A comparison of certain holothurians of the Caribbean and Pacific waters

51 Pages·02.362 MB·English

by  Schafer, Rita Dorothy

A COMPARISON OF CERTAIN HOLOTHURIANS OF THE
CARIBBEAN AND PACIFIC WATERS
A Thesis
Presented to
the Faculty of the Department of Zoology
The University of Southern California
In Partial Fulfillment
of the Requirements for the Degree
Master of Arts
by
Rita Dorothy achafer
August 1951
UMI Number: EP67205
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thesis, written by
&i t a._ Do rot hy___ Sc haf e r
under the guidance of hBXt...Faculty Committee,
and approved by all its members, has been
presented to and accepted by the Council on
Graduate Study and Research in partial fulfill­
ment of the requirements for the degree of
Master..of. Arts.....................
Faculty Committee
Chairman
£,.2).
INTRODUCTION
The relationship of the invertebrates of the Carib­
bean and of the Panamic region of the Pacific is of great
interest to investigators because of the connection between
the oceans during past geologic agesv Some work has been
done to attempt to clarify the relationship of faunas of
holothurians of these areas.
Some of the earliest work on the holothurian fauna
of the West Indian region was done by Leseuer in 1823. His
determinations and descriptions of species taken near St.
Bartholomew Island helped to form the basis of work to
follow.
Verrill in 186? laid much of the foundation for
future studies or distribution by his comparative study of
the holothurians of the Caribbean and Panamic areas, and
discussion of possible means of transmission of forms from
the one area to the other. In 186?, Selenka*s work on the
holothurians of the world increased the list of species of
the Caribbean, it likewise represented one of the earliest
attempts to systematize and classify the then known'holo­
thurians of the world.
In 188§, Th^el1s report of the Challenger expedition
added further to the species known from the Caribbean. Ives
(1890) made a study of the echinoderm faunas of the north­
ern coast of Yucatan and the harbor of vera Cruz, describ-
2
ins two new species,
Clark (1901b) described 4a new species from the Porto
Bican areai In 1919 in a paper dealing with the distribu­
tion of the echinoderms of the west Indies, he listed the
known genera and species* giving their type localities and
distribution.
Edwards (1908) attempted to clear up much of the con­
fusion which already existed concerning similar forms found
in the western Atlantic and Pacific regions by detailed
studies of certain species, emphasizing aspects of their
external and Internal structure ard especially their dermal
spicules♦
In 1930 Deichmanns paper describing and discussing
tbs holothurians of the western Atlantic appeared. This
work, because of its thoroughness, has proved to be one of
the most valuable discussions of the holothurian fauna of
that region.
Fanning* s work (1928-1933) on the holothurians of
the world is an extensive study giving brief descriptions
compiled from various authors, usually accompanied by spi­
cule illustrations.
The purpose of this study is to clarify, in so far
as possible, the relationship of the species of the genus
holothuria of the Caribbean waters and the Pacific. This
3
detailed analysis has been necessary in order to complete
a taxonomic study of certain species in both areas* The
extensiveness of the Allan Hancock Foundation collection
make it one of the most adequate for such a study.
The writer is deeply Indebted to Dr. Irene McCulloch
under whose direction this study was completed and whose
advice and helpfulness were invaluable; to Dr. Walter S.
Martin and Dr. John L . Mohr1 whose many kindnesses through-
out the course of this study are deeply appreciated; to
Captain Allan nancock, Director of the Allan Hancock Foun­
dation, for use of the space and materials.
MATERIALS and techniques
The specimens used in this study were collected over
a period of more than fifteen years, assembled as a part of
the allan Hancock Foundation collection* and represent both
the Atlantic and Pacific species of Holothuria. Immedi­
ately- after collection, specimens were narcotized in satu­
rated magnesium sulfate solution and then placed in 70^
alcohol.
in the determination and identification of species
both the external characteristics and the calcareous struc­
tures of the body wall were used; uareful examination of
these calcareous structures was the chief and most satis­
factory means employed. For the study of the spicules,
slides were made of sections of the body wall in the follow-.
ing manner. A small section, approximately 1/16 inch square*
was removed. This section of tissue was then placed on a
clean glass slide and covered with a drop or two of 20fo NaOH
solution# Over this was placed a gf 0 round coverslip. The
slide was then held over a low flame of a Bunsen burner or
alcohol lamp and heated until the tissue was seen to begin t
to disintegrate. Extreme care was necessary to avoid over­
heating which would result in destruction of both tissue
and spicules. After the tissue had begun to disintegrate,
the slide was removed from the heat and carefully washed
with clear water, strips of absorbent paper were held
across the end of the slide and adjacent to the covers lip.
water was then gently dropped at the angle formed by the
strip and the edge of the coverslip, permitting it to flow
under the coverslip, flood the area around the section of
tissue and then be reabsorbed by the absorbent paper, an
average of five or six operations wase required to^complete­
ly wash away the HaOH.
Drying was accomplished by dropping absolute alcohol
around the edge of the coverslip in the manner de scribed
above for washing. Following this, evaporation took place
rapidly, permitting the coverslip to be easily removed from
the slide without mutilating the spicules•
Permanent mounting was done after removal of the
coverslip by placing a drop or two of euparal on top of the
section. The coverslip was then carefully replaced, the
slide labelled, and put aside to dry.
DeterminatIons were made by studying the spicules
under both low and high magnification, comparing them as to
size, shape, and surface contour. Externally, the specimens
were compared as to body length, width, color, number of
tentacles and distribution of pedicels and papillae.
6
_2>iviurn
dorsal mesentery _ _
tentacle____
i 1
rmncg canal I j
• anal tooth.
Polian vesicle
i Cuvierian organ
tube foot___________* |
i respiratory tree
trrvitim------------
H olctkari&n, view
^nterradial piece
720
^ pteci
B utton Calcareous ring
Basal disk
spare__j
>S=*
Rosette
Supporting roA
Ro<2
Wheel
Calcareous deposits
Ambulacra! f o ot......Tub© f oot
Anchor................Calcareous deposit found in some spe­
cies 9 typically anchor-shaped.
Anal tooth,........ .One of several calcareous tooth-like
deposits grouped around anus.
Bivium.............. .two of the five ambulacra, in holo- ;
i
thurians, dorsally placed. j
Button ....... Perforated plate, oval or elliptical
with perforations regularly arranged
in pairs. Entire structure may be
i
smooth, knobbed, or spiny.
Calcareous ring......calcareous deposit of plates in the
body wall, forming a ring surrounding
the esophagus. 1
Cuvierian organ......Modified basal branches of respiratory
trees, containing cells which upon the
addition of sea water secrete a slime,
then visceral organs are ejected, these
organs are first to be cast out, form- i
ing a tangle of white threads.
Bisk. ..... .Perforated plate forming the base of
»
the table. 1
Dorsal mesentery.....Thin membrane, attached to the body
wall at the mid-dorsal line, holding