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Behavioral Plasticity in Cichlids

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1 Behavioral Plasticity in Cichlids
A dominant male cichlid fish courts and breeds with females, and confronts other males – dominance is indicated by bright coloration and a dark eye bar A subordinate male cichlid flees dominant males, does not court or breed, and has a drab coloration Removal of a dominant male initiates cascade of changes in gene expression in a subordinate male that rapidly transforms its behavioral and physical phenotype to dominant

2 Dominant Male Cichlids

3 Epigenetic Effects Epigenetic mechanisms cause heritable changes in behavior without altering DNA sequence Example: Lack of tactile stimulation early in a female rat’s life causes methylation of its DNA, resulting in changes in gene expression that suppress oxytocin’s effects The methylated DNA is passed on from generation to generation, disrupting oxytocin’s influence and negatively affecting female parental behavior

4 Take-Home Message: How does the environment affect behavior?
With behavioral plasticity, environmental factors influence an individual’s behavior during its lifetime. The environment can also cause heritable changes in behavior through epigenetic modifications of DNA.

5 43.5 Movements and Navigation
All animals are motile during some part of their life cycle An innate directional response is called a taxis Example: Planarians are negatively phototactic and positively geotactic Kinesis is a response that causes an animal to increase or decrease its movements without regard for direction Example: Planarians are photokinetic

6 Migration During a migration, an animal interrupts its daily pattern of activity to travel in a persistent manner toward a new habitat Migration most often involves seasonal movement to and from a breeding site Some animals (e.g. birds) migrate every year; others (e.g. eels) migrate only once to spawn and die

7 Navigation and Migration
Some animals have an innate magnetic compass – they use variations in Earth’s magnetic field to determine direction Example: A European robin “sees” directional differences in Earth’s magnetic field with its right eye Some animals navigate by the sun and stars A migrating animal may gauge its progress relative Earth’s magnetic field, or to visual or olfactory landmarks

8 Vision-based Magnetic Compass in European Robins
Figure Vision-based magnetic compass in European robins. (a) Triangles indicate predominant direction of movements made by 12 robins tested indoors in the spring. Arrow indicates average result. (b) A robin with a frosted lens in front of its right eye and a clear one over its left eye shows no directional preference in its movements.

9 Take-Home Message: What factors influence animal movements?
Innate responses to specific stimuli can influence the rate or direction of animal movements. Some animals migrate between habitats. Navigating to a specific site requires an ability to determine compass direction and a mental map.

10 43.6 Communication Signals
Communication signals transmit information between members of the same species Chemical signals such as bee pheromones Acoustical signals such as prairie dog barking Visual signals such as threat displays Tactile signals such as honeybee dances Bird courtship often involves both visual and acoustic signals

11 Prairie Dog Barking a Warning
Figure Prairie dog barking a warning. The bark provides information about whether the threat is an eagle or coyote. Other prairie dogs that hear the alarm call behave accordingly, diving into burrows when the call warns of a flying predator, or standing erect to observe the movements of a ground predator such a coyote.

12 Courtship Display in Albatrosses
Figure Courtship display in albatrosses. The display involves a series of movements, some accompanied by calls.

13 Threat Display: Male Collared Lizard
Figure Threat display of a male collared lizard. This display allows two rival males to assess one another’s strengths without engaging in a potentially damaging fight. The display also is called into service to deter potential predators.

14 Tactile Display: Honeybee Dances
When bee moves straight up comb, recruits fly straight toward the sun. When bee moves straight down comb, recruits fly to source directly away from the sun. When bee moves to right of vertical, recruits fly at 90° angle to right of the sun. Figure Animated Honeybee waggle dance, a tactile display. The orientation of the “waggle run” conveys information about the direction of a food source. Stepped Art

15 ANIMATED FIGURE: Honeybee dances
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16 Communication Chemical and acoustical signals typically are effective over longer distances than visual or tactile ones – also, they are more effective in the dark The same signal may function in more than one context Example: In dogs and wolves, a play bow indicates that any seemingly aggressive signals that follow, such as growling, should be interpreted as play behavior

17 A Wolf’s Play Bow Figure A wolf’s play bow tells another wolf that its next behavior is meant as play, not aggression.

18 Eavesdroppers and Counterfeiters
Predators can benefit by intercepting signals sent by their prey Example: Frog-eating bats locate male tungara frogs by listening for their mating calls Counterfeit signalers can also pose a threat Example: A predatory beetle imitates the flash of a female firefly to lure a male firefly close enough to eat him

19 Take-Home Message: What are the benefits and costs of communication signals?
A communication signal transfers information from one individual to another individual of the same species. Such signals benefit both the signaler and the receiver. Signals have a potential cost. Some individuals of a different species benefit by intercepting signals or by mimicking them.

20 43.7 Mates, Offspring, and Reproductive Success
Males and females behave in ways that maximize their own reproductive success Males compete for females and seek many mates Females select for quality of a mate, not quantity Microevolutionary process favor characteristics that provide an advantage in obtaining and keeping mates

21 Mating Systems Promiscuity: Members of both sexes mate with multiple partners Polygamy: One sex has multiple partners Monogamy: A male and female mate only with one another Members of a species may vary in their behavior, and formation of pair bonds does not preclude extrapair matings

22 Sexual Selection When one sex is the limiting factor for the other’s reproduction, sexual selection occurs Examples: Female hangingflies mate only with males that supply food Female fiddler crabs judge a male’s burrow-building skill before selecting a mate Male sage grouse display at a lek to be chosen by females Male bison fight to hold a territory with access to females

23 Male Hangingfly Bearing Food
Figure How to impress a choosy female. A. Male hangingfly dangling a moth as a nuptial gift for a potential mate.

24 Male Fiddler Crab with Large Claw
Figure How to impress a choosy female. B. Male fiddler crabs (top) wave their one enlarged claw to a attract a female (bottom).

25 Male Sage Grouse at a Lek
Figure How to impress a choosy female. C. Male sage grouse gather on a communal display ground called a lek, where they dance, puff out their neck, and make booming calls.

26 Male Bison Defending Territory
Figure Male bison locked in combat during the breeding season. A few males will mate with many females. Some males will not mate at all.

27 Parental Care Parenting requires time and energy
Increase in survival of young may outweigh costs Examples: In mammals, females are typically sole caregivers Male midwife toad cares for eggs Cooperative care of young by both parents occurs most frequently in birds

28 Female as Sole Caregiver
Figure Caring for offspring. A. Female grizzlies care for their cub for as long as two years. The male takes no part in its upbringing.

29 A Male Caregiver Figure 43.19 Caring for offspring.
B. A male midwife toad carries developing eggs.

30 Cooperative Care Figure 43.19 Caring for offspring.
C. A pair of Caspian terns cooperate in caring for their chick.

31 Take-Home Message: What factors affect mating systems and parental care?
The positive effects of genetic diversity among offspring make monogamy rare. In many species, a few males monopolize mating opportunities either by enticing females to choose them or by defending a territory with many females. Parental care evolves only when the benefit of parental care outweighs the costs in lost opportunity for more offspring.

32 43.8 Living in Groups Animals that live in social groups may benefit by cooperating in predator detection, defense, and rearing the young Such groupings evolve only if benefits of close proximity to others outweigh the costs

33 Defense Against Predators
In some groups, cooperative responses to predators reduce the net risk to all Alarm calls (e.g. birds, monkeys) Presenting a united front (e.g. sawfly caterpillars) A selfish herd forms when animals hide behind one another to avoid predators

34 Group Defenses: Sawfly Caterpillars
Figure Group defenses. A. Cluster of sawfly caterpillars regurgitating fluid (yellow) that predators find unappealing.

35 Group Defenses: Musk Oxen
Figure Group defenses. B. When threatened, musk oxen adults (Ovibos moschatus) form a ring of horns, often around their young.

36 Improved Opportunities
Many mammals live in social groups and cooperate in hunts, but cooperative hunters are not always more successful than solitary ones Groups are more successful at fending off scavengers, caring for young, protecting territory Group living also allows transmission of cultural traits, or behaviors learned by imitation, such as termite “fishing” among chimpanzees

37 Cooperative Hunting in Wolf Packs
Figure Members of a wolf pack hunt cooperatively.

38 Chimpanzees Fishing for Termites
Figure Chimpanzees (Pan troglodytes) using sticks as tools for extracting tasty termites from a nest. This behavior is learned by imitation.

39 Dominance Hierarchies
Many animals that live in permanent groups form a dominance hierarchy Dominant animals get a greater share of resources and breeding opportunities than subordinate ones Example: Wolves cooperate in hunting, caring for young and defending territory, but only the alpha male and alpha female breed

40 Regarding the Costs In most habitats, the costs of living in large groups outweigh the benefits Large groups attract predators Increased competition for space and food Increased vulnerability to disease and parasites Risk of being killed or exploited by others Example: Penguins form dense breeding colonies in which competition for space and food is intense

41 Penguin Breeding Colony
Figure A crowded penguin breeding colony.

42 Take-Home Message: Benefits and costs of living in a social group
Living in a social group can provide benefits, as through improved defenses, shared care of offspring, and greater access to food. Costs of group living include increased competition and increased vulnerability to infections.

43 43.9 Why Sacrifice Yourself?
Extreme cases of sterility and self-sacrifice have evolved in only a few groups Insects such as honeybees, termites, and ants Two species of mammals (mole-rats)

44 Eusocial Animals A eusocial animal lives in a multigenerational family group with a reproductive division of labor Permanently sterile workers care cooperatively for the offspring of just a few breeding individuals In some species, sterile workers are highly specialized in form and function

45 Specialized Workers: Honeypot Ant
Figure Specialized ways of serving and defending the colony. A. An Australian honey pot ant worker. This sterile female is a living storage container.

46 Specialized Workers: Soldier Ant
Figure Specialized ways of serving and defending the colony. B. Army ant soldier (Eciton), also a sterile female, shows her formidable mandibles.

47 Specialized Workers: Soldier Termite
Figure Specialized ways of serving and defending the colony. C. Eyeless soldier termite (Nasutitermes). It shoots glue like secretions from its nozzle-shaped head. Termite soldiers include both males and females.

48 Honeybees Queen honeybee
The only fertile female in her hive; she secretes a pheromone that makes all other females sterile Worker bees Females that develop from fertilized eggs; they collect food and maintain the hive Drones Stingless males that develop from unfertilized eggs; they mate with a virgin queen and die

49 Termites Termites live in huge family groups with a queen who specializes in egg production – a king supplies sperm Unlike the honeybee hive, a termite mound holds sterile males and females Winged reproductive termites of both sexes develop seasonally

50 Mole-Rats Mole-rats are the only eusocial mammals
A reproductive mole-rat queen mates with one to three kings Their nonbreeding worker offspring feed the clan, dig burrows, and protect against predators

51 Queen Honeybee Figure Three queens, fertile females in species that have a reproductive division of labor. A. Queen honeybee with her sterile daughters.

52 Queen Termite Figure Three queens, fertile females in species that have a reproductive division of labor. B. A queen termite dwarfs her offspring and mate. Ovaries fill her enormous abdomen.

53 Queen Naked Mole-Rat Figure Three queens, fertile females in species that have a reproductive division of labor. C. Naked mole-rat queen.

54 Evolution of Altruism Altruistic behavior
Behavior that enhances another individual’s reproductive success at the altruist’s expense Theory of inclusive fitness Altruistic behavior is perpetuated because altruistic individuals share genes with their reproducing relatives

55 Take-Home Message: How can altruistic behavior be selectively advantageous?
Altruistic behavior may be favored when individuals pass on genes indirectly, by helping relatives survive and reproduce. Mechanisms that increase relatedness among siblings may encourage the evolution of eusocial behavior.

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