I don’t know whether these link will help you or not!
http://www.int-res.com/abstracts/meps/v234/p23-42/
http://www.int-res.com/abstracts/meps/v182/
http://www.seafriends.org.nz/enviro/cru … htm#Helice
http://www.niwascience.co.nz/pubs/wa/12-1/habitat

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Attachments:

First time you need the habitat info! Have you got that? Mud is also related to its habitat.

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.

🙂

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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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 😉

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

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.

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.

hey
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?