February 18, 2007 at 8:13 am #6974
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.
February 18, 2007 at 8:25 am #69098dipjyotiParticipant
I don’t know whether these link will help you or not!
http://www.seafriends.org.nz/enviro/cru … htm#Helice
February 20, 2007 at 8:46 am #69188
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’
February 20, 2007 at 8:52 am #69190dipjyotiParticipant
First time you need the habitat info! Have you got that? Mud is also related to its habitat.
February 20, 2007 at 8:54 am #69191
no,but how to get habitat info?any websites?im struggling to find any useful habitat info.
February 20, 2007 at 9:15 am #69192
can anyone make some suggestions?im kinda stuck on this topic.
February 20, 2007 at 10:46 am #69197
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.
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.
February 20, 2007 at 10:49 am #69198
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.
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.
February 21, 2007 at 5:55 am #69241
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?
February 22, 2007 at 10:42 am #69295
can anyone give me some info on the web of how the different adaptations help with helice crassa with different light intensity and why?
February 23, 2007 at 4:02 am #69347
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 😉
February 23, 2007 at 11:00 am #69366
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?
February 25, 2007 at 5:22 am #69430
anyone can find out some info that i havent dicovered? this is an investigation i agree. but the fisrt part is to find out the basic info behind the ecological niche of the organism,so that u can form a hypothesis.
February 28, 2007 at 7:21 am #69558
this is my investigation processed so far.could anyone pro have a look at my investigation to see if anything needs improving?
titile page: the effect of light intensity on the distribution of helice crassa.
Introduction: the ecological niche of Helice crassa: Helice crassa belongs to biological class Malacostraca(1). The helice crassa studied were found at Tohuna Torea estuary at the end of Riddel Road.they were usually found under the mud covered by the sea water,in dark damp conditions.so that they are not exposed to high light intensity.because they are prone to dessication.many adaptation features help them reduce the effect of dessication.these include:
1.helice crassa tend to move close to the dark place but move away from the light area. Because high light intensity is often associated with large amount of heat. –biology individual animal study helice crassa: mud crab Mary Melrose department of education Auckland 1988
2. Large pincers-this helps scoop up mud so that they can burrow to shelter from searing heat which is associated with high light intensity. the behaviour of two estuarine crab species by C.G..BEER, department of zoology,university of otago,new Zealand.(received by editior,April 15,1958)
3. the impermeable exoskeleton,strengthened with calcium carbonate,protects the crab from desiccation in air.
http://www.seafriends.org.nz/enviro/cru … htm#Helice
living under the mud often covered by the sea means cooler temperature,damp condition,low light intensity,im going to investigation the preferred light intensity of helice crassa which is the best light intensity which helps reduce the effect of dessication.
Aim: the purpose of this experiment is to find out wether or not the number of helice crassa burrowing into the mud changes with increasing light intensity.
Hypothesis: the number of helice crassa burrowing into the mud increases with increasing light intensity.
(reason:high light intensity is often associated with a large amount of heat, if an increasing number of helice crassa burrowing into the mud is found,then high light intensity would have an effect of the amount of dessication)
Null hypothesis: the number of helice crassa burrowing into the mud remains the same with increasing light intensity
(Reason: if high light intensity has no effect on the amount of desiccation then helice crassa will not show any responses to the increasing light intensity)
Equipment: 30 helice crassa.
3 ice cream containers
Paper to mark
Mud-6 cm deep(the same percentage of mud as well as sand)
Method: 1.go down the riddel road to collect 30 helice crassa.
2. Put mud (6 cm deep) into each ice cream container, the percentage of mud and sand remains constant in each ice cream container.
3.seperate 30 helice crassa into three groups with each group(10) put into each ice cream container.
3.cover the first ice cream container with a piece of wipe,then cover the second ice cream container with 2 pieces of wipe then the third ice cream container with 3 pieces of wipe.
4.measure the light intensity in each of the ice cream container.record light intensity in a table
5.after 5 minutes covered by the wipe, uncover it to count the number of helice crassa that has burrowed into the mud.
6.record the number of helice crassa burrowed into the mud against different light intensity.
March 2, 2007 at 2:19 am #69587
can any experts have a look at the plan i have so far?
March 27, 2007 at 3:30 am #70563vizzeeParticipant
im doing the effects of water content on the H. crassa, can somone gimme pointers on how to criticise my experiment? and any direct info regarding the relationship between water amounts and the crab itself
March 27, 2007 at 3:58 am #70565
who are u? (from GC)?
March 28, 2007 at 11:10 am #70614
u need to tell me who u are,what ur question is about,so that i can help u out.
March 29, 2007 at 8:23 am #70650arianParticipant
according to the experiment with Helice crassa is looks well to me and the details too. you have te record all the changes and their etiology (crab’s) and alos i think you have to read some more materials about physiology of crabs becsase they are different from other arthropods because the the chitina that they have allover their body. They stay in dark areas because they insticts sent them for protection.
I hope that i give an understanable answer.
March 24, 2008 at 4:00 am #83011karoleParticipant
Hi, I’m Karole, and I want to know what you mean by helice crassa is ‘different from other arthropods because of the chitina’.
What is chitina? Do you mean chitin? And even so, don’t all arthropods have it?
Also, is having chitin all over the body mean that the mud crabs have exoskeleton all over their body?
Is it a physiological adaptation? I’m looking for any physiological adaptations of helice crassa that reduces desiccation. By the way, I’m doing this research assignment for water content of the mud that helice crassa lives in.
July 27, 2008 at 4:54 am #85207pirategrl01Participant
im doing my research on the effects (on the weight of the helice crassa) of different salinities. i have searched everywhere but i cant find any general knowledge about the helice crassa and any adaptations of the crab related to the range of salinities and how it effects their weight, to help introduce my investigation. Any suggestions?
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