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SUB!
TIDAL SURVEY OF THE PAGURID POPULATION
Hopkins Marine Station
Robert T. Cook
15/8/6
Introduction
A survey was taken of the pagurid populatien in the
subtidal area in conjunction with the intertidal survey
done by Bob Belknap. I hoped to find the types and numbers
of pagurids found in the subtidal region, and also the
substrates on which the pagurids are found.
Procedure
The procedure followed was that of the intertidal
survey except that all samples were colledted by scooping
up sand with plastic collecting boxes, or by scraping
in the substrate with a diving knife.
Due to the prevalence of a Pagurus species not found
in the intertidal area, a pigmentation chart (See Fig. 1 &
2) was constructed for identifying P. (setosus)" to use
along with John Markhame Pigmentation Chart which I used
for identification of juvenile hermit crabs.
Nine collecting areas were marked out in the subtidal
region. Within each area four substrates were sampled--
open sand, large rocks, crevices found between large rocks,
and small rocks or gravel.
The species name is not known The name in
parenthesis is a closely related species used
as a means of distinguishing the unknown species
of pagurids.
Fid 1.
PIGMENTATION OF POST-LARVAL PAGURUS
(setosus)?
Eyes
Black with distinct tiny yellow dots.
2nd Antennae
Orange-red to dark red longitudinal stripes becoming
solid color near distal end.
1.imm-1/3 distal portion nearly solid red
2.1mm -1/2
Chelipeds
Creme yellow upto 1.5mm. Tending more toward tan
past this size. Dactyl and prodopus tipped white.
Ischium banded with brown or maroon.
Carapace
White, dirty-white, or pink below 1.1mm. Becomes
orange to tan past 1.5mm.
Ambulator
legs
51.1 mm- dark brown banding on dactyl with faint
banding on other segments. Above this size
all bands become dark while proximal side of joint
begins to band with light tan.
Eye stalks

Two longitudinal maroon stripes with a
horizontal stripe at base of the stalk.
+ Size ranges from.7mm to 2.2mm carapace width.
* Carapace width.
12
Data
See Fig. 3.
Results
Three intertidal species of hermit crabs were found
in the subtidal area: Pagurus hemphilli, P. hirsutiusculus,
and P. granosimanus. Two other distinct species of Pagurus
were found in the subtidal, but they have yet to be identified.
Using Schmitt's "Key To California Species of Pagurus,
Pylopagurus, and Parapagurus" the two unknowns fit closely
the characteristics for Pagurus setosus and P. californiensis.
However examination of the species description eliminates
the possibility that these are the correct specific names.
Paguristes turgidus and P. bakeri were found in the
deeper part of the sampled area in the subtidal region.
Pagurid glaucothoe residing in shells were found in all
sampled areas. (Bee Fig. 4.)
Pagurus hemphilli and P. (setosus) constituted over
90% of the sampled pagurid population. The former being
more prevalent nearer the intertidal while the latter
was more numerous in the deeper waters. (See Fig. 5.)
Juvenile pagurids always constituted the majority of
the hermit crabs sampled in each area. (See Fig. 6.)
Although hermit crabs were found just about everywhere
in the subtidal, coralline algae proved to be the substrate
on which the paguries concentrated. (See Fig. 7.)
A

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rt
tat
oe
Distribotion of Pagds
Pagbrs
etgthite
et
Fuggtt
tsate
si o
4
84
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ror
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66170
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Fiq.3.
14
t
20
163
Types of Pagurids Found in Survey
50
Number of samples
1439
Number of pagurids counted
Types of paguride
566 (21 adults):
Pagurus hemphilli
5 (2 adults)
hirsutiusculus
granosimanus
(setosus)**
704
(californiensis)":
3 (1 adult)
Paguristes turgidus
18
Paguristes bakeri
134
Pagurid glaucothoe
Uncertain
1439
Total
* Adulthood was determined by body coloration.
Pagurids which were large and no longer had
complete juvenile coloration were considered
adults.
** Species not known. A closely related species
is given.
4
Fg
C
400

ferentage fagorid Compesition of Areds

PE
Ttet

Tdt




F15
Fig.G.
12

21
10
201
60
443
H0
12
E
Hovee
Ot
C
Pee
A
FE
aTh
114
13

E
9.7.
ious Substrates
Pagurid Concentration on Var
No. of No. of
Pagurids
Samples Pagurids per sq. ft.
16
1.5
Open sand
140
13
11
Crevices
Small rocks
Large rocks
10
80
A. Mixed algae
1154
144
B. Corallines
—
1439
Total
Discussion
Pagurus hemphilli, which was found by Belknap to
be prevalent in the lower intertidal area, was also very
prevalent throughout the subtidal area. P. hirsutiusculus,
which was numerous throughout the whole intertidal area,
was not found to any great extent in any part of the
subtidal area. This could be indicative of a sudden drop
in population at the intertidal zone or of poor sampling
in one of the surveys.
P. (setosus), which I found throughout the subtidal
area, was not found in the intertidal area by Belknap,
perhaps because it was not recognized (it resembles P.
hirsutiusculus).
Summary
1. Pagurus hemphilli, P. hirsutiusculus, P. granosimanus,
P. (setosus). and P. (californiensis) were found inhabiting
the subtidal region.
2. Paguristes bakeri and P. turgidus were found in
the subtidal region.
3. Large numbers of pagurid glaucothoe were found residing
in shells.
4. Coralline algae is the substrate having the highest
population density of pagurids.
C
References
he Marine Decapod Crustacea of California
Schmitt, Waldo L.
University of California Publications in Zoology, Vol. 23,
May 1921.