Salivary Digestion Extends the Range of Sugar-Aversions in the German Cockroach

Saliva has diverse functions in feeding behavior of animals. However, the impact of salivary digestion of food on insect gustatory information processing is poorly documented. Glucose-aversion (GA) in the German cockroach, Blattella germanica, is a highly adaptive heritable behavioral resistance trait that protects the cockroach from ingesting glucose-containing-insecticide-baits. In this study, we confirmed that GA cockroaches rejected glucose, but they accepted oligosaccharides. However, whereas wild-type cockroaches that accepted glucose also satiated on oligosaccharides, GA cockroaches ceased ingesting the oligosaccharides within seconds, resulting in significantly lower consumption. We hypothesized that saliva might hydrolyze oligosaccharides, releasing glucose and terminating feeding. By mixing artificially collected cockroach saliva with various oligosaccharides, we demonstrated oligosaccharide-aversion in GA cockroaches. Acarbose, an alpha-glucosidase inhibitor, prevented the accumulation of glucose and rescued the phagostimulatory response and ingestion of oligosaccharides. Our results indicate that pre-oral and oral hydrolysis of oligosaccharides by salivary alpha-glucosidases released glucose, which was then processed by the gustatory system of GA cockroaches as a deterrent and caused the rejection of food. We suggest that the genetic mechanism of glucose-aversion support an extended aversion phenotype that includes glucose-containing oligosaccharides. Salivary digestion protects the cockroach from ingesting toxic chemicals and thus could support the rapid evolution of behavioral and physiological resistance in cockroach populations.

Salivary Digestion Extends the Range of Sugar-Aversions in the German Cockroach

Saliva has diverse functions in feeding behavior of animals. However, the impact of salivary digestion of food on insect gustatory information processing is poorly documented. Glucose-aversion (GA) in the German cockroach, Blattella germanica, is a highly adaptive heritable behavioral resistance trait that protects the cockroach from ingesting glucose-containing-insecticide-baits. In this study, we confirmed that GA cockroaches rejected glucose, but they accepted oligosaccharides. However, whereas wild-type cockroaches that accepted glucose also satiated on oligosaccharides, GA cockroaches ceased ingesting the oligosaccharides within seconds, resulting in significantly lower consumption. We hypothesized that saliva might hydrolyze oligosaccharides, releasing glucose and terminating feeding. By mixing artificially collected cockroach saliva with various oligosaccharides, we demonstrated oligosaccharide-aversion in GA cockroaches. Acarbose, an alpha-glucosidase inhibitor, prevented the accumulation of glucose and rescued the phagostimulatory response and ingestion of oligosaccharides. Our results indicate that pre-oral and oral hydrolysis of oligosaccharides by salivary alpha-glucosidases released glucose, which was then processed by the gustatory system of GA cockroaches as a deterrent and caused the rejection of food. We suggest that the genetic mechanism of glucose-aversion support an extended aversion phenotype that includes glucose-containing oligosaccharides. Salivary digestion protects the cockroach from ingesting toxic chemicals and thus could support the rapid evolution of behavioral and physiological resistance in cockroach populations.

Perilaku Memilih Umpan Dengan Fagostimulan Yang Berbeda Pada Kecoak Jerman Blattella germanica L. (Dictyoptera: Blattellidae)

Kecoak Jerman (Blattella germanica L.) merupakan salah satu serangga hama permukiman yang penting, karena peranannya sebagai vektor penyakit. Untuk mengurangi populasinya, dapat digunakan dengan teknik pengumpanan. Namun belakangan ini muncul perilaku glucose aversion pada kecoak Jerman terhadap umpan komersial berbasis glukosa sebagai fagostimulan. Oleh karena itu perlu dilakukan kaji ulang terhadap fagostimulan sebagai komponen umpan untuk meminimalisir kegagalan pengendalian kecoak Jerman berbasis umpan dengan menggunakan kecoak Jerman jantan strain VCRU (Vector Control Research Unit). Langkah awal untuk membuat formulasi umpan tersebut adalah mencari fagostimulan yang paling disukai oleh kecoak Jerman. Bahan yang digunakan sebagai fagostimulan adalah gula, durian, erythritol, dan pisang. Tujuan penelitian adalah untuk mengetahui perilaku memilih kecoak Jerman terhadap umpan dengan fagostimulan yang berbeda dan puncak aktivitas makan pada kecoak Jerman. Penelitian ini menggunakan metode eksperimental dengan Rancangan Acak Lengkap (RAL) yang terdiri dari 4 perlakuan pemberian fagostimulan dan diulang sebanyak 4 kali yang terbagi menjadi empat arena uji. Perlakuan terdiri dari umpan yang masing-masing mengandung gula, durian, erythritol, dan pisang sebagai fagostimulan. Pengamatan perilaku menggunakan metode behavior sampling yang dicatat secara continuous recording selama 24 jam menggunakan kamera Closed Circuit Television (CCTV). Parameter yang diukur berupa latensi, frekuensi, durasi, dan puncak aktivitas makan dari kecoak Jerman. Data yang diperoleh dianalisis dengan ANOVA pada p<0.05. Hasil penelitian yang diperoleh menunjukkan bahwa perilaku memilih kecoak jantan strain VCRU terhadap umpan tidak berbeda nyata (p>0.05) dan tertarik dengan semua umpan yang diberikan, tetapi umpan gel dengan fagostimulan gula merupakan umpan yang lebih disukai dengan melihat ketiga parameter latensi, frekuensi, dan durasi. Hasil rata-rata latensi pada strain VCRU menuju gel durian selama 17 menit, rata-rata frekuensi kunjungan terbanyak ke gel gula pada strain VCRU sebanyak 10 kali, rata-rata durasi terlama pada gel gula strain VCRU selama 1 menit 46 detik dan puncak aktivitas makan strain VCRU terjadi antara pukul 17.00 – 20.00.