Now showing items 1-4 of 4

    • 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

      Diet composition and feeding periodicity of the seahorse Hippocampus barbouri reared in illuminated sea cages 

      LMB Garcia, GV Hilomen-Garcia, FT Celino, TT Gonzales & RJ Maliao - Aquaculture, 2012 - Elsevier
      The zooplankton prey composition and feeding periodicity of juvenile and adult seahorses Hippocampus barbouri reared in illuminated and non-illuminated sea cages were compared. Mean frequency of occurrence (%FO), prey composition (%N), and gut fullness of seahorses were calculated from analyses of gut contents. Compared with juvenile seahorses, adults consumed more variety of prey consisting of copepods, larvae of decapods, polychaetes and fish, and euphausid shrimps. Calanoid copedods were found in the gut of more juvenile (%FO = 47) and adult (%FO = 64) seahorses in illuminated cages but harpacticoid copepods were ingested by more juvenile fish (%FO = 50) in non-illuminated cages. Decapod larvae (%N = 66) in illuminated cages dominated the diet of juvenile seahorses, whereas in non-illuminated cages harpacticoid copepods (%N = 59) did. Calanoid copepods and decapod larvae (%N = 91–97) comprised the bulk of ingested prey among adult seahorses in all experimental cages. The gut of caged seahorses was generally full during daytime but declined in the evening, becoming almost empty at midnight, particularly among juveniles. Cage illumination commencing at midnight increased the number of filled guts at dawn (0400 h) among juvenile and adult seahorses. Unlike adult seahorses over a 24-h period, the overall incidence of filled guts among juveniles was not different between those in non-illuminated and illuminated cages. These results provide an alternative to growing caged H. barbouri on cultured live food, particularly copepods attracted by night illumination.
    • Article

      Gross and fine anatomy of the respiratory vasculature of the mudskipper, Periophthalmodon schlosseri (Gobiidae: Oxudercinae) 

      TT Gonzales, M Katoh, MA Ghaffar & A Ishimatsu - Journal of Morphology, 2011 - Wiley-Blackwell
      To illustrate vascular modification accompanying transition from aquatic to amphibious life in gobies, we investigated the respiratory vasculatures of the gills and the bucco-opercular cavities in one of the most terrestrially-adapted mudskippers, Periophthalmodon schlosseri, using the corrosion casting technique. The vascular system of Pn. schlosseri retains the typical fish configuration with a serial connection of the gills and the systemic circuits, suggesting a lack of separation of O2-poor systemic venous blood and O2-rich effluent blood from the air-breathing surfaces. The gills appear to play a limited role in gas exchange, as evidenced from the sparsely-spaced short filaments and the modification of secondary lamellar vasculature into five to eight parallel channels that are larger than red blood cell size, unlike the extensive sinusoidal system seen in purely water-breathing fishes. In contrast, the epithelia of the bucco-opercular chamber, branchial arches, and leading edge of the filaments are extensively laden with capillaries having a short (<10 μm) diffusion distance, which strongly demonstrate the principal respiratory function of these surfaces. These capillaries form spiral coils of three to five turns as they approach the epithelial surface. The respiratory capillaries of the bucco-opercular chamber are supplied by efferent blood from the gills and drained by the systemic venous pathway. We also compared the degree of capillarization in the bucco-opercular epithelia of Pn. schlosseri with that of the three related intertidal-burrowing gobies (aquatic, non-air-breathing Acanthogobius hasta; aquatic, facultative air-breathing Odontamblyopus lacepedii; amphibious air-breathing Periophthalmus modestus) through histological analysis. The comparison revealed a clear trend of wider distribution of denser capillary networks in these epithelia with increasing reliance on air breathing, consistent with the highest aerial respiratory capacity of Pn. schlosseri among the four species.
    • Article

      Respiratory vasculatures of the intertidal air-breathing eel goby, Odontamblyopus lacepedii (Gobiidae: Amblyopinae) 

      TT Gonzales, K Masaya & A Ishimatsu - Environmental Biology of Fishes, 2008 - Springer Verlag
      Lacking a propensity to emerge over the mud surface, the eel goby, Odontamblyopus lacepedii, survives low tide periods by continuously breathing air in burrows filled with hypoxic water. As with most marine air-breathing fishes, O. lacepedii does not possess an accessory air-breathing organ, but holds air in the buccal-opercular cavity. The present study aimed to clarify how the respiratory vasculature has been modified in this facultative air-breathing fish. Results showed that the gills apparently lacked structural modifications for air breathing, whereas the inner epithelia of the opercula were richly vascularized. Comparison with two sympatric gobies revealed that the density of blood capillaries within 10?m from the inner opercular epithelial surface in O. lacepedii (14.5 ± 3.0 capillaries mm-1; mean ± s.d., n = 3) was significantly higher than in the aquatic non-air-breathing Acanthogobius hasta (0.0 ± 0.0) but significantly lower than in the amphibious air-breathing mudskipper, Periophthalmus modestus (59.1 ± 8.5). The opercular capillary bed was supplied predominantly by the 1st efferent branchial arteries (EBA1) and drained by the opercular veins, which open into the anterior cardinal vein. Deep invaginations at the distal end of the EBA1 and the junction with EBA2 are suggestive of blood flow regulatory sites during breath-holding and apnoeic periods. It remains to be investigated how blood flow through the gills is maintained during breath holding when the buccal–opercular cavity is filled with air.