Provisioning Mass by Females of the Maritime Earwig, Anisolabis maritima, is not Adjusted Based on the Number of Young

The amount of parental provisioning is thought to reflect the need of offspring. This hypothesis was tested in the case of provisioning food mass to young with controlled clutch size using the maritime earwig, Anisolabis maritima Bonelli (Dermaptera: Anisolabididae). The female provisioned a constant mass of food to the young irrespective of the number of nymphs and the distance of food carrying. In addition, the survival rate of young did not change with adjusted clutch size. This study showed that A. maritima females appear to provide food mass to their nymphs independent of their number

ラット ニ オケル テイ カンキョウ カ ノ ホコウ ウンドウ ガ タイ シボウ チクセキ ニ オヨボス エイキョウ

本試験は低温環境下で飼育されるラットの体脂肪減少に対する歩行運動の影響を検討した。試験には3週齢の雄ラット25匹を用いた。個別ケージに収容して,19匹は18±2℃の調温室で,6匹は24±2℃の調温室で7日間予備飼育をした。給与飼料は市販の維持繁殖用固形飼料を用いた。予備飼育の間に平均体重が等しくなるように各区にラットを振り分けた。試験区は試験開始時の体成分を測定する7匹のラットを配した補正区,24±2℃で自由行動のラット6匹を配した区,18±2℃で自由行動のラット6匹を配した区,同様に18±2℃で14m/分の歩行運動を課したラット6匹を配した区とした。増体量,体組成に対する環境温度の影響については18±2℃区と24±2℃区の自由行動を許容した区間で検討した。歩行運動区のラットは18±2℃の環境下で毎日短時間歩行運動に馴らした。本試験期間中の歩行運動は毎日3時間モーター付きの回転槽で行い,対照区のラットも3時間は餌が摂取できないように回収した。試験開始時に補正区のラットはジエチルエーテルで屠殺し,他のラットも4週間後の試験終了時に同様の処理を行い,常法で体組成の成分を分析した。その結果を相互の区間で比較したところ,増体量に有意差は見られなかったが,総飼料摂取量は18±2℃区が有意に(P<0.05)に多くなった。18±2℃区の飼料効率と粗タン白質蓄積率は24±2℃区に比べて有意(P<0.05)に低かった。18±2℃での歩行運動は増体量,飼料摂取量,飼料効率を有意(P<0.05)に低くした。さらに飼料由来の化学成分の蓄積率の結果から,歩行運動区の粗脂肪,熱量の値は対照区に比べて有意(P<0.05)に低くなった。本試験成績において低温環境は飼料摂取量を高めるが,増体量を高めず,適度な歩行運動はその消費エネルギーを飼料中の粗脂肪に由来していることを示唆した。The present study aimed to examine the effects of walking exercise on the body fat deposition of rats fed under low environmental temperature. Twenty-five male rats, aged 3 weeks, were used. They were given commercial feed. The 19 rats at 18±2℃ were divided into three experimental groups as follows : a supplementary group (7 rats) as a donor of start point ; free-moving control group (6 rats) ; and a walking exercise (14m/min.) group (6 rats). The effects of environmental temperature on body weight gain and body composition were then examined comparing the free-moving groups in the 18±2℃ and the 24±2℃ rooms. The 6 rats in the walking exercise group were trained to walk for a short period per day for 7 days. Walking exercise was conducted for 3 hours every day using a walking motor wheel : rats in the control group had their feed removed for 3 hours. At the start of the experiment, the rats in the supplementary group were killed with diethyl ether while the other rats were killed similarly at the end of the experiment (4 weeks later). Chemical composition of the whole body was analyzed, then compared with those of other groups. A comparison of environmental temperature showed no significant difference in body weight gain, but total feed intake for 4 weeks in the 18±2℃ group was significantly (P<0.05) higher than that of the 24±2℃ group. Furthermore, feed efficiency and accumulated ratio of crude protein in the 18±2℃ group were significantly (P<0.05) smaller than those of 24±2℃ group. Walking exercise in a 18±2℃ room temperature significantly (P<0.05) reduced feed intake and feed efficiency. Furthermore, in the results showing the accumulated ratio of chemical composition from feed, the values for ether extracts and calorie in the exercise group were significantly (P<0.05) lower than those of the freree-moving control group. The present result suggests that the low environmental temperature increased feed intake, but it did not affect body weight gain. This indicates that appropriate walking exercise under low environmental temperature may be using energy derived from fat

Biparental negotiation or larval begging? Determinant of male provisioning in a burying beetle (Nicrophorus quadripunctatus)

In species showing biparental care, parents often adjust their level of care facultatively. Partners can potentially monitor each other directly (modify their effort sequentially in direct response to the prior effort of their mate) or indirectly (parents modify their effort through the begging rates of their offspring). This study examined whether partner negotiation or begging by larvae best explains male provisioning in Nicrophoms quadripunctatus. The frequency of males approaching larvae to feed did not increase with either female removal or female handicapping. However, larval begging toward males increased with female removal, but not with female handicapping. This suggests that larvae are not affected by the change of female investment in care but larvae reacted to the absence of a female parent. Although larvae begged more towards the male when the female was removed, my findings show that males did not respond by increasing their care, which suggests that males are insensitive to variation in their partner's state or offspring behaviour in N. quadripunctatus

Host defense in Nicrophorus quadripunctatus against brood parasitism by Ptomascopus morio (Coleoptera: Silphidae: Nicrophorinae)

Few studies have been conducted on the host defenses of insects against brood parasitism. We investigated whether the silphid beetle Ptomascopus morio, a brood parasite of related silphid species Nicrophorus concolor, can also parasitize another silphid species Nicrophorus quadripunctatus and the manner in which N. quadripunctatus defends itself against parasitism. Successful brood parasitism under natural conditions was not observed at the time of year when P. morio and N. quadripunctatus are both reproductively active. Follow-up experiments revealed that P. morio attempts to oviposit near N. quadripunctatus nests, but is rarely successful if adult hosts are present. When P. morio larvae were experimentally introduced to N. quadripunctatus broods, some P. morio larvae survived when the host and parasite larvae were at the same stage. We concluded that N. quadripunctatus defends itself against brood parasitism in two ways: (1) potential brood parasites are repelled, thus limiting their access to the resource; and (2) the young of the parasitic species are killed

Isolation of nine polymorphic microsatellite loci from the burying beetle, Nicrophorus quadripunctatus (Coleoptera: Silphidae)

The burying beetle, Nicrophorus quadripunctatus Kraatz, is a common species in Japan, and its biparental care has been well studied. It exploits small vertebrate carrion as food for its young. Therefore, its reproductive success is restricted to large habitats in which carrion is abundant and available. Hence, the abundance of Nicrophorus species can be used as an indicator of forest fragmentation. Forests have recently become fragmented due to anthropogenic activities, and thus the population sizes of Nicrophorus species have decreased. To investigate the population genetic structure of N. quadripunctatus, we developed polymorphic microsatellite markers using magnetic particles. Nine microsatellites were polymorphic, with two to 12 alleles observed in the samples collected from our study sites, Matsunoyama and Nagaoka A and B. Deviation from the Hardy-Weinberg equilibrium was detected at five to seven loci in each population examined, which is indicative of significant heterozygous deficiencies. Higher genetic diversity was found in the Matsunoyama and Nagaoka B populations, the collection plots of which were covered by continuous woodlands, compared to Nagaoka A. The isolated microsatellite markers will be used to determine the genetic structures of the fragmented populations of N. quadripunctatus

Mate Choice and Copulation Frequency in the Burying Beetle Nicrophorus quadripunctatus (Coleoptera: Silphidae): Effect of Male Body Size and Presence of a Rival

It is widely assumed that there exists a competition between males for mating and that females prefer males with elaborate male traits. Further, such traits are considered to be synonymous with high quality in terms of benefits to females. The number and duration of copulations and the frequency of mate refusal between large and small Nicrophorus quadripunctatus males were examined both for single males and for two males competing. The number of copulations was not affected by the size of the male or by the presence of a rival, but there was a significant interaction such that large males increased their number of copulations when a small rival was present. Copulation duration was not affected by male size but was shortened by a rival male. Females rejected copulation attempts of small males more often than of large males, whether the males were alone or paired with a rival. These results suggest that large males have two advantages: they win contests between males and are preferred by females

Does Experience Affect the Outcome of Male-Male Contests in the Burying Beetle, Nicrophorus quadripunctatus?

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