The Ctenophora are a phylum of marine animals commonly known as comb jellies. They have transparent gelatinous bodies and swim using rows of ciliary plates. There are about 80 known species found in coastal waters. They were formerly classified under Coelenterata but are now placed in their own phylum. Ctenophorans can be divided into two classes - Tentaculata which have two tentacles, and Nuda which lack tentacles and includes only the predatory genus Beroe.

1. Phylum Ctenophora: Classification and
Features
The Ctenophorans are a small group of firee-swimming. planktonic marine animals with
transparent, delicate, gelatinous bodies. They are commonly known as sea wainuts or comb
jellies. About 80 known species are present in this phylum and are abundant in coastal water.
Formerly this phylum was placed under coelenterata but Hatschek (1889) placed it under a
separate phylum Ctenophora.
Etymolog:
Greek: ktenos, comb; phoros, bearing
Diagnostic Features of Phylum Ctenophora:
i. Exclusively marine; solitary and mainly pelagic.
ii. The radial symmetry is rendered biradial by two tentacles (radial + bilateral).
ii. Body wall two layered; mesoglea is thick and has amoebocytes and smooth muscle fibres.
iv. Cnidocytes absent but tentacles carry Tasso celis (colloblasts).
V. Eight meridional rows of ciliary plates are present which help in locomotion.
vi. Carnivorous animals having gastro-vascular cavity with mouth and anal pore.
vii. Respiratory exchange takes place by diffusion.
viii. Presence of luminescence.
ix. Nervous system is in the form of a sub-epidermal nerve network which is particularly well
developed beneath the comb rows.
x. Hermaphrodite; a few reproduce asexually. Cleavage complete, determinate type, leading
ulimately to a 'cydippid' larva.
Scheme of Classification ofPhylum Ctenophora:
The first definite description of ctenophores was given by Martens (1671). It was Hatschek
(1839) who put all the ctenophores under a distinct phylum. Nearly all authors have divided
ctenophores into two classes, the Tentaculate (six orders) and the Nuda (beroids only).
Parker and Haswell, 1972 (as revised by Marshall and Williams, 7th edn.), has also divided
clenophores into 2 classes-- Tentaculata (Mierupharyngea) und Nuda(Macroplharynge4)

2. However, according to Meglitsch and Schram (1991), as the groups are poorly known,
separation at the class level was not attempted. The classification followed in this text is after
Ruppert and followed in this text is
after Ruppert and Barnes, 1994
(6th edn).
abxoral se1se organ Comb rwS
ana anal
ore cana
rctractilJe tentacl
Cntaci
tcntacle
sheutli
men
Phylum Class
dronal
canal
stalcys
aboral astrevaCuBar canal
canal
peripherai netwirk of
AstfovaKuiar canai
stomach
E
N Tentaculata
pharyt
ciliary comb plates anal porec
Nuda ITouth
A
Comb
H
statcy tCntacle
R
A papillac
Out uth
ctacles
pharyngecal
statcyst comb piates
canal
subtenlacular
meridional canal pharynx
peripheral rctwork
of alimerilation
Systematic Resume of Phylum
Ctenophora:
gonads
Fig 143: A Pleurebruciua, B. Cirnoptarn.a, C" Velanun, D. CorhopBasa anet E Hurmphora
Class Tentaculata:
i. The members of this class possesses two tentacles.
ii. It is divided into 4 orders.
Examples:Hormiphore (Fig. 1.43E), Cestum and Velamen (Venus's girdle) (Fig. 1.43C).
Pleurobrachia (Fig. 1.43A), Ctenoplana (Fig. 1.43B), Coeloplana (Fig. 1.43D), Bolinopsis.
Class Nuda: mouth
i. The representatives of this class lacks tentacles.
ii. It includes only one order.
swimming
plates
iii. They are predators on other ctenophores.
Example: Beroe (Fig. 1.44).
infundibulum
Fig. 144: Beroe. Note that tentacles are absent.