Luidia

Members of the genus are characterised by having long arms with pointed tips fringed with spines.[4] Their upper surfaces are covered with paxillae, pillar-like spines with flattened summits covered with minute spinules. The upper marginal plates are replaced by paxillae, but the lower marginal plates are large and covered with paxillae. The tube feet do not have suckers, but have two swollen regions. A mouth, oesophagus, and cardiac stomach are seen, but no pyloric stomach or anus is present. The gonads are underneath the sides of each arm.[5]

The early larval stages of starfish are known as bipinnarial larvae, and members of this genus do not continue their development after this stage into a brachiolar stage before undergoing metamorphosis. However, they are capable of larval cloning, with asexual reproduction taking place while they are larvae. This has been shown to take place both in the field and in laboratory cultures and has been studied by molecular analysis of sequences of mitochondrial tRNA to identify the taxa involved.[6]

These species are recognised by the World Register of Marine Species:[2]

• 
  Luidia alternata
• 
  Luidia atlantidea (MNHN)
• 
  Luidia australiae.
• 
  Luidia cilliaris
• 
  Luidia clathrata.
• 
  Luida columbia.
• 
  Luidia foliolata
• 
  Luidia heterozona.
• 
  Luida latiradiata.
• 
  Luidia lawrencei.
• 
  Luidia ludwigi.
• 
  Luidia maculata.
• 
  Luidia magellanica
• 
  Luidia magnifica (oral face).
• 
  Luidia neozelanica
• 
  Luidia porteri.
• 
  Luidia quinaria
• 
  Luidia sagamina
• 
  Luidia sarsi.
• 
  Luidia savignyi.
• 
  Luidia senegalensis
• 
  Luidia superba.