Suction feeding is a well-understood feeding mode among macroscopic aquatic organisms. The little we know about small suction feeders from larval fish suggests that small suction feeders are not effective. Yet bladderworts, an aquatic carnivorous plant with microscopic underwater traps, have strong suction performances despite having the same mouth size as that of fish larvae. Previous experimental studies of bladderwort suction feeding have focused on the solid mechanics of the trap door’s opening mechanism rather than the mechanics of fluid flow. As flows are difficult to study in small suction feeders due to their small size and brief event durations, we combine flow visualization on bladderwort traps with measurements on a mechanical, dynamically scaled model of a suction feeder. We find that bladderwort traps generate flows that are more similar to the inertia-dominated flows of adult fish than the viscosity-dominated flows of larval fish. Our data further suggest that axial flow transects through suction flow fields, often used in biological studies to characterize suction flows, are less diagnostic of the relative contribution of inertia versus viscosity than transverse transects.

Appropriate decision‐making in conservation programmes requires an understanding of the population genetic structure of various indigenous species. However, in lake and river ecosystems rated as biodiversity conservation priority areas in the Philippines, the diversity of many species remains uncharacterized.To address the existing gap, genetic diversity of two native freshwater fishes, Glossogobius celebius (Valenciennes, 1837) and Glossogobius giuris (Hamilton, 1822) was measured. Genetic structure and estimates of genetic variation for each species was determined using isozyme analysis.A higher level of genetic variation was observed within G. celebius populations compared with G. giuris. Genetic structure indicated that the observed genetic variation in G. giuris is due to the variation among the populations. The results suggest the presence of geographical barriers even in adjacent aquatic ecosystems that could restrict gene flow among G. giuris populations.This study supports the need for immediate conservation interventions for both species as they show a low level of genetic diversity in addition to being threatened in their own environment. Possible measures include translocation and establishment of a refuge population of the species studied to be complemented with location‐specific strategies that would enhance their habitat conditions. In addition, education and enhancing the awareness of the local community regarding habitat protection are strongly recommended. Copyright © 2014 John Wiley & Sons, Ltd.