What Are the World's LARGEST Starfish??

The other day, I was thinking of BIG stuff. and then, a bit later, I was thinking of STARFISH stuff. 

and then I thought of cake. (mmm..cake..)

And then I thought What about a BIG Starfish POST??!! A survey of all the world's LARGEST starfish!!! 

Criteria: Different groups were evaluated primarily in terms of overall diameter and volume/mass. Some species, such as the brisingid Midgardia xandaros have REALLY long arm spans (4.5 feet!-to be discussed in a future blog!) but are just very minimal otherwise.

So...what's with the bigness?? Size doesn't seem to be really constrained to any specific climate type area. You see them in both

1. Cold-Temperate water regions

2. And in the Tropics. But WHY?? Nutrients? Predator defense? Growth constraints? Hmm.....
And so..in order of what I believe to be a rough estimate of overall mass to size priority..... (11. Labidiaster annulatus gets honorable mention!)

10. The Oreasteridae Fisher 1911 (Order Valvatida) Here is a WHOLE family of starfishes whose primary features include having heavily calcified, BIG oversized bodies. Three included species below are listed separately.

Most occur in the tropical Indo-Pacific in relatively shallow-water (some individual species occur in deeper-water). Examples: Culcita novaeguineae Mueller & Troschel 1842,  Pentaceraster spp. Protoreaster nodosus (Linnaeus 1758)

9. Big Luidia species (Familly Luidiidae, Order Paxillosida)

(thanks to Jen Hammock, USARP for scale!)

Most species of Luidia are pretty small to medium sized. Luidia occurs mostly in tropical to temperate shallow-water habitats and live on sandy bottoms throughout the world. Mostly have an adult diameter of roughly 7-15 cm but in some exceptional cases, they get HUGE. Pictured above is the rarely encountered Luidia superba from the Galapagos. This is believed to be a normal adult size. About 1-2 feet across (30-60 cm). YOW. (but, again-poorly known...)

A few other species of Luidia also get big...such as this Luidia maculata from Singapore

8. Macroptychaster accrescens (Koehler 1920) (family Astropectinidae-Order Paxillosida)

(from the recent NIWA cruise to Antarctica)

A big animal that lives in mud-soft-sediment in the Southern Ocean/Antarctica and has pointed tube feet. Adult size for Macroptychaster is about 1-2 feet (30-60 cm). The body cavity is frequently swollen making it appear even bigger than it already is! This species falls into the category "About which, little is known.."

 7. Poraster superbus (Mobius 1859) (Family Oreasteridae, order Valvatida)
A big oreasterid from the Indian Ocean. Lives mostly in tropical-shallow waters. All the adults I've seen are big, 1-2 feet across. This species also falls into the category "About which, little is known.."

 6. Oreaster reticulatus (Linnaeus 1758) (Family Oreasteridae, Order Valvatida) Oreaster reticulatus lives in shall0w-water settings in the tropical Atlantic. Not as big as some, only about 1-2 feet across (a big one shown above), but these get THICK. Easily 6-9 inches thick along the disk! An animal that has been facing regional extinction due to an overzealous tourist trade. An increasing amount of information on this animal is becoming available..a microalgal film/scavenger/opportunist and sponge feeder with some foraging-feeding behavioral complexity. A blog on this animal awaits!

  5. Astrosarkus idipii Mah 2003 (Family Oreasteridae, Order Valvatida) A weird beast I described back in 2003. This was first discovered by the Coral Reef Research Foundation during a coral sub-reef expedition (aka the Twilight Zone Expedition) back in 1997. This species occurs mostly in deeper water and is, found throughout the Indo-Pacific.

Its about 1.5-2.0 feet across but about 4-5 inches THICK. Its also unusual in that its mostly decalcified and has the fleshy consistency of a pumpkin..Its overall volume makes it much more massive then say, Luidia. Another one in the "about which, little is known" category...(but I will blog about it too someday!)

4. Pisaster brevispinus (Stimpson 1857) (Family Asteriidae, Order Forcipulatida) I have written about the Giant Pink Starfish from the west coast of North America. The lesson here is that Pisaster brevispinus gets BIG. Especially under conditions where it can feed and GROW. Aquariums I've worked in or visited report that this species can reach OVER TWO FEET across (~60 cm!)

Here is a big specimen collected years ago-with a human for scale. 

(thanks to Mr. Timothy Coffer for his modelling expertise!)

4a. Acanthaster planci (Linnaeus 1758) (family Acanthasteridae, order Valvatida) A big starfish-and tied for 4th place, but sorry Wikipedia, NOT the second largest in the world. Typical sizes range in the 1-2 foot size range (30-60 cm) but with reports of some animals reaching slightly over 2 feet (70 cm). I've written about this infamous Indo-Pacific corallivore and will undoubtedly do so in the future!

3. Evasterias echinosoma Fisher 1926 (Family Asteriidae, Order Forcipulatida) I have only ever seen one or two specimens of this species of this size..but diameter is recorded at 37.79 inches (96 cm!) Making it over 3 FEET wide! This species occurs in Alaska and the Aleutians. Many are big..but not all are quite this large..

2. Pycnopodia helianthoides (Brandt 1835) (Family Asteriidae-Pycnopodiinae, Order Forcipulatida) A famously known species known only from the west coast of the North America. Under aquarium or ideal feeding conditions-this animal easily reaches 2 feet (or 80 cm) across but has been observed to surpass THREE feet in diameter. But thing is, its all mostly decalcified.

Mostly fleshy tissue and soft stuff. Big volume and diameter but not much to its size out of water.. Pycnopodia is a voracious predator of uh..well almost everything. There's plenty known about it which is why I'll talk about it more during another blog post.

1. Thromidia catalai Pope & Rowe 1977, Thromidia gigas Mortensen 1935 (Family Mithrodiidae, Order Valvatida)

(From Dave Lane on the Santo 2006 Expedition)

Most people don't realize that one of the biggest, most massive starfish in the world lives in the South Pacific and Indian Ocean primarily in deeper water settings.

 It weighs in here at #1 because of its overall bulk, which reaches over 13.2 pounds (SIX kilograms!-yes, even I am skeptical) but reaches a maximum span of a little over 2 feet (60-65 cm).