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URGENT RESEARCH NEEDS

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URGENT RESEARCH NEEDS

Postby chenwithasterisk » Sun Feb 18, 2007 8:13 am

hi:
my school is doing a research on helice crassa(mud crab). i cant find any info on the habitat of it.e.g. temperature,salinity,humidity of substrate,soil type,exposure. can anyone find this sorta info on the website?
i would really appreciate this :)

ps. pliz dont put wikipedia that site on, i already seen it many times.


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Postby dipjyoti » Sun Feb 18, 2007 8:25 am

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Postby chenwithasterisk » Tue Feb 20, 2007 8:46 am

hi:
my hypothesis is 'the effect of mud content on the distribution of the mudcrabs.'

can anyone provide some info (preferrably online journals on this aspect i.e. why mudcrabs prefer mud rather than the sand'

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Postby dipjyoti » Tue Feb 20, 2007 8:52 am

First time you need the habitat info! Have you got that? Mud is also related to its habitat.
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Postby chenwithasterisk » Tue Feb 20, 2007 8:54 am

no,but how to get habitat info?any websites?im struggling to find any useful habitat info.

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Postby chenwithasterisk » Tue Feb 20, 2007 9:15 am

can anyone make some suggestions?im kinda stuck on this topic.


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Postby Dr.Stein » Tue Feb 20, 2007 10:46 am

J. exp. mar. Biol. Ecol. 56: 49–62.

Habitat preferences of two estuarine burrowing crabs Helice crassa Dana (Grapsidae) and Macrophthalmus hirtipes (Jacquinot) (Ocypodidae)

M. B. Jones and M. J. Simons

Department of Zoology, University of Canterbury, Christchurch 1, New Zealand


Available online 1 April 2003.


Abstract

The horizontal and vertical distributions of two species of endemic, burrowing mud crabs Helice crassa Dana 1851 (Grapsidae) and Macrophthalmus hirtipes (Jacquinot 1853) (Ocypodidae) are described for the Avon-Heathcote Estuary (43°33′S: 172°44′E), Christchurch, New Zealand. Substratum preference is shown to be the most important factor influencing mud crab distribution, but lack of tolerance to salinities below 4‰ is also a significant factor preventing M. hirtipes from occurring at points close to freshwater input. Both species had similar sediment organic content and particle size requirements. Helice crassa was concentrated in well-drained, compacted sediments above mid-tide level, whilst Macrophthalmus hirtipeswas found in waterlogged areas below mid-tide level. This vertical separation is shown not to be caused by differential desiccation tolerances, but by feeding and burrowing adaptations related to these different substrata.

:)
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Postby Dr.Stein » Tue Feb 20, 2007 10:49 am

J. exp. mar. Biol. Ecol. 52: 271–278.

Effect of temperature, season, and stage of life cycle on salinity tolerance of the estuarine crab Helice crassa Dana (Grapsidae)

M. B. Jones

Department of Zoology, University of Canterbury, Christchurch I, New Zealand


Available online 1 April 2003.


Abstract

Survival of juvenile and mature specimens of Helice crassa Dana 1851 (Brachyura: Grapsidae) collected during summer, and of mature crabs collected in winter was measured at various salinity and temperature combinations. Summer crabs were euryhaline and eurythermal, and had low mortality after 7 days in salinities of 3.5–52.5%. at temperatures of 5–30 °C. Mortality was high in all salinities at 35°C and at all temperatures in 0.35%., however, juveniles had longer times to 50% mortality than mature crabs in 0.35%. at temperatures from 10–20 °C. Mature crabs had significantly better survival (P < 0.05) in 52.5%. at 5, 10, and 30 °C than juveniles. Juveniles showed widest salinity tolerance at temperatures closest to field temperatures at time of collection; lower and higher temperatures reduced the salinity range in which maximum survival was possible. No consistent effect of temperature on salinity tolerance of mature crabs was apparent. Winter crabs had significantly higher survival (P < 0.05) in 0.35 %. at the three temperatures tested (5, 10, and 20 °C) compared with summer crabs.

The salinity tolerance of stage 1 zoeae released from ovigerous female H. crassa maintained in the laboratory was investigated at 20 °C. Larvae were stenohaline, and had 100% mortality within 1 hour's exposure to salinities of 3.5–10.5 %., and within 24 h in 14%.; there was no mortality in 35%. until after 48 h.

Combination of wide salinity—temperature tolerances, seasonal acclimatization giving enhanced survival in dilute salinity during winter, and the refuge of a burrow during extreme physico-chemical conditions allows the benthic stages of H. crassa to occupy the most dilute regions of an estuary. In these latter areas, concentration of the vertical distributions of ovigerous females to highest shore levels ensures that larvae are released into salinities within their limited tolerance range.

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Postby chenwithasterisk » Wed Feb 21, 2007 5:55 am

hi:
thanks so much for providing evaluble info.however,my group decides to do 'the effect of light intensity'.so can anyone find info on this aspect?


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Postby chenwithasterisk » Thu Feb 22, 2007 10:42 am

can anyone give me some info on the web of how the different adaptations help with helice crassa with different light intensity and why?


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Postby Dr.Stein » Fri Feb 23, 2007 4:02 am

If we gave you the info you need regarding your exact topic, what will you and the group do? ;) I mean you are going to investigate the effect of light to Helice. So, assume that you don't know at all and want to study it. Create hypothesis. If you already know the effect (why and how), the experiment will not interesting anymore. That's how Scientifical Method works ;)
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Postby chenwithasterisk » Fri Feb 23, 2007 11:00 am

hi:
we need basic info regarding the ecological niche behind the species. wat i found out so far,is that high light intensity is often associated with heat.helice crassa likes shadowness because they need to prevent themselves from dessication.

any more effects i need to consider?

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