Common condition indices are no more effective than body mass for estimating fat stores in insectivorous bats

Researchers often use simple body condition indices (BCI) to estimate the relative size of fat stores in bats. Animals determined to be in better condition are assumed to be more successful and have higher fitness. The most common BCI used in bat research are the ratio index (body mass divided by forearm length) or residual index (residuals of body mass-forearm length regression) of size-corrected body mass. We used data from previous and ongoing studies where body composition (fat mass and wet lean mass) was measured by quantitative magnetic resonance to test basic assumptions of BCI, determine whether BCI is an effective proxy of fat mass, and whether other approaches could be more effective. Using data from 1,471 individual measurements on 5 species, we found no support for the underlying assumption that, within species, bats with longer forearms weigh more than bats with shorter forearms. Intraspecific relationships between body mass and forearm length were very weak (R2 \u3c 0.08 in all but one case). BCI was an effective predictor of fat mass, driven entirely by the relationship between fat mass and body mass. With little variation in forearm length, calculation of BCI is essentially equivalent to dividing body mass by a constant. We evaluated alternative approaches including a scaled mass index, using tibia length, or predicting lean mass, but these alternatives were not more effective at predicting fat mass. The best predictor of fat mass in our data set was body mass. We recommend researchers stop using BCI unless it can be demonstrated the approach is effective in the context of their research

Induction of metamorphosis of pediveliger larvae of the mussel Mytilus galloprovincialis Lamarck, 1819 using neuroactive compounds, KCl, NH4Cl and organic solvents.

Pediveliger larvae of Mytilus galloprovincialis were subjected to a series of bioassays to investigate the induction of metamorphosis using neuroactive compounds, K(+), NH(4)(+) and organic solvents. Growth and survival of post-larvae obtained using ethanol and methanol were also observed. Epinephrine, phenylephrine, clonidine and metanephrine induced larval metamorphosis at 10(-6) to 10(-4) M in both 24-h and continuous exposure assays. In 24-h exposure assays, alpha-methyldopa at 5 x 10(-5) M and methoxyphenamine at 5 x 10(-5)-10(-4) M induced 55-94% metamorphosis. Similarly, excess K(+) at 3 x 10(-2) M induced 39% metamorphosis and NH(4)(+) at 1-5 x 10(-2) M induced 63-78% metamorphosis. The EC50s of seven organic solvents ranged from 0.04 to 0.82 M. Post-larvae that metamorphosed using ethanol and methanol survived as juveniles and grew at the same rate as those from microbial biofilm. Thus, the above compounds can be useful inducers of metamorphosis for antifouling studies using larvae and juveniles of M. galloprovincialis