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The typical tunicate looks like a non-chordate animal. If the life history of such animal is studied, the larval form reveals the chordate characters of that animal. In 1816, Lamarck and Cuvier placed these animals in one class ‘Tunicata’. Allis described a compound Ascidian “Botryllus’ in 1756. KowalevskSi. Worked on…
Subphylum Urochordata is divided into three classes. CLASS 1. ASCIDIACEA CLASS 2. THALIACEA CLASS 3. LARVACEA (APPENDICULARIA) CLASS 1. ASCIDIACEA: These are sedentary tunicates. The body is covered by a test. Pharynx is large and contains gill-slits. Notochord, nerve-cord and tail are absent These are Bisexual animals.…
The tunicates were first regarded as sponges. Lamark in 1816 placed Tunicata in between the Radiata and Vermes in his system of classification. Later, they were included in Mollusca. In 1866 Kowalevsky kept them in chordates. Their chordate features are clearly seen in the larval stages. All Urochordates are…
The development of organ system is called as Organogeny. In Amphioxus the gastrula elongates in the future anteroposterior direction and the blastopore comes nearer to the posterior end of the dorsal surface and starts the development of organ system. 1. FORMATION OF NEURAL TUBE INAMPHIOXUS: Neural ectoderm cells of…
FATEMAP OF FERTILISED EGG OF AMPHIOXUS: Conklin in 1932 studied the fate map of Amphioxus. In 1962 Tunguntung described the egg of amphioxus 4 regions are clearly seen. Clear cytoplasm occupying the animal pole will mainly become epiderm& ectoderm. The granular yolky cytoplasm near the vegetal pole will become…
Amphioxus is a Cephalochordate animal. Its Life history in the early stages shows resemblance with ascidians. HATSCHE’K WILSON. CONKLIN’ worked on the part of embryogenesis of Amphioxus. ‘CONKLINS’ work in more accurate and is recent. Amphioxus is a unisexual animal. But sexual dimorphism is absent. Amphioxus shows 26 pairs…
In amphioxus a big space is present, called Atrium it is lined by ectoderm. It encloses pharynx, and part of intestine. It opens out through atriopore at 36 myotome in front of caudal fin. The dorsal wall of the atrium is folded. ln the larva the atrium develops at the…
In the Urochordate and Cephalochordate animals the ventral side of the pharyhx wilI contains endostyle. It is a glandular ciliated groove present on the floor of the pharynx. This contains alternate bands of ciliated and glandular cells. The gland cell secretes mucus. This mucus will concentrate the food particles of…
In chordate animals notochord, dorsal tubular nerve cord and pharyngeal slits are present. In Amphioxus notochord is a cylindrical rod extending the whole length of the body from anterior end to posterior end. it is present below the dorsal nerve cord and above the alimentary canal. The notochord is…
Exoskeleton is absent in Branchiostama. Endoskeleton include the notochord, gelatinous rods and plates, fin-ray boxes etc. 1. Notochord in Amphioxus: The notochord of Amphioxus is extending the whole length of the body along the mid-dorsal line just below the central nervous system. The notochord consists of a single longitudinal…
Amphioxus belongs to Cephalochordate. In 1778 Amphioxus was first discovered and described by Palias. He called it a Molluscan animal. In 1834, it was described as a chordate animal by Costa. He called it ‘Branchistoma’. In 1836, Yarrell gave th name Amphioxus. Amphioxus lives in shallow marine waters and burrows…
The sub-phylum Cephalochordata includes a single class Leptocardii, which has single family, Branchiostomidae. The family contains only two genera Branchiostoma and Asymmetron. The subphylum - Cephalochordata includes Amphioxus or Branchiostoma. Pallas described this animal first. He named it as Umax lancealatus, He included this in Mollusca. In 1834,…
Cephalochordata includes two genera, 1. Asymmetron and 2. Branchiostoma (Amphioxus). Cephalochordates are small fish like animals which show Chordate characters. The notochord extends the entire length of the body. They show a dorsal, tubular neural tube without a definite brain. GENERAL CHARACTERS: Body is fish-like and is useful…
Phylum Chordate is divided into three Sub-Phyla. SUB-PHYLUM: UROCHORDATA SUB-PHYLUM: CEPHALOCHORDATA SUB-PHYLUM: VERTEBRATA The first two sub phyla are called lower chordates or PROTOCHORDATES. They are usually called Acrania group. The vertebrata sub-phylum is called CRANIATA group. 1. SUB-PHYLUM: UROCHORDATA: The urochordate animals belonging to this…
CHORDATES The Phylum Chordate includes bilaterally symmetrical, metamerically segmented, triploblastic, enterocoelomate metazoans exhibiting hights complex organization. This phylum is supposed to be one of the most heterogenous and diversified gruop of animal kingdom. The minute sessile cephalodiscus, work-like Balanoglossus, degenerate tunicates, Amphioxus and the true vertebrates have been included…
The animal kingdom is divided into two sub-kingdoms: Chordata Non-Chordata GENERAL CHARACTRS OF CHORDATES The Chordate characters appear in the developmental stage will persist in the adult or modified in the adult or disappeared in the adult They are, 1. PRESENCE OF NOTOCHORD: It is…
