THE XERCES SOCIETY FOR INVERTEBRATE CONSERVATION Aquatic Invertebrates in Pacific Northwest Freshwater Wetlands |
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| abdomen - the third major body region of an insect, posterior to the head and thorax. |
| anal gills - fleshy, finger-like gills on the last segment of the abdomen. |
| anal prolegs - a pair of fleshy, unsegmented lobe or leglike structure at the end of the abdomen; act as extra appendages during the larval stages; absent in adults. |
| antenna (pl. antennae) - a pair of segmented appendages located on the head above the mouthparts; usually sensory in function. |
| anterior - at or directed towards the front end, either in reference to part of an entire organism (anterior end of a mayfly = head) or to a particular body part (anterior edge of thorax = region of the thorax closest to the head). |
| anus - excretory opening at the posterior end of an invertebrate. |
| aperture -opening, in this case the opening of a snail shell through which the muscular body can be extended. |
| apical - located at the end, tip, or outermost part of a segment or structure |
| apotome - a part or subdividison |
| arthropod - a member of the phylum Arthropoda, which includes invertebrates such as insects, arachnids (spiders, scorpions, mites, ticks), myripods (centipedes and millipedes) and crustaceans (crabs, lobsters, crayfish, shrimp). Arthropods have a hard exoskeleton, segmented body, and articulated appendages. |
| beak - the rounded or pointed extremity (umbo) of a bivalve shell; its original growth point; may also be used as a term for the piercing/sucking mouthpart of Hemiptera. |
| benthic - associated with the bottom or substrate of a waterbody. To be benthic, an organism must spend the majority of its time on or between the rocks, mud, sand, or other substrate in moving or still water. Most macroinvertebrates are benthic for only part of their life cycle. |
| benthos - The collection of organisms living on or in sea or lake bottoms. |
| biological assessment (or bioassessement) - surveying or monitoring living things to evaluate the overall health of a body of water or other habitat; a measure of the effect that human activities have had on that body of water or habitat. |
| biological condition - the ability of a waterbody to support a diverse and healthy biological community. |
| biota - a single term to describe the collection of organisms living in a particular habitat (e.g. freshwater biota includes fish, amphibians, invertebrates, algae, and other plants). |
| carapace - A hardened shield that covers the dorsal surface of the body, consisting of fused sclerites |
| cerci (sing. cercus) - pair of appendages at posterior end of the abdomen of many invertebrates; often diagnostic for some aquatic insect larvae (alll stoneflies have two cerci; mayflies have 3 cerci) |
| chaetae (sing. chaeta) - stiff hairs; found on segmented worms (Annelida). |
| clade - a monophyletic group of taxa sharing a closer common ancestry with one another than with members of any other clade. |
| complete metamorphosis - a developmental process in the life cycle of invertebrates in which the larval stage is followed by a distinct pupal stage, from which the adult stage emerges |
| cyst - a sac, vesicle, or bladderlike structure. |
| denticle - bump or toothlike projections on the surface of the body. |
| diversity - the number of different species in a given area. |
| detritus - pieces of dead or decomposing plant or animal material in the water column or accumulated on the substrate. |
| dorsal - top or upper surface; the region of most animals that one would call the "back." |
| dorsoventral - from top to bottom, or from the upper to lower side; usually in reference to being flattened from top to bottom, like a flatheaded mayfly, a sowbug, or a water penny. |
| ecoregion (bioregion) - area with a distinct assemblage of species; and a unique geology, vegetation, land use, and topography. For example, the Pacific Northwest west of the Cascades ("Cascadia"). |
| elytra (sing. elytrum) - the hardened, thickened outer (front) wings of adult beetles (Coleoptera). |
| ephemeralhabitat - a habitat that only exists temporarily or periodically, such as a vernal pool. |
| evenness - The relative abundance of a species within a given area. For example, if a wetland has numerous different taxa with each one making up a similar proportion of the total taxa, the wetland may be considered very even; if 95% of the taxa in a wetland is made up of a single species, it would not be considered very even. This is another measure of diversity. |
| eutrophic - a waterbody that has been enriched in nutrients, especially nitrogen and phosphorus, and with a high algal productivity; usually characterized by low oxygen at certain times of year. Eutrophication can happen naturally or may be a result of excessive nitrates, often from fertilizer or sewage runoff. |
| extant - still in existence; not destroyed, lost, or extinct. |
| family - the taxonomic level that is a subdivision of an order, containing a group of related genera and species. Example: Culicidae (all mosquitos) is a family within the order Diptera (all true flies). |
| femur (pl. femora) - third major segment of the leg, located between the trochanter and tibia; often the closest conspicuous segment nearest the body. |
| filamentous - thin and threadlike; may be inreference to antennae, gills, or strings of algae |
| flange - a rim or lip |
| foretrochantin - a separate, small, platelike appendage at the base of the trochantin of caddisfly (trichoptera) larvae. |
| gametes - cells involved in reproduction; gametes fuse together during conception in organisms that reproduce sexually. |
| genus - A group of closely related species; the taxonomic level below family and above species. The species within a genus often look very similar, and can be difficult to tell apart. |
| gill - evagination (protrusion) of the body wall or hindgut that functions in gaseous exchanges in aquatic animals. |
| glossa (pl. glossae) - one of a pair of lobes at the apex of the labium between the paraglossae. |
| gradient - also known as slope; the steepness of a streambed that influences water velocity and substrate size. |
| head - the most anterior body major body region of an insect; bears the eyes, antennae and mouthparts. |
| hinge- collective term for structures of the dorsal region of bivalve shells that function in opening and closing the valves. |
| hydrophobic -"water fearing"; refers to water repellant hairs and other structures |
| hyporheic - the region beneath and lateral to a stream bed, where shallow groundwater and surface waters mix. |
| IBI - Index of Biological Integrity; an analysis tool that uses characteristics of the macroinvertebrate community that respond predictably to changes in human influence in the watershed, to develop scoring criteria for evaluating the biological condition of a waterbody; these characteristics may include total taxa richness (number of different kinds of macroinvertebrates found in a sample), richness or dominance of a particular taxon, and percent of the community that is tolerant to pollution. |
| insect- an organism in the class Insecta, distinguished by having an exoskeleton, three major body regions (head, thorax, and abdomen), and six legs. Includes many orders, such as the true flies (Diptera), beetles (Coleoptera), and mayflies (Ephemeroptera). |
| instar - the insect between successive molts, i.e. a first instar is an insect between hatching and the first molt. |
| interflow - water that travels laterally across the landscape right after it rains. |
| invertebrate - animal without a backbone. Includes insects, crustaceans, mollusks, annelids and other animals. |
| keel- an elevated ridge. |
| labial palps - small lobes or feller-like structures at the front of the labium; in Odonata (dragonflies and damselflies) they are pronounced and often have spines or teeth on the inner margin, and are used for grabbing prey. |
| labium - the lower "lip" or most posterior mouthpart at the front of an insect's head; especially pronounced in dragonflies and damselflies (Odonata). |
| labrum - the upper "lip" or most anterior mouthpart at the front of an insect's head. |
| lacinia - insect mouthpart at the end of the maxillae and, along with the mandibles; helpful in identifying some insects, particularly the stonefly family Perlodidae. |
| lateral - at or toward the side; analogous to a profile. |
| lentic - aquatic environments with standing water, such as lakes, ponds and swamps, and the inhabitants of such environments. |
| lotic - aquatic environments with flowing water, such as streams or rivers, and the inhabitants of such environments. |
| macroinvertebrate - "large" animals (i.e. visible to the unaided eye) that lack backbones. Freshwater macroinvertebrates include all aquatic insect larvae (plus a few pupae and adults) and other aquatic invertebrates (worms, snails, clams, leeches, crayfish, etc.) that are larger than 0.5 mm, or about half the thickness of a dime. The largest of the freshwater macroinvertebrates in North America are the mussels and crayfish. |
| mandible - the chewing mouthpart of many insects, particularly prominent in predators. |
| maxillae (sing. maxilla) - major mouthparts of the head posterior tothe mandibles; sometimes very prominent as in many stoneflies (in lacinia, which is the inner lobe of the maxilla). |
| maxillary palps - finger-like appendages on the maxillae; important in the identification of some mayflies (Ephemeroptera). |
| mesonotum - the dorsal sclerite of the middle (second) thoracic segment. |
| mesosternal Y - a Y-shaped characteristic between the legs on the underside of the mesothorax of many stoneflies; particularly helpful in identifying Perlodidae stoneflies, but often not very clear in immature or damaged specimens. |
| mesothorax - the middle or second segment of the thorax, in insects. |
| metathorax - the third or posterior segment of the thorax, in insects. |
| metanotum - the dorsal surface of the metathorax, in insects. |
| metric - a characteristic of an assemblage of organisms (in this case macroinvertebrates) that responds predictably to changes in human disturbance; used in multimetric indices. |
| mitigate - in the case of wetlands, to recreate or restore a wetland to compensate for wetlands that are being lost due to a human activity (such as building a parking lot where a wetland used to stand, and replacing it with a man-made wetland habitat). |
| molt - the process of shedding the exoskeleton and forming a new one; an insect molts to the next instar |
| multimetric index - an analysis tool that uses graphical interpretation of predictable biological responses to human disturbance to evaluate the level of human impact on a particular habitat (see also IBI). |
| multivariate model - a statistical model that allows analysis and interpretation of complex data sets; utilizes independent and dependent variables that are related to each other to varying degrees. |
| naupliar - The free-swimming first stage of the larva of certain crustaceans, having an unsegmented body with three pairs of appendages and a single median eye. |
| nodus - a strong cross vein near the middle of the upper border of the wing. |
| nymph - an immature stage of insects that undergo incomplete metamorphosis (i.e. do not have a pupal stage), such as true bugs (Hemiptera) and mayflies (Emphemeroptera) |
| oligotrophic - a water body that is nutrient-poor, oxygen-rich, and has only modest algal and plant communities. |
| omnivore - an animal that feeds on a mixed diet of living plant and animal matter. |
| operculate - a flap-like structure that acts as a lid or cover for an opening or body part; e.g., some mayflies have platelike operculate gills that cover the remaining gills. |
| operculum - plate or lid that covers other body parts; fish have an operculum covering their gills; many snails have an operculum that covers the aperture of their shell when the body is withdrawn. |
| order - the taxonomic level below class and above family; a subdivision of class or subclass, containing a group of related families. For example, Diptera (the true flies) is an order within the class Insecta. |
| palps - segmented arm-like appendages on the maxillae or labium. |
| paraglossa - one of a pair of lobes at the apex of the labium. |
| pelagic - inhabiting the open sea; ocean-dwelling. |
| percent impervious area - the percentage of a watershed that is impermeable to water; often the portion of the watershed covered with roads, rooftops, and parking lots. Percent impervious area can be used as a rough estimate of human influence when developing IBIs for urban and urbanizing watersheds. |
| pleural folds- folds in in the lateral (side) sclerites of an insect. |
| posterior - at or directed towards the rear end, either in reference to part of an entire organism (posterior end of a mayfly = end of the abdomen) or to a particular body part (posterior edge of thorax = region of the thorax furthest from the head). |
| pre-apical claw - claw situated just before the apex (tip) of the leg. |
| prementum - the distal part of the labium; the grabbing part of the modified labium of dragonflies and damselflies (Odonata). |
| procercus - nodule located above the anus, bearing the anal setae, as in some fly larvae (Diptera). |
| proleg - one of the fleshy, unsegmented protrusions of certain insect larvae, located on the ventral surface of the thorax or abdomen. These are not true legs and are absent in the adult form. |
| proboscis - elongate piercing and/or sucking mouthpart of some insect taxa. |
| pronotum - the dorsal surface of the first thoracic segments of insects; top of the the segment closest to the head. |
| prosternal horn - a small protrusion from the sternum, or ventral sclerite, of the prothorax |
| prothorax - the first (most anterior) of the three thoracic segments of insects; the throacic segment closest to the head. |
| raptorial - modified to grasp and hold prey, as in the forelegs of some true bugs and beetles |
| reference conditions - the chemical, physical, and biological characteristics expected in a body of water in the absence of human influences in the watershed. Since no watershed is completely lacking in human influence, reference conditions are usually represented by the least disturbed water bodies in an area. |
| reference sites - bodies of water within watersheds that most closely resemble pre-industrial conditions; generally of high biological integrity. |
| richness - the number of different species in a habitat or specific area, as in species richness; biodiversity. |
| riparian - occurring along the banks of rivers or streams |
| rostrum - modified beak or piercing mouthpart present in some arthropods; used to pierce prey, insert digestive enzymes, and suck out food; may also be refer to a long spinelike process that projects from the front of the head of some crustacea. |
| sclerites - a hardened plate forming part of the exoskeleton of an insect; may be surrounded by a more membranous area.. |
| sclerotized - hardened; with sclerites. Most aquatic insects have some sclerotization; riffle beetle larvae, for example, are almost entirely sclerotized, while midges only have a sclerotized head capsule. |
| scutellum - small triangular plate or sclerite between the front edges of the outer wings, in some insects (Hemiptera, Coleoptera). |
| sessile - not freely moving; often attached to a substrate; for example, sponges (Porifera). |
| slough - a swamp, marsh, bog or pond; an area of soft, muddy ground and slow-moving or stagnant water. |
| species - the most specific taxonomic level; a group of closely related individuals or popualtions that can interbreed and produce fertile offspring (given they are of the right sex and are fertile). Every described species has a unique binomial designation. |
| spiracles- small breathing pores or openings in the exoskeleton of an insect; used in respiration. |
| stenotherm - an organism that requires a limited range of water temperatures to survive; for example, a cold water stenotherm will only be found regularly in cold, often spring- or groundwater-fed streams and rivers. |
| substrate - the mineral (rocks, silt) and organic (woody debris, leaves) materials that comprise the bed or bottom of a water body and provide habitat for benthic macroinvertebrates. |
| tarsal claw - claw on the apex of the tarsal segment (last or most distal segment) of an insect leg. |
| tarsus - (pl. tarsi) the last or most distal segment of an insect leg, just beyond the tibia; may have multiple smaller segments and claws. |
| taxon - (pl. taxa) a named group of organisms; generic term to describe a group of organisms that share characteristics that make them similar on some level. Examples are the taxonomic levels kingdom, phylum, class, order, family, genus and species. There are further taxonomic divisions within these levels, such as subphylum, subclass, tribe, and subspecies. |
| taxonomy - the science of classifying organisms; assigning names and relationships related to the hierarchy of all life; placing organisms within taxa according to morphological or genetic characteristics. |
| thoracic - of or referring to the thorax. |
| thorax - the second of the three major body regions of an insect; divided into three segments: the prothorax, mesothorax and metathorax. The legs and wings (if present) are attached to the thorax. |
| tibia - The fourth segment of the leg, between the femur and the tarsus. |
| tibial spur - a spine that may be prsent on the tibia, usually at the distal end. |
| trochantin - A small sclerite at the base of the thoracic wall immediately above the first leg segment. |
| tubercles - bumps or spikes on the exoskeleton; particularly prevalent in the mayfly family Ephemerellidae. |
| turbidity - the amount of cloudiness in the water, generally from silt, plankton or other organic matter. |
| umbo - the beak of a bivalve shell; the protuberance of each valve above the hinge. |
| valves - the two parts (halves) of the shell of a bivalve mollusk (mussels, clams, etc). |
| ventral - at or towards the bottom or underside of a structure or organism; analogous to our stomach. |
| ventral apotome - plate on the underside of a caddisfly (Trichoptera) head that separates the two major sides of the head capsule; can be helpful in identifying many caddisflies. May separate the two sides entirely or it may only be present as a small wedge at the top or the bottom of the line where the two sides meet. |
| voltinism - the number of life cycles completed by a species in one year; for example, if an egg is laid in January and the organism hatches, grows, emerges as an adult, and lays eggs and dies the following January, then the taxon has gone through 1 generation in a year and is considered univoltine; bivoltine = 2 generations/year; multivoltine = more than 2 generations/year; and semivoltine = more than 1 year/generation. |
| whorl - one complete turn or coil, referring here to a snail shell |
| wing pads - small structures on the thorax of nymphs that will eventually develop into full-sized functional wings as the nymph grows into an adult. |
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