GLOSSARY FOR INVERTEBRATE CONFUSION
This glossary, to be used with the 4th edition of "Invertebrate Zoology" by R. D. Barnes (1980,
W. B. Saunders Co.), was compiled as a labor of love to fill what seemed to a former student to
be a considerable gap in the chain of information from text to reader. It makes no pretense to
include every scientific term. Those which are in common use as well as obvious ones, i.e.
circum pharyngeal, dorso- or ventro lateral, were deliberately omitted.
It is hoped that it will clarify or ease the path to the understanding of the vocabulary of
invertebrate study.
Irving Leving
PREFIXES AND SUFFIXES
L., Latin; G., Greek
a, ab (L) away, from
a, an (G) not, without
acanth (G) thorn, spine
actin (G) a ray
ad (L) toward, near
alveol (L) pit
ampho- (G) both, double
ape, apo- (G) away from
archeo- (G) beginning, first in time
athro- (G) joint
bi-, bio- (G) life
blast- (G) bud, sprout
brachi- (G) arm
brachy- (G) short
branchi- (G) fin, feather
bucc- (G) the cheek
calie- (x) (G) cup
capit- (L) head
caud- (L) tait
cephal- (G) head
cerc- (G) tail
ceno- (G) new, recent
chaet- (G) hair
choan- (G) funnel, tube
-chord (G) gut, string
chrom- (G) color
coel- (G) hollow
cten- (G) comb
cutis- (L) skin
cyto- (G) hollow, cell, vessel
de- (L) down, away from
dent- (L) tooth
derm- (G) skin
de-utero- (G) second
di- (G) double, two
duct (L) a leading, conducting
e, ex (L) out, without, from
ect- (G) outside
end- (G) within
enter- (G) bowel
ep(i)- (G) on, upon, over
eu, ev- (G) good, true
-eury (G) broad
fer (G) carrier of
fil (L) thread
gaster (G) belly
glob (L) ball
glom, glomer (L) ball of yarn
gnash (G) jaw
gul (L) throat
gymn (G) naked
gyr (G) round, circle
haem (G) blood
hal (G) the sea
hemi- (G) half
hetero (G) other, different
hist- (G) web, tissue
hal- (G) whole, entire
homo- (G) alike
hypo- (G) under
hyper- (G) above, beyond
in (L) in, into, not, without
is-, iso- (G) similar, equal
lecith- (G) yolk
loph- (G) ridge, crest
lumen (L) light
macr (o) (G) large
mela (G) black
mere (G) a part of
meso (G) middle
mete (G) next to
mio (G) less
micr (o) (G) small
mon (o) (G) one, single
morph (G) shape
nect (G)
neo (G) new, recent
not (o) (G) the back
odont (G) tooth
oligo (G) few
omm (L) all
opercul (L) cover, lid
opisth (G) behind
orth- (G) straight
paleo (G) ancient
par (a) (G) beside
pectinate (L) comb-like, having tooth-like projections
peri (G) around, near
phag (G) to eat
phil (G) loving, friend
phor (G) to bear
phot (G) light
phyl (G) tribe
pinaco (G) board, tablet
platy (G) broad
plio (G) more
pod (G) foot
poly (G) many
poro (G) hole, passage
post (L) after, behind
prim (o) (L) first
pro (G) before, in front of
prove (G) forward, in front
proto (G) early
pseud (o) (G) false
pulmo (G) lung
pyg- (G) rump
ram (L) branch
retro (L) backwards
rhin (G) nose
rhinch (G) beak, snout
sarc (G) flesh
scler (G) hard
som (e) (G) body
squam (G) scale
steg (G) roof
sten (G) narrow, straight
stom (a) (G) mouth
styl (e) (G) pillar, column
sub (L) under, below
super (L) above, over
syn, sym (G) together
tele (G) far
teleo (G) perfect, entire
tetr (G) four
thee (G) case, container
therm (o) (G) heat
trem (G) a hole
tri (G) three
trich (G) hair
trop (G) a change, a turn
troph (G) a feeding, one who feeds
vas (L) vessel
ventr (L) belly
zoe (ie) (G) life
zyg (G) yolk, a coupling, linkage
VOCABULARY
A
Acanthocephala(G. akantha, thorn + kephale, head). A phylem of parasitic worm-like pseudo
coelomates.
Acanthor (der. see above). Larval form of above.
Acoelomate (G. a, without + coel, hollow). Animals which lack a body cavity and a solid type of
body construction.
Acontium (G. Aconto, spear, javelin). In polyps, a mesenterial filament which projects into the
gastrovascular cavity and produces enzymes for digestion of food.
Acron (G. akron, top, summit, peak). The unsegmented head (prostomium) of annelids.
Actinula (G. acting, rod, beam). A larval form of hydroids
Aerobe (G. aero, air + bios, life). An organism which requires air or oxygen for life.
Aesthetes (G. aisthetikos, sensitive, perceptive). In chitons, mantle cells lodged in the tegmentum
which act as sensory organs.
Ambulacral area (L. ambulacrum, walk). Five sections of the oral area of echinoderms which
contain podia.
Ambulacral grove. A furrow extending from the mouth of echinoderms; in a sterodia along each
arm.
Amictic (G. a, not + mixtos, mixed). A thin-shelled diploid egg which cannot be fertilized and
develops by parthogenesis into an amictic female.
Amphid (G. amphi, around, double). An inervated invagination of cuticle in nematodes.
Ampulla (L. flask, bottle). Bulb at end of lateral canal in astroida.
Anabiosis (G. + bios, life). Inactivity accompanied by water loss and very low metabolic rate.
Also cryptobiosis (G. Kryptos, hidden, concealed + bios, life).
Anaerobe (G. an, not + bios, life). An organism which cannot exist in the presence of air or
oxygen.
Anastomose (G. anastomosis, new outlet, new network). Connection between two vessels or
hollow organs.
Annulus (L. annulus, ring). A spiraled transverse groove of dinoflagelates. If a simple ring, it is
termed a girdle.
Apodeme (G. apo, from, off, away + demas, body). Projection of procuticle of exoskeleton
muscle attachment in crustaceans.
Aposematic (G. apo, from, off, away + sema, sign, token). Warning coloration.
Archenteron (G. archea, beginning, first cause + enteron, intestine). Pouch formed by
invagination of blastula to form primitive gut.
Archeocytes (G. arche, beginning + cyte, cell, hollow place). Phagocytic cells found in the
mesohyl of spongia.
Articular membrane (L. articulus, joint). A thin, chitinous membrane joining segments of the
arthropod body.
Ascus (G. asco, bladder, bag). A space under the frontal plate which provides, with muscles, the
means of protruding the lophophore of bryozoans.
Atrium (L. vestibule, hall). The interior cavity of asconoid sponges.
Autogamy (G. autos, self + gamete, husband, wife). Self mixing of genetic material within the
individual.
Autotomy (G. autos, self + temno, cut). The act of casting off an appendage.
Autozooid (G. autos, self + zoe, life). An individual feeding bryozoan.
Avicularium (ia, pl.) (G. avis, bind). A heterozoid in the form of a pincers or jaw which serve to
protect the organism.
B
Basopodite (G. basis, pedistal, foundation + pod, foot). A/crustacean appendage process attached
to the coxapodite and which bears the endo- and exopodites.
Bdelloid (G. bdelo, leech + oid, like, having the appearance of).A class of fresh water rotifers.
Benthic (G. benthos, deep). Bottom dwelling organisms.
Biramous (L. bi, two + ramus, branch). Two branched; Sometimes extended to cover more than
two.
Blastula (G. blastos, germ, bud, sprout). The early developmental stage of a metazoan; a
spherical layer of cells enclosing a central cavity.
Blastomere (G. blastos, germ, bud, sprout + mere. a part). A cell produced during cleavage of an
ovum; a blastula cell.
Blastozoid (G. blastos, germ, bud, sprout + zoe, life). A reproductive bud of tunicates.
Book gills. Leaf like lamellae of Limulus which serve as organs of gaseous exchange i.e. gills.
Brachiole (G. brachion, arm). A slender pinnule-like projection which contains the peripheral end
of the food groove of fossil crinoids.
Buccal (L. bucca, cheek, cavity). A cavity just within the mouth opening .
Budding - See fission.
C
Calyx (G. Kalyx, cup, cover). The body, as differentiated from the stalk, of an ectoproct; the
skeletal cup within which a polyp is fixed (scleractinian corals).
Capitulum (L. capitalis, relating to the head). In stalked Cirripedia, the main body, excluding the
stalk).
Carapace (Sp. carapach(o), shield). A chitinous exterior structure covering the crustacean thorax
minimally and sometimes the whole body.
Cecum, caecum (L. caecum, blind). A pouch or sac within the body which has only one opening.
Centrolecithal (G. Kentron, mid point + lecitho, yolk). An ovum in which the nucleus is
surrounded by a small amount of nonyolk cytoplasm within a large yolk mass.
Cephalon (G. cephalo, head). The interior body of trilobites.
Cerata (G. Keratos, horn). Dorsal body projections of nudibranchs.
Cercaria (New Latin). The fourth developmental stage of trematodes i.e. a free-swimming tailed
tadpole-like form.
Chelicerae (G. chele, claw) . Claw-like feeding appendages of chelicerates (eg. horseshoe crabs).
Coanocyte (G. coane, funnel + cyto, cell). Spongia cells which are flagellated and collared which
create water currents and extract food from them.
Chloragogen (G. ehlor, green + agogue, stimulating). A substance in cells which serves as a
center for glycogen and fat synthesis in oligochaetes.
Chromatophores (G. chrom, color + phore, bearer). Pigment cells in cephalopods.
Cilium, pl. cilia (L. eyelash, hair). A hair-like projection of the cell wall used for locomotion or
current generation.
Cirri (L. cirrus, curl, tendril)
1. In crinoids, small, jointed appendages attached of the stalk.
2. In Cirripedia, thoracic feeding appendages.
3. In Ciliata, ciliary tufts used for locomotion.
4. In polychaetes, a sensory appendage.
5 . In trematodes and neohabdocoels, an eversible copulatory organ.
Clavules (L. clavus, nail). Specialized spines of Echinoideae. They are believed to produce
mucus for burrow maintenance and to create water currents.
Clitellum (L. clitella, pack saddle). A glandular segment of oligochaetes and hirudinates which
forms a reproductive cocoon.
Cnidosac (G. Knide, nettle + sakkos, bag). Structures at the tip of cerata of nudibranchs which
contain nematocysts.
Cnidocil (G. Knide, nettle + cdl, deriv. unknown). A short bristle-like process on the end of the
cnidocyte which triggers the discharge of nematocysts.
Cnidocyte (G. Knide, nettle + cytos, cell). Cells which contain stinging structures (nematocysts).
Coanenchyme (G. coeno, common + chymos, juice). In octocorallians, a mass of mesoglea which
has gastrodermal tubes connected to adjacent polyps.
Colloblasts (G. collo, glue + blastos, ball). In ctenophores, cells which have adhesive properties
and which are analagous to nematocysts.
Columella (L. dim. columella, pillar). Central column of the shell of gastropods.
Commissure (L. committere, to bring together). A band of fibers joining symmetrical parts,
especially in the brain.
Condyle (L. condylus, knuckle, knob, enlarged end of a bone). A cuticular knob which engages a
socket and permits movement between body segments of arthropods.
Conjugant (L. con, with + jugum, yoke, pair). Fused ciliates.
Contractile vacuole. Water balancing organelle.
Coracidium (G. Korak raven, deriv?)1. Early larval stage of turbullarians. 2. Also an
onchosphere.
Coxa (L. hip). The basal section of the leg of chilicerates and insects.
Coxal gland (L. coxa, hip). Thin walled sacs which serve as excretory organs of chilicerates.
Coxapodite (L. coxa, hip + G. pod, foot). The crustacean appendage process nearest the body, to
which the basopodite is attached.
Crown (L. crone, crown, wreath). The pentamerous body of a crinoid.
Cyclomorphosis (G. cyclo, circle + Morpho, shape, form). A seasonal change in body shape or
proportion.
Cyclosis (G. cyclo, circle). Streaming protoplasm in amoba.
Cysticercus (G. cyst), bladder + New Latin, cercaria, tadpolelike). The second stage of
development of cestodes; pre-adult stage.
Cytoplasm (G. cyto, cell + plasma, substance). The material contained within the cell wall.
Cytostome (G. cyto, cell + stom, mouth). Mouth or oral chamber of ciliates.
Cytopyge (G. cyto, cell + pygo, rump, buttocks). Anal opening in ciliates.
D
Dactylozooid (G. dactylo, finger + zoe, life). Specialized defensive polyp in hydrozoans.
Demibranch (L. dimidius, half + branchos, gill). One of a pair of lamelli branch gills.
Deutocerebrum (G. deutos - double + L. cerebrum, brain). The median region of the brain of
arthropods.
Digenea (G. di, twice, two + genesis, birth, origin). A parasitic organism whose life cycle
involves two or more hosts.
Dioecious (G. di, twice, two + oeco, house). An organism which produces either male or female
gametes, but not both.
Ditaxic (G. di, twice, two + tasso, place arrange). A fine muscular contraction which sweeps
across half of the foot of some molluses (gastropods).
Diverticula (L. diverticulum, a by-path). In anatomy, a pouch or sac opening out from a tube or
cavity.
Dorsal lamina (L. dorsum, back + lamina, plate). A projecting ridge of finger-like processes
(languets) which run from the pharynx to the esophagus in tunicates.
E
Ecdysis (G. ekdysis, escape, molt). The shedding of arthropod skeleton.
Ecdisone (G. ekdysis, escape, molt). Hormone which causes ecdysis.
Echinoplutens (G. echinos, sea urchin + L. pluteus, shield, parapet). The second and planktonic
larral stage of echinoderms.
Elytra (G. elytron, shield, husk). Plate-like scales.
Ectoplasm (G. ecto, out of + plasm, substance). Outer portion of cytoplasm of cells.
Endoplasm (G. endo, within + plasm, substance). Inner portion of cytoplasm of cells.
Endopodite (G. endo, within + pod, foot). Appendage process which is attached to basopodite of
crustaceans.
Endostyle (G. endo, within + stylos, pillar, column). In tunicates, a deep groove which extends
the length of the pharyngeal wall which contains mucus secreting cells and flagellae.
Entolicithal (G. ento, within + licitho, yolk). An ovum which has the yolk as an integral part of
the cytoplasm.
Entoproct (G. ento, within + proktos, anus, rectus, tail). Sessile bryozoan-like animals with the
mouth and anus within the tentacular crown.
Ephyrae (Deriv. unknown). Immature medusae.
Epiboly (G. epibole, to place upon, throw). In histology, overriding or surrounding other cells in
development.
Epicardium (G. epi, on, over, upon + Kardia, heart). In tunicates, a tube which parallels the
digestive loop.
Epicuticle (G. epi, on over, upon + L. cutis, skin). The exterior portion of the chitinous arthropod
skeleton.
Epiphytic (G. epi, on, over, upon + phytos, plant). Concerning plants which grow non-
parasitically on others.
Epipodite (G. epi, on, over, upon + pod, foot). Appendange process which is attached to, or is
apart of, the coxapodite of crustaceans. It frequently bears gills.
Epistome (G. epi, on, upon, over + stome, mouth). A narrow crescent fold which overhangs the
mouth of phoronids.
Epitheliomuscular cells (G. epi, on, over, upon + there, nipple; + L. musculus, flesh). In hydra,
epithelial cells which have basal extensions connected to each other and which are contractile.
Epitoke (G. epi, on, over, upon + toco, birth, offspring). An annelid reproductive individual
adapted for bottom dwelling or pelagic existence.
Epitoky (See above). The formation of an epitoke.
Epizoic (G. epi, on, upon, over + zoon, animal). An external parasitic form.
Esthetases (G. aisthetikos, sensitive, perceptive). Chemoreceptors on the first antennae of
copepods.
Eukaryote (G. eu, good, well + caryo, nut, kernel). A cell whose nucleus is enclosed within a
membrane, a characteristic of all life above the level of bacteria and blue-green algae.
Eumellibranch gill (G. eu, good, well + L. lamina, plate + G. branchos, gill, fin). Molluscan gills
which have formed solid sheets of tissue.
Eutely (G. euteleia, thrift, economy). A condition of some aschelminths in which the body is
made up of a constant number of cells for each species.
Exopodite (G. exoterikos, external + pod, foot). An appendage process which is attached
externally to the basopodite of crustaceans.
Exumbrella (L. ex, out of + umbra, shace). The exterior upper surface of a medusa.
F
Facultative (L. facultas, feasibility, means). Having the ability to live under more than one
environmental condition i.e. parasitic or non-parasitic.
Fillibranch gills (I.. filix, fern + G. brachos, gill, fin). Molluskan gills in which the individual
filaments are more or less separate.
Filopodia (L. glum, thread + G. pod, podium. foot). A pointed pseudo-podium.
Fission (L. cleft, chink). Formation of daughter cells by division:
a. Binary if result is two similar cells
b. Budding if result is two dissimilar cells
c. Schizogony if result is multiple division
Flabellum (L. fan). Spatulate process on last leg of Limulus used to clean gills.
Flagella (L. flagellum, small whip, lash). A long slender motile appendage of cells.
Funiculus (L. funds, rope, cord). Tissue which connects individual bryozoans through pores and
which provides some sort of communication .
Flame cell. The protonephridium of turbellarians. See text (Barnes, pages 220, 221 and 222).
G
Gametamy (G. gametos, wife, husband, spouse). Sexual reproduction
Gametogonia (G. gametos, spouse + gone, seed). Primary gametodytes which are shed into the
coelom of polychaetes.
Gamete (G. gametos, spouse). Reproductive cell.
Gamont (G. gamos, union). A gametocyte which is the precursor to a gamete. (See gamogony).
Gamogony (G. gametos, spouse + gonad, seed). The development of gametes.
Ganglion (G) A knot or plexus of nerves.
Gastrodermis (G. gastro, stomach + derma, skin). Nutritive muscle cells of cnidarians and
ctenophores.
Gastrovascular cavity (G. gastro, stomach + vas, vessel, pouch). A space or channel for digestion.
Gastrozoid (G. gastro, stomach + zoid, life-like). Hydrozoan feeding polyp; food gathering
individual in colonial tunicates (trophozoite).
Gastrula (G. gastro, stomach). A cup-like early stage of germ layer formation characterized by
two layers of cells.
Gemmules (G. gemma, bud, eye). A spore-like aggregate of sponge material which winters over
and grows into a larva in the spring.
Girdle (Anglo-Saxon, gydrdel, belt). In polyplacophorans, the peripheral area of the mantle.
Gonophore (G. gone, seed + phore, bearer, carrier). The repro ductive structure of a polyp (See
medusa).
Gnathobase (G. gnathos, jaw + basis, foundation). Heavily armed processes at base of
appendages for grinding food in Limulus.
Gnathopods (G. gnathos, jaw + pod, foot). The 2nd and 3rd appendages of amphipods which are
modified for prehension.
H
Hectocotylus (G. hecto, hold + Koides, hollow). A cephalopod arm modified as a reproductive
organ.
Hemocoel (G. haima, blood + coelo, cavity, cup). In arthropods, a sinus or space filled with
blood.
Hemocyanin (G. haima, blood + cyano, dark blue). The oxygen carrying component of the blood
of arthropods, cephalopods, crustaceans and mollusks.
Heterozoid (G. heteros, other, different + zoe, life). A modified bryozoan individual which serves
many different functions i.e. stolous, attachment discs, etc.
Hologamy (G. holo, entire + gamos, union). Fusion of two individuals, each acting as a gamete.
Holophyte (G. holo, entire + phyto, plant). The form of life able to create nutriments out of water,
minerals and lignt.
Holozoic (G. holo,entire + zoon, animal).
Homologous (G. homologos, agreeing). Corresponding in type of structure and deriving from a
common primitive origin.
Homology - The state of being homologous.
Hydranth (G. hydra, many headed + anthus, flower). The oral end of a polyp.
Hydrocaulus (G. hydra, many headed + L. caulis, stalk). The stalk of a polyp.
Hydrotheca (G. hydra, many headed + theca, case, container). The continuation of the perisarc of
hydroids which encloses the hydranth
Hydrorhiza (G. hydra, many headed + rhizo, root). Root-like structure at the base of a polyp.
Hypertrophy (G. hyper, very, above + trophe, food, growth). Excessive growth.
Hypertonic (G. hyper, very, above + tongs, stretching). A medium with high osmotic pressure.
Hypodermis (G. hypo, under, beneath + cerma, skin). In arthropods, the underlying layer of
integumentary epithelial cells.
Hypostome (G. hypo, under, beneath + stoma, mouth). The mouth of a hydra.
Hypotonic (G. hypo, less than, under, beneath + tongs, stretching). A medium with low osmotic
pressure.
I
Instar (L. form, likeness). Stages between growth periods in arthropods.
Intralecithial (L. intra, within + G. lecitho, yolk). Superficial cleavage of arthropod eggs.
Interstitial (L. interstitium, interstice). Situated between the cellular components of tissue;
specifically between the epidermis and epithelio-muscular cells of hydras.
Introvert (L. intra, within + versus, turn). The head and anterior part of the body of
pogonophorans which can be retracte into the body.
Iridocycle (G. irid, rainbow, iris + Kylon, area under the eye). Cells in the chromatophores of
cephalopods which reflect light differentially.
Isogamy (G. iso, the same + gamete, spouse). The fusion of two gametes with the identical
genetic material.
Isomyarian (G. iso, the same + L. mya, a kind of mussel). A primitive lamellibranch in which the
adductor muscles are more or less equal.
K
Kinetosome (G. Kinetico, pertaining to motion + some, body). Organelle to which the base of the
cilium or flagellum is attached.
L
Labial palp (L. labium, lip + G. palpo, touch, feel). Flap-like folds associated with proboseides
which act as food sorting stru tures.
Labium (L. lip). The lower lip of arthropods.
Labrum (L. lip). The lip-like upper prominence of mouth parts of chewing insects.
Lamellibranchea (L. lamella, plate + G. branchos, lung). See pelecypod.
Lappets (Mid. Eng. lappe, fold, wrap). Movable plates on ambulacral groove of crinoids, each
associated with three podia.
Lamellibranchea (L. lamina, plate + G. branchos, gill, fin). Mollusks having 2 valves hinged
dorsally and with sheet-like gills having a food gathering function. Symon. bivalves, pelecypods.
Lamella (L. lamina, plate).
a. Folded filament half of molluskan gill
b. Leaf-like folds of gills of chelicerates (book gills).
Lanquets (Deriv. unknown). Finger-like processes which run posteriorly to the esophogus of
tunicates.
Lecithotrophic (G. lee, tho, yolk + trophe, food, nourishment). Developing forms which receive
their nourishment from yolk.
Lobopodia (G. lobos, a rounded protuberance + pod, foot). A blunt pseudopodium.
Locular (L. loculus, cell, box). A chambered body.
Lophophore (G. lopho, mane, crest + phore, bearer, carrier). A food capturing organ consisting of
ciliated tentacles which are found on phoronids, bryozoans and brachiopods.
Lorica (L. lether cuirass or corselet). The shell, test or thickened encasement of bdelloid rotifers.
Lumen (L. light, window). In biology, a duct, hollow or enclosed space.
Lunules (L. dim. of luna, moon or crescent). Large elongated notches or openings in the body of
some echinoderms.
Lysosome (G. Blysis, dissolve, break up + some, body). A cellular organelle containing digestive
enzymes.
M
Madreporite (Deriv. unknown - perhans Spanish madre, mother + G. poros, hole). A modified
pore V in the aboral surface of some echinoderms. [which connects to water channels.]
Malpighian tubules (Malpighi, Italian anatomist who discovered capillaries + L. tubus, pipe).
Slender tubes which carry wastes from the diverticula to the intestine.
Mandible (L. mandibula, jaw). Short, heavy mouth parts of crustaceans used for biting and
grinding.
Mantle-palium
a. In bivalves and brachio pods, a sheet of muscular, sensory and secreting tissue lying
beneath the valves.
b. In cephalopods a muscular structure surrounding the body. c. In barnacles, the
enveloping carapace of larval forms.
Manubrium (L. handle, haft). A scyphoran structure which hangs from the subumbrella and
surrounds the mouth aiding in capture and ingestion of prey.
Marsupium (G. marsupion, pouch, bag). In amphipods a brood chamber which holds the eggs.
Mastax (G. mouth). The mouth of a rotifer.
Mastigophora (G. mastigo, whip + phore, bearer, carrier). Zoo or phytoflagellales which have
flagellae.
Maxillae (L. jawbones). Pairs of feeding appendages of crustaceans.
Maxillipeds (L. jawbone + G. pod, foot). The first three appendages on the thorax of
malacostrans which have been modified to manipulate food.
Medusa (L. a gorgon). A free swimming bell or umbrella shaped cnidarian.
Medusoid (L. a gorgon). In hydra, a free swimming reproductive form which develops into a
medusa or is retained as a gonophore.
Mesenchyme (G. meso, middle + chymos, juice). Cells which develop into connective tissue,
blood and blood vessels.
Mesenteron (G. meso, middle + enteron,- intestine). The central part of anthozoan gastrovascular
cavity.
Mesentery (G. meso, middle + enteron, intestine). A supporting or enfolding membrane which
attaches organs to the body wall or other organs.
Mesoglea (G. meso, middle, glia, glue). The thick gelatinous material making up the major part
of the inner body of medusae.
Mesohyl (G. meso, middle + hylister (?), sieve). A gelatinous matrix lying below the pinacoderm
in spongia.
Metachronal (G. meta, between, after + chronos, time). Wave-like beating of fields of cilia or
flagellae.
Metamerism (G. meta, between, implying change + meris, share portion -pernaps indicating
change from acoelomate to coelomate body archetecture). Division of body into segments along
an amteropostorior axis.
Metanephridium (G. meta, between + nephro, kidney). The nephridium in which the preseptal
end is an open ciliated funnel.
Metazoan (G. meta, between + zoon, animal). A multicellular motile heterophic animal.
Mictic egg (G. mictos, mixed). A haploid egg which produces males parthogenically if not
fertilized. If fertilized, they become dormant after which they develop into females.
Monoecious (G. mono, single + oeco, house).- An individual which produces male and female
gametes.
Monogenea (G. mono, single + genesis, birth, origin). A parasitic organism having only one form
or generation in the life cycle.
Monoplacophora (G. mono, single + placo, tablet + Phore, bearer, carrier). A class of mollusks
having a single symmetrical shell.
Monopodal growth (G. mono, single + pod, foot). In hydrozoans, growth at the distal end of the
stalk with lateral branching of secondary polyps. The oldest polyp and its hydranth occupy the
tip.
Monotaxic (G. mono, single + tasso, arrange, place). A fine muscular contraction which sweeps
synchronously across the whole surface of the foot of gastropods.
Myogenic (G. myo, muscle + genesis, birth, origin). Muscle contraction which originates and is
controlled within the muscle itself.
Myonemes (G. myo, muscle + nema, thread). Long contractile fibrils in ciliates.
N
Nauplius larva (Der. unknown). Earliest larval form of crustaceans - basic crustacean type.
Nematocyst (G. nemato, thread + cystos, cell). Toxic stinging structures carried by cnidocysts in
hydrozoans and scaphozoans.
Nephridium (G. nephro, kidney+ L.ium,quality or nature of). A tubule specialized for excretion
and/or osmoregulation. See proto- and metanephridia.
Nephrocytes (G. nephro, kidney + cytos, cell). Cells which are capable of filtering and
accumulating waste particles.
Nephrostome (G. nephro, kidney + stoma, mouth). The fan shaped open and ciliated end of
metanephridia in polychaetes.
Neuro pile (G. neuron, nerve + L. pile, column). Intertwined processes of the interior of the
ganglion.
Neuropodium (G. neuro, nerve + pod, foot+ L. ium,quality of). Lower part of the parapodium.
Nudimental gland (L. nudus, nest). A gland of cephalopods (e.g. Loligo) which provides a
gelatinous mass which covers the eggs.
Notopodium (G. noto, back + pod, foot). The upper part of the parapodium.
Nucal organs (Arabic, nukla, nape of neck). Ciliated sensory pits in the head region of
polychaetes.
Nucleus (L. nucula, dim, kernel). Chromosomes contained within a double membrane, separate
from the cytoplasm of the cell. The region of the cell containing the genetic material, separated
from the cytoplasm by a double membrane (the nuclear envelope).
Nudibranchs (L. nudus, bare + G. branchos, gill, fin). An order of gastropods characterized by a
secondarily bilateral symmetry and loss of shell, mantle and original gill.
*They are coiled tubes with a short, stiff bristle-like process which is everted for protection or
prey capture.
O
Obligate (L. obligatus, bound) Biol. Restricted to a particular condition of life i.e. parasites which
must live in close association with hosts.
Odontophore (G. odonto, tooth + phore, carrier, bearer). The cartilaginous base for the radula of
mollusks.
Onchosphere (G. oncho, hook, barb + L. sphere, ball). The ciliated free-swimming larva of
cestodes.
Operculum (L. cover, lid). In serpulids, a modified radiole which serves as a plug when the
crown is withdrawn.
Ophiopluteus (G. ophio, snake + L. pluteus, shed, parapet). The second and planktonic larval
stage of ophioroides.
Opisthaptor (G. opistho, behind + apo, bind, fit). A muscular organ which attaches a parasite to
its host by means of suckers, hooks, etc.
Opisthosoma (G. opistho, behind + some, body). The posterior portion of pogonophores.
Osculum (L. little mouth). The large opening at the top of the atrium of asconid sponges.
Osphradium (G. osphresis, smellable). Sensory areas on the poster margin of efferent gill
membranes which have a chemoreceptor function.
Ossicle (L. ossiculum, dim. of ossis, bone). Calcareous rods, crosses or plates which are the
skeleton of asteroids.
Ostium, Ostia, pl. (L. door). Lateral openings in the heart of arthropods. Also the incurrent pore
of sponges.
Ovicell (L. ovum, egg + cell). A structure at one end of bryozoans which holds the embryo and
serves as a brooding chamber.
Ocelli (L. ocellatus, having small eye spots). Light sensitive organs.
Ommatidium (G. omma, eye + unknown deriv.). A long cylindrical structure possessing the
ability of light reception in the arthropod eye.
Oxconformers (G. oxys, sour, acid + E. conform, to adapt). Organisms whose oxygen
consumption is regulated in part by the amount available.
P
Paedogenesis (G. paedo, child + genesis, birth, origin). A sexually mature larval form which does
not become adult.
Paedomorphosis (G. paedo, child + morph, form + osis, condition of). Reaching sexual maturity
with juvenile morphology. In an evolutionary sense.
Palium (L. mantle, robe). The epidermis underlying the shell of mollusks.
Palium sinus (L. mantle, robe + sinus, space, hollow). A hollow structure below the adductor
which is the point of attachment of the siphon of mollusks.
Palruella (Deriv. unknown). A stage of development in flagellates characterized by loss of the
flagellum and non-motility.
Papula (L. pistule, pimple). Outpockets of epithelium of echinoderms which serve, with tube
feet, as gas exchange surfaces.
Parapodium (G. pare, beside, near + pod, foot). Lateral appendages extending from the segments
of annelids and from the body or foot of some mollusks.
Parenchyma (G. pare, beside, near + chyma, juice). A spongy mass of cells.
Parthenogenesis (G. parthenos, virgin + genesis, birth, origin). Reproduction by the development
of an unfertilized egg.
Paxilla (L. paxillus, nail, peg). Ossicles on the aboral surface of asteroids raised above the
surface and crowned with small spines.
Pecten (L. comb). Comb like chitinous plates which project from the sides of scorpions and
which are sensory.
Pedicellariae (L. pes, pedis, foot + cellarius, steward). Small specialized jaw like structures of
echinoyds which protect, and in one case, capture prey.
Pedicle (G. pea, foot + L. iculus, dim. suffix). A cylindrical extension of the ventral wall of
orachiopods which attaches to the substrate.
Pedipalp (L. pes, pedis, foot ~ palpo, feel, touch). A sensory appendage arising out of prosoma
and modified to perform various functions.
Pelecypod (lamellibranch) (G. pelecy, ax, hatchet + pod, foot). A class of mollusks which have
two shell valves and a large foot, both laterally compressed, and gills which have assumed a food
collecting function.
Pelmatazoa (G. pelma, sole of foot). Animals which travel on soles of foot (i.e. gastropods).
Pellicle (L. pellis, skin). Body covering of ciliates.
Pericardial (G. pert, near, on, around + kardia, heart). The region nearest the heart.
Perihemal - spaces or sinuses (G. pert, on, around, near + hema, blood). Separate extensions of
the coelam; part of the bloodvascular system of asteroides.
Perrostracum (G. pert, on, around, near + ostrakon, shell). The outer layer of the mollusk shell.
Peripods (G. peri, on, around, near +pod, foot). Crustacean thoracic appendages.
Periproct (G. pert, on, around, near + proctos, anus). The anal region of echinoderms.
Perisark (G. pert, on, around, near + sarco, flesh). In hydroids a non-living protein-chitinous
envelope which acts as a support.
Peristalsis (G. pert, on, around, near + staltikos, contraction). Undulations produced by waves of
contraction in the longitudinal muscles of the body wall.
Peristome (G. pert, on, around, near + stoma, mouth)
1. Groove which leads to cytostome in protozoans
2. Pre-oral chamber of ciliate
3. First complete segment of annelids
4. Post-oral region of polychaetes.
Peristomial membrane (G. pert, on, around, near + stoma, mouth). In ophiuroids a roof-like
structure over the prebuccal cavity.
Perivisceral (G. pert, on, over, around + L. viscera, entrails). Region nearest the intestines.
Petaloid (G. petalon, leaf). In echinoderms the aboral ambulacural area which radiates from the
aboral center.
Phagocyte (G. phago, to eat + cyte, hollow place, cell). Cells which engulf food particles or
foreign bodies. (Phagocytosis; the process of engulfment by a phagocyle)
Phasic neurons (G. phasis, to appear + neuron, nerve). Newrons which initiate fast but brief
muscle contractions in arthropods.
Pharynx (G. throat). Area between the mouth and nasal passages and the larynx.
Phasmid (G. phasma, apparition, specter). Unicellular glands in the tail of nematodes.
Phytoflagellate (G. phyto, plant + L. flagellum, whip). Single celled protozoa having flagellae
and chloroplasts.
Photophores (G. photo, light + phore, bearer). Light producing organs of euphaniaceans-krill.
Pinnules (L. pinnula (dim.), feather, wing). Jointed appendages on arms of crinoids giving them a
feather-like appearance.
Pinocytosis (G. ping, drink + cyto, cell). Uptake of liquid by cellular engulfment.
Polyplacophore (G. poly, many + placo, flat, tablet + phore, bearer, carrier). Chitons which have
eight overlapping transverse plates as shells.
Plankton (G. planeto, wandering, roaming). Floating oceanic organisms.
Planospiral (L. planus, flat, even + spiralis, coil, twist). A spiral form which extends more or less
horizontally.
Planula (L. planus, flat, even). Ciliated free swimming larva of coelenteratis.
Pleopod (G. pleo, swim, sail + pod, foot). Interior abdominal appendages used for swimming,
ventilation, food/gathering, etc. in malacostricans.
Plicate gill (L. plicatus, folded). A molluscan gill which the surface of the lamellae has been
increased by folding along the long axis.
Pleuron (G. pleura, side). The two lateral cuticular sections of the skeleton of arthropods.
Podium (L. platform, projection). Tubular projections on the ambulacural groove of asteroids
which serve as locomotor organs.
Polyp (G. polypous, coral). A sessile cnidarian.
Polypoid (G. polypous, coral + eidos, having the form of). Resembling a polyp, a sessile
cnidarian.
Pneumostome (G. pneumo, wind, air, breath + stoma, mouth). Porelike opening in pulmonate
snails leading into lung or mantle cavity.
Podium (podia, pi.) (G. pod, foot). Tubular projections on the arms of echinoderms which serve
as locomotor organs.
Polian vessicles (Deriv. unknown). Elongated muscular sacs suspended in the coelom of some
asteroids which are believed to serve as expansion chambers of the water vascular system.
Polychaete (G. poly, many + chaeto, long hair, mane). A class of annelids with paired lateral
fleshy appendages (parapodia).
Polyp (G. polypos, many footed). Coelanterate individual e.g. coral, anemone.
Polyplucophora (G. poly, many + placo, tablet + phores, body). A class of mollusks having a
body covering of transverse overlapping plates.
Polyploid (G. poly, many + ploid - der. unknown). Having more than two complete sets of
chromosomes.
Post larva (L. post, after). The last stage in the development of crustacean larvae.
Pre-epodite (L. pre, before + G. epi, around, on, near + pod, foot). Outer gill bearing structure of
the appendage of trilobites.
Proboscis (G,. proboskis, snout). An extensible or extended structure containing sense organs or
mouth and feeding aparatus.
Proboscides (G. pro, in front of + boske, food, fodder). Tentacles on the margin of the mouth of
protobranchia.
Proctodeal (G. proctos, anus, tail). The hind gut region of arthropods.
Protocuticle (G. pro, in front of + L. cutis, skin). The layer of cuticle lying immediately under the
epicuticle in arthropods.
Proglottid (G. pro, in front of + glottis, mouth of the windpipe). Linearly arranged individual
reproductive segments of the strobila of cestodes.
Prokaryote (G. pro, in front of + caryo, kernel, nut). A one celled organism whose genetic
material is distributed throughout the cell. Includes bacteria and blue-green algae.
Propodium (G. pro, in front of + pod, foot). The fore part of a podium.
Prosobranch (G. prove, forward + branchos, gill). Primitive mollusks of the sub order
Archeogastropods.
Prosoplyle (G. prove, forward + pyre, gate, orifice). Pores opening into the incurrent canals of
syconoid sponges.
Protocereberum (G. proto, first + L. cerebrum, brain). The anterior portion of the brain of
arthropods - see prefixes deutero - and trito.
Protonephridium (G. proto, first + nephro, kidney). Primitive excretory and osmoregulatory
organ. See text (Barnes) for flame cells.
Protoplasm (G. proto, first + plasma, substance, that which is formed). All cellular material.
Protopodite (G. proto, first + pod, foot). The two most proximate elements of the crustacean
biramous appendage.
Protostyle (G. proto, first + style, pillar, colemn). A rotating mass of mucus in the stomach of
molluscs.
Prototroch (G. proto, first + trocho, ball, round). Free swimming larvae of mollusks characterized
by a girdle of ciliated cells.
Protozoan (G. proto, first + zoon, animal). A single celled animal.
Pseudo branch (G. pseudo, false + branchos, gill). In aquatic pulmonates a gill formed
secondarily from folds of the mantle.
Pseudofeces (G. pseudo, false + L. feces, dregs, rejected material). Material too large to be
digested and egested by bivalves.
Pseudopodia (G. pseudo, false + pod, foot). A flowing extension of the body of sarcodinians.
Pteropods (G. ptero, feather, wing + pod, foot). An order of swimming pelagic opisthobranchs.
Pygidium (G. pygo, rump, tail). The terminal end of annelid worms.
R
Radioles (L. radium, rod, spike). A bipinnate feeding organ of fanworms which forms a conduit
for transporting food particles to the mouth.
Radule (L. radula, scraper). In mollusks, a feeding organ consisting of rows of chitinous teeth.
Redia (Deriv. unknown). The third developmental stage in the trematode life-cycle.
Rhabdites (G. rhabdo, stick, rod + ite, having the nature of). In turbellarians, rod shaped
epidermal bodies.
Rhabdomere (G. rhabdo, stick, rod + mere, part, portion). The area of retinular cells oriented at
right angles to the axis of the omatidium of arthropods.
Reticupodia (L. reticulatus, net-like + pod, foot). Branched interconnected thread-like
pseudopodia.
Retinula (L. rete, net). A network of rhabdomes which line the omatidium of arthropods.
Rhabdome (G. rhabdos, rod, staff). An enclosed central space, lined with rhabdomeres, in the eye
of arthropods.
Rhmophore (G. rhino, nose + phore, bearer, carrier). Modified opisthobranch tentacle containing
tactile and chemoreceptor cells.
Rhopalium (G. rhopalon, club). Concentrations of neurons in the margins of scyphozoans.
S
Saccules (L. sacculus, dim of saccus, bag). Small spherical bodies near the outer sides of lappets
in crinoids.
Saprophyte (G. sapro, rotten + phyto, plant). A plant which obtains its nutrients from dead
organic material.
Saprozoic (G. sapro, rotten + zoon, life). An organism which obtains its nutrients from dead
organic material.
Sarcodinas (G. sarco, flesh). Protozoans having flowing extensions of the body i.e. pseudo podia.
Scalid (L. scale, stair, ladder). Longitudinal rib like conical projections on the introvert of
priapulids.
Schizogamy (G. schistos, split + gamos, union). See fission.
Scolex (G. scolo, thorn, pointed). The anterior region of the head of cestodes.
Scaphognathite (G. scapho, trough, hollow vessel + gnathos, jaw). A paddle-like structure which
produces an inhalent current which flows over the lamellae of malacostrians.
Scyphistome (G. scyphus, cup + stoma, mouth). In schyphozoans, the polyploid larva, similar in
appearance to a hydra, which develops from a planula.
Scyphozoan (G. scyphus, cup). The cnidarians in which the medusa is the dominant and
conspicious individual in the life cycle.
Seminal vessicle (L. semen, seed). A coelomic pouch which provides for maturation of gametes
of oligochaetes.
Septibranch (L. septum, fence, wall + G. branchos, gill). A subclass of mollusks having
degenerate gills modified to muscular septa.
Seta, pl. setae (L. seta, bristle). A modified ennervated cilium.
Sinus (L. cavity, recess). Any cavity, recess, or passage in tissue or bone.
Siphonoglyph (G. syphon, pipe, tube + glypho, carve, engrave). In anemones, a ciliated groove at
each end of the mouth which provides for circulation of water.
Solenogaster (G. soleno, a pipe + gaster, stomach). A class of worms-shaped mollusks.
Spermatheca (G. spermation, seed + theca, case, container). Chambers or receptacles for storage
of sperm.
Spermatophore (G. spermation, seed + phore, carrier, bearer) Sperm contained within a
membrane or case.
Spheridia (L. sphere, ball). Statocyst containing structures in echinoids (urchins, sand dollars).
Spicule (L. kernel of grain, point). Skeletal process of spongia,either calcareous or siliceous.
Sporocyst (G. spore, seed + cyst, cell). The second developmental phase of a trematode life-
cycle, a hollow structure which develops into a radia.
Sporogony (G. spore, seed + gony, node). The development of spores
Sporozoite (New L. spore, seed + zoa, life). Stage in life-cycle of some protozoans, the
development of which follows sporogony.
Statoblast (G. statos, fixed, placed + blastos, ball). Resistant reproductive bodies of bryozoans
which germinate under favorable conditions.
Statocyst (G. statos, fixed, placed + cyst, cell). Kinetic sense organs; chambers containing
statoliths (concretions) in contact with recptor cells.
Sternum (G. sternon, breast, chest). The ventral cuticular skeleton of arthropods.
Sterogastrula (G. stereos, solid, first, hard + gaster, belly, paunch, womb). A blastula changed to
a solid gastrula by ingression, a process by which cells move into the blastocoel.
Stigmata (G. stigma, mark, spot). Pharyngeal slits in tunicates.
Stolon (L. stolo, branch, shoot, runner) - Runner connecting hydroids in colonial cnidarians.
Stomodeal (G. stoma, mouth). The foregut region of arthropods.
Stomodium (G. stoma, mouth + ium). Mouth area of larvae and gastrulae.
Strobila (G. strobilos, twisted or turning). 1. Posterior body of cestodes consisting of linearly
arranged proglettids. 2. The polyploid stage of scyhozoans which produce medusae by transverse
budding.
Style sac (G. style, pillar, column). The posterior conical section of the stomach of molluscs.
Subumbrella (L. sub, under + umbra, shade). Lower exterior surface of medusae.
Superposition image (L. super, over f positus, placed, put). The response of a rhabdomere to light
entering from adjacent ones.
Synapse (G. synapsia, connection, junction). Connections between neurons.
T
Torsion (Mid. Eng. torcion, to twist). In mollusks, the visceral mass, mantle and mantle cavity
being twisted 180degrees counterclock wise.
Totipotent (L. totus, all + noteus, powerful). Cells which can be transformed into all other types
i.e. archeocytes. (Undifferentiated cells)
Trachea (L. windpipe). Respiratory tubes of insects and some arachnids.
Trichobothria (G. tricho, hair + bothros, trench, pit). Long sensitive hairs, set in a socket; the
most important sense organs of arachnids.
Trichocyst (G. tricho, hair + cyst, cell). Organelles containing fluid hardens into rod-like
structures for defense or attachment.
Tritocerebrum (G. tritos, third + L. brain). The posterior region of the arthropod brain
Trivium (L. tri, three + rivus, alive). The three ventral ambulacral areas of holothuroids.
Trophozooid (G. trephin, nourish + zoe, life). A feeding or nutritive polyp (gastrozooid).
Tun (L. tunica, garment, husk). An animal which has undergone anabiosis.
Tunicin (L. tunica, garment, husk). A type of cellulose which is the principal constituent of the
covering of tunicates.
U
Umbo (L. boss, knob). A dorsal projection of the valve of bivalves.
V
Vacuole (L. vacuus, em~ty). A liquid-filled cavity in a cell.
Vector tissue (L. carrier, messenger). Special tissue which acts as a passageway for sperm
moving to ovisacs in hirudineans.
Vibraculum (L. vibrissa, whisker, hair). Modified bryozoan operculum with a seta used to sweep
away detritus.
Veliger larva (Deriv. unknown). Molluscan larva in which the foot and shell make their
appearance.
Velum (L. curtain, veil). Marginal flap or shelf attached to subumbrella at margin of bell of
medusae.
Vitillarium (L. vitellus, yolk of egg +arium, place or thing connected with). A structure in the
flatworm ovary which produces yolk eggs.
Zoea (G. zoe, life). The second stage of crustacean larvae.
Zooecium (G. zoe, life +L. ium, nature of). The external covering of bryozoans.
Zoochlorellae (G. zoe., life +chloro, green). Photosynthetic cells which live commensally with
cnidarians and ctenophores.
Zooid (G. zoon, animal +id, nature of).
1. Individual organisms which are attached in a chain-like fashion to form a colony.
2. An individual bryozoan.
Zooflagellates (G. zoon., animal +flagellum, whip). Protozoans which have one or more
flagellae and are without chloroplasts.
Zooxanthellae (G. zoon, animals + xanthos, yellow).
1. Symbiotic dinoflagellates
2. Foreign animals living symbiotically with marine animals.
Zygote (G. zygon, yoke, pair). A cell created by union of two gametes; a diploid form of a
reproductive cell.
Zygosis (G. zygon, yoke, pair). The process of the union of two zygotes.