. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 60 S. J. FROGGETT AND E. M. LEISE en 100 'in -n 80 Q. t_ § 60 £ £ 40 1 20 2 Q) CL 0 Ii n=60 Q Q K H 11 I I •JT- ~ Controls [L-NAME] B - Arrows indicate concentrations that were significantly effective by 24 h but not at 48 h. n = 30 for 10"" and 10~'° M L-NAME. (B) Injections of the inactive isomer D-NAME induced no significant rates of metamorphosis by 48 h. (iS-HT = injected 5-HT). phose by diatoms or associated organisms that occur natu- rally in their littoral habitats (Leise et ai, 1996), but we have no unders
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 60 S. J. FROGGETT AND E. M. LEISE en 100 'in -n 80 Q. t_ § 60 £ £ 40 1 20 2 Q) CL 0 Ii n=60 Q Q K H 11 I I •JT- ~ Controls [L-NAME] B - Arrows indicate concentrations that were significantly effective by 24 h but not at 48 h. n = 30 for 10"" and 10~'° M L-NAME. (B) Injections of the inactive isomer D-NAME induced no significant rates of metamorphosis by 48 h. (iS-HT = injected 5-HT). phose by diatoms or associated organisms that occur natu- rally in their littoral habitats (Leise et ai, 1996), but we have no understanding of the time course for metamorpho- sis in that situation. Our results have led us to hypothesize that NO production is necessary for the maintenance of the larval state until an appropriate metamorphic cue is de- tected. Preliminary data from experiments on Pliestilla si- bogae suggest that NO may be active in the metamorphic pathway in this species as well (Meleshkevitch et ai, 1997). The ubiquity of NO in molluscan metamorphosis and its specific actions in this process remain to be determined. Although the tranformations that invertebrate larvae un- dergo in reaction to metamorphic cues are among their most well known activities (Pawlik, 1992), unsuitable habitats can also elicit distinctly negative responses from some larvae, such as those of the polychaetes Nereis vexillosa and Capitella sp. (Woodin, 1991). We recently found a similar effect on llvanassa larvae from one species of benthic diatom. Extracts of cultures of a sheathed pennate diatom species that were isolated from sediments obtained at Myr- tle Grove. North Carolina, inhibit spontaneous metamor- phosis in older (>3 weeks in culture) llyanassa larvae (Leise et ai, 1996; unpubl. data). Such negative metamor- phic actions and the uncertainty of larval encounters with appropriate juvenile habitats suggest that the maintenance of the larval life-history phase is an integral component of the metamorp
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
