Lolignidae Family of Pencil Squids

Two Pencil Squids of the Lolignidae Family can be found in this website:

Phylogeny: Pencil Squid of the Lolignidae Family are in the phylum Mollusca and in the class Cephalopoda. This class includes squids, octopuses, cuttlefish, and nautiloids. Cephalopods are characterized by having a mantle (body), a head, and a foot that is modified into a series of, at least, eight arms. The arms attach to the head and surround the mouth. The arms may be equipped with suckers, hooks, or cirri. Some will have tentacles in addition to their arms. All cephalopods have three hearts. Two hearts pump blood to the gills, and one heart pumps blood to the rest of the body. Cephalopods have blue blood, because they bind oxygen with hemocyanin. Cephalopods have relatively large brains and complex eyes. Cephalopods can change the color of their skin at will, and very quickly. They do this by nerve controlled chromatophores (pigment sacks in the skin), iridiphores (reflect light to appear iridescent), and leucophores (scatter ambient light).  Cephalopods also have the ability to squirt “ink” into the water to confuse, or hide from, predators. Squid are in the superorder Decapodiformes. Decapodiformes are characterized as having an elongate body, eight arms, two tentacles, large eyes, and an internal shell, known as a gladius or pen. The pen is made of chitin and may be rod or feather shaped. The pen provides rigidity to the body, as well as an attachment point for muscles. The suckers on the arms and tentacles may be located on stalks and have chitinous rings or hooks. The tentacles are modified arms that are usually longer than the arms, are retractile, and terminate in wide, flat lobes (tentacular clubs). The only suckers on the tentacles are located on the tentacular clubs. Fins are attached to the mantle and may be used for swimming, hovering, or maneuvering. Pencil Squid are in the order Myopsida. Myopsid Squid lack eyelids and instead have a transparent membrane covering the eye.  They have suckers with circularis muscles, but never hooks. Their tentacular clubs lack a carpal locking apparatus. Myopsid Squid are also known as “near shore squid” because they are generally found in shallow water. The the Lolignidae Family is one of two families within this order. The the Lolignidae Family is made up of ten genera and around forty-seven species. Squid in this family are also commonly known as Loliginids. The name Lolignidae comes from the Latin word meaning “squid” or “cuttlefish”.

Morphology: Loliginid Squid have a body that tapers to a point, and fins that unite posteriorly. The head has a tentacle pocket. They have two rows of suckers along their arms, and four rows on the tentacular clubs. These squid rarely have photophores. The pen runs the length of the mantle. They have a cornea covering the lens of each eye. They may be translucent or opaque, and highly variable in color. They can change color, and color patterns almost instantly. Squid are usually measured by mantle length, because it is so difficult to measure the tentacles accurately. These squid reach a maximum mantle length of 40 cm (16 inches), though the majority are only around 10 cm (3.9 inches).

Habitat and Distribution: Pencil Squid are generally found in open water, over hard or soft substrates. They range from the surface to around 700 m (2,300 feet), though most are found much shallower. They are found worldwide, in tropical to temperate seas. Four species from the Lolignidae Family are found in the Atlantic Ocean along Mexico’s east coast and five species in the Pacific Ocean along the west coast.

Reproduction:  Pencil Squid are gonochoric (male or female for life) and reproduce sexually. In male Pencil Squid, one of the arms is modified to carry sperm in an open groove. This arm is known as a hectocotylus. The male inserts this arm under the mantle of the female during reproduction, delivering packets of sperm (spermatophores). The female lays eggs that are attached to the sea floor substrate, in finger-like clusters. The male and female both die within weeks or months after mating.

Ecosystem Roles: Pencil Squid are strong swimmers, and big eaters. Some species eat up to 30% of their body weight every day. They eat crabs, shrimp, fish, polychaetes, and other mollusks. They are an important food source for sea birds, fish, marine mammals, and other squid.