---
title: Arabian Crust-sponge (Hemimycale arabica)
scientific_name: Hemimycale arabica
common_name: Arabian Crust-sponge
taxon: Sponge
published: 2023-12-30T17:53:06.333Z
updated: 2026-08-29T12:44:23.142Z
tags: Arabian Crust-sponge, Hemimycale arabica, Sponge, Red Sea, Marine Life, Diving
url: https://redseacreatures.com/taxon/invertebrate/sponge/arabian-crust-sponge
---

# Arabian Crust-sponge (*Hemimycale arabica*)

## Quick facts

- **Group:** Sponge (*Porifera*)
- **Size:** up to 20 cm
- **Diet:** Filter feeder
- **Activity:** Cathemeral
- **Rarity:** Common
- **Habitat:** dead coral and reef rock
- **Endemic:** Endemic to the Red Sea

## How to recognise it

- dark blue crust spreading over dead coral
- tissue underneath the blue surface is yellow
- smooth surface with vents scattered across the whole crust
- soft, thick and easily cut
- patches up to 20 cm across

The blue is only the outside. This sponge spreads over dead coral as a dark blue crust, and the tissue underneath that skin is yellow, so any place where the surface has been nicked shows a different color from the sponge around it. The describers recorded exactly that in 2004: dark blue alive on the exterior, yellow within.

It grows as an encrusting sheet thickening into low irregular masses, creeping over dead coral and reef rock, its surface smooth rather than warty, with vents scattered across the whole crust instead of gathered into chimneys. The texture is soft and it cuts easily. Patches reach about 20 cm (8 in) across.

What is doing the growing is an animal with no organs. There is no mouth, no gut and no nerves; a sponge is cells arranged around plumbing. Water enters through thousands of pinhole pores over the surface, is driven through internal chambers by cells with beating whips, and leaves through the vents, and each cell captures its own food, bacteria and particles far smaller than anything a fish could eat. A sponge this size processes many times its own volume of water every hour.

Most sponges cannot be named from a photograph. What separates the species is the skeleton, in this case a loose mesh of slender spicule tracts with a dense matted layer at the surface, and reading it means a slide and a microscope. This one is easier than most because of the color pair, but a blue crust on its own is not enough: check for the yellow underneath before you commit.

It is known only from this sea, the type material coming from the northern and central Red Sea and records reaching the head of the Gulf of Aqaba, and it was not described at all until 2004. Chemists have since pulled a set of hydantoin alkaloids out of it, one of many Red Sea sponges being worked through for compounds worth developing.

## Also known as

- **English:** Arabian Crust Sponge

---

*Source: [Red Sea Creatures](https://redseacreatures.com/taxon/invertebrate/sponge/arabian-crust-sponge)*
*Updated: August 29, 2026*