Polycladida-Marine Flatworms

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355
Polycladida – Marine Flatworms
Verónica N. Bulnes – Translated from Spanish by Ben Machado

Fig. 2
Fig. 1
356
Phylum Platyhelminthes
Order Polycladida
General Introduction
The marine flatworms, also known as polyclads, are
colourful and delicate leaf-shaped animals that inhabit
the bottom of the sea. The name “Polycladida”, which
means ‘many branches’, is a reference to the shape of the
intestine in these animals. Even though there are over 900
described species, little is known about their physiology,
ecology or biogeography.
The marine flatworms are considered to be an ancient
group of invertebrates, possibly originating in the western
Indo-Pacific region. The majority of the species inhabit
waters between the latitudes 30ºN and 30ºS. They are
animals that primarily live in warm water environments;
the number of species diminishes in colder water areas.
Similarly, the species that inhabit warmer waters are very
colourful and eye-catching, whereas in the colder water
zones they go unnoticed by possessing more homogenous
colours. They are active predators that feed on oysters,
clams, corals, ascidians, etc.
External Anatomy
The Polycladida are dorsoventrally flattened worms, but
with a great capacity to change the shape of their body,
going from disk-shaped to completely stretched out. The
dorsal surface of the body displays colours and patterns
of colouration that are characteristic for each species, and
the epidermis can be smooth or covered with papillae. At
the anterior end of the body the eyes and tentacles can
be observed; they are sensitive structures connected to
an anterior ganglion concentration called the brain (Figs.
1&2). Ventrally they are smooth, except for representatives
of the Cotylea that possess a glandulo-muscular organ
named the sucker, which is located behind the mouth and
the genital openings or gonopores.
Internal Anatomy
The marine flatworms do not possess an excretory,
respiratory or circulatory system and exchange with
the environment is accomplished by simple diffusion of
substances across the body wall. The digestive system is
incomplete, they have no anus and waste is regurgitated
through the mouth. The intestine extends from a central
cavity, where the mouth is located, splitting radially towards
the margins of the body. The mouth opens into a relatively
large internal cavity, housing the pharynx, which is a
muscular organ capable of engulfing, sucking or crushing
prey (Figs. 3&4). The polyclads are hermaphrodites, with
the female and male reproductive systems developing
simultaneously (Figs. 5&6). The male reproductive system
is constituted, in general, by small and numerous testicles,
Polycladida – Marine Flatworms
Verónica N. Bulnes – Translated from Spanish by Ben Machado

Fig. 6
Fig. 3
Fig. 7
Fig. 4
Fig. 8
Fig. 5
357
Fig. 1. ce, cerebral eyes; fe,
frontal eyes; me, marginal eyes;
nt, nuchal tentacles; te, tentacu-
lar eyes.
Fig. 2. fg, female gon opore; m,
mouth; mg, male gonopore; mt,
marginal tentacles; ov, ovaries;
ph, pharynx; su, sucker; te, ten -
tacular eyes; tes, testicles.
Fig. 3. b, brain; i, intestine; m,
mouth; nt, nuchal tentacles; ph,
pharynx.
Fig. 4. i, intestine; m, mouth; mt,
marginal tentacles; ph,
pharynx; phc, pharyn-
geal cavity.
Fig. 5. asv, accesory
seminal vesicle; ej,
ejacu lator y duct; fa, fe-
male atrium; fg, female
gonopore; lv, Lang´s
vesicle; m a, male at-
rium; mg, male gono-
pore; ovi, oviduct; pv,
protatic vesicle; s, sty-
let; sv, seminal vesicle;
vb, vagina bulbosa.
Fig. 6. cg, cement
glands; dgi, genito-
intestinalis duct; ej,
ejaculatory duct; fa,
female atrium; i, intes-
tine; ma, male atrium;
ovi, oviduct; pd, prostatic duct; pp, penis papila;
pv, prostatic ve sicle; sb, spe rmiducal b ulbs; s v, se-
minal vesicle; v, vagina; vd, vas deferens.
Fig. 7. ej, eja cul ato ry duct; pd, pr ost atic du ct; pv, prost ati c
vesicle; sv, seminal vesicle.
Fig. 8. ej, ejaculatory du ct; exg, extra -vesicula r glan ds; pv,
prostatic vesicle; sv, seminal vesicle.

358
Phylum Platyhelminthes
Order Polycladida
Identification
The description of the microanatomy, especially from
serial histological sections of the reproductive organs, is
decisive for the identification of the specimens. The male
reproductive system shows the greatest specialisation
and may develop numerous types of organization. The
female reproductive system, as well as the digestive
system, reveals information that also must be taken into
consideration.
For the classification of suborders and families, the
characteristics considered are the orientation of the
prostatic vesicle, the type of pharynx and the direction
of the male copulatory organ. At the generic level, great
importance is given to the type of male copulatory organ,
the multiplication of genital organs, the peculiarities of the
digestive system, and the presence or absence of definite
male and female organs (the Lang’s vesicle, the seminal
vesicle, the genito-intestinalis duct, etc). The form of the
body, its size, colour, colour pattern and number of eyes
have proven to be variable, in many cases with variations
due to the environmental origin and also depending on
the stage of development; consequently, these characters
are only considered for discriminating at species level.
The systematic classification of this group developed
by Faubel (1983–1984) is based on microanatomical
characteristics, especially the presence and type of
prostatic vesicle, its relationship with the ejaculatory duct
and the type and shape of the copulatory organ. There
is also an important compilation authored by Prudhoe
(1985), based mostly on the external morphological
characters. The following work is based on the
classification system of Faubel (1983–1984), due to the
fact that many of the original descriptions of the Chilean
species were based on fixed material, and because the
ecological variability and biology of this group in Chile is
relatively unknown.
a seminal vesicle, various types of prostatic vesicles
(Figs. 7&8), and the copulatory organ, which can be a
stylet, penis or cirrus. The female reproductive system is
composed of the ovaries, uterus and vagina. The latter is
surrounded with a musculo-glandular tissue with different
degrees of development. In some cases there are other
accessory organs that are located behind the point where
the oviduct joins the vagina, such as Lang’s vesicle or the
uterine vesicles. Although self-fertilisation is possible,
in general cross fertilisation takes place, usually after a
specific mating ritual. The fertilised eggs are deposited in
laminar form and they remain adhered to fixed objects on
the bottom by means of mucilaginous secretions (Cannon,
198 6).
Collection and Preservation
Although the first descriptions date from the 18th century,
this group has never been intensively studied. This is to a
great extent because of their extreme fragility and that
they generally do not withstand the traditional sea-bottom
sampling methods. Also, their manipulation in the laboratory
is difficult and identification always involves elaborate
microscopic techniques.
The polyclads must be handled with fine, moist brushes,
transferring them to receptacles with clean water before
proceeding with fixation. It is necessary to photograph them
alive, or to register in a detailed manner all the information
about their colouration and colour patterns. Once extended
and relaxed, they must be submerged in a rapid action fixative.
The material is best fixed in Bouin’s fluid, 10% formalin, or
70–100% ethyl alcohol for 3–6 hours and then preserved in
70% ethanol. The specimen must be completely submerged
and not be agitated, since they continue to be extremely
fragile, despite being fixed. Later they must be embedded
in a block of paraffin or resin before continuing with the
histological techniques (Newman & Cannon, 2003).
Marine Flatworms of the Chilean Fjord Region
Until 1882, when Ludwig von Graff created the order
Polycladida, these animals were described as organisms
belonging to Turbellaria, Planaria, Vermes, etc. In 1884,
Lang published a book on the polyclads of the bay of
Naples, which is a detailed account of this group from
the waters of the Mediterranean Sea. After this very
important contribution, many authors continued the
work of Lang on this group. Ernst Marcus (1947–1954)
and Eveline Du Bois-Reymond Marcus (1955–1968)
studied polyclads on the coasts of Brazil; this is the most
important contribution on the knowledge of this group
in South America. In the 1980s, Faubel (1983; 1984) and
Prudhoe (1985) published a series of contributions that
set the basis for the current systematics of the flatworms.
The most important study on the polyclads in Chile was
performed by Marcus (1954), based on the specimens
collected during the Lund University Chile Expedition.
The previously cited faunistic studies of the group in

359
Chilean territory (see bibliography) were based on
the species gathered during different expeditions to
Antarctica, the Magellan Region, Juan Fernández and
Easter Island. More recently, Baeza et al. (1997) described
a new species from Chile, demonstrating the growing
interest of scientists in exploring the fauna inhabiting
the Chilean coastal waters. Nevertheless, almost all the
scientific contributions for the polyclads are descriptive
accounts of the morphology, taxonomy and systematics
of the flatworms and less is known about the biology,
ecology and biogeography of this group in the Chilean
territory. Nineteen species are described for the Chilean
fjord region (See App. 2 for the complete list) Seinfeld
(2002). During the process of making this book, five
species of Polycladida were collected. These will be
morphologically characterised in detail in this chapter.
Classification
Suborder Acotylea Lang, 1884
Superfamily Ilyplanoidea Faubel, 1984
Family Euplanidae Marcus & Marcus, 1966
Aprostatum stiliferum Bock, 1913
Superfamily Stylochoidea Poche, 1926
Family Callioplanidae Hyman, 1953
Neostylochus pacificus Bock, 1923
Superfamily Leptoplanoidea Faubel, 1984
Family Notoplanidae Faubel, 1983
Notocomplana palta (Marcus, 1954)
Suborder Cotylea Lang, 1884
Superfamily Euryleptoidea Faubel, 1984
Family Euryleptidae Lang, 1884
Eurylepta meridiana (Ritter-Zahony, 1907)
Family Laidlawiidae Herzig, 1905
Laidlawia trigonopora Herzig, 1905
Family Euplanidae Marcus & Marcus, 1966
Ilyplanidea with ruffled pharynx, with more or less
central position. Copulatory apparatus directed
backwards; gonopores separated. Male reproductive
system lacks accessory prostatic vesicles entering the
ejaculatory duct. Tentacles absent or rudimentary.
Genus Aprostatum Bock, 1913
Euplanidae with elongated or oval shaped body.
If marginal eyes present, they are well developed.
Tentacular, frontal and cerebral eyes in varying positions.
Pharynx anterior or somewhat central. Male reproductive
system with seminal vesicle or spermiducal bulbs, penis
armed with a sclerotised stylet. Lang’s vesicle present.
Type species: Aprostatum stiliferum Bock, 1913, by
original designation.
Family Callioplanidae Hyman, 1953
Stylochoidea with ruffled pharynx located centrally or
somewhat anterior to centre of body. Male reproductive
system directed posteriorly backwards or perpendicular;
true ejaculatory duct present. Prostatic vesicle with
smooth or somewhat wavy but not ridged glandular
lining. Usually, the gonopores are localized in the
posterior body half and open separately to the exterior.
Genus Neostylochus Yeri & Kaburaki, 1920
Callioplanidae with tentacles reduced or knobs. With
tentacular, cerebral and marginal eyes. Pharynx in
anterior half of body. Male reproductive system with
true seminal vesicle and penis armed with an elongated
tubular stylet. Lang’s vesicle present. Type species:
Neostylochus fulvopunctatus Yeri & Kaburaki, 1920, by
original designation.
Family Notoplanidae Faubel, 1983
Leptoplanoidea with obovate, or cuneate form of body.
Pharynx ruffled. Male reproductive system directed
backwards, located behind pharynx; with true prostatic
vesicle present, ’interpolated’. Glandular lining profoundly
folded, forming a limited number of tubular chambers
that surround central ejaculatory duct projected distally
to interior of vesicle.
Genus Notocomplana Faubel, 1983
Notoplanidae with paired tentacular and cerebral eye
clusters. Tentacles usually lacking. Gonopores separate.
Male copulatory system consists of a true seminal vesicle
and an elongated or blunted, conical penis papilla.
Female apparatus with Lang’s vesicle. Vagina with
tendency to have a strong muscle wall (vagina bulbosa).
Type species: Notocomplana humilis (Stimpson, 1857),
new combination Faubel, 1983.
Family Euryleptidae Lang, 1884
Polyclads with more or less elliptical body shape, without
marginal tentacles. Cerebral and marginal eyes present.
Pharynx cylindrical; mouth located behind the brain.
Male reproductive system located beneath the pharynx
and directed forwards. Prostatic vesicle arranged ’free’;
1 pair of accessory prostatic organs present. With true
seminal vesicle and penis armed with stylet. Female

360
Phylum Platyhelminthes
Order Polycladida
reproductive system with 2 uteri directed backwards and
1 uterine vesicle present.
Genus Eurylepta Ehrenberg, 1831
Euryleptidae with smooth dorsal surface, marginal
tentacles well developed or rudimentary. Cerebral
eyes distributed in 2 elongated groups. Mouth located
directly behind the brain. Digestive system devoid
of frontal median intestine, hence the main intestine
forks anteriorly around the pharynx. Male reproductive
system with dorsal prostatic vesicle; oriented forward.
Penis papillae armed by a tubular pointed stylet. 1 pair of
uterine vesicles present. Type species: Eurylepta cornuta
(O. F. Müller, 1776), new combination Ehrenberg, 1831.
Family Laidlawiidae Herzig, 1905
Cotylean of elongate to broadly oval body shape; with
smooth dorsal surface. Tentacles lacking or reduced to 2
blunt conical folds. Cerebral and marginal eyes present.
Pharynx directed towards the level of the brain; digestive
system with 1 central anterior median branch of the main
intestine. Gonopores separate. Male reproductive system
beneath pharynx, directed forwards. Seminal vesicle
present; prostatic vesicle arranged in ‘free’ form. Penis
papillae armed with stylet. Female reproductive system
with 1 pair of seminal receptacle vesicles and 1 unpaired
genito-intestinalis duct. Oviduct connected caudally to
a common duct, which opens to the exterior dorsally.
Uterus or uterine vesicles absent. Ventral sucker on
posterior body half.
Genus Laidlawia Herzig, 1905
With the characteristics of the family. Type species:
Laidlawia trigonopora Herzig, 1905 by original
designation.
Taxonomic Key
(Based on Faubel, 1983–1984, modified by the author)
1) a) Without a ventral sucker behind female gonopore. If tentacles present, they are nuchal ............................ 2
b) With ventral sucker behind female gonopore. If tentacles present, they are marginal. ................................ 9
2) a) With true prostatic vesicle .......................................................................................................................... 3
b) Without true prostatic vesicle. .................................................................................................................... 8
3) a) Prostatic vesicle arranged free .................................................................................................................... 4
b) Prostatic vesicle arranged interpolated ....................................................................................................... 5
4) a) Copulatory organ is a cirrus with sclerotised teeth. ........................................................................Planocera
b) Copulatory organ is a penis papillae armed with stylet..............................................Neostylochus, (p. 362)
5) a) Prostatic vesicle with smooth inner lining ..............................................................................Stylochoplana
b) Prostatic vesicle with ridged or chambered inner lining ............................................................................. 6
6) a) Prostatic inner lining ridged; without any projection of the ejaculatory duct into the prostatic vesicle .........
..........................................................................................................................................................Hylocelis
b) Prostatic inner lining chambered; ejaculatory duct projecting into the prostatic vesicle ............................. 7
7) a) Penis papillae armed with stylet ...................................................................................................Notoplana
b) Penis papillae conical and short ............................................................................. Notocomplana, (p. 363)
8) a) Penis papillae armed with tubular pointed stylet ..........................................................Aprostatum, (p. 361)
b) Penis papillae conical .................................................................................................................Euplanoida
9) a) Tubular pharynx directed forwards; mouth immediately behind brain; prostatic vesicle arranged free ..... 10
b) Ruffled pharynx extending perpendicularly in pharyngeal cavity; mouth opening in varying positions .... 12
10) a) Male gonopore opens independently of mouth ........................................................................................11
b) Male gonopore and mouth open together to exterior ...............................................................Stylostomum
11) a) With marginal eyes and anterior median branch of intestine; with gastro-intestinalis duct; without uterine
vesicles ...............................................................................................................................Laidlawia, (p. 365)
b) Without marginal eyes or anterior median branch of intestine, without gastro-intestinalis duct, with 1 pair of
uterine vesicles.................................................................................................................... Eurylepta, (p. 364)
12) a) Without prostatic vesicle ...........................................................................................................Stylochoides
b) Prostatic vesicle arranged free........................................................................................................................... 13
13) a) Dorsal surface smooth ....................................................................................................................Tytthosoceros
b) Dorsal surface covered with papillae ..............................................................................................Thysanozoon

250 µm
Fig. 9
361
Aprostatum stiliferum Bock, 1913
Common name: Small brown polyclad;
Policlado castaño pequeño
Description: Shape and colour: 9.25 mm long and
8.2 mm wide. Body rounded. Colour light brown;
translucent. Tentacles: Nuchal tentacles rudimentary,
only distinguishable in histological cross-section. Eyes:
Great quantity of eyes distributed in many rows on
dorsal body, especially on the anterior half. Cerebral and
tentacular eyes intermixed. Marginal eyes around whole
body. Mouth and pharynx: Mouth opening behind centre
of body; distal in pharyngeal cavity. Ruffled pharynx
strongly folded, reaching a length of 1/³ the body length.
Reproductive system: Not completely developed. Mal e:
Male copulatory organ without prostatic vesicle or
seminal vesicle and with 2 accessory seminal vesicles.
Penis directed backwards; armed with sclerotised
tubular stylet that is not completely developed. Penis
housed in an elongate and narrow male atrium. Female:
Vagina poorly developed; inner lining ciliated and
folded. Cement glands surrounding middle portion of
vagina. Lang’s vesicle absent. Possibility for confusion:
Unknown.
Habitat: On polychaetes and ascidians. Depth: 15
m. Abundance: Unknown; 2 specimens collected.
Distribution: SE Pacific (ZPN–ZPC). Chile: 43°S–50°S.
Comments: Description based on collected specimens.
Main reference: Bock (1913).
Fig. 9. Longitudinal view of reproductive system. asv, acces-
sory seminal vesicle; ej, ejaculatory duct; fa, female atrium;
fg, female gonopore; ma, male atrium; mg, male g o nopore;
ovi, oviduct; p, penis; s, stylet; v, vagina.

300 µm
2 mm
Fig. 10
362
Phylum Platyhelminthes
Order Polycladida
Neostylochus pacificus Bock, 1923
Common name: Juan Fernández polyclad;
Policlado de Juan Fernández
Description: Shape and colour: 17.7 mm long. Anterior
border rounded; sides almost parallel. Colour white-
yellowish to brown. Tentacles: Rudimentary. Eyes:
Tentacular eyes in 2 groups. Frontal eyes numerous;
radially distributed; up to the pharynx. Marginal eyes
completely surrounding body. Mouth and pharynx:
Mouth opening posterior in pharyngeal cavity. Ruffled
pharynx strongly folded; 4.9 mm long. Reproductive
system: Male: Testes small and numerous. Seminal
vesicle behind pharynx; anchor-shaped. Central portion
of seminal vesicle connected with ejaculatory duct.
Prostatic duct joins ejaculatory duct beyond base of
penis papillae. Prostatic vesicle with smooth glandular
lining. Numerous extra vesicular glands. Penis papillae
conical and muscular; armed. Straight stylet; 137 µm
long; housed in a male atrium directed posteriorly.
Female: Vagina directed forward, located dorsally to
male copulatory organ. Common oviduct penetrates
female canal from below; the canal continues dorsally
and turns in a posterior direction. Ciliated epithelium;
ce men t gl and s su rro und ing mid dle tr act o f va gina. Lan g’s
vesicle rounded. Possibility for confusion: Unknown.
Habitat: Rocky bottoms. Depth: 14–17 m. Abundance:
Unknown; 5 specimen collected. Distribution: SE
Pacific (PP–ZPN); Juan Fernández Archipelago. Chile:
33°S–43°S.
Main reference: Bock (1923).
Fig . 10. A) Longitudinal view. B) Longitudinal view of the copu-
latory system. b, brain; ce, cerebral eyes; cg, cement glands;
ej , ej acul ato ry d uct ; exg , ex tra -ve sic ula r gla nds ; fe , fro nta l ey es;
fg, female gonopore; i, intestine; lv, Lang’s vesicle; m, mouth;
ma, male atrium; me, marginal eyes; mg, male gonopore; ovi,
ovi duct ; pd, pros tati c duct ; ph, phar ynx ; pv, pr osta tic v esic le; s,
stylet; sv, seminal vesicle; te, tentacular eyes; v, vagina.

250 µm
C
A
3 mm
500 µm
B
Fig. 11
363
Notocomplana palta (Marcus, 1954)
Common name: Large pink polyclad;
Policlado rosado grande
Description: Shape and colour: 21.5 mm long and 4.6
mm wide. Body elongated; with rounded anterior and
posterior ends. Dorsal surface red, pink or light brown;
with a darker dorsal line; ventrally yellowish. Tentacles:
Small. Eyes: Cerebral eyes in 2 groups that join anteriorly.
Tentacular eyes in 2 groups. Mouth and pharynx: Mouth
opens at anterior half of body, in middle of pharynx
cavity. Pharynx ruffled; 1/³ of body length. Reproductive
system: Separated gonopores. Male: Testes ventral and
ovaries dorsal. Vasa deferentia enter separately into
seminal vesicle. Ejaculatory duct extends into interior
of prostatic vesicle. Prostatic vesicle ‘interpolated’.
Glandular inner lining folded forming 4 tubular
chambers. Penis papillae slender and short; housed in a
deep male atrium. Female: Common oviduct that opens
from below female canal. From this point on along and
backwards the duct opens to a spacious Lang’s vesicle.
Cement glands anteriorly open into proximal portion of
vagina. Vagina and female atrium without distal folds.
Possibility for confusion: Notocomplana chierchiai
(Plehn, 1896), which is translucent, pale grey, with a
darker dorsal line and with cerebral eyes arranged in 2
well separated groups (dorsally N. palta is brown to red,
with a darker mid line and the groups of cerebral eyes
fused anteriorly).
Habitat: Rocky bottoms. Depth: Intertidal–5 m.
Abundance: Unknown; 5 specimens collected.
Distribution: SE Pacific (ZPN). Chile: 41°S–42°S.
Main references: Marcus (1954); Faubel (1983).
Fig. 11. A) Longitudinal view. B) Longitudinal view of the
copulatory apparatus. C) Diagram of the prostatic vesicle.
b, brain; cg, cement glands; ej, ejaculato ry duct; fa, female
atrium; fg, female gonopore; i, intestine; lv, Lang’s vesicle;
m, mouth; ma, male atrium; mg, male gonopore; nt, nuchal
tentacles; ovi, oviduct; ph, pharynx; pp, penis papillae; pv,
prostatic vesicle; sv, seminal vesicle; v, vagina.

300 µm
Fig. 12
364
Phylum Platyhelminthes
Order Polycladida
Eurylepta meridiana (Ritter-Zahony, 1907)
Common name: Chilean red flatworm;
Policlado chileno rojo
Description: Shape and body: 7.3 mm long and 8.4 mm
wide. Body oval. In vivo dorsally red; with a brown band
along margin of body; preserved, dorsally brown with
a lighter marginal band. Tentacles: Marginal tentacles
small. Eyes: Cerebral eyes separated in 2 groups; well
developed. Tentacular eyes small; only visible in serial
sections. Mouth and pharynx: Mouth opens in front of
the female gonopore. Cylindrical pharynx; reproductive
system everted during fixation. Reproductive system:
Separated gonopores. Male: With muscular seminal
vesicle. Prostatic vesicle located dorsally to seminal
vesicle. Penis papillae armed with a short stylet. Female:
Female atrium and vagina without folds. Cement glands
surround terminal portion of vagina. Possibility for
confusion: Unknown.
Habitat: On hydrozoa. Depth: 15–20 m. Abundance:
Unknown; 4 specimens collected. Distribution: SE
Pacific (ZPN–ZPC). Chile: 42°S–52°S.
Main reference: Ritter-Zahony (1907).
Fig. 12. Longitudinal view of the reproducti ve system. ej, eja-
cula tor y duct; c g, ceme nt gl and s; fa , female atr ium; fg, f ema -
le gonopore; m, mouth; ma, male atrium; mg, male gonopore;
pd, prostatic duct; phc, pharynx cavit y; pv, prostatic vesicle;
s, stylet; sv, seminal vesicle; v, vagina.

50 µm
Fig. 13
365
Laidlawia trigonopora Herzig, 1905
Common name: Brown Magellan polyclad;
Policlado magallánico café
Description: Shape and colour: 2.55 mm long and
1.9 mm wide. Body rounded; distally widened.
Dorsally with reddish-brown pigment granules, with
a marginal band free of pigment. Tentacles: Marginal
tentacles rudimentary. Eye s: Tentacular and cerebral
eyes in separate groups. Mouth and pharynx: Mouth
opens in front of male gonopore. Cylindrical pharynx.
Reproductive system: Male: Male gonopore near mouth.
Vasa deferentia enter separately to well-developed
seminal vesicle. Prostatic vesicle elongated and slender;
arranged ‘free’; located dorsally to seminal vesicle.
Ejaculatory duct joins prostatic duct just after base of
penis. Penis papillae armed with pointed stylet, 130 µm
long, located in a deep male atrium. Female: Female
reproductive system with 1 pair of seminal receptacles
and 1 unpaired genito-intestinalis duct. Oviduct
connects caudally to an unpaired common duct that
opens dorsally to exterior. Possibility for confusion:
Unknown.
Habitat: Under rocks. Depth: 12.5 m. Abundance:
Unknown; 1 specimen collected. Distribution: SE
Pacific (ZPN–ZPC). Chile: 43°S–53°S.
Main reference: Herzig (1905).
Fig. 13. Longitudinal view of the reproductive system. ej, eja-
culatory duct; exg, extra-vesicular glands; fg, female gonopo-
re; m, mouth; ma, male atrium; mg, male gonopore; p, penis;
pd, prostatic duct; phc, pharynx cavit y; pv, prostatic vesicle;
s, stylet; sv, seminal vesicle; v, vagina; vd, vas deferens.

366
Phylum Platyhelminthes
Order Polycladida
Glossary
Accessory seminal
vesicle (asv)
Terminal distension of the vasa deferentia, also known as false seminal vesicle (Fig. 5).
Brain (b) Concentration of ganglion nerves located in the anterior region (Fig. 3).
Cement glands (cg) Belonging to the female reproductive system, located next to the female gonopore,
responsible for the secretion of the mucilaginous substances that assist in the fixation of the
eggs to the substratum (Fig. 6).
Ciliated epithelium Tissue constituted by ciliated cells that covers the body of the polyclads and some of their internal
structures.
Cirrus It consists of a hollow muscular bulb usually lined by a variety of sclerotised teeth and
spines, which evert to the exterior, works as a male copulatory organ.
Ejaculatory duct (ej) Constituted by the terminal part of the male duct from the proximal portion of the seminal
vesicle, up to the tip of the penis or everted cirrus (Figs. 5–8).
Extra-vesicular glands
(exg)
They are located on the out side of the prostatic vesicle. Their fine ducts cross the muscular
wall of the vesicle, pouring their secretions into the prostate (Fig. 8).
Eyes The polyclads possess numerous types of eyes. The marginal eyes (me) occur along the body
margin; the tentacular eyes (te) are on the tentacles; the cerebral eyes (ce) are situated over
the brain region and the frontal eyes (fe) are located dorsally from the anterior margin of the
body up to the location of the pharynx (Fig. 1).
Female reproductive
system
Consisting of the ovaries, oviducts, uteri, vagina and any other accessory organ that is
located behind the point where the oviduct joins the vagina. This last one is generally
surrounded by a glandular tissue producing mucilaginous substances that are responsible for
the fixation of the eggs to the sea bottom (Figs. 5&6).
Genito-intestinalis duct
(dgi)
Connection, present in some species, between the female copulatory apparatus and the
digestive system (Fig. 6).
Gonads The polyclads are hermaphroditic. The testes (tes) and ovaries (ov) are found distributed in
the lateral body regions (Fig. 2).
Gonopores The polyclads can have separate male (mg) and female (fg) gonopores, or both reproductive
systems can open to a common gonopore. In general the female gonopore is located behind
the male one (Fig. 2&5).
Intestine (i) Formed by a central tube from which intestinal branches radiate towards the periphery.
Distally the branches may anastomose into a peripheral net work (Figs. 3,4&6).
Lang’s vesicle (lv) In many acotylean polyclads, from the point of entry of the oviduct to the female duct, a long
duct directed posteriorly can develop that opens into a blind sac called Lang’s vesicle, which
probably functions as a seminal receptacle (Fig. 5).
Male atrium (ma) Cavity that extends from the male gonopore to the base of the copulatory organ and houses
the penis papillae (pp), rod, stylet or cirrus when present (Figs. 5– 6).
Male reproductive
system
Generally formed by a seminal vesicle, a prostatic vesicle and a copulatory organ, which can
be a stylet, penis or cirrus (Figs. 5&6).
Oviduct (ovi) Tube that connects the ovaries to the uterus, generally paired (Figs. 5&6).
Penis Male copulatory organ, in general the term is used combined, as in penis papillae (pp), or
penis armed with stylet (Fig. 6).
Pharynx (ph) Glandulo-muscular structure found between the mouth and intestine. The pharynx is
protrusible and used to capture prey. The ruffled pharynx is a folded curtain that hangs
from the roof of the pharyngeal cavity. The tubular pharynx is a cylindrical or bell-shaped
projection arranged horizontally inside the pharyngeal cavity (phc) and it opens to the
outside across a ventral gap called the mouth (m) (Figs. 2–4).

367
Prostatic vesicle (pv) An organ composed of a muscular wall and glandular inner lining. The glandular epithelium
can be smooth (Fig. 7), ridged or folded. When the folds of the glandular epithelium form
tube-like projections occupying the inner space of the prostate is called ‘in chambers’
(Fig. 8). If the ejaculatory duct runs through the prostatic vesicle, the sperm then cross this
organ as well; this disposition is called ‘interpolated’ (Fig. 8). If the prostatic vesicle is found
separated, like a blind sac, the sperm do not traverse this organ and thus the contents of the
vesicle are led across a prostatic duct (pd) up to the penis or cirrus. This disposition is called
‘free’ (Fig. 7).
Seminal vesicle (sv) Muscular organ of varied forms that receives the vasa deferentia and stores the sperm (Figs.
5, 7&8).
Spermiducal bulbs (sb) Expanded distal portion of the vasa deferentia that serves for storage and propulsion of the
sperm (Fig. 6).
Stylet (s) A penis papilla that can develop at its distal end a sclerotised projection in the form of a
hollow tube. The sclerotised stylet is a structure that may be of varying lengths, straight,
curved and even coiled. It is wide in the proximal region, slimming distally up to a sharp
distal end. When the penis possesses a stylet, is said to be ‘with armour’ or ‘armed’ and
works like a copulatory organ by protrusion to the exterior (Fig. 5).
Sucker (su) Glandulo-muscular adhesive organ, usually located behind the pharynx, on the ventral
surface of the Polycladida Cotylea (Fig. 2).
Tentacle s Dorsal sensory projections from the surface of the body. The nuchal tentacles are projections
located on the region of the brain (Figs. 1&3), and can be lengthy, conical and scarcely
developed or rudimentary. The marginal tentacles (mt) are folds of the anterior border of the
body, also called pseudo-tentacles (Figs. 2&4).
Uterine vesicles One or more secondary chambers used exclusively for the storage of the eggs.
Uterus Relatively spacious region of the female reproductive system where the eggs are stored
before being released.
Vagina (v) Terminal region of the female duct, located at the opposite end to that of the oviduct (Fig. 6).
In some cases, the muscular portion of the vaginal wall is strongly developed, which is
known as a vagina bulbosa (vb) (Fig. 5).
Vasa deferentia (vd) Also known as vas deferens, it is a sperm duct that runs along the median region of the body
from the testes to the seminal vesicle, usually paired (Fig. 6).
from the Brazilian coas t. Boletim Facultade de Filosofia, Ciências
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Du Bois-Reymond, E. & Marcus, E. (1968) Polycladida from Curacao and
faunistically related regions. Studies on the Fauna of Curaçao and
other Caribb ean Islands, 26: 1-133.
Faubel, A. (1983) The Polycladida, Turbellaria. Proposal and establishment
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Herzig, E.M. (1905) Laidlawia trigonopora n. gen. n. sp. Zoologischer
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