Studies on differentiation of species and distribution of surinam cockroaches inhabiting in Japan

• Material Type: 博士論文
• Title: Studies on differentiation of species and distribution of surinam cockroaches inhabiting in Japan
• Author/Editor: 小松, 謙之
• Author Heading: 小松, 謙之
• Publication Date: 2015-07-08
• Publication Date (W3CDTF): 2015-07-08
• Alternative Title: 日本に生息するオガサワラゴキブリの種の鑑別および分布に関する研究
• Degree grantor/type: 麻布大学
• Date Granted: 2015-07-08
• Date Granted (W3CDTF): 2015-07-08
• Dissertation Number: 乙第26号
• Degree Type: 博士(学術)
• Conferring No. (Dissertation): 乙第26号
• Text Language Code: eng
• Target Audience: 一般
• Note (General): オガサワラゴキブリ（Common name : Surinam cockroach）は、世界の熱帯、亜熱帯に広く分布する害虫であり、国内では鹿児島から南西諸島、小笠原諸島などに分布している。近年、このゴキブリが、我が国の都市部の建築物内にも侵入し、捕獲や駆除が報告されはじめている。また海外においても、同様に都市部の家屋内への侵入が問題となっている。疫学的には、エチアピアにおいて、Kinfu and Erko (2008) は、このゴキブリの体表から、ヒトに感染性をもつ蠕虫類の回虫卵やテニア科条虫卵を検出し、さらに腸管からは、これらに加え、鞭虫卵や原虫類である大腸アメーバのシストの検出を報告しており、感染症を媒介する衛生害虫としても注目されている。 オガサワラゴキブリに関しては、形態的に良く似た2種が知られており、両性生殖を行うPycnoscelus indicusと、単為生殖を行うPycnoscelus surinamensis が存在する。P. indicusとP. surinamensisの種の分類方法については、Roth（1967）が成虫を用いた交配実験を行い、受精嚢内に精子があるにもかかわらず、雌のみを産出した個体をP. surinamensis、雌雄を産出した個体をP. indicusとしている。また、形態的な違いとしてP. indicus は複眼と単眼点の距離が離れているのに対して、P. surinamensis は両眼が接していることで区別できるとしている。 P. indicus の雄は雌に比べて乾燥に弱く、生育環境が適切でないと雄が死んでしまうため交尾ができず、繁殖することはできない。ところが、P. surinamensis は繁殖に雄は必要ないため、雌が1匹でも生息すれば多少環境が悪くても侵入した場所で繁殖を繰り返すことが可能である。 朝比奈（1991）は、日本産の個体は、雌雄が常に同時に採集されており、雌だけの単為生殖の系統は観察されないことから、日本に生息する個体はP. indicusである可能性を示唆した。しかしながら、日本産のオガサワラコギブリを用いた詳細な実験による証明が行なわれるまでは、従来のP. surinamensisとすることを提唱し、今日に至っている。このように、オガサワラゴキブリは衛生害虫として重要なゴキブリでありながら、種の鑑別と分布がまったく不明なのが現状である。 そこで本研究では、成虫にまで発育する前に雌雄の区別ができるように、まず幼虫期における雌雄の鑑別方法の確立を行った。ゴキブリ類の幼虫期における雌雄の鑑別については、トウヨウゴキブリBlatta orientalis、チャオビゴキブリSupella longipalpa、クロゴキブリPeriplaneta fuliginosaで確立されており、幼虫期の腹板の形態により鑑別可能であることが報告されている。そこで、沖縄県八重山郡竹富町石垣島で採集し、予備実験により産仔幼虫が雌雄の成虫に発育することを確認した個体群を使用して実験を行い、孵化直後の幼虫を腹板の形態ごとにグループに分け、成長段階における腹板の形状を記録し、最終的に各グループの個体が雌雄のどちらになるかを調べた。その結果、雌では1～6齢期の幼虫において第9腹板の後縁中央部に雄では見られないnotch（V字型）を有し、7齢（終齢）期では、第７腹板が発達して第8～9腹板および尾突起を覆い隠した。これに対して雄では7齢期まで第8～9腹板、尾突起がみられた。したがって、この特徴を観察することによって幼虫期の雌雄鑑別が可能であることが判明した。 次に幼虫期の齢期を判定するため、尾肢の腹面および背面の環節数を計測した。その結果、背面の環節数は2、3齢で同数となり判定できないが、腹面の環節数は1齢幼虫で3節、2齢幼虫で4節と加齢するごとに1節ずつ増加することが分かり、この部位の環節数を調べることにより幼虫の齢期の判定が可能となった。 これらの結果をもとに、日本に生息するオガサワラゴキブリの種と分布を明らかにするため、小笠原諸島（硫黄島・母島・父島・西島・媒島）、奄美諸島（徳之島・奄美大島）、沖縄諸島（沖縄島・宮古島・石垣島）、ハワイ島から採集した雌成虫を単独で飼育し、実験に用いる個体の繁殖を行った。その結果、硫黄島・徳之島・沖縄島は、雌のみを産出する個体と、雌雄を産出する個体が見られたため、前者をAグループ、後者をBグループとして11地域14系統の個体群を使用して交配実験を行った。 交配実験は、雌のみを産出する個体群には、Roth（1967）と同様にP. indicusと判明しているハワイ産の雄を使用し、雌雄産出する個体群は、その個体群内の雄を使用した。その結果、1地域で2系統見られた硫黄島、徳之島、沖縄島では、硫黄島Aグループの個体での産出数は、雄0個体、雌478個体で、産出後のすべての各個体における受精嚢内に精子を保有していたことよりP. surinamensisであった。硫黄島Bグループは、雄162個体、雌157個体を産出し、1回の平均産仔数の雄雌比は、10.8：10.5（p＞0.05）で、性比に有意差は認められずP. indicusであった。徳之島Aグループは、雄0個体、雌221個体を産出し、すべて受精嚢内に精子を保有していたことよりP. surinamensisであった。徳之島Bグループは、雄242、雌207を産出し、1回の平均産仔数の雄雌比は12.1：10.4（p＞0.05）で、性比の有意差は認められずP. indicusであった。沖縄島Aグループは、雄0個体、雌724個体を産出し、すべての受精嚢に精子が保有されていたことよりP. surinamensiであった。沖縄島Bグループは、雄322、雌312を産出し、1回の平均産仔数の雄雌比は16.1：15.6（p＞0.05）で、性比の有意差は認められずP. indicusであった。以上の結果より、硫黄島、徳之島、沖縄島は、P. surinamensisとP. indicus の2種が同時に生息していることが初めて明らかとなった。 雌のみが産出された母島・父島・西島・媒島の個体のうち、母島の受精嚢に精子が確認された個体での産出数は、雌248個体、父島の精子が確認された個体での産出数は、雌59個体、西島の精子が確認された個体の産仔数は、雌663個体、媒島の精子が確認された個体での産出数は、雌143個体であったことから、以上4島の個体は全てP. surinamensis であることが明らかとなった。 雌雄産出した個体のみであった奄美大島・宮古島・石垣島では、奄美大島の個体は、雄260、雌260で、1回の平均産仔数が14.4：14.4（p＞0.05）であった。宮古島の個体は、雄230、雌267で、1回の平均産仔数が16.4：19.1 (p＞0.05) であった。石垣島の個体は、雄281、雌266で、1回の平均産仔数が16.5：15.6（p＞0.05）であった。ハワイ島の個体は、雄199、雌189で、1回の平均産仔数が11.7：11.1（p＞0.05）であり、以上4島の個体はすべてP. indicusであることが明らかとなった。 以上の結果より、日本にはP. indicusとP. surinamensisの2種類が生息しており、これらが混生している地域、およびP. indicusのみ、あるいはP. surinamensisのみが生息する地域があることが明らかとなった。 次に、実験により種が判明した個体を使い、この2種類の形態的な違いを調べた。Roth（1967）は、複眼と単眼点が接していればP. surinamensis、離れていればP. indicusであるとしたが、本実験ではP. surinamensis の雌成虫の複眼と単眼点は接しておらず、その距離は、母島0.16㎜＞父島0.14㎜＞媒島0.13㎜＞西島・徳之島・沖縄島0.12㎜＞硫黄島0.10㎜となり、平均0.13㎜であった。一方、P. indicus 雌成虫の複眼と単眼点の距離は、硫黄島 0.18㎜＞宮古島0.16㎜＞奄美大島・沖縄島 0.13㎜＞徳之島・石垣島0.12㎜で、平均0.15㎜となり、どちらの種も接しておらず、両種の複眼と単眼点の距離による鑑別は不可能であった。 また、昆虫類の種の違いとして前翅長の違いが広く利用されているため、雌成虫の平均前翅長を計測した。その結果、P. surinamensisは、沖縄島15.82㎜＞母島15.26㎜＞西島15.07㎜＞媒島14.16㎜＞父島13.81㎜＞徳之島13.57㎜＞硫黄島12.87㎜、P. indicus 雌成虫の平均前翅長は、沖縄14.72㎜＞硫黄島14.35㎜＞石垣島13.81㎜＞徳之島13.54㎜＞奄美大島13.53㎜＞宮古島12.96㎜と、地域的な差異が大きく、両種を鑑別することはできなかった。 一方、交配実験を行わなくても種を鑑別できる方法を検討するため、本実験で得られた各雌成虫の未交尾個体による飼育実験を行った。その結果、P. surinamensisはすべての個体が幼虫を産出し、前述した幼虫期の雌雄鑑別法により、すべてが雌であることがわかった。一方、P. indicusはすべての個体で幼虫は産出しなかった。このことより、野外で採集した雌成虫の同定法として、産仔幼虫がすべて雌であった場合はP. surinamensis、また雌雄を産出、あるいはまったく産出しない場合はP. indicusと同定できることが判明した。 以上、本研究により、これまで日本に生息するオガサワラゴキブリはP. surinamensisのみであると考えられていたが、P. indicusも同時に生息していることが明らかとなり、これらの結果から、日本に生息するゴキブリは1種増えて58種となった。さらに、現在までP. indicusとP. surinamensisは生息地域が違うと考えられてきたが、2種類が同一地域に混生している事実が明らかになり、今後の研究の方向性を再検討する必要がある。また、Roth（1967）が提唱している複眼と単眼点の距離による形態をもとにした鑑別方法は利用できないことがわかった。これに替わる新たな鑑別方法として、交配実験を行わなくとも未交尾の雌個体であれば、そのまま飼育して産仔すればP. surinamensis、産仔しなければP. indicusと判断でき、野外採集個体であれば、産出された幼虫が雌のみであればP. surinamensis、雌雄産出すればP. indicusと判断できることがわかった。朝比奈（1991）の報告では、我が国におけるオガサワラゴキブリの種に関する知見が明確ではなかったが、本研究における種々の交配実験や形態的な観察により、その詳細が明らかとなった。; The so-called “Ogasawara cockroaches”, which hitherto has also been synonymously called “Surinam cockroaches”, are widely distributed throughout the world in the tropical and sub-tropical areas. In Japan, their distribution is limited to Kagoshima in Kyushu and the island chain of Nansei and Ogasawara island chain. In recent years, this cockroach has invaded into urban buildings and abode, resulting in the report of their capture or eradication attempts. The problem of urban buildings invasion by this cockroach has also been seen in other countries. From an epidemiological perspective, Kim and Erko (2008) reportedly detected the potentially zoonotic helminth ascarid and taeniid eggs on the body surface of this species of cockroach in Ethiopia. Furthermore, they also reported the presence of trichurid eggs and Entamoeba coli cyst in the digestive tract of the cockroach. These findings has put the spotlight on the role of the cockroach as a potential mechanical transmitter zoonotic infectious diseases.Regarding the constituent species of the so-called “Ogasawara cockroaches” or “Surinam cockroaches”, it seem that there were two apparently morphologically similar species, namely Pycnoscelus indicus and Pycnoscelus surinamensis, with the former showing bisexual reproduction and the latter, parthenogenesis. For the identification of these two species, Roth (1967) proposed that for the adults, irrespective of the presence or absence of sperms in the spermatheca, those which produce only female offspring should be identified as Pycnoscelus surinamensis, while those that produce both male and female offspring should be relegated as Pycnoscelus indicus. Moreover, he also reported that there were morphological differences between the two aforementioned species, based on the distance between the compound eye and ocelli. In P. indicus, the ocelli and the compound eyes were separated, whereas in P. surinamensis, the two eyes were in contact.The male of P. indicus are relatively more susceptible to dryness than the female, and easily died off under non-optimal environmental condition, leading to reduced chances of mating. However, since P. surinamensis is parthenogenetic and does not need male to reproduce, they can even proliferate under a harsh environmental condition if a single female is able to invade and survive under that condition.Asahina (1991) reported that both male and female individuals could always be found among the “Ogasawara cockroaches”, without noting that the female were parthenogenetic. This led him to suspect that the Japanese “Ogasawara cockroaches” might include P. indicus. However, he proposed that until the detailed breeding experiments had been carried out, the “Ogasawara cockroaches” should all be tentatively be identified as P. surinamensis. Thus, despite that the Ogasawara cockroaches has been recognized as a pest, their species identification and distribution has not been clearly elucidated.To clarify the species involved, first of all, we need to establish a criteria be able to identify the sex of the cockroach at the larval stage before they mature into set out to establish a method to differentiate the sex of male and female cockroach from the larval stage to the adult stage. Sexual differentiation of the cockroach nymph for all the instar stages of Blatta orientalis, Supella longipalpa and Periplaneta fuliginosa has been established, based on the morphological observation of the abdominal segments of the in star.In our study, cockroaches were collected in Ishigaki island, Taketomi-cho, district, Okinawa prefecture, Japan. They were then reared and passaged for several generations in the laboratory. Only those groups that produced offspring, which matured into male and female adults were used in the following experiment. The instar that hatched from the eggs were immediately isolated and separated according to their morphoplogical characteristic of ventral segments. Changes on the ventral segment were also noted for each instar stages and ultimately, the sex of the mature adult for each group was determined. Using the aforementioned method, the female of the 1st to 6th stage instar nymph were found to possess a V-shaped notch at the middle of the posterior edge of the 9th sternite. This notch was not seen in the male nymph. In the female 7th stage (final stage) instar nymph, the styli were not apparent and, the 8th and 9th sternites became degenerated and were covered over by the profoundly developed 7th sternite. In contrast, all stages of the male nymph until the 7th stage nymph showed the presence of the 8th and 9th sternitesas well as styli. Based on these observations, our study has demonstrated that it is possible to differentiate the sex of the Indian cockroach, P. indicus, at different developmental stages.Next, to identify the various specimens as to which stage the nymph instar belong to, we counted the number of cercal segments from the dorsal and ventral view. It was observed that the number of cercal segments from the dorsal view in 2nd and 3rd stage nymph were the same, that is 4 and thus could not be used to identify the nymph stage. However, when viewed ventrally, it was observed that the number of cercal segments on the1st stage nymph was 3; 2nd stage, 4; and in the subsequent stages, an increase of one extra segment for each stage. The number of cercal segments of all the stages of the female, right up to the 7th stage nymph, when viewed ventrally were the same as that of the male nymph. Therefore, the developmental stage of the nymph could be identified by examining the number of segments from the ventral view.Based on the above results, we set out to confirm species and distribution of Surinam cockroaches inhabiting Japan. We collected cockroaches from Ogasawara island chain (Iwoto, Hahajima, Chichijima, Nishijima, Nakodojima), Amami island chain (Tokunoshioma, Amamiooshima), Okinawa island chain (Okinawato, Miyakojima, Ishigakijima) and Hawaii, kept the female in solitary rearing for use in later mating experiments. Cross breeding experiments that were carried out showed that there were those cockroaches from Iwoto, Tokunoshima, and Okinawato that produced only female offspring, and also that produced both male and female offspring. The former group was designated A group and the latter, B group. Both groups comprises of 14 isolates from 11 areas. The cockroaches from both groups were then used for subsequent cross breeding experiments. For the cross breeding experiments, those specimens that produced only female offspring were mated with those male from Hawaii that had produced both male and female offspring and had been identified a P. indicus as previously reported by Roth (1967). From the results of our study, the area that contain the two different characteristic types of the cockroaches were Iwoto, Tokunoshima and Okinawato, whereas an individuals of Iwoto- A group, which produced a total of 478 female and no male offspring, despite having sperms in their spematheca, can be identified as P. surinamensis. On the contrary, while those of Iwoto-B group with all having sperms in their spermatheca, produced a total of 168 male and 157 female offspring in an average ratio of 10.8 to 10.5 (p>0.05) with no significant difference in the sexual ratio, can identified as P. indicus. Cockroaches of Tokunoshima-A group that produced a total of 221 female and no male offspring, despite having sperms in their spematheca, can be identified as P. surinamensis, while those of Tokunoshima-B group with all having sperms in their spermatheca produced a total of 242 male and 207 female offspring in an average ratio of 12.1 to10.4 (p>0.05) with no significant difference in the sexual ratio, can thus be identified as P. indicus.On the same note, female cockroaches of Okinawato-A group that produced a total of 724 female and no male offspring, despite having sperms in their spematheca, can be identified as P. surinamensis, while those of Okinawato-B group with all having sperms in their spermatheca produced a total of 322male and 312 female offspring in an average sexual ratio of 16.1 to 15.6 (p>0.05) with no significant difference in the sexual ratio, can be identified as P. indicus.Thus, both species of P. surinamensis and P. indicus were found to be distributedon the three islands of Iwoto, Tokunishima and Okinawa, with their habitat overlapping with each other.The group of five F1 female cockroaches from Hahajima, Chichijima, Nishijima and Nakodojima, produced a total of only 248, 59, 663 and 143 female offspring, respectively and no male offspring, despite having sperms in their spematheca. These cockroaches were identified as P. surinamensis. Thus, there is a possibility that only P. surinamensis and not P. indicus are distributed on these four islands.The group of five F1 female cockroaches from Amamiooshima, Miyakojima, Ishigakijima and Hawaii, produced a total of 260 male (M) and 260 female (F) offspring with an average ratio of M:F at 14.4:14.4 (p>0.05) per litter, 230M, 267F, av. 16.4:19.1 (p>0.05) per litter, 281M, 266F, av. 16.5:15.6 (p>0.05) per litter and 199M, 189F, av. 11.7:11.1 (p>0.05) per litter, respectively. Thisprobably indicates that only P. indicus and not P. surinamensis were inhabiting the four islands.From the above results, we can conclude that there are areas in Japan where the distribution of P. surinamensis and P.indicus overlap with each other, and there are also areas in which either only one or the other could be found.Futhermore, all the various specimen from our study were examined for morphologic differences between the 2 species. Roth (1967) stated that P. surinamensis could be morphologically distinguished from P. indicus based on the distance between the ocelli and compound eye, in which the former species show contact between the ocelli and the compound eye, while in the latter species, they are separated. However, in our experiments, we could not find any female adult cockroach of P. surinamensis, whose ocelli were in contact with the compound eye, that is, for the groups that do not produce any male offspring, the distance between ocelli and compound eye in the adult female from the various localities are as follows: Hahajima, 0.16 mm > Chichijima, 0.14 mm > Nakodojima, 0.13 mm > Nishijima, Tokunoshima-A & Okinawato-A, 0.12 mm > Iwoto-A, 0.10 mm, respectively, with an average distance of 0.13 mm. For the groups that produce both male and female offspring, identified as P. indicus, the distance between ocelli and compound eye in the adult female from the various localities are as follows: Hawaii, 0.21mm > Iwoto-B, 0.18 mm > Miyakojima, 0.16 mm > Amamiooshima & Okinawato-B, 0.13 mm > Tokunoshima-B & Ishigakijima, 0.12 mm, respectively, with an average distance of 0.15 mm.There was no significant difference in the distance between the ocelli and compound eye between the two species. Thus, this morphological criterion is not applicable for species identification.The length of tegmina has been used as a criterion for species identification in many insects. Thus, we proceed to measure the length of the tegmina of the adult female cockroaches in our study. For the groups that do not produce any male offspring, identified as P. surinamensis, the average tegmina length of the adult female from the various localities are as follows: Okinawato-A, 15.82 mm > Hahajima, 15.26 mm > Nishijima, 15.07 mm > Nakodojima, 14.16 mm > Chichijima, 13.81 mm > Tokunoshima-A, 13.57 mm > Iwoto-A, 12.87 mm, respectively. For the groups that produce both male and female offspring, identified as P. indicus, the average tegmina length of the adult female from the various localities are as follows: Okinawato-B, 14.72 mm > Hawaii, 14.64 mm > Iwoto-B, 14.35 mm > Ishigakijima, 13.81 mm > Tokunoshima-B, 13.54 mm> Amamiooshima, 13.53 mm > Miyakojima, 12.96 mm, respectively. It was observed that there was not much difference in the tegmina length among the specimens from different localities and also between the two species, thereby excluding the used of this criterion for species identification.Moreover, to differentiate the species without using the cross breeding experiment, we tried the method of solitary rearing of the unmated female adult cockroaches obtained from our previous experiments. Our results showed that all individuals identified as P. surinamensis produced offspring, and based on our previous sexual differentiation method of the nymph, all the offspring nymph were found to be female. On the contrary, individuals identified as P. indicus did not produce any offspring. From this observation, we can identify the species of the adult female cockroach collected from the wild by solitary rearing and examining the sex of the offspring produced. Thus, those female adult that produce only female offspring can be identified as P. surinamensis and that that produce both male and female offspring or those that did not produce any offspring can be identified as P. indicus.Based on the results of the above studies, the so-called “Ogasawara cockroaches” which has until now been thought to consist of only P. surinamensis, actually also comprises of P. indicus, which are also distributed in the same area. From our study, we have also added one more species of cockroach that inhabit Japan, that is to 58 species. Until recently, P. indicus and P. surinamensis were thought to be distributed in different areas but our study shows that there are areas in which both species co-habitat together and there are also areas in which either only one of the two species can be found. This finding has deep implication for future studies. In addition, we also found that the criterion of using the distance between the ocelli and the compound eye for species identification, as proposed by Roth (1967), is applicable nor reliable. We propose an alternative method in the form of solitary rearing of wild female adult and determining the sex of the offspring for species identification. Those that produce only female offspring be identified as P. surinamensis, while those that produce both male and female offspring, as well as that that failed to produce, should be regarded as P. indicus. Since the report by Asahina (1991) that species identification of “Ogasawara cockroaches”, needs further clarification, the results of our present study has provided the answer to his question through our morphological observation, cross breeding and solitary rearing experiments of those cockroaches.
• Persistent ID (NDL): info:ndljp/pid/9479428; https://dl.ndl.go.jp/pid/9479428
• Collection: 障害者向け資料
• Collection (Materials For Handicapped People:1): テキストデータ
• Collection (particular): 国立国会図書館デジタルコレクション > デジタル化資料 > 博士論文; https://dl.ndl.go.jp/collections/A00014
• Acquisition Basis: 博士論文（自動収集）
• Date Accepted (W3CDTF): 2015-08-01T14:40:15+09:00
• Date Created (W3CDTF): 2015-07-16
• Format (IMT): PDF; application/pdf
• Access Restrictions: 国立国会図書館内限定公開
• Service for the Digitized Contents Transmission Service: 図書館・個人送信対象外
• Availability of remote photoduplication service: 可
• Periodical Title (URI): http://id.nii.ac.jp/1112/00004234/
• Data Provider (Database): 国立国会図書館 : 国立国会図書館デジタルコレクション; https://dl.ndl.go.jp

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