Zoology

  SCOLOPENDRA CLASSIFICATION : PHYLUM ARTHROPODA (Jointed appendages). SUB-PHYLUM UNIRAMIA (Single branching appendage). CLASS CHILOPODA (Body divided into head & trunk). COMMENTS: •Commonly called as centipede . • Body is elongated, dark greenish-brown in colour, dorsoventrally flattened & is divided into a distinct head & a long segmented trunk or body . •Head appendages are long antennal, ocelli & reduced maxillae & mandible visible on ventral side. •Mouth is guarded by labrum, mandibles & first maxillae. •Body segments have 21 pairs of walking legs. The first pair of legs are curved , clawed & forwardly directed to form maxillipedes or poison claws. •Each leg is composed of coxa, trochantea, femur, tibia & 3 tarsi ending in a single claw. •Paired, oral spiracles lie on the pleural areas. •It is harmful to mankind. •Habit & Habitat : It is a tropical animal, found in India & America.

PALAEMON CLASSIFICATION PHYLUM:  ARTHROPODA (Jointed appendages). SUB-PHYLUM:  CRUSTACEA (Biramous appendages). CLASS: MALACOSTACA (carapace covers head/thorax). Comment: •Commonly called as "prawn". •Body is elongated, spindle shaped, bilalerally symmetrical and deep orange coloured when preserved. •Division the body are cephalothorax, abdomen & telson." •Cephalothorax is made up of 5 head & 8 thoracic segments. Carapace is anteriorly produced into sawthoothed rostrum. •There are two prominent eyes on the head. • Abdomen is made up of 6 segments. •There are 19 pairs of appendages, one pair in each segment. The cephalic appendages comprises of antennules, antennal,mandibles, maxillal & maxillulae. •First abdominal somite is not reduced. Rest 5 abdominal segments contain paired biramous swimming pleopods.

  SACCULINA CLASSIFICATION PHYLUM:  ARTHROPODA (Jointed appendages). SUB-PHYLUM: CRUSTACEA (Biramous appendages). CLASS:  CIRRIPEDIA (Adult sessile or parasitic). COMMENTS : •Commonly called as "Root-headed barnacle". •Parasitizes crabs. Zoologists were able to discover its real crustacean nature by studyings it embryology having 1st stage nauplius larva. • Adult loses all arthropodan characters & appears like a fleshy tumour attached to the abdomen of the crab on ventral side & lead a parasitic life on decapod sructures. •It sends root like structures like mycelium of fungus through peduncle in each appendages of crab & in the body to derive nutrition. • Appendages, segmentation, mouth, anus, alimentation absent. •Hermaphroditic, • Presence of sacculina causes development of many changes in secondary sexual characters of the host.

BALANUS   CLASSIFICATION : PHYLUM:  ARTHROPODA (Jointed appendages) SUB-PHYLUM: CRUSTACEA (Biramous appendages) CLASS: CERRIPEDIA (Adults sessile /parasitic) COMMENTS: •Commonly called as Rock Barnacle. •Stalk is absent to the shell covering animal is directly attached to the substratum or rocks. •Head is short & broad. • Mantle surrounding the body is covered six calcareous plates, consisting of unpaired carina, rostrum & 2 pairs of carino-lateral plates. Edges of the plates overlap & fit together forming a cylinder. • opening of the shell is provided with a movable fourfold lid or operculum, composed of 2 scuta or 2 terga. •In water, the barnacle protrudes through the opening six pairs of delicate, curled, fringed & jointed thoracic legs to collect food. • Life cycle includes nauplius larva. •Distribution: It has cosmopolitan distribution.

  CLASSIFICATION PHYLUM ARTHROPODA (Jointed appendages). SUB-PHYLUM CRUSTACEA (Biramous appendages). CLASS : BRACHIOPODA (Trunk appendages as gills). COMMENTS : • Commonly called 'water flea'. •Microscopic, attain a length of about 2 mm. • Body is oval & laterally compressed with a ventral beak on head & sharp caudal spine. •Head bears reduced uniramous antennules, & two very large biramous antennal. •A thin bivalved carapace covers the body except the head. • Carapace is transparent. • Sessile compound eyes are united to large structure. • 5 pairs of thoracic appendages food an efficient food gathering organ. • Abdominal appendages are absent. • Sexes are separate. • Brood pouch present in female but absent in males. Development of eggs take place in brood pouch.

CLASSIFICATION : Phylum :Arthropoda(Jointed legs) Sub-phylum :Chelicerata (Feeding appendages called chelicerae) Class : Arachinida (possess both lungs and tracheae). COMMENTS: • Commoly called as scorpion. • Body is elongated, segmented & differentiated into anterior prosoma and posterior opisthosoma. •Opisthosoma is sub-divided into a broad anterior mesosoma & a narrow posterior metasoma. •Prosoma is covered dorsally by a carapace. •Body is encased in chitinous covering. •Mesosoma is composed of 7 broad segments & metasoma of 5- narrow segments. • Last metasomatic segment is telson containing a sting. Ventrally the sternum of 1st segment contains a pair of genital openings. •Metastoma is limbless. •Sexes are separate without sexual dimorphism and Viviparous. • Habit & Habitat : It is a nocturnal arthropod. Found in sand. • Distribution : cosmopolitan distribution.

CLASSIFICATION : Phylum :Arthropoda (Jointed legs) Subphylum :Chelecerata (Feeding appendages called chelicerae) Class : Merostomata (exhibit pseudocopulation during mating). COMMENTS : • It is commonly known as king crab & it is a marine arthopod found burrowing in sand. • Body is comprised of anterior cephalothorax or prosoma & a posterior-opisthosoma. •Cephalothorax is broad, convex above & concave below & bears a pair of median & a pair of lateral eyes andthree longitudinal ridges above. •It also bears six pairs of non-locomotor limbs below around the mouth. All the legs,except the last pair, are chelate. •The opisthosoma is divided into mesosoma, metasoma & belson & is movably articulated with prosoma. • The first pair of appendages is united to form a genital operculum whereas remaining five pairs bear book gills or book lungs. • Malphigian tubules absent & excreation through coxal glands. •Regarded as living fossil. Indirect development.

 CO MMENTS : • Bilaterally symmetrical, primitively coelomate,Segmented protostomes. •Coelom reduced to the portions of the reproductive & excreatory systems. •Body segments primitively associated with one pair of jointed appendages. •Body divided into two or more tagmata (regions): -In mandibulates a head, with sensory and feeding functions, and trunk, often subdivided into a thorax (locomotory) & abdomen (digestive & respiratory functions). -In chelicerates a prosoma, with feeding & locomotary functions, and an opisthsoma, with digestive & respiratory function. •Exoskeleton typically chitinous (α-chitin) • Digestive system is complete with large stomodeal & proctodeal region lined by chitin in between it's midgut •Sense organs include sensillium & compounde eyes Brain tripartite. •Cardiovascular system (open) in which haemolymph is pumped by a heart. •Excreatory system includes saccular excreatory organs & Malphigian tubules. •Generally diocious, i...

  EVOLUTION OF COELOM Body cavity - A body cavity can mean any internal space or a series of spaces present inside body.   Coelom - The coelom is defined as a liquid filled cavity in the mesoderm. It develops in, and is surrounded by the embryonic mesoderm .  Pseudocoelom - The body cavity is formed by a persisting of the blastocoel . This is simply a space between the digestive tract and that part of the body wall not bounded by mesoderm. According to the nature of body cavities there are three major groups of triploblastic animals ↳ Acoelomata ↳ Pseudocoelomata ↳ Coelomata or eucoelomata 1) Acoelomata No body cavity or coelom is present. Embryonic mesoderm remains as a solid layer, space betweeen endoderm (gut wal) and ectoderm (bodywall) is filled with mesenchyme and muscle fibres . Ex. Porifera, Coelenterata, Ctenophora, Platyhelminthes and Nemertinea     2) Pseudocoelomata Body space is a pseudocoelom or false coelom . It is a persistent bla...

COMMENTS: • Intestine starts after 15th segment . It shows beaded appearence. Section is triploblastic with organ grade of construction and true coelom . • Intestine is divisible into 3 regions :- (i) Pre - typhlosolar region (15th to 26th segment). (ii) Typhlosolar region (from 26th segment to rectum)  (iii) Post typhlosolar region (rectum).  Typhlosolar region has median dorsal internal fold . • Body wall is composed of thin cuticle , columnar epidermis , thin circular muscle layer and thick longitudinal muscle layer, parietal coelomic epithelial layer. • Intestine is composed of outer visceral coelomic epithelial layer , intermediate longitudinal and circular muscle layer and it's lining is made up of endodermal columnar epithelial ( layer) cells. In typhlosolar region epithelial cells are raised to from typhlosole .  • Typhlosole is a median internal fold of dorsal wall having chloragogen cells and a capillary blood vessel. • Typhlosole increase the ...