Daily Rings in Saccular Otoliths of Lepomis sp. and Talipia mossambica

[摘要] Daily rings were formed on saccular otoliths of known-age,laboratory raised pumpkinseed (Lepomis gibbosus), green sunfish (Lepomis-cyanellus), bluegill (Lepomis macrochirus), and Tilapia mossambica for at least 176, 170, 125, and 60 days,respectively. Subdaily rings were found in young laboratoryand wild fish, but were easily distinguished from daily rings.Width of daily rings of green sunfish was linearly related todaily increase in length of fish, and the number of rings wasa product of age of fish only, not length of fish or otolithradius. Otolith growth and daily ring formation in wild bluegilland largemouth bass (Micropterus salmoides) appeared to besimilar to those in laboratory-raised fish. Saccular otolithsof green sunfish under simulated winter conditions ceased toproduce daily rings, but did form an annulus. Two kinds ofsaccular otolith tissue were present in most of the largerlaboratory fish and wild bluegill, but were not observed inwild largemouth bass:the first, which was present in all areasof the otolith except the extreme posterior end, was translucent, and daily rings were well defined in it; the second was presentonly in the posterior end, was opaque, and daily rings in thisarea etched poorly and were difficult to discern. Both tissueswere calcium carbonate in the aragonite form.To determine if light, cyclic feeding or an internal clockinfluenced daily ring formation, juvenile 1· mossambica, whichhad been exposed to continuous light (LL) and constant temperaturesince egg fertilization, were held under six experimentalconditions:1) LL, 27°C, and fed at three hour intervals,2) LL, 27°C, fed at three hour intervals with a nine hour breakin feeding every 24 hours, 3) L24:D12, 27°C, fed at 6 hourintervals, 4) Ll5:D9, 27°C, fed at 6 hour intervals (the firstfour conditions were maintained in environmental chambers,the remaining 2 in the laboratory), 5) 15:D9, 27°C, fed at 6hour intervals, 6) Ll5:D9, 25 to 26°C, fed at various timesevery day. Daily rings were formed only in groups 4, 5, and 6,indicating that a 24-hour light-dark cycle reinforcing aninternal, diurnal clock, were required for daily ring production.

[发布机构] University of Wisconsin-Stevens Point, College of Natural Resources