Basal and aquatic insects Flashcards
what are Ephemeroptera
- mayflies
- Most primitive winged insects
- the first fliers
- Most of life is spent as an aquatic nymph, eating decayed plant material or algae
Ephemeroptera - development
- Only insect with two winged instars
- Sub-imago: penultimate molt – functional wings, quickly molts into…
- Imago/adult: wings, genitalia
Ephemeroptera - adults
- Adult life is short: hours, ~1-2 days
- No feeding mouthparts
- In some, no legs
Ephemeroptera - mating
- Males emerge, swarm over water
- Females emerge, fly to swarm
ephemeroptera - why are swarms formed
- Bc life is short, must also be synchronized so adult males and females can find each other
- Result is huge, sometimes massive, swarms
ephemeroptera - what adaptation do males have for mating
Males have larger eyes (compound eyes) – search for females flying overhead, pounce and mate
what are Odonata
- dragonflies (suborder Anisoptera) and damselflies (suborder Zygoptera)
- First really good fliers
- next fliers after ephemeroptera, and basal to other winged insects
odonata - nymphs
- Aquatic nymphs (live in water as nymphs) – active hunters
- Odonata nymphs have extensive labium to grab prey
odonata nymphs - zygoptera vs anisoptera gills
- Zygoptera have external gills
- Anisoptera have internal rectal gills
odonata adults - how to distinguish dragonflies and damselflies
- 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
odonata adults - how do they hunt?
- they are active visual hunters that catch other insects onto their wing
- Not ephemeral (lasting for a very short time) like mayflies
odonata - mating
- 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
odonata mating - male-male comeptition
Males defend territories, usually along river/lake shores
odonata mating - sperm competition
Male secondary genitalia often adapted to remove sperm of previous mates before actual mating
odonata mating - co-evolutionary arms race between male and female
females evolve more elaborate morphology to have choice over who fertilize her
what are Trichoptera
- Caddisflies
- sisters to Lepidoptera
- not phylogenetically close to ephemeroptera or odonata
- not ancestral to other winged insects
trichoptera - explain apperance
Moth like, But…
- With long filiform antennae
- Reduced mouthparts
- (Often) hairs on wings rather than scales
trichoptera - Aquatic larvae
- Use silk glands mouths to make underwater shelter
- May also be sensitive to pollution
trichoptera: aquatic larvae - how is the shelter created
- they use pebbles and twigs and small pine needles
- Make a protective case over abdomen (for camouflage as well)
How do aquatic insects to breathe underwater?
- closed systems
- open systems
general properties of oxygen
- 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
breathe underwater - closed systems
- 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
breathe underwater - open systems
- snorkel
- “compressible gill”
- “Plastron”
- behavioral ventilation
breathe underwater: open systems - snorkel
- insect has spiracles that stays connected to the top of the water for air
- Can live in water that has zero oxygen
breathe underwater - “compressible gill”
- 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
breathe underwater: “compressive gill” - what is the problem with this method
- 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
breathe underwater - “Plastron”
- 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
breathe underwater: “Plastron” - what is the problem with this method
Theoretically, can be permanent, but not practical to support high metabolism
breathe underwater - behavioral ventilation
- 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)
Aquatics and water quality monitoring - basic concept
aquatic communities are bioassay for water qualities like:
- Temperature
- Sedimentation
- Pollution
- Eutrophication
Aquatics and water quality monitoring - aquatic nymphs
- 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
Aquatics and water quality monitoring -benefits of using
- Inexpensive relative to chemical testing
- General response (don’t need specific chemicals, combinations)
Aquatics and water quality monitoring -costs of using
Not good for specific level of chemical – good for broader qualities
