13.4 Wednesday, Jan. 4 Reduced lateral line canal development in the round goby, Neogobius melanostomus DICKSON, JM*; UDVADIA, AJ; JANSSEN, J; University of Rhode Island; Univsersity of Wisconsin, Milwaukee; University of Wisconsin, Milwaukee email@example.com
Fish can detect water movement through mechanosensory organs of the lateral line system known as neuromasts. There are four major canal morphologies that can be found on the head of teleosts; narrow, reduced, widened, and branched. Round gobies, Neogobius melanostomus, have the reduced canal morphology where canal segments containing neuromasts are replaced by lines of superficial (SF) neuromasts below the eye. The reduced canal morphology is thought to be derived from the narrow canal morphology that results from changes in the onset or rate of development (i.e. neuromasts are present but canal development would be halted before the canal develops). We hypothesize that the initial development of the round goby should be similar to that described for narrow canal species. The initial development was documented using samples prepared for scanning electron microscopy and then confirmed in live fish by labeling neuromasts with the vital fluorescent stain DASPEI. Shortly after hatching the larger presumptive canal neuromasts or paedomorphic homologues are present. By 7 mm SL there are horizontal lines of SF present under the eye. At 9 mm SL the supraorbital canal above the eye has enclosed. Orthogonal lines of SF neuromasts have begun to form by 14 mm SL and by 30 mm SL the pattern of SF neuromasts reflects the adult pattern. In the mandibular region there is no enclosed canal, but there are two lines of SF neuromasts. One of those lines is in a groove, which is the first sign of canal development described in other fishes. More SF neuromasts may be advantageous because they are more sensitive to changes in velocity and they can detect lower frequencies.