Palaemon (Freshwater Prawn) Appendages

The appendages of Palaemon, the freshwater prawn, are a marvel of nature's engineering. Its formidable claws, equipped with sharp pincers, serve both as formidable weapons for defense and efficient tools for capturing prey. With these versatile appendages, Palaemon navigates its aquatic habitat with precision and thrives in various freshwater environments.

1. Indian River water prawn is called Palaemon. The marine water prawn is called Pegasus.
2. The body of the prawn is divisible into Cephalothorax and abdomen.
3. Cephalothorax is made of 13 segments which include cephalic and thoracic regions.
4. The cephalic region contains 5 segments and the thoracic region contains 8 segments.
5. In the abdomen 6 segments are present.
6. The cephalothoracic region is covered by a carapace, k produces anteriorly a rostral spine.
7. In the abdomen, the segments are seen.
8. Each segment is covered on the dorsal side by a convex tergal plate and a ventral thin sternal plate.
9. Both are connected on the sides by pleuron.
10. In the abdomen, the appendages are attached to a small plate, called Epimeron on the pleuron.

Cephalothoractc appendages

1. These are 13 pairs.
2. The first 5 pairs are called Cephalic appendages.
3. The next 8 pairs are Thoracic appendages.

Cephalic appendages

1. Antennules: The protopodite is 3 segmented, with basal structure precoxa, coxa, and basis.
2. In the precoxa a statocyst is present.
3. It maintains the equilibrium of the animal.
4. Based on 2 long, many segmented whip-like feelers are present. They are tactile sense organs.
5. They are not homologous to exopodite and endopodite.
6. The outer feeler is further divided into an inner smaller branch and an outer larger branch.

Antenna

The protopodite shows coxa and basis.

1. Endopodite is a long feeler-like structure, which is a tactile sense organ.
2. The exopodite is a plate and it is called Squama.
3. It works as a balancer during swimming.
4. At the base of the coxa renal opening is present.
5. The antenna is sensory, excretory, and balancing in function.

Mandibles

They are present on either side of the mouth.

1. The basal part of coxa is divided into two parts, it shows a mandibular and incisor process.
2. The mandibular process shows 5 or 6 dental plates.
3. The incisor process shows 3 teeth. On the outer margin of the head, a mandibular palp is present, which represents the basis and endopodite.
4. The exopodite is absent. The mandibles are masticatory in function.

I Maxilla or Maxillula

1. The protopodite is 2 lobed. They are called Gnathobases.
2. The endopodite is slender. Exopodite is absent.
3. It helps in the manipulation of the food.

II. Maxillae

The protopodite is fait and is divided into 4 lobes.

1. Endopodite is small and unsegmented.
2. The exopodite is a broad, and plate-like structure.
3. It is called Scaphognathite or baler. It is useful to bring water into the branchial region.
4. It is helpful for respiration and the manipulation of food.

Thoracic appendages

1. They are 8 pairs.
2. The first 3 pairs are Maxillipedes.
3. The remaining 5 are walking legs.
4. I Maxillipede: They are thin and leaf-like.
5. Protopodite is 2 segmented. The endopodite is short.
6. Exopodite is present.
7. It is bilobed. Epipodite is respiratory in function.
8. It is present on the outer side of the coxa.

II. Maxillipede

It has 2 segmented protopodite.

1. Coxa bears a conical epipodite and a gilk Endopodite is 5 segmented.
2. The five segments are ischium, merus, carpus, propodus, and dactyls. Exopodite is long and unsegmented.

III. Maxillipede

It looks like a walking leg. It has 3 segmented endopodites.

1. The basal segment corresponds to the ischium and merus.
2. The apical segment is fused and corresponds to propodus and dactyls.
3. The middle one is carpus.

IV. Walking legs

They are 5 pairs.

1. The first 2 pairs are chelate and the other 3 pairs are nonchalant.
2. They are useful for walking.
3. The typical walking leg has a two-jointed protopodite and 5 jointed endopodites.
4. The protopodite has two segments, coxa and basis.
5. The endopodite has ischium, merus, carpus, propodus, and dactyls.
6. In the first and second pairs of legs the propodus is prolonged beyond its articulation with dactyls and it looks like a chela or pincer.
7. Such legs are called chelate legs. They catch the food and push it into the mouth.
8. The second chelate, leg in males is larger and more powerful than in females.
9. The 3^rd, 4^th, and 5th walking legs are nonchalant.
10. In females, the 3rd walking leg bears a female reproductive opening on the inner side of the coxa.
11. In the male, the genital opening is present on the arthrodial membrane between the thorax and 5th walking leg.

Abdominal Appendages

1. The abdomen bears six pairs of appendages.
2. Each appendage is biramous. These are called pleopods or swimmers.
3. The protopodite has coxa and basis. The basis bears two flat leaf-like exo and endopodite.
4. From the inner margin of the endopodite, a small appendix interna arises.
5. In the females during breeding season the appendix interna of opposite appendages unite and carry eggs.
6. In the first pair of abdominal appendages, the appendix interna is absent.
7. The second abdominal appendage of the male shows appendix masculine also.
8. The sixth pair of abdominal appendages will be called Uropods or tail feet.
9. They are large and lie on either side of the telson.
10. The two uropods and telson together form a broad tailfin.
11. It helps the Prawn to take a backward spring in water.
12. In a uropod, the coxa and basis fuse to form a triangular sympod.
13. It helps the Prawn to take a backward spring in water.
14. In a uropod, the coxa and basis fuse to form a triangular sympod. It bears exo and endopodites.

Thus the appendages of Prawns are helpful in food collection, respiration, and locomotion.