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Stop...all are mine....
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| [Note Guidelines] Photographer's Note |
Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (Greek: βραχύ/brachy = short, ουρά/οura = tail), or where the reduced abdomen is entirely hidden under the thorax. They are generally covered with a thick exoskeleton, and armed with a single pair of chelae (claws). 6,793 species are known. Crabs are found in all of the world's oceans. Additionally, there are also many freshwater and terrestrial crabs, particularly in tropical regions. Crabs vary in size from the pea crab, only a few millimetres wide, to the Japanese spider crab, with a leg span of up to 4 m.
The infraorder Brachyura contains about 93 families , as many as the remainder of the Decapoda. The evolution of crabs is characterised by an increasing robustness of the body, and a reduction in the abdomen. Although many other groups have also undergone similar processes of carcinisation, it is most advanced in crabs. The telson is no longer functional in crabs, and the uropods are absent, having probably evolved into small devices for holding the reduced abdomen tight against the sternum.
In most decapods, the gonopores (sexual openings) are found on the legs. However, since crabs use the first two pairs of pleopods (abdominal appendages) for sperm transfer, this arrangement has changed. As the male abdomen evolved into a narrower shape, the gonopores have moved towards the midline, away from the legs, and onto the sternum. A similar change occurred, independently, with the female gonopores. The movement of the female gonopore to the sternum defines the clade Eubrachyura, and the later change in the position of the male gonopore defines the Thoracotremata. It is still a subject of debate whether those crabs where the female, but not male, gonopores are situated on the sternum form a monophyletic group.
The earliest unambiguous crab fossils date from the Jurassic, although the Carboniferous Imocaris, known only from its carapace is thought to be a primitive crab. The radiation of crabs in the Cretaceous and afterwards may be linked either to the break-up of Gondwana or to the concurrent radiation of bony fish, the main predators of crabs.
About 850 species of crab are freshwater or (semi-)terrestrial species; they are found throughout the world's tropical and semi-tropical regions. They were previously thought to be a closely related group, but are now believed to represent at least two distinct lineages, one in the Old World and one in the New World. |
valy67, thor68, uleko has marked this note useful
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- valy67
![Gold Star Critiquer/Gold Star Workshop Editor/Gold Note Writer [C: 1880 W: 59 N: 2915]](http://i1.treknature.com/misc/g-g-g.gif)
(8733) - [2009-07-08 2:50]
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Hello Horia !
I have seen many crabs during my holiday, but I didn't get any good shot - you were much better than me, as this picture is simply outstanding. The details on the crab are excellent, and I also like the very natural colors, the composition, the POV and the pose of the crab who seems to be protecting his preys from any stealer. Very well done !
Valérie.
Ciao Horia, interesting capture of superb beautiful crab with its preys, wonderful natural colors, good details and excellent sharpness, very well done, ciao Silvio
ho Horia,
Excellent photo, drawing the frame tatural, has achieved a balanced and pleasant composition. I like the focus point in the crab with variations in the secondary level elements. Excellent optical adjustment to a very good result.
Thanks for the note attached, which seems to interest me on this animal.
Good job. Thanks for sharing!
Jesús
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- thor68
(5642)
- [2009-07-08 11:18]
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what a greedy crab! *g* i would not like to stick my hand in that hole. great capture of the pretty crab in its "home",
love the datails, especially the patterns and color of the body. well done & best wishes, thor.
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- uleko
(2769)
- [2009-07-09 1:03]
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Hello Horia,
A really great capture of this Crab guarding its hole! Excellent focus showing sharp details and natural colours. I like the framing too. Very well done!
TFS and regards, Ulla
Hi Horia
It is also Pachygrapsus marmoratus. I like the POV and funny moment with shels of Mytilus edulis Crabs are rarely presented on TN Thank you for the interesting contribution
TFS
Krzysztof
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- rommel
![Gold Star Critiquer/Silver Note Writer [C: 86 W: 0 N: 49]](http://i1.treknature.com/misc/g-n-s.gif)
(849) - [2009-11-08 1:53]
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Hallow Horia,
Greatr exposure and sharp image showing some interesting details in this little crabs cave.Very natural photo, well done.
erwin...
![Gold Star Critiquer [C: 152 W: 1 N: 0]](http://i1.treknature.com/misc/g-n-n.gif)
(565)![Gold Star Critiquer/Silver Workshop Editor/Gold Note Writer [C: 461 W: 17 N: 945]](http://i1.treknature.com/misc/g-s-g.gif)
(3512)
Superba poza.Pentru ca e foarte clara se pot vedea detaliile crabului.O seara buna. Alin.