Second Lecture
CLASSIFICATION OF
PROTOCHORDATA
General Characters of Protochordata (Acranita):
➢Proto means first or lower or primitive chordates.
➢ Cranium, vertebral column, appendages, cephalization
and exoskeleton are absent.
➢ They are exclusively marine.
➢ Persistant of notochord.
➢ Kidney’s are protonephric.
➢ Sexes are separate or united.
➢ Reproduction is sexual and asexual.
➢ Gonoduct mostly absent.
➢ Development is indirect.
➢ Free swimming larva.
Phylum: Chordata
Group: Acraniata (Protochordata)
Sub-phylum:
Hemichordata Cephalochordata Urochordata
Class Eg. Amhioxus
Enteropneusta Pterobranchia
Eg.: Balanoglosus Eg.: Cephodiscus
Saccoglosus Rhabdopleura Class
Ascidiacea Larvacea Thaliacea
Eg.: Ascidia Eg.: Oikopleura Eg.: Salpa
Hermania Appendicularia Doliolum
Botryllus Fritallaria
Sub-phylum-1: Hemichordata
➢ Hemi: Trunk (Half)
➢ Notochord is doubtful and short.
➢ known as stomochord.
➢ Body is divided into proboscis, collar and
trunk.
Class: (A) Enteropneusta
Class: (B) Protobranchia
Class: (A) Enteropneusta
(Enteron means Gut and pneusta breadhing)
➢ Tongue worm, proboscis, collar and trunk.
➢ Numerous gill slits and gonads.
➢ Alimentary canal straight.
➢ Example: Balanoglosus, Saccoglosus,
Ptychodera.
Balanoglosus
Class: (B) Pretobranchia
(Gr. Pteron, feather + branchion, gill)
➢ Sedentary, solitary and colonial marine form.
➢ Proboscis bears ciliated tentacles to produce ciliary
feeding current of water.
➢ Collar bears two or more tentaclated arms.
➢ One pair of gills or none.
➢ U-shaped alimentary canal.
➢ Few gonads.
➢ Reproduction by budding.
Order:- (1) Cephalodiscida
Order:- (2) Rhabdopleurida
Order- 1:- Cephalodiscida
➢Solitary or several individuals unconnected in a
common gelatinous house.
➢Collar with several tentaculated arms.
➢Single pair of gills and gonads.
Example: Cephalodiscus,.
• Cephalodiscus
Order:- (2) Rhabdopleurida
• Collonial
• Collar with two tentaculated arms
• Gills are absent
• Single gonads
Example: Rhabdopleura
Rhabdopleura
Sub Phylum-2 : Cephalochordata
(G.kephale, head + L.chorda, cord).
• Notochord well developed, extending entire
length of body.
• Presence of endostyle (a ciliated groove in the
floor of pharynx, used for getting food).
• Not well defined head.
e. g. Amphioxus
Sub-phylum: 3: Urochordata
➢ Exclusively marine known as sea squirts.
➢ Solitary or colonial.
➢ Fixed or free swimming and pelagic.
➢ Body is covered by Tunic or Test.
➢ Notochord present in larval stage and absent from
adults.
➢ Nerve cord in larva which degenerates in the form
of small ganglion in adults.
➢ Numerous gill slits.
➢ Sexes are united i.e. Hemophrodite.
Class: (A): Ascidiacca
➢ Test permanent and well developed.
➢ Reproduction sexual or asexual.
➢ Fixed or free swimming marine forms.
➢ Simple or compound, solitary or colonial.
➢ Retrogressive metamorphosis.
Order 1. Enterogona
➢ Body sometimes divided into thorax and
abdomen.
➢Single gonad lying in or behind intestinal loop.
➢Larva with ocelli (simple Eye) and otolith (stone
like iinternal ear).
e. g. - Ascidian
Ascidian
Order 2. Pleurogona
➢ Body compact and not divided.
➢ Gonads two or more embedded in mantle
➢ Larva with otolith. Separate eye absent.
Examples: Herdmania, Botryllus.
Herdmania
Botryllus
Class: (B): Larvacea
➢ Neotic form which retain the larval form
throughout adult life.
➢ Test temporary.
Example: Oikopleura, Appendicularia,
Fritallaria.
Oikopleura Appendicularia Fritalaria
Class: (C): Thaliacea
➢ Musculature of body wall is in the form of
circular bands and barrel like body.
➢ Life history exhibits an alternation of
generation.
➢ Free swimming pelagic forms.
➢ Solitary and colonial.
Order -1:- Cyclomyaria (Doliolida)
➢Test is moderately well developed, never much
thickened.
➢Muscle-bands are always complete surrounding
the body.
➢Life history exhibits an alternation of generation.
Examples: Doliolum.
Doliolum
Order 2. Hemimyaria (Salpida)
➢Test is well developed and transparent.
➢Muscle-bands are always incomplete ventrally.
➢Life history exhibits an alternation of
generations.
➢Tailed larva absent.
Examples: Salpa.
Salpa
