Ontogenetic Shifts in Oxygen Uptake in Common Mudskipper (Periophthalmus kalolo) and its Role in Microhabitat Selection

Abstract

Aims: The common mudskipper, Periophthalmus kalolo is a tropical, amphibious fish that utilizes both air and water as a respiratory medium. Adult oxygen uptake in water and air is well studied, but requirements of post-metamorphosed fish are virtually unknown. Our study quantifies how ontogenetic shifts across mudskipper life stage affects microhabitat choice.
 Study Design: metabolic rates in air and water were estimated for common mudskippers with mass values from 0.03 to 28.9 grams. Fish in each media were divided into 5 standard length classes (≤ 2.00, 2.01-4.00, 4.01-6.00, 6.01-8.00, ≥ 8.01 cm). Oxygen consumption for each class was calculated as the mean individual oxygen consumption for the group.
 Place and Duration of Study: Hoga Research Laboratory, Wakatobi National Park, Sulawesi, Indonesia, between June 14 and August 26, 2005.
 Methodology: Gilson manometry, and flow-through respirometery was used to determine respective aerial and aquatic oxygen uptake values for common mudskippers.
 Results: Mudskipper lengths varied by an order of magnitude (1.0 to 10.3 cm) and mass varied by three orders of magnitude (0.03 to 17.3 g). Mass-adjusted aerial metabolic rates of fish 2.00 cm or less in length, consumed up to ten times more oxygen than larger fish. whereas, aerial consumption values for size classes 2.01 cm and above did not differ significantly from each other (ANOVA: F4,112 = 40.29, P < 0.0001; SNK, α = 0.05).
 Metabolic rates of submerged fish fell into two statistically distinct subsets. mudskippers with lengths of 4.00 cm or less had significantly higher metabolic rates than fish in remaining size classes; however, mean oxygen uptake values of fish within subsets did not differ significantly (ANOVA: F4,87 = 6.89, P < 0.0001; SNK, α = 0.05). When oxygen consumption values at each size class were compared, only the smallest mudskipper size class (£ 2.00 cm) differed significantly between air and water (t-test: df = 34, t = 3.44, P < 0.0001). Mudskippers 2 cm in standard length or smaller consumed over seven times more oxygen in air than water. All other size classes had similar rates of oxygen uptake in air and water and air:water oxygen uptake ratios fell to approximately 1:1.
 Conclusions: (1) Common mudskippers select different mangal habitats based on developmental life stage. (2) Small, post-metamorphosed fish <2 mm in standard length, prefer cool shaded mangal areas, whereas, larger mudskippers utilize sun-exposed zones.
 (3) Post-metamorphosed fish, consume 10X more oxygen than all other size groups, confirming that juveniles are well suited to aerial respiration oxygen shortly after hatching. (4) Emerged post-metamorphosed fish exploit cooler, wetter pool habitats, thereby ameliorating problems of desiccation, excretion, and/or predation. (5) Ontogenetic shifts are a key life-history event in P. kalolo that promotes wider mangrove habitat use, and plays an important role in establishing common mudskipper as a key mangal species.