Chapt 10 Bony Fishes Ichthyology “the study of fish”
Phylum Chordata• Class Actinopterygii – “modern bony fish” – 25,000 species or ½ of all vertebrate species – So diverse no one characteristic can differentiate them from sharks, skates, and rays (cartilaginous fish) – Taxonomy of fishes are still changing as new technology and research reveal new characteristics
Phylum Chrodata• Characteristics – Presence of swim bladder or lung – Bones – Bony scales – Fin rays
2 major groups• Subclass Chondrostei • Subclass Neopterygii – Heterocercal tail – Homocercal tails – Skeleton made mostly of • Backbone does not cartilage extend into tail – Ganoid scales – Cycloid OR Ctenoid • Armored appearance scales • Florida Gar • Both are thinner and more flexible than ganoid scales
Body Shapes-determined by habitat• Fusiform- streamlined shape for active swimmers• Laterally compressed- flattened so can maneuver though corals• Flattened: bottom- dwellers• snakelike: burrowing fish
Respiration• Gills: receive oxygen and remove CO2, and maintain salt balance – Made of gill filaments: blood flows in opposite direction of incoming H2O• Water must continuously pass over gills – Meets with blood with lower O2 and higher CO2 • Diffusion moves from where to where????? – Fish actually “pump” H2O over gills
Cardiovascular• Close circulatory system: Heart, veins, arteries – Most complex we’ve seen so far! – 4 chambered heart • Draw diagram in your notes• What does it mean to have an open circulatory system?
Muscle Contractions• W shaped bands of muscle• Movement occurs when muscle contracts. – Alternate from one side to the other – Starts at anterior and travels to posterior end• Contractions start at different areas in the body for different fish = different swimming patterns.
Staying neutrally bouyant• Buoyancy – Swim bladder: gas filled sac; add and remove to adjust buoyancy • SCUBA divers must adjust air in BCD for same purpose – To go down: let air/gas out – To go up: add air/gas
Fish Coloration5 important types you need to know
Important to fish survival• Help the fish to – Find food – Communicate – Attract mates – Defend itself from predators – Recognize species – Conceal themselves• Pigments: found in cells called chromatophores
Different types• 1. Structural colors – Produced by light reflecting from crystals located on chromatophores• 2. Obliterative Countershading – Found on fish living in pelagic zone (open ocean) – Dark on the top and white on the bottom – Why?
More types..• 3. Disruptive Coloration – Distract predator – Lines, stripes, fake eyes • Trying to aim predator in the wrong direction• Cryptic Coloration – Sneaky – Use colors to ambush prey• Poster Colors – Bright, showy colors that advertise territorial ownership or sexual displays
Nervous System• Brain, spinal cord, nerves• Senses – Olfaction: sense of smell: olfactory pits (nostrils) – Taste: receptors on head, jaws, tongue, mouth and barbels on some fish (catfish) – Hearing: internal ears – Sight: Eyes Lack eyelids • Most set on sides of face: each eye see own independent view.• Lateral Line: Detect movement in water
• Vast: depends on species Reproduction – Internal and external sexual reproduction – Some care and protect young, others do not• Perch: separate sexes – Males and females spawn eggs – Early spring in sandy, shallow sediments – Females lay more than 20,000 eggs at a time; male comes afterward to fertilize