Non chordate

CLASSIFICATION OF NON-CHORDATES UPTO CLASSES

WITH SALIENT FEATURES

1. Phylum Porifera: From the Latin porus for pore and Ferre to bear, hence an animal with with pores. ~5000 species.

Characteristic features:-

a)    Multicellular; no true tissue; asymmetric; sessile

b)   spongin- protein fibers for structure;  spicules for skeleton

c)    filter feeders using collar cells (choanocytes) & amoebocytes

d)   Water enters pores and exits osculum

e)    asexual reproduction - fragmentation

f)     sexual reproduction - hermaphroditic

g)    External fertilization – shed gametes in water

Classification

Phylum Porifera can be divided into four classes:

a)    Class Calcarea: They are characterized by the presence of spicules made of calcium carbonate. e.g. Sycon, Leucosolenia.

b)   Class Hexactinellida: They are characterized by the presence of spicules six-rayed spicules are made silica. Eg. Euplectella .

c)    Class Demospongiae: They are characterized by the presence of siliceous spicules , in some species by spongin  fibres, and others have a mixture of spongin and spicules. Eg: Hippospongia communis and Spongia officinalis,

d)   Class Sclerospongiae: They are characterized by the presence of spicules constructed from calcium carbonate, silica and spongin. e.g. Sclerospongia sp.

2. PHYLUM COELENTERATA(Cnidaria):~ 9000 species

Characteristics  features:

a)    Radial symmetry; true tissues; sessile and/or motile

b)   Cnidocytes - stinging barbs to capture prey

c)    Tentacles to bring prey into gastrovascular cavity

d)   Nervous system in the form of a nerve net

e)    Two body forms

–Polyp – sessile with mouth dorsal

–Medusa – motile with mouth ventral

f)     Asexual reproduction - budding

g)    Sexual reproduction - external fertilization

Classification

a) Class Hydrozoa: They may be solitary or colonial form. Cnidocytes present in the epidermis; they possess many polyps. eg. Hydra, Obelia.

b) Class Scyphozoa : They are solitary cnidarians. Medusa prominent in the life history; polyp are small; cnidocytes present in the gastrodermis as well as epidermis; Eg. Aurelia.

c) Class Cubozoa : They are also solitary cnidarians. Medusa prominent in the life history; polyp are small; Eg Chironex, carybdea

d) Class Anthozoa Colonial or solitary polyps; medusa absent; cnidocytes present in the gastrodermis; Eg. Metridium, Sea anemones

3. Phylum Platyhelminthes ~25,000 known species.

Characteristic features

a)    Bilateral symmetry

b)   Nervous system: ganglia and nerve chords

c)    Excretory system: flame cells

d)   Digestive system:  two-way digestive tract with common mouth/anus; gastrovascular cavity

e)    Respiratory system:  diffusion through epidermis

f)     Circulatory system:  none (diffusion)

g)    Reproductive system: 

                     I.        Sexual – internal fertilization; hermaphroditic; lay eggs

                   II.        Asexual – fragmentation

Classification

1. Class Turbellaria: Usually free-living forms with soft flattened bodies. Eg: Dugesia, Planocera.
2. Class Trematoda :Body Leaflike or cylindrical in shape; endoparasites OR ectoparasites complex life cycle with more than one host. Eg: Fasciola, Schistosoma.
3. Class Monogenea :B ody usually leaflike to cylindrical in shape, all parasitic, mostly on skin or gills of fish. Eg: Dactylogyrus, Polystoma,
4. Class Cestoda: (Tape worms)Body plan tapelike; Head or scolex with suckers or hooks; body usually divided into segments of proglottids; parasitic in digestive tract of all classes of vertebrates. Eg: Diphyllobothrium, Taenia.

4. Phylum Nematoda – The Roundworms, ~12,000 species

Characteristic features

a)    The body of a roundworm is long, smooth and unsegmented.

b)   Roundworms have a complete digestive system with mouth and anus.

c)    Bilateral symmetry.

d)   Excretory system of either one or more gland cells, a canal system without gland cells, or both gland cells and canals together.

e)    Reproduction – sexual; complex life-cycle with multiple hosts

Classification

a)    Class Secernentea (Phasmidea): Paired glandular or sensory structures called phasmids are present in the tail region; Eg.Ascaris, Enterobius.

b)    Class Adenophorea (Aphasmidia) Phasmids absent; Eg Trichinella, Trichuris.

5. PHYLUM ANNELIDA, ~ 15,000 species

Characteristics features

a)    Body metamerically segmented; bilateral symmetry

b)   Closed circulatory system

c)    Digestive system complete

d)   Respiratory gas exchange through skin, gills, or parapodia

e)    Excretory system typically a pair of nephridia for each metamere

f)     Nervous system with a brain, double ventral nerve cord and a pair of ganglia with lateral nerves in each metamere;

g)    Hermaphroditic or separate sexes;

Classification

a.    Class Polychaeta: Mostly marine; distinct head bearing eyes and tentacles; mostly segments with parapodia. Eg: Nereis, Glycera

b.   Class Oligochaeta: Body with conspicuous segmentation; no parapodia; head absent; Eg: Lumbricus ,Stylaria

c.    Class Hirudinea: Body with fixed number of segments (usually 34) with many annuli; no parapodia; setae absent.. Eg: Hirudo, Placobdella.

6. PHYLUM MOLLUSCA. ~50,000 living and 35,000 fossil species.

Characteristics features:

a)    Bilaterally symmetrical

b)   part body plan:

-Visceral mass – contains organs

-mantle – secretes shell

-foot – locomotion

c)    Circulatory system open but mostly closed in cephalopods

d)   Nervous system of paired cerebral, pleural, pedal, and visceral ganglia, with nerve cords and sub epidermal plexus.

e)    Reproduce sexually; many hermaphroditic; form trochophore larvae

Classification

a)    Class Caudofoveata : Wormlike; shell, head, and excretory organs absent;. Eg: Chaetoderma, Limifossor.

b)   Class Solenogastres : Wormlike; shell, head, and excretory organs absent; foot represented by ventral pedal groove. Eg: Neomenia.

c)    Class Monoplacophora: Body bilaterally symmetrical with a broad flat foot; a single shell; large coelomic cavities; Eg. Neopilina

d)   Class Polyplacophora : Elongated body , dorsoventrally flattened body with reduced head; foot broad and flat. Eg : Mopalia, Chaetopleura.

e)    Class Scaphopoda: Body enclosed in a one-piece tubular shell open at both ends; conical foot; Eg Dentalium

f)     Class Gastropoda :Body asymmetrical; usually in a coiled shell foot large and flat;Eg. Physa, Helix

g)    Class Bivalvia : Body enclosed in a two-lobed mantle; no radula; Eg: Mytilus ,Venus.

h)   Class Cephalopoda : Shell often reduced or absent; head well developed with eyes and a radula; head with arms or tentacles; Eg: Octopus, Nautilus.

7. PHYLUM ARTHROPODA

Characteristics of the phylum Arthropoda:

a)    largest and most diverse phylum; includes insects, crustaceans, spider

b)   segmented bodies – head, thorax, & abdomen or cephalothorax & abdomen; segmentation apparent on abdomen.

c)    Jointed  appendages (3, 4 or 5 pairs of walking legs plus assorted other specialized appendages)

d)   Respiration:  spiracles into trachea; gills;  book lungs

e)    Excretion through Malpighian tubules

f)     Incomplete or complete metamorphosis

g)    exoskeleton of chitin              

h)   ventral nerve cord & brain      

i)     open circulatory system         

j)     Sexes usually separate, parthenogenesis in a few forms;

Classification:

I. Subphylum Trilobita : All extinct forms. Trilobed shape of the body.

II. Subphylum Chelicerata: Chelicerate are characterized by having six pairs of appendages.

a.    Class Merostomata : All aquatic. Body with cephalothorax and abdomen; sharp telson; Eg. horseshoe crabs.

b.   Class Pycnogonia:. Body chiefly cephalothorax; usually four pairs of long legs and one pair of subsidiary legs for egg bearing. Example: Pycnogonum.

c.    Class Arachnida Four pairs of legs; segmented or unsegmented abdomen. Eg: Spiders, mites, ticks.

III.Subphylum Crustacea:

a.    Class Branchiopoda : Flattened, leaflike swimming appendages with respiratory function. Examples: Triops, Lynceus, Daphnia.

b)   Class Maxillopod: They have five cephalic, six thoracic, and usually four abdominal somites and they possess unique maxillopodan eye. Eg: Cypris, Cyclops.

c)    Class Malacostraca: Usually with eight thoracic and six abdominal somites.Eg. shrimps, crayfishes, lobsters, crabs.

IV.Subphylum Uniramia: insects and myriapods.

a)    Class Chilopoda : Dorsoventrally flattened body; variable number of somites, each with one pair of legs. Eg: centipedes ,Cermatia,

b)   Class Pauropoda : Cylindrical body consisting of double segments and bearing nine or ten pairs of legs; no eyes. Example: Pauropus.

c)    Class Symphyla:  Body consisting of 15 to 23 segments with 10 to 12 pairs of legs. Example: Scutigerella.

d)   Class Insecta: Body with distinct head, thorax, and abdomen; pair of antennae; mouthparts modified for different food habits; Eg. Mosquitoes

8) PHYLUM ECHINODERMATA ~7000 species

Characteristics feature:

a)    Adults mostly with pentaradial symmetry .

b)   No head or brain.

c)    Locomotion by tube feet or by movement of spines, or by movement of arms

d)   Respiration by dermal branchiae, tube feet, respiratory tree (holothuroids), and bursae (ophiuroids)

e)    Excretory organs absent

f)     Sexes separate (except a few hermaphroditic).

Classification

a)    Class Crinoidea:  Five arms ; tentacle-like tube feet for food gathering. Eg: Antedon, Nemaster.

b)   Class Concentricycloidea: Disc-shaped body, with marginal spines but no arms. Eg: Xyloplax

c)    Class Asteroidea : Star shaped, with arms not sharply demarcated from the central disc; tube feet often with suckers; Eg: Asterias, Pisaster.

d)   Class Ophiuroidea : Star shaped, with arms sharply demarcated from central disc; tube feet without suckers .Eg: Ophiura, Astrophyton

e)    Class Echinoidea : More or less globular or disc-shaped, with no arms; Eg: Arbacia, Strongylocentrotus .

f)     Class Holothuroidea : Cucumber-shaped, with no arms. Eg: Parastichopus, Cucumaria.

Hello guys... this is a very brief summary of Non chordate classification. But if you want to know the classification of each phyla in much details please visit other posts of my blog... you will get it.... thankyou