Idiosepius

Idiosepius is a genus of very small squid in the family Idiosepiidae, commonly known as pygmy squids. Members of this genus are among the smallest living cephalopods, with mantle lengths typically only a few centimeters or less, and some species are considered even smaller.

These squids inhabit shallow coastal waters, often in seagrass beds, mangroves, and algal-rich environments. They are distributed in the western Pacific region, with records from parts of East and Southeast Asia. Their small size and cryptic coloration aid them in blending with their vegetation-friendly habitats.

A distinctive feature of Idiosepius is its adhesive capability. The mantle or associated tissues produce a sticky substance that enables the animal to attach itself firmly to seagrass blades and other substrates. This adaptation helps them resist currents and predation while they feed and rest within their vegetation-dominated habitats. Like other cephalopods, they possess a mantle, two fins, and arms arranged around a siphon, with coloration and patterning used for camouflage.

Reproduction involves direct fertilization, with females laying gelatinous eggs that are often deposited on vegetation or substrates in the vicinity of seagrass beds. The eggs develop into free-swimming paralarvae before maturing into adults. The genus includes several described species, such as Idiosepius pygmaeus and Idiosepius paradoxus, among others recognized in regional faunas. More detailed species-level information varies across sources and regions. Conservation concerns for Idiosepius largely relate to habitat degradation, particularly of shallow coastal ecosystems.