Minor phyla
Ctenophora
The ctenophore are biradially symmetrical organisms, lacking nematocysts, possessing ciliary plates in eight rows and possessing a gelatinous ectomesoderm containing mesenchymal muscle fibres.
Hermiphora plumosa
Systematic position
Phylum Ctenophora
Class Tentaculata - with two long aboral tentacles
Order Cydippikda - body oral or rounded, tentacles branched and retractile into
pouch
Genus Hermiphora
Species plumosa
position in animal kingdom - Ctenophores have certain characteristics in common with coelenterates. They are believed to have diverged very early from ancestral medusoid coelenterates which was a spherical animal with concentration of cilia along 8 meridional rows which later developed into comb plates, so known as comb jellies. However they represent a blind offshoot which gave rise to no higher forms. Ctenophores also present certain advancements over Radiata such as prominence of apical region, musculature derived from mesoderm, presence of gonoducts and determinate type of cleavage. This implies that Ctenophora are intermediate between Radiata and Bilataeria and have undergone considerable specialization with many striking characteristics of their own. Therefore, it seems quite logical to treat that Ctenophores should be included into a separate phylum rather than a class or subphylum of phylum of Coelenterata.
Hermiphora plumosa is slightly smaller and pear shaped organism about 5 to 20 mm in diameter. It is of glassy transparency. The species H plumosa is found in the Mediterranian sea .
External surface bears 8 equally spaced paddle plates or comb plates each made up of transverse rows of long cilia. So, they are also known as comb jellies. Near aboral end, on opposite sides, are attached two very long ( 15 cm) solid and highly extensible tentacles provided with lateral branches. Each tentacle can be completely withdrawn into a deep cavity or tentacle sheath or pouch. At the aboral end is a shallow depression with a sense organ or statocyst. A slit like mouth is present at the oral end. It leads into a long narrow pharynx or stomodaeum opening into the stomach. The stomach is connected to a system of gastrovascular canal. Hermiphora is strictly carnivore. Food is captured by tentacles with the help of colloblast. Colloblasts are adhesive cells also known as lasso cells. Undigested materials come out of mouth. The digestion is both extracellular and intracellular.
The body is covered externally by a delicate ectodermal epithelium. The epithelium of the stomodaeum is found by development to be ectodermal. The interval between the external epidermis and the canal system is filled by a soft, jelly like mesogloea. The tentacle sheath is is an invagination of the ectoderm and the tentacle itself is covered by a layer of ectoderm with which a is a core or axis formed by a strong bundle of longitudinal muscular fibres which are of mesodermal origin which serve to retract the tentacle into tits sheath.
The feeble development of the muscular system of course correlated with the fact that the swimming plates are the main organs of progression. A further striking difference between our present type and the Cnidaria is the absence of stinging capsules (nematocysts). This causes Ctenophora to be referred to as Acnidaria in older system. The place of stinging capsules is taken in a sense by the peculiar adhesive cell with branches of tentacles are covered. Adhesive cell has a convex surface produced into a small papillae which readily adheres to any object with which it comes in contact and is with difficulty separated.
The Hermiphora is hermaphrodite. Gonads develop in the meridional gastrovascular canal. Each of which has and ovary extending along the whole length of one side and testis along the whole length of opposite side. When ripe the ova and sperms are discharged into the canals, make their way to the infundibulum then into stomodaeum an finally escape by the mouth. Fertilization takes place in sea water.
Life cycle
The egg consists of and outer layer or protoplasm containing nucleus and of an internal mass of a frothy or vacuolated nature. The vacuoles contain homogenous substance which serve as a nutrient store to the growing embryo which corresponds with the yolk which occurs in a large proportion of animal eggs. Enclosing the egg is a thin vitelline membrane separated from the protoplasm by a considerable space filled with a clear jelly. Development includes a free swimming cydippid larva.
Ctenophora
The ctenophore are biradially symmetrical organisms, lacking nematocysts, possessing ciliary plates in eight rows and possessing a gelatinous ectomesoderm containing mesenchymal muscle fibres.
Hermiphora plumosa
Systematic position
Phylum Ctenophora
Class Tentaculata - with two long aboral tentacles
Order Cydippikda - body oral or rounded, tentacles branched and retractile into
pouch
Genus Hermiphora
Species plumosa
position in animal kingdom - Ctenophores have certain characteristics in common with coelenterates. They are believed to have diverged very early from ancestral medusoid coelenterates which was a spherical animal with concentration of cilia along 8 meridional rows which later developed into comb plates, so known as comb jellies. However they represent a blind offshoot which gave rise to no higher forms. Ctenophores also present certain advancements over Radiata such as prominence of apical region, musculature derived from mesoderm, presence of gonoducts and determinate type of cleavage. This implies that Ctenophora are intermediate between Radiata and Bilataeria and have undergone considerable specialization with many striking characteristics of their own. Therefore, it seems quite logical to treat that Ctenophores should be included into a separate phylum rather than a class or subphylum of phylum of Coelenterata.
Hermiphora plumosa is slightly smaller and pear shaped organism about 5 to 20 mm in diameter. It is of glassy transparency. The species H plumosa is found in the Mediterranian sea .
External surface bears 8 equally spaced paddle plates or comb plates each made up of transverse rows of long cilia. So, they are also known as comb jellies. Near aboral end, on opposite sides, are attached two very long ( 15 cm) solid and highly extensible tentacles provided with lateral branches. Each tentacle can be completely withdrawn into a deep cavity or tentacle sheath or pouch. At the aboral end is a shallow depression with a sense organ or statocyst. A slit like mouth is present at the oral end. It leads into a long narrow pharynx or stomodaeum opening into the stomach. The stomach is connected to a system of gastrovascular canal. Hermiphora is strictly carnivore. Food is captured by tentacles with the help of colloblast. Colloblasts are adhesive cells also known as lasso cells. Undigested materials come out of mouth. The digestion is both extracellular and intracellular.
The body is covered externally by a delicate ectodermal epithelium. The epithelium of the stomodaeum is found by development to be ectodermal. The interval between the external epidermis and the canal system is filled by a soft, jelly like mesogloea. The tentacle sheath is is an invagination of the ectoderm and the tentacle itself is covered by a layer of ectoderm with which a is a core or axis formed by a strong bundle of longitudinal muscular fibres which are of mesodermal origin which serve to retract the tentacle into tits sheath.
The feeble development of the muscular system of course correlated with the fact that the swimming plates are the main organs of progression. A further striking difference between our present type and the Cnidaria is the absence of stinging capsules (nematocysts). This causes Ctenophora to be referred to as Acnidaria in older system. The place of stinging capsules is taken in a sense by the peculiar adhesive cell with branches of tentacles are covered. Adhesive cell has a convex surface produced into a small papillae which readily adheres to any object with which it comes in contact and is with difficulty separated.
The Hermiphora is hermaphrodite. Gonads develop in the meridional gastrovascular canal. Each of which has and ovary extending along the whole length of one side and testis along the whole length of opposite side. When ripe the ova and sperms are discharged into the canals, make their way to the infundibulum then into stomodaeum an finally escape by the mouth. Fertilization takes place in sea water.
Life cycle
The egg consists of and outer layer or protoplasm containing nucleus and of an internal mass of a frothy or vacuolated nature. The vacuoles contain homogenous substance which serve as a nutrient store to the growing embryo which corresponds with the yolk which occurs in a large proportion of animal eggs. Enclosing the egg is a thin vitelline membrane separated from the protoplasm by a considerable space filled with a clear jelly. Development includes a free swimming cydippid larva.
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