RHYNE, A.L.**; JOHNSON, K.J.; LIN, J.; Florida Institute of Technology; Florida Institute of Technology; Florida Institute of Technology: Ontogenetic shift of spectral sensitivity in the larval phototaxis of two caridean shrimp, Lysmata wurdemanni and L. boggessi

We subjected larvae of two species of caridean shrimp (Lysmata wurdemanni and Lysmata boggess) to a range of light spectra and intensities to examine their phototactic responses. Larvae were less sensitive to light than some other decapod crustaceans, typically requiring a light intensity of 10¹⁴ photons m^-2 s^-1 to elicit a response. Both species displayed a spectral preference shift from 480 to 520 nm as they progressed from early to late zoeal stages. Spectral preference shifts during ontogeny are previously unknown in crustaceans or, to our knowledge, other taxa. The phototaxis of these larvae is interesting in light of our recent reevaluation the taxonomic status of western Atlantic Lysmata. These two species of Lysmata are nearly identical to one another morphologically and possess similar larval development; both occur in Florida Bay and on the west coast of Florida. L. boggessi has a restricted geographic range (Western Coast of Florida and Florida Bay) and is abundant in shallower water (3-10 meters), while L. wurdemanni is widely dispersed in the northwest America but mainly occurs in deeper water in Florida Bay (12-20 meters) and is rare in the seagrass beds on the West Coast of Florida. The unique phototactic responses of these larvae may provide clues as to how maturing larvae prepare for settlement in their respective adult habitats.