Benthic macroinvertebrates They are ___________  even in the most _________ or  environmentally extreme lotic environments contain some ________________ organisms. n In general: macroinvertebrates refers to fauna retained by a ___________________. Exception: many early life stages pass through this mesh size (mesh um)

Macroinvertebrate communities in many lotic environments consists of several _________ species, from numerous phyla: n __________: insects, mites, crayfish n Molluscs: snails, limpets, mussels, clams n ___________: segmented worms n Nematodes: roundworms n _______________: flatworms

Most stream macroinvertebrate species are associated with surfaces of the _________ bottom n bedrock, _________ and finer sediments n or other stable surfaces (fallen _______, snags, roots, and submerged or emergent aquatic vegetation. (Usually not free- swimming) Collectively called __________________. n Fundamental ____ in food web between organic matter resources (leaf litter, algae, detritus) and ________.

Aquatic insects Extremely diverse both taxonomically and _______________. n Usually the most abundant large organisms collected in stream benthic samples. Thirteen __________ in N. America  five are strictly aquatic  _________: dragonflys and damselflies  Plecoptera: stoneflies  ______________: mayflies  Trichoptera: caddisflies  ____________: hellgrammites

Dragonfly, damselfly

Stonefly nymphs

Stonefly predator

Mayfly Larvae

Adult mayfly

Adult caddis fly

Caddis larvae, adult

Caddis larvae and cases

Shredders

Problems of living in a stream How to obtain ____________?  or how to remain in a _______ position? n Some lotic species have developed structures to obtain oxygen from the atmosphere  (analogous to ______________) n Others use temporary storage of an air bubble (analogous to SCUBA diving) A few species use __________________ (analogous to vertebrate hemoglobin) n Many have developed _________ gills for obtaining oxygen dissolved in water.

Morphological adaptations for existence in running water n ____________ projections along trailing edges of legs and body to form hydrofoils that _______ the organism onto the substratum. n _______________ of body shape to offer reduced resistance while swimming. n ____________ to provide attachment to smooth surfaces. n Leg and anal ______ to provide attachment to a variety of surfaces.

Life history diversity and adaptability n Streams are very dynamic  __________  spatially  ____________  trophically, etc.

Adaptability: 1. Some species are adapted to ___________ streams  by having ____________ stages that hatch as they are hydrated when flow resumes. 2. Closely related species that occupy a similar trophic function (or level)  may temporally separate growth and _________________ within the same stream reach.

3. ___________ timing of larval __________ (limits _____________ competition by regulating development of young) n or ____________ release by adults for mate attraction (synchronizes reproductive behavior with the appearance of young at the time of optimal food availability).

4. Considerable variation in the ______________ cycles to take advantage of resources when plentiful. n Some species are  multivoltine  ____________  univoltine  or may require 2 or 3 years to complete life cycle (semivoltine) n Life history of a particular species may vary over its’ ____________________.  univoltine in a portion of its’ range  semivoltine in ________ portion of range.

Feeding techniques __________: scraping microbes on solid surfaces. __________ of CPOM Collecting or ___________ of drifting FPOM. Predation Most benthic invertebrates gain little nutritive value from __________ until it has undergone considerable microbial modification (digest ________)