1) Mud crabs undergo a complex life cycle beginning as larvae called zoea, which go through five zoeal stages and one megalopal stage before metamorphosing into juvenile crabs. 2) As juveniles, they migrate to estuaries where they mature over 18-24 months. Mature males and females mate, after which the females migrate offshore to spawn millions of eggs. 3) The eggs hatch into zoea larvae, restarting the cycle, with spawning occurring year-round in the tropics and during late spring to mid-autumn in subtropical and warm temperate areas.

1. LIFE CYCLE OF MUD CRAB
Presented by
IPSITA SAHOO
Reg. No - 200705180160
Guided by
Dr. SITARAM SWAIN
Assistant Professor, School of Applied Sciences
Centurion University of Technology and Management,
Bhubaneswar, Odisha

2. Review Literature
METHODOLOGY
Introduction
Examples of Mud crap
Types of Mud crabs
Life cycle of mud crab
References
Presentation
Outline
Conclusion

3.  Crabs of the genus Scylla are commonly known as mud
crabs or mangrove crabs. They are found in intertidal and
sub-tidal zones of estuaries and in mangrove systems in
tropical to warm temperate zones of the Pacific and Indian
oceans.
 Mud crabs have a complex life cycle, where the larvae go
through five zoeal stages (3-5 days each) and one megalopal
stage (8-10 days) before finally metamorphosing into the
benthic first juvenile crab stage.
INTRODUCTION
Image source- http://advancefishery.com/crab/

4. Examples of Mud crap
Image source- Keenan, C., Davie, P. J., & Mann, D. L. (1998).

5. Types of Mud crabs
Mud crabs in the genus Scylla inhabit coastal areas, estuaries and backwaters.
i. Larger species :
The larger species is locally known as `green mud crab'.
It grows to a maximum size of 22 cm carapace width and 2 kg in weight.
These are free living and distinguished by the polygonal markings present on all
appendages.
ii. Smaller species :
The smaller species is known as `red claw'.
This grows to a maximum size of 12.7 cm carapace width and 1.2 kg in weight.
It is without polygonal markings and has a burrowing habit.
Both species have good demand in the domestic as well as in the foreign market.

6. Life cycle of
mud crab

8. ZOEA
 A mud crab begins life as a larva called a ‘zoea’, which hatches from an egg. It is about one
millimetre long with undeveloped limbs and looks a little like a tadpole. The zoea floats in the water
with plankton – microscopic organisms that drift in clusters.
 The zoea larva undergoes 5 successive moults to become the megalopa larva. Thus there are 5
zoeal stages. For each moult, it takes 3-4 days.
Image source- http://ecoursesonline.iasri.res.in/mod/page/view.php?id=51482

9. MEGALOPA
 A zoea grows by ‘moulting’ (shedding its shell) four times over 12 to
15 days.
 During the fifth moult, it transforms into a ‘megalopa’, which has
functional claws. After a week or so, it moves inshore and settles to the
seabed.
 After a few days, it moults into a stage one juvenile crab.
Important morphological characters
 Carapace longer than wider; abdomen with 5 pairs of pleopods ; a
pair of cheliped; 4 pairs of legs.
Image source- http://ecoursesonline.iasri.res.in/mod/page/view.php?id=51482

10. JUVENILE CRAB & YOUNG ADULT
 A miniature version of the adult, it is about 4 mm
wide.
About a month after hatching, when 10 – 20 mm
wide, it moves to an estuary and settles in a sheltered
area.
Juvenile Crab
 The crab reaches sexual maturity at 18 to 24 months. A
green mud crab matures at about 110 millimetres
(carapace width) and a brown at about 90 millimetres.
Juvenile Crab
Young adult
Image source- http://ecoursesonline.iasri.res.in/mod/page/view.php?id=51482

11. Mating
 In the warmer months, mature females release a ‘pheromone’
(chemical attractant) into the water to attract males.
 Once paired, the male climbs on top of the female, clasps her
with his hind legs, picks her up and carries her around for up to
four days.
 He releases her when she begins to moult, and after she has
shed her shell, he turns her upside down to mate.
 He deposits a capsule of sperm inside her reproductive
opening, where it’s stored for months until her developing ‘ova’
(eggs) are ready to be fertilised.
 After mating, the male flips the female upright and holds her
under him for a few more days while her shell hardens.
Precopulatory caging
Male guarding over newly
molted female prior to
copulation
Male flipping female over,
with female’s abdomen
readily opened
Copulation between male
and female
Insertion of male’s
gonopods into female’s
gonopores Postcopulatory guarding
Image source- https://doi.org/10.1016/j.aqrep.2015.08.004

12. Spawning and hatching
 The female migrates offshore to spawn.
 The fertilized eggs are released in
batches of two to five million.
After digging a hole in the sand or mud
with her abdominal flap, the female
releases her eggs into it.
Using her swimming legs, she gathers the
eggs up to carry them under her abdomen.
 The eggs hatch in two to four weeks.
The lifecycle then begins again.
Image source- https://doi.org/10.1093/icesjms/fst181
Life cycle of S. serrata showing ontogenetic shift
between the inshore (estuarine) and the offshore
(oceanic)

13.  Mud crabs are highly fecund: a female can produce several million eggs per spawning and
can spawn multiple times per year.
 In the tropics, spawning of mud crabs occurs year round, but in subtropical and warm
temperate areas, spawning is restricted to late spring to mid-autumn.
 An understanding of ontogenetic changes in digestive physiology and feeding behaviour of
various larvae stages is important for the development of an appropriate hatchery protocol and
the design of formulated feeds for crab larvae.
CONCLUSION

14.  Fushimi, H., & Watanabe, S. (1999). Problems in species identification of the mud crab genus
Scylla (Brachyura: Portunidae). UJNR Tech Rep, 28, 9-13.
 Australia, W. (2013). Mud Crab.
 Phelan, M., & Grubert, M. (2007). The life cycle of the mud crab. Fishnote No. 11, Department
of Primary Industry. Fisheries and Mines, Darwin, Australia.
 Australia, W. (2020). Resource Assessment Report.
 Keenan, C., Davie, P. J., & Mann, D. L. (1998). A revision of the genus Scylla de Haan, 1833
(Crustacea: Decapoda: Brachyura: portunidae). The Raffles Bulletin of Zoology, 46, 217-245.
 Websites: http://www.fish.wa.gov.au/species/mud-
crabs/pages/default.aspx#:~:text=Lifecycle,over%2012%20to%2015%20days.
 http://advancefishery.com/crab/
REFERENCES