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Reproduction in Eucheuma denticulatum (Burman) Collins and Hervey and Kappaphycus alvarezii (Doty) Doty farmed in Danajon Reef, Philippines
Aquaculture,
(1992)29-34
29
Elsevier Science Publishers B.V., Amsterdam
eproduction in Eucheuma denticulatum (Burman ) Collins an alvarezii (Doty ) Doty fa Philippines Rhodora Azanza-Corrales, Samuel S. Mamauag, E. Alfiler and M.J. Orolfo Marine Science Institute, University of the Philippines, Diliman, Quezon City, Philippines
(Accepted 6 July I99 1)
ABSTRACT Azanza-Corrales, R., Mamauag, S.S., Alfiler, E. and Orolfo, M.J., 1992. Reproduction in Eucheuma denriculatum (Burman) Collins and Hervey and Kappaphycus alvarezii (Doty ) Doty farmed in Danajon Reef, Philippines. Aquaculture, 103: 29-34. Occurrence of reproductive structures in seven forms belonging to two species of carrageenophytes, Eucheuma denticulatum and Kappaphycus alvarezii was determined at a farming site at Danajon Reef, NorthernBohol, Philippines during 1987 and 1988. Reproductive plants of these forms were encoun-
tered throughout the study period although not all three structures (asexual or tetrasporic form and sexual male and female forms) were represented in each form. For K. alvarezii forms, taking the ‘browns’ (EAB I and EAB2) and the ‘greens’ (EAG 1 and EAGZ) collectively, male and female reproductive structures were found throughout the year but no tetrasporic thalli were encountered. Only male and tetrasporic structures were observed for E. denticulurum (EDB and EDG ) while the ‘sacul type’ ( EAG3) had both structures present throughout the study period. Analysis of variance revealed significant difference (PcO.05) in the frequencies of reproductive structures of each form.
INTRODUCTION
Forms of Eucheuma denticulatum (Burman ) Collins and Hervey and Kappaphycus alvarezii (Doty ) Doty are the most important seaweeds cultivated by vegetative regeneration in Danajon Reef, Northern Bohol, Philippines (Fig. 1). Farming these carrageenophytes is also the main source of living for thousands of coastal dwelling families in Tawi-tawi, Palawan and Cuyo Islands (Trono, 1987). A number of forms of both Kappaphycus alvarezii and Eucheuma denticulatum have appeared since their introduction in the study area. Locally, there has been a number of publications on the genus’ taxonomy, distribution and culture ecology but no report has been made on their reproductive biology. 004M486/92/$05.00 0 1992 Elsevier Science Publishers B.V. All rights reserved.
R. AZANZA-CORRALESET AL.
30
Doty ( 1987) described the development of a tetrasporophyte from carpospores for Kappaphycusalvareziiand designated E. alvarezii as Kappaphycus alvarezii (Doty, 1988), describing the reproductive structures. Other studies on reproductive biology and ecology of species of Eucheuma include Dawes et al. ( 1974), Cheney and Dawes ( 198 1) and Gabrielson ( 1983 ). The effects of environmental factors on algal reproduction have been reviewed by Ohno ( 197 1 ), Dawes et al. ( 1974), Mairh et al. ( 1986) and Hoffmann ( 1987 ), among others. MATERIALS AND METHODS
Antonio-Agro Seaweed Farm, Danajon Reef, Northern Bohol, Philippines ( 10” 16’N Lat., 124’35’E Long.) is a shallow, white sandy stretch of reef flat characterized by consistently strong water current (Fig. 1). Forms of Eucheuma and Kappaphycuswere introduced some 12 years ago and are farmed using the monoline method (Trono, 1987 ). Monthly collections were made over one year (April 1987 to April 1988) on four Kappaphycusalvareziiforms, two Eucheuma denticulatum forms and
20'
II’
0
IO’
m 0 I
0 r
05’
I
BOHOL
IO'
124.20’
1
IO km.
25’
30’
35’
Fig. 1. Location of study site at Danajon Reef, Bohol, Philippines.
45’
124.50’
REPRODUCTlON IN EUCifEUMA AND KAPPAPHYCUS
31
ace unique K alvarezii form called ‘sacul type’ by fishermen. Sampling was done by free-diving and randomly gathering 100 plants for each form each month (Dawes et al., 1974). The seven forms whose morphology is described in detail in Azanza-Corrales ( 1990) are as follows: ( 1) K alvarezif green I= EAG 1; ( 2 ) K+alvarezii green 2 = EAG2; ( 3 ) K. alvarezii brown 1 = EAB 1; (4) K. alvarezii brown 2 = EAB2; ( 5 ) K. alvarezii green 3 = EAG3; (‘sacul type’); (6) E. denticulatum brown=EDB; and (7) E. denticulatum green=EDG. Samples of EAGl and EAG2, and those of EABl and EAB2 were each taken collectively since their reproductive structures have been found to be very similar in size and morphology. Representative fronds were fixed in 5% formalin-seawater solution or Bouin’s fixative and/or buffered glutaraldehyde for microscopic studies. Cross and longitudinal sections using free-hand, and J/B4 and Spurr-embedded plants were studied using a Polyvar Reichert Jung Microscope (Azanza-Corrales, 1990). Occurrence of reproductive ( spermatia, cystocarpic, tetrasporic) and sterile plants was calculated from the total number of samples per form. Analysis of variance, using arcsine transformation of the Statistical Analysis System, was employed to determine the significance of diflerences in frequencies of reproductive structures in each form. RESULTS AND DISCUSSION
Reproductive plants of the various forms (Table 1) were encountered throughout the study period although not all three phases (tetrasporic, antheridial, cystocarpic) were found in each form. Male and female thalli were always found in K alvarezii forms EAB 1, EA EAG 1 and EAG2 (Table 1). Tetrasporophytes were not found in this group. Only male and tetrasporic plants were found in the EAG3 form. No female reproductive structures were found in E. denticulatum forms EDB and EDG. The differences in frequency of occurrence for the three reproductive phases in each form (brown EAB 1 & EAB2 and green EAG 1 & EAG2, each taken collectively) were highly significant (PC 0.05; Table 2 ) . Results indicate that prevailing conditions in the study area could support sporogenesis and gametogenesis (i.e. asexual and sexual, respectively) in Eucheuma and Kappaphyezcs.This was observed also in Manila Bay 1979- 1980 for Gracilaria sp. (Trono and Azanza-Corrales, 198 1) and Calatagan, Batangas for Laurencia sp. (Ganzon-Fortes and Trono, 1982 ) where all reproductive phases were found for both genera throughout the year. Mshigeni ( 1976) suggested that rhythm (associated with spore or gamete production and liberation in some seaweeds) does not commonly occur in the tropics where conditions favor year-round gametogenesis and sporogenesis. In contrast, Hoffmann ( 1987) reported that the fertility of some tropical species was pe-
32
R. AZANZA-CORRALES
ET AL.
TABLE 1 Occurrence (9’0)of reproductive and vegetative thalli in all forms of Eucheuma denticulatum and Kuppuphycus alvarezii, over I year beginning in April 1987 Form Structure
Month Apr.
EABI & EAB2 Antheridial 46 39 Cystocarpic 0 Tetrasporic 15 Vegetative EAG 1 & EAG2 Antheridial 42 35 Cystocarpic Tetrasporic 0 23 Vegetative EAG3 Antheridial 14 0 Cystocarpic 35 Tetrasporic 51 Vegetative EDB Antheridial 3 Cystocarpic 0 Tetrasporic 20 77 Vegetative EDG Antheridial I Cystocarpic 0 Tetrasporic 0 Vegetative 99
June
July
Sep.
Oct.
Nov.
Dec.
Jan.
Feb.
Apr.
44 37 0 19
41
36
21 0 38
17 0 47
53 24 0 23
67 30 0 8
12 72 0 16
6 53 0 31
14 52 0 34
63 8 0 29
59 25 0 15
39 45 0 16
57 25 0 18
53 22 0 25
51 30 0 19
45 40 0 15
23 58 2 17
10 68 0 22
19 58 0 28
53 12 0 35
54 16 7 23
32 0 31 37
34 0 32 34
22 0 34 44
29 0 17 54
38 0 3 59
55 0 16 29
49 0 21 30
34 0 30 36
62 0 14 24
35 0 49 16
1 0 I5 84
44 0 6 50
61 0 1 38
72 0 27
78 0 2 20
72 0 6 22
56 0 9 35
49 0 22 29
60 0 13 27
51 0 18 31
0 0 0
25 0 0 75
57 0 0 48
41 0 0 59
25 0 0 75
60 0 8 32
46 0 6 48
32 0 0 68
52 0 0 48
56 0 11 33
May
100
I
TABLE 2 Summary of ANOVA (Statistical Analysis System ) using arcsine transformation showing differences of frequencies among reproductive structures in seven forms of Eucheuma denticulatum and Kappaphycus alvarezii
Form
d.f. F value
Pr>F
EABl & EAB2 EAGI & EAG2 EAG3 EDB EDG
2
0.1950 0.000 1 0.0683 0.0003 0.000 1
1.73
3
92.39
2 2 2
2.94 11.01 29.86
REPRODUCTION
IN EUCHEUMA
AND KAPPAPHYCUS
33
riodic, as in Gelidiella acerosa (P.S. Rao, 1971; M.U. Rao, 1974) in India and Pterocladia caerulescens (Santelices, 1978) in Hawaii. Vegetative regeneration of plants will continue the same reproductive phases. Thus, the ratio of reproductive phase (i.e. male, female and tetrasporic) may reflect that of the original plants introduced in the area. Sporogenesis and gametogenesis might occur without release or germination. Spores might be released but due to strong water currents in the area, may have settled and developed in other areas. Lack of suitable substrates in the site w-ould lessen the possibility of spore settlement and germination. Hoffmann ( 1987 ) suggested that ‘algal spore rains’ and propagules, sporelings or germlings could be dispersed and dredged in other suitable areas. Factors favoring spore shedding include salinity changes as observed by Kim ( 1970). Hoffmann ( 1987) explained that in some species spore release occurs as a result of desiccation and reimmersion during the sequences of low/high tides while in others, maximum output occurs during high tides. For the farmed carrageenophytes, the mechanism and factors favoring spore release are not yet clear. In the present study, insufficient data on physicochemical factors preclude any conclusive statement. It is suggested that more studies be done on the reproductive biology of Eucheuma specially in areas where they grow naturally. The presence of reproductive plants is very promising, because they can be used in sporulation or ‘seeding’ experiments in the laboratory and field. They could also be sources of materials for other manipulative studies. ACKNOWLEDGEMENTS
We gratefully acknowledge the partial support provided by the Council for Aquatic and Marine Research and Development (PCAMRD) ( 1987- 1988 and 1989- 1990) and the International Foundation for Science (IFS) ( 1989- 1990). The help extended bq;the proprietor and farmers of the Antonio Agro Seaweed Farm, Dr. Ernie1 Barrios of U.P. Statistical Center and Dr. Clinton J. Dawes, for his critical review, is highly appreciated.
REFERENCES
Azanza-Corrales, R., 1990. The farmed Eucheuma species in Danajon Reef, Philippines: vegetative and reproductive structures. J. Appl. Phycol., 2( 1): 57-62. Cheney, D.P. and Dawes, C.J., 198 1. Taxonomic studies of the Florida species of Eucheuma. I. Initial considerations. In: T. Levring (Editor), Proceedings Xth International Seaweed Symposium. Walter de Gruyter, Berlin, pp. 59-66. Dawes, C.J., Mathieson, A.C. and Cheney, D.P., 1974. Ecological studies of Floridian Eucheuma (Rhodophyta, Gigartinales). I. Seasonal growth and reproduction. Bull. Mar. Sci., 24( 2): 235-273.
34
R. AZANZA-CORRALES ET AL.
Doty, MS., 1987. The production and use of Eucheuma. In: M.S. Doty, J.F. Caddy and B. Santilices (Editors), Case Studies of Seven Commercial Seaweed Resources. FAO Fish. Tech. Pap. 28 1. FAO, Rome, pp. 123-I 6 1. Doty, M.S., 1988. Prodomus ad Systematica Eucheumatoideorum: a tribe of commercial seaweeds related to Eucheuma (Solieriaceae, Gigartinales). In: I.A. Abbott (Editor), Taxonomy of Economic Seaweeds with Reference to Some Pacific and Caribbean Species, Vol. II. Calif. Sea Grant College Program, Univ. of Calif., La Jolla, CA. Report NO. T-CSGCP-018, pp. 159-207. Gabrielson, P.W., 1983. Vegetative and reproductive morphology of Eucheuma isiforme (Solieriaceae, Gigartinales, Rhodophyta). J. Phycol., 19: 45-52. Ganzon-Fortes, E.T. and Trono, G.C., Jr., 1982. Reproductive morphology and periodicity of Laurencia sp. at Calatagan, Batangas, Philippines. Kalikasan, Philipp. J. Biol., 1 1 ( 1): 2738. Hoffmann, A.J., 1987. The arrival of seaweed propagules at the shore: a review. Bot. Mar., 30: 151-165. Kim, D.H., 1970. Economically important seaweeds in Chile: Gracilaria.Bot. Mar., 13: 140164. Mairh, O.P., Soe-Htun, U. and Ohno, M., 1986. Culture of Eucheuma sfriatum (Rhodophyta, Solieriaceae) in sub-tropical waters of Shikoku, Japan. Bot. Mar., 29: 18% 19 1. Mshigeni, K.E., 1976. Field ctiltivation of Hypnea (Rhodophyta) spores for carrageenan: prospects and problems. Bot. Mar., 30: 38 l-383. Ohno, M., 1972. The periodicity ofgamete liberation in Mcmostruma.In: K. Nisizawa, S. Araki, M. Chihara, Y. Nakamura and Y. Tsuchiya (Editors), Proc. VIIth Int. Seaweed Symp., 812 August 197 1 at Sapporo, Japan. Univ. Tokyo Press, pp. 405-409. Rao, M.U., 1974. Observations on fruiting cycle, spore output and germination of tetraspores of Gelidiellaacerosu in the Gulf of Mannar. Bot. Mar., 17: 204-207. Rao, P.S., 197 1. Studies on Gelidiellaacerosa (Forsk. ) Feldmann et Hamel. IV: spore studies. Bull. Jpn. Sot. Phycol., 19: 9-14. Santelices, B., 1978. The morphological variation of Pterucludiucaerzdescens(Gelidiales, Rhodophyta) in Hawaii. Phycologia, 17: 53-59. Trono, G.C., Jr., 1987. Seaweed Culture in Asia-Pacific Region. Regional Office for Asia and the Pacific (RAPA), Food and Agriculture Organization of the United Nations, Bangkok, Thailand, 4 1 pp. Trono, G.C., Jr. and Azanza-Corrales, R., 198 1. The seasonal variation in the biomass and reproductive states of Gracilariain Manila Bay. In: T. Levring (Editor), Proceedings Xth International Seaweed Symposium. Walter de Gruyter, Berlin, pp. 743-748.
(1992)29-34
29
Elsevier Science Publishers B.V., Amsterdam
eproduction in Eucheuma denticulatum (Burman ) Collins an alvarezii (Doty ) Doty fa Philippines Rhodora Azanza-Corrales, Samuel S. Mamauag, E. Alfiler and M.J. Orolfo Marine Science Institute, University of the Philippines, Diliman, Quezon City, Philippines
(Accepted 6 July I99 1)
ABSTRACT Azanza-Corrales, R., Mamauag, S.S., Alfiler, E. and Orolfo, M.J., 1992. Reproduction in Eucheuma denriculatum (Burman) Collins and Hervey and Kappaphycus alvarezii (Doty ) Doty farmed in Danajon Reef, Philippines. Aquaculture, 103: 29-34. Occurrence of reproductive structures in seven forms belonging to two species of carrageenophytes, Eucheuma denticulatum and Kappaphycus alvarezii was determined at a farming site at Danajon Reef, NorthernBohol, Philippines during 1987 and 1988. Reproductive plants of these forms were encoun-
tered throughout the study period although not all three structures (asexual or tetrasporic form and sexual male and female forms) were represented in each form. For K. alvarezii forms, taking the ‘browns’ (EAB I and EAB2) and the ‘greens’ (EAG 1 and EAGZ) collectively, male and female reproductive structures were found throughout the year but no tetrasporic thalli were encountered. Only male and tetrasporic structures were observed for E. denticulurum (EDB and EDG ) while the ‘sacul type’ ( EAG3) had both structures present throughout the study period. Analysis of variance revealed significant difference (PcO.05) in the frequencies of reproductive structures of each form.
INTRODUCTION
Forms of Eucheuma denticulatum (Burman ) Collins and Hervey and Kappaphycus alvarezii (Doty ) Doty are the most important seaweeds cultivated by vegetative regeneration in Danajon Reef, Northern Bohol, Philippines (Fig. 1). Farming these carrageenophytes is also the main source of living for thousands of coastal dwelling families in Tawi-tawi, Palawan and Cuyo Islands (Trono, 1987). A number of forms of both Kappaphycus alvarezii and Eucheuma denticulatum have appeared since their introduction in the study area. Locally, there has been a number of publications on the genus’ taxonomy, distribution and culture ecology but no report has been made on their reproductive biology. 004M486/92/$05.00 0 1992 Elsevier Science Publishers B.V. All rights reserved.
R. AZANZA-CORRALESET AL.
30
Doty ( 1987) described the development of a tetrasporophyte from carpospores for Kappaphycusalvareziiand designated E. alvarezii as Kappaphycus alvarezii (Doty, 1988), describing the reproductive structures. Other studies on reproductive biology and ecology of species of Eucheuma include Dawes et al. ( 1974), Cheney and Dawes ( 198 1) and Gabrielson ( 1983 ). The effects of environmental factors on algal reproduction have been reviewed by Ohno ( 197 1 ), Dawes et al. ( 1974), Mairh et al. ( 1986) and Hoffmann ( 1987 ), among others. MATERIALS AND METHODS
Antonio-Agro Seaweed Farm, Danajon Reef, Northern Bohol, Philippines ( 10” 16’N Lat., 124’35’E Long.) is a shallow, white sandy stretch of reef flat characterized by consistently strong water current (Fig. 1). Forms of Eucheuma and Kappaphycuswere introduced some 12 years ago and are farmed using the monoline method (Trono, 1987 ). Monthly collections were made over one year (April 1987 to April 1988) on four Kappaphycusalvareziiforms, two Eucheuma denticulatum forms and
20'
II’
0
IO’
m 0 I
0 r
05’
I
BOHOL
IO'
124.20’
1
IO km.
25’
30’
35’
Fig. 1. Location of study site at Danajon Reef, Bohol, Philippines.
45’
124.50’
REPRODUCTlON IN EUCifEUMA AND KAPPAPHYCUS
31
ace unique K alvarezii form called ‘sacul type’ by fishermen. Sampling was done by free-diving and randomly gathering 100 plants for each form each month (Dawes et al., 1974). The seven forms whose morphology is described in detail in Azanza-Corrales ( 1990) are as follows: ( 1) K alvarezif green I= EAG 1; ( 2 ) K+alvarezii green 2 = EAG2; ( 3 ) K. alvarezii brown 1 = EAB 1; (4) K. alvarezii brown 2 = EAB2; ( 5 ) K. alvarezii green 3 = EAG3; (‘sacul type’); (6) E. denticulatum brown=EDB; and (7) E. denticulatum green=EDG. Samples of EAGl and EAG2, and those of EABl and EAB2 were each taken collectively since their reproductive structures have been found to be very similar in size and morphology. Representative fronds were fixed in 5% formalin-seawater solution or Bouin’s fixative and/or buffered glutaraldehyde for microscopic studies. Cross and longitudinal sections using free-hand, and J/B4 and Spurr-embedded plants were studied using a Polyvar Reichert Jung Microscope (Azanza-Corrales, 1990). Occurrence of reproductive ( spermatia, cystocarpic, tetrasporic) and sterile plants was calculated from the total number of samples per form. Analysis of variance, using arcsine transformation of the Statistical Analysis System, was employed to determine the significance of diflerences in frequencies of reproductive structures in each form. RESULTS AND DISCUSSION
Reproductive plants of the various forms (Table 1) were encountered throughout the study period although not all three phases (tetrasporic, antheridial, cystocarpic) were found in each form. Male and female thalli were always found in K alvarezii forms EAB 1, EA EAG 1 and EAG2 (Table 1). Tetrasporophytes were not found in this group. Only male and tetrasporic plants were found in the EAG3 form. No female reproductive structures were found in E. denticulatum forms EDB and EDG. The differences in frequency of occurrence for the three reproductive phases in each form (brown EAB 1 & EAB2 and green EAG 1 & EAG2, each taken collectively) were highly significant (PC 0.05; Table 2 ) . Results indicate that prevailing conditions in the study area could support sporogenesis and gametogenesis (i.e. asexual and sexual, respectively) in Eucheuma and Kappaphyezcs.This was observed also in Manila Bay 1979- 1980 for Gracilaria sp. (Trono and Azanza-Corrales, 198 1) and Calatagan, Batangas for Laurencia sp. (Ganzon-Fortes and Trono, 1982 ) where all reproductive phases were found for both genera throughout the year. Mshigeni ( 1976) suggested that rhythm (associated with spore or gamete production and liberation in some seaweeds) does not commonly occur in the tropics where conditions favor year-round gametogenesis and sporogenesis. In contrast, Hoffmann ( 1987) reported that the fertility of some tropical species was pe-
32
R. AZANZA-CORRALES
ET AL.
TABLE 1 Occurrence (9’0)of reproductive and vegetative thalli in all forms of Eucheuma denticulatum and Kuppuphycus alvarezii, over I year beginning in April 1987 Form Structure
Month Apr.
EABI & EAB2 Antheridial 46 39 Cystocarpic 0 Tetrasporic 15 Vegetative EAG 1 & EAG2 Antheridial 42 35 Cystocarpic Tetrasporic 0 23 Vegetative EAG3 Antheridial 14 0 Cystocarpic 35 Tetrasporic 51 Vegetative EDB Antheridial 3 Cystocarpic 0 Tetrasporic 20 77 Vegetative EDG Antheridial I Cystocarpic 0 Tetrasporic 0 Vegetative 99
June
July
Sep.
Oct.
Nov.
Dec.
Jan.
Feb.
Apr.
44 37 0 19
41
36
21 0 38
17 0 47
53 24 0 23
67 30 0 8
12 72 0 16
6 53 0 31
14 52 0 34
63 8 0 29
59 25 0 15
39 45 0 16
57 25 0 18
53 22 0 25
51 30 0 19
45 40 0 15
23 58 2 17
10 68 0 22
19 58 0 28
53 12 0 35
54 16 7 23
32 0 31 37
34 0 32 34
22 0 34 44
29 0 17 54
38 0 3 59
55 0 16 29
49 0 21 30
34 0 30 36
62 0 14 24
35 0 49 16
1 0 I5 84
44 0 6 50
61 0 1 38
72 0 27
78 0 2 20
72 0 6 22
56 0 9 35
49 0 22 29
60 0 13 27
51 0 18 31
0 0 0
25 0 0 75
57 0 0 48
41 0 0 59
25 0 0 75
60 0 8 32
46 0 6 48
32 0 0 68
52 0 0 48
56 0 11 33
May
100
I
TABLE 2 Summary of ANOVA (Statistical Analysis System ) using arcsine transformation showing differences of frequencies among reproductive structures in seven forms of Eucheuma denticulatum and Kappaphycus alvarezii
Form
d.f. F value
Pr>F
EABl & EAB2 EAGI & EAG2 EAG3 EDB EDG
2
0.1950 0.000 1 0.0683 0.0003 0.000 1
1.73
3
92.39
2 2 2
2.94 11.01 29.86
REPRODUCTION
IN EUCHEUMA
AND KAPPAPHYCUS
33
riodic, as in Gelidiella acerosa (P.S. Rao, 1971; M.U. Rao, 1974) in India and Pterocladia caerulescens (Santelices, 1978) in Hawaii. Vegetative regeneration of plants will continue the same reproductive phases. Thus, the ratio of reproductive phase (i.e. male, female and tetrasporic) may reflect that of the original plants introduced in the area. Sporogenesis and gametogenesis might occur without release or germination. Spores might be released but due to strong water currents in the area, may have settled and developed in other areas. Lack of suitable substrates in the site w-ould lessen the possibility of spore settlement and germination. Hoffmann ( 1987 ) suggested that ‘algal spore rains’ and propagules, sporelings or germlings could be dispersed and dredged in other suitable areas. Factors favoring spore shedding include salinity changes as observed by Kim ( 1970). Hoffmann ( 1987) explained that in some species spore release occurs as a result of desiccation and reimmersion during the sequences of low/high tides while in others, maximum output occurs during high tides. For the farmed carrageenophytes, the mechanism and factors favoring spore release are not yet clear. In the present study, insufficient data on physicochemical factors preclude any conclusive statement. It is suggested that more studies be done on the reproductive biology of Eucheuma specially in areas where they grow naturally. The presence of reproductive plants is very promising, because they can be used in sporulation or ‘seeding’ experiments in the laboratory and field. They could also be sources of materials for other manipulative studies. ACKNOWLEDGEMENTS
We gratefully acknowledge the partial support provided by the Council for Aquatic and Marine Research and Development (PCAMRD) ( 1987- 1988 and 1989- 1990) and the International Foundation for Science (IFS) ( 1989- 1990). The help extended bq;the proprietor and farmers of the Antonio Agro Seaweed Farm, Dr. Ernie1 Barrios of U.P. Statistical Center and Dr. Clinton J. Dawes, for his critical review, is highly appreciated.
REFERENCES
Azanza-Corrales, R., 1990. The farmed Eucheuma species in Danajon Reef, Philippines: vegetative and reproductive structures. J. Appl. Phycol., 2( 1): 57-62. Cheney, D.P. and Dawes, C.J., 198 1. Taxonomic studies of the Florida species of Eucheuma. I. Initial considerations. In: T. Levring (Editor), Proceedings Xth International Seaweed Symposium. Walter de Gruyter, Berlin, pp. 59-66. Dawes, C.J., Mathieson, A.C. and Cheney, D.P., 1974. Ecological studies of Floridian Eucheuma (Rhodophyta, Gigartinales). I. Seasonal growth and reproduction. Bull. Mar. Sci., 24( 2): 235-273.
34
R. AZANZA-CORRALES ET AL.
Doty, MS., 1987. The production and use of Eucheuma. In: M.S. Doty, J.F. Caddy and B. Santilices (Editors), Case Studies of Seven Commercial Seaweed Resources. FAO Fish. Tech. Pap. 28 1. FAO, Rome, pp. 123-I 6 1. Doty, M.S., 1988. Prodomus ad Systematica Eucheumatoideorum: a tribe of commercial seaweeds related to Eucheuma (Solieriaceae, Gigartinales). In: I.A. Abbott (Editor), Taxonomy of Economic Seaweeds with Reference to Some Pacific and Caribbean Species, Vol. II. Calif. Sea Grant College Program, Univ. of Calif., La Jolla, CA. Report NO. T-CSGCP-018, pp. 159-207. Gabrielson, P.W., 1983. Vegetative and reproductive morphology of Eucheuma isiforme (Solieriaceae, Gigartinales, Rhodophyta). J. Phycol., 19: 45-52. Ganzon-Fortes, E.T. and Trono, G.C., Jr., 1982. Reproductive morphology and periodicity of Laurencia sp. at Calatagan, Batangas, Philippines. Kalikasan, Philipp. J. Biol., 1 1 ( 1): 2738. Hoffmann, A.J., 1987. The arrival of seaweed propagules at the shore: a review. Bot. Mar., 30: 151-165. Kim, D.H., 1970. Economically important seaweeds in Chile: Gracilaria.Bot. Mar., 13: 140164. Mairh, O.P., Soe-Htun, U. and Ohno, M., 1986. Culture of Eucheuma sfriatum (Rhodophyta, Solieriaceae) in sub-tropical waters of Shikoku, Japan. Bot. Mar., 29: 18% 19 1. Mshigeni, K.E., 1976. Field ctiltivation of Hypnea (Rhodophyta) spores for carrageenan: prospects and problems. Bot. Mar., 30: 38 l-383. Ohno, M., 1972. The periodicity ofgamete liberation in Mcmostruma.In: K. Nisizawa, S. Araki, M. Chihara, Y. Nakamura and Y. Tsuchiya (Editors), Proc. VIIth Int. Seaweed Symp., 812 August 197 1 at Sapporo, Japan. Univ. Tokyo Press, pp. 405-409. Rao, M.U., 1974. Observations on fruiting cycle, spore output and germination of tetraspores of Gelidiellaacerosu in the Gulf of Mannar. Bot. Mar., 17: 204-207. Rao, P.S., 197 1. Studies on Gelidiellaacerosa (Forsk. ) Feldmann et Hamel. IV: spore studies. Bull. Jpn. Sot. Phycol., 19: 9-14. Santelices, B., 1978. The morphological variation of Pterucludiucaerzdescens(Gelidiales, Rhodophyta) in Hawaii. Phycologia, 17: 53-59. Trono, G.C., Jr., 1987. Seaweed Culture in Asia-Pacific Region. Regional Office for Asia and the Pacific (RAPA), Food and Agriculture Organization of the United Nations, Bangkok, Thailand, 4 1 pp. Trono, G.C., Jr. and Azanza-Corrales, R., 198 1. The seasonal variation in the biomass and reproductive states of Gracilariain Manila Bay. In: T. Levring (Editor), Proceedings Xth International Seaweed Symposium. Walter de Gruyter, Berlin, pp. 743-748.