|
The shark that is to be introduced is very particular: the back has a yellowish coloration as the peel of a lemon, from which his name derives and he is the more studied shark in the whole shark's world. This has allowed to clarify not only the biology of the lemon shark but big part of all the knowledge about these fishes. The lemon shark has really a curious coloration, the back is brown-yellowish, while the abdomen clear. The motive for this unusual physical aspect is in the habits of the animal, that it often next to sandy and muddy backdrops, lagoons and inlets with forests of mangroves, environments where the yellowish coloration is prevailing and therefore a mimicry of this type practically makes invisible the lemon shark bewaring from the surface toward the sea backdrop.
The face is short and stumpy,
the maximum length is of 300 cm, middly among 220-280 cm. The dorsal
fins are two and are of similar dimensions, the anal fin is enough
great. The teeth are sharp, smooth, without side cusps, similar in the
two jaws. The eyes are of middle dimensions even if the sight would not
result particularly acute, perhaps because of the waters in which it
swims.
This shark results to be more
active during the crepuscular and nighttime hours and he can stir
solitary or in groups that reach 20 samples. As other kind is able to be
immovable on the fund, into a "sleeping" condition, but this state of
numbness doesn't have to deceive the curious scuba diver or the
skin-diver that, in case of noise would be found to a vehement and
dangerous reaction of the animal. (Note1: sharks respiraton)
The adults have not a
particularly vast area of movement, even if have been recorded
migrations of small-medium populations.
The reproduction is
viviparous
with placenta and date the facility of observation and study, through
the analysis of the vital cycle of the lemon shark have many biological
and ecological aspects of these fishes have been clarified. There are
numerous video on the birth of females of lemon shark, which move in
protected waters, a little deep lagoons or bays with forests of
mangroves, to give birth since 4 to 17, after a 10-12 month-old long
pregnancy.
Curiosity1: Mr. Samuel Gruber, ftom university in Miami, studies the lemon sharks from 1967, in particular way the population around the island of Bimini, in the Bahamas, where the Gruber's Bimini Biological field station is found. Curiosity2: The lemon shark Negaprion brevirostris, described here, is very similar to the lemon shark sickle Negaprion acutidens, that has a less stumpy face, pectoral fins more falcades and teeth most sharp and narrow. The distribution of the Negaprion acutidens is completely different (Indian Ocean) and greater is also the aggressiveness.
Note1: recommended reading: sharks respiration Note2: the remora is a fish whose first dorsal fin is turned into an adhesive disk that is used for sticking to great objects in movement (boats, sharks, turtle..) Note3: sharks reproduction: Around the 30% of the sharks has a oviparous reproduction, that is when the female deposes outside the eggs; around 50% has a aplacental viviparous reproduction, that is when the female produces the eggs that develope inside her body and the small sharks go outside completely formed; the remained 20% has a placental viviparous reproduction, that is when the embryo is in contact with her mother through a primitive placenta.
Bibliography: "Sharks & Rays, Elasmobranch Guide Of The World". Ralf M. Hennemann, "Sharks of the world", Leonard Compagno, M. Dando, S. Fowler,
Marco Angelozzi - www.prionace.it
|
|
.jpg)
.jpg)
.jpg)
.jpg)
