1 st Year Undergraduate Model 1 UGC Syllabus. Animal Diversity-1

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1 Academic Script Course Name: Paper No. & Title: Zoology 1 st Year Undergraduate Model 1 UGC Syllabus Z 101 B Animal Diversity-1 Topic No. & Title: Practical - 14 Echinoderms : Specimen Study

2 Academic Script: - 1.Introduction: Expert: Today we will study something new in zoology, which is common but many more things yet to be studied. Echinoderms date back to the Paleozoic era and there were numbers of them, but recent survey says that there are about 7000 species, which exist. What is our knowledge regarding echinoderms is, a layman knows a starfish which you can see in the sea or in the oceanic area. It is a feather star or brittle star or an urchin. But regarding zoological studies, we should know what are the final characters of particular specimen or a particular animal, which we observe. Echinoderms are organisms that are highly specific in habitat. They are exclusively marine residing in various areas at various depths. Most of them inhabit bottom areas and are found in deep seas. They are found in a variety of colors and varied structures. All the living organisms are classified into different groups according to the similarity in their characters. The science of classifying and placing the organisms in a particular position is known as systematics. This includes identification, classification and study of the organism in relation to others,if there is any. Echinodermata is one such phylum of Kingdom Animalia which is very special. They are invertebrates. The term Echinodermata is derived from Gr. Echinus-Hedgehog and derma-skin. Initially, the term was applied to echinoids only. (Jacob Klein-1734) However, in 1791,Bruguiere applied the term Echinodermata for all the animals placed in this phylum. For years, these animals were included in a group radiata along with the coelenterates, due to their radial symmetry. These are a well-defined group of animals and are dated back in the history since the Paleozoic era. They exhibit a lot of diversity. There are about 7000 species, which include starfishes, Sea cucumbers, feather stars, Sea urchins and many more. Water vascular system and tube feet are specific of this type of animals.

3 They are also the only major group of dueterostome invertebrates. They can be defined as triploblastic, unsegmented, coelomate animals that are enterocoelous. They are having pentamerous radial symmetry which can be better understood as biradial symmetry with oral-aboral axis. This radial symmetry has been originally derived from bilateral symmetry, which can be observed in larval stages of echinoderms. Expert: With this little background regarding echinoderms, first let us study the general characters. One thing we are knowing very clearly about it, that they are found in oceanic sea areas only and there are specific characters. They are having very exclusive characters which are not found in other groups. 2.Characteristics : Echinoderms do not have a distinct head, but the surface with mouth is called as oral surface and the opposite surface of the body termed as aboral. They have an endoskeleton of calcareous plates or ossicles. These organisms have a peculiar system, which is hydraulic ambulacral, or water vascular system that originates from coelome. They connect with podia or tube-feet that are extensions of the body wall. This project through the holes in the skeleton. These holes are referred to as ambulacra, and hence this system is also termed as ambulacral system. There is a complete digestive system. The five alternating anti-radii are called anti ambulacra. The function of tube feet is locomotion. The echinoderms have a diffuse nervous system. A specific nephridial system is absent and the gonads open directly into the exterior of the body through specific ducts. They do not have any parasitic forms and have great powers of regeneration. In echinoderms sexes are separate i.e. they are dioecious with few exceptions. Reproduction is sexual. A few echinoderms may reproduce asexually or by regeneration. They exhibit external fertilisation. Development is indirect involving the intermediate stages of larval form, which is of different type in different classes.

4 Expert: As we have studied regarding the characters, we should know about the classification or taxonomical status of the organisms. Now this is known as Systematic. It is the study of a particular class. Actually you can further divide into subclass right up to the genus species. So let us study one by one all the systematic and the taxonomical status of animals, which are included in Phylum Echinodermata. 3. & Sub-phylum Pelmatazoa : of Echinoderms: Echinoderms are spread worldwide in marine systems and are very beautiful with varied colors. According to Hyman L.H. (1955), the classification of echinoderms is explained here. They are classified into two sub phyla i.e. 1) Pelmatazoa 2) Eleutherozoa. The sub phylum Pelmatazoa has only one living class Crinoidea, while sub phylum Eleutherozoa has four living classes : (1) Asteroidea (2) Ophiuroidea (3) Echinoidea (4) Holothuroidea There are many classes of echinoderms that are extinct. Only living classes have been discussed here. Sub-phylum: Pelmatazoa The term Pelmatazoa means stalked animals. (Pelmatos-stalked, zoan-animal) It contains mostly the extinct echinoderms as well as living forms. The mouth and the anal aperture is present on the oral surface. The calcareous ossicles support the stalk. Aboral cup or calyx is present. Ciliated ambulacral grooves are restricted to aboral surface. The main nervous system is present on the aboral surface.

5 Class: Crinoidea It is the only living class of this sub-phylum. (Gr. Crinon-Lily, eidos-form) Contains both living and extinct forms. Body has a pentamerous symmetry, it contains a long stalk and a cup like calyx and an oral roof called tegmen. The oral surface of the crinoids is directed upwards and anus is situated near the mouth. Arms are extended, movable and usually branched. Generally they are five or ten in numbers. Tube-feet are without suckers and the ambulacral grooves extend to the tip of the arms. In crinoids, madreporite, spines and pedicellaria are present. The animals are dioecious i.e. sexes are separate. Presence of intermediate stage in the form of doliolaria larva or pentacrinoid larva during development. Crinoidea is divided into four orders: 1) Inadunata 2) Flexibilia 3) Camerata 4) Articulata Ex. 1) Antedon 2) Rhizocrinus 4.Sub-phylum Eleutherozoa : Sub-phylum : Eleutherozoa The term Eleutherozoa means free living animals. It is derived from Gr. Eleutheros- free and zoan-animals. It consists mostly of existing echinoderms. They do not have a stalk or a stem. They exhibit a pentamerous symmetry. The oral surface is generally lower bearing the mouth. Anus is positioned on the aboral surface on the upper side. Here the ambulacral grooves do not function as food gatherers and have tube-feet for locomotory purpose. Presence of a main oral nervous system. There are four classes in this sub-phylum : 1) Asteroidea 2) Ophiuroidea

6 Class : Asteroidea 3) Echinoidea 4) Holothuroidea This includes starfishes and related organisms. Body is flattened and star shaped, and hence the name Asteroidea. It is pentagonal in shape and contains a central disc and five radiating arms. A ventrally positioned ambulacral groove with tube-feet is present in each arm. The number of arms may vary from 5 to 50 radiating out from central disc. The function of tube-feet is locomotory. Ambulacral grooves are restricted to oral surface and are extended from peristome to the end of the arms. Anus is small and located on the aboral surface. Endoskeleton consists of calcaerous plates i.e. ossicles. Presence of small pedicellaria with spines. Madreporite is present on aboral surface. Sexes are separate and the gonads are arranged radially. The development includes larval stages bipinnaria and brachiolaria. Class Asteroidea is further classified into five orders: 1) Platyasteroidea 2) Hemizonida 3) Phanerozonia include 1)Luidia 2) Astropecten 4) Spinulosa include 1) Asterina 2) Echinaster 5) Forcipulata Class : Ophiuroidea This includes brittle stars and related organisms. The name is derived from Gr. Ophis-snake, oura-tail, eidos-form. Norman(1865) seperated these organisms from Asteroidea. Body is flattened and pentamerous with a central disc. The oral and aboral surfaces are distinct. Presence of five arms generally, but may be six or seven in numbers, and are long. Ambulacral groove is absent. Absence of anus and intestine.

7 Tube feet are present, but they are devoid of suckers. Presence of Madreporite on oral surface. Sexes are separate i. e. dioceous and gonads are pentamerous. The development is indirect including an ophiopluteus or pluteus larva which is free-swimming. Ophiuroids have great regeneration power and live in shallow to deep waters. Class Ophiuroidea is further divided into two orders as follows :- 1) Ophiurae : Ex. 1) Ophioderma 2) Ophioscolex 3) Ophiolepis 2) Euryalae : Ex. 1) Asteronyx 2) Astophyton 3) Astroporpa Class : Echinoidea This class includes Sea - Urchins, sand dollars and related organisms. Echinoids have globular body which is disc like or heart shaped with a rigid skeleton, sometimes disc-like, oval or heart shaped. Absence of arms and ambulacral grooves. Endoskeleton covers the body i. e. the test and has closely fitted calcareous plates. Calcareous plates can be clearly distinguished into five alternating ambulacral and anti-ambulacral regions. Presence of slender tube-feet having suckers projecting from the holes in the calcareous plates. Mouth and anus are either centrally or laterally positioned. On oral surface, mouth is surrounded by peristome. On the aboral surface, anus is surrounded by periproct. Numerous pedicellaria with stalk are present all over the body.they are three jawed. Organisms are dioceous and having pentamerous gonads. During development, a free swimming echinopluteus larva is observed. This class is divided into three sub - classes :- 1) Bothriocidaroidea 2) Regularia 3) Irregularia

8 Sub-class: Regularia Members of sub-class regularia have a globular body, mostly circular and sometimes oval. Location of mouth is central and oral and Peristome is present. Anus present on aboral surface and Periproct is present. Symmetry is pentamerous with two rows of inter ambulacral plates. A well developed Aristotle s lantern is present. Ambulacral madreporite is present. The sub-classes divides in to 6 orders as follows : 1) Lepidocentroida e.g. (a) Phormosoma (b) Sperosoma 2) Cidaroidea e.g. (a) Cidaris (b) Notocidoais 3) Aulodonta e.g. (a) Diodema (b) Astrophyga 4) Camarodonta e.g. (a) Echinus (b) Strongylocentrotus 5) Melonechinoida 6) Stirodonta Sub-class: Irregularia Outer covering of the body is flattened, oval or circular. They exhibit bilateral symmetry. On the oral surface, a centrally located mouth is present. Anus is present on oral or aboral surface; generally displaced posteriorly and marginal end is positioned outside the apical system of plates. Tube feet or podia are present but do not function as locomotory organs. This sub-class is divided into 4 orders : A. Helectypoida B. Cassiduloida C. Clypeastroida e.g. (1) Clypeaster (2) Laganum (3) Echinarachinus D.Spatangoida e.g. (1) Spatangus (2) Echinocardium Class : Holothuroidea This groups of organisms generally termed as sea cucumbers. (Gr. Holothurian = water polyp + eidos form).

9 Body is usually elongated in oral aboral axis and bilaterally symmetrical. Mouth is present on or near one end and anus is present at the another. The surface of body is rough and coarse in texture. Mouth has tentacles surrounding it and is attached to the watervascular system. Microscopic spicules or plates embedded in body wall form the endoskeleton. Presence of podia or tube feet which are locomotory in function. In holothuroids, digestive tract is long and coiled. Respiratory tree is present except in apoda. These are monoecious, and the gonads are in the form of single or paired tufts of tubules. This class is divided into 5 orders : 1) Aspidochirota e.g. Holothuria 2) Elasipoda e.g. Deima 3) Dendrochirota e.g. (1) Thyone (2) Cucumaria 4) Molpadonia e.g. (1) Molpadia (2) Paracaudina 5) Apoda e.g. (1) Synapta (2) Chiridota This is an outline classification of phylum Echinodermata. 5. Specimen Study & Summary : Expert: Now let us study a specimen or two from each class which are commonly known to us and represent the phylum. (1) Class :- Crinoidea (Specimen : Antedon) Subphylum : Pelmatazoa Class : Crinoidea Order : Articulata Genus : Antedon

10 (2) Class :- Asteroidea (Specimen :- Asterias) Sub-phylum : Eleutherozoa Class : Asteroidea Order : Forcipulata Genus : Asterias Another specimen of the class is Astropecten Phylum : Echinodermala Subphylum : Eleutherozoa Class : Asteroidea Order : Phenerozonia Genus : Astropecten (3) Class :- Echinodea (Specimen:-Echinus) Subphylum : Eleutherozoa Class : Echinoidea Sub-class : Regularia Order : Camarodonta Genus : Echinus Another specimen of Echinoidea is Echinarachinus : Sub phylum : Eleutherozoa Class : Echinoidea Sub class : Irregularia Order : Clypeasteroidea Genus : Echinarachinus (4) Class :- Holothuroidea (Specimen:Holothuria) Subphylum : Eleutherozoa Class : Holothuroidea Order : Aspidochirota Genus : Holothuria

11 Another specimen of the class is Cucumaria Calssification : Sub-phylum : Elutherozoa Class : Holothuroidea Order : Dendrochirota Genus : Cucumaria Expert: So now we are very clear about the classification pattern, the characters and various specimens of phylum echinodermata. So whenever we look at echinoderm, we shall have a clear idea about its characters as a zoologist. It is part of a beautiful and wonderful nature.