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Each starfish arm contains two gonads that release gametes through openings called gonoducts, located on the central disc between the arms. Fertilization is generally external but in a few species, internal fertilization takes place.
Patiria miniata, the bat star, sea bat, webbed star, or broad-disk star, is a species of sea star (also called a starfish) in the family Asterinidae. It typically has five arms, with the center disk of the animal being much wider than the stubby arms are in length. [2] Although the bat star usually has five arms, it sometimes has as many as ...
The main elements, to determine the various species from photo, are: the appearance of the dorsal marginal plates and spines, the size, the shape of disc and arms. For a good identification by sea photo it is important to take a complete picture of all the subject, a picture of the detail of the marginal plates and to measure as precisely as ...
The starfish body plan consists of five to six arms radiating from a central disk. Regenerative ability differs greatly among starfish species, but can generally be classified within three categories: unidirectional regeneration, disk-dependent bidirectional regeneration, and disk-independent bidirectional regeneration.
The common starfish normally has five arms, broad at their base and gradually tapering to a point at their tips, which are often turned up slightly. There is a line of short white spines running along the centre of the aboral (upper) surface of the arms with low, soft mounds called papulae on either side.
It grows to a diameter of about 30 to 40 centimetres (12 to 16 in). The aboral or upper surface has a patchwork of closely packed spiny plates. The square ones near the edge of the arms are cream coloured and the irregular ones in a band running down the middle of the arms are grey. The margins of the arms are fringed with short white spines.
Choriaster granulatus is a large sea star with a convex body and five short arms. The arms have rounded tips, making it appear "phallic", leading to one of its common names being "the doughboy starfish". Relatively large in comparison with other sea stars, its maximum radius is about 27 centimetres (11 in).
Most starfish in the genus Leptasterias have six arms, although five-armed individuals can occur. The Brisingida also contain some six-armed species. Amongst the brittle stars, six-armed species such as Ophiothela danae , Ophiactis savignyi , and Ophionotus hexactis exist, and Ophiacantha vivipara often has more than six.