Coelomate Animals: Museum Specimens

Coelomate Animals: Here we can study the museum specimens of celomate animals their classification and characteristic.

Coelomate animals are those that possess a true coelom, a fluid-filled body cavity completely lined by mesodermal tissue. This group includes a wide variety of animals, from simple invertebrates (Mollusks, Annelids, Arthropods and Echniodermata) to complex vertebrate (Chordata) animals.

Coelomate Animals- Museum Specimens

1. Chiton or Ischnochiton

Classification :
Phylum …………. Mollusca
Class …………….. Amphineura
Order …………… Polyplacophora
Genus …………… Chiton (Sea mouse)

Characters:

1. Chitons are found in marine shallow waters, few species live in deep sea.
2. Commonly called as sea mouse, measuring about 1 to 5 cms.
3. Body is elliptical, bilaterally symmetrical and dorsoventrally flattened with small, head, large flat foot and dorsal mantle roof.
4. Head contains ventral mouth and labial palps.
5. Eyes and tentacles are absent. Mouth and anus are opposite ends.
6. Dorsal side of mantle contains a linear series of 8-calcareous overlapping plates marked with lines of growth. ‘Coelomate Animals: Museum Specimens’
7. Sometimes Chiton is eaten by man. The foot is called as sea beal.

2. Unio

Classification :
Phylum…………. Mollusca
Class ……………… Pelecypoda
Order ……………. Eulamellibranchiata
Genus ……………. Unio

Characters:

1. Unio found in ponds, lakes, rivers and streams.
2. Commonly called as fresh water mussel or clam.
3. Body is dark brown, bilaterally symmetrical and flattened and measuring 5 to 10 cm in length.
4. Animal is completely enclosed in equal bivalve shells.
5. Two valves are united together along the dorsal side in a straight hinge-line by hinge-ligament.
6. Anteriorly, in front of the hinge, there is a whitish, knob-like swelling on each valve, called as umbo.
7. Posteriorly, on lateral margins there are two openings; smaller one is exhalent siphon, while the larger one is inhalent siphon.
8. Sexes are separate but the male and female shells are alike.

3. Nereis

Classification :
Phylum …………. Annelida
Class …………….. Polychaeta
Order ……………. Errantia
Genus…………….. Nereis

Characters:

1. Nereis is found in marine water crawling type, living in temporary burrows in sand, 200 meters deep.
2. Commonly called as Rag worm or Clam worm and is the simplest annelid.
3. Examination of preserved specimen shows cylindrical and elongated body form which is divided into similar metameres or segments about 200 in number.
4. First few segments fuse to form head which is composed of (i) prostomium or preoral lobe, which carries prostomial tentacles, palps and ocelli; and (ii) peristomium (2 segments fused), which carries antero-laterally 4 pairs of peristomial tentacles.
5. Mouth is found on the anterior surface of the peristomium.
6. Body has metameres segments, except head and anal segment, contain each pair of locomotory parapodia.
7. Parapodia also serve as respiratory and circulatory functions. Each parapodium is composed of dorsal notopodium and ventral neuropodium.
8. Anal segment contains a pair or anal cirri.

4. Chaetopterus

Classification :
Phylum …………. Annelida
Class …………….. Polychaeta
Order …………… Tubicola
Genus ……………. Chaetopterus

Characters:

1. Chaetopterus is a tubicolous, marine and bioluminescent annelid which lives permanently in a U-tube.
2. Commonly called as paddel worm having greatly modified segments.
3. Tube is opaque, measuring approximately 50 cm long and about 1 cm in diameter.
4. Body is white, 30 cm long and divided into anterior, middle and posterior regions.
5. Parapodia are variously modified as for water pumping fans, sucking discs or food ball organs.
6. Anterior region comprises of 15 to 20 segments, having a funnel-shaped mouth.
7. Middle region has fused segments. The notopodia of segments 14 to 16 are fused in mid line to form three fans. Notopodia are fused to form suckers.
8. Posterior region is longer with a pair of parapodia in each segment, about 11 to 30 in number.

5. Eupagurus (Hermit-crab)

Classification :
Phylum …………. Arthropoda
Class……………… Crustacea
Sub-class ………. Malacostraca
Order …………… Decapoda
Genus…………… Eupagurus (The Hermit-crab)

Characters:

1. Eupagurus leads a commensal life. It adjust in the coils of molluscan shells.
2. Commonly known as Hermit-crab.
3. Body is reduced and asymmetrical but shows usual divisions into head, thorax and abdomen.
4. Head contains antennules, antennae and stalked eyes. Thoracic appendages protrude through the opening of the shell. First thoracic leg is chelate and rest reduced.
5. Abdominal appendages of the right side absent while those of left side reduced. Sixth left abdominal appendages (uropod) adapted for holding the body in hollow objects.
6. Seventh and eighth thoracic appendages are reduced and remain inside the mollusc shell.
7. Uropods are hooked and notched in the shell.

6. Palamnaeus (Scorpion)

Classification :

Phylum ………….. Arthropoda

Class ……………… Arachnida

Order ……………. Scorpionida

Genus ……………..Palamnaeus (Scorpion)

Characters:

1. Palamnaeus is a nocturnal arthropod, found in sand, crevices and under stones and in bark of dead trees.
2. Commonly called as scorpion.
3. Body is elongated, segmented and differentiated into anterior prosoma and posterior opisthosoma.
4. Opisthosoma is sub-divided into a broad anterior mesosoma and a narrow posterior metasoma.
5. Prosoma is covered dorsally by a carapace and its appendages are a pair of small chelate chelicerae, a pair of large chelate pedipalps, 4 pairs of walking legs and several ocelli.
6. Body is encased in chitinous covering. The dorsal side covering is called as tergum, side one pleuron and ventral one sternum.
7. Mesosoma is composed of 7 broad segments and metasoma of 5 narrow segments.
8. Last metasomatic segment is telson containing a sting.
9. Just beneath chelicerae there are I and II gnathobases.
10. Sexes are separate but without sexual dimorphism. Viviparous.

7. Asterias (Sea Star or Starfish)

Classification :
Phylum ………….. Echinodermata
Sub-phylum ……. Eleutherozoa
Class ……………… Asteroidea
Order …………….. Forcipulata
Genus ……………. .Asterias

Characters:

1. Asterias is a marine form, found below 200 fathoms on most of the eastern seashore
2. Commonly called as starfish or sea star.
3. Body is radially symmetrical, star-shaped and pentagonal.
4. Body or central disc of the animal is distinguished into downwardly directed oral (mouth) and upwardly directed aboral surfaces.
5. Central disc is continued into 5 arms.
6. Aboral surface is pink and contains conical spines. The finger-like semi-transparent branchiae and pedicellariae are also present on aboral surface.
7. Oral surface contains central actinostome or mouth, from which five ambulacral grooves extend, one in each arm.
8. The open ambulacral groove accommodates a large number of podia or tube feet. Water vascular system is well developed.
9. Pedicellariae are usually present and may be of more than one kind.
10. Sexes are separate. Fertilization is external. The larva is typically a bipinnaria developing into a brachiolaria before metamorphosis into adult.

8. Pentaceros

Classification :
Phylum …………… Echinodermata
Sub-phylum ……. Eleutherozoa
Class ……………… Asteroidea
Order …………..… Phanerozonia
Genus ……………. Pentaceros (Starfish)

Characters:

1. Pentaceros is the most common eleutherozoan echinoderm found in sea from shallow water to 1,000 fathoms.
2. Commonly called as sea pentagon or starfish.
3. Body is enclosed in a tough, hard and leathery integument containing several ossicles.
4. Central disc and the arms are fused together. Arms contain extension of gonad, coelom and the gut.
5. Body is differentiated into oral and aboral surfaces.
6. Aboral surface is brown and convex, containing rows of definitely arranged spines.
7. There is a rounded sieve plate or madreporite plate in one of the inter-radii. It forms the first part of the water vascular system which is well developed.
8. Oral surface is concave, dark brown, having a centrally-placed mouth or actinostome.
9. Ambulacral groove contain double rows of locomotory organs of tube foot.
10. Sexes are separate. Development indirect which includes bipinnaria larva.

9. Balanoglossus

Classification :
Phylum ……………. Hemichordata
Class ……………….. Enteropneusta
Genus ……………….Balanoglossus (Acorn Worm)

Characters:

1. It is a marine animal. adapted for burrowing life in the sandy bottom.
2. Balanoglossus is commonly called as ‘Acorn worm.’ It lives in a V-shaped burrow and at one opening of burrow fecal castings may be seen. U-tube burrow at other end has opening for anterior end and also another additional opening.
3. It measures 10 cm to 2.5 meters, depending on the species.
4. It is bilaterally symmetrical, triploblastic deuterostome with worm-shaped body divisible into three regions-anterior proboscis or prosoma, middle co!lar or mesosoma and posterior trunk or metasoma.
5. Proboscis is conical, collar is funnel like, while trunk is cylindrical.
6. Proboscis contains heart vesicle, central sinus and buccal diverticulum.
7. Collar contains the mouth and colla. coelom which opens by a pair of collar pores on dorsal surface.
8. Trunk region contains most of the internal organs, such as pharynx, gonads or hepatic region.
9. Alimentation is complete and circulatory system usually contains contractile sac of heart.
10. Sexual dimorphism. Fertilization external and development includes tornaria larva. It possesses power of regeneration. ‘Coelomate Animals: Museum Specimens’