Osteichthyes: Bony Fish Introduction

Osteichthyes: Bony Fishes - Introduction

• Osteichthyes, known as bony fish, are a diverse group with skeletons primarily of bone, unlike cartilaginous fish (Chondrichthyes).
• The name is derived from the Greek words "osteon" (bone) and "ikhthus" (fish).

Brief History/Ancestry

• Bony fish have a long evolutionary history, dating back to the Late Silurian period (420 million years ago).
• That period was a time of advancements in both marine and terrestrial life.
• Following the Ordovician-Silurian extinction, it marked a period of recovery and diversification.
• They evolved from early jawed fish.
• They became the most diverse and successful group of vertebrates.
• Guiyu oneiros is the oldest known bony fish (osteichthyan) and comes from the Late Silurian period.
• "Guiyu" means "ghost fish" in Mandarin
• "oneiros" is Greek for "dream."

General Characteristics: Skeletal Structure

• Endoskeleton is made of true bone (ossified tissue) rather than cartilage, unlike that of cartilaginous fish.
• Skull is composed of multiple fused bones and has a well-defined jaw with teeth (some species have tooth plates).
• Vertebral Column provides structural support and flexibility.
• Notochord is present in early development but is replaced by vertebrae.
• Fins and Limb Structure are supported by bony fin rays (lepidotrichia) in ray-finned fish; lobed fins in lobe-finned fish have internal bones homologous to tetrapod limbs.
• Ribs protect internal organs.
• Pectoral and pelvic girdles support fin attachment.
• Operculum (Gill Cover) is a bony plate covering gills, aiding in respiration.

Swim Bladder Function

• A gas-filled organ found in most bony fish which helps them control buoyancy in water.
• Physostomous Swim Bladder is found in more primitive fish (like goldfish and catfish) and is connected to the esophagus via a duct, allowing the fish to gulp air to fill or release air.
• Physoclistous Swim Bladder is found in more advanced fish (like perch and bass) and is not connected to the esophagus, where gas exchange occurs through the rete mirabile, a blood vessel network.

Scales and Body Covering

• Cycloid scales are round, smooth, without spines or ridges, as found in fish like salmon, trout, and carp.
  • This allows greater flexibility and speed while reducing friction.
  • Scales are composed of thin layers of bone as a streamlined, smooth, shiny appearance.
• Ctenoid scales are similar to cycloid but with tiny comb-like structures on the outer edges, and are common in perch, bass, and other modern fish.
  • They reduce drag; made up of bone with a more textured surface and fine teeth along the edges.
• Ganoid scales are diamond-shaped or rhomboid, with a hard, glossy, and thick outer layer and are found in more primitive bony fish like gars, sturgeons, and bichirs.
  • They provide extra protection and a more rigid structure that is also heavy, durable, and armor-like.

Respiration Through Gills

• The Gill Arches support the gills, provide a framework for the gill filaments (typically four gill arches on each side).
• Gill Filaments cover each gill arch and are made of thin, flat layers called lamellae,
• Gas exchange occurs in the lamellae of gill filaments.
• The Operculum is a bony plate protecting the gills and helps control water flow,
• Gill rakers are comb-like structures on the gill arches that filter debris and food particles.
• The Step, Description in water intake occurs when water enters the mouth, fills the buccal cavity.
• During Gas Exchange oxygen diffuses from water to blood, and carbon dioxide diffuses from blood to water.
• The operculum helps regulate water flow over the gills.
• Water exits through the operculum after oxygen has been absorbed.

Comparison to Other Groups

• Bony fishes (Osteichthyes) have a bone skeleton, swim bladder, and gill cover (operculum).
• Cartilaginous fishes (Chondrichthyes) lack a swim bladder and gill cover (operculum)
• Jawless fishes (Agnatha) have no true skeleton, swim bladder, or gill cover (operculum).
• Bony fishes possess cycloid, ctenoid, or ganoid scales
• Cartilaginous fishes possess placoid scales.
• Jawless fishes lack scales or have bony plates.

Evolutionary Origins

• Earliest bony fish likely evolved from placoderms (armored jawed fish). E.g., Dunkleosteus
• By "Age of Fishes," Devonian period, bony fish diversified into two groups:
  • Sarcopterygii (lobe-finned fish) are the ancestors of amphibians, reptiles, birds, and mammals.
  • Actinopterygii (ray-finned fish) are the dominant group of fish today.

Rise of Ray-Finned Fish (Carboniferous-Permian, ~360-250 MYA)

• Early Actinopterygians were relatively small and lived in freshwater, outcompeting other fish due to their structures.
• Key Adaptations:
  • Ray-supported fins provided better maneuverability than fleshy fins.
  • Swim bladder improved buoyancy control with minimal energy.
  • Efficient jaw and skull structures enabled adaptation to various feeding strategies.

Mesozoic Era (Triassic-Cretaceous, ~250-66 MYA): Age of Modern Fish

• Teleosts (advanced ray-finned fish) appeared.
• Equipped with jaws, flexible fins, and body shapes, allowing them to thrive in environments
• Key Adaptations:
  • Advanced Jaw Structure and Feeding Adaptations
  • Flexible Fins for Better Swimming
  • Lighter and More Adaptable Skeletons
• Many modern fish families evolved leading to diversity

Cenozoic Era (66 MYA-Present): Age of Teleosts

• Bony fish continued to diversify.
• Over 30,000 species of Osteichthyes exist, making them the most diverse group of vertebrates.

Systematics and Taxonomy

• Domain Eukaryota includes organisms with eukaryotic cells (cells with a nucleus and membrane-bound organelles).
• Kingdom Animalia includes multicellular, heterotrophic organisms that lack cell walls.
• Phylum Chordata includes animals with a notochord, dorsal hollow nerve cord, and pharyngeal slits.
• Subphylum Vertebrata includes chordates with a vertebral column (backbone) made of bone or cartilage.
• Class Osteichthyes includes jawed fish with a bony endoskeleton.
• Two Subclasses of Osteichthyes: Subclass Sarcopterygii & Subclass Actinopterygii.

Subclass Sarcopterygii (Lobe-Finned Fishes)

• It is characterized by fleshy, lobed pectoral and pelvic fins supported by bones.
• Greek word sareos means "flesh" and pterygium means "fin".
• They have two dorsal fins with separate bases and lungs, gills, and a heterocercal tail.
• Later sarcopterygians have a continuous flexible fin and are ancestors of terrestrial vertebrates due to their limb-like structure.
• Two orders include: Order Crossopterygii & Order Dipnoi.

Order Crossopterygii

• Comes from the Greek word crossoi and pteryx and has paired fins lobate with a three-lobed caudal fin, present internal nares/spiracles
• Ex: Primitive fleshy-finned extinct fishes, example: Latimeria.
• Order Dipnoi comes from the Greek words double and breathing: continuous median fins for diphycercal tail.
• absent Premaxillae and maxillae, present internal nares but absent spiracles.

Subclass Actinopterygii (Ray-Finned Fishes)

• Pteryz means "fin;" ray-supported fins provide agile, efficient swimming: single/divided dorsal fin & swim bladder.
• Greek word actis means "ray"
• Highly diverse, with over 30,000 species, most widespread.

Superorder Chondrostei

• Derived from the Greek words for "cartilage" and "bone," their skeleton is primarily Cartilaginous with a large mouth opening, and Ganoid scales
• Has a Heterocercal Tail Fin.

Order Polypteriformes

• Rhomboid Ganoid Scales, Lobed Pectoral Fins, Dorsal Fin of 8+ Finlets, Ossified Skeleton.
  • Ex: Polypetrus ornatipinnis
• Order Acipenseriformes: scaleless or bony (Ganoid) scutes w/ Cartilaginous Skeleton
  • Ex: Acipenser transmontanus

Superorder Holostei

• Smaller mouth and Heterocercal Tail Fin, skeletons are ossified
• Comes from Greek halos, osteon with Order Amiiformes: has Cycloid scales plus movement control
  • Ex: Amia calva.

Order Lepisosteiformes

• torpedo-shaped bodies, sharp jaws, ganoid scales
  • Ex: Lepisosteus osseus

Superorder Teleostei

• Largest Order of Fish -- Over 10,000 species in freshwater/marine environments.
• A Homocercal Tail with Ctenoid Scales is common.
  • Spiny and Soft-Rayed Fins seen, Ex: Oreochromis niloticus
• Order Cypriniformes possess 4,000 freshwater fishes located mostly in rivers, lakes, and ponds
  • No True Teeth in Jaws so instead, pharyngeal teeth assist.
  • Scales Cycloid or Absent, Well-Developed Barbels, Ex: Cyprinus carpio
• Other Orders include Clupeiformes e.g. Sardinella frimbiata, Scopeliformes e.g. Myctophum asperum, Anguilliformes e.g. Anguilla japonica, Beloniformes e.g. Hyporhamphus unifasciatus, Syngnathiformes e.g. Hippocampus kuda, Channiformes or Channa striata,

Physiology: Nervous System

• The bony fish brain is divided into three parts:
  • Forebrain: Involved in olfactory or smell processing and behavior (e.g. eels have a good sense of smell)
  • Midbrain: Processes vision, learning, and motor responses (e.g. mudskippers have excellent eyesight, while blind cave fish has reduced midbrain)
  • Hindbrain: movement, muscle tone, and balance, and also sensory information (e.g. sailfish and marlin have an enlarged hindbrain)
• Spinal cord: tubular structure which is a central conduit for nerve signals between the brain and the body
• Peripheral Nerves: extend from the spinal cord to tissues and organs
  • Somatic nerves control skeletal muscles
  • Autonomic nerves regulate involuntary functions
• Lateral Line System: Adaptation that allows them to sense changes in water pressure and detect prey/predators
  • Neuromasts: Organs with hair-like cells.

Muscular System

• Structure: Bony fish have a specialized system that allows for movement
  • Myomeres: bands for locomotion.
  • Myosepta: tissue separates each myomere.
• Fiber Types: use a mixture.
  • Red Muscle Fibers: sustain swimming.
  • White Muscle Fibers: are used for quick strikes.
• Fin Musculature stabilizes
  • Pectoral/Pelvic Fins steer.
  • Dorsal/Anal Fins balance.
  • Caudal Fins propel.
• Jaw Muscles facilitate feeding, respiration
  • Adductors close the jaw.
  • Abductors open the jaw.

Skeletal System

• Axial Skeleton is the Central support, protecting the spinal cord and brain.
  • Vertebrae allow flexibility.
  • Cranium protects the brain.
  • Ribs support protection
• Appendicular Skeleton: provides maneuverability.
  • the Pectoral/Pelvic Girdle support the fins

Respiratory System

• Gills extract oxygen and expel carbon dioxide.
  • Gill Arches support gill filaments.
  • Gill Filaments provide a large gas exchange surface.
  • Gill Lamellae are plate-like structures.
  • Operculum serves a shield, mouth, and buccal cavity direct water.
• Respiratory Functions:
  • Countercurrent exchange in the gills absorbs oxygen.
• Water Flow/Ventilation: moves water through their gills.
  • Buccal Pump actively moves water.
  • Ram Ventilation forces water by swimming with the mouth open.

Circulatory System

• Structures: A two-chamber hearts pumps blood.
  • One atrium receives deoxygenated blood, a ventricle pumps blood to gills
  • blood flow is smoothed by Bulbus Arteriosus which avoids pulsations.
• The System of Blood Vessels follows 3 modes:
  • Arteries move oxygen-rich to the body.
  • Veins return deoxygenated to the heart.
  • Capillaries facilitate gas exchange.

Endocrine System

• regulates sexual activity, growth, osmotic pressure, general metabolism, and skin color.
• Ultimobranchial secrete calcitonin
• unique Stannius islets secrete hypocalcin or eliciting antihypercalcemic response
• produces Urotensin I which includes somatostatin.
• Urotensin II includes mammalian corticotropin-releasing hormone

Integumentary System

• covers the external surfaces of the body: skin extensions of barbels, composed of the epidermis and dermis.
• Cosmoid Scales are found in extinct lungfishes and are hard, enamel-like with ganoid (articulating)
• Cycloid Scales have an outer layer which adds concentric layers.
• Ctenoid Scales do the same but also have spiny extensions.
• Extensions "whiskers" are sensory on the head area of the fish.
• Flaps are bone gills to direct the flow.

Skin: protection

• Mucous secretions keep the skin free of pathogens/particles.
• Nonkeratinized epithelial repair wounds w/ nonkeratinized cells by means of phagocytosis
• Hyperplasia thickens the skin.
• Scales create encasements and defenses
• Noxious venoms are secreted to avoid attack
• Leukocytes provide "wandering" adaptive immunity.
• Pigmentation uses coloration and bioluminescence

Digestion

• Important processes cover absorption/transport of nutrients.
  • Predatory mouths are typically for grasping, while omnivorous are "sharper."
• The structure moves toward the stomach in stages
  • Esophagus is a mucus lining.
• Stomach varies as a "bent muscular tune" to hold substances
  • Pylorus blocks movement
• Tissue (Caeca) is found around.
• Liver produces energy in the form of glycogen as bile
• Intestine is a thin tube, and the digestive system terminates at the anus

Excretory System/Reproductive System

• Excretion is removed and concentrated.
• "Gonads," ovaries, and testes follow the same route
• sexual readiness begins at points
• the reproductive system then develops either egg (oviparous) or withy yolk (Bivalvia), after which parental care may occur.

Distribution and Ecology: I. Habitat

• Bony fish inhabit almost every body of water (fresh, sea, brackish).
• Some live in the deep sea (11 km deep) to lakes above sea level (5 km high).
• About 58% of bony fish reside in marine environments, while 42% in freshwater.
• Tunas are pelagic, flatfishes are bottom-dwellers, and gobies are sand-burrowers.
  • Sunfish are spotted most often at the ocean surfaces and can "hibernate" under mud if trapped at all.

Distribution and Ecology: II. Endemic Bony Fish

Mistichthys luzonensis (sinarapan)

• commonly known as the Sinarapan or Tabyos is from the Bicol River
• Found in Lakes Buhi, Bato, Katugday, and Manapao

Pait (Barbodes amarus)

• was exclusively found in Lake Lanao (Mindanao) and is now considered extinct

Schoppe's Barb (Cyclocheilichthys schoppeae)

• a species of cyprinid fish found in Palawan, Philippines

Twocoat coralblenny (Ecsenius dilemma)

• coral reefs specifically in the Philippines

Distribution and Ecology: III. Migration

• Bony species migrate distances due to food, habitat, reproduction, cycles, and temperature.
• Almost all tuna are migratory
  • ex) Albacore migrate 8,500km of coast
• Billfishes are highly migratory
  • ex) Black marlin (10,680 km)
• Some bony fish are also Diadromous with separate habitats
  • Anadromous - the hatch in freshwater then ocean to spawn

Distribution and Ecology: IV. Trophic Interaction

• Herbivores eat "bony" algae and make great health
• Carnivores are predators and invertebrate.

Distribution and Ecology: V. Intraspecific Interactions

• Territoriality means that resource control and the mating and reproduction process occurs
• In that reproductive process, some give parental care
• Schooling involves a safety-in-numbers effect

Distribution and Ecology: VI. Interspecific

• Bony structures can enhance for "fishing efficiency"
• The interactions shape systems/ecosystems like with predation (snapper), competition (invasive species), mutualism (cleaner fish), or parasitism (commensal fish).

Distribution and Ecology: VII. Life History

• Each cycle begins is eggs by which fertilized ones become embryos that "hatch" to begin the larval state
• These larvae form into juveniles until they become adulthood
• This is all a vulnerable stage

Distribution and Ecology: VIII. Ecological

• Cycles feed at all stages to provide increased levels of health
• Engineering leads to various habitats with "ecosystem" symbiosis
• Ecosystems of the bony are able to be indicate via population indicators

Distribution and Ecology: IX. Human Impacts

• Overfishing and damage all habitats.
• Climate and pollution contribute, impacting the behavior of reef species

Trapping Methods/Analysis: A. Cast Nets

• Series of tailored fittings together form the "fishing net"
• A handline ensures retrieve, mesh measures in millimeters
• Braille lines close, and the swivel helps with "twists"
• Lead line traps, it is small

Trapping Methods/Analysis: B. Gill Nets

- Check the cast

• Each net comes "armed" with extra float, by lines that secure it
• The size of each anchor needs to be great since it measures at range

Trapping Methods/Analysis: C. Seine Nets

• As the rope is adjusted:
  • The wing of rope "guides" the fish
  • Lead is weighed Often, the nets create discards