Astropecten mais laquelle ?

Roberto PILLON le 26/07/15

Les piquants sur la face latérale des plaques supramarginales est mieux le critère décrit dans la littérature:
 - Koehler, R. (1921). Faune de France. Echinodermes:- “Astropecten platyacanthus … …est caractérisée principalement par ses plaques marginales dorsales et ventrales munites de petits piques plus nombreux et plus forts que chez l’ Astropecten bispinosus typique. Les faces latéral vertical des marginales dorsales, au lieu d’être neus en leur milieu, portent d’assez nombreux petits piques …” (pag.47-48)
 - Tortonese Enrico (1965). Fauna d'Italia. Echinodermata:- “Astropecten bispinosus… …Piastre margino-dorsali strette e alte, con un’ampia zona nuda laterale e un robusto aculeo inserito sull’orlo superiore e interno.” (pag. 140)
- Tortonese Enrico (1965). Fauna d'Italia. Echinodermata:-“Astropecten platyacanthus… …Queste (piastre margino-dorsali) sono quasi completamente rivestite di aculei e squame e portano un aculeo, più o meno scostato dall’orlo superiore e interno.” (pag. 143)

Mais en plongée la meilleure façon est de regarder cette "petite surface nue", il est un de plus visible, plus constante (en effet, parfois dans quelques specimen de A.platyacanthus cette plaques peuvent sembler côté nu) et en outre, il est un auteur qui a également décrit cette différence:
Tortonese Enrico (1965). Fauna d'Italia. Echinodermata
"...(Astropecten bisinosus) Piastre margino-dorsali...con... un robusto aculeo inserito sull'orlo superiore e interno." (pag.140)
"...(Astropecten platyacanthus) ...piastre parginp-dorsali... portano un aforte aculeo, più o meno scostato dall'orlo superiore e interno. (pag. 142)

Sylvain LE BRIS le 26/07/15

Bonjour Roberto,
Merci pour ces précisions, je reste donc sur A. platyacanthus

Roberto PILLON le 25/07/15

Le apparence de la partie supérieure des plaques de Astropecten bispinosus est très différent, comme le montre cette photo.

Roberto PILLON le 25/07/15

Bonsoir, elle est sûrement Astropecten platyacanthus.Elle se distingue de Astropecten bispinosus principalement pour les épines superomarginal loin du bord intérieur de plaques que ils laisser sur le dessus, sur la base d'eux, une petite surface nue qu'il est blanc, si il ya une forte épines dans la plaque (généralement dans les plaques près le disque) ou bleu-violet si la plaque a très petites épines ou pas d'épines (généralement vers la pointe de bras). Ceci est la meilleure façon de distinguer ces deux espèces dans la mer.

It is distinguished from Astropecten bispinosus mainly for the superomarginal spines far from the inside edge of plates and they leave on top, on the base of them, a small bare area. Another important Astropecten platyacanthus’s feature is that the superomarginal plates are laterally, on vertical face, covered with scales and small spines rather than nude. Moreover, it is different because it has smaller, irregularly shaped, laterally flattened (rather than clean conical spine) superomarginal spines and because it has average less superomarginal plates on each arm. In addition, on average Astropecten platyacanthus has a central disc larger, a darker oral side and a small red point in the point of arms have.
It has narrow and high superomarginal plates, laterally covered with scales and small spines (on vertical face). Every superomarginal plates is equipped with one strong spine, usually sharp but irregularly shaped, slightly flattened laterally, often yellow or orange but rarely off white. Sometimes, especially in young specimen, only superomarginal plates between the arms are equipped with one strong spine while others are not (in some rare specimens all the superomarginal plates are totally devoid of spines). In populations of certain areas of the Mediterranean (for example, the South of Corsica) this feature is very frequent. The superomarginal spines are (more or less) far from the inside edge of plates and they leave on top, on the base of them, a small bare area that it is white if there is a strong spine in the plate (usually in the plates near the disc) or blue-violet if the plate has very small spine or no spine (usually towards the tip of arms). The maximum number of superomarginal plates, observed on each arm, is 48; normally the number is between 29 and 43, depending on the size of the starfish. The inferomarginal spines are long, flat and quite pointed. It is an Astropecten with very variables features and it can have wide or narrow arms. The aboral side has very variables colours and it can be more or less dark brown, olive green, pink-brown, bluish-grey. The oral side usually is yellow-brown. It lives on all mobile seabed at depths between 1 and 60 m, but it is more frequently in seabed of mixed coarse sand and mud at 1-4 m depth. This specie is active and easy to find during the night but also during the day, especially in early morning and late afternoon. Normally it reaches a diameter of 9-12 cm and exceptionally it can measure up to 18 cm. It is the Mediterranean Astropecten hardest to identify both for the variability of features of the species, both for the resemblance to some other species.

Sylvain LE BRIS le 25/07/15

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