BIO 370 - Exam 1 - Adaptations to Aquatic Life Flashcards
Describe how aquatic animals obtain oxygen.
Aquatic vertebrates have external or internal gills. Internal gills consist of primary lamellae (sometimes known as gill filaments) attached to the walls of gill pouches in hagfishes and lampreys and to gill arches in other fishes.
In teleosts, the gills separate the buccopharyngeal cavity (= the oral cavity and pharynx) from the opercular cavity. On each side of the head, the opercular cavity is covered by an operculum (plural, opercula) composed of bones and associated soft tissues.
Flow of water across the gills is unidirectional.
As water leaves the buccopharyngeal cavity, it passes over primary lamellae. Gas exchange takes place at the secondary lamellae
Types of Pumping
Buccopharyngeal pumping: pumping action of the mouth and pharyngeal region that creates a positive pressure across the gills
Ram ventilation: creating a respiratory current by swimming with their mouth open
Slide 6 - countercurrent exchange in gills of a teleost.
The arrangement of blood vessels in gills maximizes oxygen exchange. Each primary lamella has two vessels: an afferent lamellar artery running from the gill arch to the tip, and an efferent lamellar artery returning blood to the arch. Each secondary lamella connects the afferent and efferent lamellar arteries. The direction of blood flow through the secondary lamellae is opposite to the direction of water flow. This arrangement, known as countercurrent exchange, assures that as much oxygen as possible diffuses from water into blood.
Countercurrent flow maintains a difference in oxygen concentration (a diffusion gradient) between the water and the blood along the full length of a secondary lamella, resulting in a high oxygen concentration (90%) in blood leaving the gills.
Describe how aquatic animals adjust their buoyancy in water.
Holding a bubble of air inside the body changes the buoyancy of an aquatic vertebrate, and bony fishes use lungs and gas bladders to regulate their position in the water. Air-breathing aquatic tetrapods (whales, dolphins, seals, and penguins, for example) can adjust their buoyancy by altering the volume of air in their lungs when they dive.
Gas Bladder
sac containing gas that helps regulate buoyancy.
Types of Gas Bladders
Physostomous: connection between gas bladder and intestine to regulate volume by adding gas when they swim down and removing gas when they swim up
Physoclistous: increase volume of gas bladder by secreting gas from the blood into the bladder and decrease volume by absorbing gas from the bladder and releasing it into the gills
Slide 12 - gas bladders of teleosts.
Neutral buoyancy produced by a gas bladder works as long as a fish remains at one depth, but if it swims vertically up or down, the surrounding water exerts hydrostatic pressure on the bladder, which in turn changes the bladder’s volume. Water pressure increases as a fish dives deeper, compressing the gas bladder and reducing buoyancy. When the fish swims toward the surface, water pressure decreases, the gas bladder expands, and the fish becomes more buoyant. Thus, to maintain neutral buoyancy, a fish adjusts the volume of gas in its bladder as it changes depth.
The Bohr effect reduces hemoglobin’s affinity for oxygen when pH is low (Figure 4.4C).
The Root effect, a property of teleost hemoglobin, not only reduces hemoglobin’s affinity for oxygen at low pH, but also reduces the maximum amount of oxygen that hemoglobin can bind
Describe sensory systems in aquatic animals.
Lateral line system senses vibrations in the water.
Vision
Largely supplemented by other senses
Retinas differ between aquatic and terrestrial vertebrates to make up for difference in refraction.
Fishes have spherical lenses with high refractive indices. The entire lens is moved toward or away from the retina to focus images of objects at different distances from the fish. Terrestrial vertebrates have flatter lenses, and in birds and mammals, muscles in the eye change the shape of the lens to focus images, rather than moving the entire lens forward and backward as in fishes.
Slide 16 - Chemosensation: olfaction and taste
Sea lampreys have a single median nostril on top of the head that leads to the nasal sac and ends blindly in the nasohypophyseal pouch.
Jawed fishes such as eels have paired nasal sacs. Associated with each nasal sac is an anterior (incurrent) and posterior (excurrent) nostril. Thus, on each side of the head, water flows into the incurrent nostril, over the olfactory epithelium in the nasal sac, and out through the excurrent nostril.
Slide 17 - Detecting water displacement
Gnathostomes have a series of canals on the head (cranial or cephalic canals) and a trunk canal (or canals) that pass along each side of the body to the tail.
This receptor system is the lateral line system.
Hearing and Equilibrium
3 semicircular canals
In fish without gas bladders, sound travels through tissues of the skin and skull to reach the inner ear.
In fish with gas bladders, sound travels through tissues to the gas bladder, which then vibrates to the inner ear.
Types of Electroreception
Passive electroreception: ability to detect weak electric fields generated by muscle contractions of aquatic prey.Animals with passive electroreceptive abilities detect prey using electroreceptors called ampullary organs, or ampullae.
Passive electroreception is universal among chondrichthyans
Active electroreception: electric organs generate an electrical discharge
Describe how aquatic animals maintain a stable internal environment.
Water is more stable than air is from a temperature perspective.
Body temperature: Reactions in a metabolic pathway usually have different temperature sensitivities, so a change in temperature can mean that too much or too little substrate is produced to sustain the next reaction in the pathway.Heat flows out of the body if an animal is warmer than the surrounding water and into the body if the animal is cooler.
Nitrogenous wastes: Most nitrogenous waste comes from the breakdown of proteins. When protein is metabolized, nitrogen is enzymatically reduced to ammonia through a process called deamination.
Osmoregulation: refers to the process of maintaining both water and salt balance to prevent body fluids from becoming too concentrated or too dilute.
Excretion of Nitrogenous Waste
Ammonotely: excretion of ammonia through skin and gills as well as urine produced by the kidneys with no metabolic energy required (most bony fishes)
Ureotely: urea synthesized from ammonia in the liver, which requires more energy but produces a less toxic substance and can be concentrated in urine (amphibians can switch to this in times of dehydration)
Osmoregulation
the process of maintaining both water and salt balance to prevent body fluids from becoming to concentrated or too dilute.
Slide 25 - osmoregulation and excretion by marine and freshwater fish.
Cartilaginous fishes minimize osmotic flow by maintaining internal concentration of their body fluids close to that of seawater. To do this, they retain nitrogen-containing compounds, primarily urea and trimethylamine oxide (TMAO), that increase blood osmolality.
To compensate for osmotic dehydration, marine teleosts do something unusual: they drink seawater.
Ancanphobians – well developed paired fins, spines – anterior to each – dermal bone in skull, partly ossified skeletons, precursor to sharks (sharks do not have bony skins).
