Dykning med Langryggede søpindsvin

Koh Lantas Marineliv | Diadematidae

Longspine Sea Urchins are a family of around 32 species of spiny, spherical, or globe shaped animals with hard shells which live on the seabed. Spotted everywhere, on all of our Koh Lanta dive trips.

As with other echinoderms, most urchins have a five part symmetry, with five equally sized parts radiating out from their central axes. The mouth is at the base, and the anus at the top.

The long spines are usually hollow, and most species have two series of spines, primary (long) and secondary (short), distributed over the surface of the body, with the shortest at the poles (top and bottom) and the longest at the equator (middle).

Ligesom søstjerner og søpølser har søpindsvin små rørfødder, som kan bruges til at 'gå' hen over havbunden, ofte hjulpet på vej af deres pigge. Et omvendt søpindsvin kan rette sig selv op ved at bruge sine rørfødder og manipulere sine pigge til gradvist at rulle sin krop op.

Ligesom andre søpindsvin er langfinnede søpindsvin følsomme over for berøring og kemikalier og kan registrere lys. De har øjepletter, som kan opfange lys, og piggene kan manipuleres, så lyset falder på øjepletterne. Når de registrerer skygger, kan de flygte fra en oplevet trussel eller bevæge sig mod et oplevet skjul.

Søpindsvin lever hovedsageligt af alger, men spiser også andre langsomt bevægende eller stationære hvirvelløse dyr, som de kan støde på. Ligesom andre familier af søpindsvin bliver de spist af søstjerner og aftrækkerfisk.

Tætte bestande af langfinnede søpindsvin kan hurtigt fortære vigtige marine algesamfund i et koralrevs økosystem og ødelægge økosystemets balance i de særlige områder, hvor disse ansamlinger forekommer.

2 arter fundet på denne side:

Double-Spined Urchin (Echinothrix calamaris)
Black Longspine Sea Urchin (Diadema setosum)

Double-Spined Urchin

(Echinothrix calamaris)

Double-Spined Urchin @ Koh Bida

The Double-Spined Urchin, or Banded Sea Urchin, has a slightly oval test (shell) which can grow up to 5 cm in diameter. As with all other members of the family Diadematidae, the hollow spines are two different lengths, and very obvious in this species.

The short spines are yellow to dark brown and can deliver a very painful sting. The longer spines can be light coloured, dark coloured, or banded light and dark, and grow to 15 cm in length. Juvenile cardinal fish (family Apogonidae) may hide in the spines for protection.

As with other sea urchins and echinoderms, the Double-Spined Urchin displays five-part symmetry which is clearly visible with the shorter spines.

The mouth is on the lower body surface, and the large anal opening on the top is a generally light colour, with many black and white speckles and spots. The anus is surrounded by a ring of light sensitive receptors which provide rudimentary vision.

The Double-Spined Urchin is nocturnal, feeding at night and usually seeking shelter during the day.

Black Longspine Sea Urchin

(Diadema setosum)

Diadema setosum @ Koh Bida

The Black Longspine Sea Urchin is common to all dive sites in Thailand. The central test (body shell) is almost spherical in shape (slightly squashed vertically), normally black, sometimes dark grey, and grows to 8 cm in diameter.

As with other Echinoderms, this species displays five-fold symmetry which can be seen in the five equally-spaced white dots on the body.

The Black Longspine Sea Urchin has long, hollow, black or white, occasionally banded spines. The spines are slightly venomous and can easily inflict a painful sting, though non fatal.

There is an orange to white ring around anal sac opening, and the body is covered with light receptors (eye spots) providing rudimentary vision. The entire body, is in effect, a very basic ‘eye’.

This species is found on sandy, rubble or rocky bottoms and can use it’s longer spines to move quickly along the seafloor.