Microalgae on Shell
(1)
TRACT
ABS
A field survey and culture study of the microalgae
living on the shells of the intertidal prosobranch
mollusc, Tricolia pulloides (Carpenter, 1865), a-
round the Monterey Peninsula, California have identified
the microalgae commonly found growing on these shells and
have shown that some of these microalgae are in greater
abundance on shells from a wave exposed coast as com¬
pared to shells from a wave protected coast. Conchocelis
rosea Batters, a shell-boring red alga not expected in
high intertidal shells, was commonly found. An encrusting
green alga identified as Pseudopringsheimia apiculata
Setchell & Gardner showed free radiating irregularly
branched marginal filaments in monostromatic regions and
horizontally elongated cells in polystromatic regions,
neither of which had been described for P. apiculata
on macroalgal hosts.
Microalgae on Shell
(2)
INTRODUCTION
An extensive survey of the epizoic and endozoic
microalgae associated with the shell of a single species
of a living marine snail has never before been carried
out. The relative abundance of Tricolia pulloides
(Carpenter, 1865) around the Monterey Peninsula,
California (Firestone, 1979) and the smooth, semi¬
transparent character of the shell offered a convenient
opportunity for beginning such a survey.
The objective of this study was to identify the
microalgae found on the shells of T. pulloides and to
investigate whether or not there existed differences
in species or quantity of microalgae on the shells be¬
tween a wave exposed coast and a wave protected coast.
This study also led to an investigation of the habit of
a green alga placed in the Chaetophoraceae, a family of
green algae not fully understood.
MATERIALS AND METHODS
The specimens were gathered from four main study
areas on the Monterey Peninsula. Two areas, Point Pinos
and Point Joe, were on a wave exposed coast, and two
areas near Mussel Point were on a wave protected coast
(fig. 1). Three collection sites (+2.0 ft., +1.0 ft..
0.0 ft.) at each study area were selected relative
Microalgae on Shell
(3)
to 0.0 ft. tide level (mean low low water) and accor¬
ding to immediate macroalgal type (table 1). A sample
20 snails was collected at each site for culture
studies, and an additional sample of 20 snails was
preserved in 5% formalin for later observation. Col-
lections were made from May 10-15, 1979 during the neap
tides of that month.
The shell of each snail collected for culture
(240 in total) was cracked and the animal removed.
All shell fragments from five snails were placed in
separate plastic petri dishes (100xl5mm) containing
.45um filter-sterilized sea water enriched with modi-
fied Provasoli's media (Provasoli, McLaughlin, and Droop,
1957); 5 drops of Ge0» solution were added to each dish
to control diatoms. Two of the four shell cultures
from each collection site were placed at 15°0 with
constant light (40 watt, cool white, 46 microeinsteins
-2
-1
m sec ) and two were placed at 22°C with constant
light (40 watt, cool white, 150 microeinsteins müsec
After 6 and 9 days in culture, depending on the species,
specific microalgae were counted under a dissecting
microscope. Following the ninth day, samples of each
microalga were identified using a compound microscope
and photographed with a Nikon compound microscope
camera unit. The preserved snails were used to com¬
Microalgae on Shell
(4)
pare the microalgal forms in the field with those in
culture.
An additional 256 snails were sterilized in an auto-
clave (121 C, 20 lbs. pressure, 15 minutes). These
shells were then glued with epoxy to 4x8cm wood plates
(18 shells per plate), and the wood plates were bolted
to rocks at sites denoted in table 1, during May 10-15,
1979. The shells were examined for new growth of micro¬
algae after a 2-3 week period.
ESULTS
The results of this study are presented under three
categories: 1) frequencies of occurrence, 2) new growth
on sterilized shells, and 3) observations of form and
habit.
FREQUENCIES OF OCCURRENCE
Table 2 lists the microalgae encountered in field
and culture observations. Figure 1 depicts the numbers
of particular microalgae on the shells from the wave
protected coast and wave exposed coast study areas
as determined by culture counts. Figure 2 displays
the results of culture counts to determine frequency
differences between 15°0 cultures and 22 C cultures.
NEW GROWTH ON STERILIZED SHELLS
Table 2 shows that many species of algae observed
on the shells of living snails from the field were also
Microalgae on Shell
(5)
observed on sterilized shells after 3 weeks. Shells
placed at low sites showed the greatest amount of
new growth for any given area. On 10 shells from
a low site near Mussel Point the following new growth was
observed: 21 Enteromorpha sp. and Ulva sp., 1 Erythro-
cladia subintegra Rosenvinge, 13 Erythrotrichia carnea
(Dillwyn) J. Agardh, 12 Feldmannia chitonicola (Saunders)
Levring filaments, and general presence of Pseudo-
pringsheimia apiculata Setchell & Gardner.
OBSERVATIONS OF FORM AND HABIT
The following observations deal with those micro-
algae where the observed form or habit was of special
interest or differed from that hitherto described.
Conchocelis rosea Batters -- Shell-boring. Common at
all observed tidal heights. The thin, transparent
shell made possible direct observation under the com¬
pound microscope. Three distinct morphological forms
were observed. 1) Thin, usually straight filaments,
2.2um in width, with occasional short side branches.
Filaments contain very elongated pink cells (plate 1).
2) Thick to thin filaments, up to 9um in width, not
straight, branching common, becoming somewhat con¬
stricted between cells and near branchings, containing
pink somewhat elongated cells (plate 2). 3) Uniformally
thick filaments, 9um in width, cells dark in color, not
elongated, 4.5um in diameter (plate 3).
Microalgae on Shell
(6)
Erythrocladia subintegra Rosenvinge -- In culture, thallus
discoid, up to 224um in diameter. Cells in central
region polystromatic (plates 4,5).
Lyngbya sp. -- A blue-green alga very common especially
on shells from the wave exposed coast. Often the entire
shell is covered with tufts of this alga. 139um in
length, 4um in width. Appeared colorless in all
cases (plate 6).
Pseudopringsheimia
apiculata Setchell & Gardner -- Com-
mon. Lends grass green color to many shells. Usually
epizoic on shell surface, occasionally endozoic under
protein coat of shell. Cross-section shows apiculate
tips and polystromatic growth up to 10 cells thick (67um)
(plate 7). Cells in cross-section are in vertical rows
and horizontally elongated (2 times as wide). Top view
of growth on shell surface (plates 8,9) shows areas of
monostromatic growth at the margins, including free ir-
regularly branched cells 2.2um in width and llum long.
Cells of central region of monostromatic growth from
top view are 2.7-3.Zum in diameter. Cells have single
pyrenoid, small rhizoids(?), and parietal(?) chloroplast.
DI.
SSION
FREQUENCIES OF OCCURRENCE
The results in figure 1 suggest that the wave ex¬
posed coast favors all the particular microalgae counted
with the exception of Erythrotichia carnea. These re¬
Microalgae on Shell
(7)
sults are reasonable assuming that the exposed coast
has more dissolved oxygen and nutrients available
due to increased water turbulence.
The results in figure 2 suggest that the red algae,
Erythrocladia subintegra and Erythrotrichia carnea, and
the brown alga, Feldmannia chitonicola, are not well
adapted to warm temperatures, though E. carnea is
known from the tropics (Abbott and Hollenberg, 1976).
This seems consistent with a paper by Hoek (1975) which
suggests that species of algae living abundantly in
cooler thermal regions are usually not well adapted
to live in warmer thermal regions. The results in
figure 2 may also be due at least in part to the difference
in light intensities to which the two sets of shell
cultures were exposed.
NEW GROWTH ON STERILIZED
SHELLS
New growth on the shells was surprising in view
of the short time period. These results bring up the
question of why the Tricolia pulloides in the field
are not overgrown with algae. At least 70% of the
Tricolia observed from the field were less than 50%
covered with microalgae. Another snail, however, the
limpet Collisella limatula Carpenter, often seen at the
same tidal height as the higher of the T. pulloides,
Microalgae on Shell
(8)
is commonly completely covered with algae. The T.
pulloides in the field are not as exposed to light
as were the sterilized shells or as are the shells of
C. limatula, thus lack of sufficient light may account
for the lack of increased algal growth. Possibly
Tricolia pulloides graze upon each other or are
grazed upon by some other organism. Though such
grazing has been described for some intertidal snails
(Eikenberry and Wickizer, 1964) it was never observed
for T. pulloides in the field or in laboratory tanks
provided with macroalgal fronds. Such behavior was
only observed when snails were confined in small
containers without any other food. Yet another ex¬
planation is that the protein coat of Tricolia's shell
may inhibit algal growth. The question of why the
live T. pulloides in the field are only rarely more
than 50% covered with algae is a perplexing one which
I am unable to explain.
OBSERVATIONS OF FORM AND HABIT
Conchocelis rosea -- The fact that this shell-boring
alga was found in Tricolia's shells is an interesting
finding in itself. Conchocelis, an alternate morpho-
logical form of various Porphyra species (Tseng and Chang,
1956; Hollenberg, 1958), may serve to insure the sur¬
vival of Porphyra during times when the intertidal
Microalgae on Shell
(9)
habitat is under stress owing to intense sunlight,
high temperatures, or lack of large waves. Conchocelis
phases are more resistant to these physical stresses
than the large, blade-like Porphyra plants. These
Conchocelis filaments in Tricolia shells are at ap¬
proxiamately the same tidal height as locally occur-
ring Porphyra perforata J. Agardh.
While an enormous amount of work has been done on
the form and habit of Conchocelis in culture (Drew, 1949,
1957; Kurogi, 1953; Tseng and Chang, 1955, 1956; Hollenberg,
1958; and Dixon and Richardson, 1969), little if any
extensive work has been done with Conchocelis in the
field. The shell of Tricolia pulloides has proved to
be an excellent place to observe Conchocelis in the field.
The three distinct morphological forms observed each
correspond to similiar forms described by Tseng and
Chang (1954) and locally by Hollenberg (1958) as dif¬
ferent stages of Conchocelis. It is of interest that
Hollenberg described the Conchocelis stage of locally
occurring Porphyra perforata as free-living (not shell¬
boring) while the Conchocelis filaments in Tricolia
shells may likely represent the Conchocelis stage of
Porphyra perforata in a shell-boring situation. The
shell of T. pulloides offers an opportunity for study
of the seasonal variations, if any, in the abundance
Microalgae on Shell
(10)
of the three observed forms of Conchocelis in the field.
ythrocladia subintegra -- This alga has been described
from the field as monostromatic (Abbott and Hollenberg.
1976), but according to Nichols and Lissant-(1967) Ery.
throcladia subintegra in culture becomes polystromatic
with age, in agreement with this author's observations
in culture. This particular example demonstrates a
problem in present phycology, in that earlier descrip¬
tions of many species are based entirely on a few field
observations and often miss the morphological variability
present. This problem becomes more acute when one studies
inadequately defined taxa such as the genera and species
of the family Chaetophoraceae around the Monterey Peninsula.
Pseudopringsheimia apiculata -- Early descriptions of
many of the species of Chaetophoraceae described for
the Monterey Peninsula, including Pseudopringsheimia
apiculata, are based entirely on morphological attri-
butes observed in the field, often only on one or a
few hosts. Studies of thier habit, form, and pheno-
typic variability under a wide range of environmental
conditions have never been made. Yet, recent cultural
investigations of the family Chaetophoraceae by Wilkin-
son and Burrows (1972) and Yarish (1976) demonstrate
that serious taxonomic problems do exist in this family
due to earlier field descriptions which did not take
into account the extraordinary phenotypic plasticity
in members of this family.
Microalgae on Shell
(11)
It was within the above framework of knowledge
that this author had to work. Tables 3 and 4 illus-
trate the reasons for tenatively assigning the common
Chaetophoraceae alga seen on the shells to the genus
and species Pseudopringsheimia apiculata and also the
author's reservations about doing so. The differences
in habit between the alga on the shells and Pseudo-
pringsheimia apiculata may be due to a phenotypic
(not genotypic) difference resulting from the difference
in hosts from which the alga is being described. Yarish
(1976) concluded, "In the case of certain Chaetophoraceae
it is essential to culture the organisms to obtain
correct identification. Many species described in the
literature are probably ecophenes of a more limited
number of species." Comparative culture and field
studies of this alga and others in the Chaetophoraceae
from the Monterey Peninsula should be attempted in
order to better understand the taxonomy of this family.
Microalgae on Shell
ACKNOWLEDGEMEN
I would like to express my sincere appreciation
to William Magruder for his dedicated presence and
instruction throughout this study. I would also
like to especially thank Dr. Isabella A. Abbott who
taught me how to view life in a new way.
(12)
Microalgae on Shell
(13)
LITERATURE CITED
Abbott, I. A. and Hollenberg, G. J. 1976. Marine
Algae of California. Stanford University Press,
California. p. 286, p. 284.
Dixon, P. S. and Richardson, W. W. 1969. The life
histories of Bangia and Porphyra and the photoperiodic
control of spore production. Proc. Int. Seaweed
Symp. 6:133-139.
Drew, K. M. 1949. Conchocelis-phase in the life-history
of Porphyra umbilicalis (L) Kutz. Nature 164:748.
Drew, K. M. 1957. Studies in the Bangiophycidae IV.
The Conchocelis-phase of Bangia fuscopurpurea (Dillw)
Lyngbya in culture. Estratto dalla Pubbl. Staz. Zool.
Napoli 30:358-372.
Eikenberry, A. B. and Wickizer, D. E. 1964. Studies
on the Commensal Limpet Acmea asmi in Relation to its
Host, Tegula funebralis (Mollusca:Gastropoda). The
Veliger 6:supplement,
66-70.
Firestone, A. 1979.
Distribution and abundance of
Tricolia pulloides and Barleeia haliotiphila at Mussel
Point and Point Pinos. Unpublished MS on file at
Hopkins Marine Station Library.
Microalgae on Shell
(14)
Hoek, C. V. D. 1975. Phytogeographic provinces along
the coasts of the northern Atlantic Ocean. Phycologia
14:317-330.
Hollenberg, G. J. 1958. Culture Studies of Marine
Algae. III. Porphyra perforata. Am. Journ. Bot.
15:653-656.
Kurogi, M. 1953. On the Liberation of Monospores from
the filamentous Thallus (Conchocelis-stage) of Porphyra
tenera Kjellm. Bull. Tohoku Reg. Fisheries Resrch Lab
2:104-108.
Nichols, H. W. and Lissant, E. K. 1967. Developmental
Studies of Erythrocladia Rosenvinge in Culture.
J. Phycol. 3:6-18.
Provasoli, L., McLaughlin, J. J. A., and Droop, M. R.
1957. The development of artificial media for marine
algae. Arch. Mikrobiol. 25:392-428.
Tseng, C. K. and Chang, T. J. 1954. Studies on Porphyra
1. Life History of Porphyra tenera Kjellm. Acta Botanica
Sinica 3:287-302.
Tseng, C. K. and Chang, T. J. 1955. A Revision of the
Life Cycle Diagram of Porphyra tenera Kjellm. Acta Botanica
Sinica 4:265-268.
0
Microalgae on Shell
(15)
Tseng, C. K. and Chang, T. J. 1956. Conditions of
Porphyra Conchospore Formation and Discharge and the
Discharge Rythm. Acta Botanica Sinica 5:33-48.
Wilkinson, M. and Burrows, E. M. 1972. An experimental
taxonomic study of the algae confused under the name
Gomontia polyrhiza. J. Mar. Biol. Ass. U. K. 52:49-57.
Yarish, C. 1976. Polymorphism of selected marine
Chaetophorceae (Chlorophyta). Br. Phycol. J. 11:29-38.
Microalgae on Shell
(16)
TABLE CAPTIONS
Table 1 --
Tidal heights and immediate macroalgae of
high, medium, and low level collection sites.
Table 2 -- The microalgae found on Tricolia shells as
observed in the field, in culture, and as
new growth on sterilized shells.
Table 3 -- A comparision of characteristics between the
common Chaetophoraceae alga seen on Tricolia
shells and local Chaetophoraceae genera.
Table 4 -- A comparision of characteristics between the
common Chaetophoraceae alga seen on Tricolia
shells and Pseudopringsheimia apiculata.
The differences in characteristics may be
due to the difference in hosts.
Microalgae on Shell
(17)
FIGURE C
PION.
Figure 1 -- Numbers of particular microalgae in cultures
from the wave exposed coast study areas
(Point Pinos and Point Joe) and from the
wave protected coast study areas (Mussel Point).
Figure 2 -- Numbers of particular microalgae as related
to the culture temperature.
Microalgae on Shell
(18)
OF PIATES
EXPLANATION
Plates 1-3 -- Three distinct forms of Conchocelis ob¬
served in Tricolia pulloides shells.
Rule is 12um.
Plate 4 -- Erythrocladia subintegra, top view.
Rule is 169um.
Plate 5 --
Erythrocladia subintegra, cross-section showing
polystromatic central region. Rule is 44um.
Plate 6 --
Lyngbya sp. Rule is llum.
Plate 7 - Apiculate tips of Pseudopringsheimia apiculata.
Rule is 5um.
Plate 8 -- Free, irregularly branched filaments from a
monostromatic region of Pseudopringsheimia
apiculata. Rule is 52um.
Plate 9 -- The discoid-cushion thallus of Pseudopringsheimia
apiculata showing monostromatic growth at the
margins and polystromatic growth in the center.
Rule is 52um.
Microalgae on Shell
COLLECTION SITE
(approx.)TIDAL HIEGHT
IMMEDIATE
MACROALCA
TABLE 1
Medium
High
+2 ft.
11 ft.
Gigartina
Rhodoglossum
papillata
aff
LOW
+0 ft.
Gastroclonium
coulte
—
(19)
Microalgae on Shell
TABLE 2
SPECIES
Acrochaetium arcuatum ........
Conchocelis rosea ............
Interomorpha sp
Trythrocladia subintegra .....
Lrythrotrichia carnea ........
Teldmannia chitonicola .......
Pseudopringsheimia apiculata.
Ulva sp
Dermocarpa sp.
Lyngbya sp..
Coccoid blue-green ...........
PLACE OF OBSERVATION
AS NEW
IN
FIELD CULTUR
GROWTH
+
+
(20)
CHARACTERISTIC
GROWTH TYPES
DESCRIBED
SHAPE OF THALL
MONOSTROMATIC
AND POLYSTRO¬
MATIC GROWTH
HABIT OF MONO¬
STROMATIC
REGION
CELLS IN VER¬
TICAL ROWS IN
POLYSTROMATIC
REGIONS
TERMINAL CELLS
OF VERTICAL
ROWS ARE
APICULATE
Microalgae on Shell
TOCLADIA
Epiphytic
Endophytic.
Epizoic
Not primarily
discoid
Monostromatic
Cells round in
center. Cells
form free, ir-
regularly
branched, rad¬
iating fila-
ments at mar-
gins.
(Table 3)
SEUDULVELLA
Epiphytic
Epizoic
Discoid
Polystromati
in central
portion.
Monostromatic
at margins.
Cells may be
round in cen
ter. Cells
may form
free fila¬
ments at mar¬
gins, may al
so form lat¬
erally ad¬
joined fila-
ments at mar-
gins.
YES
NO
ULVELLA
Epiphytic
Endophytic
Discoid
Usually mono-
stromatic
Cells may be
round in cen¬
ter. Cells
do not form
free fila¬
ments at mar-
gins. Cells
do form lat¬
erally ad¬
joined fila-
ments at mar¬
gins.
(21)
PSEIIDO¬
PRINGSHEIMLA
Epiphytic
Discoid¬
cushion
Polystromatic
in central
portion.
Monostromatic
at margins.
Cells round ir
center. Cells
do not form
free filaments
at margins.
Cells do form
laterally ad¬
joined fila-
ments at mar¬
gins.
YES
YES (for
one local
species:
P. apiculata
COMMON
SHELL ALGA
Epizoic
Endozoic
Discoid¬
cushion
Polystromatic
in central
portion.
Monostromatic
at margins.
Cells round in
center. Cells
form free, ir
regularly
branched, rad
iating fila-
ments at mar¬
gins. Cells
may also form
laterally ad¬
joined fila-
ments at mar¬
gins(?).
YES
YES
Microalgae on Shell
CHARACTERISTIC
VERTICAL ROWS OF
CELLS IN CROSS
SECTION
TERMINAL CELLS OF
VERTICAL ROWS ARE
APICULATE
HEIGHT OF CROSS¬
SECTION
CELLS OF VERTICAL
ROWS ARE VERTICALLY
ELONGATED
HABIT OF MONOSTRO¬
MATIC REGIONS (Top
view)
**HOST**
PSEUDOPRINGSHETMIA
APICULATA
YES
YES
9-12 cells
145-165 um
YES, cells 0.5-2.5
times as long as
wide. (8-12um in
width)
Present, but not
described.
Egregia menziesii
and Dictyoneurum
californicum
(both are macro¬
brown-algae)
(Table 4)
(22)
ALGA ON SHELL
YES
YES
10 cells
67 um
NO,cells are
horizontally
longated, 2 times
as wide as long.
(2.2xh.5um)
Circular cells
in crowded region
(2.7-3.4 um in diam.)
Radiating, irregular-
ly branched free
filaments at margins.
Cells elongated up
to 5.1 times as long
as width.
(11.2x2.2um)
Shell of the inter¬
tidal snail
Tricolia pulloides
Microalgae on Shell
6000
5000
4000
3000

2000
1000



OL
200

150
100

50


Pacific
Ocean
Pt. Joe
Pt. Pinos
(23)
(Figure 1)

Enteromorpha sp.
& Ulva sp.

Feldmannia
chitonicola



rythrocladia
subintegra

Erythrotrichia
carnea


Monterey
Bay
Mussel Pt.
J
Microalgae on Shell
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