Science of Water : Concepts and Applications

186 The Science of Water: Concepts and Applications
d. Piercers—These herbivores pierce plant tissues or cells and suck the fl uids out. Some
caddisfl ies do this.
e. Predators—Predators eat other living creatures. Some of these are engulfers, that
is, they eat their prey completely or in parts. This is very common in stonefl ies and
dragonfl ies, as well as caddisfl ies. Others are piercers, which are like the herbivorous
piercers except that they eat live animal tissues.
2. Mode of Existence (habit, locomotion, attachment, concealment):
a. Skaters—Adapted for “skating” on the surface where they feed as scavengers on organisms
trapped in the surface fi lm (e.g., water striders).
b. Planktonic—Inhabiting the open-water limnetic zone of standing waters (lentic; lakes,
bogs, ponds). Representatives may fl oat and swim about in the open water, but usually
exhibit a diurnal vertical migration pattern (e.g., phantom midges) or fl oat at the surface
to obtain oxygen and food, diving when alarmed (e.g., mosquitoes).
c. Divers—Adapted for swimming by “rowing” with the hind legs in lentic habitats and
lotic pools. Representatives come to the surface to obtain oxygen, dive and swim when
feeding or alarmed; may cling to or crawl on submerged objects such as vascular plants
(e.g., water boatmen; predaceous diving beetle).
d. Swimmers—Adapted for “fi shlike” swimming in lotic or lentic habitats. Individuals
usually cling to submerged objects, such as rocks (lotic riffl es) or vascular plants
(lentic), between short bursts of swimming (e.g., mayfl ies).
e. Clingers—Representatives have behavioral (e.g., fi xed retreat construction) and
morphological (e.g., long, curved tarsal claws, dorsoventral fl attening, and ventral gills
arranged as a sucker) adaptations for attachment to surfaces in stream riffl es and waveswept
rocky littoral zones of lakes (e.g., mayfl ies and caddisfl ies).
f. Sprawlers—Inhabiting the surface of fl oating leaves of vascular hydrophytes or fi ne
sediments, usually with modifi cations for staying on top of the substrate and maintaining
the respiratory surfaces free of silt (e.g., mayfl ies, dobsonfl ies, and damselfl ies).
g. Climbers—Adapted for living on vascular hydrophytes or detrital debris (e.g., overhanging
branches, roots and vegetation along streams, and submerged brush in lakes)
with modifi cations for moving vertically on stem-type surfaces (e.g., dragonfl ies and
damselfl ies).
h. Burrowers—Inhabiting the fi ne sediments of streams (pools) and lakes. Some construct
discrete burrows, which may have sand grain tubes extending above the surface of the
substrate or the individuals, may ingest their way through the sediments (e.g., mayfl ies
and midges).
MACROINVERTEBRATES AND THE FOOD WEB
In a stream or lake, there are two possible sources of primary energy: (1) photosynthesis by algae,
mosses, and higher aquatic plants and (2) imported organic matter from streamside/lakeside vegetation
(e.g., leaves and other parts of vegetation). Simply put, a portion of the food that is eaten
grows right in the stream or lake, such as algae, diatoms, nymphs and larvae, and fi sh. A food that
originates from within the stream is called autochthonous.
Most food in a stream comes from outside the stream. This is especially the case in small,
heavily wooded streams, where there is normally insuffi cient light to support instream photosynthesis,
so energy pathways are supported largely by imported energy. Leaves provide a
large portion of this imported energy. Worms drown in fl oods and are washed in. Leafhoppers
and caterpillars fall from trees. Adult mayfl ies and other insects mate above the stream,
lay their eggs in it, and then die in it. All of this food from outside the stream is called
allochthonous.