Abstract of Ph. D. Thesis in Marine Invertebrates.

Presented by Dr. Fayez A. M. Shoukr, Zoology Department, Faculty of Science, Tanta University, Tanta 31527, Egypt. Shoukr, F. A. M. (1982): Studies On Some Coelenterates (Cnidarians) Inhabiting Marine Egyptian Waters. Ph. D. Thesis, Faculty of Science, Tanta University, Tanta, Egypt, 225 pp.


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 Alexandria, has a stinging power with erythema and urticaria. In addition, some sessile Coelenterates are regarded as fouling organisms which are attached to ships hulls and affect the world navigation. Moreover, certain hydroids are used for decorative purposes especially in the United States of America and Germany. On the other hand, hydroids are considered the most abundant Cnidarians Inhabiting among fouling assemblages In the Egyptian Harbors and Shipyards. Hence, the present investi­gation deals with their detailed studies which represent a virgin field In our Egyptian region.


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 Alexa­ndria (Mediterranean Sea), Port-Fouad, Port-Said, Ismailia and Port-Taufiq (Suez Canal). Sampling was continuous every month for two years and started from January 1980 till December 1981. The collection of these animals was done randomly from many submerged constructions such as buoys, local ships hulls, pier pilings and rubber cylinders.


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 (Agassiz,1862)

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 (Mediterranean sea), Port-Said, Port-Taufiq (Suez Canal).


1.1.2. Tentacles arranged in a single basal whorl. Hypostome differentiated from the hydranth body with trumpet-shape. 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, Ismailia (Suez Canal). 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 (Mediterranean sea). 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 (Mediterranean sea).

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 (Suez Canal).


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 (Suez Canal).


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 (Suez Canal).

2.1.2. Mature colonies appeared as branched or unbranched hydrocauli with many


alternative hydrothecal, pedicels and elongated, small-sized gonothecae. Hydrothecae with sharp toothed margin. 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 (Suez Canal). 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 (Mediterranean sea). Hydrothecae without toothed margin. 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 (Mediterranean sea). 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 (Mediterranean sea).


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 (Suez Canal).


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 (Suez Canal).


(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 (Mediterranean sea ,Egypt).

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 (Mediterranean sea , Egypt), the hydroids were always associated with other surrounding fouling orga­nisms throughout the year. These organisms were various and including green algae, diatoms, suctorian protozoa, porifera, turbellarian platyhelminthes, nemertine worms, nematodes, bryozoans, polychaetes, pycnogonids, crustaceans and nudibranch molluscs. Some of these associations was for predation, commensalism, parasitism or unpurposal for attachment and protection.


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.




I am indebted to Prof. Dr. M. E. Abdel - Hamid, Late Professor of Invertebrates, Zoology Department, Faculty of Science, Tanta University, Tanta, Egypt, for supervision of this thesis; Prof. Dr. A. F. Ghobashy, Professor of Invertebrates, Zoology Department, Faculty of Science, Suez Canal University, Egypt, for his fruitful help and continuous interest with indirect supervision throughout this study. Special thanks are also extended to Prof. Dr. P.F. S. Cornelius, Prof. Dr. S. J. Moore of British Museum (London) and Prof. Dr. K. W. Petersen of Denmark, for their invaluable help in verification of Identification for several specimens.


Selected References


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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 Cambridge Expedition to


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Billard, A. (1933): Les Hydroides des Golfes de Suez et d'Akaba. Mission


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Brinckmann-Voss, A. (1969): Anthamedusae / Athecatae (Hydrozoa,


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Correspondence To :


Prof. Dr. Fayez A. M. Shoukr, Zoology Department, Faculty of Science, Tanta University, Tanta 31527,Egypt. Shoukr, F. A. M. (1982): Studies On Some Coelenterates (Cnidarians) Inhabiting Marine Egyptian Waters. Ph. D. Thesis, Faculty of Science, Tanta University, Tanta, Egypt, 225 pp.





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