SCIENTIFIC CORRESPONDENCE CURRENT SCIENCE, VOL. 110, NO. 4, 25 FEBRUARY 2016 504 the body of hydra 7 . Long-term exposure to waterborne iron led to a significant accumulation of metal in liver that caused tissue damage in fish 6 . Although iron depositions were not detected in mesoglea, morphometric measurement of mesoglea verified various thickness values (Figure 2), presumably due to its largely non-cellular structure. It is assu- med that mesoglea represents a buffer of some sort 13 . Exposure to iron can cause the retention of water in mesoglea, due to its inability to eliminate excess water from the body by contracting 14 and can enhance synthesis of its constituents, which can thicken mesoglea. In conclusion, non-symbiotic brown hydra exhibited greater susceptibility to iron. Symbiotic green hydra survived better in the given micro-environmental conditions. The present study may point towards the advantages of symbiosis in the living world. 1. Martin, H. M. and Coughtrey, P. 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M., Water Res., 1986, 20, 1137–1147. 13. Kovačević, G., Kalafatić, M. and Horvatin, K., Folia Biol. Krakow, 2009, 57, 139–142. 14. Benos, D. J. and Prusch, R. D., Com- parative Biochemistry and Physiology, Part A. Physiology, 1972, 43, 165–171. ACKNOWLEDGEMENTS. We thank Ms Nadica Vincek for technical assistance. We acknowledge the support of the Ministry of Science, Education and Sport of the Republic of Croatia (project 119-1193080-1214 ‘Mo- lecular phylogeny, evolution and symbiosis of freshwater invertebrates’). Received 6 October 2015; revised accepted 6 November 2015 GORAN KOVAČEVIĆ 1, * ,† GORDANA GREGOROVIĆ 2,† ANA MATIJEVIĆ 3 MIRJANA KALAFATIĆ 1 1 Faculty of Science, University of Zagreb, Department of Biology, Zoology, Rooseveltov trg 6, HR-10000 Zagreb, Croatia 2 Ministry of Health, Ksaver 200a, Department of Pharmaceutical Inspection, HR-10000 Zagreb, Croatia 3 University Hospital Centre Zagreb, Department of Laboratory Diagnostics, Kišpatićeva 12, HR-10000 Zagreb, Croatia *For correspondence. e-mail: goran.kovacevic@biol.pmf.hr † Equally contributed to this paper. Aquilaria malaccensis fruit borer in Peninsular Malaysia Aquilaria malaccensis Lam. (Thyme- laeaceae) has a natural distribution in lowland tropical forests in Peninsular Malaysia, India, Myanmar, Sumatra, Singapore, Borneo and the Philippines. The tree is highly valued for its resin, known as agarwood or popularly known as ‘gaharu’ in the region, which is uti- lized in various products such as perfum- ery, incense, decorative carvings and pharmaceutical products. Agarwood is produced when an agarwood-producing tree is wounded or infected with fungi, microorganisms or insect borers, whereby the borers could also act as a vector of diseases 1 . Only 10% of trees in the wild can become infected by the fungi 2 and produce the much-sought-after resin. Indiscriminate felling of agarwood- producing trees, especially A. malaccen- sis, in the forests has gone beyond con- trol in certain countries. The harvested quantity of agarwood is, however, very low, with less than 0.2 kg per tree for a high-grade resin 3 . A. malaccensis is currently listed as vulnerable according to the IUCN Red List 4 due to overexploitation. Conserva- tion of A. malaccensis is important to en- sure the sustainability of resources, and this requires an understanding of its re- productive biology 5 , which is lacking. Therefore, a series of phenological stud- ies were conducted on wild A. malaccen- sis trees in the forested areas at Penang Island and Perak, Malaysia beginning 2011. The fruits and seeds were also col- lected from each study site by placing 10–20 square-framed nettings measuring 1 m  1 m each under the tree prior to the fruiting season for abortion and germina- tion studies. Damaged fruits were scruti- nized for the presence of insect pests. In Penang, one of the aborted and damaged fruits from a total of 1144 had a mature larva living inside and was seen feeding on the fleshy capsule (Figure 1), whereas in Perak a larva was found in- side an aborted fruit randomly picked from the ground. A hole measuring about 3 mm in diameter was seen penetrating through the capsule into the fleshy part (Figure 2). The larvae were extracted and Figure 1. Larva partially concealed within its feeding tunnel (arrow).