Sunday, August 27, 2006


Imbaw: An Abstract-Bibliography

Melchor F. Cichon
August 26, 2006


I have observed that lately biology students from the University of the Philippines in the Visayas and some researchers from the same University have become interested in imbaw, a mud clam, Anodontia edentula. This bivalve is common in mangrove areas and is a delicacy in Western Visayas, especially in Panay and Guimaras.

To help them find literature on this subject, I surfed the internet and luckily I found about six. I also checked the theses collection of the UPV, and I found some more. The results (16) of that search are found below.

As of this date, the focus of the research on this species is on its reproduction. We still have to know its behavior, culture, diseases and pests, ecology, feeding habits, handling and processing, physiology, economics, and life history. We also still have to know its enzymes. Aside from food, what other economic values can be produced from this bivalve?

Indeed, there are many more things to know about imbaw.

I challenge our researchers to find that out.

Through this search, I noticed that there are two species of imbaw: the Anodontia edentula and the Austriella corrugata. How are they different from each other, I still have to find that out.

The abstracts were written by the respective authors. I included them here as a public service to all those who are interested in this subject.

But if you have additional research work about this bivalve, please notify me through the Comment Post of this blog.

The theses are available at the CAS Ref/Serial Section of the College of Arts and Sciences Library, University of the Philippines in the Visayas, Miag-ao, Iloilo, Philippines.

1. Arboleda, Erika Anfone. 1999. Effect of sperm concentration on fertilization rate and the timing of early developmental stages of imbaw, (Anodontia edentula). 19 leaves. Undergraduate thesis-B.S. Biology-U.P. in the Visayas, Iloilo. Available at: CAS Ref./Serials. In this study, effect of sperm concentration to fertilization rate is investigated. Also, the timing of early developmental stages is done. Sperm concentration at seventy is most effective although not significantly different. In the range used, effect of sperm concentration to fertilization rate is broad. The concentration of ten sperm per egg is least effective and significantly different from all the rest. In developmental stages, polar body extrusion is observed after ten minutes from fertilization. Two-cell and four-cell is formed within an hour. After two hours, eight-cell and sixteen-cell stage is noted. The larval stage trocophore is already present after the fifteenth hour. The straight-hinge veliger can be observed after twenty four hours.

2. Dideles, Kristi Marie Joie. 2005. A preliminary study of sexual dimorphism and hermaphroditism occuring in the mud clam sp., Austriella corrugata (Deshayes, 1843). 2005. 33 leaves. Undergraduate thesis-B.S. Biology-U.P. in the Visayas, Iloilo. Available at CAS Ref./Serials. 75 leaves. Austriella corrugata, commonly known as imbaw laki, inhabits the muddy bottom of mangrove areas, or the adjacent mudflats. To date, there is only one reported study regarding this clam which is a potential aquaculture species. Further research on the biology and distribution of this clams can greatly contribute to the recognition of this species as an important source of food and income. Thus this study was conducted to gather preliminary investigation on the characterization of imbaw laki. Sexual dimorphism was found to be exhibited by A. corrugata which was determined by its shell morphology and gonad characterization. Maturity rates were last determined through gonadal biopsy and was noted to be constant throughout the sampling months. Monthly maturity rates was also correlated with the GSI values of the clams. Hermaphroditism was also found to be present in the clam population which was also determined through gonadal biopsy and histological examination of gonad sections.-"

3. Guevarra, Ann F. 2005. A preliminary study on fecundity measure of the mudclam Anodontia edentula. 26 leaves. Undergraduate thesis-B.S. Biology-U.P. in the Visayas, Iloilo. Available at CAS Ref./Serials. Fecundity measure of mud clam Anodontia edentula, locally known as "Imbaw" was the main focus on this study. The external characteristics of the clams such as the shell length width and height were measured. Eggs were also counted an its characteristics were also noted. Results show that there is direct relationship between the shell length and the number of eggs the clams produce. Moreover, it was observed that big clams with shell length that range from 40mm to 55mm are considered to be mature and thus produce large amount of eggs compared to clams which have shell length sizes that ranges from 22mm to 39.99mm. The big clams (40mm-55mm) obtained a higher fecundity with the value of 2,200,947 or 2.2x10 raise to the 6th power eggs compared small clams (22mm - 39.99mm) which only got 628,852 of 6.3 x 10 raise to the 5th power eggs. among the factors that affect fecundity, food availability and stress in the environment were found to affect the clams greatly.-"

4. Lacuesta, Vanessa Christine Y. 1999. Some aspects of the reproductive biology of Anodontia edentula Linne, 1758. 41 leaves. Undergraduate thesis. B.S. Biology-U.P. in the Visayas, Iloilo. Available at: CAS Ref./Serials. Anodontia edentula also known as "Imbaw" is an important source of livelihood of some households in the province of Guimaras and in some parts of Panay. This study hoped to give more light on previous studies conducted on the reproductive biology of the species. The study aimed to established a criteria for assessing maturity of the gonads for induced spawning; compare the effectivity of gonad extract and serotonin to induce spawning; determine the number of eggs and the size of eggs spawned for females and the number of sperms spawned for males and to describe the histological appearance of gonad prior to spawning, spent and several days after spawning. The experiment was conducted from September 1998 to February 1999. The broodstock were acquired from barangay were acquired from barangay Lawi, Jorda, Guimaras and transported to the Institute of Aquaculture of the College of Fisheries, UPV, Miag-ao Iloilo. Only clams with shell length greater than or equal to 40mm were used for the experiment. The GSI and the biopsy technique were both employed as bases for assessing gonad maturity prior to induced spawning. Although the difference is insignificant, the GSI's and the ratios of stalked to unstalked oocytes of spawners were higher than nonspawners. For induced spawning, biological stimulation using gonad extract was more effective in terms of inducing female spawners (no. of eggs: 1.89 x 10 raised to the fourth power, egg diameter: 9.5 æ) than chemical stimulation using at least 2.5 mg/ml of serotonin ( no. of eggs : 5.35 x 10 raised to the third power; egg diameter : 8.6 æ ). Serotonin however was more effective in inducing sperm release (2.30 x 10 raised to the fifth power sperms/ml) in clams than the gonad extract (2.22 10 raised to the fourth power sperms/ml). Ripe gonads were an orange-white to creamy white color, turgid with a thin surface covering while spent gonads were flaccid and purplish in color. Histological analyses showed that prespawning males had mature spermatozoa free in the lumen while females had stalked oocytes undergoing vitellogenesis attached to follicular walls; mature, spherical oocytes were also observed. Spent clams had shrunken tubules with developing sperms lining the periphery. Spen female clams had collapsed follicles and only light stained residual oocytes remained at the periphery. An increase in the number of germ cells was observed in gonads several days after spawning.-"

5. Lebata, M. J. H. L. 2000. Elemental sulfur in the gills of the mangrove mud clam Anodontia edentula (family Lucinidae) Journal of Shellfish Research. 19(1):241-245, 2000 Jun.

6. Lebata, M. J. H. L. 2001. Elemental sulphur in the gills of the mangrove mud clam Anodontia edentula: evidence of symbiosis. Journal of Shellfish Research. 20(3):1273-1278, 2001 Dec.

7. Lebata, M. J. H. L. and J. H. Primavera. 2001. Gill structure, anatomy and habitat of Anodontia edentula: Evidence of endosymbiosis. Journal of Shellfish Research. 20(3):1273-1278, 2001

8. Lebata, M. J. H. L.2001. Oxygen, sulphide and nutrient uptake of the mangrove mud clam Anodontia edentula (Family : Lucinidae). Marine Pollution Bulletin. 42(11):1133-1138, 2001 Nov.

9. Millarez, Christian E. 2005. Sex ratio, spawning periodically and sexual dimorphism of the mud clam "imbaw", Anodontia edentula (Linne, 1758), from Nueva Valencia, Guimaras Islands. 37 leaves. Undergraduate thesis-B.S. Biology-U.P. in the Visayas, Iloilo. Available at: CAS Ref./Serials. The study was undertaken on one population of the local mud clam "imbao bayi", Anodontia edentula, to investigate sex ratio and maturity distribution of the population as well as the previously reported sexual dimorphism, spawning periodically and occurence of hermaphroditism. The samples were collected from Brgy. Lawi, Nueva Valencia, Guimaras between August until December, 2004. Results showed that females outnumber males in the population with very rare occurrence of hermaphroditism. In the histological section of the hermaprodite gonad, the female part seemed to be more prominent than the male part. Also, gonadal biopsy showed the population was dominated by mature males and immature females. The fluctuation of their occurrence in the population is related to the spawning activity of the clam. GSI trend confirmed the previous observation that gametogenesis occurred throughout the year and major spawning occurred in the month of Nov. and Dec. Moreover, sexual dimorphism seemed to be apparent in the population sampled; males have a more pointed, triangular umbo while females have a more curved umbo. However, the previously reported height and color dimorphism were found to be insignificant.-"

10. Primavera, J. H., M.J.H.L. Lebata, L. F. Gustilo and J. P. Altamirano. 2002. Collection of the clam Anodontia edentula in mangrove habitats in Panay and Guimaras, Central Philippines. Wetlands Ecol. Mgt. 10:363-370.

11. Samentar, Lorena P. 1997. A preliminary study of the reproductive biology of "Imbaw", Lucinoma annulata (Reeve, 1850).35 leaves. Undergraduate thesis-B.S. Biology-U.P. in the Visayas, Iloilo. Available at: CAS Ref./Serials. Lucinoma annulata, a mud clam locally known as "imbaw" is an important fishery resource which supports the livelihood of some households in Guimaras. Thus, to properly manage this important and fast disappearing resource, knowledge of its reproductive biology is necessary. This study aimed 1) to histoligically describe the gonads of Lucinoma annulata and 2) to determine spawning peaks and reproductive cycle of the mud clam. Monthly samples were collected from July 1996 to February 1997. After the determination of the length and the GSI the clams were processed histologically. Histological examination showed that Lucinoma annulata may either be a hermaphrodite or a female . However, hermaphrodites were more frequently encountered in clams with shell length 25mm to 40mm and also in clams with shell length greater than 55mm. Females were predominant in individuals with shell lengths greater than 40mm to 55 mm. Lucinoma annulata with size range from 25 mm to 70 mm in shell length were found to have either spermatozoa or vitellogenic oocytes in the gonad. However, in hermaphrodite specimens, the male system is the first to produce mature germ cells, which probably suggest a trend towards protandry. Data on GSI showed that the clam might be in active gametogenesis in October and November when GSI was high and spawned in December when GSI was relatively low. The presence of several small peaks implies that spawning is continous in this species. Moreover, the presence of juveniles in the mantle cavity of mature clams suggests brooding in this species. Hermaphroditism and brooding of the young observed in Lucinoma annulata may be an adaptation of this species to overcome difficulties in reproduction and survival.-"

12. Samentar, Lorena P., Minda J. Formacion and Jane S. Geduspan. 2004. Reproductive biology of the mud-dwelling clam, imbaw (Anodontia edentula) in guimaras Province, Central Philippines. UPV J. Nat. Sci. 9(2):217-228. Anodonta edentula, commonly known as imbaw, is an economically important clam found in mangrove areas in Guimaras, Central Philippines that supports the livelihood of many households in the area. To properly manage this economically important shellfish resource, the reproductive biology of this bivalve was studied for a one-year duration. The monthly mean gonadosomatic indices showed regular peaks suggesting that this species spawned throughout the year with highest peak from April to May probably followed by massive spawning thereafter. Histological observations revealed four categories of gonad condition, namely: developing, ripe, spawning and spent. The gonads are surrounded by thick muscular capsule. As the clams increased in shell length, the thickness of muscle and connective tissues dividing the gonads into compartments decreased in size accordingly. A. edentula reached sexual maturity at 35 mm shell length when gonads indicated predominance of either spermatozoa or mature oocytes. The specimens were either male or female, with an occasional

13. Sorongon, Ida P. 1996. A preliminary study of the mollusk locally known as "Imbaw" 1. Characterization and determination of sexual dimorphism. 37 leaves. Undergraduate thesis. B.S. Biology, U.P. in the Visayas, Iloilo. Available at: CAS Ref./Serials. The mollusk, locally known as "Imbaw" belonging to the family of Lucinidae refers to two species of bivalves, identified as Lucinoma annulata and Anodontia edentula under subfamily Myrteinae and Milthinae respectively. Each species has different morpholochical features as they differ in ridges, shell length, width, height, ligament or attachment of both valves and color of periostracum. Internally they differ in gonad color and size. In both species, sexes are separate although little differences can be observed in shell structure to distinguish the female from the male. Gonadal somatic index was found to be greater in females.-"

14. Taylor JD. Glover EA. 2005. Cryptic diversity of chemosymbiotic bivalves: a systematic revision of worldwide Anodontia (Moltusca : Bivalvia : Lucinidae) [Review] Systematics & Biodiversity. 3(3):281-338, 2005 Sep.

15. Teodosio, Joanne Ramos. 2004. A preliminary study of the gonadal maturation of "imbaw", Anodontia edentula (Linne, 1758). 28 leaves. Undergraduate thesis-B.S. Biology-U.P. in the Visayas, Iloilo. Available at: CAS Ref./Serials. The gonadal cycle of "imbaw", Anodontia edentula, a fast-growng mudclam was investigated by histological examination following spawning. This study provided preliminary information about the gonadal stages of imbaw. Gonads and gamete development were observed in imbaw every week after spawning for one month in clams with shell length from 45 mm to 55mm. The increase in the number and size of oocytes and sperm cells for both post-spawning ovary and testis indicates that gametogenesis restarted right away. The presence of residual oocytes after spawning suggests that this species is a partial spawner. Further observations shows that oocyte develops slower than in pserms and that oogenesis may occur in batches. The results suggest that the gametogenic for this species is continuous and mud clams can spawn year round.-"

16. Yu, Rosito D. Jr. 1997. Preliminary study of the gonadal development of "Imbaw Laki", Anodontia edentula (Linne', 1758). 1997. 33 leaves. Undergraduate thesis-B. S. Biology-U.P. in the Visayas, Iloilo. Available at: CAS Ref./Serials. The study aimed (1) To gather preliminary information on the sexual maturation of Anodontia edentula by histological descriptions of the gonad, (2) To correlate shell size with stage of gonadal development , and (3) To determine the size range at which sexual maturity is attained. (p)Eighty-one mud clams were obtained from Panubulon, Nueva Valencia, Guimaras and shell length, width, height, body and gonad weight were measured. The mud clams were categorized into Subclass 4 (60-70 mm) based on shell length. Three to five gonads were randomly selected from each subclass, processed histologically into serial slide sections, and examined under the microscope. Results suggest that Anodontia edentula is hermaphroditic and protandric such that the testicular region is sexually mature at shell lengths of 30mm or less, and the ovarian region at shell lengths of 50-60 mm. The GSI is inversely related to shell length such that as shell length increased, GSI decreased. This attributed to the shrinkage of tissue as spawning and release of gametes progress.-"

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