Papers by Dr. Roberto Pagulayan
Proceedings of the First National Congress on Philippine Lakes, 2005
Environmental Monitoring and Assessment, 2005
In order to achieve a more substantial appraisal of lake water quality, the assessment must not b... more In order to achieve a more substantial appraisal of lake water quality, the assessment must not be based only on chemical measurements and analyses of the water itself, but even more so on the impact of existing conditions on aquatic biota. This is possible with the use of biotests or biomarkers, e.g. investigations of the developmental parameters (96-h embryotoxicity evaluate) or of the induction of heat shock proteins (proteotoxicity evaluate). To evaluate the suitability of these tests for environmental screening, fertilized zebrafish eggs were exposed to water samples collected from five sites of varying levels of stress from Laguna Lake, Philippines. Reconstituted water was used as laboratory control while water samples from a highly polluted freshwater source was used as positive control. Developmental parameters were noted and described within 48 and 96 h of exposure. Dilution experiments of the positive control were also done to further assess and compare toxicity potentials of Laguna Lake waters with those originating from a polluted freshwater. After the 96-h exposure, the levels of stress proteins (hsp 70) were determined in embryos from all exposure groups. Results showed 100% mortality in embryos exposed to undiluted positive control (PC) within only 12 h. Increasing dilution levels, however, resulted in lower mortality and lower abnormality rates. No detectable developmental differences were noted among embryos exposed to either the laboratory control or Laguna Lake waters at the end of 96 h, regardless of the source. Very high survival rates and high hatching success rates were observed in embryos exposed to lake waters as well as laboratory control, and the data did not differ significantly among the groups. Likewise, no significant malformations were noted among all developing embryos throughout the exposure period. However, the levels of heat shock proteins in the two sites located closest to Manila, the Philippine capital (Northern West Bay and Central West Bay), showed a pronounced elevation relative to the control, indicating that these stress proteins protect the embryos from the detrimental effects of pollutants in the water. Based on the 96-h early life stage (ELS) test, the water quality of the lake is good for fishery propagation despite the current levels of pollutants in the water. This finding is in accordance with the Class C status (i.e. suitable for fish growth and propagation) as given to the lake by the local environmental agency. On the other hand, data on proteotoxicity showed that the fish are under stress, presumably deriving from pollutants. This calls for a continuous monitoring and improvement of the lake water. The present study indicates that the two biomarker methods are very easy to use, practical, rapid, and sensitive for assessing water quality in a tropical lake and recommends for their incorporation into the future monitoring program of Laguna Lake.
Zooplanktivory in the endemic freshwater sardine, Sardinella tawilis (Herre 1927) of Taal Lake, t... more Zooplanktivory in the endemic freshwater sardine, Sardinella tawilis (Herre 1927) of Taal Lake, the Philippines. Zoological Studies 47(5): xxx-xxx. In this study, we compared the composition and relative abundance of zooplankton found in the vicinity of Napayun I., Taal Lake, the Philippines, with the zooplankton found in stomachs of the freshwater sardine Sardinella tawilis (Herre 1927) caught from the same location. Samplings were conducted monthly from July 2003 to June 2004. Ninety percent of the stomach contents were composed of relatively large-bodied adult copepods; the remaining 10 % contained cladocerans and rotifers. Selectivity coefficients computed from comparing the fish diet with the available prey from the environment showed a high preference for copepods and a low to no preference for cladocerans and rotifers for all 10 mo sampled of the 12-mo study. A high preference for calanoid copepods noted in Apr.-June coincided with the peak spawning of S. tawilis according to...
A taxonomic and biogeographic study of the introduced suckermouth armored catfishes locally known... more A taxonomic and biogeographic study of the introduced suckermouth armored catfishes locally known as “janitor fish ” is briefly described. Specimens were collected from five sites in the Laguna de Bay basin and were examined for 19 meristic and 37 morphometric characters and other external features including coloration. Results were compared with existing literature on fishes in the family Loricariidae. Examination revealed that specimens of janitor fish, previously reported as Hypostomus plecostomus, actually belong to the genus Pterygoplichthys, family Loricariidae. Collected specimens consisted of two species—Pterygoplichthys disjunctivus and Pterygoplichthys pardalis. Both species were collected from the five sites except in Pasig River where only P. disjunctivus was collected.
AGRIS record. Record number, PH1997011152. Titles, Update of freshwater mollusc research in the P... more AGRIS record. Record number, PH1997011152. Titles, Update of freshwater mollusc research in the Philippines. Personal Authors, Pagulayan, RC (Philippines Univ. Diliman, Diliman, Quezon City (Philippines)). Conference, 1. National ...
Zoological Studies, 2008
Rey Donne S. Papa, Roberto C. Pagulayan, and Alicia Ely J. Pagulayan (2008) Zooplanktivory in the... more Rey Donne S. Papa, Roberto C. Pagulayan, and Alicia Ely J. Pagulayan (2008) Zooplanktivory in the endemic freshwater sardine, Sardinella tawilis (Herre 1927) of Taal Lake, the Philippines. Zoological Studies 47(5): 535-543. In this study, we compared the composition and relative abundance of zooplankton found in the vicinity of Napayun I., Taal Lake, the Philippines, with the zooplankton found in stomachs of the freshwater sardine Sardinella.tawilis (Herre 1927) caught from the same location. Samplings were conducted monthly from July 2003 to June 2004. Ninety percent of the stomach contents were composed of relatively large-bodied adult copepods; the remaining 10% contained cladocerans and rotifers. Selectivity coefficients computed from comparing the fish diet with the available prey from the environment showed a high preference for copepods and a low to no preference for cladocerans and rotifers for all 10 mo sampled of the 12 mo study. A high preference for calanoid copepods not...
Science Diliman, 2007
The digestive anatomy of Radix sp. from Taal Lake, Batangas, Philippines, was studied. The major ... more The digestive anatomy of Radix sp. from Taal Lake, Batangas, Philippines, was studied. The major differences with the other known lymnaeids previously described from the Philippines are found in the radular formula, presence of intestinal caecum, the orientation of the pylorus and the intestine, and the number of loops made by the intestine around the stomach and the digestive gland.
Philippine Agricultural Scientist, 2009
The silver perch,Leiopotherapon plumbeus (Kner, 1864), is an endemic and economically important f... more The silver perch,Leiopotherapon plumbeus (Kner, 1864), is an endemic and economically important fish in the Philippines. A native species of Laguna de Bay, the silver perch was transplanted from this lake to Sampaloc Lake in the late 1950s and Taal Lake in the early 1970s. Morphological variation has been observed among the native and transplanted populations of the silver perch. In this study, genetic variation within and between the native and transplanted populations was examined using isozyme electrophoresis. Four sites were sampled: two in Laguna de Bay (Binangonan and Tanay) and one each in Sampaloc Lake and Taal Lake. Twenty-two (22) loci were scored but only one locus (PGM*) was polymorphic by the 95% criterion and only two loci (ADH* and PGM*) were polymorphic by the 99% criterion. The average heterozygosities, genetic distances and FST values of specimens from the four sites were very low, suggesting that the native and transplanted populations had very low genetic variati...
We show that the structure of microcrustacean zooplankton communities in five Asian tropical wate... more We show that the structure of microcrustacean zooplankton communities in five Asian tropical water bodies (Sri Lanka: three reservoirs; Thailand: one reservoir, Philippines: one crater lake) differed among these water bodies and that these differences were correlated with environmental variables, but that there was no clear seasonality. The structure of the communities was described by both densities of zooplankton taxa / groups, and by sizes of higher zooplankton taxa (calanoid copepods, cyclopoid copepods, and cladocerans). In addition, zooplankton fecundity was studied on a species basis for the Sri Lankan and Thai reservoirs. Variation between water bodies and temporal variation within water bodies were studied with univariate and multivariate techniques. Zooplankton densities
The environmental impact of cage culture on water quality of Lake Taal was assessed from March 19... more The environmental impact of cage culture on water quality of Lake Taal was assessed from March 1996 through February 1997. Three stations were considered namely: Balas, which serves as station 1 (non-cage area) and Sampaloc and Laurel, stations 2 and 3 (cage areas), respectively. Monthly water samples with two replicates were collected using a van Dorn sampler at 0, 5, 10 and 15-m depths in all stations. Below surface water from the inside of the cages was also collected. Water temperature, water transparency, pH, and conductivity were determined in situ. Dissolved oxygen, chloride, NO 3 , NH 3 , PO 4 , and total P were analyzed in the laboratory. Phytoplankton density and algal biomass (through cholorophyll a) and primary productivity indices were determined with the light-and-dark bottle method. Of the water quality parameters, conductivity and DO had significant differences between non-cage and cage areas. Conductivity gave significant difference (P<0.01) between control and c...
Molluscan Research, 2016
ABSTRACT Intensive aquaculture in natural lakes has been shown to have negative effects on biodiv... more ABSTRACT Intensive aquaculture in natural lakes has been shown to have negative effects on biodiversity. We conducted a study on the diversity and distribution of macro-gastropods (>1 cm) in three major lakes used for aquaculture on Luzon, the largest island in the Philippines archipelago, to provide baseline information on freshwater gastropods. Collections were made in 27 sampling sites in all three lakes. The samples were identified by examining the shell and radula. The gastropod collection comprised 13 species in six families, including 12 new records in Laguna de Bay and seven new records for Lake Taal. All species found in Lake Sampaloc are considered new records due to the lack of published literature on its gastropod fauna. There is low gastropod diversity in all three lakes. Distribution within the lakes is related to the presence of suitable habitats for each species rather than the size and geological origin of the lakes. The proximity of all three lakes may have facilitated gastropod dispersal between them, as all have similar environmental conditions brought about by intensive aquaculture activities.
… of Philippine Lakes in Relation to …, 2001
The environmental impact of cage culture on water quality of Lake Taal was assessed from March 19... more The environmental impact of cage culture on water quality of Lake Taal was assessed from March 1996 through February 1997. Three stations were considered namely: Balas, which serves as station 1 (non-cage area) and Sampaloc and Laurel, stations 2 and 3 (cage areas), respectively. Monthly water samples with two replicates were collected using a van Dorn sampler at 0, 5, 10 and 15-m depths in all stations. Below surface water from the inside of the cages was also collected. Water temperature, water transparency, pH, and conductivity were determined in situ. Dissolved oxygen, chloride, NO 3 , NH 3 , PO 4 , and total P were analyzed in the laboratory. Phytoplankton density and algal biomass (through cholorophyll a) and primary productivity indices were determined with the light-and-dark bottle method.
This study represents the first molecular survey of the ichthyofauna of Taal Lake and the first D... more This study represents the first molecular survey of the ichthyofauna of Taal Lake and the first DNA barcoding attempt in Philippine fishes. Taal Lake, the third largest lake in the Philippines, is considered a very important fisheries resource and is home to the world's ...
Journal of Zoological …, 2009
Philippine sardines are members of the commercially important Sardinella genus (Family Clupeidae)... more Philippine sardines are members of the commercially important Sardinella genus (Family Clupeidae). Sardines are mostly marine species with a very few exception like the Philippine freshwater sardine, Sardinella tawilis, of Lake Taal. This species is believed to have immigrated from Balayan Bay some 250 years ago. To determine the relationship of freshwater S. tawilis to the marine forms, 35 biometric features were investigated. The variables were subjected to univariate (mean, standard deviation and coefficient of variance) and multivariate analyses [Principal Component Analysis (PCA) and Hierarchical Cluster Analysis]. Results from univariate tests revealed that the number of ventral fin ray can discriminate Sardinella lemuru from the rest of the sardines. Multivariate PCA, on the other hand, showed discrete separation of the marine sardines. Sardinella tawilis, however, cannot be clearly separated from the marine species, Sardinella albella. The same clustering was recovered in HCA, thus providing evidence that S. albella is the closest marine relative of the freshwater S. tawilis.
Extensive studies have been carried out on the diversity, morphology, ecology and reproductive bi... more Extensive studies have been carried out on the diversity, morphology, ecology and reproductive biology of Littorinidae. Two species of Littoraria (Littorinidae)have been recorded to be present in Bangkung Mapalad, Sasmuan, Pampanga : Littoraria cf. angulifera and Littoraria cf. articulata . However, quantifiable morphometric data on shell shape variation is not available among these taxa in the area. This study aims to examine and identify snail species that thrive in Bangkung Mapalad using landmark-based geometric morphometric analysis. A freeware program tpsDig v. 2.30 was used for landmark digitization and the analysis of landmark data was done using Paleontological Statistics (PAST) v.2.17. The Principal Component Analysis of the 42 coordinates of the 21 landmarks combine to account for 85.814 % of the variation amongst the samples and showed separation between L. cf angulifera and L. cf articulata . Visualization of shell shape, relative to the mean shape, generated from thin-p...
We show that the structure of microcrustacean zooplankton communities in five Asian tropical wate... more We show that the structure of microcrustacean zooplankton communities in five Asian tropical water bodies (Sri Lanka: three reservoirs; Thailand: one reservoir, Philippines: one crater lake) differed among these water bodies and that these differences were correlated with environmental variables, but that there was no clear seasonality. The structure of the communities was described by both densities of zooplankton taxa / groups, and by sizes of higher zooplankton taxa (calanoid copepods, cyclopoid copepods, and cladocerans). In addition, zooplankton fecundity was studied on a species basis for the Sri Lankan and Thai reservoirs. Variation between water bodies and temporal variation within water bodies were studied with univariate and multivariate techniques. Zooplankton densities 154 were highest in Lake Taal (Philippines) and Ubolratana station 3 (Thailand), but very similar for the three Sri Lankan reservoirs. Mean size per taxon differed slightly among the investigated water bodies, copepods were smaller in Lake Taal and larger in Minneriya and Ubolratana station 3, but fecundities per species were similar. A redundancy analysis on densities of zooplankton groups showed that the zooplankton communities of all five water bodies showed considerable temporal variation, and that they also differed among each other. Temperature and chlorophyll-a concentration were most strongly correlated with community structure, while the effect of water level was negligible. A canonical variates analysis with season as class showed that although we observed some indication of seasonality in community structure, it was not statistically significant.
Philippine Journal of Systematic Biology, 2009
Philippine sardines are members of the commercially important Sardinella genus (Family Clupeidae)... more Philippine sardines are members of the commercially important Sardinella genus (Family Clupeidae). Sardines are mostly marine species with a very few exception like the Philippine freshwater sardine, Sardinella tawilis, of Lake Taal. This species is believed to have immigrated from Balayan Bay some 250 years ago. To determine the relationship of freshwater S. tawilis to the marine forms, 35 biometric features were investigated. The variables were subjected to univariate (mean, standard deviation and coefficient of variance) and multivariate analyses [Principal Component Analysis (PCA) and Hierarchical Cluster Analysis]. Results from univariate tests revealed that the number of ventral fin ray can discriminate Sardinella lemuru from the rest of the sardines. Multivariate PCA, on the other hand, showed discrete separation of the marine sardines. Sardinella tawilis, however, cannot be clearly separated from the marine species, Sardinella albella. The same clustering was recovered in HCA, thus providing evidence that S. albella is the closest marine relative of the freshwater S. tawilis.
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Papers by Dr. Roberto Pagulayan