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Chapter 8 Marine Fish Figure 8.01 Figure 8.02 Characteristics of Subphylum Vertebrata A notochord that has developed into a spinal cord protected by vertebrae and a head with a brain characterize organisms in this subphylum. Vertebrates consist of the most complex, large, fast, and conspicuous organisms. They include us, the organism that has had the most effect on the global biosphere. Significance of Class Agnatha This is the class of the jawless fish. Species include lampreys and hagfish. Organisms in this class are significant because they may represent the ancestor of bony fish/sharks. Scientists theorize that during the Cambrian period the first of three gill arches on a jawless fish evolved into the first jaws. Having jaws allowed vertebrates to become very successful predators. Having jaws put organisms in class Chondrichthyes (sharks and rays) and class Osteichthyes (bony fish) near the top of marine food webs. Characteristics of Sharks and Rays Class Chondrichthyes includes sharks, rays and their close relatives. Sharks and rays don’t look similar on the outside, but share a basic anatomy that classifies them together. Sharks and rays are jawed fish, that lack a swim bladder, and have cartilaginous skeletons. Special Attributes of Sharks and Rays Sharks and rays are successful predators: Subclass Elasmobranchii have cartilaginous skeletons. This characteristic saves energy. Saving energy is one of the things that have made them successful predators. Sharks have a sense of smell that detect incredibly diluted substances. Sharks have a “conveyor belt” of multiple rows of teeth. They swing into place as old teeth wear out and fall away. Special Attributes of Sharks and Rays (continued) Sharks and rays have other interesting characteristics: Both have lateral lines – lines of sensory hair along the length of the body that detect water motion and vibrations. Unique to elasmobranchs is electroreception – the ability to sense minute electricity created by muscles and nerves. Sharks and rays have organs called ampullae of Lorenzini which you can see as visible pits near their snouts used to detect the electrical current. 5-6 Special Attributes of Sharks and Rays (continued) Elasmobranchs differ in their reproductive strategy. Sharks and rays produce fewer, but more mature offspring. Most fertilize their eggs internally. The male deposits sperm in the female via a pair of copulatory organs called claspers found at the base of the pelvic fins. The female lays an egg case in which the juveniles develop for up to six months at which time one or more sharks or rays emerge. A few shark species are ovoviviparous – the eggs hatch within the mother’s body. They give birth to live young rather than egg cases. The largest fish in the ocean. Shark size ranges from hand-sized to the whale shark – the largest fish in the ocean. Whale sharks can reach 14 meters (46 feet). Basking sharks can reach 10 meters (33 feet). Megamouth sharks can reach 6 meters (20 feet). All three are filter feeders that consume plankton. Special Attributes of Rays Superorder Batidoidimorpha of subclass Elasmobranchii consists of the rays, which includes skates and guitarfish. Ray anatomy is well suited to life on sandy bottoms or midwater. Specially adapted to life in midwater are the eagle ray and manta ray. Pectoral fins have become “wings” that stretch forward over the gills and are fused to the sides of the head. Shoulder girdles are flattened and many bones are fused together for rigidity. No longer need a tail for swimming, the tail has become a defensive whip in some species. Rays literally fly through the water. The largest rays are mantas with wingspans exceeding 8 meters (26 feet). Like the largest shark, the mantas feed on plankton. Figure 8.14a Figure 8.12a Figure 8.26 Figure 8.04 Figure 8.05b Figure 8.06b Figure 8.07 Figure 8.08a Characteristics of Bony Fish Class Osteichthyes are jawed fish with bone skeletons. Most have a swim bladder and scales. Most control buoyancy by adding or releasing gas to/from their swim bladder. They control the swim bladders with oxygen gas exchanged to and from blood circulation. Many have a special organ called the gas gland and the rete mirabile that take up gases from the bloodstream for the swim bladder. This allows many species to hover nearly motionless in midwater. Most bony fish reproduce externally. The female lays her eggs, the male immediately fertilizes them. 5 - 17 Their strategy is to produce a vast number of off-spring with only a few expected to survive to maturity. Characteristics of Bony Fish (continued) Bony fish have characteristics for life on the reef and for life in the open ocean: Bony Fish – Half the World’s Vertebrates Bony fish have lateral lines that detect water motion and vibrations. Most open ocean and schooling fish have a torpedo-like streamlined shape that minimizes drag and turbulence. This fusiform shape is spindle-like, slightly broader at the head and a V-shaped tail. This makes them fast swimmers. Most open-ocean and schooling fish have a lighter underside and dark Chapter 5 Pages 5-74 & 5-75 topside for concealment. Bony fish living in reefs and on the bottom use survival strategies more diverse and include concealment and armor instead of swimming. 5 - 18 For this reason, you see far more diversity in color, shape, and size among reef and bottom fish. Types of Marine Fish Agnatha These jawless fish have a muscular, circular mouth with rows of teeth in rings Long, cylindrical body Lack paired fins and scales seen in other fish Two types of jawless fish exist- hagfish and lampreys Ectothermic Lamprey – www.wikipedia.com Types of Marine Fish Hagfishes – 20 species – Exclusively marine – They feed on dead and dying fish and marine mammals primarily – Live in burrows in soft sediments – Produce large quantities of mucous from glands in the skin to protect them while feeding www.wikipedia.com Pacific Hagfish (Eptatretus stoutii) - 4 pairs of sensory tentacles around mouth - 12 pairs of gill slits - SLIME Types of Marine Fish Lamprey 30 species Live in freshwater (lakes) and salt water Adults of some species spend a large portion of their life in the sea, but return to freshwater to breed; adults normally die after breeding. Parasitic: They feed on living fish by rasping into the sides of fish with their sucker-like mouth and consuming blood, tissue and body fluids Produce anticlotting agent More Advanced Groups of Fish Fishes in the Classes Chondrichthyes and Osteichthyes are considered to be more advanced. General Characteristics (advancements) seen in these groups: – Highly efficient gills – Scales cover the body – Paired fins – A wide variety of jaw and feeding types – Lateral line and other sensory organs – Streamlined body Osteichthyes, The Bony Fish Skeleton composed of bone More species that all other vertebrates combined- over 23,000 species worldwide Gills used for respiration Hinged jaws allow for a variety of different feeding strategies Homocercal tail (two lobes of equal size) provides forward thrust www.wikipedia.com Osteichthyes, The Bony Fish Flat bony scales protect body ctenoid (tiny spines) or cycloid (smooth) Bony operculum covers the gills (provides better protection against injury compared to gill slits for each gill) Lateral line used in sensory capacity and communication Swim bladder used for buoyancy control (some bottom dwelling fish lack swim bladder) Variable body plans are adapted for specific environments Osteichthyes, Body Shape Body shapes vary greatly dependent on the niche Ex. flounders and soles (flat shape) live on the bottom and cover themselves slightly with sand to camouflage themselves from potential predators as well as prey Osteichthyes – Body Shape of FAST fish Tuna, billfish, and other fast moving predators are long, streamlined and most of their fins serve as rudders (very little flexibility except in caudal fin) This body shape allows these predators to cut through the water quickly Notice, too, that the area of the body called the caudal peduncle (area just before the tail) is very thin – this allows all the muscles to concentrate in this area allowing for greater thrust of the caudal (tail) fin (this means FAST swimming capabilities) Sailfish Osteichthyes – Body Shape of not so fast fish Angelfish – coral reef fish example – not open ocean fish Angelfish and the like inhabit coral reefs, oyster reefs and other similar environments In these fish, the body is not as streamlined and the fins are feather-like for lots of flexibility This flexibility allows for greater control around the features that would be seen in a coral reef type environment (crevices, etc) – Humphead parrotfish www.animalphoto.tk Osteichthyes – Shape of fish that don’t swim far Other fish have a shape that allows for camouflage in their environment For example, fish like the toadfish and the stonefish actually look like rocks or “scenery” and thus can go undetected by predators or prey www.fishimage.blogspot.com www.njsciba.net Osteichthyes – Color Patterns Countershading is seen in virtually all fish species In countershading, the ventral (belly) area of the fish is lighter than the dorsal area of the fish This allows the fish to “blend in” with the environment If a fish is seen from above, the darker coloration of the dorsal area blends in with the darker color of the ocean bottom If the fish is seen from below, the lighter coloration of the ventral surface blends in with the lighter coloration of the ocean surface www.nationalgeographic.com Osteichthyes, The Bony Fish – Coloration patterns: Slower swimming fish often have bars or stripes that help break up the silhouette of a fish (a form of disruptive coloration) This helps with predator avoidance Some also have coloration that helps them blend in with environment (known as cryptic coloration) www.sunysb.edu Osteichthyes, The Bony Fish Coloration Patterns: Circular patterns on or near the caudal fin Confuses predators who are not sure which end of the fish is the head If fish attacked on caudal end where the black dot looks like an eye, she can probably get away with minor damage If attacked on his head region, she may sustain serious, life threatening damage Warning Coloration – use color to advertise their bad taste or poisonous nature – www.animalworld.com www.fishwallpaper.net www.inkart.net Swimming Patterns Fish exhibit an “s-shaped” swimming pattern Bands of muscle along the body called myomeres drive this swimming motion Depending on the type of fish, different fins may be used primarily for the forward movement Swimming Patterns A) eels swim by undulating body in lateral waves from head to tail B) fast fishes with shorter bodies – flex caudal tail C) surgeonfishes, parrotfishes – move only the fins D) trunkfishes and porcupine fishes swim slowly by moving base of tail and rest of body remains immobile Specializations for swimming Myomeres – bands of muscles that produce rhythmic contractions for swimming in S-pattern Swim bladders in bony fish Swimming Patterns In bony fish, pectoral fins are not needed for lift (like in sharks) and thus are normally not stiff in construction (exception: fast swimming species like tuna, billfish, etc) In contrast, the pectoral fins in many bony fins are flexible and used for maneuverability In some slower-swimming species, forward movement is mainly provided primarily by the pectoral fins (see fish in tanks! – coral reef fish) In other species, all the fins may be flexible and highly modified for camouflage (example: sea horses and leafy sea dragons and weedy sea dragons Fins will not allow for significant forward movement Flying fish example Fish Gills The construction of the gill is the same in all fish – Gill arch supports the entire structure Gill rakers are on the forward surface of the gill arch and Gill filaments trail behind the gill arch Like in the human lung, exchange of oxygen and carbon dioxide takes place on these surfaces Figure 8.17 The gills of fishes are very efficient for gas exchange. Bony fishes have 4 pairs of gills (a), each containing 2 rows of gill filaments (b). Lamellae in gill filaments (c) increase the surface area of the gill filaments. (d) Diffusion of oxygen from seawater into the blood gets a boost b/c the water flows across the lamallae in the opposite direction to that of the blood. (e) The concentration of oxygen (indicated by dots) is always higher in the water than in the blood. If circulation were not reversed, blood to the body would have less oxygen. VIDEO Acquiring and Processing Food Mouth structure also reveals the dietary preferences of fish As an example, the “beak” (fused teeth) seen in parrotfish allows for these fish to scrape algae and other organisms off of hard surfaces The butterfly fish uses its long tube-like mouth to feed on corals While the barracuda uses rows of sharp teeth and a wide mouth to capture its prey – other fish Acquiring and Processing Food Jaw/Mouth Structure Acquiring and Processing Food: Mouth Structure The position of the mouth is also important A strongly forward facing mouth is important in fish who chase down their prey (as seen in barracuda) A downward facing mouth would be seen in fish feeding at/near the bottom (opposite for feeding on surface of water) Acquiring and Processing Food: Digestion Organs involved: stomach, intestine (with anus), liver, pyloric caeca and pancreas The stomach is structured very similarly to the human stomach – stretch receptors in the wall of the stomach indicate when a meal is present and needs to be mechanically digested by the churning motion of the stomach wall Acquiring and Processing Food: Digestion Intestine, pyloric caeca (tubes at end of intestine), pancreas and liver (bile breaks down fat) all secrete digestive enzymes The intestines of carnivorous fish tend to be short and straight while the intestines of herbivorous fish are longer and more coiled (plant and algae material is more difficult to process, so it needs to stay in the intestines longer) Acquiring and Processing Food: Digestion The Circulatory System Two chambered heart that pumps blood throughout the body (in contrast to the 4 chambered heart seen in mammals) System of arteries, veins and capillaries takes blood to the body tissues and returns it for re- oxygenation by the gill filaments O2 and CO2 diffuses across thin membranes of capillaries either in the gills or at the tissues of the body Figure 8.15. The circulatory system of fishes consists of veins that carry deoxygenated blood (in blue) from the body, a twochambered heart that pumps blood into the gills for oxygenation, and arteries that carry oxygenated blood (in red) to rest of body). Fluid Balance in Fish Remember osmosis and diffusion are always at work in an organism Fish need mechanisms to combat the issue of water loss – OSMOREGULATION Fish osmoregulate by: Swallowing seawater and expel the solutes in the digestive process (this allows them to keep the water and lose the solutes) Most marine fish pass very little urine that is processed by the kidneys, and is highly concentrated with solutes with very little water content Fig. 8.18 Marine fishes - salts excreted by kidneys and drink water The Fish Nervous System The fish have a brain, spinal cord and numerous nerves like other vertebrates Smell: Fish possess olfactory sacs (with nostrils/nares) Hearing: Inner ears are set in fluid-filled canals with sensory cells similar to the lateral line system. Taste: Detect chemical stimuli by using taste buds are located in the mouth, lips, barbels and skin Sight: The position of the lens changes like in a camera (Note: Different from land animals where the lens changes shape for focusing on items The Fish Nervous System All fish rely heavily on the lateral line system The lateral line is a series of pores and canals lined with specialized organs called neuromasts that are specialized to detect vibrations Lined with hair cells – similar to those in your cochlea Orientation, predatory behavior, social schooling Fish Behavior Schooling Widely used (+4000 species school) Why school? Predator deterrent Spawning aggrigation Migration Enhanced foraging Fish Behaviors Territoriality Some fish are territorial by nature all the time, others are only territorial during reproduction Fish maintain their territories normally by “posturing” to show their aggression Posturing can include raised fins, open mouth, darting, etc. Fights between individuals are actually rare Damselfish and algae Reproduction in Fish Sex hormones control the development of sperm and eggs in fish Release of sex hormones cued by water temperature, day length, specific tide cycles, etc. Broadcast spawning most common Some fish have internal fertilization (sperm is inserted directly into the female by the male) Complex mating behaviors are seen in some species (Ex. Banggai cardinals, potato cod) Color or body changes can cue reproduction Atlantic cod mating behaviors. 1. Male establishes territory. 2. Male makes displays (grunting, spreading fins, etc). 3. Female (if the male is lucky) spawns with male. Fish Reproduction Some fish are hermaphroditic Simultaneous hermaphrodites – rare (ex. salmon, some deep sea fish) Sequential hermaphrodites) Protandry - males then females (ex. anemone fish) Protogyny – females males (ex. wrasses, parrotfish) Cues for changes - changes in social structure or environment Fish Reproduction Depending on the species, fish can either be: Viviparous – young are born live Oviparous - egg layers (most common) Some parents protect eggs, though most do not Ovoviviparous – eggs are kept inside and “hatch” before being released from female reproductive tract RARE: Parthenogenic species - in this reproductive plan, young develop directly from the unfertilized eggs of the female (no DNA from males) – the young are “clones” of the female Figure 8.08b Figure 8.12b Figure 8.14b Figure 8.15 Figure 8.16a Figure 8.16b Figure 8.17a Figure 8.17b Figure 8.17c Figure 8.17d Figure 8.17e Figure 8.18a Figure 8.18b Figure 8.19 Figure 8.21a Figure 8.21b Figure 8.21c Figure 8.21d Figure 8.22 Pg. 164 Figure 8.24 Figure 8.25 Figure 8.28 Figure 8.13a Figure 8.09a Figure 8.09b Figure 8.09c Figure 8.09d Figure 8.09e Figure 8.09f Figure 8.09g Figure 8.09h Figure 8.09i Figure 8.11a Figure 8.11b Figure 8.11c Figure 8.11d Figure 8.13b Figure 8.13c Figure 8.13d Figure 8.13e