Lesson III: Animal Adaptations and Distributions II Keywords: ichthyologist, vertebrate, metabolic rate, olfactory organs, crustaceans, antennae, lateral line, Eurypharyngidae, neuromast, demersal, diversity, epifauna, infauna, morphology, decomposition, polychaetes, holothurian, crinoid, rattail, brotula, halosaur, swimbladder This program is a continuation of the previous show in which we began our journey through the deep sea. If you remember in our last show we started out in the epipelagic or surface zone and went on to the mesopelagic or twilight zone where there is very little light. We even discussed how some organisms, the vertical migrators, migrated daily between the two zones. Today we will journey even where do you think the world’s deeper, beyond the point where the most abundant fish is found? The sun’s rays can reach to explore epipelagic zone? Of course not, deep water and ocean bottom they are found in the meso and creatures. You may wonder why bathypelagic zones. Any one would study the deep sea. But, ichthyologist (a person that if you remember from last week’s studies fish), will tell you that the show, about 60% of the world is world’s most abundant vertebrate deep sea. It is the average earth (animal with a backbone) is the environment. It is more bristlemouth. These are also representative of our planet than a known by their genus name meadow or a forest! Knowing this, Cyclothone. The bristlemouth, Cyclothone acclinnidens Deep Sea Adaptations The average depth of the ocean is fact, several places far exceed the 3800 meters or 12,500 feet. It is average depth. The deepest point not all 3800 meters deep; the of the oceans is located in the ocean floor has irregular Western Pacific, north of New topography, just like on land. In Guinea in the Marianas Trench. It is one of many deep trenches in the Every organism, whether it lives in Western Pacific. It is known as the the deep sea or on land, uses the Challenger Deep, named after the energy it receives from the food it British vessel that took the first eats for three purposes; growth, sounding in 1951, establishing it as reproduction and maintenance. the deepest point in the world’s However, the environment in oceans. Mount Everest could be which an organism lives affects dipped in it with over a mile to how much energy is used for each spare! purpose. Today we will look at how an organism living in a food- There are several general changes poor environment would direct its that occur in organisms as they energy stores. Growth, is useful: live deeper in the ocean. As the larger you are, the fewer things mentioned in the previous show, can eat you. Reproduction is food becomes scarcer the deeper helpful to ensure survival of your you go. This is because the food species. Maintenance is the web begins with the energy used to stay alive, such as phytoplankton, which can only the pumping of your heart! We can occur in the photic or well-lit zone. measure maintenance by One consequence of living in a measuring the metabolic rate, food poor environment is a greater which is a measure of how fast an water content. There is a higher organism makes things like percentage of water in an muscles and how fast it can break organism’s tissues the deeper it down other things like food. lives in the water column. This Scientists have shown that the happens because there is less food metabolic rate of deep-sea fishes available to build strong muscles, decreases the deeper they live. A so bathypelagic organisms tend to fish living at 1000 meters breathes have weak, flabby muscles. Even more slowly than an animal living bones become less dense as you go at the surface. deeper in the water column. This gives the fish two basic advantages: 1. It allows more of the food it eats to be directed into growth and reproduction. 2. It allows it to live much longer on the food it does eat; it doesn’t burn it up as fast as a shallower living fish. Now, with these basics in mind, on to the bathypelagic zone! Organisms of the bathypelagic zone The bathypelagic zone is similar luminescent lure that the females to the mesopelagic zone. It is cold have. Their main purpose is to (2-5°C). It is dark, but here, there locate a female. The females do is no sunlight at all. The pressure not have a well-developed sense of is enormous; it ranges from 1500 smell. She uses her lure to attract to 6000 pounds per square inch or prey and a mate. This is a strategy psi. Food is even sparser than in for living in the food poor the mesopelagic zone, therefore environment of the bathypelagic organisms have higher water zone. A large fish requires more content. Many fish are black in food than a small one. The males color and their eyes are usually do not need to be large, a small reduced. The only light available male can make a lot of sperm. But are flashes of biological light the females can produce more eggs (bioluminescence) produced by the if they are large, therefore they do organisms themselves. Some male need to attract prey and hence they angler-fishes have sensitive, have the luminescent lure. They specially adapted eyes, which help just hang out and wait for prey to them not only catch luminescent come to them. The males put more prey, but to find the flashing lure energy into their olfactory organs of the female angler-fish. They are and in the active searching for an exception to the rule of reduced females. However, once he finds eyes in the bathypelagic zone. the female he bites down and Some of the male anglerfish also becomes a permanent attachment! have well-developed olfactory The male anglerfish receives his organs (responsible for sense of nourishment from the female and smell, like your nose), to help she receives sperm from him. them locate the females. The male Some females may have more than anglerfish is much smaller than the one male attached! female and they don’t have the Female Anglerfish Haplophryne mollis with male attached Many of the crustaceans in the in the gut wall. This is probably to bathypelagic zone have the reddish hide any light produced by coloration that is found in the luminescent prey items. Here is a mesopelagic zone. They have picture of a gulper eel, olfactory hairs and extremely long Eurypharyngidae, notice its tiny antennae, which are used for eyes and huge mouth. Some fish touch. On the other hand, squids, can even unhinge their jaws so that have virtually no olfactory organs they can open them wide enough and therefore need well-developed to eat a large organism. eyes at all depths. Most fish in the deep-sea have very large mouths and teeth, and often have stomachs capable of distending to accommodate large prey. Some fish have pigmentation Eurypharyngidae Another way that bathypelagic is a nearby disturbance the cupula fishes differ from their shallower bends and moves the cilia, which living counterparts or even their stimulate sensory cells below. An benthic or bottom living counter easy way to understand this is to parts is in their lateral line system. cup your right hand and just lightly The lateral line system in fishes touch the hairs on your left arm. gives them a “distance touch” The motion of your hand moved sense; it helps them detect motion your arm hairs and stimulated the around them. It usually consists of nerve cells below. Most fishes a canal which contains specialized contain the neuromasts in canals, cells called neuromasts which either open mucous filled canals or contain cilia (sense hairs) covered closed canals, such as a lateral by a gelatinous cupula. When there line. This helps buffer the stimulus of currents or other water bathypelagic fishes and gentler movements not caused by other water movements. Water organisms. However, in the movements above the bathypelagic bathypelagic fishes the neuromasts zone and at the very bottom in the are found in either wide open benthos tend to be stronger. Also, canals such as found in the flabby many of the fish themselves are whale-fishes or on long stalks such more active than the bathypelagic as those found on the gulper eels! fishes, therefore, creating more This may be due to the rather water movement against the inactive life style of the sensitive neuromast. lateral line A rattail, A free ending Macrouridae neuromast Organisms of the Benthos and Near-Bottom Animals that reside permanently there is total darkness in the on the bottom are called benthic bathypelagic zone, however, the organisms. Organisms that live on benthic organisms here have a few or near the bottom are known as advantages over their pelagic demersal organisms. The counterparts. They do not have to diversity of organisms that live on swim to keep themselves from or near the bottom is greater than sinking. They can just rest on the that of the deep-sea pelagic bottom; buoyancy is not a organisms and they are usually of problem. In addition, anything a larger size. There are about 1,000 sinking will end up on the bottom, known species of demersal fish instead of just passing through as it alone between 1,000 and 7,000 would in the meso and meters depth. They are found just bathypelagic zones. Therefore, if offshore all they way down to the you are looking for food, the deepest part of the ocean.