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Abstract
of Ph. D.
Thesis in Marine Invertebrates.
Presented by Dr. Fayez A. M. Shoukr, Zoology Department,
Faculty of Science,
Cnidarians of the Egyptian marine waters have received very little
attention, although they are found in vast numbers of individuals and species.
They are of great Interest from scientific, medical and economical points of
view. The venomous sea anemone Anemonia sulcata (Pennant,
1777),
which prevails the sea coasts of
It was
aimed by the present work to :
-
Investigate the Egyptian hydroid fauna from a
taxonomical point of view and present an identification key for these animals.
-
Describe the morphological variations of both
the Gymnoblastic and the Calyptoblastic hydroids and to draw a diagram for all
the reported species.
-
Determine the biology of the most abundant
hydroid species all the year round at the Eastern Harbor of Alexandria. These
biological aspects include the seasonal variations for growth rates and sexual
maturity, regeneration, autotomy and summer regression.
-
Study of the histological structure for some
hydroid species.
-
Throw some light on the local geographical
distribution and ecological interrelationships between hydroids and other
fouling organisms.
-
Collect the scattered literature on these
interesting animals for stimulation of further detailed studies.
A sampling scheme was designed to collect marine
hydroids and associated organisms from seven stations. These collecting
stations located at the Eastern Harbor of
These marine hydroids were narcotized by the
common narcotics such as magnesium sulphate,
magnesium chloride, chloral hydrate, menthol and ether. They were fixed in 5
percent formalin in sea-water, boiling concentrated formalin, sea water Bouin's fluid and Helly's fluid (Zenker-formal). The fixed hydroids were stained as a whole
(to investigate their morphology) by the following stains Gower's carmine, Grenacher's borax carmine, Grenacher's
alum carmine, Mayer's haemalum and iron alum-Ehrlich'e haematoxylin. Moreover,
light and fast green were employed as counter stains to demonstrate the chitinous perisarc. Gower's
carmine and alcoholic fast green gave excellent results for staining whole
mounts of hydroids. The histological sections of hydroids were prepared by the
usual ways and stained with a variety of staining methods Including Heidenhain's Mallory Azan, Orth's
lithium carmine, Milligan trichrome and Mayer's haemalum. The first method proved to be excellent for
staining hydroids tissues.
The
results of this study may be summarized in the following :
(A) Taxonomy and distribution:
A taxonomic list of
thirteen species of our marine hydroids were reported among fouling
organisms. Six of these species were firstly recorded for the Egyptian fauna.
Among the identified species, six species belong to the Gymnoblastic hydroids,
namely, Tubularia crocea
(Agassiz,1862), Halocordyle pennaria (Linnaeus,1758), Eudendrium
carneum (Clarke,1882), Eudendrium rameum (Pallas,1766),
Corydendrim parasiticum (Linnaeus,1767)
and Dicoryne conferta
(Alder,1856).The Calyptoblastic hydroids consist of seven
species: Orthopyxis lennoxensis
(Jaderholm,1903), Clytia foxi
(Billard,1926), Clytia aegpyptica (Shoukr,1982), Obelia dichotoma ( Linnaeus,1758 ) ,
Obelia geniculata (
Linnaeus,1758 ), Aglaophenia pluma
( Linnaeus,1767 ) and Plumularia
setacea (Ellis,1755). The following
key will help to identify these Gymnoblastic and Calyptoblastic hydroids.
Identification key to the Egyptian marine hydroids
species.
1. Athecate (naked) hydroids in which, hydranths and
reproductive polyps without
hydrothecae and gonothecae
...
Gymnoblastic hydroids
1.1. Hydranths
with filiform tentacles only.
1.1.1. Tentacles arranged in two basal and distal whorls
..
.
.
.Tubularia
crocea.
Tubularia crocea (
Colony simple with false ramification up to 12 cm. high, perisarc on the hydrocaulus
slightly annulated at its origin from the stolen and at irregular intervals.
Coenosarc form a collar under the hydranth base. Aboral tentacles more numerous than oral ones, their
numbers reached to 28 and 22 respectively. Gonophores growing
in long unbranched racemes reaching in number to 16. Female gonophores
characterized by four to eight apical processes or tentacles, they were
laterally compressed and surrounding the spadix. The male gonophores lacking the laterally compressed ridges or
tentacles.
Local Distribution: The Eastern Harbor of
Alexandria (
1.1.2. Tentacles arranged in a single basal
whorl.
1.1.2.1. Hypostome differentiated from the hydranth body with
trumpet-shape.
1.1.2.1.1. Colony large, tree-shaped, branching in
all planes without
twisting
.
..
..Eudendrium carneum
Eudendrium carneum (Clarke,1882)
This
hydroid occurred in a considerable abundance with well developed and
rigid perisarc reaching in height to 21 cm. Tentacles
ranged in their number from sixteen to twenty-eight. Sexes are separate with
male and female colonies. The male gonophores radiating in whorls while female gonophores
in clusters. The gonophores concentrated at the upper region of the colonies.
Local Distribution
:Port-Fouad, Port-Said,
1.1.2.1.2. Colony small
with twisted long branches
..
..
.
Eudendrium rameum.
Eudendrium rameum (Pallas,1766)
This
species reported with well developed and thick perisarc
reaching in height to 2.5 cm. Hydranths with variable number of tentacles from
12 to 24. The gonophores arise at the basal region of colonies.
Local
Distribution: The Eastern Harbor of Alexandria (
1.1.2.2. Hypostome not
differentiated from the hydranth body with
conical-shape
..
Dicoryne conferta
Dicoryne conferta
(Alder,1856)
Colonies consisting of much branched, and
irregularly alternating fascicled stems up to 5 cm. high. Hydranths elongated
with tentacles ranged in the number from 8 to 14. Gonophores
pear-shaped, scattered in dense clusters on both sides of the hydranth pedicel
or on blastostyles without hydranths.
Local Distribution: The Eastern Harbor of Alexandria (
1.1.3.Tentacles
scattered without
arrangement
..
..Corydendrium
parasiticum
Corydendrium parasiticum (Linnaeus,1767)
Colonies irregularly branched with bundled hydrocauli reaching to 6 cm. in height. Hydranths very much
elongated with fusiform shape and delicate
attachment. Tentacles number varied from 20 to 38. The sex cells (ova)
developed inside the hydrocauli. The
ultimate ramuli of stems with a cluster of fixed
gonophores on short peduncle.
Local Distribution: Port-Fouad, Port-Said (
1.2. Hydranths with filiform and capitate tentacles
.
.
Halocordyle pennaria
Halocordyle pennaria
(Linnaeus,1758)
Hydroids with
feather-like colonies reaching to large sizes up to 17.5 cm. high.
Hydranths flask-shaped arranged on the upper side only of the lateral branches.
It has an aboral whorl of long filiform tentacles
with a varying number from 8 to 14. Several short capitate
tentacles usually arranged in whorls, the number of these tentacles ranged from
6 to 12. Gonophores developed on the hydranth body just above the aboral tentacles, their number on each hydranth was varied
and reached to 4.
Local
Distribution: Port-Said, Port-Taufiq (
2. Thecate
(covered) hydroids in which hydranths and gonophores protected with
hydrothecae
and gonothecae or similar structures
.
......Calyptoblastic
hydroids
2.1. Hydrothecae free on pedicels, never sessile and never
immersed to the stem or
branches. Diaphragm always
present but nematophores absent.
2.1.1. Mature colonies appeared as single hydrothecal pedicels with broad, large-sized
gonothecae
.Orthopyxis lennoxensis
Orthopyxis lennoxensis (Jaderholm,1903)
This hydroid consisting of unbranched hydrothecal pedicel reached to 2.1 mm. in height. Pedicels with thickened perisarc and wavy
walls throughout. Usually, the pedicel with a distinct
ring just below the hydrotheca. This latter,
contained very thick
wall and toothed margin. The number of marginal teeth and hydranth tentacles
ranged from 8 to 12. Gonothecae were
laterally compressed with shallow corrugated surface and truncate distal end.
Local Distribution: Port-Said (
2.1.2. Mature colonies appeared as branched or
unbranched hydrocauli with many
alternative
hydrothecal,
pedicels and elongated, small-sized gonothecae.
2.1.2.1. Hydrothecae with
sharp toothed margin.
2.1.2.1.1. Hydrothecal surface with vertical lines
.........................................
.Clytia
foxi
Clytia foxi (Billard,1926)
Colonies
small with unbranched hydrocauli reached to 6 mm.
high. The hydrothecal pedicels
alternately arranged from side to side and annulated throughout. Hydrothecae
cone-shaped in which the margin with 12 - 22 tooth. This hydroid nearly
characterized by the longitudinal striations which varied from 2 to 4, on the hydrothecae. Diaphragm is triangular-shaped at the hydrothecal base. The number of hydranth tentacles ranged from 12 to18. Gonothecae arise
from a short annulated pedicel with smooth walls and truncate distal end.
Local Distribution: Port-Taufiq, Port-Said, Port-Fouad
(
2.1.2.1.2.
Hydrothecal surface without vertical lines
..
Clytia aegyptica
Clytia aegpyptica (Shoukr,1982)
The hydrocaulus of
this species is unbranched or with lateral branches, up to 10 mm. high. Small
colonies arise as hydrothecal pedicels, annulated
proximally and distally. The hydrothecal
pedicels annulated throughout for large colonies. Cone-shaped
hydrothecae with 14 - 18 marginal teeth. The hydrothecae lacked any longitudinal striations with thin
and transverse diaphragm. Hydranth tentacles ranged in their number from 12 to
18. Gonothecae on annulated pedicels with large terminal aperture and smooth
walls without corrugation.
Local Distribution: The Eastern Harbor of Alexandria (
2.1.2.2.
Hydrothecae
without toothed margin.
2.1.2.2.1. Bell-shaped hydrothecae,
with unequal length and width, thin perisarc and
transverse
diaphragm
.
.
.
Obelia dichotoma
Obelia dichotoma (
Linnaeus,1758 )
Colonies
consisting of unbranched or branched hydrocauli
reached in height to 45 mm. Hydrothecal pedicels
alternating from side to side, usually annulated throughout and, sometimes at
each end. The tentacle whorl of hydranths consisted of 16 to 28 filiform
tentacles. Gonothecae condensed at the basal region
of colonies. They were elongated with terminal collar and annulated pedicels.
Local Distribution: The Eastern Harbor of
Alexandria (
2.1.2.2.2. Cup-shaped hydrothecae, with nearly equal length and width, thick perisarc and
triangular
diaphragm
.. .. Obelia geniculata
Obelia geniculata (
Linnaeus,1758 )
Colonies
unbranched reaching In height to 4 mm. Hydrocaulus bearing alternate hydrothecal
pedicels on apophyses of the internodes. The perisarc of the internodes and hydrothecal
cup is thick. The number of hydranth tentacles varied from 16 to 22. Gonothecae born
on short annulated pedicels with distinctly thickened perisarc
at the basal region. They were truncate distally with a terminal collar.
Local Distribution: The Eastern Harbor of Alexandria (
2.2. Hydrothecae sessile
and immersed to the stem or branches in one side only.
Nematophores always present but diaphragm absent.
2.2. 1. Hydrothecal margin
toothed
.
.. Aglaophenia
pluma
Aglaophenia pluma
( Linnaeus,1767 )
This
hydroid closely resembles a feather reaching in height to 5.7 cm. Hydrocaulus with regularly alternate hydrocladia
bearing polyps on the upper side only with closely approximated hydrothecae. The margin of each hydrotheca
has nine teeth with a median tooth projecting outwards. The intrathecal
ridge is well marked. Three nematophores associated
with each hydrotheca and each hydrocaulus
internode.
Local Distribution: Port-Said
& Port-Taufiq (
2.2.2. Hydrothecal margin
entire
.
.
.. Plumularia setacea
Plumularia setacea (Ellis,1755)
Hydrocaulus simple with lateral hydrocladia up to 8
mm. high. Stem internode with two nematothecae alternately directed at its distal and basal
ends. Each hydrocladium consist of a short athecate basal internode with
regular sequence of thecate and athecate internodas. The hydrotheca is cup shaped with smooth circular aperture.
Three nematothecae associated with each hydrotheca and one nematotheca
for the athecate internodes.
Local Distribution: Port-Taufiq (
(B) Morphology and biology:
The
morphological characters of the hydroids greatly differed according to seasonal
and ecological variations. At the Eastern Harbor of Alexandria, the hydroid Tubularia crocea
showed several morphological variables including the length of individuals,
width of hydranths (as an indication of growth) and number of oral, aboral tentacles and blastostyles.
The number of the oral and aboral
tentacles varied from 3 to 22 and 7 to 28 respectively. In addition, the blastostyles
number ranged from 4 to 16. These three
variables were significantly correlated with the Individuals length. The
computation of the correlation coefficients and the regression equations for
these variations showed their positively increase with the hydroid growth.
The individuals length pronounced wide range of
variations between 0.3 and 120 mm., while the hydranth
width ranged from 0.12 to 3.3 mm. The
results obtained from the calculations of means, standard deviations and variances
for both individuals length and hydranths width in each
sample all the year round, were statistically analyzed with t-test. These variations revealed a biological
significance as
follows:
* The colonies flourished during the cooler
periods of the year (Autumn, Winter and early Spring)
and regressed during the hot periods in the Summer of 1980 and 1981.
* The peak period of longitudinal growth reported
during April and December while the minimum growth recorded during May and
July.
The mature gonophores developed from September
to April. Consequently, the actinulae larvae produced
by the gonophores and the minute polyps were frequently encountered from
October to April. Therefore, the
breeding period for the hydroid Tubularia crocea was continuous during the cooler periods of the
year at the Eastern Harbor of Alexandria (
In the
life-cycle of this hydroid, the free-swimming medusa stage is reduced to fixed
gonophores. In addition, the sexes are
separate with male and female colonies. The actinulae
larvae liberated from the female gonophores were often settled on the stems and
hydrorhizae of their parents growing directly to the
minute polyps without any metamorphosis.
Thus, false ramification produced for the colonies which usually
mistaken their identification.
The
freshly collected colonies when taken from the sea contained some hydrocauli either missing their hydranths or regenerating
new ones. Thus, the autotomy regeneration phenomenon of Tubularia
crocea may constitute a from
of sexual and asexual reproduction. Furthermore, the width of hydranths was
significantly correlated, with the length of individuals in the normal growth
population. Nevertheless, insignificant correlation between hydranths width and
individuals length was recorded for the population showing regeneration.
The summer regression of Tubularia crocea seems to be normal in the life-cycle of these
hydroids and occurring as a response to ecological changes as rising of the sea
water temperature and presence of predators or as a result of an ecological
succession for another communities.
In spite of the variability of the specific characters in the hydroid Tubularia crocea,
its identification is constant and not led to the construction of other new
species. Therefore, the morphological variables of the hydroids particularly
with growth and maturation are very important and must be taken in
consideration in their taxonomy.
(C) Histology:
The endoderm of the hypostome in Tubularia crocea
and other Gymnoblastic hydroids developed internal longitudinal ridges or villi
to increase the endodermal absorptive surfaces. On
the other hand, Calyptoblastic hydroids
as Obelia dichotoma
lack these villi .In the hydroid Tubularia
crocea, both the oral and aboral
tentacles were solid consisting of endodermal core of
vacuolated cells, ensheathed by an ectodermal layer packed with nematocysts. At the hydranth
base of this hydroid, there is an endodermal cushion
composed of large parenchyma cells to prevent large food particles from passing
into the hydrocaulus. The spermatogenesis and
ovogenesis in addition to development of the actinula
larvae occur inside the gonophores. The stem of this tubularian
hydroid is divided into two peripheral longitudinal canals.
(D) Ecology:
At the Eastern Harbor of Alexandria (
The
confusion in the identification of hydroids and the summer regression of Tubularia crocea
were discussed and showed similarity to other regions of the world.
Moreover, the obtained data were statistically analyzed to confirm the
biological interpretation.
Acknowledgments
I
am indebted to Prof. Dr. M. E. Abdel - Hamid, Late Professor of Invertebrates, Zoology Department,
Faculty of Science,
Selected References
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4: 1-380.
Allman, G.J. (1871): A monograph of the Gymmoblastic or Tubularian
Hydroids.
Ray- Society, Parts I and II,
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development in Tubularia indivisa L.
Ny. Mag. Zool.15: 112 -
117.
Banoub, M.W. (1960): Notes on the fouling of
glass plates submerged in the
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Billard, A. (1926): Zoological Results of the
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Prof. Dr. Fayez A.
M. Shoukr, Zoology Department, Faculty of Science,
