the presentation deals in detail the taxonomic aspects,the general behaviour and livelihood,centolecithal eggs, developmental aspects, the anatomical parts of the body,spawning activity, male organ called claspers, the developmental stages which include the granulation and degranulation stage, nuclei formation, germ disc formation, germ disc expansion, the limb bud stage followed by the embryonic moult stages, special reference to the trilobate larvae

1. Presented by,
AKHILA S
BFSc 2014 batch
Kerala University of Fisheries and Ocean Studies

2.  Kingdom Animalia
 Phylum Arthropoda
 Subphylum Chelicerata
 Class Merostomata
 Order Xiphosura
 Family Limulidae

3.  Live primarily in and around shallow ocean
waters on soft sandy or muddy bottoms
 Life cycle similar to other arthropods
 Nesting occurs high on the beach- exposure
to air or sunlight is stressful and damaging –
gulls also attack

4. Nesting of horse shoe crabs

5.  Produce centrolecithal eggs = densely
packed yolk surrounded by a peripheral layer
of egg protoplasm

7.  Come ashore as amplexed mated pairs
 Mainly occurs during night
 Mated pairs surrounded by multiple
satellite males that milt as female
deposits the eggs

8. © ERDG. Illustration by George Yurgin

9. Claspers on first pedipalp

10.  Eggs released from gonopores are fertilised
by sperm released from amplexed and
satellite males
 Extruded eggs shaped by female in discrete
clutches and deposited at depths of 15cm.

12. UNFERTILSED EGGS- STAGE 0
 Greenish blue or greenish grey(some are
pink)

13.  1.6-1.8mm diameter
 Eggs when released from the genital
operculum may be slightly dented and is
coated with an adhesive material that cause
it to stick to other eggs and sand grains
 Have large volume of yolk, surrounded by a
tough outer chorion with many pits

14.  Flagellated sperms attach to the chorion in
two stages
 Initial attachment of the apical tip of the sperm
head to the chorion
 Acrosomal reaction and penetration of sperm
acrosomal filament
 No predetermined site of sperm entry or
micropile

15.  The changes that occur during this phase are
not easily discerned due to the density and
pigmentation of the yolk
 Eggs undergo superficial cleavage
 The germ disc formation begins as a
triangular shape inundation at stage 7 and
gradually increases as embryo develops

16.  Germ disc continues to expand – visible as
slightly uplifted area when embryo is viewed
laterally
 By stages 11 and 12, bands or furrows appear
within the germ disc,that give rise to
prosomatic appendages(walking legs and
chelicera)

17.  Rudimentary prosomatic appendages
 Difficult to distinguish from early embryonic
stages as color and diameter virtually
identical
Stage 15 embryo(limb bud)

18.  Limb buds become noticably pointed at their
tip
 Chelicerae becoing more distinct
 Segmentation of the hepatopancreas evident
 Blood cells or amoebocytes produced at this
stage

19.  Tip of limb buds develop a biramous claw
like shape
 Lateral organs become prominent
 Segmentation along dorsal surface becomes
evident
 Embryo continues to flatten

20.  Opaque chorion splits
Just after the rupture
Of the chorion

21.  Embryo can be seen with unaided eye
 Embryo actively rotates within clear egg
membrane
 Prosomatic appendages become fully segmented
 Book gills develop rapidly
 Lateral eyes(compound) and median ocelli
visible
FOURTH EMBRYONIC MOULT- STAGE 21
 This moult also occurs within egg membrane

22. Compound eye

23.  Results in first instar or trilobate larval stage
 Book gills become larger
 Animal move rapidly
 Greatly resembles adult
 But lacks telson
Trilobate larvae

24.  Briefly remain planktonic before they settle
to the benthos
 After moulting to the second instar stage,
telson is formed
 After many moults, reach the forth instar
Second instar

25.  Spend their first and second summer on
intertidal flats, usually near breeding
beaches

26.  99% of juveniles are found in areas of salinity
greater than 5ppt
Juvenile hoorseshoe crabs

27.  Moult 16 to17 times over a period of 9 to
11 years before they are fully grown and
mature
 After attaining sexual maturity, they no
longer moult

30.  Eggs and larvae are preyed upon by large
invertebrates(sand shrimp, blue crabs),
fishes(perches) and shore birds
 Bacterial infection may affect individual
horse shoe crabs by erosion of the carapace
 The larvae can survive in the sediments for
many months until hatching conditions are
favourable

32.  Developmental ecology of the American horseshoe
crab Limulus polyphemus- L. BOTTON, Department
of Natural Sciences, Fordham University, New York,
NY 10023, USA; Richard A. TANKERSLEY, Department
of Biological Sciences, Florida Institute of Technology,
Melbourne, FL 32901, USA ;
 Biology and Conservation of Horseshoe
Crabs,edited by John T. Tanacredi, Mark L. Botton,
David Smith,pg:151
 Website of ERDG(The Ecological Research &
Development Group (ERDG), founded in 1995, is a
501(c)3 non-profit wildlife conservation organization
whose primary focus is the conservation of the
world's four horseshoe crab species)
 Wild screen arkive(ARKive is a not-for-profit
initiative of the charity Wildscreen