In this article we will discuss about the nauplius, zoea and megalopa larva of crustaceans with the help of suitable diagrams.
Nauplius Larva of Crustaceans:
Fig. 147 NAUPLIUS LARVA W.M
1. It is the slide of Nauplius larva, which is the earliest free swimming stage in the development of crustaceans.
2. Body is some what fusiform or pear shaped and is without segmentation.
3. The head bears paired mitanous antennae and biramous antennule and mandibles and a median sessile eye.
4. All appendages bear setae.
5. This larva possesses only alimentary canal and no other organ. After spending free swimming life it metamorphoses into metanauplius.
Zoea Larva of Crustaceans:
Fig. 148 ZOAEA LARVA W.M
1. It is the slide of Zoea larva, which is the fourth stage in the life cycle of crustaceans.
2. This larva develops from Protozoa.
3. The body is divisible into cephalothorax and a long segmented abdomen.
4. The cephalothorax is covered over by carapace and bears paired compound eyes and paired appendages e.g., antennules, antennae, mandibles, maxillae and maxillepedes and five pairs of gills.
5. The carapace is produced into a long and pointed rostrum and a long median dorsal spine with many small bristles.
6. The cephalothorax also bears buds for 6 pairs of thoracic appendages.
7. The abdomen has six segments with paired rudiments of abdominal apeandages and a pair of caudal forks.
8. It metamorphoses into Metazoea and ultimately into Megalopa.
Megalopa Larva of Crustaceans:
Fig. 149 MEGALOPA W.M
1. It is the slide of Meglaopa larva of crustaceans.
2. It develops from Zoea larva through Metazoea stage.
3. The body is divisible into a large anterior cephalothorax and a long posterior abdomen.
4. The cephalothorax bears paired antennules, antennae, mandibles, stalked compound eyes and five pairs of thoracic legs and is covered over by a carapace.
5. The carapace is produced in front into a median rostral spine.
6. Of the thoracic legs the first paired is chelate and the rest non-chelate.
7. The abdomen bears six segments and five pairs of plumose pleopods.
8. It metamorphoses into the adult crustacean.