na ▁are ▁thought ▁to ▁use ▁their ▁bi ol um ines cent ▁cap ability ▁as ▁a ▁l ure ▁to ▁attract ▁fish . ▁This ▁genus ▁is ▁one ▁of ▁the ▁few ▁to ▁pre y ▁on ▁fish ▁rather ▁than ▁cr ust ace ans . ▁The ▁bi ol um ines cent ▁org ans ▁on ▁these ▁individuals ▁f lick er , ▁and ▁thus ▁it ▁has ▁been ▁concluded ▁that ▁they ▁use ▁bi ol um ines c ence ▁to ▁attract ▁pre y . ▁ ▁Mov ement ▁ ▁Si phon op hor es ▁use ▁a ▁method ▁of ▁lo com otion ▁similar ▁to ▁jet ▁prop ulsion . ▁A ▁ne ct oph ore ▁is ▁a ▁gather ing ▁of ▁many ▁si phon op hor es , ▁and ▁depending ▁on ▁where ▁each ▁individual ▁si phon oph ore ▁is ▁position ed ▁within ▁the ▁ne ct oph ore , ▁their ▁function ▁diff ers . ▁Col onial ▁movement ▁is ▁determined ▁by ▁individual ▁si phon op hor es ▁of ▁all ▁development al ▁stages . ▁The ▁smaller ▁individuals ▁are ▁concentr ated ▁towards ▁the ▁top ▁of ▁the ▁ne ct oph ore , ▁and ▁their ▁function ▁is ▁turning ▁and ▁adjust ing ▁the ▁orientation ▁of ▁the ▁col ony . ▁The ▁smaller ▁the ▁individual , ▁the ▁younger ▁it ▁is . ▁The ▁larger ▁the ▁individual , ▁the ▁older ▁it ▁is . ▁The ▁larger ▁individuals ▁are ▁located ▁at ▁the ▁base ▁of ▁the ▁col ony , ▁and ▁their ▁main ▁function ▁is ▁thrust ▁prop ulsion . ▁These ▁larger ▁individuals ▁are ▁important ▁in ▁att aining ▁the ▁maximum ▁speed ▁of ▁the ▁col ony . ▁The ▁colonial ▁organization ▁of ▁si phon op