freshwater streams pt 2 Flashcards
Freshwater streams
- Also in rivers/streams, the carbon cycle overlaps with terrestrial surroundings
- Leaves will enter the stream
- Some organisms have life stages in both
- Terrestrial animals will take prey from the stream and vice versa
- Animals waste/remains may enter the water
Freshwater animals as idnicators of envrinmental disruption
○ One third of all amphibian species are trheatened with extinction
○ Many amphibian species have narrow envrinmental tolerances and exchange gases thrpugh their skin, making them especially sesntive to envrinmental disruption
○ Amphibians are consiered the canaries in the gold mine for global envrinment bc of this - they tell us when things are wrong in the envrinment
○ Reason they are going extinct is bc of disease and exasterbated by loss of habitat, pollution and human movement
○ Habitat destruction, the use of pesticides, and fungal infections have all contributed to amphibian declines
○ These factors along with invasive species, run off from constrcution/agriculture/road salt, changes to land use and climate change are changing who is living in the rivers
Bioassessment is the idneification of living organisms in natural systems to assess if they are healthy habitats (many organisms used as bionidicators)
Conservative bio
○ Diminished biodiversity may make communities less productive and less resilient to fires, hruicanes, or other envrimental events
○ Lost species mean lost opportunities for disocervy of novel compounds for medical research or industries like fishing and travel
Humans are connected and rely on the land and its inhabitants - biodiversity loss will change lives of all people
Subphylum vertebrata (craniate)
○ All have cranium enclosing the brain
○ Cranium and endoskeleon may be made of cartilage or bone
○ Endoskeleton supports body, allows much bigger body size
○ Muscles attach to endoskeleton to allow movement
○ Vertrebrates include fish, amphibians, mamals, etc
○ Endoskelton permits larger body size without limiting size of internal cavity (this is what exoskeletons do)
○ Cartilage skeleton dveelped prior to bone
○ Bone is stronger than cartilage and superior for msucle to bone attachment
○ Early skeleton were most likley made out of cartilage, some lower verterates only have cartilage
○ Endoskelton of living hagfish, lampreys, sharks and their kin and some bony fishes like sturgeons, mostly composed of cartilage
○ Perhaps bone eveolved, in part, as a means of mineral regulation
○ Phopshorous and calcim are used for many phsyiological rpocesses
○ Vertebrate Classes:
§ Jawless fishes (hagfish, lamprey)
§ Cartilaginous fishes (sharks, rays)
§ Bony fishes (trout)
§ Amphibians (frogs)
§ Reptiles and birds
§ Mammals
§ (fish make up most)
○ A general veretrbate phsyology is difficult
○ Lots of diveristy and iff methods for respiration, exceteion, feeding and reproduction
Ray finned fish - telosts (bony fish)
○ Fins are supported by bone or spines, connected to skeleton
○ Skin over the bone to be web-like fin
○ Contrast to lobe-fined fish (which are more flesh and msucular)
○ Teleost fish (infraclass) - includes salmon, trout, eels etc - so these are bony fish class
○ Make up 96% of all living fishes; 1/2 of all vertebrates
○ Found from high altitudes to great depths
○ Large temp range (-2 dgerees to 44)
○ Marine and freshwater
○ Major chaarcterics:
§ Specilized scales, fins and tails allow exceptional moiblity
§ Changes in jaw strcrure alllow new ttpes of prey to be caught
§ (many more)
§ Swim bladder filled with air for buoyancy - gasses diffsuies in to fill bladder and also involved in sensing
○ Ancestors were covered in heavy, dermal armour
○ Scales are lighter and allow more mobility
○ More easily capture prey, escape predators
○ Teleost scales overlap (reducing drag in water), and grow by adding outer rings
teleost feeding
§ In general most fish spend most of their time searching for food
§ Evolution of jaws meant new type of food became avalble (not just filter feeding)
§ Most fish are carnivores - feeding on zooplankton, insects, larvae, crustaneas, smaller fish
□ But fish mostly cant chew feed
□ Chewing would block water flow across gills
□ The food is swallowed whole
§ Primitive jaws: they cant suck food in bc no cheeks
§ They can porturde some jaw bones - this creates area of low pressure in their cavity, creating more volume and this moves material in bc theres higher pressure outside - makes the food more easier to catch
Teleost reprodcution
§ Most fishes are diocious (separate sexes) with external fetrlization and external dveelopment
§ Some are ovoviviparous fish that dveelop in ovarian cavity - embryo develops in eggs, within mother until hatching
§ Some sharks are viviparous - with some kind of placental attachment to noursh young - embryo develops with placenta in mother intil live birth
§ Most oviparous pelagic fish (external fertlizatin) lay huge numebrd of eggs - eggs laid with no developmenbt of embyro inside mother
Salmon (kings of teleosts)
§ Cultureal, economic history of signficance
§ Natural stcoks continue, but fish darming has grown in past decade
§ Many implications to conservation of salmon and surrouding animals
§ The are anadromous (spawn in freshwater, grow up in sea and come back to freshwater to lay eggs and die)
§ 6 species of pacific salmon and 1 atlantic salmon migrates
§ Atlantic salmon makes repeated spawning runs
§ Pacific species spawn only once and die
§ Pacific species of sockeye salmon:
□ Migrates downstream
□ Roams pacific for 4 years
□ Returns to psawn in parents stream after sexual maturation - cue to come back
□ Young fish are imrinted with odour of their stream
□ May navigate to stream mouth by sensing earth magentic field or angle of the sun and then smelling their way home
□ Salmon are endgaer by stream degredation from logging, farming, pollutin and hydelectric dams
□ The amount of biomass that moves into river and then surroudning forest - biomass is huge bc of them - so many nurteints are brought back - this goes to bear, birds etc - river life is supproted by them
Bony fishes to tetrapods - slow crawl to land
○ 3 feature unite bony fishes and tetrapod descendnts:
§ Bone replaced cartilage during dveelopment
§ Lung or swim bladder is present:
□ Evolved as extension of gust
□ Inc vascularization of the air filled cavity
□ Double circulation directs deoxygentaed blood into the lungs and oxygenated blood out to the body
§ Have several unique cranial and dental characters
○ Characterics adapted for auatic habitats made it psosble to explore terretrial habiatts:
§ Air filled cavity functioned as a swim bladder
§ Paired nares (or nostril) used in chemoreception
○ On land, would be used to draw in air through nares
○ Bony elemts of paired fins
§ Modified for supprt and moevemnt underwater
On land would provide the same function
movement onto land
○ The most dramtic eent in animal evolution
○ Animals are composed of mostly water
§ Land represnet dangerosu habitat
§ Vasculr plants, pulmontae snails and tracheate arthorpods made transition priro to chordates
○ Adaptions included skull, teeth, pectoral gridle and jointed limbs
○ Tetrrapods vs fish:
§ Have stronger backbone
§ Muscles to support the boyd in air
§ Muscles to elevate the head
§ Stronger shoulder and hip gridles
§ More proetctive rib cage
§ Modified ear strcttrue to dtetc airborne sounds
amphibians (tetrapods)
○ (not amniotes)
○ More than 6k species in three orders
○ Remain tied to water - eggs must be kept moist and larvae depend on gills for respiration
○ Challnges faced lving terretrially:
§ Thin skin loses water rapidly - need moist habitat
§ Eggs easily dry out, must be shed into water or kept moist - a few brood young
○ Skin is pouros so gas exchange trhough here
○ Often attached to vegetation like rocks when growing
○ Toads are more able to leave water than frogs but still need to come back to lay eggs
○ Are predatroes and prey for many
○ Salamanders: § 553 species in mrotehrn temeprate regions § Most are small § Burrowing and some aquatic forms may have lost their limbs § Canrvoruos as both larvae and adults - feed on wrms, small arthorpods and molluscs § Breeding behaviour □ Most have auatic lrve and terrstrial addults □ Aquatic: lay eggs in clsyters or stringy masses □ Terrestrial: lay eggs in small clsuter underneath logs or in soft earth Terrestrial species undergo direct dveelpment ○ Frogs and toads: § 5900 species § Near water sources - reproductin requires water and skin is water permeable § All have tailed larvae stage (tadpoles) and tailles, jumping adults (except 1 specis) § Eggs of most hatch into tadpoles with long, finned tail, no legs, internal and external gills and specilzed mouthparts for hervous feeding § Tadpoles look and act diff than adults § Thretedn bc of fungal ifnection that caues their skin to thciken and that reuces their ability to breath through skin
Phylum molluscs (not vertebrates )
○ Bivalves draw in water and remove particles - clear water, help remove partciles
○ More than 90k species and 70k fossil species
○ Includes snails, slugs, clams, mussels, oyster,s squid etc
○ Prominent classes:
§ Gastorpods found on land, seawater (ocean) and freshwaterr
§ Cephlopods found in seawater (ocean) only
§ Bivalves found in freshwater and seawater
○ Molluscs body characterics:
§ Mantle (folds of skin covering viscera) and mantle cavity
□ Produces shell in some mollucs
□ Houses gills or lungs; surfcae acts in gas exchange
□ Highly modified in some mulluscs
§ Headfoot region - many imrtant functions:
□ Well dveelop head
□ Radula (rough ribon like organ)
Foot used for moevemnt - adhesion, exyend, hydraulcially, burrow into mud/sand, fin-like fot swimming
Gastropods
§ Largest mollusc class
§ Many have shells - sluggish, shell is one piece/univalve, may be coiled or uncoiled
§ Development usually involves trochopoe stage (microscopic, free swimming ciliate larva - plantonic and circular) and a veliger stage (shell and foot start to form) § Role in envrinment is diverse, cinldues scrapers of algae, plants (prevnt overgrowth), often prey for many organisms (birds, mammals, fish etc) § Coiled shells may be: □ Right-handed - dextral □ Left handed - sinstral □ Judged by holding the shell with apex up and aperatrue facing you □ Tough operculum proetcs the soft snail heads - helps them form being picked at § Feeding: □ Radula - rough ribbon like organ □ Found in all molluscs except bivalves □ Muscles move radula outwards □ Used for scraping, peicrcing, tearing and cutting and boring □ Two main fucntions: scarpe food partciles from hard surfaces and act as a converyor belt to move food towards the stomach □ Well defined head and mouth □ Radula is a toothy ribbon that is key for collecting food □ The food is variable □ Mosr are herbivores - scarping algae off of surfaces, foraging for green veegation (land snails) □ Some are scavengers, feeding on dead and decaying organic matter Marine snails: some are parasites of corals - some are predators: use radula to tear at their prey - bore holes into shells of shelled prey and proboscis to feed on soft tissue § Respiration: □ Respiratory organs found in mantle cavity □ Ctenidia (primitive gill) - wter and air brought in allowing transfer of gasses □ Secondary gill □ Or lungs in some gastorpodus ® Some snails adapted to land, losing the gills so they have blood vessels aorund the cavity which acts like a respiratory cavity - air trasnfers over tissue (those that went back to freshwater still use the respiratory cavity) § Reproduction: □ Dio- or monoecious (hermaphrodite - prodicg both sperm and eggs) □ Fertalization in water, trcohophore within the egg - shelled eggs may be released to water column or attached to surface, veliger emerge □ Terrestrial and some frsshwater gastropods will fertlize internally within the oviducts - young snails emerge from eggs but other life stages occur inside egg
Gastropods
§ Terrestrial gastorpods: land snails have shells, land slugs have no shells, both are air breathers and have opening to lung visible
§ Freshwater snails: numerous species/lineages that have successfully adapted to freshwater - most have shells - some breathing using gills, some surface to breath air using lungs - important in cultrual cusines (food) and human health - many freshwater snails carry parasites that can transfer to us or livestock
Impacts of invasive snails: reproduce and spread rapidly, may prey on fish eggs and reduce survival rates, outcompete for food and habitat and effect the abundance of native snails, chanelled apple snail acts as vector transfering bacteria and paraiste - can also thraten crops etc
Bivalves
§ 9k extant species
§ Most are marine - some freshwater and brackish water
§ Most are sedentary filter feeders - create water currents using cilia on tehri specilized gills
§ No defined head
§ No radula (toothy ribbon)
§ Very little cephalization (clustering of nervous tissue toward one end)
§ 2 valves held together by a hinge ligament
§ Valves are drawn togetehr by strong adductor muscles
Resting state is shell open
§ Shell: □ Umbo is oldest part of the shell, growth occurs as rings □ Pearls produced when an irritant is lodged between the shell and the mantle - layers of nacre secreted around the foreign material - some force an irritant in to produce pearls in clams □ Section through a bivalve □ Foot hangs along the midline, attached to viscera □ Modified ctendia (gill) hang on eitehr side of foot Siphons are extensions of mantle - adaption of brurowing marine bivalves - inccurent is water in and excurrent is water out - may be used to obtain food and oxygen
Respiration
□ In some bivalves, gills are mdofied to also colelct food particles from water
□ Gills are derived from primitive ctendia by lnegthing the filaments to each side
□ Filaments fused to form plate like lamellae
□ (water in, cilia creates current, water enters gill pores, circulating blood exchange co2 for o2, water out)
□ Long sheets produced to capture food better - lamaellae like gills where food is being captured and brought to mouth
§ Respeirtaion and feedin: □ Filter feeding □ Suspeneded organic matetr enetrs inccurent siphon □ Gland cells on gills secrete mucus to captue paticles □ Food trapped in mucous masses Cilia and palps diret the mucus + food into the mouth § Reproduction: □ Sexes usually separate □ Fertlization usually external; always sexual □ Gametes released in excurrent flow □ Generally indirect dveelopemnt □ Eggs hatch, produce free swimming trochoiphore larva - like anelids □ Followed by veliger (foot and shell are devloping) and spat stages (cilia are covered by valve) □ Many freshwater bivalves have internal fertlization: sperm is reelased tow ater, entering inccurent siphon, fetrlize eggs in water tubes of females fills, larvae develop into bivalved glochidia stage, attaches to gills of passing fish where they live breifly as parsites □ Gochidium of some freshwater bivalves are a specilized veliger stage Cannot swim - parasite on fish gills for several weeks and detach and sink to bottom as free living jeuvalines - this helps keep a dense popultion
