Paralarval gonatid squids (Cephalopoda : Oegopsida) from the Mid-North Atlantic Ocean

Ninety six gonatid cephalopod specimens (Oegopsida: Gonatidae) from the Uni versity of Amsterdam Mid-North Atlantic Plankton Expeditions were analyzed and two species were identified: Gonatus steenstrupi (Kristensen 1981) and Gonatus fabricii (Lichtenstein 1818). Gonatids were collected only in sprin g and summer, despite sampling in autumn and winter. This paper describes a spects of their development and reports their geographical distribution in the central North Atlantic Ocean. Chromatophore patterns were the most cons istently useful characters for distinguishing between the species. Among 34 measurements, Tentacle Length (TtL) relative to Dorsal Mantle Length (ML) and number of suckers on Arms I-IV were useful for distinguishing specimens >13 mm ML. Both species develop hooks from suckers on the arms and tentacu lar clubs at ML >20 mm. Subtle differences were noted in the morphology of the funnel pads except in the smallest specimens. Specimens of G. steenstru pi >20 mm ML were collected at greater depths (250 to 995 m) than the small er specimens (found at depths <200 m). Our data suggest that 20 mm ML is th e point of transition between paralarvae and juveniles of G. steenstrupi, b ecause specimens larger than 20 mm ML have well defined hooks, and a juveni le vertical distribution is established.