Now showing items 1-20 of 21

    • 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

      Clearance rates and ingestion efficiency of the Japanese scallop Patinopecten yessoensis 

      FA Aya, Y Hidaka & I Kudo - Plankton and Benthos Research, 2013 - Plankton Society of Japan
      In coastal ecosystems, variations in food quantity may have significant effects on the clearance and ingestion rates of suspension-feeding bivalves. In this study, clearance rates and ingestion efficiencies were determined for Japanese scallop (Patinopecten yessoensis) juveniles (60.6±4.5 mm in shell height) under laboratory conditions. Scallops were kept individually in glass beakers at 15°C and fed with different cell numbers of Pavlova sp. (0.8 to 57.60×106 cells) to provide a wide range of food quantity as particulate organic carbon (POC). Clearance rates (CR) and ingestion efficiencies (IE) were estimated by monitoring POC concentration over a two-day period, and from 2 to 14 days of feeding, respectively. Both CR and IE were significantly influenced by POC concentration. CR ranged from 15.8 to 38.5 mL ind-1 h-1 (or 8.9 to 49.6 mg Ch-1 g dry weight-1) with maximum values at high POC concentrations. IE varied from 40 to 71% and differed significantly between the lowest (2,900 μg C L-1) and highest (8,000 μg C L-1) food rations. The feeding response of juvenile scallops to different POC concentrations was fitted to a power curve equation: IE (%)=0.9272×POC0.5105, r=0.98. Extrapolated field-based estimates of IE ranged from 7.8 to 12.7% in response to seasonal changes in POC concentration (64.5 to 168.6 μg C L-1). It is concluded that particle filtration rates by juvenile scallops are related to food quantity, as suggested by both field and laboratory-derived feeding rates.
    • Article

      A comparison of the annual changes in testicular activity and serum androgen levels between the early and delayed maturing groups of male Cottus hangiongensis 

      GF Quinitio, A Goto & H Takahashi - Environmental Biology of Fishes, 1992 - Springer Verlag
      Annual changes in testicular activity and concentration of two serum androgens were monitored in two groups of the river-sculpin Cottus hangiongensis collected from the upper and lower reaches of a river at southern Hokkaido, Japan. One of them (early maturing group) underwent testicular maturation with aberrant spermatids and spermatid masses produced during the reproductive cycle. Moreover, regular seasonal changes in serum testosterone and 11-ketotestosterone concentrations were observed. On the other hand, in the other group (delayed maturing group), although body size of the fish was large enough to undergo reproduction, annual changes in gonadosomatic index and testicular activity did not vary much. During the months of active testicular development in the early maturing group, spermatogenesis was observed to begin in some regions of the testes of delayed maturing fish, but always resulted in the formation of aberrant spermatids and spermatid masses. Moreover, concentration of serum androgens did not significantly vary throughout the year. Results suggest that low androgen production is a proximal factor for delayed sexual maturity in the delayed maturing group, and that the occurrence of aberrant spermatids and spermatid masses during spermatogenesis is not linked to the delayed maturity.
    • Article

      Distribution of an oxytetracycline resistance determinant tet(34) among marine bacterial isolates of a Vibrio species 

      SR Kim, L Nonaka, MJ Oh, CR Lavilla-Pitogo & S Suzuki - Microbes and Environments, 2003 - Nakanishi Printing Co
      The distribution of tet(34) was examined among oxytetracycline (OTC) resistant Vibrio strains isolated from Japan, Korea and the Philippines. tet(34) was detected in 10 isolates (6 in fish, 4 in seawater) from Japan and Korea, suggesting that it is widely distributed among fish and seawater bacteria in these countries. Ninety-eight percent of the Vibrio strains in the Philippines were sensitive to OTC, but none of the 60 isolates from the Philippines. The minimum inhibitory concentration (MIC) of OTC-resistant isolates increased 2 to 8 fold in the presence of Mg2+, and MICs were higher in the Japanese and Korean isolates than the Philippine isolates. The MIC for furaltadone (FD) was low in Japanese (23.9%) isolates at over 3.1 μg/ml and high in Korean (50%) and Philippine (56.7%) isolates. This was probably due to the different frequency of use of FD in these countries. Sequences of 16S rDNA of tet(34)-positive isolates were 100% identical, suggesting that tet(34) is conveyed in a particular Vibrio species.
    • Article

      Euryhaline rotifer Proales similis as initial live food for rearing fish with small mouth 

      A Hagiwara, S Wullur, HS Marcial, N Hirai & Y Sakakura - Aquaculture, 2014 - Elsevier
      The SS-type rotifer Brachionus rotundiformis is a common initial food for rearing fish larvae with a small mouth. However, there are commercially important fish species whose mouth sizes are too small to feed on SS-type rotifers. In 2004, we isolated a small (body length = 82.7 ± 10.9 μm; body width 40.5 ± 6.4 μm), flexible, and iloricate rotifer, Proales similis from an estuary in Okinawa, Japan. Under laboratory conditions (25 °C, 2–25 ppt) P. similis produced its first offspring on 2.5 to 2.8 days after hatching, and produced 4.3 to 7.8 offspring within 4.0 to 4.7 days life span. Batch cultured P. similis fed Nannochloropsis oculata suspension at 28.8 μg dry weight ml− 1 and cultured at 25 °C, 25 ppt filtered seawater, increased exponentially from 25 to 2400 ind ml− 1 after 11 days of culture with an overall intrinsic rate of natural increase (r) of 0.42 day− 1. The growth rate of P. similis was not significantly different when fed fresh N. oculata and super fresh Chlorella vulgaris-V12®. Total lipid per wet weight of P. similis fed by N. oculata and C. vulgaris were 2.4 and 2.6%, respectively. The compositions of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and arachidonic acid (ARA) of P. similis fed N. oculata were 23.2, 0.0 and 5.3%, respectively, while these were 11.0, 17.5 and 0.5% respectively, when fed C. vulgaris. The use of P. similis to feed small mouth fish including seven-band grouper Epinephelus septemfasciatus, rusty angelfish Centropyge ferrugata, and humphead wrasse Cheilinus undulatus showed that it is an excellent starter food for these species because of their high selectivity index and improved survival. In addition, P. similis was ingested by Japanese eel Anguilla japonica larvae with a complicated digestive system. The use of P. similis as starter feed for small mouth fish larvae is highly recommended.
    • magazineArticle

      Exclusive fishing rights in Japan 

      Southeast Asian Fisheries Development Center, Aquaculture Department - Aqua Farm News, 1993 - Aquaculture Department, Southeast Asian Fisheries Development Center
    • Article

      Immune responses of Asian sea bass, Lates calcarifer Bloch, against an inactivated betanodavirus vaccine 

      RV Pakingking Jr., R Seron, LD de la Peña, K Mori, H Yamashita & T Nakai - Journal of Fish Diseases, 2009 - Blackwell Publishing
      Asian sea bass, Lates calcarifer (Bloch), exhibited strong immune responses against a single injection of the formalin-inactivated red-spotted grouper nervous necrosis virus (RGNNV), a betanodavirus originally isolated in Japan. Fish produced neutralizing antibodies at high titre levels from days 10 (mean titre 1:480) to 116 (1:1280), with the highest titre at day 60 post-vaccination (1:4480). When fish were challenged with the homologous RGNNV at day 54 post-vaccination, there were no mortalities in both the vaccinated and unvaccinated control fish. However, a rapid clearance of the virus was observed in the brains and kidneys of vaccinated fish, followed by a significant increase in neutralizing-antibody titres. Furthermore, the vaccine-induced antibodies potently neutralized Philippine betanodavirus isolates (RGNNV) in a cross-neutralization assay. The present results indicate the potential of the formalin-inactivated RGNNV vaccine against viral nervous necrosis (VNN) of Asian seabass.
    • Conference paper

      Important diseases and practical control measures in shrimp culture in Japan 

      K Yuasa, T Mekata & J Sato - In RV Pakingking Jr., EGT de Jesus-Ayson & BO Acosta (Eds.), Addressing Acute Hepatopancreatic Necrosis Disease (AHPND) and Other Transboundary Diseases for Improved Aquatic … Diseases for Improved Aquatic Animal Health in Southeast Asia, 22-24 February 2016, Makati City, Philippines, 2016 - Aquaculture Department, Southeast Asian Fisheries Development Center
      The gross product from sea culture in Japan was about USD 3.4 billion in 2013 with kuruma shrimp Marsupenaeus japonicus constituting 2% of the total production. In recent years, annual shrimp production has reached about 1,600 metric tons (MT) and 99% of the species produced comprised of M. japonicus. Kuruma shrimp is highly traded at market price of USD 40-60 per kg. At present, 65% of cultured kuruma shrimp are produced in Okinawa and Kagoshima prefectures. To increase or maintain kuruma shrimp fishery in the natural environment, 200 million fry have been annually released into the sea along the coast of Japan. In addition, whiteleg shrimp Penaeus vannamei has also been produced in a private farm since 2007 with an annual production of approximately 40 MT. Recently, the number of farms that ventured into whiteleg shrimp culture has increased.

      The most serious obstacle faced by the kuruma shrimp industry in Japan in the 1990s was the outbreaks of white spot disease (WSD) caused by white spot syndrome virus (WSSV). The seed production of kuruma shrimp has been dependent on captured wild broodstocks. However, broodstocks obtained from the wild could be carriers of WSSV that may vertically transmit the virus to fertilized eggs. To prevent the spread of WSD, measures for disinfecting WSSV-infected fertilized eggs of shrimp and detection of the causative virus by polymerase chain reaction (PCR) have been developed. Lately, with the application of an improved technology for broodstock rearing, production losses ascribed to WSD have significantly decreased because majority of the hatcheries have been using specific WSSV-free shrimps.

      In the last decade, in kuruma shrimp hatcheries and grow-out ponds, vibriosis due to Vibrio penaeicida has been frequently encountered. Fusariosis caused by Fusarium solani is also common. The first cases of vibriosis and fusariosis in Japan occurred in 1973 and 1972, respectively. Taking the case of Okinawa prefecture as example, production losses in 2005 due to vibriosis and fusariosis were 66% and 34%, respectively. Cleaning of the pond bottom prior to the commencement of grow-out culture has been recommended to prevent vibriosis. Some antibiotics have also been orally administered to reduce mortality of shrimps affected by vibriosis. However, farmers have been properly cautioned regarding their use as emergence of antibiotic-resistant bacteria could consequently arise. Because no practical treatment for fusariosis is currently available, farmers either dispose or harvest infected shrimps followed by disinfection of ponds with 10 ppm chlorine.

      Acute hepatopancreatic necrosis disease (AHPND) has not yet been detected in Japan. As kuruma shrimp is also susceptible to the disease, the Government of Japan plans to designate AHPND as Specific Disease. Under Japanese law, enlistment of AHPND as a quarantinable disease will also be instituted to prevent the introduction of this disease into Japanese hatcheries and grow-out facilities. However, in case an AHPND outbreak inadvertently occurs, Prefectural Fisheries Experimental Stations (PES) could immediately conduct preliminary diagnosis using the AP4 polymerase chain reaction (PCR) method. In addition, confirmatory diagnosis using AP4 nested PCR method and sequencing could be conducted at the National Research Institute of Aquaculture (NRIA), a central laboratory for aquatic animal health. NRIA s task is not only to perform confirmatory diagnosis but likewise disseminate diagnostic techniques to the staff of the National Quarantine and PES.
    • Article

      Interactive effects of vitamin C and E supplementation on growth performance, fatty acid composition and reduction of oxidative stress in juvenile Japanese flounder Paralichthys olivaceus fed dietary oxidized fish oil 

      J Gao, S Koshio, M Ishikawa, S Yokoyama & REP Mamauag - Aquaculture, 2014 - Elsevier
      A study was conducted to determine the interactive effects of vitamin C (VC) and E (VE) supplementation on growth, fatty acid composition and oxidative status of Japanese flounder juveniles. Fish (initial average body weight of 1.1 ± 0.1 g) in triplicate were fed five test diets for 60 days. Control diet contained fresh fish oil (FFO, 8.9 meq/kg) with 100 mg α-tocopherol (α-Toc) equivalents/kg of VE and 500 mg ascorbic acid (AsA) equivalents/kg of VC (FFO100E/500C). The other four diets contained oxidized fish oil (OFO, 167.8 meq/kg) with varying levels of VE (mg/kg) and VC (mg/kg) (OFO100E/500C, OFO200E/500C, OFO100E/1000C and OFO200E/1000C). Fish fed FFO100E/500C and OFO100E/500C had no differences in body weight gain (BWG). However, fish fed OFO200E/1000C diet had a significantly lower BWG than FFO100E/500C. Fish fed OFO200E/500C and OFO100E/1000C showed no differences in thiobarbituric acid-reactive substance values compared with FFO100E/500C. Increasing the levels of VC and VE supplementation increased liver AsA and α-Toc contents, respectively. Liver α-Toc content was significantly increased with incremental dietary VC levels, indicating a sparing effect of VC on liver α-Toc content of fish. Increasing the levels of dietary VC and VE supplementations decreased concentrations of 20:5n-3, 22:5n-3 and 22:6n-3 in fish liver. Fish fed OFO100E/500C and OFO200E/1000C diets showed higher oxidative stress condition than those fed FFO100E/500C. In conclusion, dietary VC and VE supplementation could maintain normal growth and health condition of juvenile Japanese flounder fed OFO. However, high doses of both vitamin supplements induced fish lipid peroxidation under oxidative stress condition.
    • Conference paper

      Japan: Mangrove areas and their utilization 

      M Minagawa - In JH Primavera, LMB Garcia, MT Castaños & MB Surtida (Eds.), Mangrove-Friendly Aquaculture : Proceedings of the Workshop on Mangrove-Friendly Aquaculture organized by the SEAFDEC Aquaculture Department, January 11-15, 1999, Iloilo City, Philippines, 2000 - Aquaculture Department, Southeast Asian Fisheries Development Center
      Although Japan has large-scale aquaculture, there is no aquaculture development in mangrove areas because the total area is small (553 ha) and strictly protected. Mangroves are preserved in comparatively good condition. Future development of aquaculture in mangrove areas is considered small-scale. Rather than aquaculture, Japan practices enhancement and management of wild fisheries. Tourism is another industry that would have an important role in mangrove utilization. But basic research on mangrove ecosystems is essential prior to determining policies for utilization of mangrove areas. International cooperative research work is important to encourage mangrove-friendly aquaculture and protect the environment.
    • Article

      Live food production in Japan: recent progress and future aspects 

      A Hagiwara, WG Gallardo, M Assavaaree, T Kotani & AB de Araujo - Aquaculture, 2001 - Elsevier
      Techniques to culture rotifers at high-density (2000 to 20 000 ind./ml) have been developed by utilizing condensed phytoplankton products. Many public hatcheries in Japan have introduced automated systems for culturing and harvesting rotifers. Research has been conducted on the diagnosis of rotifer culture status and chemical treatment for reducing stress on rotifers. Preservation of the resting eggs of rotifers for an extended period or at low temperature (4 °C) for a limited time has become possible. Thus, appropriately sized rotifers can be provided to fish larvae, according to fish species and growth stage. Techniques to identify the genetic status of rotifer strains have yet to be developed. Practices for culturing copepods in Japan have also been summarized.
    • Book | Conference publication

      Mangrove-Friendly Aquaculture : Proceedings of the Workshop on Mangrove-Friendly Aquaculture organized by the SEAFDEC Aquaculture Department, January 11-15, 1999, Iloilo City, Philippines 

      JH Primavera, LMB Garcia, MT Castaños & MB Surtida (Eds.) - 2000 - Aquaculture Department, Southeast Asian Fisheries Development Center
      The proceedings have three review papers on the mangroves of Southeast Asia, silvofisheries, and Indonesia's integrated mangrove forest and aquaculture systems. The rest of the papers, all on mangrove-friendly aquaculture efforts are from the Philippines, Japan, Thailand, Vietnam, Malaysia, Brunei Darussalam, Indonesia, and Cambodia. All the countries represented had varied methodologies, with Cambodia in its initial stages while some countries like Indonesia and Thailand have tested methodologies. The proceedings include a tabulation of the reported mangrove-friendly technology by country -- e.g. silvofisheries in ponds (mangrove and fish/shrimp/mudcrab) and pens (mangrove and mudcrab). The workshop recommendations are classified into three major topics: problems associated with mangroves, problems associated with aquaculture practices, and socioeconomic and cultural issues.
    • Article

      Microsatellite–centromere mapping in the Japanese eel (Anguilla japonica) by half-tetrad analysis using induced triploid families 

      K Nomura, K Morishima, H Tanaka, T Unuma, K Okuzawa, H Ohta & K Arai - Aquaculture, 2006 - Elsevier
      Genetic improvement of the Japanese eel (Anguilla japonica) can be achieved by artificially controlling its life cycle using recent advances in reproductive biology. In this study, we developed 43 microsatellite loci to confirm Mendelian inheritance at 10 of them as well at 16 previously reported in two full-sib families produced by artificial insemination. In order to establish a base for aquaculture genetics of this species in the near future, these microsatellite loci were mapped in relation to the centromere by half-tetrad analysis using four artificially induced triploid families. The second division segregation frequency (y) of the microsatellite loci ranged from 0.008 to 0.968 (mean ± SD = 0.645 ± 0.298). These results suggest the presence of strong chiasma interference in the eel. Significant differences were observed for the map distances of microsatellite loci between the two isolation procedures. Microsatellites isolated using the enrichment procedure were mapped to various sites starting from the centromere to the telomere, whereas those from the conventional size-selected library showed a tendency to be distributed in the telomeric region.
    • Article

      Molecular epidemiology of koi herpesvirus 

      J Kurita, K Yuasa, T Ito, M Sano, RP Hedrick, MY Engelsma, OLM Haenen, A Sunarto, EB Kholidin, HY Chou, MC Tung, L de la Peña, G Lio-Po, C Tu, K Way & T Iida - Fish Pathology, 2009 - Japanese Society of Fish Pathology
      Three regions of koi herpesvirus (KHV) genomic DNA were compared for 34 samples from Japan, six from Indonesia, two from Taiwan, one from the Philippines, 13 from the Netherlands, one from the UK, one from the USA and one from Israel. The analyzed genomic regions included known PCR-detection targets (SphI-5, 9/5 and the thymidine kinase gene). The KHVs from Asian countries were very homogeneous, although two variants were noted based on a single nucleotide polymorphism. In contrast, seven variants were found in KHVs from outside of Asia, and although closely related to one another, they were clearly distinct from those from Asian. The results suggest that a clear genetic distinction exists between Asian and European (including each single isolate from the USA and Israel) types of KHV, and that unique types of KHV were independently introduced or emerged in the respective geographic locations.
    • magazineArticle

      Promising strategies against WSSV for kuruma shrimp in Japan 

      T Itami - SEAFDEC Asian Aquaculture, 2002 - Aquaculture Department, Southeast Asian Fisheries Development Center
    • Conference paper

      Status of development and use of alternative dietary ingredients in aquaculture feed formulations in Japan: Recent progress of fish meal replacement study of marine fish 

      S Koshio - In MR Catacutan, RM Coloso & BO Acosta (Eds.), Development and Use of Alternative Dietary Ingredients or Fish Meal Substitutes in Aquaculture Feed Formulation … Ingredients or Fish Meal Substitutes in Aquaculture Feed Formulation, 9-11 December 2014, Nay Pyi Taw, Myanmar, 2015 - Aquaculture Department, Southeast Asian Fisheries Development Center
      Fish meal (FM) reduction in aquafeeds is one of the most important issues in aquaculture in Japan. The progress in research studies on reducing the amount of FM in aquafeeds has been demonstrated in several marine species in recent years. This report summarizes those on three species which are high-valued and intensively cultured in Japan; namely, the red sea bream, the amber jack and the Kuruma shrimp.
    • magazineArticle

      Surimi: Status and prospects 

      Southeast Asian Fisheries Development Center, Aquaculture Department - Aqua Farm News, 1995 - Aquaculture Department, Southeast Asian Fisheries Development Center
      The paper discusses the current situation of surimi industry. It is a minced fish meat that is used as a raw material for a wide array of convenient food. Japan remains the world’s leader in consumption and production of surimi. The total supply for 1992 is expected to be 120000-130000 tons of pollock and 30000 tons of others such as Alaska mackerel and fall salmon. USA is the major on-board supplier for Japan while, USSR is another source of pollock surimi. There is a decrease production of hoki surimi from New Zealand due to declining resources and a growing demand for fillets.
    • Article

      Surveillance of emerging fish viral pathogens in some Southeast Asian countries 

      G Lio-Po, E Amar, L de la Peña, ZG Orozco, J Faisan, V Suarnaba & DB Tubo - The Israeli Journal of Aquaculture-Bamidgeh, 2009 - Society of Israeli Aquaculture and Marine Biotechnology
      Preventing the transboundary movement of fish viral pathogens in a global environment requires active surveillance. This study examined the presence of three emerging viral pathogens among koi, common, grass, and silver carp in Cambodia, Lao PDR, Myanmar, Philippines, and Vietnam. The studied viruses included koi herpesvirus (KHV), spring viremia of carp virus (SVCV), and grass carp reovirus (GCRV). Detection methods consisted of virus isolation by cell culture, infection assay in naive fish, polymerase chain reaction (PCR), and reverse-transcriptase PCR (RT-PCR). Tissues were collected and pooled from 193 fish samples in Dec. 2004 to Feb. 2005, 406 in Sep. 2005 to Feb. 2006, and 1302 in Oct. 2006 to Feb. 2007. For cell culture, tissue filtrates were prepared from pooled spleens, kidneys, livers, and gills and inoculated onto koi fin (KF-1), grass carp kidney (GCK), and fat head minnow (FHM) cells. For infection assay, tissue filtrates were injected intraperitoneally to healthy, naive common carp. No virus was detected after three cell culture passages and the infection bioassays. One-step and nested-step PCR was used to detect KHV in gills of fish samples. One-step and semi-nested RT-PCR was used to detect SVCV and GCRV in the spleens, kidneys, and livers of fish samples. Samples from all three years from all five countries yielded negative results for all three viruses, indicating that KHV, SVCV, and GCRV were not present in these five countries during the period of the study although KHV outbreaks had been detected in Indonesia, Taiwan, Japan, Thailand, China, and Malaysia.
    • Article

      Total volume of 3D small patch reefs reflected in aerial photographs can predict total species richness of coral reef damselfish assemblages on a shallow back reef 

      A Hattori & T Shibuno - Ecological Research, 2015 - Springer Verlag
      Because fish have a high dispersal ability, an understanding coral reef fish metacommunity structure is vital for effective conservation. Coral reefs provide patchy habitat of various sizes and scales. We examined the species–area relationship (SAR) of damselfish (Pomacentridae) assemblages over 81 environmentally homogenous patch reefs ranging 0.07–45.4 m2 with low coral cover. Patch reefs were located in the shallow back reef (<2.5 m deep) off Ishigaki Island, Japan. Reef area was measured by performing image analysis of enlarged sections of a high-resolution (>1/2500) color aerial photograph used as a fine-scale seascape map. To assess the effects of three-dimensional meso-scale rugosity on species richness, we assumed that all reefs had a cylindrical shape and examined species by volume (area × height) relationships (SVR). Patch reef volume was a better determinant of species richness than area, and the regression functions of SVR provided better estimates of patch reef species richness. Neither the observed SVRs nor SARs, however, could be explained by a random placement model alone. Our results suggest that several small reefs are likely to have higher species richness than a single large reef of equivalent area in the shallow back reef where large patch reefs are flat. Thus, total patch reef volume (area × height) better reflects meso-scale rugosity and is a useful indicator of total species richness relative to the total amount of essential habitat in shallow back reefs.
    • Article

      An ultrastructural study on the occurrence of aberrant spermatids in the testis of the river sculpin, Cottus hangiongensis 

      GF Quinitio & H Takahashi - Japanese Journal of Ichthyology, 1992 - The Ichthyological Society of Japan
      The process of spermatogenesis and spermiogenesis in the river sculpin,Cottus hangiongensis, was observed ultrastructurally. During spermatogenesis, some germinal cysts in the seminal lobules were found to contain spermatocytes, which were provided with irregularly shaped nuclei, doughnut-shaped mitochondria, and atypical intercellular bridges with multiple disk-like cisternae. In addition, many cysts containing binuclear spermatids were observed in the testis. Within the condensed chromatin of the paired nuclei of the aberrant spermatids, highly electron-dense granules occurred, becoming the core of successively developing chromatin globules. The chromatin globules increased in size, resulting in an enlargement of the paired nuclei. These cells were finally released from the cyst into the lumen of the seminal lobules and underwent further degeneration, thus appearing as characteristic ‘spermatid masses’ in the mature testes.