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| Sources for definitions: Gordh & Headric 2001, Martin & Davis 2004, Lawrence 2000, Thorp& Covitch 1991, Merriam-Webster 2005, Blass 2007 and the various identification key references | |
 pala |
expanded anterior tarsal segment |
| palar pegs | row of projections on the pala , used to maintain secure contact between male and female during copulation |
| palm(ar) | proximal part of propodus of chela (descriptive of) |
| palp(al) | a paired, finger-like (digiform) appendage of the maxilla and labium (descriptive of) |
| palpi | plural of palpus, an alternative to palp |
| palpus | a paired, finger-like appendage of the maxilla and labium |
| papilla(e) | any small, soft projection; any conical cuticular projection (plural) |
| para- | beside |
| paraglossa(e) | a paired, labial structure positioned at either side of the ligula (plural) |
| paramere | one of the paired lobes exterior to the penis |
| paraproct |
a pair of lobes laterally bordering the anus |
| parasitic |
referring to organisms that live in or on another organism in such a way as to derive nourishment from the tissues of the host |
| parasitising |
to be deriving nourishment from tissues of a host animal |
| parthenogenesis |
reproduction without fertilization, in which the zygote develops without the ovum being fertilized by a male gamete |
| parthenogenetical(ly) | referring to organisms developed by parthenogenesis (adverb) |
| patelliform | disc-shaped with a narrow rim |
| peat | dark brown organic deposit consisting of partly decomposed plant material usually associated with bogs and wetlands |
| pedicel | a stalk or stem supporting an organ or other structure in Insecta; the second antennal segment |
| pedipalp(i) | in spiders and other aracnids, a small paired leg-like appendage, immediately anterior to the walking legs (plural) |
| peduncle | any stalk-like structure supporting an organ or other structure in Hemiptera, basal segment of the antennae |
| pedunculate | structure positioned on, or attached by a slender stalk or peduncle |
| penellipse | the figure formed when a part less than the half of a uniserial circle of crochets is absent from the proleg |
| penes |
open, slit-like structures of the seminal vesicles to the outer surface |
| penultimate | descriptive of structure adjacent to the terminal segment of a body or appendage; the segment second from the end |
| pereonite | a segment of the pereon |
| pereon | thoracic division of the body |
| pereopod |
thoracic appendage used for movement, feeding and defense |
| periostracum | the external layer of most mollusc and brachiopod shells |
| peripneustic | having spiracles arranged all along sides of body, the usual condition in most insect larvae |
| peristalsis | series of successive waves of contraction |
| peristaltic | referring to peristalsis |
| petiolate | stalked, placed on a stalk |
| pharyngea | a pharyngeal sclerite |
| pharyngeal pouches | infoldings of endoderm between branchial arches in pharyngeal region of vertebrate embryos |
| photosynthesis | the use of light energy to produce nutrition for living organisms |
| phytoplankton | microscopic plant life found floating and drifting in large numbers in bodies of freshwater |
| piercer | a predator that captures and feeds by spiking the prey with modified mouthparts |
| pigment(ed) | a substance that gives a colour appearance (more heavily coloured) |
| pilosity | a covering of long, stout setae typically above small, fine, closely set setae |
| pimera | plural of pimeron |
| planispiral | coiled in one plane |
| plankton(ic) | microscopic plant or animal life found floating and drifting in large numbers in bodies of freshwater (referring to) |
| plastron | a film of air that is maintained in place along the body of an aquatic animal, for the purposes of underwater respiration, by a series of water repellant setae or cuticular modifications |
| pleon | an abdominal body division |
| pleonite | a segment of the pleotelson; a somite of the pleon |
| pleopod | abdominal appendage or swimming leg of crustaceans |
| pleotelson(ic) | body segment formed by the fusion of terminal abdominal segment(s) to the telson |
| pleura | plural of pleuron |
| pleurobranch | gill arising from lateral walls of thorax |
| pleuron | the lateral portion of the body between the dorsal tergum and the ventral sternum; lateral sclerite between dorsal and ventral portions of the thorax |
| plumose | feather-like; referring to antennae with long, ciliated processes on each side of each segment; referring to setae that have many branches |
| polygamy | males mate with many females |
| polygyny | males display for females, the best male gets to mate |
| polyp | an individual feeding or reproducing organism with tubular body and cytoplasm in Amoebae or amoeboid cells |
| pond | a body of standing water smaller than a lake |
| pool | a body of non-flowing water |
| porrect | extending forward horizontally |
| post- | situated behind; hindmost part of an organism |
| posterior | referring to, or situated toward the rear or anal end |
| posterolateral(ly) | descriptive of a structure toward the rear and side (adverb) |
| postmental | descriptive of a structure associated with the postmentum |
| postmentum | basal part of the labium |
| postmoult stage | the stage of the lifecycle directly after moulting when the soft exoskeleton stretches "to fit " the animal, before hardening |
| postocular | situated behind the eye |
| pre- | before, in space, time or degree |
| pre-apical(ly) | descriptive of a structure positioned before the apex of another structure |
| predaceous | referring to an animal that typically sustains life by preying upon (eating) other organisms |
| predate | to kill another animal for food |
| predation | a type of behaviour where one animal eats another |
| predator | an animal that overpowers, kills and consumes other animals |
| prehensile | descriptive of a structure adapted for grasping, holding or seizing |
| premental | descriptive of a structure associated with the prementum |
| prementum | the stipital region of the labium, containing the muscles of the palpi and the ligular lobes, and giving insertion to the cranial muscles of the labium |
| premoult stage | stage before moulting |
| pro- | first |
| proboscis | in Insecta, any extended or extendable mouth
structure in Nemertea, muscular trunk-like appendage of the head end |
| process | any projection from a surface, margin or appendage |
| processes | may be used to refer collectively to gills, filaments and projections i.e. terminal processes or caudal processes |
| proctiger | small papilla or conical structure that bears the anus |
| profemur | femur of the foreleg (first leg) |
| prognathous | with mouthparts projecting forwards; in lateral aspect the primary axis of the head is horizontal |
| projection | something jutting out at an angle from a flat surface |
| proleg | unjointed abdominal or thoracic appendage |
| prolonged | extended or lengthened beyond ordinary limits |
| pronotal | referring to a structure on the pronotum |
| pronotum | the upper or dorsal surface of the first thoracic segment |
| propleuron | lateral portion of prothorax |
| propodal | referring to the propodus |
| propodi | plural of propodus |
| propodus | second segment of a pereopod or maxilliped, counted from the distal end |
| prosternum | ventral area between the forelegs |
| protandric | having male sex organs while young and then femal sex organs later in life |
| prothorax | the first thoracic segment, bearing forelegs but not wings or wing pads |
| protopod | synonomous with protopodite |
| protopodite | the basal piece of a segmented appendage |
| protrusible | descriptive of something capable of being protruded, or put out |
| protuberance | any elevation above the surface of which it is apart, typically a rounded extension from a flat surface |
| protuberant | descriptive of a conical or mound-like rising above the surface or general level |
| proximad | toward the proximal end of a stucture or an appendage |
| proximal | the portion of a segment nearest the body or connection with the body |
| pseudobranch | a conical extension of the epithelium used in respiration; |
| pseudopod(ia) | soft, flexible foot-like appendage (plural) |
| pubescence | state of being pubescent |
| pubescent | covered with soft, short, fine, closely set setae |
| punctured | with small impressions on the hard outer surfaces |
| pupa(e) | a phase of complete metamorphosis, when larval features are destroyed and adult features are constructed |
| pupal | referring to the pupa |
| pupate | to become a pupa |
| pupation | the act of becoming a pupa |
| pyriform | pear-shaped |
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| radula |
a chitinous membrane in the mouth of gastropods, set with numerous minute horny teeth |
| rami | plural of ramus |
| ramus | branch-like division of any structure or appendage |
| raptorial | descriptive of legs adapted for seizing prey, typically with modified tibiae and tarsi |
| reflexed | bent up or back |
| retreat | a shelter made by spinning a silk net across a gap or depression in a log or rock |
| retractile | descriptive of any structure that is capable of being advanced forward and retracted backward |
| rhynchocoel | cylindrical cavity in body that houses the proboscis when it is not extended |
| riffle | shallow section of a river or stream, typically the surface is rippled by current passing over stones and irregularities in the substrata |
| riparian | descriptive of organisms inhabiting river banks, typically vegetation |
| river | a naturally occurring freshwater drainage which is larger than a stream |
| riverine pool | a pool located in the river channel but out of the main flow |
| rostral prong | a structure rising from the side of the rostrum |
| rostrum | a jointed snout-like projection from ventral surface of the head formed by a labial sheath enclosing the maxillary and mandibular stylets |
| rugose |
referring to a surfaces covered with wrinkles |
| rugosite | a structure that is strongly rugose |
| runnel | a small channel of water |
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| saccoid |
sac-like |
| saline | salty, of water |
| sanguivorous | referring to invertebrates that are blood eating |
| saprophagous | descriptive of organisms that feed upon dead and decaying animal or plant matter |
| saprophytic | an organism that feeds upon dead organisms or decaying organic matter |
| scape | basal segment of the antennae |
| scavenger | an animal that feeds on dead and decaying animal or vegetable matter |
| scent evaporatorium | opening in the abdominal terga, related to scent production |
| sclerite | any hard portion of the integument |
| sclerotin | tough proteins that are resistant to chemical and physical degradation |
| sclerotized | the integument is hardened and darkened in definite areas by deposition of, or formation, of sclerotin |
| sclerotization | the physiochemical process by which sclerites are formed |
| scraper | consumers of algae and associated material attached to the surface of submerged plants or rocks |
| scutellum | triangular part of the mesothorax, generally placed between, sometimes overlapping, the bases of the hemelytra |
| secretion | a fluid or substance passed through a duct, membrane or aperture |
| seepage | the slow oozing of groundwater out on to the earth's surface |
| segment | a natural subdivision of the body or appendage |
| segmented | having segments |
| self fertilization | the fusion of male and female gametes from the same parent individual |
| semi-aquatic | growing or living close to water, sometimes found in, or entering water |
| seminal vesicle | pouch-like portion of the male reproductive system where spermatozoa are stored |
| sensillum | a simple sense organ or sensory receptor |
| sensory pit | a deep pit or puncture through the surface of the integument, which may bear pegs, bristles or setae, open or covered by a membrane |
| serrate | saw-like; descriptive of a structure with conical or tooth-like processes along an apical margin |
| sessile | any structure or appendage that broadly attaches at the base without constriction; an organism lives attached to the substratum |
| seta(e) | bristle-hair-like cuticular projection (plural) |
| setal | referring to, or descriptive, of the setae |
| setation | the state of having setae |
| setobranch(ia) | a tuft of setae attached to gills (plural) |
| setose | a surface, structure or appendage covered with setae |
| setule | small, short seta, hair or bristle |
| shredder | consumes coarse particulate organic matter, eg. wood, bark, leaves |
| silt | unconsolidated sediment of fine mud (<0.16 mm diameter) |
| sinistral | pertaining to or positioned on the left side of the body |
| sinuated | descriptive of structures which are long and narrow with a winding or wavy form |
| siphon | any tubular external process or structure |
| skater | glides or skates over water surface |
| snag | a tree or part of a tree held fast in the bottom of a river forming an obstruction or diversion of the water flow |
| somite | in Insecta, body segment of an adult in Crustacea, segement of the body, can be differentiated into dorsal tergite and ventral sternite |
| species | the primary biological unit |
| spermatophore | a capsule that surrounds spermatozoa |
| spermatozoa | male gamete |
| spicule | any minute, pointed process or spine |
| spine | stiff, sharp, tapered process on the surface of a plant or animal |
| spinneret | a hollow spine, connecting to silk glands, by which cases, retreats or cocoons are spun |
| spinose | descriptive of a structure or body covered with spines |
| spinulate | set with little spines or spinules |
| spinule | a very small spine |
| spiracle | a pore, hole or aperture in the integument which allows gas exchange for respiration |
| spiracular | descriptive of or referring to the spiracles |
| spire | the whorled part of a spiral shell |
| splash zone | zone of a waterfall aside from the main flow of water but which may be wetted by spray |
| sprawler | stretched out, usually on substrate |
| statoblast | a specialized asexual bud enclosed in a chitinous shell that remains dormant over winter then develops into a new colony in spring |
| statocyst | a sense organ responsible for maintaining equilibrium and orientation |
| statolith | a sand grain-like structure found in a statocyst |
| stemma(ta) | a tubercule bearing an antenna (plural) |
| sterna(l) | plural of sternum (referring to the sternum) |
| sternite | a sclerotized or hardened subdivision of a sternum |
| sternum | the entire ventral portion of any ring-like body segment |
| stipes | second segment of the maxilla |
| stipital | descriptive of, or referring to the stipes |
| stream | a course of running water; general term that includes rivulet, brook, river |
| striate | descriptive of integument surface that is sculptured with numerous parallel, fine, impressed lines |
| strider | an animal that moves across the water's surface by repeatedly spreading and drawing in its long legs |
| stridulate | to make a creaking, grating or hissing sound by rubbing two ridged or roughened surfaces against each other |
| stridulation | a creaking, grating or hissing sound that is made by rubbing two ridged or roughened surfaces against each other |
| stridulatory combs | ridged or roughened surfaces that can be rubbed against each other to make a creaking, grating or hissing sound |
| stylet | a structure for cleaning antennae, at junction of tibia and tarsus on first leg of certain insects small, pointed, bristle-like appendage |
| styli | plural of stylus |
| stylus | a small pointed, non articulated process |
| sub- | under, less than, not complete |
| subalar | referring to structure positioned below the wings |
| subimago | stage between the aquatic nymph and reproductive adult |
| subpedunculate | not quite pedunculate |
| substrata | plural of substratum |
| substratum | the solid base of a waterbody, ususally described in such terms as rocky, sandy, gravelly, silty |
| subterranean | beneath the surface of the ground |
| sucker | an organism that sucks, a part or organ adapted for sucking nourishment or for adhering to an object as by suction |
| suctorial | mouthparts adapted for sucking |
| sulcus | a furrow or groove |
| sulcate | groove-shaped; descriptive of a surface which is deeply grooved or furrowed |
| sulcation | having deep grooves or furrows |
| supra-orbital | referring to a position above the eyes |
| suspension feeder | an animal that feeds of fine particles suspended in the water column by filtering water through a spun net or net-like feeding appendage |
| suture | a seam-like anatomical feature which serves as a boundary to separate distinct body parts |
| swamp | an ecological habitat or area characterized by wet, spongy land usually covered with water |
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| tarsal |
descriptive of or referring to the tarsi |
| tarsi | plural of tarsus |
| tarsus | a jointed appendage basally attached to the tibia, bearing claws or other structures |
| taxa | plural of taxon |
| taxon | any definite entity of classification formally recognized by taxonomists |
| taxonomic level | referring to a classification type (species, genus, family, order, class, phylum, kingdom) |
| tectiform | descriptive of a structure that is sloping from a medial ridge |
| telson | terminal part of the juvenile abdomen |
| tentacle | a flexible organ of touch |
| terga | plural of tergum |
| tergite | a sclerotized subdivision of a body tergum |
| tergum | the upper or dorsal surface of any body segment |
| terminal processes | may be used to refer collectively to gills, filaments and projections located at the posterior end of the body |
| terminal proleg | unjointed abdominal appendage located at the posterior end of the body |
| terminalia | terminal abdominal segments modified to form the genital segments |
| terminally | located at the end of a body, appendage or structure |
| terrestrial | living on or in the land |
| thoracic | referring to the thorax; descriptive of structures attached to the thorax |
| thoracomere | somite of thorax; thoracic somite, the first two of which are incorporated into the head and bear the maxillipeds and chelipeds respectively |
| thorax | second of the three divisions of the whole animal (head, thorax, abdomen) |
| tibia(e) | fourth segment of the leg (plural) |
| trachea(e) | an elongate respiratory tube (plural) |
| tracheole | smaller tubes than tracheae |
| transverse | referring to structures that are wider than long |
| tributary | a smaller river or stream which contributes its water to a larger river at any point along the river course |
| trichobothria | seta bearing spots |
| trickle | a small, gentle flow of water |
| tridentate | referring to structures with three tooth-like projections |
| triquetral | triangular in sections; with three flat sides |
| trochanter | small second segment of leg, between coxa and femur |
| trochantin | a small sclerite at the base of the leg |
| trophic level | the level of a group of organisms in the food chain, typically defined by the method of obtaining food |
| tubercle | a small rounded protuberance |
| tumid | referring to bodies or structures which are swollen or enlarged |
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