CHARACTERISATION OF POMACEA CANALICULATA EGGS TREATED WITH PROTEASE
Authors: Mohd Salleh Noor hasyierah , Zainalabidin Nurhadijah , Md Latip Siti Noor Hajjar 
Published: January 2024

Pomacea canaliculata is a type of freshwater snail that has become a major pest in paddy fields, as it feeds on young paddy leaves and stems, thus, posing a serious threat to paddy production. It was named one of the world's top 100 worst invasive species, with serious consequences for the environment, human health, and the social economy. Their hatchability rate is high, which explains their global distribution worldwide. Therefore, it is vital to manage their hatchability to prevent their population from expanding further by understanding the protection that permits the eggs to survive. P. canaliculata eggs are covered with a thin layer of cuticle that is rich in protein to protect the embryo during the hatching process. The biological treatment with protease enzyme successfully hydrolysed the protein cuticle layer, lowering the percentage of hatchability. Disruption of the protein cuticle may have an impact on conductivity, water loss, hatching time, protein content, and other factors. However, documentation of the protease effect on the protein cuticle is scarce. Therefore, the goal of this study is to evaluate the protease treatment on the protein cuticle of P. canaliculata eggs physically (conductivity, water loss, and morphological analysis) and chemically (cuticle protein content, protein breakdown, and amino acid profile). Physical characterisation revealed that protease-treated eggs have higher conductivity and water loss than the control egg. Images taken with a light microscope (LM) and a scanning electron microscope (SEM) revealed changes in cuticle structure, which explained the protease-induced cuticle hydrolysis. Chemical characterisation revealed a decrease in cuticle protein content, hydrolysis of protein to a small size, and changes in amino acid composition. The physical and chemical analyses strongly suggested that protease can damage the cuticle protein, thus, preventing the eggs from hatching. ABSTRAK: Pomacea canaliculata adalah sejenis siput air tawar yang telah menjadi perosak utama di sawah padi, kerana ia memakan daun dan batang padi yang muda, sekaligus menimbulkan ancaman serius kepada pengeluaran padi. Ia disenaraikan antara 100 spesis invasif utama dunia dengan kesan serius pada alam sekitar, kesihatan manusia dan sosio-ekonomi. Kadar penetasannya adalah tinggi, meningkatkan penyebaran mereka secara global di seluruh dunia. Oleh itu, adalah sangat penting untuk mengawal populasi ini daripada terus berkembang dengan memahami perlindungan yang membenarkan telur untuk hidup. Telur P.canaliculata dilapisi dengan lapisan kutikel nipis yang kaya dengan protein bagi memberi perlindungan untuk embrio semasa proses penetasan. Rawatan biologi dengan enzim protease telah berjaya menghidrolisis lapisan kutikel protein, sekaligus mengurangkan peratusan penetasan. Gangguan terhadap lapisan kutikel protein mungkin memberi kesan pada konduktiviti, kehilangan air, tempoh penetasan, kandungan protein dan faktor lain. Walau bagaimanapun, kesan protease ke atas kutikel protein adalah kurang. Oleh itu, objektif kajian ini adalah mengkaji rawatan protease ke atas kutikel protein telur P. canaliculata secara fizikal (konduktiviti, kehilangan air, dan analisis imej kutikel) dan secara kimia (kandungan protein kutikel, pecahan protein dan profil asid amino). Ciri fizikal menunjukkan telur yang dirawat protease mempunyai konduksi dan kehilangan air tinggi berbanding telur kawalan. Imej yang diambil dengan mikroskop cahaya (LM) dan mikroskop pengimbas elektron (SEM) mendedahkan perubahan dalam struktur kutikel, yang menjelaskan hidrolisis kutikel yang disebabkan oleh protease. Ciri kimia menunjukkan penurunan kandungan protein kutikel, saiz kecil pada hidrolisis protein, dan perubahan pada kandungan asid amino. Analisis fizikal dan kimia mencadangkan bahawa protease merosakkan protein kutikel, oleh itu menghalang telur daripada menetas.