Basal and aquatic insects

Question 1

what are Ephemeroptera

Answer 1

• mayflies
• Most primitive winged insects
• the first fliers
• Most of life is spent as an aquatic nymph, eating decayed plant material or algae

Question 2

Ephemeroptera - development

Answer 2

• Only insect with two winged instars
• Sub-imago: penultimate molt – functional wings, quickly molts into…
• Imago/adult: wings, genitalia

Question 3

Ephemeroptera - adults

Answer 3

• Adult life is short: hours, ~1-2 days
• No feeding mouthparts
• In some, no legs

Question 4

Ephemeroptera - mating

Answer 4

• Males emerge, swarm over water
• Females emerge, fly to swarm

Question 5

ephemeroptera - why are swarms formed

Answer 5

• Bc life is short, must also be synchronized so adult males and females can find each other
• Result is huge, sometimes massive, swarms

Question 6

ephemeroptera - what adaptation do males have for mating

Answer 6

Males have larger eyes (compound eyes) – search for females flying overhead, pounce and mate

Question 7

what are Odonata

Answer 7

• dragonflies (suborder Anisoptera) and damselflies (suborder Zygoptera)
• First really good fliers
• next fliers after ephemeroptera, and basal to other winged insects

Question 8

odonata - nymphs

Answer 8

• Aquatic nymphs (live in water as nymphs) – active hunters
• Odonata nymphs have extensive labium to grab prey

Question 9

odonata nymphs - zygoptera vs anisoptera gills

Answer 9

• Zygoptera have external gills
• Anisoptera have internal rectal gills

Question 10

odonata adults - how to distinguish dragonflies and damselflies

Answer 10

• Dragonflies have eyes touching or nearly so
• Damselflies do not
• Dragonflies have wings perpendicular to longitudinal axis of body, like airplane
• Damselflies have wings parallel to longitudinal axis

Question 11

odonata adults - how do they hunt?

Answer 11

• they are active visual hunters that catch other insects onto their wing
• Not ephemeral (lasting for a very short time) like mayflies

Question 12

odonata - mating

Answer 12

• Males have ‘secondary genitalia’ on 2nd or 3rd abdominal segment: male transfers sperm from regular genitala to here
• Then grabs female behind head with clasper at distal end of abdomen
• Female curls her abdomen up to receive sperm from secondary genitalia

Question 13

odonata mating - male-male comeptition

Answer 13

Males defend territories, usually along river/lake shores

Question 14

odonata mating - sperm competition

Answer 14

Male secondary genitalia often adapted to remove sperm of previous mates before actual mating

Question 15

odonata mating - co-evolutionary arms race between male and female

Answer 15

females evolve more elaborate morphology to have choice over who fertilize her

Question 16

what are Trichoptera

Answer 16

• Caddisflies
• sisters to Lepidoptera
• not phylogenetically close to ephemeroptera or odonata
• not ancestral to other winged insects

Question 17

trichoptera - explain apperance

Answer 17

Moth like, But…
- With long filiform antennae
- Reduced mouthparts
- (Often) hairs on wings rather than scales

Question 18

trichoptera - Aquatic larvae

Answer 18

• Use silk glands mouths to make underwater shelter
• May also be sensitive to pollution

Question 19

trichoptera: aquatic larvae - how is the shelter created

Answer 19

• they use pebbles and twigs and small pine needles
• Make a protective case over abdomen (for camouflage as well)

Question 20

How do aquatic insects to breathe underwater?

Answer 20

1. closed systems
2. open systems

Question 21

general properties of oxygen

Answer 21

• Not much in the water – max 15 ppm in water vs 200,000 in air
• In general: cooler, swifter water has more oxygen than warm, still water
• Thus, much more is available in streams than lakes

Question 22

breathe underwater - closed systems

Answer 22

• no spiracles
• they can just diffuse through cuticle: must be very small – often instar immatures
• or have gills: thin cuticle, high surface area:volume ratio, lots of trachea

Question 23

breathe underwater - open systems

Answer 23

• snorkel
• “compressible gill”
• “Plastron”
• behavioral ventilation

Question 24

breathe underwater: open systems - snorkel

Answer 24

• insect has spiracles that stays connected to the top of the water for air
• Can live in water that has zero oxygen

Question 25

breathe underwater - “compressible gill”

Answer 25

- carrying a bubble and use it to diffuse oxygen out of the water - bubble can be carried, stretched under wing, attached to abdomen - steps: 1. Insect uses O2, releases CO2 2. CO2 dissolves into water, more O2 dissolves into bubble and repeat

Question 26

breathe underwater: "compressive gill" - what is the problem with this method

Answer 26

- bubble size decreases (‘compressible’) bc N2 dissolves out - lower surface area: volume reduces diffusion of O2 and insect has to go back up for more

Question 27

breathe underwater - "Plastron"

Answer 27

- Hold layer of air against skin/spiracles with RIGID hairs (hydrophobic) or cuticle extensions - Volume does not decrease (as in bubble) bc of rigid support - O2 gradient maintained

Question 28

breathe underwater: "Plastron" - what is the problem with this method

Answer 28

Theoretically, can be permanent, but not practical to support high metabolism

Question 29

breathe underwater - behavioral ventilation

Answer 29

- circulate fresh water around, avoid O2-depleted ‘boundary layer’ by moving legs, gills, or self - insects choose its location to maximize O2 (swiftly moving water)

Question 30

Aquatics and water quality monitoring - basic concept

Answer 30

aquatic communities are bioassay for water qualities like: - Temperature - Sedimentation - Pollution - Eutrophication

Question 31

Aquatics and water quality monitoring - aquatic nymphs

Answer 31

- Aquatic nymphs as indicator of water quality: sampling nymph communities can give good indication of water quality - because some species require clean well-oxygenated water; some do well in more polluted water

Question 32

Aquatics and water quality monitoring -benefits of using

Answer 32

- Inexpensive relative to chemical testing - General response (don’t need specific chemicals, combinations)

Question 33

Aquatics and water quality monitoring -costs of using

Answer 33

Not good for specific level of chemical – good for broader qualities