|
Date & Time : 25, April 2024 13:12
General Characteristics of Urochordata
Classification of Urochordata
A Few Examples
1.Herdmania
Geographical distribution: India, Pacific and the Atlantic oceans and from Malaya and West Indies
Habitat: solitary marine form
Food: microscopic plants and animals i.e. diatoms, algae and infusorians
Characteristic Features:
1. Body: roughly oblong in outline
2. Body Length: 9.5 to 12 cm long
3. Body Colour: pink
4. Attachment of animal is at posterior ventral end by foot
5. Body free end is provided with two external openings of the branchial and the atrial apertures
6. Opening of mouth through branchial aperture or siphon,while anus by atrial aperture
7. Sac-like pharynx perforated by numerous stigmata
8. U-shaped alimentary canal
9. Respiration through branchial – sac. Test also act as an accessory respiratory organ
10. Open – type blood vascular system
11. Excretory organ is neural gland present above the nerve ganglion
12. Hermaphrodite
2. Doliolum
Geographical distribution: Tropical and sub-subtropical waters
Habitat: free- swimming,pelagic form inhabiting the warm water
Characteristic Features:
1. Body: barrel-shaped with the mouth and at opposite end lies anus
2. Test or tunic : thin,transparent and has no cells
3. Open ends of barrel are fringed with lobes
4. In volumnous pharynx oral funnel opens broadly
5. Pharynx: perforated by dorsal and rows of stigmata present ventrally
6. In the pharynx Endistyle and peripharyngeal ciliated bands are present
7. Absence of dorsal lamina and tentacles
8. Stomach small and intestine short and anus open posteriorly
9. Hermaphrodite
10. Near the anterior end dorsal ganglion and subneural glands are situated
11. Life cycle show an alteration of sexually mature adult , the gonozoid with the asexually reproducing phase,the oozoid
3. Salpa
Geographical distribution: Tropical seas
Habitat: free swimming,solitary pelagic forms
Characteristic Features:
1. Body: barrel-shaped with the mouth and atrial aperture present at opposite end
2. transparent test
3. Presence of Endostyle and pharyngeal bands
4. Dorsal lamina present and is known as gill
5. On dorsal surface a single tentacle is present
6. Digestive system and heart is present in a spot called nucleus
7. Eye is present near near the nerve ganglion
8. In front of the pharynx dorsal tubercle is present
9. Presence of subneural gland ventral to the ganglion
10. Salpa is found in 2 forms:
a) Asexual phase or oozoid
b) Sexual phase or blastozooid
3. Ciona
Geographical distribution: Western region
Habitat: solitary marine form attached to rocks
Characteristic Features:
1. Body: cylindrical ,tubular ,transparent and longer than broad
2. Body Length: 3.5-5inches
3. Body covered with thin transparent test or mantle
4. Opening of mouth is in branchial siphon and anus into atrial-siphon
5. Branchial aperture is 8-lobed while atrial aperture is 6-lobed
6. Longitudinal folds absent in pharynx
7. U – shaped alimentary canal consist of pharynx, oesophagus, stomach and intestine
8. Rectangular stigmata
9. Horse-shoe shaped dorsal tubercle
10. Hermaphrodite and protogynous
|
