The lowest cell density to induce significant levels of metamorphosis was 7200±520 cells mm−2 and at this density 50±12% of larvae had undergone metamorphosis (F = 4.2, p = 0.002, pair-wise comparison to the negative control).
Isolate J010 induced significant levels of metamorphosis at cell densities as low as 7,000 cells mm−2 (Fig. 2), and comparable densities for at least individual genera of bacteria, including Pseudoalteromonas, do occur on seaweeds in the field [37].
The 1∶10 and 1∶100 dilution of synthetic TBP resulted in the same levels of metamorphosis (∼90%) after 6 h and were different from the control (for 1∶10; F = 17, p = 0.001; for 1∶100; F = 20, p = 0.001, pair-wise comparison to the negative control).
Parameter estimates for the continuous time model (Table 2) clearly show that ad libitum food and medium and warm temperature levels increase the probability of metamorphosis relative to that in restricted food level and cold temperature.
To investigate this, premetamorphic tadpoles at stage 54 were treated for 0-7 days with 10 nM T3, a concentration close to the physiological plasma T3 level at the climax of metamorphosis [ 47].
The plasma T3 rises to peak levels at the climax of metamorphosis and subsequently is reduced to much lower levels by the end of metamorphosis.
Its expression increased further during metamorphosis to reach high levels at the end of metamorphosis.
To determine whether the total intestinal expression of the HAL genes changes during metamorphosis and to rule out any potential effects on mRNA levels by the enzymatic separation of the Ep and non-Ep, total RNA was isolated from the small intestine of animals from premetamorphic stage 54 to the end of metamorphosis (stage 66) and subjected to qRT-PCR analysis.
While much is known about adult, sex-specific phenotypes caused by mutations in dsx and fru [ 5, 6], how dsx and fru direct sex-specific development at the level of gene expression during metamorphosis is still an open question.
However, by the later stages of metamorphosis, the levels of these transcripts remain high only in wild type females and drop to trough levels in wild type males, and tud male and female progeny.
