AND CLASSIFICATION OF PHYLUM PORIFERA GENERAL … · The phylum Porifera has been broadly classif ied into three classes:-Class 1 – Calcarea:- Commonly called ‘chalk sponges’

GENERAL CHARACTERISTICSAND CLASSIFICATION OF

PHYLUM PORIFERAFOR B.Sc. PART – I(HONS. & SUBSI.)

PAPER – I

BYDr. DILEEP KUMAR

ASSISTANT PROFESSORDEPARTMENT OF ZOOLOGY

B.N. COLLEGE, PATNA

The word ‘Porifera’ has been derived from two Latinwords- ‘Porus’(meaning pore) and ‘ferro’(meaning tobear). Hence the phylum Porifera include the animalsbearing pores.

The term Porifera was given by Grant.The animals are invertebrates with numerous openings,

called ostia, on their body.

INTRODUCTION

▶ The members of the phylum Porifera are commonlyknown as ‘sponges’

▶ These animals bear pores on their body surface▶ They represent the first step towards multicellularity▶ Sessile, sedentary and they spend their lives anchored

to a rock or ocean bottom

GENERAL CHARACTERS

▶ All are aquatic and mostly marine▶ Have choanocytes(flagellated cells)▶ They have a peculiar canal system through which

water current flows and conveys food and oxygen▶ Body shape is vase or cylinder-like, asymmetrical or

radially symmetrical▶ The body surface has numerous pores called ostia and

a large opening called osculum▶ Cellular level of body organisation and diploblastic

GENERAL CHARACTERS

▶ The interior space of the body is either hollow orpermeated by numerous canals lined with choanocytes

▶ Skeleton consisting of either fine flexible spongingfibres, siliceous spicules or calcareous spicules

▶ Mouth absent, digestion intracellular▶ Excretory and respiratory organs absent▶ Nervous and sensory cells are probably not

differentiated

GENERAL CHARACTERS

▶ Hermaphrodite, reproduction by both asexual andsexual methods

▶ Asexual reproduction by buds and gemmules▶ Sexual reproduction by ova and sperms, fertilization is

internal but cross-fertilisation as rule▶ Cleavage is holoblastic, development is indirect

through a free-swimming ciliated larva calledamphiblastula or parenchymula

▶ Organization ascon type, scontype and leuconoid type

GENERAL CHARACTERS

The phylum Porifera has been broadly classified into threeclasses:-

Class 1 – Calcarea:-▶ Commonly called ‘chalk sponges’▶ They have a skeleton of separate calcareous spicules which

are monaxon or tetraxon▶ They are solitary or colonial▶ Body shape is vase-like or cylindrical▶ They may show asconoid, syconoid, or leuconoid structure▶ They are found in shallow waters in all oceans▶ The collar cells(choanocytes) are comparatively large

CLASSIFICATION OF PORIFERA

The class Calcarea has been divided into 2 orders:-Order 1 – Homocoela:-

▶ Asconoid sponges with radially symmetricalcylindrical body

▶ Body wall is thin and not folded▶ Spongocoel is lined by choanocytes(continuous)▶ E.g.-Leucosolenia, Clathrina


Order 2 – Heterocoela:-▶ Syconoid or leuconoid sponges having vase-shaped

body▶ Body wall is thick and folded▶ Choanocytes line only radial canals▶ Spongocoel is lined by flattened endoderm▶ E.g. – Sycon or Scypha, Grantia ETC.


Class 2 –Hexactinellida or Hyalospongiae:-▶ Commonly called glass sponges(skeleton made of

silicious spicules-triaxon with six rays)▶ No epidermal epithelium▶ Choanocytes line finger-shaped chambers▶ Cylindrical or funnel-shaped▶ Found in deep tropical seas


This class has been divided into 2 orders:-Order 1 – Hexasterophora:-

▶ Spicules are hexasters i.e., star-like in shape▶ Radial canals simple▶ Not attached by root tufts commonly attached to a hard

object▶ E.g. – Euplectella, Farnera etc.

Order 2 – Amphidiscophora:-▶ Spicules are amphidics. No hexasters▶ Attached to the substratum by root tufts▶ E.g. – Hyalonema, Pheronema


Class 3 – Demospongiae:-▶ Commonly known as ‘horn sponges’▶ Large sized, solitary or colonial▶ Skeleton may be of sponging fibres or of sponging fibres

with siliceous spicules or without skeleton▶ Spicules are monaxon or tetraxon and are differentiated

into large megasceleres and small microsceleres▶ Irregular body shape▶ Leuconoid type of canal system▶ Generally marine, few freshwater forms


This class has been divided into three subclasses:-Subclass 1.- Tetractinellida:-

▶ Sponges are mostly solid and simple rounded cushion-like flattened in shape usually without branches

▶ Skeleton comprised mainly of tetraxon siliciousspicules but absent in order Myxospongida

▶ Canal system is leuconoid type▶ Shallow water form


It has been classified into three orders:-Order 1. – Myxospongida:-

▶ Simple structure▶ Skeleton absent▶ E.g. – Oscarella, Halisarca, etc.

Order 2. – Carnosa:-▶ Simple structure▶ Spicules are not differentiated into mega- and micro-scleres▶ Asters may be present▶ E.g. – Plakina

Order 3. – Choristida:-▶ Spicules are differentiated into mega- and micro-scleres▶ E.g. – Geodia, Thenea etc.


Subclass 2. – Monaxonida:-▶ Skeleton consists of monaxon spicules with or without

sponging▶ Spicules are distinguished into megascleres and

microscleres▶ Shallow and deep water forms▶ Two rayed spicules are present


Subclass 3. – Keratosa:-▶ Body is rounded, massive with a number of

conspicuous oscula▶ Skeleton composed of network of sponging fibres only▶ Silicious spicules absent▶ E.g. – euspo0ngia, Hippospongia.

THANK YOU

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AND CLASSIFICATION OF PHYLUM PORIFERA GENERAL … · The phylum Porifera has been broadly classif ied into three classes:-Class 1 – Calcarea:- Commonly called ‘chalk sponges’