Invertebrate Anatomy OnLine
Glycera dibranchiata ©
Copyright 2001 by
Richard Fox ,
Edward Ruppert, Clemson
is one of many exercises available from Invertebrate
Anatomy OnLine , an
Internet laboratory manual for courses in Invertebrate Zoology. Additional
exercises, a glossary, and chapters on supplies and laboratory techniques are
also available at this site. Terminology
and phylogeny used in these exercises correspond to usage in the Invertebrate
Zoology textbook by Ruppert, Fox, and Barnes (2004). Hyphenated
figure callouts refer to figures in the textbook. Callouts
that are not hyphenated refer to figures embedded in the exercise. The glossary
includes terms from this textbook as well as the laboratory exercises.
AnnelidaP, Polychaeta C,
Palpata, Aciculata, Phyllodocida O,
Glyceridae F (Fig
consists of the segmented worms in the major taxa Polychaeta (bristleworms),
Oligochaeta (earthworms and relatives), Branchiobdellida (crayfish
ectosymbionts), and Hirudinea (leeches) with a total of about 12,000 known
species in marine, freshwater, and terrestrial environments. The
segmented body is composed of an anterior prostomium, a linear series of similar
segments, and a posterior pygidium. The
prostomium and pygidium are derived from anterior and posterior ends of the
larva whereas the intervening segments arise through mitotic activity of
mesodermal cells in the pygidium.
body wall consists of a collagenous cuticle secreted by the monolayered
epidermis. A connective tissue dermis lies beneath the epidermis. The coelom is
lined by a peritoneum which may be specialized to form the body wall muscles. Most
annelids have chitinous bristles, or chaetae, secreted by epidermal cells, that
project from the body. The coelom is large, segmentally compartmented, lined by
peritoneum, and well developed in polychaetes and oligochaetes but reduced in
coelomic spaces are separated by transverse bulkheads known as septa which
consist of double layers of peritoneum with connective tissue in between. The
right and left sides of each segmental coelom are separated by longitudinal
mesenteries which, like septa, are double layers of peritoneum with connective
gut is a straight, regionally specialized tube that begins at the mouth at the
anterior end and extends for the length of the body to end at the anus on the
penetrates each septum and is supported by dorsal and ventral mesenteries. Like
that of most invertebrates, the gut consists of ectodermal foregut, endodermal
midgut, and ectodermal hindgut. The
nervous system consists of a dorsal brain in or near the prostomium, a pair of
circumpharyngeal connectives around the anterior gut, and a double, ventral
nerve cord with paired segmental ganglia and nerves. The
hemal system of most annelids is a set of tubular vessels, some of which are
contractile and serve as hearts. The
hemal system is absent or greatly reduced in leeches. The
system includes a dorsal longitudinal vessel above the gut in which blood moves
anteriorly, a ventral longitudinal vessel below the gut, in which blood moves
posteriorly, and paired segmental vessels that connect the dorsal and ventral
vessels. The digestive, hemal, and nervous systems are continuous and pass
through the segments.
is accomplished in a variety of ways. In
some, the general body surface is sufficient but gills are present in most
polychaetes, many leeches, and a few oligochaetes. Excretory
organs are metanephridia or protonephridia and typically one pair is present in
each segment. These osmoregulatory organs are best developed in freshwater and
terrestrial species. The sexes are
separate in polychaetes but oligochaetes and leeches are hermaphroditic. In
the ancestral condition paired submesothelial clusters of germ cells were
present in each segment and released developing gametes into the coelom. In
derived taxa reproductive functions tend to be confined to a few specialized
genital segments. Gametes mature in the coelom or its derivatives and
fertilization is external. Gametes
are shed through ducts derived from metanephridia or by rupture of the body
cleavage follows fertilization. Clonal reproduction is common.
is a large (8000 species) and diverse taxon of marine annelids thought to be the
most primitive of the annelid taxa and the most like the ancestral annelid. The
body of a typical polychaete is divided into segments, each of which bears a
pair of fleshy appendages, or parapodia. The
head is often equipped with abundant, well-developed sense organs. The
anterior gut is muscular, sometimes eversible, and frequently equipped with
chitinous jaws. Polychaetes
are gonochoric and gametes ripen in the coelom from which they are shed through
ducts or by rupture of the body wall.
prostomium has a pair of sensory palps. These are lacking in the sister taxon,
is a large taxon containing many worms well-known to marine biologists and
invertebrate zoology students. The parapodia are well-developed and biramous. The
prostomium has antennae. Aciculates
were once known as “errant” polychaetes because they are active and mobile.
are the polychaetes with a muscular eversible pharynx.
common on the coasts of North America and elsewhere. These
animals are known as "bloodworms" by fisherman who purchase them or dig them for
commercial bloodworm industry exists in Maine and the Canadian Maritime
Provinces where one species, Glycera
dibranchiata, attains large sizes and high population densities.
or preserved specimens are suitable for the study of Glycera. Preserved
animals are available from biological supply companies. Courses
taught on sedimentary coasts may collect living specimens or they may be
purchased from coastal bait shops or ordered from supply companies such as the
Woods Hole Marine Biological Lab or from wholesale bait distributors in the
northeast (See Supplies chapter). Glyceridae
is a homogeneous taxon and any species can be used for this study.
are derived polychaetes that have diverged in many ways from the more typical
polychaete plan as exemplified by Nereis. The
coelom is unpartitioned with vestigial septa, the hemal system is vestigial,
osmoregulation is with protonephridia instead of metanephridia, and gametes are
shed by rupture of the body wall.
are active raptorial species that excavate and inhabit galleries of tunnels in
soft sediments (Fig 13-39B). These worms capture food and dig with a powerful,
eversible pharynx which can be expelled forcefully through the mouth (Fig 1,
pharynx is a key feature in the life and evolution of glycerid worms.
of the adaptations exhibited by glycerids are ultimately consequences of the
presence of the eversible pharynx. 1.
A spacious and unpartitioned coelom is necessary to accommodate the retracted
pharynx. The transverse septa that divide the coelom of most other polychaetes
are necessarily lost or reduced in Glycera to
make room for the pharynx. 2.
The coelom, since it is not interrupted by septa, can function as a fluid
transport system and it replaces the hemal system, which is vestigial. 3.
The absence of a pressurized blood vascular system necessitates the substitution
of protonephridia for metanephridia since there is no heart or blood pressure to
drive ultrafiltration into the coelom. 4.
Finally, gametes must be shed by rupture of the body wall since there are no
metanephridial ducts to conduct them to the exterior.
spite of its unusual features, Glycera is
included in this collection as the representative of the polychaetes because it
is an easy dissection that reveals much about the organization of polychaete
is easily handled alive and is useful for observations of behavior and
an ambush raptor that uses the eversible pharynx for both prey capture and
burrowing. Glycera is
unusual among the many taxa of burrowing polychaetes because it uses the pharynx
to enter the sediment and pull itself through it. It
does not generate peristaltic contractions in the body wall as do most other
burrowing annelids. Glycera constructs
a system of interconnected burrows, called a gallery (Fig 13-39B), and occupies
one of the branch burrows where it waits in ambush for unsuspecting prey which
it seizes with its pharyngeal jaws. It
detects the presence of prey by sensing vibrations in the water with its four
Annoy the animal by pushing it (gently) with an applicator stick or a probe. Be
careful, Glycera has
poison glands and a large one can bite and, although by no means lethal, the
bite is not pleasant. Observe
the explosive protrusion of the pharynx and be sure to notice the four jaws at
the expanded tip of the pharynx. Each
jaw receives a duct from a poison gland in the pharynx wall. The
dark jaws can be seen through the body wall when the pharynx is retracted. Look
for them and note their position well posterior of the anterior end. <
burrowing with a rapid eversion of its pharynx into the sediment. Once
into the sediment, contraction of pharyngeal circular muscles causes the pharynx
to swell and form a terminal anchor. Contraction
of longitudinal muscles in the wall of the body pulls the rest of the worm
forward to the anchor.
can observe burrowing and gallery construction in an observation chamber made
from two pieces of window glass and a length of rubber tubing (Fig 5). Place
the apparatus upright, open end up, in a seawater aquarium, so you can see it
a healthy worm on the sediment surface and watch it burrow, recording your
the burrow seem to be lined with silk or mucus to stabilize its walls? <
your animal is living, place it in magnesium chloride and allow it to relax
completely. This will take 15-30 minutes depending on the size of the
use a worm that was relaxed by the teaching staff prior to the beginning of the
laboratory period. The
worm should be in a transparent dish of magnesium chloride. Study
the relaxed animal with the dissecting microscope.
If your worm is preserved it should be in tapwater.
the sleek, tapered, vermiform shape (Fig 13-39A). The body includes an anterior
head, posterior pygidium, and a large number of short, similar segments in
head is one of the simplest among the polychaetes and consists of the long,
conical prostomium plus the peristomium. It
bears the mouth but the sensory appendages are reduced.
The prostomium is
the anterior end of the worm (Figs 1, 2, 13-39C). Because
of its embryological origins it is not considered to be a true segment. It
is anterior and dorsal to the mouth and is long, conical, and divided into rings
by shallow transverse grooves.
worms often have the pharynx everted, giving the animal an awkward and unnatural
appearance that is anything but streamlined and tapered (Fig 1). When
fully everted, four black, chitinous jaws are
visible at the tip of the pharynx, which has temporarily become the anterior end
of the animal. If
the pharynx of your specimen is everted, the prostomium will be located at its
base and be dwarfed by it. Figures
2 and 13-39A show worms whose pharynges are not everted. Four tiny vibration
sensitive antennae are
visible at the tip of the prostomium (Fig 2). Use
the anterior, dorsal prostomium as a landmark to help locate ventral and
glycerid species have tiny eyes on the apex and base of the prostomium but Glycera
dibranchiata and G.
americana do not.
Figure 1. Dorsal
view of the anterior end of Glycera
dibranchiata with the enormous
pharynx everted. The
prostomium is the actual anterior end of the worm and the pharynx is usually
retracted and out of sight. Poly80L.gif
which is the first true segment, is immediately posterior to the prostomium and
is much wider (Fig 2). It
is fused with the proximal end of the prostomium and appears to be part of it. The mouth is
encircled by the peristomium and overhung by the prostomium. Note
the paired, horseshoe-shaped slits, the nuchal
organs, which are presumed to be chemoreceptors, situated laterally on
the dorsal surface of the peristomium. The
nuchal organs are ciliated pits which can be everted to form ciliated papillae. The
peristomium bears neither parapodia nor chaetae. The
first segment with parapodia and chaetae is the one immediately behind the
peristomium and is the second true segment.
living specimens, the large brain, surrounded by red, neuroglobin-rich tissue
can sometimes be seen through the dorsal body wall at the base of the
is easiest to see in small individuals with thin integument.
of the numerous short segments making
up the body of the worm is superficially divided into two rings, or annuli,
by a shallow transverse groove circling the body. As
a consequence, there seem to be twice as many segments as actually are present. Each
true segment, except the peristomium, bears one pair of fleshy parapodia which
protrude from the sides of the segment. Observe
the parapodia, noting that, with the exception of those of the anteriormost two
segments, they are biramous;
that is, composed of two branches.
living specimens look for a midventral line extending the length of the worm. It
is red and conspicuous. It
resembles, but is not, a blood vessel. It
is neuroglobin-rich tissue surrounding the ventral nerve cord. There
may also be a middorsal longitudinal, red line on your animal but it is not a
blood vessel either, but neither is it a nerve cord as you will soon see.)
Figure 2. The
anterior end of Glycera
dibranchiata with the pharynx
the magnification and look at the anterior surface of a parapodium of
a segment near the middle of the body. Each
parapodium is composed of two branches, or rami. These
are the dorsal notopodium and
the ventral neuropodium (Fig
are close together and may be difficult to distinguish from each other. Each
has a bundle of chaetae and the notopodium has a small dorsal cirrus.
your fine forceps, hold a parapodium so you see it in side view and look at the
parapodium is supported by a pair of short internal rods, the acicula, which
cannot be seen at present.
The gills (=
branchiae) are thin-walled coelomic sacs protruding through the body wall of the
dibranchiata has two unbranched
digitiform gills extending from each parapodium, one dorsal and one ventral,
hence the name "dibranchiata". If
the gills are otherwise, your specimen belongs to another species.
Figure 3. Anterior
view of the 55 th right
parapodium of Glycera
you have a living specimen, red hemoglobin-laden coelomic fluid will be visible
through the thin walls of the branchiae. Find
a parapodium with pink gills and examine the gill with your highest power using
transmitted light. Experiment
with the light to achieve the best view of the interior of the gill. Observe
the motion of the red coelomocytes in the coelomic fluid in the gill. If
you look carefully, you may also see some of the white cells that are often
clumped in the gills. Spherical
white ova are often visible in the gills. The
coelomic fluid is circulated by the ciliated peritoneum lining the coelom. <
The pygidium is
the posterior end of the animal. Like
the prostomium, it is not considered to be a true segment. It
is small and bears two short tentacle-like anal
cirri and a tiny anusdorsal
to the cirri. The
pygidium is often damaged and may be incomplete in your specimen.
your specimen from the glass dish to a long narrow dissecting pan of tapwater
(if preserved) or magnesium chloride (if living). Arrange it in the dissecting
pan so that, once pinned, all parts will be visible with the dissecting
under a dissecting microscope, orient the specimen with its dorsal side up. It
is easy to confuse dorsal and ventral but it is important to do so, so be
best landmark is the dorsal prostomium.
secure the anterior end by pressing two #1 insect pins through the bases of the
parapodia of segment 5 or 6 and into the wax of the dissecting pan. It
may be necessary to impale part of the lateral body wall in order to anchor the
specimen securely. Similarly,
pin the specimen to the wax at two points well behind the pharyngeal region
(about segment 60-70) stretching the animal slightly as you do so.
your finest scissors, make a dorsal longitudinal incision, starting at about
midbody and working anteriorly. Initiate
the incision by pinching the body wall with fine forceps and then snip through
the fold with fine scissors. The
incision should be shallow and slightly to one side of the middorsal line but
must pass completely through the body wall.
your animal is alive, red coelomic fluid will gush from the body but you should
not wash it away as it is useful in visualization of ciliary currents. As
soon as you open the coelom, pipet some coelomic fluid onto a slide and apply a
the preparation with high power of the compound microscope and find
coelomocytes. Note the size of the cells and look for bits of phagocytized
material inside them. Gametes,
either gigantic spherical ova with conspicuous nucleii, or tiny flagellated
spermatozoa, may also be present. <
your specimen is preserved, the coelomic fluid will be coagulated into irregular
gray masses filling the body cavity. Wash
this material away with squirts of water from a pipet. Advance the incision as
far as possible anteriorly, to the base of the prostomium, but do not cut into
the prostomium. The absence of septa makes the dissection much easier that it
would be inLumbricus or Nereis.
the incision a short distance laterally on either side of the anterior end of
the worm so the body wall can lie flat on the dissecting pan. Be
careful that you do not cut more deeply than the body wall.
the original pins, center the worm in the dissecting pan ventral side down, and
pin aside the two flaps of body wall. Insert
the pins at 45 ° angles
and use as many as necessary to hold the body cavity open. Stretch
the body wall slightly as you pin it. If
convenient, pull the gut to one side and secure it temporarily with a single
the incision posteriorly, pinning as you go, to the end of the worm.
the cut edge of the body wall along the middorsal incision. The
outermost layer of the thick body wall is the cuticle. Inside
it is the epidermis and
a layer of connective tissue. The cuticle is secreted by the
wall musculature lies inside
the connective tissue layer and resembles that of other annelids. First
is an outer layer of circular
muscles divided into rings
by the annulations in the cuticle and epidermis. The longitudinal muscles lie
inside the circular muscles and are arranged into four broad, flat, longitudinal
bundles that extend uninterrupted from anterior to posterior. Two dorsolateral
bundles lie on either side
of the dorsal midline and extend laterally to the dorsal edge of the parapodia
(Fig 4). These
are easy to see on the inner surface of the body wall. Two ventrolateral
bundles lie beside the
ventral midline and extend laterally to the ventral edge of the parapodia. They
are not so evident as the dorsolateral bundles. Later
you can use scissors to cut across a dorsal and ventral bundle to get a better
ventral bundles are easily seen in such a cross section. The
peritoneum is the innermost layer of the body wall but is not apparent in gross
polychaete peritoneum is usually not ciliated, that of Glycera is. The
coelom and coelomic fluid are the fluid transport system of these worms.
Circulating coelomic fluid and is responsible for distributing gasses,
nutrients, and wastes throughout the body. Mesothelial
cilia generate the necessary currents in the coelomic fluid to transport these
If you have a living worm, look at the mesothelial lining of the coelom for
evidence of ciliary activity. If
red coelomocytes are still present, their motion can easily be followed along
the wall of the coelom. If
no cells remain in the coelom, try to find some that spilled from the animal
earlier and pipet them back onto the peritoneum. <
your fine scissors to remove a complete parapodium and make a wetmount with it. Select
a parapodium from a segment in the posterior half of the worm. Study
it with 40X of the compound microscope and distinguish the notopodium from
the neuropodium (Fig
the dorsal and ventral
the small dorsal cirrus on
the dorsal base of the notopodium. There
is no ventral cirrus. Study
the chaetae with
100X and distinguish between the simple (unjointed) notochaetae and
the compound (jointed) neurochaetae. If
the thickness of your preparation permits, look at the chaetae with 400X and
then change back to 100x. Each
ramus is supported by a heavy, stiff, internal chitinous rod called an aciculum. Adjust
the light so you can see the acicula (Fig
large space revealed by opening the body is the coelom. It
is filled with coelomic fluid and
contains the viscera. The
coelom of Glycera is
spacious and, unlike that of most polychaetes, nearly free of septa or
mesenteries. Septa are
present, nevertheless, but are reduced to small, transparent, transverse
membranes on the coelom floor. Gently
drag the tip of aminuten nadel along
the floor of the coelom to demonstrate the presence of the reduced septa.
dissection of the anterior end of Glycera
nephridia and chaetal sacs of the left side are hidden by the gut. poly83La.gif
coelomic fluid contains abundant coelomocytes, most of which contain hemoglobin
and are red (in life). The
red coelomic fluid is the reason for the common name "bloodworm" for these
so-called "blood" of the name is actually coelomic fluid. Ironically,
bloodworms do not have blood.
conspicuous rows of segmentally repeated structures projecting into the sides of
the coelom are the acicula and
chaetae associated with the parapodia. The chaetal
protractor muscles are thin,
whitish bands arranged around each bundle like guy wires around a tent pole. A
cap of secretory tissue, the chaetal
sac, sits atop the two acicula, which it secretes (Fig 13-5A). Find
the two acicula associated with a chaetal sac.
long gut tube is
the most conspicuous feature in the coelom (Fig 4). It
is longer than the body and its anterior end may be coiled loosely in the
anterior coelom. The
extra length permits the protrusion of the pharynx during burrowing, feeding, or
preserved material the anterior gut is usually everted from the mouth.
gut is divided into three regions. There
is an anterior foregut, whose lining is ectodermal and cuticularized, a very
long, middle midgut with an endodermal, non-cuticularized lining, and a very
short, posterior hindgut which, like the foregut, is ectodermally derived and
lined with cuticle. The
midgut is by far the longest of the regions and its anterior end is attached to
the dorsal body wall by numerous dorsal
mesenterial muscles derived
from the dorsal mesentery (Fig 4). These
muscles, along with others in the gut wall, are the retractor muscles for the
The foregut extends
from the mouth to the point where the first mesenterial muscle originates (Fig
consists of the buccal cavity, pharynx, and esophagus. The
walls of the buccal cavity and anterior pharynx are longitudinally striated and
cannot be distinguished from each other until the gut is opened. The
anterior sixth of this longitudinally striped region is buccal
cavityand the remainder is the anterior
pharynx, which is not striped, has thick muscular walls and its
junction with the anterior pharynx is marked by four delicate flaps of tissue
attached to the gut wall. The
surface of this part of the pharynx bears four large, swollen, longitudinal
ridge contains a long pouch that itself contains a jaw, its musculature, and its
poison gland. A
black, chitinous jaw can
sometimes be seen through the pharynx wall at the anterior end of each of these
fleshy ridges. The
poison gland may also be visible as a whitish area in the middle of the ridge.
to the pharynx, the foregut narrows and becomes the esophagus (Fig
exposed surface of the esophagus is marked with faint transverse bands. The
esophagus extends posteriorly to its junction with the midgut.
or intestine, is easily recognized by the presence of the numerous dorsal
mesenterial muscles and the yellow (in life) chlorogogen
tissue in the peritoneum
investing it. The
mesenterial muscles originate from the dorsal midline of the midgut and insert
on the dorsal midline of the body wall.
pharynx is extended when contraction of circular muscles in the body wall
pressurizes the coelomic fluid and force the anterior foregut (pharynx) to turn
inside out through the mouth. Contraction
of the mesenterial muscles pulls the midgut posteriorly in the coelom and
retracts the foregut.
midgut is the region of hydrolysis, absorption, and feces formation. Its
anterior end is specialized for secretion of hydrolytic enzymes and digestion of
food molecules. The
middle region is specialized for absorption. The
dorsal mesenterial muscles are relatively small and weak in the absorptive
tissue, usually yellowish and a characteristic feature of annelid peritoneum,
functions metabolically like the vertebrate liver. It
stores glucose as glycogen and releases it when needed, synthesizes hemoglobin,
detoxifies toxins, deamifies amino acids to produces ammonia and synthesize
urea, and stores lipids.
short posteriormost region of the gut is the rectum, or hindgut, but it is
difficult to distinguish it from the midgut. The
rectum opens to the exterior via a very small anus.
the anterior gut with a longitudinal incision beginning at the mouth. Make
the cut a little to one side of the dorsal midline and avoid the brain in the
the cut posteriorly, studying the interior of each region before proceeding
cavity is lined with a
thick, iridescent cuticle with
wavy, irregular ridges. Its
iridescence is due to microscopic striations on its surface.
cuticle of the anterior
pharynx is transversely
ridged and bears a dense covering of minute papillae. The
cuticle is thinner and less evident in this region.
for the black tips of the four chitinous jaws protruding
into the lumen of the pharynx. The
jaw tips may be visible where they emerge from deep pouches in the gut wall. Push
the folds of tissue aside and reveal the opening of the pouch and look for the
jaw within. With
your fine forceps, grasp the tip of one of the jaws and gently pull it into
will be resisted by powerful muscles.
the tip of your finest scissors into the opening from which a jaw protrudes and
cut posteriorly to reveal the interior of the pouch, its musculature, jaw, and
thick muscular walls of the posterior
pharynx are lined with a
thick cuticle. The
walls of the esophagus are
thinner and less muscular than those of the pharynx but are also cuticularized,
most heavily anteriorly. The
cuticle is irregularly ridged.
elevated ring of circular muscle, the midgut
sphincter, marks the junction of the foregut with the midgut. The
walls of the midgut are thinner, softer, and much less muscular than those of
the foregut and have no cuticle.
excretory organs of Glycera are
protonephridia associated with modified coelomoducts (Fig 13-27C). There
is a pair of small and inconspicuous protonephridia in
each segment except for the first fifteen or so and the last few (Fig 4). The
protonephridia are attached to the body wall near the chaetal bundles by a
locate the protonephridia, first find the large chaetal protractor muscle on the
anterior side of a chaetal bundle and the large protractor muscle on the
posterior side of the adjacent chaetal bundle. The
two protractor muscles extend in opposite directions and cross each other near
the body wall. In Glycera
dibranchiata the protonephridium
is located at the point where they cross. In
life they are brown and white but these colors may be obscured by obsolescent
red coelomocytes which accumulate in their tubules. (In G.
americana there may be two or
even three nephridia associated with each chaetal bundle on the anterior
retractor muscle and the
the white (in life) ventral
nerve cord lying on the
ventral midline on the floor of the coelom. In
life it is surrounded by red neuroglobin-rich tissue which forms a longitudinal
red stripe along the midventral line outside the peritoneum. Try
to locate the delicate segmental nerves which extend laterally just posterior to
the ventral nerve cord anteriorly to the large, bilobed brain in
the prostomium dorsal to the pharynx. The
brain is also surrounded by red tissue in living animals.
the prostomium and extend the middorsal incision into it to get a good view of
the brain. Free
the brain from the surrounding tissues and find the two circumpharyngeal
laterally around the anterior gut from brain to nerve cord.
Fluid Transport System
fluid transport system of glycerids is the coelom. The
ciliated peritoneum circulates the coelomic fluid and transports materials from
sources to sinks. Oxygen,
for example, is transported from the gills to the tissues, nutriment is
transported from the midgut to the tissues, and ammonia is carried from
chlorogogen to the gills.
is a ciliated groove on either side of the dorsal midline that helps circulate
coelomic corpuscles. The
faint red color (in life) of the middorsal line is due to concentrations of red
coelomocytes in these grooves. Glycera is
usually reported as having no hemal system but recent work has shown it to be
present but vestigial. There
are no red corpuscles in the hemal system.
are gonochoric and the submesothelial gonads are evident only during the
reproductive season. If
gonads are present, they appear as opaque, white, globular masses attached
directly to the body wall next to the chaetal bundles. Gametes
are shed from the gonads into the coelom where they mature.
ripe, the worms release gametes from the coelom by rupture of the weakened body
adults do not survive the experience. The
tiny ducts associated with the protonephridia are not used for release of the
JH. 1967. A
monograph on the Polychaeta of southern Africa, Part 1, Errantia. British
Mus. Nat. Hist. 458p.
FW, Gardiner SI (Eds.). 1992. Microscopic
Anatomy of Invertebrates vol. 7 Annelida. Wiley-Liss,
New York. 418p.
MH . 1963. Marine
polychaete worms of the New England region. Bull.
Mus. Nat. Hist. 227:1-356.
EE, Smith PR . 1988. The
functional organization of filtration nephridia. Biol.
PR. 1989. Ultrastructure
of polychaete nephridial organs with emphasis on structure and function of
solenocytic protonephridia. Ph.D.
dissertation, Clemson Univ., Clemson, South Carolina.
W, Hermans CO. 1988. The
Ultrastructure of Polychaeta (Microfauna
Marina vol. 4). Fischer
Verlag, Stuttgart. 494p.
Ruppert EE, Fox RS,
Barnes RB. 2004.
Invertebrate Zoology, A functional evolutionary approach, 7 th ed.
Brooks Cole Thomson, Belmont CA. 963 pp.
Slides and coverslips
Glycera, about 10-12 cm
Dissecting pan. Kippered
herring, sardine, or smoked oyster tins poured with wax are a good size.
# 1 stainless steel insect pins
Isotonic magnesium chloride if using living Glycera
Dissecting set with microdissecting tools