Go Ogura

CHARACTER DISPLACEMENT AND RELEASE IN THE SMALL INDIAN MONGOOSE, HERPESTES JAVANICUS

In western parts of its native range, the small Indian mongoose (Herpestes javanicus) is sympatric with one or both of two slightly larger congeners. In the eastern part of its range, these species are absent. The small Indian mongoose was introduced, about a century ago, to the West Indies, the Hawaiian islands, Mauritius, the Fijian islands, and Okinawa. All introductions except possibly that to Mauritius were from the region of Calcutta and Bangladesh, where it is sympatric with both congeners. No other mongoose is present on any of these islands. In each instance, the introduced population derived from a small propagule. We examined size variation in the maximum diameter of the upper canine tooth (the prey-killing organ) and skull length. In the eastern (allopatric) part of its native range, males of the small Indian mongoose are much larger in both traits than in the western (sympatric) regions, approaching the size of the smaller of its absent two congeners, Herpestes edwardsii. Females from the allopatric part of the range are also larger than those of the source region. The species is more sexually dimorphic in the region of allopatry. On all islands to which it has been introduced, in 100-200 generations the small Indian mongoose has increased in male size and in sexual dimorphism; changes in female size have been slight and inconsistent. In general, sizes of island individuals are approx- imately intermediate in size between those in the region of origin (where they are sympatric and small) and those in the region of allopatry. Sexual dimorphism is greatest for canine diameter. Thus, H. javanicus shows variation consistent with ecological release from com- petition with its congeners. There is no evidence on whether this variation is genetic, nor on what dietary items might be partitioned between species and between sexes. However, morphological variation is consistently smaller for both traits and both sexes on the islands of introduction than in any part of the native range, consistent with idea of a genetic bottleneck imposed by the small propagule size. Neither of the two congeneric mongooses shows morphological variation consistent with ecological release from competition with H. javanicus in the southern part of their ranges, where the latter species is absent.

Proposal for Japanese encephalitis surveillance using captured invasive mongooses under an eradication project on Okinawa Island, Japan.

A project to eradicate invasive small Asian mongooses (Herpestes javanicus) is underway to conserve the unique ecosystem of Okinawa Island, Japan. In the present study, we tried to elucidate whether the mongoose is a host of Japanese encephalitis virus (JEV) and to evaluate the reliability of surveillance of Japanese encephalitis (JE) using this species. Culex tritaeniorhynchus, the main vector mosquito of JEV, feeds on the mongoose. Eighty-five (35.4%) of 240 wild small Asian mongooses captured between 2001 and 2005 had neutralizing antibodies against more than one of four JEV strains. Prevalence rates of JEV antibodies tended to increase with body weight and length of the animals. One of three sentinel mongooses showed a temporal change in antibody titer. These results indicate that the small Asian mongooses on Okinawa Island are sensitive to JEV. From the antibody titers and the locations of capture, the JEV active area was clarified. We propose that surveillance of JE using mongooses captured under the eradication program is reliable.

The Main Suppressing Factors of Dry Forage Intake in Large-type Goats.

In large-type goats that were fed on dry forage twice daily, dry forage intake was markedly suppressed after 40 min of feeding had elapsed. The objective of this study was to determine whether or not marked decreases in dry forage intake after 40 min of feeding are mainly caused by the two factors, that is, ruminal distension and increased plasma osmolality induced thirst produced by dry forage feeding. Six large-type male esophageal- and ruminal-fistulated goats (crossbred Japanese Saanen/Nubian, aged 2 to 6 years, weighing 85.1±4.89 kg) were used in two experiments. The animals were fed ad libitum a diet of roughly crushed alfalfa hay cubes for 2 h from 10:00 to 12:00 am during two experiments. Water was withheld during feeding in both experiments but was available for a period of 30 min after completion of the 2 h feeding period. In experiment 1, saliva lost via the esophageal fistula was replenished by an intraruminal infusion of artificial parotid saliva (RIAPS) in sham feeding conditions (SFC) control, and the treatment was maintained under normal feeding conditions (NFC). In experiment 2, a RIAPS and non-insertion of a balloon (RIAPS-NB) control was conducted in the same manner as the SFC control of experiment 1. The intraruminal infusion of hypertonic solution and insertion of a balloon (RIHS-IB) treatment was carried out simultaneously to reproduce the effects of changing salt content and ruminal distension due to feed entering the rumen. The results of experiment 1 showed that due to the effects of multiple dry forage suppressing factors when feed boluses entered the rumen, eating rates in the NFC treatment decreased (p<0.05) after 40 min of feeding and cumulative dry forage intake for the 2 h feeding period reduced to 43.8% of the SFC control (p<0.01). The results of experiment 2 indicated that due to the two suppressing factors of ruminal distension and increased plasma osmolality induced thirst, eating rates in the RIHS-IB treatment were, as observed under NFC, reduced (p<0.05) and cumulative dry forage intake for the 2 h feeding period decreased to 34.0% of the RIAPS-NB control (p<0.01). The combined effects of ruminal distension and increased plasma osmolality accounted for 77.5% of the suppression of dry forage intake 40 min after the start of dry forage feeding. The results indicate that ruminal distension and increased plasma osmolality induced thirst are the main factors in the suppression of dry forage intake in large-type goats.

Survey and capture of albino-like house musk shrews (Suncus murinus) in Okinawa, Japan, and a preliminary report regarding inheritance of the albino-like mutation

92008 ?? 33 1214 Received 2.8.2007 ; a cepted 5.5.2008 Copyright

Establishment of a primary hepatocyte culture from the small Indian mongoose (Herpestes auropunctatus) and distribution of mercury in liver tissue

The present study established a primary hepatocyte culture for the small Indian mongoose (Herpestes auropunctatus). To determine the suitable medium for growing the primary hepatic cells of this species, we compared the condition of cells cultured in three media that are frequently used for mammalian cell culture: Dulbecco’s Modified Eagle’s Medium, RPMI-1640, and William’s E. Of these, William’s E medium was best suited for culturing the hepatic cells of this species. Using periodic acid-Schiff staining and ultrastructural observations, we demonstrated the cells collected from mongoose livers were hepatocytes. To evaluate the distribution of mercury (Hg) in the liver tissue, we carried out autometallography staining. Most of the Hg compounds were found in the central region of hepatic lobules. Smooth endoplasmic reticulum, which plays a role inxenobiotic metabolism, lipid/cholesterol metabolism, and the digestion and detoxification of lipophilic substances is grown in this area. This suggested that Hg colocalized with smooth endoplasmic reticulum. The results of the present study could be useful to identify the detoxification systems of wildlife with high Hg content in the body, and to evaluate the susceptibility of wildlife to Hg toxicity.

A Physiological Stimulating Factor of Water Intake during and after Dry Forage Feeding in Large-type Goats.

When ruminants consume dry forage, they also drink large volumes of water. The objective of this study was to clarify which factor produced when feed boluses enter the rumen is mainly responsible for the marked increase in water intake in the second hour of the 2 h feeding period in large-type goats fed on dry forage for 2 h twice daily. Six large-type male esophageal- and ruminal-fistulated goats (crossbred Japanese Saanen/Nubian, aged 2 to 6 years, weighing 85.1±4.89 kg) were used in two experiments. In experiment 1, the water deprivation (WD) control and the water availability (WA) treatment were conducted to compare changes in water intake during and after dry forage feeding. In experiment 2, a normal feeding conditions (NFC) control and a feed bolus removal (FBR) treatment were carried out to investigate whether decrease in circulating plasma volume or increase in plasma osmolality is mainly responsible for the marked increase in water intake in the second hour of the 2 h feeding period. The results of experiment 1 showed that in the WA treatment, small amounts of water were consumed during the first hour of feeding while the majority of water intake was observed during the second hour of the 2 h feeding period. Therefore, the amounts of water consumed in the second hour of the 2 h feeding period accounted for 82.8% of the total water intake. The results of experiment 2 indicated that in comparison with the NFC control, decrease in plasma volume in the FBR treatment, which was indicated by increase in hematocrit and plasma total protein concentrations, was higher (p<0.05) in the second hour of the 2 h feeding period. However, plasma osmolality in the FBR treatment was lower (p<0.05) than compared to the NFC control from 30 min after the start of feeding. Therefore, thirst level in the FBR treatment was 82.7% less (p<0.01) compared with that in the NFC control upon conclusion of the 30 min drinking period. The results of the study indicate that the increased plasma osmolality in the second hour of the 2 h feeding period is the main physiological stimulating factor of water intake during and after dry forage feeding in large-type goats.

Trials for Risk Assessment of Japanese Encephalitis Based on Serologic Surveys of Wild Animals

Japanese encephalitis (JE) is a severe and acute encephalitis with a high fatality rate, caused by Japanese encephalitis virus (JEV), a mosquito-borne flavivirus of the genus Flavivirus, family Flaviviridae. The JEV serogroup of flaviviruses includes West Nile virus, St. Louis encephalitis virus, and Murray Valley encephalitis virus which also cause encephalitis, though with some clinical variation (Mackenzie et al., 2007). JE is a major public health problem in the Asian region, accounting for more than 16,000 reported cases and 5,000 deaths annually. With the near eradication of poliomyelitis, JE is now the leading cause of childhood viral neurological infection and disability in Asia (Halstead and Jacobson, 2003). Approximately half of all survivors suffer from permanent neurological and/or mental impairments due to the invasion and destruction of cortical neurons and Purkinje cells by the virus (Johnson et al., 1985, Monath, 1986). Historically, severe epidemics of JE had been reported during the summer season in Japan since the 19th Century and more than 1000 cases were reported annually in the 1960s. With the control of epidemics in Japan and Korea due to changes in agricultural and animal husbandry practices, and in part through vaccination, the number of JE cases markedly

Induced estrus in female small Asian mongooses (Herpestes javanicus) for the purpose of controlling invasive alien species in Okinawa Island

The small Asian mongoose (Herpestes javanicus) belongs to the family Herpestidae, order Carnivora, and originally inhabited Iraq through northern India to extreme southern China and Indonesia, the Malay Peninsula, Hainan, Java (Nowak 2005). Mongooses, including small Asian mongooses, have been widely introduced by people to exterminate rats for pest control (Yamada and Sugimura 2004). In Japan, small Asian mongooses were introduced to eliminate yellow-spotted pit vipers (Habu snakes; Protobothrops flavoviridis) and sugarcane rats on Okinawa Island in 1910 and Amami-Oshima Island, Kagoshima Prefecture in 1979 (Yamada 2002). Naturalized and overbred mongooses, which prey on insects, reptiles, small mammals, wild birds and domestic fowl, have impacted the poultry industry, and threaten the survival of rare endemic species, such as the Amami rabbit (Pentalagus furnessi), Okinawa rail (Galirallus okinawae) and so on (Yamada 2002). A mongoose eradication project led by the Ministry of the Environment, Government of Japan, has been conducted on Amami-Oshima Island since 1996 and northern Okinawa Island since 2000. Moreover, mongooses were designated as invasive alien species by the Invasive Alien Species Act in Japan (Ministry of the Environment, 2004); however, the eradication project has not yet succeeded. The distribution of mongooses has expanded on Okinawa and Amami-Oshima Islands and, in addition, mongooses were found in Kagoshima city (Kyusyu Island) in 2007. Currently, cage-type traps and cylindrical trapping with bait, chicken meat, have been mainly used for capturing mongooses on Okinawa and Amami-Oshima Islands. Mongoose-drawing techniques require a more effective for increase of the capture number. For effective capture, studies searching for and identifying attractant substances for species-specific capture have been performed in small Asian mongooses, and the previous study attempted to identify volatile fatty acids from anal sac secretions in this species (Ogura et al. 2000b). In the present study, to establish a trapping method with an estrous female or its excreta, we tried to create a protocol to artificially induce estrus in female small Asian mongooses using exogenous hormonal treatment. Estrus was determined based on the profile of urinary estrogen concentrations.