Head Structures of Pherusa papillata
I.K. Berzins
Introduction
Species of the family Flabelligeridae, a group of sedentary marine
polychaetes, show some unique specializations at the anterior end. The head
and its appendages are fully retractile, and when extended are still encased
in a large "cephalic cage" of anteriorly directed setae. Day (1967) and
Hartman (1969) offer general accounts of the family. Two large German monographs.
Gunther (1912) on Flabelligera diplochaitus and Schlieper (1927) on Pherusa
(Stylaroides) plumosus, provide good anatomical and morphological accounts of
the species concerned, but do not contain many details on behavior and function.
Spies (1971 § 1975) begins to account for a variety of functions associated
with feeding, respiration, excretion and sensory perception in the worm
Flabelliderma commensalis and mentions several other species of flabelligerids
for comparison, but presents primarily further morphological information. A
functional understanding of the complex anterior end of flabelligerids is still
far from complete.
The purpose of this study was to investigate the functional morphology
of the head structures of a flabelligerid, Pherusa papillata (Johnson,1901),
and to investigate some aspects of the relationships between these head
structures and the life habits of the worm. The species is well known to
systematists (e.g. Hartman, 1969), but little is known in detail of its structure
and behavior.
Head Structures of Pherusa papillata
I.K. Berzins
Materials and Methods
The study was done at Hopkins Marine Station of Stanford University in
Pacific Grove, California during April and May, 1976. Specimens were collected
subtidally roughly 1,500 ft. to the east of Mussel Point, Pacific Grove, at an
average depth of 30 ft. The worms were found in the loose, small-grained sands
associated with well developed (high vs. low density) Diopatra ornata communities
which were located at the outer edges of kelp (Macrocystis) beds. The worms
were collected by hand, with a dredge and by taking shovelfuls of sand, which
were transported to the laboratory in plastic bags.
A binocular dissecting microscope and a hand lens were used to observe
live specimens. Carmine red and graphite particles were used to indicate ciliary
currents. For anatomical study, worms were relaxed in equal parts of seawater
and of a MgCl, solution isotonic with sea water. Some specimens were fixed in
Bouin's' solution prior to dissection. Fine anatomical details were observed
under a compound microscope.
The majority of living worms were kept in the laboratory in uncovered
plastic pans filled to a depth of 4-5" with sand taken from the collecting
areas, and provided with running sea water at a temperature of about.1200.
Several worms were kept in seperate glass bowls. Altogether 32 worms were
collected.
Head Structures of Pherusa papillata
I.K. Be
Gross External Morpholog
The body of Pherusa papillata is cylindrical and tapers posteriorly (Fig.1).
Dimensions of all specimens are given in Table 1. The average length was 4.5 cm.,
average diameter .25 cm., and the average number of segments was 71. There was
not a strong correlation between size and number of segments. The body surface
is soft and papillated, with a light distribution of small sand grains embedded
in the body wall at the bases of papillae. The sand grains are most densely
distributed at the dorsal surface of the head region, where the papillae are
largest and most concentrated, but even here the embedded sand does not form
a definite crust. Papillae are absent in the segment boundaries, making ex¬
ternal segmentation fairly clear.
The body is olive green in color with the exception of the first three or
four setigerous segments which instead are orange in color and lighter ventrally
than dorsally. The main body color blends with the color of the sand, offering
some possible camouflage value.
In cross section the worm is eliptical with the dorsal surface rounded and
the ventral side slightly flattened (Fig. 9). Occasionally the anterior third
of the body exhibits bulges, and a dark green or a whitish color can be seen
through the body wall. Spies (1971) mentions that green ovaries and white
testes are present in mature individuals. A pulsating vessel can be seen
through the dorsal body wall, sending green-pigmented blood anteriorly. The
setae of the first setigerous segment are greatly elongated and directed for¬
ward, forming the cephalic cage characteristic of the Flabelligeridae. The rest
of the segments have shorter simple straight notosetae (Fig.2) and simple hooked
I.K. Berzins
Head Structures of Pherusa papillata
neurosetae (Fig.3). The head (Fig.4), formed by the fusion of the prostomium
and peristomium, bears eight green branchiae, two fleshy palps, eyespots and
three large protruding lips. It is retractable and can withdraw deeply into
anterior body somites. When everted the head is surrounded and enclosed by the
long setae of the first setigerous segment. Posteriorly, at the tip of the tail,
is a dorsally positioned anal opening. More detailed considerations of partic¬
ular structural elements on body regions appear below.
Papillae
The papillae covering the body vary in size, density, shape and distribu¬
tion (Table 2, Figs. 5-8). Dorsal papillae are larger than those in correspond-
ing on the ventral side, and all the papillae decrease in size posteriorly.
Anteriorly, the papillae are oriented forward, posteriorly they point back. The
number of papillae per unit area at a given level on the body is greater ventrally
than dorsally and the density of papillae also increases posteriorly in the
tapered portion of the body. Wart-like papillae cover most of the body, while
the elongate and nipple-like papillae are located primarily in close proximity
to one another at the bases of setae. Especially prominent are the two
nipple-like papillae at the base of each sheaf of notosetae (Fig.7). The first
three setigerous segments have especially long, club-shaped papillae in high
densities. Spies (1971) mentions the presence of possible nerve fibers in the
club-shaped papillae and notopodial papillae in Flabellidermata commensalis.
The papillae may be serving as sensory structures, but their specific functions
were not obvious in the present study.
Head Structures of Phert
I.K. Berzins
Noto- and Neuropodial Setae
Each setigerous segment (excluding the first three chaetigers) has two
bundles of straight, fine, simple setae dorsally and two bundle of shorter,
thicker, simple,hooked setae ventrally(Fig.9). Parapodia are poorly developed,
and are present only as slight bumps. The notosetae in each parapodium numbered
5-9, the specific count being constant on individual worms. On a worm 5.2 cm.
long they averaged 1.7 mm. in length with shafts about .19 mm. in diameter.
They are a light yellow color and are marked with longitudinal and transverse
striations, the transverse intervals increasing in length distally (Fig.10).
Near the attached end the transverse striations form thin, fine lines (Fig.11)
as described by Schlieper (1927) but at the tips they become wedged shaped (Fig.12)
as Gunther (1912) describes them. The tips of the setae are very thin and
flexible, suggesting the wedge shaped transverse marks represent interruptions
of the longitudinal (themselves internal fibrils?) increasing setal flexibility.
Externally the setae are arranged in an open fan pattern (Fig.13), each seta
projecting out from an individual opening. The fan arrangement results from the
internal spiral positioning of the attached setal bases (Fig.14). The spiral
is not a symetrical arc but is rather elongated in one direction (Fig.13, the
solid line). Regularly interspersed between the bases of the notosetae are
fine straight setae, with faint transverse striations.They have hooked roots,
as compared to the straight roots of the longer notosetae, and do not project
beyond the body wall. The notosetae are non-retractable and move back and forth
as a result of body motion (Fig.15). The notosetae may play some type of
sensory role, for when lightly touched, the segments bearing the disturbed setae
contract (Fig.16). The two nipple-like papillae close to the setal bases, if
they are neural structures, may also be involved.
I.K. Berzins
Head Structures of Pherusa papillata
In a neurosetal bundle there are four hooked bristles arranged in a vertical
line which project out perpendicular to the body wall (Fig:17). They are all
of different lengths, the longest being the most dorsal, the sizes progressively
decreasing ventrally, and the shortest being the most ventral. The lengths
range 1.4-.8mm for a 5.2 cm worm. They are shorter and thicker (0.48 mm)
than the notopodial setae. Both types of striations are present, but the
transverse intervals decrease distally (Fig.18). The setal tips are not flexible
possibly related to the fact that transverse wedges interrupting long striations
are absent. Internally the bases are again spirally arranged (Fig.17). The
farther up the spiral, the shorter and more ventrally located the seta is
externally. Small straight setae are present at the bases of the neurosetae.
Schlieper (1927) mentions their possible role as remnant aciculae. The
neurosetae can retract, rotate, and move back and forth. They are less responsive
to disturbences than the notosetae.
In the first 10-12 setigerous segments, both sets of setae are directed
forward (Fig.19). Thereafter the setae begin to point posteriorly. The
notosetal fans are oriented vertically in the same anterior segments and then
become oriented horizontally (Fig.20).
Head Structures
The prostomial and peristomial structures have fused together without
a boundary to form the head. Spies (1975), for Flabellidermata commensalis,
makes the distinction that the prostomium bears the eyes, dorsal lip, the
nuchal organs (a sensory structure), and palps, while the peristomium bears the
median and ventral lips, the nepridiopore and branchiae. Hartman (1969) makes
no distinction.
I.K. Berzins
Head Structures of Pherusa papillata
The head lacks setae and papillae. Located on a dorsal, semicircular
ridge are sight, blunt-pointed branchiae (Fig.21). They are ciliated, creating
a current that moves anteriorly, away from the head. When extended, they show
no motile of contractile abilities. On a worm 5.2 cm long they are 0.45 cm in
length and 0.04 cm in diameter.
The palps, whitish in color, have a ventral groove with a lobed margin;
in the groove a ciliary current accompanied by a film of mucus moves toward
the head. Dorsally each palp bears another ciliated tract, in a slight
depression whose current moves away from the head. The palps are highly
mobile and are able to contract and extend considerably. They move about on
the surface of the substratum, picking up sand and loose detrital material in
the ventral groove and transporting it towards the mouth. Some particles are
dropped along the way; the lips bordering the ventral groove can flex out-
ward (Fig.22) allowing the particles to drop. The rest of the particles are
carried further and are dropped at the base of the palps, forming a "sand-pile'
(Fig.23) on either side of the mouth. There is no connecting groove between
the palps and lips.
Dorsal to the palps is a small triangular lobe bearing four cresent-
shaped eyespots.
There are three lips; two large, protruding median lips and a puckered
ventral lip. They are a light orange-pink color. A small membrane connects
the lips to the outer branchiae. The lips exhibit muscular movements (Fig.24).
The median lips move outward and upward as the ventral'lip moves downward and
outward. Then the median lips move back, as does the ventral lip. This is
accompanied by downward peristaltic movements along the base of the lip,
reminiscent of swallowing.
I.K.Berzins
Head Structures of Pherusa papillata
A worm in a natural position in the sand is able to protrude the lips into
the pile of material deposited by the palps, shoveling and scooping it into the
mouth. To check if the worms were actually ingesting the sand, the contents
of worms freshly collected from the field and of worms that had been kept
for several days in the laboratory were made. The guts were always filled with
sand. The average dimensions of the sand ingested were 0.24 x 0.18 mm, with
an occasional large particle (1 mm). Comparing the sizes and types of sands
available in the field to what is in the gut, it is apparent that a selection
process is occuring, with the palps and perhaps the lips providing the sorting
mechanism (Tables 3-4). Fecal matter consisted of sand, detritus, and sometimes
setae. It was occasionally expelled as pellets enclosed in a very delicate
mucus membrane, but usually it was loose.
The forward current created by the branchiae removes water from the region
ventral to the head. Replacing this a flow of water passes from dorsal to
ventral between the branchiae (Fig.21); suspended detritus is thus brought in.
Some of it is carried out again by a strong current created by the ciliary fringe
of a small red-colored ridge on the ventral side of the head posterior to the
branchiae. Some of the suspended detritus brought in is carried by a small
ciliary path starting between the bases of the two palps and leading into
the mouth. This may be a secondary feeding mechaniwm. A few of the worms eg
collected had palps of different sizes, one being shorter than the other. In
the laboratory, one worm place in a dilute solution of MgCl automized both
palps. Regeneration to a functional condition occured within three weeks.I
Loss and regeneration of one or both apparently occurs in nature. Animals le
lacking palps can ingest sand with the lips but they may also rely on this
secondary feeding mechanism.
I.K.Berzins
10
Head Structures of Pherusa papillata
The Cephalic Cage
When extended, the head is surrounded by the elongate setae of the first
three setigerous segments, notably those of the first (Figs.4,25). Setigers 1-3
show a progressive increase in size, and their setae undergo considerable wo
modification. On each side of each somite the dorsal and ventral setal bundles
are drawn closer together. The neurosetae are straight, like the notosetae,
and all setae bear longitudinal and transverse striations. Both noto- and
neuropodial setae increase in number and length progressively as one moves an
anteriorily. The longest setae from the first segment of a worm 5.2 cm long
were 0.76 cm. The fourth setigerous segment had four hooked neurosetae and
five straight notosetae. The second and third segments bore six straight
setae in each setal bundle, and the first setigerous segment had ten straight
notosetae per bundle and seven straight neurosetae. The notosetae here are
up to .029 cm in diameter but the neurosetae still remain larger. The notosetae
of the second and third segments are slightly longer than the neurosetae but in
the first segment the situation is reversed.
The setae of chaetiger one show a precise arrangement. The shortest and
finest setae are located laterally; setae become progressively longer as one
moves dorsally and ventrally creating a cage-like structuré (Fig.25826). The
dorsal most and ventral most setae begin to shorten but only slightly. The
tips of the setae are very fine and flexible. The dorsal setal tips curve
downward and the ventral setae curve inward. As a result, the characteristic
cephalic cage is formed by the first segmental setae. It is semicircular in
a cross-sectional view and is open ventrally (Fig.27). When expanded, the
setae create an encaged cavity in which the extended head apparatus lies.
The branchiae do not extend beyond the tips of the setae, they lie totally
Head Structures of Pherusa papillata
I,K. Berzins
11
within the cage. A steady current enters the dorsal side of the cage, at
the base of the setae, and is directed forward, exiting at the anterior apex
of the cage (Fig.26).
The bases of the setae of the first chaetiger, buried in the body wall,
are surrounded by a common membranous sheath(Fig.29). The setae spiral just
before they project externally. Between the setal bases, lying ventraltto the
internal setal sheath are two overlapping triangular sheaths (Fig.30) which
completely enclose many fine, slightly striated setae (Fig. 31). The same was
observed for the setae of the second and third setigerous somites, though-
they show slight differences in the positions of these extra bundles (Fig32 ).
The uppermost tips of the buried bundles protrude slightly outward (Fig. 33.)
producing slight bumps lataral to the main setal bundles, but they do not project
through the body wall.
The position of the head was observed only under laboratory conditions.
It was held at a diagonal (Fig. 28) with the ventral side directed downward and
forward, and with either the dorsal portions of the first few segments or
just the setae of the first segment exposed at the surface of the sand. The
meshes of the cephalic cage create an effective grid which does not allow
sand particles to enter. Placing the worms in different sizes of sand, the
setae adjusted the size of the grid accordingly and proved very effective in
keeping out particles. The worm occasionally withdrew its body into the sand,
leaving only the tips of the setae exposed, surrounding the cage with sand.
Again the grid was adjusted and kept the cavity clear of sand.
Slight disturbances, such as lightly touching the anterior regions
(especially touching the club-shaped and elongate papillae) or slight vibrations,
caused the head to retract quickly and the setae to close tightly together,
"cross-hatching"(Fig.34) at the distal ends, creating a sort of operculum
protecting the withdrawn head.
Head Structures of Pherusa papillata
I.K.Berzins
12
When portions of the dorsal surfaces of several of the anterior segments
are exposed, notopodial setae of the second and third chaetigers are spread
open keeping the area free of sand (Fig.35). This area has the large club¬
shaped papillae in high concentrations.
When the setal cage is expanded and the head extended, the palps extend
along the substratum under and well beyond the edges of the cage (Fig.27).
Though the palps can move in many directions and their range is large, they do
most of their foraging in a limited area (Fig.36, shown by the dashed line).
A lateral view (Fig.37) shows that a slight depression is created around the
worm where the palps have foraged. This is cleared of detritus and small sand
particles. A small ridge forms around the head (Fig.37) built up by larger
particles which were brought in by the palps but have been rejected. Worms
were frequently observed to retract their heads, close up their anterior setae
and use these anterior setae to sweep the immediate area. This removed the
built-up ridge and may have uncovered some buried detritus and sand suitable
for ingestion. Watching one worm for a period of four hours, this sweeping
motion occured at intervals averaging 13 minutes. Also, while sweeping, the
worm often shifted the direction of its head (Fig.38) enabling the palps to clear
the feeding radius for a full 360°. The worm never fully rotated; reaching
a certain point in rotation, the worm reversed and turned in the other direction,
A restriction is placed on the rotation of the head by the position taken by
the remainder of the body.
Frequent contact between sand and setae fof the cephalic cage inhibits the
settlement of organisms on the setae; vorticellid ciliated protozoans were found
growingeon the setae only within the cavity, on the medial surface of the setae,
Head Structures of Pherusa papillata
I.K. Berzins
13
Body Position
In laboratory situations the worms formed U-shaped burrows with the head
and tail at the surface (Fig.39). The body is greatly elongated compared to
its length when out of the sand. The worm, while rotating its exposed anterior
portion, appears to be twisting the body; it apparently does this only so far
in each direction for there is not a complete rotation of the head at the
surface.
At the posterior end,assmall mound ofldefected sand eöf thessame size
asmthatzfoundtinttheugut; is formed and around the head is the slight depression
which lacks detritus and small sand grains. The burrow is not strongly
consolidated, though a small amount of mucus is produced by the worm which may
line the tube to provide some support, When removing worms from sand, no
strongly formed tube was found and the animal was not surrounded by a thick
mucus coat.
Within the tube, the worm moves its tail up to the surface and retracts
it. The anterior end occasionally withdraws into the sand, the particles of
sand collapsing the opening of the burrow. In laboratory burrows where portion
of the body was visible, pressed against the side of a glass bowl, the worm
moved within the burrow by slight peristaltic and sinusoidal waves, with
some twisting.
A more complete picture of movement in the burrow was not obtained but
in worms fully exposed at the surface of the sand locomotory movements were
observed. Peristaltic waves and lateral undulatory waves moved anteriorly;
at the same time neurosetal hooks were projected outwards with the hooked tips
pointing downward and posteriorly, acting as anchor points for the passing
waves. The head was usually retracted and the cephalic cage closed but
occasionally both were extended. The setae of the first chaetiger were not
in
Head Structures of Pherusa papillata
I.K. Berzins
14
involved in locomotion but were held above the surface of the sand. The
ventral setae of the second and third segments acted as sweeps, shoving
sand posteriorly as the waves passed. The notopodial setae remained spread
and were not involved in locomotion. A slight furrow formed on the sand surface
as the animal moved forward.
The burrows seen in the laboratory are not permanent ones, and the worms
are able to change positions. In a large bowl of sand containing one worm,
three detritus-free areas were seen on the surface of the sand after several
days. Each was about 3.5 cm in diameter and seperatéd by about 1.2 cm. No
furrows connected the areas, indicating that the worms did not crawl out to
change positions or plow through the sand with the head still at the surface
(This can be done slightly, the worm inching forward a bit while buried in the
sand. The setae of the first segment are not used). Position change must have
occured beneath the sand surface. Burrowing was not observed beneath the sand,
but burrowing types of movements were observed at the surface. Remaining in
place, sinusoidal waves were sent both anteriorly and posteriorly. The posterior
portion, with the aid of extended neurosetal hooks, dislodged the sand beneath
it and worked its way under the surface. The notosetal fans remained spread
open and wére not usedfor burrowing. Anterior moving waves ceased replaced
by posterior moving peristaltic waves. The anterior region slid back and under
the sand.until all that remained exposed were the first few setigerous segments.
After covering the glass bowl, no new cleared areas formed. The worm r.
remained in one place with its head continuously at the surface.
Feeding with the palps apparently does not occure while the worms are
underneath the sand. A dish filled with sand from the Diopatra beds was
covered with a thin layer of crushed green glass beads, the bead particle
sizes being larger than the sand grains normally ingested. This prevented
Head Structures of Pherusa papillata
I.K. Berzins
15
ingestion of surface particles, therefore any ingested particles would have
to be from the natural sands. The bowl was not covered. The fecal pile that
formed contained few natural sand grains, only detrital material with minute
sand grains. The worm spent part of the time with its head at the surface
and part of the time submerged. It was considered possible that the palps
could be extended even with the worm submerged. The setae forming the cephalic
cage do close when the anterior end withdraws into the sand, but once below
the surface the setae may open and clear an area to allow the branchiae, the
major respiratory organs (Spies, 1971), to extend. To account for the detrital
matter found in the feces, the worm may have used its secondary feeding
mechanism (page 9) in the sand and at the surface. While at the surface, the
palps did not pick up the larger crushed beads, but they were waved about in
the water as though to catch detritus particles in suspension.
Additional Observations
The following observations of behavior and responses to stimuli are
fragmentary but provide some interesting leads for future work.
The worm is extremely sensitive to light. A bright light concentrated on
the head resulted in withdrawl below the sand. A light shined on the underside
of a petri dish containing a worm, caused the worm to turn over with its
dorsal side down. Changing the position of the light source, so that it shone
from above, caused the worm to flip back.
When placed on sands of different size-grades, the worm burrowed sooner
and faster in the larger particle sizes. However, with coarse sand the "scoop
intervals (the intervals between sweeping motions of the head and setae, page 12)
were much shorter, a matter of seconds as compared to minutes for the smaller gizes.
San.
Head Structures of Pherusa papillata
I.K.Berzins
16
In addition to burrowing and crawling motions, the animals can swim, with
an upward spiraling motion.
An interesting response occured when worms, exposed on the surface and for
some reason not burrowing, contacted a Diopatra tube. A worm contacting the
tube immediately begin to burrow next to it or to wrap itself around the base
of the tube. In the natural habitat from which Pherusa was collected, Diopatra
ornata builds vertical tubes which project deep into the sediment. This
stabilizes the bottom substrate, and may create a preferable environment for
sand dwellers such as Pherusa papillata, which feed on the surface and do not
have strongly consolidated tubes. It would seem advantageous for Pherusa to
be able to dectect the presence of Diopatra tubes, and to burrow near them.
IK.Berzins
Head Structures of Pherusa
Summary
Pherusa papillata is a sand-dweller inhabiting a U-shaped burrow. It
is a surface deposit feeder ingesting inorganic and detrital matter. Sand
particles are picked up and sorted by two highly mobile palps. Muscular
lips shovel in the particles brought to it by the palps.
The highly modified anterior setae of the first three setigerous segments
create a protective cage within which, when open, the retractile head lies.
The setae form a grid, du- to a mesh created by the specific arrangement of
the setae, which is effective in keeping sand particles from entering the
enclosed cavity. The grid adjusts to different sand sizes, preventing sand
from entering and disruption of the strong ciliary currents of the head which
are important for feeding and respiration. When the head is retracted the
setae close tightly acting as an operculum and protecting the anterior end.
Acknowledgements
I would like to thank Dr.D.P.Abbott for his continous advice, encouragement
and patience; and to Jim Watanabe, who was a great diving buddy.
Head Structures of Pherusa papil
I.K. Berzins
18
References:
Day,J.H. 1967. A monograph on the Polychaeta of southern
Africa. Pts. 1-2. Trustees British Museum (Natural
History). 878 pp.
Gunther,K. 1912. Beitrage zur Systematic der Gattung Flabelligera
und Studien uber den Bau von Flabelligera (Siphonostoma)
diplochaitus. Ott. Jena. Zeitschr. Naturwiss. N.S.
48:93-186.
Hartman,O. 1969. Atlas of the Sedentariate Polychaetous Annelids
from California. Allan Hancock Found. University of
Southern California. 812pp.
Schlieper,C. 1927. Stylaroides plumosus eine monographische
Darstellung. Zeitschr. Morph. Oekol. Tiere, Berlin.
7:320-383.
Spies,R.B. 1971. Contributions to the functional anatomy,
reproduction and larval development of Flabellidermata
commensalis (Moore, 1904). Ph.D. Dissertation.
University of Southern California.
Spies,R.B. 1975. Structure and function of the head in
flabelligerid polychaetes. J.Morph. 147:187-208.
Head Structures of Pherusa papillata
I.K.Berzins
Pherusa papillata
Fig. 1:
Dorsal view of entire worm with
head retracted.
Fig. 2 :
Notoseta
Fig. 3 :
Neurosetal hook
Ventral view of anterior end.
Fig. 4 :
head extended; the right palp,
and right branchial tentacles
of the first chaetiger are
amputated at their bases.
19
Head Structures of Pherusa papillata
ae
Sa
2.8.2

S
Sa

23
7213
Dorsal view
7—

branchial
tentacle

4-
Fig. 1
7-
4

eyespots
anus
Pherusa papillata
I.K.Berzins 20

Fig. 2
Noto-

Fig. 3
Neuro -
palp
IIps

Fig. 4

o

Ventral View
I.K. Berzins
Head Structures of Pherusa papillata
21
Table 1. Measurements of all Pherusa papillata examined. Worms marked with
and asterisk had posterior ends broken, due to injury in collecting.
No. of segments
Greatest diameter(cm.)
Length (cm.)
.30
6.0
.30
6.0
6.0
5.8
.40
.25
5.5
.50
5.2
.45
.30
4.8
.30
4.6
4.6
41*
4.5
4.4
4.4
4.3
4.2
4.2
37*
4.1
4.0
4.0
4.0
.20
4.0
.20
40*
25
40*
25
3.6
3.1
.20
3.1
.30
2.4
42
15
20
1.2
Average length = 4.5 cm.
Average diameter =.25 cm.
Average no. of segments - 71
I.K.Berzins
Head Structures of Pherusa papillata
Table 2. Shapes, lengths and densities of papillae.
Length- mm.
Shape
No.
.38
Club-like
Elongate
.42
Slender elongate
.31
Wart-like
.17
.28
Nipple-like
.29
.21
.15
Wart-like
.25
Wart-like and elongate
9
11
11 11
10
.18
* Refer to Figs. 5-8 for the locations of papillae
Density
mm.
very
29
2
38
45
67
Head Structures of Pherusa papillata
I.K.Berzins
Pherusa papillata
Fig. 5 :
Lateral view of entire worm
Lateral view of setigerous
Fig. 6 :
segments 1-3, showing locations
of the different types of papillae
present on the body surface. Refer
to Table 2 for shapes, lengths and
and densities of the papillae.
Fig. 7
Lateral view of setigerous
segment 7.
Lateral view of setigerous
Fig. 8
segmnent 29.
23
Head Structures of Pherusa papillata
= segments 1-3
R = segment 7
= segnent 29
Fig. 5
Lateral View
C
B

Fig. 6
17.



S
Fig. 7
4.

Wobors
Fig. 8
I.K. Berzins
Head Structures of Pherusa papillata
Pherusa papillata
Fig. 9 :
Cross-sectional view showing positions
of noto- and neurosetal bundles. Reveals
flattened eliptical shape.
Transverse interval lengths of notoseta
Fig.10 :
Shape of transverse striationseatthe
Fig.11 :
base of the notosetae as described by
Schlieper (1927).
Fig.12 :
Shape of transverse striations at the tips
of the notosetae as described by
Gunther (1912).
25
I.K. Berzins
Head Structures of Pherusa papillata
26
V
Notosetae
Neurosetae

O
Fig.9



smaller transverse
faint
striations
striations


larger transverse
striations
Fig. 10
longitudinal
striations
Tip of setae
Base of setae
Fig. 11
Fig. 12
I.K. Berzins
Head Structures of Pherusa papillata
Pherusa papillata
Fig. 13 : Open fan arrangement of external
notosetae. Internally, setal bases
spiral to form an irregular arc(dark
line).
Closer view of internal spiral arrangement
Fig. 14 :
of notosetae. Short setae (dark colored)
do not project beyond the body wall. They
are regularily interspersed with the notosetae.
Short setae have hooked roots.
Movement of notosetae due to body motions.
Fig. 15 :
Contraction of body segments due to notosetal
Fig. 16 :
disturbence( represented by arrow).
Head Structures of Pherusa par

t.


Fig. 15
Dorsal view.
I.K. Berzins
Fig. 13
Fig. 14

I
Kr
L
Fig. 16
I.K.Berzins
Head Structures of Pherusa papill
Pherusa papillata
Fig. 17 :
External and internal arrangement of
neurosetae. Short straight setae present
at bases of neurosetae, not project beyond
the body wall.
Transverse and longitudinal striation patterns
Fig. 18 :
of neurosetae.
Fig. 19 :
Orientation of noto- and neurosetae.
Orientation of notosetae.
Fig. 20 :
29
Head Structures of Pherusa papillata
I.K. Berzins
Striations
absent
Small tranverse
intervals; longitu-
dinal striations
have become
diagonal.
Large transverse
intervals.
Fig. 17
Faint
striations
—

1111
Post.

21
110
Fig. 19 Dorsal view
+ 10 - n
Dorsal view
Dorsal view
X-section
Fig. 20
30
Fig. 18
Ant.
f1 - 10
X-section
Head Structures of Pherusa papillata
I.K.Berzins
Pherusa papillata
Tables 3 & 4 :
Sand sizes were obtained by using six
Tyler-Standard screens of mesh sizes 2.362.
1.397, .991, .495, .246 and .125 mm.
Krranged in this order on a Cenco-Meinzer
Sieve Shaker, sands were sorted and were grouped
into catagories by what had accumulated between
screens. One liter of dried sand from the
collecting areas was used.
Examination of the gut contents of two
worms from the field were compared with
mall samples of sands from the collecting
areas to determine further selectivity.
I.K.Berzins
Head Structures of Pherusa papillata
32
Table 3: Percentages of different sand sizes present in one
liter of sand from the collecting site.
Sand size
olo ot 1 1it.
36%0
S 2.362 mm
1.08%0
2.361 - 1.397 mm
2.15%0
1.396 -.991 mm
5.92%0
990 - .495 mm
70.38%0
.49 - .246 mm
ave. size
ingested:
19.39%/0
.245 - .125 mm
.24 mmx.18 mm
.720
.125 mm«
Table 4: Percentages of different types of sand found the the
collecting sites vs. types found in the gut of Pherusa papillata.
in gut
Type of particle
in field
84%0
77%0
quartz
16%0
14%/0
shell
2%0
mica flakes
70/0
Head Structures of Pherusa papillata
I.K. Berzins
Pherusa papillata
Fig. 21 :
Ventral view of head. Dark arrows
represent current flow.
vl = ventral lip
ml = median lip
p = palp
es - eyespots
r - ridge, with the ciliated fringe
b = branchiae
Fig. 22 :
Cross-sectional view of palp. Shows
flex of ventral groove.
33
Head Structures of Pherusa papillata





m
C

P


Fig. 21
dorsal

ventral
Fig. 22
I.K. Berzins
34
Ventral view
e
I.K. Berzins
Head Structures of Pherusa papillata
Pherusa papillata
Fig. 23 :
Lateral view of the extended head. Large
arrow represents the depositing of sand carried
by the palps. "Sand-pile" is formed which is
built up below the lips.
Muscular movements of the median and ventral lips.
Fig. 24 :
Striped arrow represents peristaltic movement.
Head Structures of Pherusa papillata
I.K. Berzins
S


,
Branchia &


palp
Lips
sand-pile"
S

Fig. 23 Lateral view

n
a
vl
O


—
Fig. 24
Ventral views
Lateral views
36
I.K.Berzins
Head Structures of Pherusa papillata
Pherusa papillata
Fig. 25 :
Dorsal view of the cephalic cage formed
by the first segmental setae.
Fig. 26 :
Lateral view of the cephalic cage. Dark
arrows represent current flow.
Fig. 27 :
Cross-sectional view of the cephalic
cage taken at the dashed line in Fig. 28.
Setae arranged in a semicircle with branchiae
and palps enclosed.
Lateral view of the first four setigerous
Fig. 28 :
segments showing position of the head as it
is in the sand.
P
Head Structureg of Pherusa papillata
HOA
Fig. 25
Fig. 28
Lateral view
I.K.Berzins

LATERAL
Fig. 26
D
00000
branchiae
palpso
Fig 27 X-section
I.K. Berzins
Head Structures of Pherusa papillata
Pherusa papillata
Fig. 29 :
Bundle sheath of the first segmental
setae.
Positions of the two smaller membranous
Fig. 30 :
sacs, ventral to the first segmental setal
bundle.
Contents of the small triangular bundle; numerous
Fig. 31 :
small straight, finely striated setae.
39
Head Structures of Pherusa papillata
I.K. Berzins
Fig. 29
Head Structures of Pherusa papillata
Fig. 31
Fig. 30
I.K. Berzins
41
I.K. Berzins
Head Structures of Pherusa papillata
Pherusa papillata
Positions of the extra setal bundles
Fig. 32. :
of setigerous segments 2 and 3.
External view of bumps (b) created
Fig. 33 :
by the positions of the extralsetal
bundles.
Fig. 34 :
"Cross-hatching" of the first segmental
setae when they close.
Fig. 35 :
Elongate notopodial setae of segments
2 and 3 keep the dorsal portionsoftthe
anterior most segments clear of sand when
they are exposed.
42
Head Structures of Pherusa papil.
MAN
I.K.Berzins
114
Fig. 32
1 b
Fig. 33
Fig. 35
Dorsal view
Fig. 34
I.K.Berzins
Head Structures of Pherusa papillata
Pherusa papillata
The range the palps extend to is shown. The
Fig. 36 :
arrows indicate the mobility of the palps while the
dashed line indicates the area foraged the most
frequently by the palps.
Lateral view of the head and of the range of
Fig. 37 :
the palps. In cl-aring an area of detritus and
small sand grains, the palps create a slight
depression around the head. A small ridge of
large sand grains forms immediately next to the
head, having been rejected by the sorting mechanism
of the palps.
The direction in which the head points changes
Fig. 38:
frequently. The arrows indicate the direction of
the setae after the head has rotated. Head rotation
reaches a point, marked by the dashed line, that
it does not go beyond, indicating some type of
restriction placed on the head by the position
of the worm's body in the sand. Reaching this
point the head reverses. Note that a back and forth
rotation is occuring, not a continous movement in
one direction and then back again.
44
. . I.K.Berzins
Head Structures of Pherusa papillat
1.8 cm

.9 cm



1.8 cm
Fig. 37
Fig. 38



45
Fig. 36
Head Structures of Pherusa papillata
I.K.Berzins
Pherusa papillata
Fig. 39 : The U-shaped burrow of Pherusa papillata.
116
Head Structures of Pherusa papillata


6.4 cm
I.K. Berzins
7.6 cm
1.2 cm

Fig. 39
47


1.8 cm