Ci sono molti tipi diversi di stelle marine in tutti gli oceani e i mari del mondo. Giocano un ruolo importante mangiando altri animali e venendo mangiati da altri.

Sono grandi predatori di altri animali invertebrati. In particolare predano i bivalvi come vongole, cozze e ostriche. Il numero di stelle marine può influenzare il numero di bivalvi che possono vivere in un'area. A loro volta le stelle marine sono cibo per altri animali. Le stelle marine mangiano altre stelle marine e anche le lontre di mare e i pesci come il pesce lupo e il pesce balestra le mangiano.

Here are a couple of examples of what Joseph O’Sullivan is talking about in his answer:

1. In 1969, marine biologist Robert T. Paine conducted an experiment on what happens if one species of star, the Ochre Star (Pisaster ochraceus) is removed from an ecosystem. Basically he inventoried species diversity on two similar sections of rocky reef and then removed all the ochre stars from one section. Over the next year or so he returned to make sure the stars didn’t return to the removal area and then did a follow up inventory to see what, if anything, changed. Where the stars remained the diversity stayed the same while, in the removal area, diversity plummeted as the California Mussel (Mytilus californianus) crowded out virtually everything else. From this experiment Paine coined the terms “keystone species” & “keystone predator”. That concept has since been extended to many different situations in ecology. More information: Keystone species - Wikipedia
2. More recently, in 2013 & 2014 a panzootic dubbed Sea Star Wasting Disease (SSWD) killed off a high percentage of the stars on the West Coast of North America: Sea star wasting disease - Wikipedia Most of the large species stars were affected but the hardest hit was the Sunflower Star (Pycnopodia helianthoides) which has been extirpated in certain parts of the coast. Now, it has long been known that Sunflower Stars are predators on sea urchins but it has only recently come to light just how important they are to controlling the urchin population. In the absence of what turns out to be its MAJOR predator, the urchin population has exploded and is now in the process of wiping out huge areas of kelp forest in California. The kelp forests are lifelong habitat for a ton of species and serve as ‘nursery’ for a ton more. It is arguable that the kelp forests are the major driver for marine species diversity in California waters and the elimination of one sea star species is in the process of crashing it in less than a decade. British Columbia has reported similar problems while, at least so far, Washington and Oregon seem to be doing better.