This week entry is about improvement of habitat for the crabs and knowledge gain from observation. Housing crab is important that they have a comfortable place to live in and so enhancement is done. The main focus of observations are the function, mechanism, geometry and anatomy of the legs. Crab’ s specialty is their leg that are tiny and seemingly fragile but it is able to support the whole body and gain great stability compare to other animals which usually have large surface area of support system.
The habitat for the crab was change from a smaller size aquarium to a big “house” after weeks of observation on the lifestyle of the crabs. One of the reason that improvement is done is that the crabs will have more space to explore and move around. As shown in the picture, the new house is 3 times bigger than previous one. Another benefits of this change is to avoid the crabs from fighting for food. As reported in previous post, one of the crab which loses its leg is weaker to fight for food. The new home has 2 separate food containers which are located far away from each other. Therefore, when the stronger crab is eating, the other one can have its own food without fighting.
At first, the crabs were separate from each other with different containers. However, the one in the white container escaped at night and fortunately it was found the next day in the toilet :) Therefore, the new arrange was made as what is descried above.
Leg Geometry
The crabs have four pairs of legs. The legs extend outward from the main-body/carapace rather than being located underneath it as when compared with mammals. This allows for more flexibility in movement. For instance, the crabs can move in two dimensional plane in all directions without having to orient its head to the direction of movement. While axial movement is possible, the legs configuration makes radial movement more favorable and easier. This is due to that the legs are extended in radial direction with respect to the main body.
Crabs belong to the phylum of arthropod. Generally, arthropod legs include several segments consisting of femur, tibia, and multiple tarsal segments [1]. Three main segments are very obvious in the crab legs. These three segment are connected through two joints. The joints allow the segments to rotate about each other. The human finger resembles to a good approximation the crab legs. The weight is distributed over the four pairs of legs. This distribution cancels off any moment and thus prevents the body from rotation about its main axial axes. The segments which come into contact with the ground are very sharp.
The sharp ends might be useful in climbing. It allows the crab to hold or grip on something to lift its body up. It may be hypothesized that the sharp ends result in a high pressure exerted by the crab weight on the ground. The high pressure is the result of the small area of contact between the sharp ends and the ground. This allows the crab to hold firm to its position.
Hair legs of Cardisoma Armatum
Setae or hair is one of the components of the leg of Cardisoma that cover its leg with hair. It is basically the nitrogen containing polysaccharide [2] . The main function of this hair is to help them to gather phytoplankton. Basically Phytoplankton are microscopic organisms that live in watery environment, so Cardisoma armatum captures these microscopic organisms and allows them to be eaten [3]. Another function of setae is that it works as chemosensory receptor to reserve senses from nervous system in the. Setae in legs are distributed equally trough other legs
The sharp ends might be useful in climbing. It allows the crab to hold or grip on something to lift its body up. It may be hypothesized that the sharp ends result in a high pressure exerted by the crab weight on the ground. The high pressure is the result of the small area of contact between the sharp ends and the ground. This allows the crab to hold firm to its position.
Hair legs of Cardisoma Armatum
Setae or hair is one of the components of the leg of Cardisoma that cover its leg with hair. It is basically the nitrogen containing polysaccharide [2] . The main function of this hair is to help them to gather phytoplankton. Basically Phytoplankton are microscopic organisms that live in watery environment, so Cardisoma armatum captures these microscopic organisms and allows them to be eaten [3]. Another function of setae is that it works as chemosensory receptor to reserve senses from nervous system in the. Setae in legs are distributed equally trough other legs
Function and Mechanism of Crab's Legs
Crab’s legs are in pairs alongside of the body. Crabs are decapods (10 legs) which including a claw-bearing pair with spines used for feeding and defense; followed by four pairs of sharply pointed walking legs for locomotion [4]. Some walking legs may be ada
Cardisoma armatum crab possess four pairs of walking legs. Swimming legs are not found on crab's body. Sometimes, claws also known as pincers or chelae.
Crab has a peculiar way of walking. Crabs are capable of walking forward or diagonally, but usually they walk sideways [6], pushing with the legs on one side of the body and pulling with those on the other [4]. Hence, people named this behavior the word crabwise. You can probably see that crab’s legs have two joints, one up near the crab’s body and another in the center of its leg. The joint that is up near the crab’s body can allow the crab to move forward but is restricted in a way that only allows a crab to move slowly in this direction [7]. Crabs move sideways much faster by flexing the second joint of each leg [8].
pted for swimming as their last pair of walking legs is flattened into swimming paddles [5]. Crabs utilized their two front legs as their claws. Cardisoma armatum crab possess four pairs of walking legs. Swimming legs are not found on crab's body. Sometimes, claws also known as pincers or chelae.
Crab has a peculiar way of walking. Crabs are capable of walking forward or diagonally, but usually they walk sideways [6], pushing with the legs on one side of the body and pulling with those on the other [4]. Hence, people named this behavior the word crabwise. You can probably see that crab’s legs have two joints, one up near the crab’s body and another in the center of its leg. The joint that is up near the crab’s body can allow the crab to move forward but is restricted in a way that only allows a crab to move slowly in this direction [7]. Crabs move sideways much faster by flexing the second joint of each leg [8].
References :
[1] (2001, 26 April 2014). Comparative Leg Anatomy. Available: http://ww w.oricomtec h.com/proje cts /leg-comp.htm
[2] (2012). What are Phytoplankton. Available at: http://earthobservatory.nasa.gov/Features/Phytoplankton
[3] (2014). Insect Hair. [online] Available at: http://www.microlabgallery.com/gallery/InsectHair535062.aspx
[4] National Museum of Ireland. (2014). Taxonomy Trail [Online]. Available:
http://www.museum.ie/en/exhibition/taxonomy-trail.aspx
[5] Judith S. Weis (2012). Walking Sideways: The Remarkable World of Crabs. Ithaca, NY: Cornell University Press. ISBN 978-0-8014-5050-1.OCLC 794640315
[6] Sally Sleinis & Gerald E. Silvey (1980). "Locomotion in a forward walking crab".Journal of Comparative Physiology A: Neuroethology, Sensory, Neural, and Behavioral Physiology 136 (4): 301–312. doi:10.1007/BF00657350
[7] Mya Kagan. (2013). Why Do Crabs Walk Sideways [Online]. Available:
http://www.whyzz.com/why-do-crabs-walk-sideways
[8] Luis Villazon. (2009, July 22). Why Do Crabs Walk Sideways [Online]. Available:
http://sciencefocus.com/qa/why-do-crabs-walk-sideways
[1] (2001, 26 April 2014). Comparative Leg Anatomy. Available: http://ww w.oricomtec h.com/proje cts /leg-comp.htm
[2] (2012). What are Phytoplankton. Available at: http://earthobservatory.nasa.gov/Features/Phytoplankton
[3] (2014). Insect Hair. [online] Available at: http://www.microlabgallery.com/gallery/InsectHair535062.aspx
[4] National Museum of Ireland. (2014). Taxonomy Trail [Online]. Available:
http://www.museum.ie/en/exhibition/taxonomy-trail.aspx
[5] Judith S. Weis (2012). Walking Sideways: The Remarkable World of Crabs. Ithaca, NY: Cornell University Press. ISBN 978-0-8014-5050-1.OCLC 794640315
[6] Sally Sleinis & Gerald E. Silvey (1980). "Locomotion in a forward walking crab".Journal of Comparative Physiology A: Neuroethology, Sensory, Neural, and Behavioral Physiology 136 (4): 301–312. doi:10.1007/BF00657350
[7] Mya Kagan. (2013). Why Do Crabs Walk Sideways [Online]. Available:
http://www.whyzz.com/why-do-crabs-walk-sideways
[8] Luis Villazon. (2009, July 22). Why Do Crabs Walk Sideways [Online]. Available:
http://sciencefocus.com/qa/why-do-crabs-walk-sideways