BIOLOGY OF FISHES
Fall 2001
Exam # 1 - KEY
Tuesday 25 October 2001.
If you feel there was a problem with the way your exam was graded you may ask for a re-grade. Requests will be honored ONLY if a request is submitted IN WRITING within 1 week from the return of exams in class. To request a re-grade, include your original exam and a scientific explanation of why your answer is correct. Re-grade requests will not be accepted via e-mail. If you plan to submit a re-grade request, this must be done before you discuss the test with the instructor.
ANSWER FIVE (5) OF THE FOLLOWING TEN QUESTIONS. DRAW AN "X" THROUGH THE QUESTIONS YOU CHOOSE NOT TO ANSWER.
A1) (5 points) Did you hand in the two questions on the first part of the course. If "yes" receive full points. If "no" (or an incorrect "yes") receive none.
A2) (5 points) What is a fish?
A fish is a member of a paraphyletic group (a subset) of vertebrates, united by evolution in water (i.e. no terrestrial stage) with traits representing solutions to the properties of this medium.
A3) (5 points) An analysis of publications on resource use by fishes found resource partitioning along the trophic axis was most important. Do you agree that resource partitioning along the food axis is most important in explaining habitat distributions of fishes? Give your reasoning.
Tradition sampling methods for collecting fish have used gear that is large relative to fishes and their habitats. As a result, discrimination of fish locations and physical habitat use has not been very effective. (This is beginning to change with underwater TV, SCUBA, and snorkeling). In contrast, numerous studies have examined feeding, especially from stomach analysis. Therefore, the conclusion that fish tend to emphasize resource partitioning along the food axis reflects methods rather than actual habitat uses.
A4) (5 points) Draw a cladogram to show the sequence of appearance of the following Great Lakes fishes: bowfin (Amia), pike (Esox), the mooneye (Hiodon), and smallmouth bass (Micropterus).
A5) (5 points) Would you expect an aestivating (over-summering) lungfish to be ammoniotelic of ureotelic? Explain your answer.
Urea is less toxic than ammonia and hence requires less water for its excretion. Urea is a common nitrogenous waste product in xeric (limited water) situations. Aestivating lungfishes bury themselves in the substratum sometimes in a mucus sheath, to survive summer conditions of high temperature and limited water. Therefore, aestivating lungfishes are in a xeric situation and are more likely to be ureotelic than ammoniotelic.
A6) (5 points) Why is it postulated that osteichthyan fishes arose in tropical freshwaters?
An apomorphy of the Osteichyes is the presence of a lung, an adaptation to access atmospheric oxygen, implying that oxygen availability in the water was reduced. Hypoxia - reduced water oxygen availability characteristically occurs in warm water, often also shallow, and swampy where biological oxygen demand to decompose materials adds to the oxygen reduction due to temperature. Such waters may also dry out, eliminating the water oxygen supply.
A7) (5 points) Why do so many fish use a double pump for ventilation?
Water is dense, and large amounts of energy are needed for its acceleration. Water also contains relatively little dissolved oxygen. A double pump, with major components working out of phase largely accelerates the water and keeps it moving across the gills with minimal changes in speed. A continuous flow of water also helps ensure high water pO2 at the secondary lamellae.
A8) (5 points) Why does shark blood lack a Root shift?
The Root shift is associated with gas secretion into the swimbladder, choroid retia etc. These are absent from sharks.
A9) (5 points) What is the functional importance of evolution of the branchiostegal apparatus?
The branchiostegal apparatus consists of dermal bones and muscle that not only acts as a valve preventing influx through the opercular slits when the opercular pump is dominant, but also can actively expand to increase opercular volume. As a result, the opercular pump is more powerful, which especially facilitates suction feeding.
A10) (5 points) Over 90% of the world’s water is saltwater, but 41% of fish species are found in freshwater. Explain the basis for this observation.
On average (excluding coral reefs etc.) freshwaters are approximately 5 times more productive and have approximately 8 times the biomass per unit volume than marine systems. In addition, freshwater systems are on average more complex in structure, with numerous possibilities for populations isolation and hence (allopatric) speciation.
ANSWER FIVE (5) OF THE FOLLOWING EIGHT QUESTIONS. DRAW AN "X" THROUGH THE QUESTIONS YOU CHOOSE NOT TO ANSWER.
B1) (25 points) Briefly describe the zoogeographic and anthropogenic origins of the present Michigan ichthyofauna.
The Michigan fauna is speciose because of its proximity to the Mississippi drainage. This has been a major center for speciation in N. America. During the retreat of the glaciers, the Great Lakes regions had numerous meltwater connections with this system, providing a large number of avenues for immigration. Melt-water from the glaciers also created connections with the Arctic and with the Atlantic. Although young, some endemic species have already arisen, and human activity has added more.
B2) (25 points) On the accompanying diagram, there is a monophyletic clade which you are studying. On this figure, label the following:
Can you identify a single species that is most derived in the clade of interest? Explain your answer.
No. Either species c or d is most derived, by there is no information to show if species d is more derived – more recent – than species c.
B3) (25 points) Hemoglobin-less icefish live in Antarctic polar waters. From your knowledge of the principles of gas exchange, what adaptations do you anticipate in such fish in terms of gas exchange? Give your reasons.
Gas exchange can be modeled quantitatively. Basic models are modified Fick Equation for diffusion and for convective transport:
Diffusion: MO2 = k.S.D pO2/D
Convection: MO2 = VG.D [O2]water = Q.D [O2]blood
Expect low MO2 for a fish lacking hemoglobin because of the O2 delivery problems that will create.
At low water temperatures, more oxygen dissolves per unit volume of water. Therefore higher [O2]water and [O2]blood compensate to some extent for lack of hemoglobin. This permits D [O2]water and hence Q.D [O2]blood to be large.
The ventricle is large to Q large.
VG is not unusually high. Fish generally pass large volumes of water over the gills to ensure water pO2 does not fall over the gills. The high water pO2 and low metabolic rate are sufficient for blood oxygenation, and hence there is no need for icefish to differ from other species in this respect.
In principal, diffusion distance could be small and gill area large. These would be associated with larger ion and water exchanges as well. Higher capillary density (associated with higher blood volume) will reduce diffusion distances and increase exchange area in the tissues. Such modifications of metabolism and gas exchange apparently make changes is gill area and diffusions distance unnecessary.
B4) (25 points) How do flowing freshwater habitats vary in space and time? What affect does this have on the variety and types of species at various stages in the life of streams and rivers?
The stream channel changes along stream length and because flowing water is always eroding, stream channels change with time. Younger streams may be torrential with a very steep slope, >1/75 km/km. Few fishes, mainly herbivores feeding on diatoms and algae encrusting rocks and boulders, are able to persist. In space and time, subsequent changes can be summarized as:
|
brook |
creek |
river |
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steep gradient <1/75 km/km >1/20 km/km |
less steep » 1/20 km/km. |
lower gradient |
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|
riffles and torrents cool high oxygen |
riffles and pools |
Middle reaches with more pools than riffles. Runs more common. Lower reaches with meandering, stream bed and sluggish flow. Warm, less oxygen |
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Few species - "torrential" fauna. |
salmonids, cottids. |
More species. grayling, dace, chub, darters, and suckers. |
shiners, minnows, and dace. |
Most species. suckers, bullheads and catfishes, various cyprinids, pike, centrarchids. |
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B5) (25 points) How do cartilage and bone differ in mechanical properties? What are the consequences for fin form and function?
Cartilage and bone can approach similar compressive strengths, for, like reinforced concrete, this depends more on the properties of inclusions than on the properties of the matrix. However, cartilage is weak in bending. The greater bending strength of bone allows fairly slender structures (lepidotrichia) to support bony fins whereas ceratotrichia tend to be large and bulky. Consequently, the fins of elasmobranchs are relative bulky compared to bony fish fins. As a result, elasmobranch fins lack the mobility of bony fish fins. This makes slow swimming and hovering difficult - essentially impossible - excluding elasmobranch from many habitats with dense structures, and behaviors requiring precise low-speed maneuverability.
B6) (25 points) Explain why seawater is a major barrier to dispersion for freshwater fishes.
This relates to the major physiological problem of ionosmoregulation. Water and ion levels must ge kept wiuthin narrow limitis in which macromolecules can function effectively. Few, perhaps no fish is truly euryhaline, and able to survive full freshwater and full seawater. Adaptations to seawater or to freshwater are associated with major changes in biochemistry, physiology, anatomy, behavior and control systems. The adaptations associated with various radiations into new ion/water environments appear to be irreversible. Successive radiations find different solutions, often dictate by losses/changes from previous radiations. Thus saltwater is typically a barrier to freshwater dispersants, while freshwater is a barrier to marine fishes.
B7) (25 points) Compare and contrast cladistics and phenetics.
Cladistics assumes shared features (homologies) manifest hierarchical patterns because all organisms are derived from others (descent with modification leading to clades). Resulting delimitable monophyletic units (clades) can be identified only in terms of new (derived) characteristics (evolutionary innovations). Symplesiomorphies are of no use in inferring relationships within a clade. Cladograms are, however, polarized using a less-derived outgroup sharing plesiomorphic characters with a clade of interest. Pattern is expressed as a dichotomous branching diagram, a cladogram of equal status sister groups. Nodes represent speciation events. There are no intermediates nor "ancestors". Choices among possible cladograms are made on the basis of parsimony.
Phenetics (numerical taxonomy) starts with species as operational taxonomic units (OTUs) and clusters these on the basis of overall similarity using both derived and shared characteristics. Advocates believe that the more characters used, the more natural will be the classification. In general, this leads to the identification of life-form groups that are expressed as phenograms or the "traditional" classification of Kingdoms, Phyla, Classes etc.
B8) (25 points) You have undoubtedly put a lot of time and effort into learning some part of the material for this exam for which no question has been asked. Write an exam question based on the material for the course to date, and write the answer for your question that should go on an exam key.
Questions from 2001 Class - i.e. you - on the first part of the class
And more questions to help direct your studies:
Ideas for exam questions based on suggestions from students in previous years
What mechanisms are involved in coughing? How have these been modified for inflation by pufferfish? Explain the function of other adaptations of pufferfish associated with inflation.
Explain the circumstances under which cutaneous gas exchange is important for fish.
Explain why larvae have low rates of branchial ventilation than juveniles and adults, in spite of their small size.
Why do fish use a double pump for ventilation?
What is ram ventilation? How can the use of ram ventilation ameliorate the increase in metabolic rate with exercise seen in fish that use branchial ventilation?
What premises underlie the double pump concept for fish ventilation? Do you think the data are adequate to support the concept?
Why do aquatic animals such as fishes often use two pumps to ventilate their gills?
Increasing oxygen uptake involves various physiological adjustments in the gas exchange system, including increased secondary lamellar perfusion with blood. Why do they avoid if possible increasing blood pressure to increase perfusion of the secondary lamellae?
Hemoglobin-less icefish live in Antarctic polar waters. This question addresses the problem of how these fish are able to meet metabolic requirements in the absence of hemoglobin using principles discussed in class. Explain the importance of each characteristic of the habitat or the fish in matching metabolic needs and supply.
Why doesn't shark blood show a Root effect?
Explain how the blood-oxygen dissociation curve differs between an active and a sluggish fish.
Explain how NTPs and pH affect the loading of oxygen by blood at the gills and delivery of oxygen to the tissues.
Explain the mechanisms whereby fish control plasma pH, and why an Na+/H+ exchange to independently control intracellualr red blood cell pH is necessary.
Why do elasmobranchs have a contractile conus arteriosus?
Explain how patterns in the evolution of the arterial system in air-breathing fish improve the separation of oxygenated from deoxygenated blood.
Explain why hydrodynamic lift forces are used most commonly by fish in controlling their position in the water column.
Discuss the relative merits of hydrodynamic lift and gas for buoyancy regulation in surface living pelagic fishes?
Explain how use of hydrodynamic lift and gas bladders for buoyancy regulation affect the choice of habitats by fishes.
Why do perch living in shallow water tend to stay within a narrow range of depths?
And a problem to try: A salmon, with a total body mass of 100 gm migrates from freshwater to seawater. The mean density of its fat-free tissues remains constant at 1.080 gm.cm-3. Ten percent (10%) of its body mass is comprised of fats with a mean density of 0.830 gm.cm-3. Calculate the swimbladder volume necessary to achieve neutral buoyancy in freshwater and seawater. What change in swimbladder volume is required to maintain neutral buoyancy in both freshwater (density 1.000 gm.cm-3) and seawater (density 1.025 gm.cm-3)? Show your working.
How does the fin and muscle morphology of pike and tuna differ? Explain how these differences affect life styles.
What mechanisms are used for producing thrust? Explain how morphologies to maximize these thrust forces differ?
Compare and contrast optimal morphologies for thrust maximization of a lift-based and a resistance-based propulsor.
Explain how body and fin undulations generate thrust. Explain how variations in undulatory propulsors affect the magnitude of thrust and efficiency.
What muscle, propulsor and locomotor behaviors are found in pelagic predators, a trout swimming upstream, etc. Explain your answer.
What muscle, propulsor and locomotor behaviors would you expect to minimize energy consumption of a fish living in a large, open water body? Give your reasons.
What are the advantages of using gas inclusions (or lipids, or hydrodynamic lift) to regulate altitude? Give your reasons.
Suppose you are a fish that spends the daytime at the bottom of a lake. At night you migrate to the surface to feed. What mechanism for generating lift do you think you would use? Give your reasons.
How can "drag" both facilitate and impede locomotion?
What locomotor and feeding adaptation might you expect of a river fish that exploits annual flooding of adjacent forest? Give your reasons.
What factors affect food choice in fishes?
What locomotor, feeding, and behavioral strategies are used by fish to capture prey in open waters? Give your reasons.
The various steps involved in feeding by generalized carnivores acne be described by the multistep foraging cycle. Describe the generalized feeding cycle. Can fish optimize all steps simultaneously? Give your reasons.
Explain how various events during ontogeny affect locomotor gaits in fishes.
What locomotor and feeding adaptations would you expect in a fish living in a small, weedy pond containing evasive and dispersed prey. Give your reasons.
Why has a generalized fish such as a bass not evolved into a better accelerator, when this would seem desirable to better capture its prey?
Explain why a fish changes diet during ontogeny.
What energetic advantages might accrue to the transporter linking of ion regulation, pH regulation, and nitrogen excretion?
What arguments are advanced to suggest that mechanisms for ionosmoregulatory in marine fish proved to be pre-adaptations for freshwater life?
Imagine a salmon starting its run from the Pacific Ocean up coastal rivers to its spawning grounds. What ionosmoregulatory problems will the fish experience as it passes from seawater to freshwater? Explain the mechanisms used in these situations to regulate ions and water?
Explain the role of active transport in the regulation of (a) sodium, (b) chloride and (c) water in a marine teleost.
When I was younger, I had many mishaps with my pet goldfishes. One day, I brought home a goldfish from the fun fair and dumped it into my friend's brother's seawater aquarium. At the time, I didn't understand why the fish died, but now with my knowledge of fish I know what happened to my poor fish. Explain how the arrangement of the Na+/K+-ATPase pump and Na-K-2Cl cotransporter distribution in the chloride cells of my goldfish would have prevented its successful ionosmoregulation in seawater.
Explain why extrarenal mechanisms are required for ionosmoregulation by fishes.
Explain the role of the second proximal tubule in adaptation by teleosts to seawater and to freshwater.
The general strategies for predators and for prey in predation interactions can be understood using game theory. What are the general principles for (a) predator success and (b) prey success? Give one example to tactics used to achieve success for a predator and for a prey.
Chases are rare by predatory fish. Explain why this is so, and why chases are more prevalent by acanthopterygian predators compared with malacopterygian predators.
If a sudden "hagfish polio" disease began killing these scavengers at a high rate, would it be possible to immunize them against the disease? Explain your answer.
Discuss the role of fish in the biological control of human disease.
What behaviors would you expect of an ambush predator detecting its prey from near-field effects its prey use to stalk? Explain your answer.
Coelacanths have a high concentration of urea and TMAO in their body fluids whereas other osteichthyans do not. Using your knowledge of fish systematics, develop an hypothesis to explain this observation.
What factors affect the susceptibility of fish to disease? What methods are especially effective for aquaculturists to minimize the risk of disease?
How would you expect the proportions of rods and cones to vary among the dominant species in a clear Michigan northern lake and a southern Michigan eutrophic lake? Explain your answer.
You are employed in a company designing fishing lures. You are trying to develop such a lure for walleye, typically found at low light intensity at depths of about 10 m. From your knowledge of the sensory systems of fishes, what features would you want to include in such a lure? (Size and cost no object).
How do fisheries directly and indirectly contribute to loss of fish diversity? What steps are necessary to alleviate these problems?
What problems stand in the way on valuing natural resources towards their conservation for present and future generations?
Discuss the reproductive strategy of a subordinate male in a breeding system dominated by a few large males. Explain how the subordinate ensures matings.
Little Bobby fish is 3 years old and can’t seem to get any females to mate with him. All the girls seem to prefer mating with the big guys in the neighborhood. What do you tell Bobby to do when he comes to you for advice on how to get matings?
This spring was long and cool. In July, I went fly fishing in Ontario, Canada, for smallmouth bass. All the locals were concerned about the effects of the spring on spawning and future populations. How would a late cool spring affect production of young bass, and what conditions might prove corrective? Give your reasons.
In spite of the small costs of producing sperm, sperm production may be limiting to reproductive success in fish. Explain the circumstances under which this can occur, and mechanisms used by fish to ameliorate the problems.
Explain how a curve describing population growth - the logistic growth curve - can lead to ideas on life history strategy (r-K continuum).
What are complex life cycles? Why do most fish have complex life cycles? What effect does this have on the useful of traditional r-K continuum approaches to life history strategy? Give your reasons.
Discuss the effect of density-independent factors on reproductive strategies of fishes.
Fish reproductive schedules are relatively plastic. Discuss three factors that push these towards the r-end of the r-K continuum.