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11. Development of PDF-expressing neurons in the brain of the cricket Gryllus bimaclatus
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Abstracts
9. Caste differences of brain dopamine levels in honeybees Ken Sasaki a, Ken-ichi Harano b, Takashi Nagao a, a Dept. Brain Bioinfo. Sci., Kanazawa Inst. Tech., Ishikawa 924-0838, Japan; b Dept. Agri. Res., Tamagawa Univ., Tokyo 194-8610, Japan The caste in honeybees is a phenotypic plasticity with diverse morphological changes. The behavioral specialization may be caused by physiological and morphological differences in the brains between the castes. It has been reported that the brain dopamine levels in queens are more than five times as high as the workers’ levels, but mechanisms for maintaining the higher levels in queens have not been addressed. We tried to determine the source of dopamine in queens and investigated: (1) dopamine levels in hemolymph; (2) enzymatic activities of the dopamine syntheses in mandibular glands, salivary glands, ovaries and brains; (3) brain dopamine levels at the pupal stage; and (4) dopamine levels in royal jelly and honey. Queens had higher dopamine levels in hemolymph than workers. Dopamine synthesis was mainly detected in the brain tissue. The higher dopamine levels in the brains were found from pupa to adult. Royal jelly contained larger amounts of dopamine than honey. Dopamine in the brain of queens can be supplied from both food and their own synthesis in the brains. doi:10.1016/j.cbpb.2007.07.047
10. Behavioural pattern and visual characteristics of myctophid fish Eiichi Hasegawa a, Kazuhisa Uchikawa b, Kouji Sawada b, Mina Toyama c, Ronald H. Douglas d, a Fisheries Research Agency, National Salmon Resources Center, Sapporo 062-0922, Japan; b Fisheries Research Agency, National Research Institute of Fisheries Engineering, Ibaraki 314-0408, Japan; c Hamamatsu University School of Medicine, Shizuoka 431-3192, Japan; d City University London, London EC1V 0HB, UK A vertical movement of myctophids is classified into the following four types: (1) species that remarkable circadian rhythm is shown; (2) species that individual that shows circadian rhythm and individual not shown exist together in homogeneous; (3) species that does not surface so much at night time though circadian rhythm is shown; and (4) species that does not show circadian rhythm at all. As for the species in which remarkable circadian rhythm was shown, the feature in the retina form that outer segment of rod was short and outer nuclear layer was thick was observed. Moreover, it had only rhodopsin of λmax ≈490 nm in most species, but in the Myctophum nitidulum that showed circadian rhythm remarkably, most unusually for a deep-sea fish, contains both a rhodopsin visual pigment absorbing maximally (λmax) at 468 nm and a porphyropsin with λmax 522 nm. The λmax values of these two visual pigments are too far apart to form a rhodopsin/porphyropsin ‘pigment pair’, suggesting they are based on distinct opsins, giving M. nitidulum one of the broadest spectral ranges of all deep-sea fish. This might be an adaptation to the detection of both long-wave bioluminescence and residual shorter-wave surface illumination, and could be related to this animal’s tendency to migrate towards surface waters at night. doi:10.1016/j.cbpb.2007.07.048
11. Development of PDF-expressing neurons in the brain of the cricket Gryllus bimaclatus Sayoko Narahara, Miki Shimohigashi, Dept. Biol., Fac. Sci., Fukuoka Univ., Fukuoka 814-0180, Japan
Pigment-dispersing factor (PDF), an 18-amino acid neuropeptide, is a pacemaker hormone that plays an important role in the locomotor rhythm in insects. In this study, the development of PDF-expressing neurons in the accessory medulla of the cricket Gryllus bimaclatus was studied using antisera raised against Gryllus PDF. In the first to the third instar nymph, the number of PDF immunostained cells in the
accessory medulla was counted to be nine, and that of the fourth to the last instar was ten. In the adult, their number was increased up to fourteen. Although their axonal terminals in the central brain resembled entirely through all the stages of nymph, the additional axons were observed in the different area of the protocerebrum from those in the nymphs in the mature adult male. Thus, PDF-expressing neurons in adults were suggested to play a role not only in the locomotor rhythm but also in another physiological function. doi:10.1016/j.cbpb.2007.07.049
12. Neuroethological study of bitter taste reception in the axolotl (Ambystoma mexicanum) Hiro-aki Takeuchi, Miyuki Sakai, Dept. Biol., Grad. Sch. Sci., Shizuoka Univ., Shizuoka 422-8529, Japan
Our behavioral and electrophysiological experiments suggested that the aquatic amphibian, axolotl, prefers salty taste at the lower concentration and hates sour and bitter tastes, and that the salt taste transduction is not primarily mediated by amiloride-sensitive sodium channels in the axolotl. In the present study, we examined the mechanism of bitter taste reception by using a bitter-masking material “BENECOAT BMI-40 (Kao Corporation, Japan)” that selectively suppressed the bitter taste sensation in the human and bullfrog. The bitter taste sensation of axolotl was quantified by the rejection ratio [rejection / (rejection + swallowing)] after snapping the gel pellets containing a bitter substance (quinine hydrochloride, denatonium benzoate or caffeine). When 3.0% BMI-40 was added to a bitter gel pellet, the rejection ratio was significantly decreased at 1–10 mM quinine hydrochloride and 0.001–0.01 mM denatonium benzoate. On the other hand, addition of BMI-40 to a sour gel pellet showed no effect at 0.01– 0.15 M citric acid. These results suggest that the taste masking effect of BMI-40 is selective to bitter taste sensation in the axolotl. Therefore, the mechanism of bitter taste reception in the axolotl may be similar to those in the human and bullfrog. doi:10.1016/j.cbpb.2007.07.050
13. The relationship between the compensational recovery of the response rate of wind-evoked escape and the sensory input in unilaterally cercus-ablated crickets, Gryllus bimaculatus Hiroyuki Takuwa a, Natsuko Nakamura a, Masamichi Kanou b, a Dept. Biol. Ear. Sci., Fac. Sci., Ehime Univ., Bunkyo-cho 790-8577, Japan; b Dept. Biol., Grad. Sch. Sci. Eng., Ehime Univ., Bunkyo-cho 790-8577, Japan
An artificial wind stimulus evokes an escape behavior in the cricket, Gryllus bimaculatus. The wind stimulus is detected by mechanosensitive filiform hairs located on a pair of cerci. The relative occurrence of the wind-evoked escape decreased just after the ablation of one of a pair of cerci. However, when the cricket was reared under a condition permitting walking, the response rate of the cricket showed compensational recovery almost 6 days after the ablation. In the present study, the distal end of the abdomen of a unilaterally cercus-ablated cricket was covered with a plastic tube in order to eliminate sensory inputs to remaining cercal filiform hairs. They were reared under a condition prohibiting free walking for 6 days after the ablation. The recovery of the response rate was not observed in the crickets. Then, the plastic tube was removed and the cricket was reared in a large cage during another 6 days. The compensational recovery of the response rate was not observed even after the rearing. These results suggest that sensory inputs from cercal filiform hairs during first 6 days after the unilateral cercal ablation is essential for a cricket to recover the response rate of the wind-evoked escape. doi:10.1016/j.cbpb.2007.07.051
Abstracts
9. Caste differences of brain dopamine levels in honeybees Ken Sasaki a, Ken-ichi Harano b, Takashi Nagao a, a Dept. Brain Bioinfo. Sci., Kanazawa Inst. Tech., Ishikawa 924-0838, Japan; b Dept. Agri. Res., Tamagawa Univ., Tokyo 194-8610, Japan The caste in honeybees is a phenotypic plasticity with diverse morphological changes. The behavioral specialization may be caused by physiological and morphological differences in the brains between the castes. It has been reported that the brain dopamine levels in queens are more than five times as high as the workers’ levels, but mechanisms for maintaining the higher levels in queens have not been addressed. We tried to determine the source of dopamine in queens and investigated: (1) dopamine levels in hemolymph; (2) enzymatic activities of the dopamine syntheses in mandibular glands, salivary glands, ovaries and brains; (3) brain dopamine levels at the pupal stage; and (4) dopamine levels in royal jelly and honey. Queens had higher dopamine levels in hemolymph than workers. Dopamine synthesis was mainly detected in the brain tissue. The higher dopamine levels in the brains were found from pupa to adult. Royal jelly contained larger amounts of dopamine than honey. Dopamine in the brain of queens can be supplied from both food and their own synthesis in the brains. doi:10.1016/j.cbpb.2007.07.047
10. Behavioural pattern and visual characteristics of myctophid fish Eiichi Hasegawa a, Kazuhisa Uchikawa b, Kouji Sawada b, Mina Toyama c, Ronald H. Douglas d, a Fisheries Research Agency, National Salmon Resources Center, Sapporo 062-0922, Japan; b Fisheries Research Agency, National Research Institute of Fisheries Engineering, Ibaraki 314-0408, Japan; c Hamamatsu University School of Medicine, Shizuoka 431-3192, Japan; d City University London, London EC1V 0HB, UK A vertical movement of myctophids is classified into the following four types: (1) species that remarkable circadian rhythm is shown; (2) species that individual that shows circadian rhythm and individual not shown exist together in homogeneous; (3) species that does not surface so much at night time though circadian rhythm is shown; and (4) species that does not show circadian rhythm at all. As for the species in which remarkable circadian rhythm was shown, the feature in the retina form that outer segment of rod was short and outer nuclear layer was thick was observed. Moreover, it had only rhodopsin of λmax ≈490 nm in most species, but in the Myctophum nitidulum that showed circadian rhythm remarkably, most unusually for a deep-sea fish, contains both a rhodopsin visual pigment absorbing maximally (λmax) at 468 nm and a porphyropsin with λmax 522 nm. The λmax values of these two visual pigments are too far apart to form a rhodopsin/porphyropsin ‘pigment pair’, suggesting they are based on distinct opsins, giving M. nitidulum one of the broadest spectral ranges of all deep-sea fish. This might be an adaptation to the detection of both long-wave bioluminescence and residual shorter-wave surface illumination, and could be related to this animal’s tendency to migrate towards surface waters at night. doi:10.1016/j.cbpb.2007.07.048
11. Development of PDF-expressing neurons in the brain of the cricket Gryllus bimaclatus Sayoko Narahara, Miki Shimohigashi, Dept. Biol., Fac. Sci., Fukuoka Univ., Fukuoka 814-0180, Japan
Pigment-dispersing factor (PDF), an 18-amino acid neuropeptide, is a pacemaker hormone that plays an important role in the locomotor rhythm in insects. In this study, the development of PDF-expressing neurons in the accessory medulla of the cricket Gryllus bimaclatus was studied using antisera raised against Gryllus PDF. In the first to the third instar nymph, the number of PDF immunostained cells in the
accessory medulla was counted to be nine, and that of the fourth to the last instar was ten. In the adult, their number was increased up to fourteen. Although their axonal terminals in the central brain resembled entirely through all the stages of nymph, the additional axons were observed in the different area of the protocerebrum from those in the nymphs in the mature adult male. Thus, PDF-expressing neurons in adults were suggested to play a role not only in the locomotor rhythm but also in another physiological function. doi:10.1016/j.cbpb.2007.07.049
12. Neuroethological study of bitter taste reception in the axolotl (Ambystoma mexicanum) Hiro-aki Takeuchi, Miyuki Sakai, Dept. Biol., Grad. Sch. Sci., Shizuoka Univ., Shizuoka 422-8529, Japan
Our behavioral and electrophysiological experiments suggested that the aquatic amphibian, axolotl, prefers salty taste at the lower concentration and hates sour and bitter tastes, and that the salt taste transduction is not primarily mediated by amiloride-sensitive sodium channels in the axolotl. In the present study, we examined the mechanism of bitter taste reception by using a bitter-masking material “BENECOAT BMI-40 (Kao Corporation, Japan)” that selectively suppressed the bitter taste sensation in the human and bullfrog. The bitter taste sensation of axolotl was quantified by the rejection ratio [rejection / (rejection + swallowing)] after snapping the gel pellets containing a bitter substance (quinine hydrochloride, denatonium benzoate or caffeine). When 3.0% BMI-40 was added to a bitter gel pellet, the rejection ratio was significantly decreased at 1–10 mM quinine hydrochloride and 0.001–0.01 mM denatonium benzoate. On the other hand, addition of BMI-40 to a sour gel pellet showed no effect at 0.01– 0.15 M citric acid. These results suggest that the taste masking effect of BMI-40 is selective to bitter taste sensation in the axolotl. Therefore, the mechanism of bitter taste reception in the axolotl may be similar to those in the human and bullfrog. doi:10.1016/j.cbpb.2007.07.050
13. The relationship between the compensational recovery of the response rate of wind-evoked escape and the sensory input in unilaterally cercus-ablated crickets, Gryllus bimaculatus Hiroyuki Takuwa a, Natsuko Nakamura a, Masamichi Kanou b, a Dept. Biol. Ear. Sci., Fac. Sci., Ehime Univ., Bunkyo-cho 790-8577, Japan; b Dept. Biol., Grad. Sch. Sci. Eng., Ehime Univ., Bunkyo-cho 790-8577, Japan
An artificial wind stimulus evokes an escape behavior in the cricket, Gryllus bimaculatus. The wind stimulus is detected by mechanosensitive filiform hairs located on a pair of cerci. The relative occurrence of the wind-evoked escape decreased just after the ablation of one of a pair of cerci. However, when the cricket was reared under a condition permitting walking, the response rate of the cricket showed compensational recovery almost 6 days after the ablation. In the present study, the distal end of the abdomen of a unilaterally cercus-ablated cricket was covered with a plastic tube in order to eliminate sensory inputs to remaining cercal filiform hairs. They were reared under a condition prohibiting free walking for 6 days after the ablation. The recovery of the response rate was not observed in the crickets. Then, the plastic tube was removed and the cricket was reared in a large cage during another 6 days. The compensational recovery of the response rate was not observed even after the rearing. These results suggest that sensory inputs from cercal filiform hairs during first 6 days after the unilateral cercal ablation is essential for a cricket to recover the response rate of the wind-evoked escape. doi:10.1016/j.cbpb.2007.07.051