sea cucumber , introduction , reproduction , life history , references

1. SEACUCUMBER
Submitted
by
Arya
udayan
2014-01-14
Life Cycle Of

2. INTRODUCTION
 HOLOTHURIANS , Commonly called
as sea slugs or Sea cucumbers is a
group of economically important
Echinoderms.
 World wide distribution
 About 1200 species are recorded ;;
Along indian coast HOLOTHURIA
SCABRA
( SAND FISH ) is predominant.

3.  Sea cucumbers consumed either fresh or
boiled or prepared as different delicacies.
 FAO Statistics indicate a downward trend in
world sea cucumber harvest through natura
fisheries;hence attempts have been made to
promote holothurian fisheries.

6. REPRODUCTION
 HOLOTHURIAN SCABRA attains a length of
400mm & weight of 500g.
 Lives on Sandy muddy bottom & sexually
mature
at 18 months.
 Size at first maturity is 210mm.
 Sexes are separate & there is no distinct
sexual dimorphism .
 It breed twice in an year; 1stspawning
season:march
to may & 2nd during October to December
 Gonadal development is distinguishable into 5
stages such as immature , resting , growing ,
mature & post spawning phases .

7.  During immature and resting stage ;
ovarian tubules are transparent , short &
thin distal end of tubules are club shaped .
During growing phase ;tubules are having
opaque spherical oocytes of 20 – 120
microns in diameter .
In mature phase ; tubules are swollen
containing ripe oocytes of 150-200 µ.
In post spawning phase ; some tubules are
seen as in mature stage , others are shorter
showing atresia , a few ripe oocytes are in
the tubules &signs of resorption / atresia
are seen.

8. 
In males ;
During immature & resting phase : testes
is hardly distinguishable from ovary .
During growing phase testis tubules
become more branched & whitish , length
& diameter also grow ,spermatids develop
inside the tubules .
During mature phase tubules grows larger
in size,more whitish with swelling &
spermatozoa are seen in tubules .
During post spawning phase ;tubules
appear evacuated with few spermatozoa
 Ripe testes are milky white whereas
ovaries are translucent .

9. life history
 Holothurians usually spawn in late afternoon or
evening or during night .
 During spawning , males release spermatozoa
first & then female releases the eggs.
 Males lift the anterior end and perform swaying
movements for sometime after which they start
releasing sperm & it continues for 1-2 hours.
 Ripe females,if present exhibit responsive behavior
 Anterior region of female gets bulged & eggs are
released through gonopore forcefully in a
continuous jet.

10.  The mass of eggs so released appear light yellow
and mucus like .
 Fertilization is external ; taking place in water.
 One adult female releases about 1million eggs .
 Eggs are spherical , about 180 to 200 µ in size.
 After fertilization ,first polar body appears
after 20-30minutes.
 First cleavage take place after 15 minutes.
 In 3 hours the blastula is fully formed .
 Gastrula is fully formed after 24 hours.
 The AURICULARIA LARVA hatches out after 48hours
 It grows to DOLIOLARIA larva within 10 days .
 Within 2 to 3 days it develops to PENTACULA stage
 They transform into JUVENILES within one month.

11. lifehistory

12. Auricularialarvae
 It is transparent ,pelagic and measures 560µ.
 It is slipper shaped & performs locomotion by
the movement of flagella of the ectodermal cells
that forms ridges or bands.
 The larva has a digestive tract consisting of
mouth , pharynx , stomach & anus.
 There are 3 coelomic sacs; Hydrocoel & right
and left somatocoel .
 Hydrocoel is connected to hydropore on the
dorsal side by means of a tubular canal .

13. Doliolarialarvae
 Doliolaria larvae is barrel shaped
measures more than 620 microns in
size.
 There is partial degeneration of
flagellated bands leaving short pieces
that joins to form 3 to 5 numbers of
flagellated rings.
 The hydrocoel encircles the foregut
;develops to 5 lobes which represents
the 1° 𝒕𝒆𝒏𝒕𝒂𝒄𝒍𝒆𝒔
 Immediately after ; sixth lobe is
developed which is called polian
vesicles.

14. Pentacula stage
 Pentacula stage is tubular & it creeps
over the sides and bottom.
 It measures 600-700 microns in size.
 It has five tentacles at the anterior
end & a single tube foot at the
posterior end which helps in its
locomotion.
 They feed on benthic algae and other
detritus matter.
 They transform into juveniles within
one month.

16. conclusion
Holothurians commonly called as sea
slugs or sea cucumbers.
H.scabra(sand fish) predominant in indian
coast
No sexual dimorphism & Breeds twice in
an year.
Fertilization is external.
Gastrula (after 24 hrs ) , Auricularia
larvae(48 hrs ) , doliolaria larvae( within 10
days) ,pentacula stage etc are the
development stages.

17. References
 Breeding & seed production of fin fish &
shell fish.[Dr.P.C.Thomas;;Page no : 270]
 Hand book of fisheries & aquaculture
.[page:590]
 Advances in sea cucumber aquaculture &
management ,issue 463,FAO
[Page no :270-280].
 Sea cucumbers [ Jody . S. Rake] [page :57]
Chapter : Hotspot of sea cucumber
fisheries
in India.