Download aquatic insects

“primitive hexapods”
?
?
?
“basal orders” (= “Apterygota”)
true
INSECTS
NEW ORDER! ca. 2000
A current hypothesis for
the cladistic phylogeny of
the insects and primitive
hexapods
Fig. 7.2
Gullen & Cranston, 2005
The Basal or Apterygote (wingless) Orders
ARCHAEOGNATHA
(= MICROCORYPHIA)
jumping bristletails
THYSANURA
(= ZYGENTOMA)
silverfish, firebrats
ARCHAEOGNATHA
“Jumping bristletails”
X-sec
Shrimp-like profile; tail filaments relatively parallel,
bristly. Primitive, spider-like, single-articulated jaws.
Deocmposers. No economic significance.
THYSANURA (ZYGENTOMA)
“silverfish & firebrats”
Flattened profile, don’t jump, tail filaments held
close to 90 deg. apart. A few are economic pests,
damaging cellulose & fabric.
Thermobia, a firebrat. Giant neurons in
tail filaments studied at UW.
“Aquatic” Insects
 A polyphyletic, ecological assemblage of taxa.
 The aquatic lifestyle has arisen many times in
insect evolution; only in a few orders is it the rule.
 In most, the immature stages are truly aquatic
while the adult is a winged terrestrial form.
TRICHOPTERA
other
orders
with
aquatic
species
PLECOPTERA
ODONATA
EPHEMEROPTERA
Holometabolous,
Endopterygote
Hemimetabolous,
Exopterygote
Paleoptera
AQUATIC INSECTS, an ecological (polyphyletic) group
Importance of Aquatic Insects
Most references to nymphs/larvae; some taxa beyond this lecture
Natural World
Nutrient cycle: decomposers
Water quality: filter feeders
Food Webs: prey & predators, e.g. salmon fry eat bugs
Anthropophilic World
Aquatic environmental quality indicators
Medical/Disease vectors, especially mosquitoes, other flies
Human Food (coryxid eggs; water bug wing muscle; fly pupae)
Sport Fishing (Fly Tying)
Life History & Physiological Aspects of
Aquatic vs. Terrestrial Insects
Development
Terrestrial: variable rate
Aquatic: Generally slower (colder temperature under water)
Respiration
Terrestrial: open system (siphon, physical gill, etc.)
Aquatic: closed tracheal system (gills, cutaneous) with exceptions
Water/Ion Balance
Terrestrial: conserve water from dehydration
Aquatic: conserve ions from dilution
Nitrogen Waste Removal
Terrestrial: uric acid (conserves water)
Aquatic: ammonia (conserves energy)
aquatic
immature
terrestrial
(winged)
adult
EPHEMEROPTERA, mayflies
Fish-eye view through the
mind of the fisherman
(superpredator). Fish as
entomologists!
wing pads
Mayflies are
predaceous or
detritovores as
nymphs. Adults
do not feed.
gill covers
gills
3 “tail filaments”
= cerci
Adult
Larva (nymph, naiad)
Mayfly adult antennae are small; hindwing may be small or vestigal.
forlegs
hindwing
larval molt, subimago molt, & adult
ODONATA, dragon- & damselflies
damselflies
dragonflies
labial mask
All odonates are predators
as both nymphs and adults.
2. grab
1. lunge
dragonfly larva labial mask
hydraulic feeding mechanism
Some large dragonfly nymphs
may take vertebrate prey!
tracheal tubes
adult eclosion
A tropical dragonfly. The wings are always held out at rest.
• Dragon flies have
acute and fast vision.
• Up to 10,000 eye
facets (high
resolution!)
• Adaptations: small
prey capture at high
speed while flying &
mate/mate competitor
detection.
Well-known “loop”
configuration of mating
odonates; male grasps
female with tail claspers;
transfers sperm from
secondary sex organs on
2nd abdominal segment.
A damselfly. Some are spider predators.
Males of some
dragonfly species are
territorial, with
traditional perches.
Some ancient dragonfly relatives (“Griffinflies”)
measured over two feet in wingspan. How could flying
insects live at this scale?
• Orthopteroids i.e.,
cricket- or roach-like.
• Nymphs fully
aquatic, prefer highly
oxygenated water.
• Thoracic gills.
• Two long cerci in
nymphs & adults.
PLECOPTERA, stoneflies
thoracic gills
Stoneflies are
predators or
detritovores as
numphs; adults do not
feed.
wing pads
Some insects can be active at
near-freezing temperatures. A
“winter” stonefly nymph, one
species among various snowactive insects.
Stonefly exuviae.
TRICHOPTERA, caddisflies
• Sister order to the Lepidoptera.
• Moth-like.
long, thread-like antennae
hairy (vs. scaly) wings
wings membranous
(~transparent)
reduced mouthparts
Features distinguishing adult caddisflies from adult moths.
scales
A true moth.
Caddisfly
nymphs are
predaceous or
detritovores;
adults do not
feed.
diverse larval cases (including none!)
caddis fly larval cases
TRICHOPTERA
typical caddisfly larva without case
from Gullen & Cranston 2000
Life stages of an aquatic snout moth (Pyralidae).
Parallel evolution of the caddisfly-like natural history.
Halobates, an open
water predaceous bug.
Marine Insects
Hydrophobic hairs on tarsi of
Trochopus, a related genus.
Egg phoresy: eggs laid on tail of seabird.
all from Cheng 1976
male skating
male
female
Clunio californiensis, an open water
marine midge (DIPTERA:
Chironomidae)
mating behavior
all from Cheng 1976
• Sea skaters, genus Halobates, are the only
insect known to live in the open ocean.
More than 40 species have been described,
but only five (H. micans, H. sericeus, H.
sobrinus, H. germanus and H. splendens)
are oceanic (Andersen & Cheng 2004).
–
Their overall range lies between 40°N and 40°S,
but within that expanse each species has a different
specific range (Cheng 1989). In the eastern tropical
Pacific Ocean (ETP), four of five oceanic species can
be found; H. germanus occurs in the Indian and
western Pacific oceans (Andersen & Cheng 2004).
Sea skaters have been reported thus far in the diet of
more than a dozen surface-feeding seabirds.
END