KEY .. KEY .. KEY .. KEY ..

Mean = 83 9. The result is curved add +3 to your percentage to obtain the result entered in the grade book.

Deadline for regrade requests is Tuesday December 4 in class.

BIOLOGY OF FISHES

Fall 2001

Exam # 2

Thursday 21 November 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 by Tuesday December 4 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) State two advantages of ammonia for excretion of nitrogenous wastes in water compared with urea.

(a) ammonia is highly soluble in water so that there are always concentration gradients facilitating diffusion from a fish.

(b) diffusion rates are high in water.

(c) readily ionized to the less toxic ammonium ion which diffused rapidly through lipids (e.g. cell membranes).

(d) there is no carbon loss with ammonia excretion.

(e) energy is not required for the synthesis of ammonia. Some deamination reactions generate ATP.

(f) ammonium can be exchanged with H+ or other cations for acid-base and/or ion regulation.

A2) (5 points) Explain why diadromous fishes are common in the freshwater ichthyofauna of geographically young regions. Give an example of a zoogeographic region where such fish dominate the fauna.

Geographically young regions start depauperate, with few species, and there is insufficient time for an endemic fauna to have arisen. Therefore, geographically young regions typically have open habitats.

Diadromous fish include marine and freshwater stages in their life cycles. The marine stages can cross saltwater to reach geographically young areas and then exploit the open freshwater habitat. Here they often have given rise to numerous non-migratory forms. If isolated, these may evolve into distinct species. e.g. Australasian ichthyofauna with many Salmonidae and Galaxiidae.

A3) (5 points) Describe the characteristics of the ventricle you would expect for an active fish. Give your reasons.

Large size to provide a larger amount of muscle to pump the blood. A well-developed compact layer, with attendant coronary blood supply to ensure high rates of oxygen delivery to sustain high power output from the cardiac muscle.

A4) (5 points) What characteristics of sharks make them vulnerable to overfishing?

The time to maturation is long, and fecundity low, so that production is low.

A5) (5 points) Which group of fish is defined by a fringing furcula, and what is the function of this apomorphy.

Actinopteri: strengthens the leading edge of the median fin, preventing collapse and hence facilitating high swimming speeds.

A6) (5 points) Given the features of mtDNA and nDNA, explain why many studies on phylogenetic systematics focus on mtDNA?

Mitochondrial DNA (mtDNA) has from 16,000 to 20,000 nucleotides, the majority of which encodes for protein product. There are high levels of sequence diversity despite great conservation of gene function and arrangement. In contrast, nuclear DNA (nDNA) has more than 3 billion repeated nucleotide sub-units, the majority of nDNA does not encode for protein products and therefore probably does not affect the fitness of individuals.

A7) (5 points) Explain why the bulk of marine habitats have low productivity and hence support small numbers of fishes.

Water rapidly absorbs light which is required for photosynthesis and hence primary production upon which food chains are based. Most of the ocean is below the photic. Production also requires nutrients. These are sparse in much of the ocean, but are found near shore lines where terrestrial nutrient flush into the sea and where there is upwelling to recycle nutrients that have fallen into the dark deeper zones.

A8) (5 points) Why doesn't a key for a group of fishes strictly follow systematic classifications?

Phylogenetics is based on analysis of many characters (meristic counts, morphological traits, etc.) that may be external, internal, embryological, occur at various life-history stages, for all relatives from all parts of the world. Analysis of material is often time-consuming, and requires sacrifice of animals.

Keys sort out local assemblages of organisms. They largely use simple external characters pertinent only to the local fauna. Many features used in keys are not homologies and are hence useless for cladistics.

A9) (5 points) What two conditions must be met to differentiate a territory from a home range?

Home range; the area through which an animal or group regularly travels during daily activities, but there may be a core area. Territory; an area occupied almost exclusively by one or more animals, by active repulsion of potential intruders through defense or advertisement. Therefore the two conditions are exclusive use and aggressive defense.

A10) (5 points) Explain why the majority of recognized endangered species are FW.

Almost all FW systems are degraded to some degree because freshwaters are essentially islands and ribbon of water surrounded by a sea of humans. Streams and rivers are the ultimate recipients of the by-products of human activity from sewage to sediment. Endangered species are most prevalent in regions with one or more of the following characteristics:

ANSWER THREE (3) OF THE FOLLOWING EIGHT QUESTIONS. DRAW AN "X" THROUGH THE QUESTIONS YOU CHOOSE NOT TO ANSWER.

B1 (25 points) The following are characteristics of a fish;

a) blood is hypo-osmotic to the surrounding medium.

b) large ventricle, mainly compact muscle, with coronary supply.

c) canine teeth.

d) interopercular ligament connects the hyoid and the interopercle bones.

e) streamlined body with lunate tail.

f) blood has low oxygen affinity.

Use this information to answer the following two questions. DO NOT list an explanation of the meaning of each character, but use the information and meanings as premises for your arguments. Use information to exclude options first.

B1- Part 1) Use this information to identify the general group to which the fish belongs; e.g. teleostome, agnathan, elasmobranch, malacopterygian (soft-rayed), acanthopterygian.

Since the blood is hypo-osmotic to the medium, this must be a marine fish. Elasmobranchs (also coelacanths) are marine but their blood is hyperosmotic compared to the water. Therefore, elasmobranchs are excluded and the fish is a teleostome. These fish also have an interopercular ligament connecting the hyoid and the interopercle bones. Therefore - some acanthopterygian fish. The body and caudal fin form is typical of tuna.

B1 Part 2) Use the information listed above (and only this information) to discuss the habits and habitat of the fish;

The fish is marine or estuarine since the blood is hypo-osmotic to the surrounding medium. Oxygenation is probably high because of the low oxygen affinity of the blood.

The streamlined body and lunate tail are typical of wide-ranging pelagic high-speed cruisers. The well developed heart muscle and coronary supply together with low blood-oxygen affinity facilitating oxygen delivery to the tissues are typical of active fish. The connection of the interopercular ligament to the hyoid and the interopercle bones is characteristic of fish with good jaw protrusion and suction feeding.

B2) (25 points) The following are characteristics of a fish;

a) high aspect ratio lunate tail.

b) blood is hyperosmotic to the medium.

c) excess monovalent salts diffusing into the blood are excreted extrarenally.

d) very low cellulase activity

e) very fine, long gill rakers.

f) viviparous.

Use this information to answer the following two questions. DO NOT list an explanation of the meaning of each character, but use the information and meanings as premises for your arguments. Recall that it is desirable to use information to exclude options first.

B2 Part 1) Use this information to identify the general group to which the fish belongs; e.g. teleostome, agnathan, elasmobranch, malacopterygian (soft-rayed), acanthopterygian.

Blood is hyperosmotic to the medium in all freshwater fishes and marine elasmobranchs. However, freshwater fishes must conserve ions. In contrast, marine elasmobranchs have lower ionic concentrations that the seawater since the osmolarity of the blood is make hyperosmotic to seawater through the retention of urea and trimethylamine oxide. Hence ions diffuse in to the body fluids form the water. These excess monovalent ions are excreted extrarenally. Therefore this animal is probably and elasmobranch. Additional (but non-definitive) supporting evidence is viviparity.

The fish has a high aspect ratio lunate tail, excluding rays which do not have deep caudal fins. Therefore this is a shark.

B2- Part 2) Use the information listed above (and only this information) to discuss the habits and habitat of the fish.

The high aspect ratio caudal fin is characteristic of cruising fish. Since maneuverability is reduced for such fish, they are typically found in extremely homogenous (i.e. pelagic) habitats. The very fine, long gill rakers are characteristic of a filter feeder, which is also associated with long periods of steady swimming. The very low cellulase activity suggests the fish is a carnivore.

As noted above, the ion-osmotic situation shows that this is a marine fish.

Therefore, this fish is a marine pelagic zooplantktivore cruiser.

B3) (25 points) Imagine that you are a fish, either a real fish or a hypothetical fish but nonetheless a fish ruled by the same biomechanical rules as a real fish.

a) Describe the habitat in which your fish lives and its swimming behaviors.

b) Complete a gait-expression map for your fish using the template below and explain the physical basis for the presence and absence of the gaits.

station holding

median and paired fin propulsors

body and caudal fin propulsors

SO

SO

FG

SO

FG

zero ground speed

hovering and slow swimming

twitch and coast

cruise

burst and coast

sprint

fast start

B4) (25 points) Why are two or more pigments required by fish to detect objects against a background spacelight that has a relatively constant color along any given line of sight, but which varies along different lines of sight?

Most fishes often need to see as far as possible through the water, which is achieved when pigments match background spacelight. Another requirement is to detect prey and predators against the background; i.e. detect contrast.

When match is good, dark objects, or low-photon sources, give largest contrast. Function of pigment mismatch - maximizes visual contrast for close, bright objects, a special but common case in well illuminated shallow water. Bright (light) objects are sources of higher densities of photons that background, and they will not be well differentiated from background spacelight. When there is pigment mismatch, dark objects and background appear dark, but contrast is large for bright objects. In mismatch situation, dark objects can still be distinguished in silhouette - such as viewing from below, taking advantage of typical differences in background spacelight in vertical and horizontal directions.

At greater depths, and for distant objects, the light from any object and the spacelight are increasingly similar - due to long pathlengths in both cases, and hence similar losses of similar wavelength for backlight and that reflected from objects. Then matched pigments are always superior - i.e. no examples of special (common) case of near bright objects.

B5) (25 points) The logistic growth equation, dN/dt = rN ([K - N]/K = rN(1 - N/K), describes the rates of changes in numbers of a population over time. Explain the corollaries (i.e. the related deducible features) that lead to this being used as the basis for the r-K continuum for reproductive strategies.

When a habitat is first occupied, and resources are not limited, dN/dt rN, or exponential growth. With time, population numbers increase so that resources become limiting. Then intraspecific competition and stress increase death rates and reduce birth rates until an equilibrium is reached with equal rates of birth and death. At this point, dN/dt 0, and population size is fixed at the carrying capacity, K, of the environment.

Since time is required to reach equilibrium, habitats in which resources are not limiting are typically those with higher risks and higher mortality due to predation or stochastic, density independent climatic effects. The probability of surviving over several years is low. Therefore, fish must breed at a young age, usually small size, and maximize effort. The opposite occurs in more stable environment, in which density dependent processes such as competition are dominant. Since growth rates vary along a continuum from risky to low risk situations, reproductive strategies have been dubbed r- and K-selected strategies.

B6) (25 points) The figure shows the energy consummation and routine metabolic rate for a sluggish, benthic species exposed to various levels of a pollutant. Draw in a line to show how you think growth rate would change with pollutant level. Then explain how you decided where to draw the growth-pollutant level curve.

How is the shape of the curve determined?

1) Principle of Conservation of Energy - all energy entering and leaving a system is accounted for. Leads to the Balanced Energy Equation:

pQration = Qmetabolism + Qgrowth (+ Qrepro).

2) Metabolic requirements are met first from physiologically useful energy. Therefore growth can occur only if there is surplus energy after meeting these needs.

3) All animal responses to the environment are ultimately met at the metabolic level. Therefore, for a given food intake, changes in growth vary inversely with changes in metabolism.

Second, how is the location of the curve decided relative to ration and metabolism?

4) Ration losses for fecal, nitrogenous and heat increment take about 35% of ration.

5) Growth is then the remainder after routine metabolism and these losses are taken into account.

B7) (25 points) The adjacent figure shows a schematic of linkages used for feeding by a teleostean. Show the primitive pathway for upper jaw opening, and the two derived pathways for lower jaw depression. Explain how suction and jaw protrusion are achieved.

Suction feeding involves depression of the floor of the mouth via the HY-pectoral girdle-SH-hyoid pathway, and expansion of the side of the mouth involving the AOP/LOP-opercular series. The branchiostegal system also improves expansion of the opercular cavity.

Jaw protrusion is achieved following freeing of the maxilla and subsequently the premaxilla, activated through the LAP/AM1-suspensorium-maxilla series.

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. Question MAY NOT ask solely for factual information. They must include conceptual aspects