HYDRAHYDRAAbul Kalam Rashad AhmedAbul Kalam Rashad Ahmed

Lecturer in ZoologyLecturer in ZoologyRajshahi Cadet CollegeRajshahi Cadet College

INTRODUCTION.INTRODUCTION.

1. It is a common fresh water polyp.1. It is a common fresh water polyp.

2. In 1774 it was first recognized by 2. In 1774 it was first recognized by Trembley Trembley

3. C. Linnaeus named it Hydra.3. C. Linnaeus named it Hydra.

4. It is a remarkable animal.4. It is a remarkable animal.

NAMING OF HYDRA.NAMING OF HYDRA. 1. It is resembled an ancient mythological 1. It is resembled an ancient mythological

Greek Monster-Hydra, which could recover its Greek Monster-Hydra, which could recover its head as soon as it was cut off. Hercules killed head as soon as it was cut off. Hercules killed it later on.it later on.

SPECIES OF HYDRA.SPECIES OF HYDRA. 1. 1. H. vulgaris.H. vulgaris. 2. H. oligactis.2. H. oligactis. 3. H. gangetica.3. H. gangetica. 4. Chlorohydra viridissima.4. Chlorohydra viridissima.

HABIT AND HABITATHABIT AND HABITAT 1. Hydra usually attached with 1. Hydra usually attached with

submerged vegetation.submerged vegetation.2. In winter it is available.2. In winter it is available.3. It lives on insects or insect larvae 3. It lives on insects or insect larvae

and small crus taceans.and small crus taceans.4. It is found in fresh water.4. It is found in fresh water.5. It is solitary in habit.5. It is solitary in habit.

HABITAT.HABITAT.

1. Hydra founds in ponds, ditches, 1. Hydra founds in ponds, ditches, lakes, lakes,

streams.streams.

2. Hydra is found in marsh, creek, 2. Hydra is found in marsh, creek, rivers, rivers,

and their tributaries.and their tributaries.

1. Diploblastic animal.1. Diploblastic animal.

2. Triploblastic animal.2. Triploblastic animal.

3. Distinction between diploblastic and 3. Distinction between diploblastic and triploblastic animal.triploblastic animal.

4. External morphology.4. External morphology.

a) Hedd, b) Basal disc, c) Mouth, d) Buda) Hedd, b) Basal disc, c) Mouth, d) Bud

e) Tentacles, f) Body, g) Testis, h) Ovarye) Tentacles, f) Body, g) Testis, h) Ovary

HISTOLOGY OF HYDRAHISTOLOGY OF HYDRA

1. EPIDERMIS.1. EPIDERMIS.

a) Epitheliomuscular cella) Epitheliomuscular cell

b) Interstitial cellb) Interstitial cell

c) Sensory cellc) Sensory cell

d) Nerve celld) Nerve cell

e) Gland celle) Gland cell

f) Germ cellf) Germ cell

g) Cnidoblastg) Cnidoblast

Internal Structure of HydraMouth

Tentacles

Hypostome

Nematocyst

Epidermis

Gastrodermis

Mesogloea

Bud

Coelenteron

Basal disc

Fig: L.S. of Hydra

Gland cell

Coelenteron

Gastrodermis

Epidermis

Mesogloea

GastrodermisEpidermis

MesogloeaFig: T.S. of Hydra

Interstitial

Cnidoblast

Musculo-epithelial

Pseudopodial

Nerve cell

Sensory Cell

Gland cell

Flagellated cellInterstitial cell

Fig: Histology of body wall in Hydra

BarbuleThread

Barb

Nematocyst

OperculumCnidocil

Thread

Nucleus

Fig: Cnidoblast at rest and with nematocyst discharged

Musculo-epithelial

Interstitial cell

Sensory cell

Nerve cell

Cnidoblast cell

Mucous

Fig: Ectodermal cells in Hydra

NEMATOCYST.NEMATOCYST.

1. Penetrant / Stenotele1. Penetrant / Stenotele

2. Volvent / Desmoneme2. Volvent / Desmoneme

3. Glutinant3. Glutinant

a) Stereoline glutinanta) Stereoline glutinant

b) Streptoline glutinantb) Streptoline glutinant

GASTRODERMISGASTRODERMISGastrodermis : The cell of gastrodermis are Gastrodermis : The cell of gastrodermis are

produced from the germinal endoderm. It produced from the germinal endoderm. It is composed of the following cells :is composed of the following cells :

1. Nutritive- muscle cell.1. Nutritive- muscle cell. a) Pseudopodial nutritive cellsa) Pseudopodial nutritive cells b) Flagellated Nutritive cellsb) Flagellated Nutritive cells 2. Interstitial cells.2. Interstitial cells. 3. Nerve cells .3. Nerve cells . 4. Sensory cells .4. Sensory cells . 5. Gland cells. 5. Gland cells. a) Mucous secreting gland cells.a) Mucous secreting gland cells. b) Enzyme secreting gland cells.b) Enzyme secreting gland cells.

3. MESOGLOEA.3. MESOGLOEA.

4. COELONTERON.4. COELONTERON.

5. Diff. Between Epidermis and 5. Diff. Between Epidermis and GastrodermisGastrodermis

6. Diff. Between Coelenteron and 6. Diff. Between Coelenteron and Coelom.Coelom.

7. Functions of all cells.7. Functions of all cells.

8. Dig. Of all cells.8. Dig. Of all cells.

FOOD, FEEDING, AND PROCESS FOOD, FEEDING, AND PROCESS OF DIGESTIONOF DIGESTIONNUTRITION.NUTRITION. 1. Definition.1. Definition. 2. Stages.2. Stages. a) Foods. B) Ingestion . C) Digestiona) Foods. B) Ingestion . C) Digestion d) Absorption. E) Assimilation. d) Absorption. E) Assimilation. f) Egestion.f) Egestion.FOOD.FOOD. 1. Insect larvae , 2. Arthropods . 3. Cyclops.1. Insect larvae , 2. Arthropods . 3. Cyclops. 4. Daphnia . 5. Fish eggs . 6. Nematodes. 4. Daphnia . 5. Fish eggs . 6. Nematodes. 7. Rotifers.7. Rotifers.

Description of the following points will be Description of the following points will be given :given :

1. Process of food intake.1. Process of food intake.

2. Digestion.2. Digestion.

a) Extracellular digestion.a) Extracellular digestion.

b) Intracellul;ar digestion.b) Intracellul;ar digestion.

3. Absorption.3. Absorption.

4. Assimilation.4. Assimilation.

5. Egestion.5. Egestion.

LOCOMOTIONLOCOMOTION

Definition : The special process by which an Definition : The special process by which an organism changes its position respond to organism changes its position respond to various environmental stimuli , is known as various environmental stimuli , is known as locomotion.locomotion.

Types of locomotion.Types of locomotion.

1. Looping. 2. Somersaulting.1. Looping. 2. Somersaulting.

3. Gliding. 4. Walking.3. Gliding. 4. Walking.

5. Swimming. 6. Climbing.5. Swimming. 6. Climbing.

7. Floating. 8. Drowning. 9. Spontaneous7. Floating. 8. Drowning. 9. Spontaneous

REPRODUCTIONREPRODUCTION

• Definition : The process by which two Definition : The process by which two opposite sex mate together and opposite sex mate together and produce same species to maintain produce same species to maintain their own existence and continuity of their own existence and continuity of the race is called reproduction.the race is called reproduction.

Type.Type.

1. Asexual reproduction.1. Asexual reproduction.

a) budding . B) Fission.a) budding . B) Fission.

2. Sexual reproduction.2. Sexual reproduction.

a) Formation of gamete.a) Formation of gamete.

1. Spermatogenesis.1. Spermatogenesis.

2. Oogenesis.2. Oogenesis.

3. Fertilization.3. Fertilization.

4. Development.4. Development.

Development.Development.

1. Morula phase.1. Morula phase.

2. Blastula phase.2. Blastula phase.

3. Gastrula phase. 3. Gastrula phase.

4. Hydrula.4. Hydrula.

Regeneration of Hydra.Regeneration of Hydra.

Immortality of Hydra.Immortality of Hydra.

Adult Hydra

Ovary

Testis

Young Hydra

CystEctoderm

Endoderm

Mesogloea

Ovary

Testis

Oogonia Mesogloea

Mesogloea

Dev. Of sperm

Spermatogonia

Spermatocyte Egg

Fertilization

Sperm

Hydrula Cyst wall Cleavage

Endodermalcells

Archenteron

Gastrula BlastulaFig: Life cycle of Hydra

DIVISION OF LABOUR IN HYDRADIVISION OF LABOUR IN HYDRA

• 1. Epitheliomascular cell.1. Epitheliomascular cell.• 2. Interstitial cell.2. Interstitial cell.• 3. Cnidocyte cell.3. Cnidocyte cell.• 4. Sensory cell.4. Sensory cell.• 5. Nerve cell.5. Nerve cell.• 6. Gland cell.6. Gland cell.• 7. Nutritive cell.7. Nutritive cell.• 8. Oral pore.8. Oral pore.• 9. Coelenteron9. Coelenteron• 10. Tentacles. 11. Pedal disc. 10. Tentacles. 11. Pedal disc.

SYMBIOSISSYMBIOSIS

Definition. The process by which two Definition. The process by which two organisms are living together and organisms are living together and both of them get benefit from each both of them get benefit from each other is called symbiosis. other is called symbiosis.

Type.Type.

1. Mutualism. 2. Parasitism.1. Mutualism. 2. Parasitism.

3. Commensalism.3. Commensalism.