Life cycle of Penaeus monodon

Classification: Phylum: Arthropoda

Class: Crustacea

Order: Decapoda

Family: Penaeidae

Genus: Penaeus

Species: Penaeus monodon

Life history: Adult shrimps are bottom dwellers the offshore areas at depth of 20 to

70 meters. The life cycle starts with the spawning or release of eggs by gravid or

ripe female.

Spawning occurs at night some host after copulation in species with an

open thelyum. Eggs are released in large numbers and fall slowly to the seabed.

200000-10 lac eggs are released in one time.

Embryonic development last between 12-18 hours at temperature

between 24-28˚c and salinity range from 32-35 ‰.

After spawning the larvae hatch out 12-15 hours. There are mainly six

phases enjoyed in the life cycle. Such as:

Embryo→Larvae→Juvenile→Adolescent→Sub-adult→Adult

In the larval stage: Six phases of nauplius, three phases of protozoa,

three phases of mysis are involved. After passing larval stage, the larvae

metamorphose into the post larvae.

The young post larvae or fry move shore wards and start appearing in

the coastal waters around two weeks into their post larvae life.

The continue migrations towards mangrove and other brackish water

areas which serve as their nurseries or feeding grounds, growing to large

juveniles, post juveniles and sub-adult. At this stage, Penaeus monodon is

mainly carnivorous, feeding on slow moving microscopic animals, small crabs,

shrimps, molluscs, marine worms, detritus etc.

Although first mating occurs in the estuaries, it is only during or after

migration back to the offshore areas that full ripenering of the ovaries takes

place. First spawning occurs at 10 months of age, upon arrival in the offshore

areas, followed by 2-3 more consecutive spawning within a single season.

The adult remain in the ocean upto a ripe old age of 3,4 or 5 years

unless they die earlier of predation or diseases.

In the life cycle:

Phase Begins at Duration Mode of life Habitat

Embryo Fertilization 12 hours Planktonic Outer littoral

zone

Larvae Hatching 20 days Planktonic Outer / inner

littoral zone

Juvenile Completion of gill

system

15 days Benthic Estuary

Sub-adult Complement of

sexual

maturation first

copulation

4-5 months Benthic Outer / inner

littoral zone

Adult Completion of

sexual

maturation

10 months Benthic Outer littoral

zone (20-70 m

depth)

Coastal / estuarine / brackish water (05-25 ‰)

Oceanic waters (25-35 ‰))

Post larvae ← Post larvae ← Mysis ← Zoea

↓ ↑

Juvenile

↓ Nauplii

↑

Adolescent → Sub-adults → Adults → Egg / Embryo

Migration

Life cycle of Macrobrachium rosenbergii

Classification: Phylum: Arthropoda

Class: Crustacea

Order: Decapoda

Family: Palaemonidae

Genus: Macrobrachium

Species: Macrobrachium rosenbergii

Life history: There are four stages in the life of a fresh water prawn. Like as:

Egg→Larvae→Juvenile→Adult

From the age of 0-7 months, fast growing individuals are capable of

reproduction. A female prawn with gonad, copulate just after molting with a male

prawn leaving a hard shell.

During copulation the male deposit a gelatiness mass sparmetophore

and the under side of receive of the female, tectiscess her walking legs. The

female prawns release the egg a few hours to a few days after copulation. A fully

matured female of 50 gm can carry 50000-100000 eggs.

As the eggs are extruded from the gonophore, they are fertilized by

non-motile sperm. The fertilized eggs are then transferred to a breed chamber on

the underside of the abdominal appendage. Eggs are maturated for 21 days and

then hatch immediately after hatching the female can again release eggs. In

same case, a female can lay eggs twice a month.

The eggs of the prawn are slightly elliptical the larger eggs being 0.6-

0.7 mm in length. They are bright orange in colour.

During hatching the females drop down streams to the limits of

brackish water in estuaries and coastal marshes. Rapid movement of the female

pleopods dispenses the newly hatched larvae, which normally swim with their

heads down.

Even larvae hatch in freshwater; they will be needed survive if they are

put into brackish water within 2/3 days.

Larvae are Planktonic and develop in brackish water for 3 to 6 weeks.

After 25-30 days larvae met metamorphosis into PL.

PL can tolerate a wide range of salinity, but freshwater in their survival

habitat. And so, 2-3 weeks after metamorphosis, the PL move against the current

and so towards freshwater canals and rivers. All freshwater development takes

place in the in the river.

In the life cycle: Gonad → Copulation (hours-days) → Eggs

↓

Fertilized eggs

↓

Breeding chamber (21 days)

↓

Elliptical

↓

Adult ← Post larvae (25-30 days) ← Larvae (3-6 weeks) ← Hatch (2 / 3 days)

Life cycle of Lates calcarifer

Classification: Phylum: Chordata

Sub-phylum: Vertebrata

Class: Pisces

Sub-class: Teleostomi

Order: Percomorphi

Family: Centropomidae

Genus: Lates

Species: Lates calcarifer

Life history: Lates calcarifer (sea bass) spends most of its growing period (2-3

years) in fresh water bodies, such as rivers and lakes which are connected to the

sea.

It has a rapid growth rate, often attaining a size of 3-5 kg within 2-3

years. Adult fish (3-4 years) migrate towards the moth of the river from inland

waters into the sea where the salinity ranges between 30-32 ‰ for gonad

maturation and subsequent spawning.

The fish spawns according to the lunar cycle (usually at the on set of

the new moon or the full moon) during the late evening (1800-2000 hours)

usually in synchrony with the incoming tide.

This allows the eggs and the hatching to drift into estuaries. Here,

larval development takes place after which they migrate further upstream to

grow.

At present, it is not known whether the spent fish migrates upstream or

spends the rest of its life in the marine environment.

Smith (1965) noted that some fish spend their whole life in fresh water

environment where they grow to a length of 65 cm and 19.8 kg body weight.

Migrate downstream Egg drifting, Larval development

Migrate upstream

Figure: Migration pattern of Lates calcarifer

The gonads of such fish are usually undeveloped. In the marine

environment, sea bass attaining a length of 1.7 m have been recorded in the

Indo-Australia region.

Spawning ground

Salinity (30-32 ‰)

Nursery ground

Salinity (25-30 ‰) Coastline

Feeding ground

Brackish water / Fresh water bodies

Sub-phylum: Crustacea

Class: Copepoda Class: Cirripedia Class: Malacostraca

Ex- Copepods Ex- Barnacles

Sub-class: Stomatopoda Sub-class: Peracarida Sub-class: Eucarida

Ex- Mantis shrimp

Order: Amphipod Order: Isopoda

Ex-Grammarus Ex-Bopyrus

Order: Euphausiacea Order: Decapoda

Ex-Krill

Sub-order: Natantia (swimming) Sub-order: Reptantia (crawling)

Infra-order: Penaeidea Infra-order: Caridea

Ex- Prawns Ex- Shrimps

Infra-order: Astacura Infra-order: Palinura Infra-order: Brachyura Infra-order: Anomura

Ex- Clawed lobsters Ex- Spiny lobsters Ex- True crab Ex- Hermit crab