Diving with Pencil Squids

Lanta Marine Life | Loliginidae

Pencil squid are generally small cephalopods, those living inshore around 10 - 20 cm in length, though species living offshore can reach up to 40 cm long. Small groups of 5 - 10 individuals are often seen in the shallows while diving from Koh Lanta.

The body shape varies from short and stout to long and slender, and the eyes are covered with a transparent membrane.

The mouth is surrounded by 10 appendages, comprising eight arms and two tentacles. Tentacles are used to catch prey.

Arms have suckers along their entire length, while tentacles only have suckers at the tip. Octopuses have eight arms and no tentacles, while other cephalopods - such as cuttlefish and squids - have eight arms and two tentacles. Pencil squid arms are about half the length of the body.

Pencil squid are a range of colours, translucent to dense, bright scarlet (in some species with yellow and pink chromatophores) to dark brown (nearly black), darker dorsally, but highly variable depending on the behavioural situation.

All squid share the ability to squirt ink as a defensive measure.

1 species found on this page:

Bigfin Reef Squid (Sepioteuthis lessoniana)

Bigfin Reef Squid

(Sepioteuthis lessoniana)

Sepioteuthis lessoniana @ Koh Haa

The Bigfin Reef Squid has a large, thick, oval fin which extends almost completely around the margins of the entire mantle.

This squid can sometimes be confused with a cuttlefish due to the large, wide fin. There is a narrow whitish or bluish line where the fin attaches to the mantle, and a small ridge or line in the middle of the back where the fins meet.

Like many other cephalopods, the Bigfin Reef Squid can produce a jet of ink when it feels threatened.

The Bigfin Reef Squid grows to 36 cm, however they are more usually observed in small schools in the 10 cm - 15 cm range close to coral reefs.

This species has the fastest recorded growth rate of large marine invertebrates, with the diet including shrimp, mollusks, fishes, and other squid.