a part of God’s last day church? The first part of this name certainly describes many of us. What about the second part of this name? Are we asleep? “Many have been altogether too long in a sleepy condition.” Testimonies to Ministers and Gospel Workers, 206. “Men and women are in the last hours of probation, and yet are careless and stupid, and ministers have no power to arouse them; they are asleep themselves. Sleeping preachers preaching to a sleeping people.” Testimonies, vol. 2, 337. Fortunately, there is hope for us that are in this condition. “Yet the case of even this class is not utterly hopeless. With those who have slighted God’s mercy and abused His grace, the heart of long-suffering love yet pleads. Wherefore He saith, Awake thou that sleepest, and arise from the dead, and Christ shall give thee light.” The Great Controversy, 601, 602. “We are living in the closing scenes of this earth’s history. Prophecy is fast fulfilling. The hours of probation are fast passing. We have no time—not a moment—to lose. Let us not be found sleeping on guard. Let no one say in his heart or by his works: ‘My Lord delayeth his coming.’ [Matthew 24:48.] Let the message of Christ’s soon return sound forth in earnest words of warning.” Testimonies, vol. 8, 252.

David Arbour writes from his home in DeQueen, Arkansas. He may be contacted by e-mail at: landmarks@stepstolife.org.

Nature Nugget – Electric Fishes

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In marshes and stagnant areas of the Amazon Basin of South America lives a fish called the Electric Eel. Though not a true eel, but closely resembling one, its internal organs are found in a small area just behind the head with the remaining seven-eighths of its body being tail. Reaching lengths of six to nine feet, Electric Eels are obligate air-breathers, requiring a breath of air every few minutes.

The most unique thing about the Electric Eel is that it has the capability of emitting an electric discharge of up to 650 volts and a current of up to 1 ampere. It has been known to kill humans and to knock down a horse crossing a stream from 20 feet away. The main functions of these high intensity electric discharges are for stunning or killing its prey and for defense from predators. It also produces low intensity discharges in the 5 to 10 volt range for sensory perception (electro-location), allowing it to navigate and find its prey in muddy water and to communicate with others of its kind. The Electric Eel’s body is similar to a battery with the tail end having a positive charge and the head region a negative charge.

Another electric fish is the Electric Catfish, which is found among rocks and roots in dark, freshwater rivers and lakes of Western and Central Africa and the Nile River. Electric Catfishes are nocturnal and feed on smaller fishes, worms, crustaceans, and insects. Attaining a maximum size of around three feet in length, they can live for up to 15 years. Like the Electric Eel, they can produce an electric shock, but at only about half the volts (about 300–350 volts), which is also used for stunning prey and for defense. The Arabs and Egyptians used Electric Catfishes for medicinal purposes.

Another electric fish, the Torpedo Ray, found in the Mediterranean Sea, was also used for medicinal purposes. Discharging up to 220 volts and 120 amperes of current, the Torpedo Rays were used by Roman physicians as shock therapy to treat gout, mental illness, and headaches. The Greeks used the Electric Ray, a smaller, less potent relative of the Torpedo Ray, to treat headaches. They did this by wrapping the ray around the head of the patient.

The electric organs of electric fishes are composed of multiple stacks of coin-shaped cells, derived from neuromuscular tissue, called electroplaques. Nervous stimulation of each cell produces a small electrical flow from one face of the coin-shaped cell to the other. Simultaneous stimulation of many electro-plaques arranged in a column and all oriented with their innervated side up will produce a strong net current. These electroplaque columns are like batteries aligned in series; the more in a line, the greater the voltage produced. Also, the more stacks aligned in parallel, the greater the amperage.

All these fishes are capable of producing power in the form of electricity for defense against their enemies; likewise the Christian is capable of having power against his enemy, Satan, through the shed blood of Jesus Christ. “Reach up and grasp His hand, that the touch may electrify you and charge you with the sweet properties of His own matchless character. You may open your hearts to His love, and let His power transform you and His grace be your strength.” Testimonies, vol. 4, 63.

David Arbour writes from his home in DeQueen, Arkansas. He may be contacted by e-mail at: landmarks@stepstolife.org.

Nature Nugget: The Mangrove Rivulus

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The Mangrove Rivulus is a small killifish (a family of numerous small, oviparous fishes much used as bait and in mosquito control) found in the tropical and subtropical portions of the western Atlantic/Caribbean Basin from central Florida south through the West Indies and Caribbean to Brazil. It is strictly a coastal species occurring in salt and brackish habitats and rarely in freshwater. Its range closely parallels that of red mangrove forests, which is its preferred habitat, where it occupies marginal and ephemeral (temporarily flooded) bodies of water such as stagnant, seasonal ponds, sloughs, and mosquito ditches. It also occurs in similar habitats away from the mangroves in elevated marsh habitats above the intertidal zone, especially in microhabitats such as the burrows of the great land crab. The crab burrows provide refuge for the Mangrove Rivulus during the dry season when seasonal pools of water dry up. Up to twenty-six small individuals have been found in a single crab burrow, but one or two per burrow is the usual number found.

Tolerating the extremes of temperature and salinity found in these habitats, the Mangrove Rivulus is one of the few fishes that can survive here. It can tolerate salinities from 0–68 parts per thousand and temperatures ranging from 7–38 degrees Celsius. It also can tolerate low oxygen levels and high sulfide levels that are produced in these habitats from decaying leaf litter, which would kill most fish species. The Mangrove Rivulus is also amphibious and frequently travels across land during rains to reach pools of water or crab burrows. It will also leave drying up bodies of water and waters that are too low in oxygen or too high in sulfides and bury itself in moist debris. It is capable of surviving out of water in this moist situation for up to 60 days. It is able to do this because of special epidermal capillaries that allow it to absorb oxygen and expel carbon dioxide through its skin.

Reproduction in the Mangrove Rivulus is very unusual. It is the only known vertebrate “hermaphrodite” that is self-fertilizing. Hermaphrodite means that it has both male and female reproductive parts. Both eggs and sperm are produced in reproductive organs called “ovotestes.” Each hermaphroditic individual fertilizes its eggs before laying them. The young are “clones,” meaning that they are genetically identical to the parent. This hermaphroditic mode of reproduction may be an adaptation to isolation in the crab burrows and other microhabitats these fish invade. Not all Mangrove Rivuli are hermaphrodites. There are two types of males that occur: primary males and secondary males. Primary males are hatched from fertilized eggs, but secondary males were once hermaphrodites that underwent a change and became males due to certain environmental conditions. True females have not been found in the wild but occur in captive-raised populations. Hermaphroditic individuals are identified by the presence of an eyespot at the upper base of the caudal fin and by a white band in the outer part of the anal fin. There is recent evidence that shows that the young adult fish are able to reproduce by normal sexual reproduction at first, but as they age, they become hermaphroditic. Eggs, at laying, vary in development from recently fertilized to ones containing already developing embryos. Mangrove Rivuli eggs are capable of surviving droughts in damp substrates or debris in a state of “embryonic diapause” where the embryo is in suspended animation. Eggs in this state are viable for several months and hatch soon after inundation by water.

God has implanted in the genes of His creatures enough genetic variability to allow for adaptation for survival under the most extreme circumstances. “It was the Maker of all things who ordained the wonderful adaptation of means to end, of supply to need. . . .

“He who studies most deeply into the mysteries of nature will realize most fully his own ignorance and weakness.” Education, 133.

David Arbour writes from his home in DeQueen, Arkansas. He may be contacted by e-mail at: landmarks@stepstolife.org.