sensory systems, behavior, reproduction biology of fishes 11.1.12
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Sensory Systems, Behavior, Reproduction Biology of Fishes 11.1.12. Overview. Presentations & Other Assignments Presentation Guidelines – online Friday Guest Lecture II – Fishes of the Great Lakes 11.8.2012 Syllabus Revisions Exam II – November 20 Upcoming Topics Sensory Systems Behavior - PowerPoint PPT PresentationTRANSCRIPT
Sensory Systems, Behavior, ReproductionBiology of Fishes
11.1.12
Presentations & Other Assignments Presentation Guidelines – online Friday Guest Lecture II – Fishes of the Great Lakes 11.8.2012
Syllabus Revisions Exam II – November 20 Upcoming Topics
Sensory Systems Behavior Reproduction
Overview
What fishes use to gather information about their environment
Accurate and up-to-date information about surrounding conditions
Critical to decision-making success in feeding, predator-avoidance, mate selection
Sensory Systems
Mechanoreception Involves detection of movement 2 major systems
Lateral line Inner ear Collectively referred to as the “acoustico-lateralis”
system
Sensory Systems
Lateral line Unique sense organ found in all fishes (except hagfish) and
some amphibians Adapted for life in aquatic environments Sensory system stimulated mechanically by motion
weak water currents hitting the body result in distinct fin movements
Local cauterization of lateral line results in no fin movements
Sensory Systems
Lateral line – Structure Basic unit that senses motion is the neuromast Neuromast consists of cupula – jelly-like substance and
sensory hair cells
Sensory Systems
Lateral line – Structure Basic unit that sense motion is the neuromast
Sensory Systems
Lateral line – Structure Basic unit that senses motion is the neuromast
Sensory Systems
Lateral line – Structure 2 types of neuromast
Superficial neuromast Located on surface, distributed on head and body Tend to be smaller and have fewer hair cells
Canal neuromasts Located in canals in head and along body (lateral line) Tend to be larger and have more hair cells
Sensory Systems
Lateral line – Structure Superficial neuromast Canal neuromasts
Sensory Systems
Lateral line – function Identify and locate stationary object Prey detection – (e.g. sculpin-zooplankton, pike-fishes, terrestrial
insects) Detect flow differences (maintaining position, prey detection – candiru
catfish) Communicate for spawning synchronization Synchronized swimming – schools (even blind fishes can school)
Sensory Systems
blind cave fish
Inner Ear Also used for mechanoreception Provides information on the orientation and movement of
a fish Critical for maintaining balance and position
Sensory Systems
Inner Ear – structure Semicircular canals
Filled with fluid (endolymph) Movement of the fish causes movement of fluid in semicircular
canals Enlarged area (ampulla) contains sensory hair cells that are
displaced by movement of fluid Movement of hair cells results in changes response of sensory
neurons – provides brain with information on changes in acceleration and orientation
Sensory Systems
Inner Ear – structure
Sensory Systems
Inner Ear – structure Otoliths
Ear “bones” or “stones” actually crystalline formation Provide information on orientation and movement Can be used in aging fishes
Sensory Systems
Inner Ear – structure Otoliths
Sensory Systems
Hearing Inner ear also responsible for hearing Most fish tissue transparent to sound – density of tissue is similar to
water Sound vibrations travel right through the fish Otoliths denser – vibrate for sound detection Otolith vibration sets hair cells in motion – changes response of
neurons
Sensory Systems
Hearing – Gas Bladder Also increases sensitivity to sound Sound waves cause vibrations in gas bladder – transmitted to inner ear Weberian apparatus (Otophysi) Clupeomorpha have extensions of gas bladder that lie next to inner
ear Other fishes – gas bladder lies close enough to increase sensitivity
Sensory Systems
Sum of all motor responses to all internal and external stimuli
Fishes exhibit a host of behaviors associated with feeding, predator-avoidance, reproduction, locomotion, interactions
Behaviors are plastic – vary with life stage, season, time of day, environment, perceived risks; also individuals, populations
Behavior
Dynamic displays – involve posturing Ways of communicating to one another – courtship, territory defense,
dominance, signaling to young Include visual displays – rapid change in color, exposure of colored
structures, mouth/gill flaring, fin flicking, raising fins
Behavior
Dynamic displays – involve posturing Lateral displays (cichlids, anemone fishes) Frontal displays (kissing gouramis, some cichlids) Communication via sound, chemicals (alarm substance), touch,
electricity
Behavior
Parental Care – association between parent and offspring after fertilization that enhances survivorship Increases survival by reducing predation risk, increasing food access Many fishes provide no parental care – egg dispersers, pelagic eggs Some parental care is common among fishes
Behavior
Taxon Male care Female care Both parents No care
Mammals 0 90 10 0
Birds 2 8 90 0
Non teleosts 6 66 0 28
Teleosts 11 7 4 78
% of families showing parental care
Unlike other vertebrates, males are most common care-giver in fishes Females invest +energy in egg production; guarding would reduce
amount of future reproduction Paternity assurance – makes sure only one is fertilizing eggs Tradeoff – costs energy and reduces fecundity
BehaviorTaxon Male care Female care Both parents No care
Mammals 0 90 10 0
Birds 2 8 90 0
Non teleosts 6 66 0 28
Teleosts 11 7 4 78
% of families showing parental care
Two types – behavioral or physiological Substrate guarding
Most common Male constructs nest; guards, fans, cleans eggs – may also guard young
(catfishes, minnows, sculpin, stickleback, bowfin, SA lungfish)
Mouth brooding Eggs and sometimes young carried in mouth (lumpfishes, gouramis, arowanas,
cichlids
External egg-carrying Eggs carried on lower lip, on head, or own belly (several catfishes)
Brood pouch Carried inside pouch of male – seahorses and pipefishes
Behavior - Parental Care
Behavior - Parental Care
The most obvious form of social behavior in fishes is the formation of groups
Shoals – unorganized grouping of fishes Similar to a flock of birds May gather together to feed, breed, or seek refuge (salmon, gars,
minnows) Basically “milling around”, no organized or coordinated swimming
Schools – synchronized swimming groups – exhibit coordinated behaviors One of the behaviors exhibited by fish in shoals In N. American literature “school is used to cover both shoaling
(unorganized) and schooling (organized)
Behavior
Schools – Why do they form? Fish act as individuals – don’t school for the benefit of the group
“selfish” – ensure access to food, minimize predation Hydrodynamic advantage – save energy by drafting – many studies,
but little solid evidence that fish save energy by schooling Most likely relate to foraging and predator avoidance Foraging
Find food faster Prey capture may be easier Hunting in packs (tuna, sailfish) Tradeoff – must compete with individuals of group
Behavior
Schools – Why do they form? Anti-predator strategy – the need to avoid predation is a major
selective force that shapes schooling behavior (takes precedence over finding a meal)
Evasion – attack success of predators declines with group size; most likely due to confusion of predator
Compaction – in presence of predator, group becomes more compact and cohesive
Detection – many eyes aid in predator detection Skittering – minnows detect predator and leap out of water then
return to school – may alert others in school, triggering anti-predator behavior
Predator inspection – fishes (usually small groups) approach predator
Behavior
Schools – Why do they form? Reproduction
Increases likelihood of finding a mate Coordinates readiness (maturity) through hormonal & behavioral
cues Facilitates arrival at spawning site at correct time (fish migrations –
salmon, whitefish, mullet)
Behavior
Fishes – most diverse group of vertebrates – incredibly diverse reproductive strategies/mechanisms
Reproductive strategies are adaptations to maximize the fitness of individuals – ensure genes are passed on
Overview of fish mating systems
Reproduction
Frequency of spawning Iteroparity (iteroparous)
More than one spawning during a lifetime Most fishes use this strategy K-selected species – grow slowly, reproduce late, produce fewer
young, longer life expectancy, lower reproductive effort (spread across time), may provide parental care
Stable, predictable habitats – survival to following year is high Lower fecundity, but spread out to ensure some reproduction ~25-60% of somatic energy used for reproduction
Reproduction
Frequency of spawning Semelparity (semelparous)
Spawn once and die Diadromous or highly migratory fishes tend to be semelparous
(salmon, lamprey, anguillid eels) R-selected species – grow fast, reproduce early, produce many
young, shorter life expectancy, high reproductive effort (“big bang”), no parental care
Unstable/unpredictable environments – high mortality Place eggs and young in ideal growing conditions Overwhelm predators ~60-85% somatic energy used for reproduction
Reproduction
Modes of spawning Oviparous – fish lay eggs that are fertilized externally, mother
provides no nutrition other than yolk (most fishes)
Ovoviviparous – eggs are retained in female and fertilized internally, mother provides no nutrition (most sharks, coelacanth, some poeciliids)
Viviparous – eggs retained in female, fertilized internally, mother provides nutrition (some sharks, goodeids, poeciliids)
Reproduction
Types of fertilization External
Most fishes Less time and energy spent in courtship Increase number of potential mates higher fecundity – more offspring produced
Internal Few groups of fishes Chondrichthyes, guppies, mollies Requires lengthy courtship Intromittent organ – transfer sperm to females (claspers, modified
anal fin)
Reproduction
Mating Systems Promiscuous – no obvious mate choice – both spawn with multiple
partners
Polygamy – only one sex has multiple partners Polyandry – one female, several males
Relatively uncommon Anemonefish, anglerfishes, gars
Polygyny – one male, multiple females Most common Territorial males care for eggs/young – visited by multiple
females (sculpins, sunfishes, darters, damselfishes some cichlids); harems may also form
Reproduction
Mating Systems Monogamy – fish mate exclusively with same individual
N.American freshwater catfishes, butterflyfishes, some cichlids, seahorses
Reproduction
Gender Systems – in most fishes the sex of an individual is determined at early stage and fixed; some fishes are hermaphrodites and can function as males and/or females Simultaneous – capable of releasing viable eggs and sperm
during same spawning Some can self-fertilize (Cyprinodontiform Rivulus); likely
adaptation to lower population size, isolated habitats Alternate sex roles during spawning (Serranus); male with harem
of hermaphrodite females – male removed, largest hermaphrodite female changes into male
Reproduction
Gender Systems – some fishes are hermaphrodites and can function as males and/or females Sequential – function as one sex for part of their life, then
switch Protogynous (protogyny) – start female, change to male; more
common Protandrous (protandry) – start male, change to female; less
common
Parthenogenetic – alternative to traditional gender roles All female but require sperm from other species to activate cell
division in eggs (genetic info from males is not conserved) Produce daughters genetically identical to mother (Poeciliidae in
TX and Mexico)
Reproduction