Fish have no hands or fingers. Can a handless character become a member of the Green Lantern Corps?
Yes. There are several "handless" characters, notably Leezle-Pon, a super-intelligent version of the smallpox virus
There was also a giant blue whale Lantern (unnamed) in The Last Days of Animal Man:
And an unnamed green lantern fish (wearing a sweater-vest) in Green Lantern V3, #21
As well as old friend Mogo, the sentient planet. It's not entirely clear where he keeps his ring, but planets don't generally have fingers...
It's a big universe out there and since Green Lanterns (indeed ALL the various Color corps members) come from a diverse community of alien species, this includes Lanterns without fingers, hands or even appendages.
- This group of Green Lanterns shows several members who do not have fingers. There are numerous insectoids, intelligent plants, fungi and the occasional living ecosystem (See: Mogo) all capable of using the Green Power by holding a ring within or around their body. Power rings can change their shapes to accommodate their users.
(See: Do Power Rings get resized for each user? and Why do some Green Lanterns talk to their rings when giving a command? for more information about the Green Lantern Power Ring.)
G'Nort: Appearing in the Animated Brave and the Bold, the less-than-intelligent G'Nort wears his ring on a band around his single digit appendage. G'Nort has a good heart which offsets his sometimes substandard level of intelligence.
Oliversity - Green Lantern of Space Sector 2111: Oliversity was one of the Green Lanterns responsible for guarding Sinestro when he was brought to trial on Oa. He was a friend of Kilowog, and was in the "firing squad" that executed Sinestro. (Green Lantern Corps #222)
- Apros is an intelligent plant whose ring is often depicted as being held inside his body, though sometimes he will show his ring on a tentacle displaying it as a symbol. Apros is one of the oldest and most decorated of Green Lanterns. He was once part of the Green Lantern Corps Honor Guard where Apros protected the Guardians of the Universe with the help of K'ryssma and Tomar-Re. It also trains rookie and helps them overcome there fear with his psionic abilities. Apros was responsible for training the reluctant rookie, Guy Gardner of Earth.
Dkrtzy RRR - A Green Lantern that isn't even a living thing is counted among their members. Dkrtzy RRR is a sentient mathematical equation that can enter the minds of others and wipe them. Dkrtzy RRR was created by Alan Moore. How Dkrtzy RRR embodies its ring, perhaps as an internal fractal mathematical model, is not known.
Some commonly known Green Lanterns who lacked fingers or used exotic rings designed for their unique physiology.
- Apros - sentient plant (see above)
- Brokk - aquatic
- Bzzd - insectoid
- Charqwep - sentient fungoid
- Chaselon - Crystalline life form
- Cimfet Tau - aquatic, lobster-like in appearance
- Dkrtzy Rrr - Mathematical, fractal life form (see above)
- Diamalon - Crystalline life form
- Flodo Span - "Abstract" or conceptual life-form
- Larvox - insectoid
- Leezle Pon - intelligent viral life-form
- Lin Canar - Aquatic plant life
- M'Dhana - unknown, perhaps mineral-based
- Mogo - intelligent planetary ecosystem
- Olapet - intelligent plant
- Oliversity - resembles a serpent
Puffball Collective - hive mind collective entity
Not only do some Green Lanterns come without fingers, some Lanterns don't utilize entire senses, including vision, for example. Those Lanterns do not even SEE the Green Lantern nor use light as their primary sense organ.
Rot Lop Fan who appeared in Tales of The Green Lantern Corps Annual # 3 (1987) is a member of the F-Sharp Bells, a group of Green Lanterns who use the Green Power without sight.
Among the blind creatures of the Deeps was Rot Lop Fan a brave and noble member of his people and an ideal candidate for the Green Lantern Corps. Rot Lop Fan was approached by Katma Tui to join the Corps and serve as a Green Lantern however her request was meaningless to the blind alien. Being from an entirely blind race, Rot Lop Fan had no concept of light or color. The terms "green" and "lantern" had no meaning to him, and could not be translated by the power ring.