The larvae of ommastrephid squid go through a ‘Rhynchoteuthion stage’ where the tentacles fuse into a proboscis, which is apparently involved with feeding on microbes such as bacteria.
The image is from:
Roper, C. & Lu, C. (1978) Rhynchoteuthion Larvae Of Ommastrephid Squids Of The Western North Atlantic, With The First Description Of Larvae And Juveniles Of Illex illecebrosus. Proceedings of The Biological Society of Washington 91 1039–1059.
Information on their use when feeding:
Vidal, E. & Haimovici, M. (1998) Feeding and the Possible Role of the Proboscis and Mucus Cover in the Ingestion of Microorganisms by Rhynchoteuthion Paralarvae (Cephalopoda: Ommastrephidae). Bulletin of Marine Science 63(2) 305–316.