How do the sweepers perform so well?

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How do the sweepers perform so well?
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The Sweepers

• Nassarius festivus
• Habitat Sandy shore
• - Intertidal zone
• Scavengeous
• Feed on carrion
• By chemical sensation
• Epifauna
• Burrow in sand for most of the time

• Kingdom Animalia
• Phylum Mollusca
• Class Gastropoda
• Family Nassariidae
• Genus Nassarius
• Species Festivus (Powys, 1835)
• Classification of Nassarius festivus

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• Nassarius festivus

• Factors affecting successful arrival at food
• Insufficiency of carrion brought onshore
• Low concentration of food fragment
• Slow locomotion

• Our focus
• Its adaptations to the environment based on its
  feeding behaviour
• Strength of chemical sensation
• Distribution on the sandy shore
• Burrowing habit

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Materials and methods- Study site Starfish Bay

• A sheltered sandy shore
• Far from residential area and factories

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Materials and methods- Methodology

• Chemical Sensation
• a. Concentration of chemicals
• - Ground clam solution in agar blocks
• - 0.05 g/ml 0.0015625 g/ml
• - In a circular basin with radius 10 cm

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Chemical sensation - Results
Mean arrival time (s)
Concentration of clam solution in agar block
(gml-1)
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Materials and methods- Methodology

• b. Distance
• Carrion bait fixed at different regions
• Recorded at every 5-minute interval
• Numbers of individuals of N. festivus arrived at
  the bait
• Water depth

Leiognathus brevirostris fixed on the shore
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Chemical sensation - Results
Trial 2
Trial 1
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Chemical sensation - Results

• All resemble a sigmoid curve
• Longest time taken 60 min
• Velocity of locomotion 1 cm/ 7s
• 5.14 mhr-1
• ? Maximum distance 5.14 m

Initial water depth 3.5cm
Trial 4
Trial 3

• No N. festivus recorded in the first five minutes
  in trial 1
• Large deviation between eventual sizes in trials
  1 and 4 and trials 2 and 3

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Materials and methods- Methodology

• Distribution on the shore
• A 50 m transect drawn across the zones
• 2 quadrats at regular intervals of 5 m

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Distribution on the shore - Results
The distribution of N. festivus
Mean No. of individuals of N. festivus
Lower zone
Upper zone
Marks on the transect line (m)
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Materials and methods- Methodology

• Depth of burrowing
• Cotton threads (rlt0.5 mm) attached to their
  shells
• Distances they burrowed measured by the length of
  threads pulled into the sand

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Burrowing Habit - Results and discussion

• All record 0 mm
• They shook their ventral feet to burrow a little
• Often aided by wave actions

• Reactivated on the addition of carrion bait
• They remain superficial beneath the shore in
  order to
• Have swift sensation and movement
• Breathe

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Conclusion

• Well adapted in several ways
• Strong and sensitive chemical sensation
• Swift response
• Dwell in the lower part of the intertidal zone
• Burrow but remain superficial

Immaculate Heart of Mary College
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Thanks for your attention
Immaculate Heart of Mary College Members Lam Sze
Yuen Au Sze Wing Chan Chun Tung Lam Hiu
Tung Chan Ivy