Now showing items 413-432 of 1065

    • Article

      GABA enhances reproduction of the rotifer Brachionus plicatilis Muller: application to mass culture 

      WG Gallardo, A Hagiwara & TW Snell - Aquaculture Research, 2000 - Wiley-Blackwell
      Based on the results of individual and batch culture experiments in small volumes, we conducted experiments in larger volumes of 100 mL, 1 L and 10 L to determine: (1) at what phase of population growth would gamma-aminobutyric acid (GABA) treatment be most effective; and (2) whether GABA treatment of concentrated rotifers for several hours before mass culture would also be effective. GABA treatment of rotifer cultures at lag phase significantly enhanced population growth, whereas treatment at log phase had a lesser effect, and treatment at stationary phase had no effect. Addition of GABA to rotifer cultures every 2 days hastened population growth until day 8, but resulted in culture collapse thereafter. To reduce the cost of the use of GABA in mass cultures, GABA treatment may be conducted on concentrated rotifers (100 individuals mL−1) before mass culture. GABA treatment of concentrated rotifers for 24 h and 48 h before mass culture resulted in a significantly higher population density compared with their respective controls (no GABA treatment) on day 4, and on days 4 and 6 respectively.
    • Article

      GABA, 5-HT and amino acids in the rotifers Brachionus plicatilis and Brachionus rotundiformis 

      WG Gallardo, A Hagiwara, K Hara, K Soyano & TW Snell - Comparative Biochemistry and Physiology - Part A: Molecular and Integrative Physiology, 2000 - Elsevier
      γ-Aminobutyric acid (GABA) and 5-hydroxytryptamine (5-HT) have been shown to increase the reproduction of the Brachionus plicatilis (NH3L strain). In the present study, the endogenous presence of GABA and 5-HT in the rotifers B. plicatilis (NH3L and Kamiura strains) and Brachionus rotundiformis (Langkawi strain) were confirmed by dot blot immunoassay and high-performance liquid chromatography (HPLC). HPLC showed that GABA and 5-HT concentrations in the three rotifer strains range from 71 to 188 pmol/mg and from 12 to 64 pmol/mg, respectively. A total of 33 amino acids were also detected in B. plicatilis and B. rotundiformis, with glutamic acid, serine, glycine, taurine, threonine, alanine, arginine, proline, valine and isoleucine in high concentrations relative to other amino acids.
    • Article

      Gathering of economically important seaweeds in Western Visayas, Philippines 

      AQ Hurtado-Ponce, MRJ Luhan & NG Guanzon Jr. - The Philippine Scientist, 1992 - San Carlos Publications
      A survey was conducted in 12 coastal municipalities of Western Visayas, Philippines from March to July 1990 to determine the seaweed gathering practices of fishermen. There were 83 gatherers involved in this small-scale industry, who live below the poverty line and who consider it as the number one minor source of income. Only seaweeds of commercial value are gathered in big volume. There were approximately 114 T year-1 of seaweeds harvested from natural stock with a market value of P414, 950.00 ($14,819.64). The harvest is broken down into 3 main groups: (1) agarophytes, 99.5 T (Gelidiella, Gracilaria and Gracilariopsis), (2) carrageenophytes, 10 T (Eucheuma and Kappaphycus) and (3) table vegetable, 10 T (Caulerpa). An average maximum income of P5,600.00 or $200 gatherer-1 season-1 is derived from seaweed gathering.
    • Article

      Genetic assessment of milkfish (Chanos chanos Forsskal) stocks based on novel short tandem repeats for marker-aided broodstock management 

      MRR Romana-Eguia, BS Santos, M Ikeda, ZU Basiao & A Kijima - Aquaculture Research, 2018 - John Wiley and Sons
      Milkfish hatchery broodstock are either from on-grown wild-caught or hatchery-produced fry/juveniles. To determine if a marker-assisted management scheme can be formulated for improved milkfish hatchery production, milkfish stocks were genetically characterized using nine novel short tandem repeats or microsatellites. Eight wild-bred Philippine stocks (CLA, CUR, CAM, SIH, SBH-I1, HH, PAL and ZH-P0), four hatchery-bred stocks (SBH-I2, SBH-D, BoH and ZH-F1), two farm stocks of known mixed lineages (SPH and BDH) and one Indonesian hatchery-bred stock (WJH) were assessed. WJH was included since milkfish fingerlings from Indonesia reared in Philippine farms could be developed into future broodstock. Mean allelic richness (Ar) was highest in wild-bred stocks (9.5) and lowest in hatchery-bred spawners (9.1). Mean expected heterozygosities (He) were relatively similar in all stocks with wild-bred stocks slightly higher (0.67) than the others. An analysis of molecular variance indicated significant yet low genetic differentiation among stocks (FST = 0.013; p = .000) where variation (98.6%) was explained by intra-stock differences. In some of the domesticated stocks, reductions in mean allelic richness were observed in first generation hatchery broodstock (e.g. ZH-F1; Ar = 8.3), compared with their founder stock (e.g. ZH-P0; Ar = 9.4). The Indonesian stock was similar to local wild-bred stocks based on genetic variability indices; thus, it might be likely that the local stocks’ fitness traits could be comparable with the imported milkfish stock which has been perceived to be better. The quality of locally available farmed milkfish and prospects of formulating a broodstock management scheme for the production of good quality milkfish seedstock are herewith discussed.
    • Article

      Genetic changes during mass selection for growth in Nile tilapia, Oreochromis niloticus (L.), assessed by microsatellites 

      MRR Romana-Eguia, M Ikeda, ZU Basiao & N Taniguchi - Aquaculture Research, 2005 - Blackwell Publishing
      Two control (C1 or first control generation, and C4 or fourth control generation) and three selected (S1 or first selected generation, S2 or second selected generation, S4 or fourth selected generation) stocks of Chitralada Nile tilapia were analysed for microsatellite variation to determine the effect of size-specific mass selection on genetic variability. Genetic variation based on five microsatellite loci (UNH123, UNH147, UNH172, UNH222 and UNH216) showed a slightly higher allelic diversity in the selected stocks (7.4–10 alleles) than in the control stocks (6.8–8.8 alleles). Apparent reductions in the mean number of alleles and He values were noted in successive generations of both control and selected lines. Significant deviations from Hardy–Weinberg equilibrium because of an excess of homozygotes indicated inbreeding in all control and selected stocks. Although estimated inbreeding levels were not significantly different among selected and control lines based on Welch's t-tests, the increase in the degree of inbreeding within the selected line was higher (107.9%) than the control line (64.2%) after four generations. The implications of these results on the management and conservation of genetic diversity in improved breeds are discussed, while the importance of monitoring and minimizing inbreeding are likewise emphasized.
    • Article

      Genetic diversity in farmed Asian Nile and red hybrid tilapia stocks evaluated from microsatellite and mitochondrial DNA analysis 

      MRR Romana-Eguia, M Ikeda, ZU Basiao & N Taniguchi - Aquaculture, 2004 - Elsevier
      We analyzed microsatellite and mitochondrial DNA restriction fragment length polymorphism (mtDNA-RFLP) in two domesticated (NIFI and Israel) and four genetically improved (GIFT, GMT, FAC-selected and SEAFDEC-selected) Nile tilapia (Oreochromis niloticus) as well as five red hybrid tilapia (Oreochromis mossambicus × O. niloticus) stocks (BFS, FACred, NIFIred, HL, and PF) farmed in Asia. Microsatellite variation at five loci (UNH216, UNH172, UNH123, UNH147, UNH222) was more informative in characterizing stock differences than the mtDNA-RFLP markers that were based only on 14 restriction morphs. Contemporary microsatellite data showed that GIFT Nile tilapia had the highest mean expected heterozygosity (H>e=0.813), while GMT had the lowest (He=0.666). The unselected NIFI stock and SEAFDEC-selected were genetically similar, while GMT differed significantly from the other Nile tilapia stocks. Among the red tilapias, NIFIred had the highest He (0.715), while BFS had the lowest variability (He=0.567). The Taiwanese red tilapia HL and Thai NIFIred were genetically similar. Except for NIFI, most of the Nile and red tilapia stocks exhibited remarkably significant homozygote excess relative to Hardy–Weinberg Equilibrium (HWE), suggesting some degree of inbreeding. Asian Nile tilapias were more genetically diverse (pooled He=0.791; mtDNA nucleotide divergence value dA=0.009) than the red tilapias (pooled He=0.697; mean dA=0.004). This slight divergence between the Nile and red tilapias was also seen in the analysis of molecular variance (AMOVA; FCT=0.0018) and in genetic distance and nucleotide divergence dendrograms. However, the AMOVA revealed that the greater percentage of variation (99.33%) in the total genetic diversity of the surveyed stocks is principally due to differences at the individual level and not between nor within groups. The significance of these results is that they reflect and lead to new inferences regarding the selective breeding and culture methods used in managing these farmed stocks.
    • Article

      Genetic diversity of wild and cultured Black Tiger Shrimp (Penaeus monodon) in the Philippines using microsatellites 

      Z Xu, JH Primavera, LD de la Peña, P Pettit, J Belak & A Alcivar-Warren - Aquaculture, 2001 - Elsevier
      Six microsatellites were used to study (1) the genetic diversity of wild Penaeus monodon shrimp from four geographic regions (Palawan, Quezon, Capiz and Negros Occidental-W) in the Philippines, and (2) its association with the status of mangroves and intensity of shrimp culture systems in these regions. Two cultured populations (Negros Occidental-C and Antique) were used for comparison. All six microsatellite loci were polymorphic. A total of 184 different alleles were found over all loci. The total number of alleles per locus ranged from 6 to 54, with allele size ranging from 159 base pairs (bp) to 400 bp. The observed heterozygosity of the six loci ranged from 0.47 to 1.00. The number of genotypes per locus ranged from 5 to 70. Fst values showed significant genetic differentiation among the four wild populations. Genetic differences between wild populations were also detected by pairwise comparison based on genotypic and allelic frequencies. Genetic differentiation among wild populations exhibited a positive correlation with mangrove status and intensity of culture systems at P=0.083. The Negros Occidental-W population, which originated from an area with the most severe mangrove loss and the most intensive culture systems, was the most significantly differentiated population. It also showed less genotypes per locus than the other three wild populations, suggesting a decrease in genetic diversity in this population. The population from Capiz, a province with a wide area of extensive culture ponds and few remaining secondary mangroves was the second most differentiated population. The Quezon population, which originated from an area with a few extensive culture ponds and less mangrove destruction, was not genetically different from the Palawan population, which was from a pristine site with mostly primary mangroves and no major aquaculture industry. The cultured populations showed less genetic diversity and were significantly different from the four wild populations based on pairwise Fst values and pairwise comparisons of allelic and genotypic frequencies. The results suggest that (a) there was a significant genetic differentiation among the wild P. monodon populations in the Philippines, and (b) the cultured populations were significantly differentiated from the natural populations. More replicate samples from each of the geographic regions are needed to conclusively determine the possibility of an association between genetic differentiation and the status of mangroves and/or intensity of shrimp culture systems.
    • Article

      Genomic polymorphism in symbiotic populations of Photobacterium leiognathi 

      PV Dunlap, A Jiemjit, JC Ast, MM Pearce, RR Marques & CR Lavilla-Pitogo - Environmental Microbiology, 2004 - Blackwell Publishing
      Photobacterium leiognathi forms a bioluminescent symbiosis with leiognathid fishes, colonizing the internal light organ of the fish and providing its host with light used in bioluminescence displays. Strains symbiotic with different species of the fish exhibit substantial phenotypic differences in symbiosis and in culture, including differences in 2-D PAGE protein patterns and profiles of indigenous plasmids. To determine if such differences might reflect a genetically based symbiont-strain/host-species specificity, we profiled the genomes of P. leiognathi strains from leiognathid fishes using PFGE. Individual strains from 10 species of leiognathid fishes exhibited substantial genomic polymorphism, with no obvious similarity among strains; these strains were nonetheless identified as P. leiognathi by 16S rDNA sequence analysis. Profiling of multiple strains from individual host specimens revealed an oligoclonal structure to the symbiont populations; typically one or two genomotypes dominated each population. However, analysis of multiple strains from multiple specimens of the same host species, to determine if the same strain types consistently colonize a host species, demonstrated substantial heterogeneity, with the same genomotype only rarely observed among the symbiont populations of different specimens of the same host species. Colonization of the leiognathid light organ to initiate the symbiosis therefore is likely to be oliogoclonal, and specificity of the P. leiognathi/leiognathid fish symbiosis apparently is maintained at the bacterial species level rather than at the level of individual, genomotypically defined strain types.
    • Article

      Genotype environment interaction in the response of three strains of Nile tilapia to poor nutrition 

      MRR Romana-Eguia & RW Doyle - Aquaculture, 1992 - Elsevier
      Experiments were conducted to determine the effects of poor nutrition on the growth of three Oreochromis niloticus strains fed protein-deficient diets. Four-week-old fry from the three "test" strains were paired with a fourth "reference" strain of tilapia (red) of the same size and stocked in 60-1 aquaria. The treatment lasted 6 weeks, with fish being fed commercial fish feed crumbles for the first and last 2-week periods and rice bran during weeks 3 and 4. Control fish were fed commercial diet throughout. Both control and treatment fish were fed at 20% of fish biomass per day. Lengths and weights were measured every 2 weeks.

      Significant strain effects were noted when the growth of test fish over the whole experimental period was analysed by analysis of covariance using the reference fish growth as a concomitant variable. The relative growth of the three test strains differed at each feeding phase. The NIFI strain grew best during the commercial feed phases, the Israel strain performed best during the rice bran phase while the CLSU strain, regardless of the type of nutritional environment, usually ranked last. Different performance rankings at each feeding phase represent strong genotype X environment interaction among these commercially important lines. This was statistically confirmed by analysis of covariance of the growth of the Israel and NIFI strains during the different feeding phases using the reference strain as a covariate.
    • Article

      The genus Gracilariopsis (Rhodophyta, Gracilariales) in the Philippines: morphological and taxonomic confirmations 

      AQ Hurtado-Ponce & LM Liao - The Philippine Scientist, 1998 - University of San Carlos
      Reports of the economically-important agarophytic seaweed genus Gracilariopsis Dawson from Philippine waters are verified for the first time. Cystocarpic, spermatangial and tetrasporic materials collected from various localities in eastern Panay and northwestern Negros islands conform to the circumscription of this recently reinstated genus. Materials are referred to Gracilariopsis heteroclada Zhang & Xia after morphological comparisons with type materials from southern China. In addition, a discussion of the complicated nomenclatural history of this species is included.

      Another putative Gracilariopsis species is reported from Zamboanga City based on cystocarpic materials alone. This species differs from G. heteroclada with its smaller gonimoblast cells and larger height:width ratio of the gonimoblast mass. Vegetatively, the thallus is smooth, devoid of fine, determinate branchlets observed in G. heteroclada.
    • Article

      Gill lesions associated with acute exposure to ammonia. 

      ER Cruz & GL Enriquez - Natural and Applied Science Bulletin, 1982 - University of the Philippines
      The histopathological effects of the 96 hr LC50 at 20.65 ppm NH3-N on the gills of milkfish fingerlings were examined qualitatively. Lesions observed were hypertrophy, hyperplasia, fusion of the lamellae, epithelial lifting, lamellar telangiectasis, disruption of the epithelial layer, lamellar detachment, vacuolation of the lamellae and the blood cells, and presence of several mitotic cells. The physiology of the histopathological lesions observed is discussed.
    • Article

      Gill lesions in Nile tilapia Oreochromis fingerling associated with acute malathion poisoning. 

      EC Capinpin - Philippine Journal of Science, 1994 - Science and Technology Information Institute
      The hispathological changes in gills of Nile tilapia, Oreochromis niloticus, fingerlings exposed to 5.3 mg/l (96-h LC50) malathion are described. These changes include hypertrophy of epithelial cells after 3 h, epithelial lifting and destruction of the structural integrity of some lamellae after 24 h, multifocal fusion of adjacent lamellae after 72 h, and diffused epithelial lifting after 96 h. Partial to complete recovery was observed in gills after rearing in malathion-free water for 6. to 12 d.
    • 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

      Gonad development and size‐at‐maturity of silver therapon Leiopotherapon plumbeus (Kner 1864; Teleostei:Terapontidae) in tropical volcanic lakes in south Luzon, Philippines 

      PJT Denusta, EG de Jesus-Ayson, MA Laron, FA Aya & LMB Garcia - Journal of Applied Ichthyology, 2019 - Wiley
      Gonad development of the silver therapon Leiopotherapon plumbeus in two volcanic crater lake habitats (Sampaloc Lake, Taal Lake) in south Luzon, Philippines was examined during the annual reproductive cycle. The minimum body size‐at‐maturity of fish in these two lake habitats was also compared. Four gonad development stages were characterized as basis for the classification of ovarian (immature, maturing, mature, spawned) and testicular maturation (immature, maturing, mature) phases. The occurrence of all development stages in individual gonads suggest an asynchronous development whereby advanced stages are recruited continuously from a pool of younger stage germ cells to result in elevated female and male GSI throughout the annual cycle due to active gonadogenesis. Together with the increasing occurrence of advanced stage oocytes and spermatozoa from March until October, the elevated GSI of fish may indicate peak gonadal growth during the onset of the dry season (December–January) for eventual spawning from the beginning (May–June) until the end of the wet season (October–November). In both lake habitats, male fish were smaller than females but, regardless of sex, the minimum size‐at‐maturity of fish in Sampaloc Lake was significantly smaller than fish in Taal Lake. Overall, asynchronous development during oogenesis and spermatogenesis allows for year‐round reproduction of silver therapon, with elevated gonad growth in the dry season in preparation for spawning during the wet season. Compared with fish in Taal Lake, a smaller size‐at‐maturity of fish in Sampaloc Lake may be a response of the wild fishery stock to long‐term high fishing mortality and degradation of the lake habitat.
    • Article

      Gonad development of Placuna placenta Linnaeus fed Isochrysis galbana Parke, Tetraselmis tetrahele (G.S. West) Butch, or their combination 

      WG Gallardo, MTR de Castro, RT Buensuceso, CC Espegadera & CC Baylon - Aquaculture, 1992 - Elsevier
      A study was conducted to determine a suitable algal diet for the window-pane oyster, Placuna placenta Linnaeus, during gonad development. Sexually immature P. placenta (70 mm shell height) were fed Isochrysis galbana Parke, Tetraselmis tetrahele (G.S. West) Butch, or their 1:1 combination, at 100 000 cells per ml divided into two rations per day. Temperature and salinity ranged from 27 to 29 °C and 28 to 32 ppt, respectively. Monthly gonad histological examination showed a rapid gonad development in P. placenta fed the combination of I. galbana and T. tetrahele, attaining sexual maturity in the third month of rearing, a month ahead of those fed single algal species.
    • Article

      Gonadal maturation, fecundity, spawning and timing of reproduction in the mud snail, Cerithidea cingulata, a pest in milkfish ponds in the Philippines 

      I Lantin-Olaguer & TU Bagarinao - Invertebrate Reproduction and Development, 2001 - Taylor & Francis
      Gonadal maturation, spawning, fecundity and timing of reproduction of the snail Cerithidea cingulata in a brackish water pond in Molo, Iloilo, Philippines, are described. Snails 4–41 mm in shell length were sampled monthly from May 1997 to May 1998; 25% were <25 mm, 67% were 20–30 mm, and 8% were >30 mm. The sexes are separate and could first be distinguished at 15 mm. Males are aphallic, have narrower shells than females of the same length, and have bright yellow-orange testes overlying the digestive gland deep inside the shell. Females have more robust shells, an ovipositor at the right side of the foot, and yellow-green ovaries overlying the digestive gland. The sex ratio was one male to two females in the pond population studied. Gonadal maturation was monitored by means of gonadosomatic index (GSI, gonad weight as a percent of visceral weight); maturation stages were based on the gonad appearance (immature, developing, mature) and histology (immature, developing, mature, redeveloping). GSI increased with snail size, and reached 16% in a 33-mm female. The smallest mature males and females were 18–19 mm, and most snails >20 mm were mature, spawning, or redeveloping. Histological sections showed all stages of gametogenesis in mature male snails. The oocyte size-frequency distributions in mature females showed mostly mature oocytes and secondary oocytes, but also oogonia and primary oocytes. GSI and the frequency of snails at different maturation stages varied over the year. Both GSI and the frequency of mature snails were highest during the summer months, April to August. Nevertheless, mature snails occurred throughout the whole year, as did mating and egg-laying. Fecundity (= number of oocytes >70 pμ) increased with size in mature females 2041 mm; an average 25-mm female produced about 1,500 oocytes and larger females produced a maximum of about 2,500 oocytes. Eggs strings laid on the pond bottom were 45–75 mm long; an average 64-mm string contained 2,000 eggs 210+20 pm in diameter. The density of eggs strings was highest (80–120/m2) during March-September. Eggs hatched after 6–7 d into planktonic veligers, which in turn settle on the pond bottom 11–12 d later as juveniles. Juveniles 2–6-mm long were most abundant in the pond during August-October.
    • Article

      Gonadal response of juvenile protogynous grouper (Epinephelus fuscoguttatus) to long term recombinant follicle-stimulating hormone administration 

      P Palma, J Nocillado, J Superio, EGdJ Ayson, F Ayson, I Bar & A Elizur - Biology of Reproduction, 2019 - Oxford University Press
      The role of follicle stimulating hormone (FSH) in the gonadal development of protogynous hermaphroditic grouper (E. fuscoguttatus) was investigated. Recombinant giant grouper (E. lanceolatus) FSH (rggFSH) was produced in yeast. Its receptor binding capacity and steroidogenic potency were confirmed in vitro. Weekly injections of rggFSH to juvenile tiger grouper for 8 weeks (100 μg/kg body weight, BW) resulted in significantly larger and more advanced oocytes (cortical alveolar stage vs. primary growth stage in control). Sustained treatment with rggFSH (20 to 38 weeks at 200 μg/kg BW) resulted in significant reduction in gonad size, degeneration of oocytes and proliferation of spermatogonial cells, indicative of female to male sex change. Gene expression analysis showed that, while initiating female to male sex change, the rggFSH significantly suppressed the steroidogenic genes cyp11b, cyp19a1a and foxl2 which restrained the endogenous production of sex steroid hormones thus prevented the differentiation of spermatogonial cells. Expression profile of sex markers dmrt1, amh, figla and bmp15 suggests that the observed sex change was restricted at the initiation stage. Based on these results, we propose that the process of female to male sex change in the protogynous grouper is initiated by FSH, rather than sex steroids and likely involves steroid-independent pathway. The cortical alveolar stage in oocyte development is the critical point after which FSH-induced sex change is possible in grouper.
    • Article

      Gonadotropin profiles in serum of milkfish treated with salmon pituitary homogenate 

      CL Marte & LW Crim - Kalikasan, The Journal of Philippine Biology, 1983 - University of the Philippines Los Baños
      Serum gonadotropin (GtH) levels were determined by radioimmunoassay (RIA) in adult regressed milkfish injected or implanted with various doses of salmon pituitary homogenate (SPH). Gonadotropin profiles of injected or implanted milkfish show similar trends. Elevation of serum GtH occurred a day after treatment in all groups irrespective of the administered dose. The level dropped after 2 or 3 days and in the implanted fish, was at the initial level 10 days after treatment. The expected slow and sustained release of hormone from the SPH pellet was not obtained even at the high dose given.

      A preliminary investigation of the milkfish pituitary homogenate using the salmon-GtH-RIA system shows no cross reaction of milkfish GtH with salmon GtH antibody, indicating that the milkfish and salmon gonadotropins are immunologically distinct molecules.
    • Article

      Gracilaria (Rhodophyta) farming in Panay, Western Visayas, Philippines 

      AQ Hurtado-Ponce, GPB Samonte, MRJ Luhan & NG Guanzon Jr. - Aquaculture, 1992 - Elsevier
      Interviews were conducted among eight Gracilaria growers in Panay, Western Visayas, Philippines from March to July (1990) using a structured questionnaire. The "rice planting" method was employed by farmers growing seaweeds in natural drainage canals and ponds. Initial harvests are made 15–60 days after planting. Higher production [ 7–14 t (dry) ha−1 year−1] are obtained from cultures in canals than in ponds [3–4 t (dry) ha−1 year−1]. The net income derived from culture in ponds is estimated at P698/crop or P6313/year (US$234/year). A higher net income of P4936/crop or P41766/year (US$1547/year) was generated from Gracilaria farming in canals. Returns on investment (ROI) from farming in ponds and canals are 39% and 908%, respectively. Payback period is 2 months in canal farming and 1.8 years in pond farming.
    • 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.