Now showing items 1-5 of 5

    • Article

      Air breathing of aquatic burrow-dwelling eel goby, Odontamblyopus lacepedii (Gobiidae: Amblyopinae) 

      TT Gonzales, M Katoh & A Ishimatsu - Journal of Experimental Biology, 2006 - Company of Biologists
      Odontamblyopus lacepedii is an eel goby that inhabits both coastal waters and intertidal zones in East Asia, including Japan. The fish excavates burrows in mudflats but, unlike the sympatric amphibious mudskippers, it does not emerge but stays in the burrows filled with hypoxic water during low tide. Endoscopic observations of the field burrows demonstrated that the fish breathed air in the burrow opening; air breathing commenced 1.3 h following burrow emersion, when water PO2 was ∼2.8 kPa, with an air-breathing frequency (fAB) of 7.3±2.9 breaths h–1 (mean ± s.d., N=5). Laboratory experiments revealed that the fish is a facultative air breather. It never breathed air in normoxic water (PO2=20.7 kPa) but started bimodal respiration when water PO2 was reduced to 1.0–3.1 kPa. The fish held air inside the mouth and probably used the gills as gas-exchange surfaces since no rich vascularization occurred in the mouth linings. As is known for other air-breathing fishes, fAB increased with decreasing water PO2. Both buccal gas volume (VB) and inspired volume (VI) were significantly correlated with body mass (Mb). At a given Mb, VI was nearly always equal to VB, implying almost complete buccal gas renewal in every breathing cycle. A temporal reduction in expired volume (VE) was probably due to a low aerial gas exchange ratio (CO2 elimination/O2 uptake). Air breathing appears to have evolved in O. lacepedii as an adaptation to aquatic hypoxia in the burrows. The acquisition of the novel respiratory capacity enables this species to stay in the burrows during low tide and extends the resident time in the mudflat, thereby increasing its chances of tapping the rich resources of the area.
    • Article

      Collection of the clam Anodontia edentula in mangrove habitats in Panay and Guimaras, central Philippines 

      JH Primavera, MJHL Lebata, LF Gustilo & JP Altamirano - Wetlands Ecology and Management, 2002 - Kluwer Academic Publishers
      The mangrove clam Anodontia edentula is highly prized in the Philippines for its flavor and large size. Because this infaunal species is found down to one meter deep in mangrove areas, harvesting the clam reportedly damages mangrove stands. To evaluate such reports, a survey of collection methods was undertaken in Panay and Guimaras, central Philippines in August 1997-December 1999. Host to chemosynthetic bacterial symbionts that utilize sulfide as energy source, A. edentula are strategically situated in sulfide-rich anoxic substrates but also gain access to oxygenated seawater through a ventilation burrow or tube. By locating the opening of this burrow, collectors can detect the presence of a buried clam and harvest it nondestructively with a blade or bare hands. In contrast, the indiscriminate tilling of wide mangrove areas can damage mangrove plants. Most collectors were 40-45 years old with 22-30 years collection experience, married with 5-7 children, and had low educational attainment. They sold clams directly in the local markets or through middlemen (to restaurants and beach resorts); sales provided from 10% to 100% of daily family income. Collectors complained of decreasing clam sizes and numbers and the physically strenuous work of collecting.
    • Article

      Gill structure, anatomy and habitat of Anodontia edentula: Evidence of endosymbiosis 

      MJHL Lebata & JH Primavera - Journal of Shellfish Research, 2001 - National Shellfisheries Association
      Surveys and interviews were conducted to determine sources and habitat of Anodontia edentula. Results showed that they inhabit muddy substrate of mangrove areas or the adjacent mudflats, burying at 20-60 cm deep in the mud. They are strategically situated in the sulfide-rich, low-oxygen layer of the substrate but have access to oxygen through their inhalant tube; both sulfide and oxygen are essential for their survival. Study of the clam s gross anatomy revealed thick, fleshy, deep purple to blackish brown gills; reduced digestive structure; and a highly elastic foot capable of extending several times longer than its body length. These observations conform with the anatomy of fellow lucinid clams. Furthermore, scanning electron micrographs showed coccoid or spherical bacteria occupying bacteriocytes in the clam s gills. Intermediate cells separating bacteriocytes observed in other lucinids were also noted in the SEM.
    • Article

      Indicators of diminished organic matter degradation potential of polychaete burrows in Philippine mariculture areas 

      SMS Santander, ML San Diego-McGlone & W Reichardt - The Philippine Agricultural Scientist, 2008 - University of the Philippines Los Baños
      Sediments from underneath fish cages and in mesocosm tanks were examined to establish indicators of diminished organic matter degradation potential of polychaete burrows from increased mariculture activities in Bolinao-Anda, Pangasinan, Philippines. Results showed that simple sediment characteristics may be used as sediment quality indicators to describe the contribution of burrows to biodegradable processes in sediments with extremely high deposition of organic particles. The indicators of diminished organic matter degradation potential of polychaete burrows are low redox potential (-113 to -150 mV for F. Spionidae and F. Eunicidae) at the 1 cm surface layer, absence or decreased size of burrow openings, presence of H sub(2)S, disappearance of apparent Redox Potential Discontinuity Layer (aRPD), formation of black sediment, and presence of Beggiatoa (sulfide oxidizing bacteria) and gas bubbles.
    • Article

      Intertidal burrows of the air-breathing eel goby, Odontamblyopus lacepedii (Gobiidae: Amblyopinae) 

      TT Gonzales, K Masaya & A Ishimatsu - Ichthyological Research, 2008 - Ichthyological Society of Japan
      Odontamblyopus lacepedii inhabits burrows in mudflats and breathes air at the surface opening. Investigations of the intertidal burrows using resin casting demonstrated a highly branched burrow system. The burrows are composed primarily of branching patterns of interconnected tunnels and shafts that communicate into two to seven surface openings. Bulbous chambers (i.e., dilated portions of the burrow) at branching sections of the tunnels or shafts are common features of the burrow. The presence of these chambers accords the fish adequate space to maneuver inside the burrow, and thus constant access to the surface. The combination of all burrow characteristics and previously reported variability in air breathing patterns are ostensibly of selective value for aerial predator avoidance during air breathing in O. lacepedii.