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Lec 1b: Life in Water - Adaptations

I. Diversity in FreshwaterII. Adaptations to Life in Freshwater

A. RespirationB. FlowC. Osmotic balanceD. Life history E. MotionF. Feeding & Food Collection

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I. Diversity in Freshwaters

A. Low compared to Marine(41 vs. 56 phyla; 15 marine only; ID?)

B. Possible reasons….

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1. Osmotic incompatibility2. Ephemeral nature of FW systems3. Low volume4. Physically discontinuous

-What taxa can overcome this? (metapop’n)-How do humans ‘help’?

5. Dynamic (Chem. & Phys)-actually increases diversity….

6. Exceptions: Non-glacial lake endemics

Ephemeroptera (Mayfly)Odonata (Dragon/Damsel)Plecoptera (Stonefly)Hemiptera (True Bug)Megaloptera (Hellgrammite)Trichoptera (Caddisfly)Coleoptera (Beatle)Diptera (Fly)

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Insect Diversity

Order Aquatic Stage # Aquatic Spp #Non-Aquatic Spp

Collembola All 25 300Ephemeroptera Nymphs 625 0Odonata Nymphs 425 0Orthoptera All 5 1000Plecoptera Nymphs 425 0Hemiptera All 400 4600Neuroptera Larvae 5 300Megaloptera Larvae 40 0Coleoptera All 1000 30000Trichoptera Larvae 1000 0*Lepidoptera Larvae 50 10000Diptera Larvae 10%? 17000Hymenoptera Larvae 0.5%? 17000

Orders of Insects with Aquatic Life Stages

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Fishes are the most numerous of all vertebratesAmphibians 2500 sppReptiles 6000Birds 8600Mammals 4500Fish 25000 (Why?)

Fish Distributions

Fish Diversity

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• 58% are in marine (0.58*25000=14,500spp)•(15,482 marine species as of Nov.2004)• 41% are in freshwater• 1% occupy both

Breathing air vs. waterTidal process in air, ventilation in waterAir Water Contrasts:

Air Water High [O2] Low [O2] Light (0.013 kg/l) Heavy (1 kg/l)

II. Adaptations to Life in FreshwaterA. Respiration

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Increasing exposure to DO can be active or passive

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Obtain O2 directly from air:

Snorkels: -direct: rat tailed maggot -indirect: use of aquatic plants

-sharp spiracles thrust into plant arenchyma (Donacia)

Tubes: Mosquitoes, Ranatra -change from caudal tube in larvae to thoracic horns in pupae

Both make use of hydrophilic and hydrophobic surfaces

PROBLEM: not transportable; need to 'grab' some air and keep it in contact w/ spiracles

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Direct diffusion through the body surface if small (e.g. Diptera)

Why not possible for larger organisms?

Tracheal gill (Ephemeroptera, Plecoptera, Odonata, Trichoptera)

-operates best in moving water. Why?-anal gills in Anisoptera-filamentous gills in Trichoptera, Neuroptera-can adapt to changes in DO by ventilation

-Mayfly gills nervous and muscular connections-Dragonflies expand and contract rectal chamber-Damselflies fan caudal lamellae-Stoneflies, caddisflies do 'pushups', or undulate-Hexagenia will undulate in their burrows

to improve water flow

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Questions:

Does the surface area of the gills have anything to do with the DO concentration of the habitat?

What could be some mitigating factors or adaptations?

Ephemeroptera (Mayflies)Plecoptera(Stoneflies)

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1. Morphology (which are general?)a. Body flatteningb. Streamlined or fusiform bodyc. Reduction of projecting structures (aids swimming)d. Anchoring devices: suckers, hooks, silke. Small sizef. Ballast

2. Behaviora. Avoid currentb. Migration (incl. drift)c. Emergence

3. Distinct communities (Riffle vs. pools) -Flow adapted taxa: 'Rheophilic' and 'Torteniculous' taxa

II. Adaptations to Life in Freshwater B. Flow (why no/little plankton in lotic systems?)

Belphariceridae

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• Laminar flow• Turbulent flow

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Salt and freshwaters present different problems

One of two options….

II. Adaptations to Life in Freshwater C. Osmotic balance

II. Adaptations to Life in Freshwater D. Life History

(Does the habitat meet all of the needsfor metabolism, food, reproduction?)

1. Migration (insects, fishes)2. Partially aquatic (amphibians, insects)3. Resting stages in temporary habitats

(crustaceans, molluscs)

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II. Adaptations to Life in Freshwater E. Motion

1. Passive-Floating(Problem: Most organismsare more dense than water

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Sinking velocity of a spherical particle follows Stoke’s Law :

g = gravitational acceleration (m / s2) η = coefficient of viscosity of the medium (kg/m/s) densm = density of fluid densp = density of particle r = radius of the particle

Stokes Law - applies to very small spherical objects

II. Adaptations to Life in Freshwater E. Motion

1. Passive-Floating

)densdens(9

gr2v pm

2

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Phytoplankton Macrophytes18

II. Adaptations to Life in Freshwater E. Motion

2. Swimming-Both push against

water and reduce drag

a. Effect of gravity is less than in air - fish can “float” - leading to free movement through a 3 dimensional environment

b. Most muscle can be devoted to movement rather than to offsetting gravitational pull

c. High density increases resistance; and hence increases energetic costs -musculature must be devoted toward forward movement

d. Streamlining will reduce resistance of dense watere. Surface area of 'propelling' surface

(vs. a bird; better yet think about penguin vs. flying birds)19

1. Within species, individuals will have more vertebrae or body segments when reared at colder temps

2. More vertebrae in fish at higher latitudes

3. Water temp ~ viscosity

4. How to cope? Greater flexion, more vertebrae

5. Check Re eqn: get longer, reduce effect of viscosity

Jordan’s Rule: Links between fish morphology, water temperature, and density?

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F. Feeding

Blackfly larvae

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Caddisfly net

Daphnia ‘leg’

Copepod

Cladoceran

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F. Feeding

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F. Feeding

Lab

Consider some of these adaptationswhen examining specimens

Infer aspects of habitat and strategiesfor living in water from organism morphology