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Copidosoma floridanum is a species of wasp in the family Encyrtidae which is primarily a parasitoid of moths in the subfamily Plusiinae. It has the largest recorded brood of any parasitoidal insect, at 3,055 individuals.[2] The life cycle begins when a female oviposits into the eggs of a suitable host species, laying one or two eggs per host. Each egg divides repeatedly and develops into a brood of multiple individuals, a phenomenon called polyembryony. The larvae grow inside their host, breaking free at the end of the host's own larval stage.[2]
A cosmopolitan species, Copidosoma floridanum is distributed worldwide. Because of its significance to agriculture as pest control and its phylogenic relationship with other important species, the wasp's genome is being sequenced by the Human Genome Sequencing Center as part of the i5K project,[3] which aims to sequence the genomes of 5,000 arthropods.[4]
As a putatively eusocial species, C. floridanum embodies only two of the four behavioral characteristics that characterize genuine eusociality: larvae live in groups, and there is reproductive division of labor, or reproductive altruism.[5] The second characteristic, reproductive altruism, is, in these wasps, manifested as a sterile soldier caste that has the sole purpose of protecting their reproductive clonal siblings throughout their larval stage. Reproductive altruism behavior plays a major role in the survival and reproductive success of C. floridanum. This species displays haplodiploid sex determination, which increases relatedness among females from 0.5 to 0.75 because males develop from unfertilized eggs and are therefore haploid while females develop from normally fertilized eggs and are therefore diploid. So, as a result of eusocial progeny allocation and a distinctive type of clonal development in parasitized hosts, polyembryonic wasps including C. floridanum are able to thrive.[6][7][8] Additionally, these wasps modify their caste ratios in response to interspecific competition, creating a trade-off between reproduction and defense, as the wasps adapt to the levels of competition within the group.[6]
C. floridanum produce eggs that divide clonally to produce larger broods. The polyembryonic wasp caste system consists of two separate groups: some of the embryos in a clone mature into reproductive larvae that ultimately develop into adults, while the other group consists of sterile soldier larvae that protect siblings from competitors.[9] At this ecological level, the soldiers’ reproductive altruism is tied to clone-level allocation to defense; thus, in order to maximize the reproductive success of the siblings, soldiers risk their own chances of reproductive success (with no conflict between the soldiers themselves) [9] In his study, Giron argues that soldier aggression in this wasp species is inversely related to competitors’ genetic relatedness, without respect to levels of resource competition.[9] In a later study, Giron sought to differentiate between the aggression of female and male soldiers, finding that the latter group is non-aggressive toward all competitors.[9]
Polyembryonic wasps, including C. floridanum, exhibit spite through instances of precocious larval development.[10] Spite provides an explanation for how natural selection can favor harmful behaviors that are costly to both the actor and the recipient; spite is typically considered a form of altruism that benefits a secondary recipient.[11] Two criteria demonstrate that spite is truly occurring: (i) the behavior is truly costly to the actor and does not provide a long-term direct benefit; and (ii) harming behaviors are directed toward relatively unrelated individuals.[11]
In C. floridanum, the process takes place in the following manner: the host insect lays two eggs in the eggs of moths, usually one male and one female, which proceed to divide asexually to produce a brood of clonal brothers and clonal sisters.[7] The wasp larvae then mature within the moth caterpillar, utilizing the moth as food throughout growth. Competition for resources limits how many adult wasps can emerge from the host; this indicates that negative relatedness likely exists within the brood. A portion of the larvae do not emerge, who serve as adults who forgo future reproduction in order to kill relatively unrelated opposite-sex siblings maturing in the same host before dying themselves; this special group of adult killers developed precociously.[12] Asymmetrical dispersal (defined as the sex differences in the scale of competition) and asymmetrical relatedness (brothers tend to be more related to sisters than the reverse) most likely serve as the evolutionary resolution of this conflict, in favor of the sisters.[12] This process, most importantly, frees up resources for closer relatives.
C. floridanum gain interspecific competitive advantage over other competitors, including Glyptapanteles pallipes and Microplitis demolitor, primarily due to the presence of their soldier caste, whose fitness is limited to the survival of their clonal siblings. Uka studied the interspecific competition between C. floridanum male broods and G. pallipes in order to elucidate the defensive strategies of the former group. The C. floridanum progeny survival rate was greater than that of G. pallipes, regardless of the interval of oviposition.[13] C. floridanum gains a competitive advantage through its ability to physiologically suppress or putatively attack its adversaries. First off, they secrete a physiologically suppressive factor from in their labial glands as embryos or even in the tissue of the host and steadily supplied to the hemolymph. This toxic factor causes damage to G. pallipes larvae and ultimately leads to death. More specifically, C. floridanum induces a delay in competitor maturation, along with generating paralysis and weakness (Uki). Physical attack, on the other hand, has not been proven to be effective as a means of killing competitors.[14]
The morula-stage embryo of C. floridanum invades the embryo of the host, utilizing adherent junctions to host cells. This is an effective evolutionary strategy, as other approaches could leave obvious wounds on the host cells, alerting competitors to the presence of this wasp species. As a result, these embryos can invade a phylogenetically distant host embryo (the moth) by taking advantage of the compatibility of its cells with host tissues.[15]
During larval development, an extraembryonic membrane surrounds each organism during maturation with the caterpillar host. A series of experiments performed by Giron and Strand proved that this membrane serves as the cue for kin selection; they demonstrated that attack rates were less common with kinship when the membrane was present. When the membrane was removed, attack rates between kin increased.[8] This study additionally demonstrated how the membrane functions as a cue for kin discrimination by switching the membranes between larvae. Researchers found that the soldiers were fooled into not killing relatively unrelated larvae that were encased by an transplanted membrane.
Recently, studies have been conducted to identify differentially expressed genes in C. floridanum castes that code for identifiable ions and proteins that the sterile soldiers, for instance, share. Soldiers and reproductive larvae express enzymes with the differential usage of proteinase inhibitors and ribosomal proteins.[16] More specifically, odorant binding proteins (OBPs) are utilized for kin recognition, along with the likely usage of toxin-like and SP genes in the ability of soldiers to murder competitors or as immune defense against potential pathogens.[16] The host's molting cycle plays a significant role in determining the identity of precocious and reproductive larvae. More specifically, the C. floridanum young mature in synchrony with specific phases within the moth’s molting cycle. In the early stages of embryonic development, changes within the host’s developmental program intrinsically influence caste determination.[17]
Copidosoma floridanum is a species of wasp in the family Encyrtidae which is primarily a parasitoid of moths in the subfamily Plusiinae. It has the largest recorded brood of any parasitoidal insect, at 3,055 individuals. The life cycle begins when a female oviposits into the eggs of a suitable host species, laying one or two eggs per host. Each egg divides repeatedly and develops into a brood of multiple individuals, a phenomenon called polyembryony. The larvae grow inside their host, breaking free at the end of the host's own larval stage.
A cosmopolitan species, Copidosoma floridanum is distributed worldwide. Because of its significance to agriculture as pest control and its phylogenic relationship with other important species, the wasp's genome is being sequenced by the Human Genome Sequencing Center as part of the i5K project, which aims to sequence the genomes of 5,000 arthropods.
Copidosoma floridanum is een vliesvleugelig insect uit de familie Encyrtidae. De wetenschappelijke naam is voor het eerst geldig gepubliceerd in 1900 door Ashmead.
Bronnen, noten en/of referenties
キンウワバトビコバチ (Copidosoma floridanum) は、体長1mmほどの小さな寄生蜂の一種である。ハチ目（膜翅目）・コバチ上科・トビコバチ科に属する。
寄主であるキンウワバ亜科の卵に寄生し、寄主幼虫体内で発生を進めるkoinobiontの卵幼虫寄生蜂である。寄主としては、イラクサギンウワバ (Trichoplusia ni) 、ミツモンキンウワバ (Ctenoplusia agnata)、ガンマキンウワバ (Autographa gamma) などのヤガ科に属する中型のガが知られている。これらは、ニンジン、ダイズ、ゴボウ、シソなどの害虫であり、局地的に大発生して大被害をもたらす。
1つの卵からは、1,000から2,000の個体（胚）が生じる。これは現在知られている多胚性昆虫でも極端に多い例である。このため、多胚生殖のモデル生物として発生生物学と進化の研究に用いられている。
多くの膜翅目昆虫と同じく半倍数性の性決定を行い、受精卵からはメスのみが、未受精卵からはオスのみが発生する。それぞれの卵からは、多胚形成によって1個あたり2000の幼虫が生じる。また、同一寄主に対して受精卵と未受精卵を同時に産卵することが多く、この際には同じ寄主内に雌雄が混在することになる。この場合には必ずメスによるオス殺しが行われ、雌雄比は圧倒的にメスに偏る。
寄生蜂でありながら、カースト制を持つという非常に珍しい種であり、多くの研究報告がなされている。1つの卵から発生する個体は遺伝的に完全同一、つまりクローンだが、2種類の個体分化があり、前期に分化する個体は不妊の兵隊幼虫となり、後期に発生するものは生殖個体（女王）となる。これらはそれぞれ早熟型、生殖型と呼ばれる。以前は早熟幼虫と呼ばれることの多かった早熟型であるが、近年の研究で競合相手に対して排他的行動を示すことが明らかとなったため、最近はソルジャーと呼ばれることが多い。寄主であるキンウワバ幼虫は1から5齢があり、それぞれ2日程度ずつを経過する。キンウワバトビコバチのソルジャーは、寄主幼虫が1から4齢に、生殖型個体は5齢期に分化する。
分化前の生殖型個体の寄主体内における分布の仕方、およびソルジャーの生産数は雌雄で異なっている。オスの分化前個体は寄主の脂肪体に包まれた状態で存在しているが、メスは脂肪体に包まれることはなく自由に寄主体液内を浮遊している。多くの社会性の膜翅目昆虫ではソルジャーカーストはメス由来であるが、キンウワバトビコバチはオスもソルジャーを生産する。ソルジャーの生産パターンは、キンウワバトビコバチの系統や雌雄で差が見られ、研究が進んでいる。オスでは寄主が5齢時に少数のソルジャーを生産するだけであるが、メスでは寄主が卵の時期から常にソルジャーを生産しており、最大で100頭ほどを生産する。
寄生した寄主が競合相手となる異種寄生蜂に寄生された場合、ソルジャーの増員が行われる。この増員により競合相手を打ち負かすことができるが、これには生殖型の個体数の激減というコストを要する。ただし、これはメスの場合にのみ見られる現象であり、オスではソルジャーの増員も生殖型個体の減少も起こらない。メスのソルジャーが競合相手に対して排他的行動をとって噛み殺すのに対し、オスのソルジャーはそのような行動をとらない。この点から、オスにおけるソルジャーカーストの意義や社会生物学的な研究題材として大きな注目を集めている。
ソルジャーには少なくとも2種類の型（多型）が存在することが分かっている。1つめは寄主が卵の時期に現れる小型のソルジャーであり、2つめは寄主が幼虫期に現れる大型のソルジャーである。小型ソルジャーは血縁度の遠い同種他個体に対する攻撃を専門とし、大型ソルジャーは異種寄生蜂に対する攻撃を専門としている。このため、雌雄が混在した場合には、小型ソルジャーの存在しないオスがほぼ一方的に排除される。オスは完全に駆逐されることを逃れるため、寄主の脂肪体内に隠れて生息するという手段を進化させたと考えられている。
オスのソルジャーには異種寄生蜂に対する攻撃能が備わっていない。その代わり、オスは寄主体液中に毒物質を充満させており、これを用いて競合相手を排除している。この毒物質は致死性が高く、これに曝された競合相手は短期間のうちに死亡する。メスがオス同様に毒物質を使用しているかは解明されていないが、メスでは競合相手が存在した場合にソルジャーを増員し、これらが攻撃的に競合相手を噛み殺していく。
この項目は、動物に関連した書きかけの項目です。この項目を加筆・訂正などしてくださる協力者を求めています（Portal:生き物と自然／プロジェクト:生物）。 キンウワバトビコバチ (Copidosoma floridanum) は、体長1mmほどの小さな寄生蜂の一種である。ハチ目（膜翅目）・コバチ上科・トビコバチ科に属する。
寄主であるキンウワバ亜科の卵に寄生し、寄主幼虫体内で発生を進めるkoinobiontの卵幼虫寄生蜂である。寄主としては、イラクサギンウワバ (Trichoplusia ni) 、ミツモンキンウワバ (Ctenoplusia agnata)、ガンマキンウワバ (Autographa gamma) などのヤガ科に属する中型のガが知られている。これらは、ニンジン、ダイズ、ゴボウ、シソなどの害虫であり、局地的に大発生して大被害をもたらす。
1つの卵からは、1,000から2,000の個体（胚）が生じる。これは現在知られている多胚性昆虫でも極端に多い例である。このため、多胚生殖のモデル生物として発生生物学と進化の研究に用いられている。
