The reproductive biology of the barnacle, Chthamalus malayensis from Singapore and Malaysia shores'

1
The reproductive biology of the barnacle,
Chthamalus malayensis from Singapore and Malaysia
shores.

• Koh L. L., ORiordan R. M. and Lee W. J.
• Marine Biology Laboratory
• National University of Singapore

2
Introduction

• Barnacles belong to the Phylum Crustacea, Class
  Cirripedia.
• Found on most substrates immersed in seawater and
  brackish water.
• All barnacles have planktonic larval stages.
• Intertidal barnacles are hermaphrodites.
• Many species depend wholly on cross-fertilization.
  
• Self-fertilization may occur if barnacles are
  isolated.

3
About Chthamalus malayensis

• C. malayensis belongs to the Family Chthamalidae.
• Tropical species extending to subtropical waters.
• Occupies a wide band on rocks and other hard
  substrata at mid tidal levels.
• A mid-upper shore species, therefore settling
  stage must be tolerant to strong sunlight and
  high temperature.
• Upon settling on suitable substrate, they can
  start reproducing within the first year.

4
Chthamalus malayensis
5
Why study the reproductive biology of tropical
barnacles?

• Major fouling organism in tropical seas.
• Of great importance due to their high
  productivity, congregating habits and nature of
  settlement.
• Most studies on reproductive biology are done in
  temperate areas.
• Information on this aspect from tropical areas is
  depauperate.
• Useful to compare reproductive patterns of
  temperate and tropical barnacles using same
  experimental designs.
• Knowledge on reproduction is essential to
  understand their role in fouling and to devise
  control measures.

6
Factors affecting life cycle of barnacles

• Temperature
• Salinity
• Light and photoperiod
• Immersion/ emersion duration
• Food availability
• Shore height
• Wave action

7
Anatomy of the reproductive system of a barnacle
VS Vesiculae seminales
8
Materials and Methods

• Three shores were chosen for our study
• 1. St. Johns Island - southern Singapore
• 2. Tg. Pelanduk, Port Dickson - west coast of
  Peninsula
• Malaysia
• 3. Tg. Resang, Mersing - east coast of Peninsula
  
• Malaysia
• These 3 shores were chosen due to their different
  exposure to monsoons during different times of
  the year.

9
Location of Sites
Affected by Northeast monsoon from November to
February
Affected by Southwest monsoon from June to
September
Affected by Northeast monsoon from November to
February but to a lesser extent
10
Objectives

• To investigate if there are any trends in
  reproduction in Chthamalus malayensis at the
  three shores.
• To correlate any trends in reproduction with
  temperature and salinity changes.
• To investigate if there are any variations in
  embryo sizes among the three shores.
• To examine variations in embryo sizes among the
  different stages of development.

11
Materials and Methods

• 30 barnacles from each shore were collected
  monthly from Aug 2003 to Jan 2004.
• Each sample was preserved in a separate vial of
  95 alcohol.
• Barnacles collected must not be isolated from the
  rest of the population.
• Each barnacle collected must have rostro-carinal
  diameter (RCD) of more than 4 mm.

12
Materials and Methods

• Barnacles collected were dissected in the
  laboratory.
• Reproductive organs (ovaries, testes and
  vesiculae seminales) and embryos were staged.
• Presence of a penis was noted.
• RCD of each barnacle was measured.
• Length and breadth of 10 embryos from each
  brooding barnacle were also measured.

13
Stages of ovaries and embryos
14
Stages of testes and vesiculae seminales
15
Stages of ova
Stage 1
Stage 2
Stage 3
Stage 2
16
Stages of embryos
Stage 2
Stage 4, naupliar
17
Testes and Vesiculae Seminales
18

• RESULTS

19
Ovarian development of barnacles among the 3
shores from Sep 03 to Jan 04
20
Ovarian Development

• Ovaries were present in some of the barnacles
  throughout the 5 months.
• Port Dickson
• Highest in January 2004 (57)
• Mersing
• Highest in November (77) and December 2003 (73)
  highest among all the sites.
• Coincided with the Northeast monsoon.
• Decreased to 43 in January 2004.
• St. Johns Island
• Percentages of barnacles with ovaries ranged
  between 32 60 throughout the 5 months.

21
Embryo development of barnacles among the 3
shores from Sep 03 to Jan 04
22
Embryo development

• Port Dickson
• Highest in November (67) and December 2003
  (87).
• Decreased to 27 in January 2004.
• Mersing
• No barnacles brooded in October 2003.
• Remained low (14 - 33) throughout the rest of
  the months.
• St. Johns Island
• Brooding barnacles remained relatively consistent
  (55) from October to December 2003.
• At the 3 shores, most embryos were at Stage 2,
  with the exception of Dec 03 at Port Dickson
  where equal percentages of barnacles had Stage 2
  and Stage 4 embryos.

23
Testes development of barnacles among the 3
shores from Sep 03 to Jan 04
24
Testes Development

• Testes were present in some of the barnacles at
  all the 3 sites throughout the 5 months except
  for Sep and Dec 2003 at St. Johns Island.
• Port Dickson
• Highest in Jan 2004 (53)
• Mersing
• Highest in Nov 2003 (50)
• St. Johns Island
• Highest in Jan 2004 (63)
• Besides these peaks in testes development,
  percentages of barnacles with testes remained low
  at all 3 sites throughout the 5 months (0 33).
• Testes when present were mainly at Stage 1 of
  development.

25
Vesiculae seminales development of barnacles
among the 3 shores from Sep 03 to Jan 04
26
Vesiculae Seminales Development

• VS were present in most of the barnacles
  throughout the 5 months of study.
• They were present in high percentages (33 100)
  of barnacles.
• 100 of barnacles had VS in
• Port Dickson in Dec 03 and Jan 04
• Mersing in Dec 03
• St. Johns Island in Jan 04
• VS were mainly at Stage 1 or 2 of development.
• In each, a penis was always present.

27

• Rainfall was high in Mersing in Nov and Dec 2003
  (358 621mm) and Singapore (601mm) due to the
  Northeast monsoon.
• Ovarian development was highest in Mersing and
  St. Johns Island when there was high rainfall.
• Embryo development was highest in Port Dickson
  in Nov and Dec 2003 when rainfall was low(143
  -239mm).

28
Summary
Peaks in development of
29
Variations of embryo sizes among different shores
Stage 2 embryos

• Using non-parametric Kruskal-Wallis test and
  subsequently Mann-Whitney test, it was found that
  Stage 2 embryos from St. Johns Island and
  Mersing were significantly larger than embryos
  from Port Dickson.
• There was no significant difference between sizes
  of embryos from St. Johns Island and Mersing.

30
Variations of embryo sizes among different shores
Stage 4 embryos

• Using non-parametric Mann-Whitney test, it was
  found that Stage 4 embryos from Mersing were
  significantly larger than embryos from Port
  Dickson.
• As there were insufficient stage 4 embryos from
  St. Johns Island, no comparison could be made
  with this site.

31
Conclusion

• Interesting trends have been observed in the
  reproduction of C. malayensis at the three
  shores.
• However these trends represent only 1st 5 months
  of data (proposed period of study 14 months).
• Overall, there is a peak in development in
  reproductive organs and embryos between Nov 03
  and Jan 04.
• Male and female reproductive organs did not
  totally degenerate at any of the 5 months.
• This suggests that each population can produce
  broods when conditions are favourable

32
Conclusion

• Stage 2 embryos from Mersing and St. Johns
  Island were significantly larger than those from
  Port Dickson.
• Stage 4 embryos from Mersing were also larger
  than those from Port Dickson.

33
Ongoing Future Research

• Ongoing Projects
• Settlement and recruitment studies
• Photography of quadrats on a 3-monthly period
• Future Projects
• Growth and demography studies on Euraphia and
  Tetraclita.

34
Thank You!