EMBRYONIC DEVELOPMENT OF THE NERVOUS SYSTEM OF THE STONEFLY，
KAMIMUR工A T工BIAL工S (PICTET) (PLECOPTERA: PERL工DAE)

Tohru Kishimoto，University of Tsukuba，

工nstitute of Bio1ogica1 Sciences

Sakura‑mura，Ibaraki，
305 Japan

The embryonic deve10pm世 nt of the ventra1 n暗 rve cord and brain of thestonef1y， 主主恩語旦且2 弘弘主よ主2 was observed， and the number of neurob1asts ineach gang1ion of the mandibu1ar to the 10th abdomina1 segments was count日 d.
The ventra1 nerve cord of K. tibia1is deve10ps in the same way as inernbryo自 of other insects，and the neurob1asts differentiate in 3 gnatha1，3
thoracic and 1
1 昌 bdomina1 segments，but those in the 1
1th abdomina1 segment
anddo not form，as in other abdomina1 segments，a pair of

品1 ganglia.
abdomin工n the 1ater deve1opment，the 7th to 10th abdomina1 守an‑

呈re tr 註 ns~en 七

glia fuse，and the met昌 thoracic and 1st abdomin品 1 gang1ia do so a1so. The
median cord of ventra1 nerve cord is derived from the median invagination of
the ventra1 ectoderm as observed in embryos of other insects，but the fate ofit cou1d not be traced. The neuri1emma seems to arise from the periph日 ra1
gang1ion ce11s. 工n the ear1y embryogenesis of Loc足立五~nigratori~ (Bate，1976)
and 忠弘よ us bimacu 工 atu~ (Miyamoto and Shimozawa， ヲ 83; Miyamoto， 1983)， thean1ag告 of the nervous syste滋 shows the segmenta1 homo1ogy，not on1y within th芭
gnatha1 and thoracic gang1i丑， but a1so between the thor丑 cic and abdominal
ones.In .
lS.
. 主主主主よ詰， the segmental homo1ogy within each thoracic gang1ion wasdemonstrated in the ear1y embryogenesis by the result of ce11 counting，but it
shou1d be stressed out that the neurob1ast number in the mandibu1ar gang1ia issma11er than that of the maxi1lary and 1abia1 gang1ia. This difference of theneurob1ast number in gnatha1 gang1ia may be re1ated to the differences of
their structure，that iSt the mandibu1ar segment bears a p呂 ir of simp1e appenωdages，whi1e the maxi11ary and labia1 segments bear complic丑七 edapp告 nd品守 es15

1るwith palp巴 s.
工n the 昌 bdominal segments，no appendages are formed except the pleuro‑

podi品 in the 1百七 abdominal s邑 gment，so that th色 signif工cant differences instructure within abdominal segments do not occur. However，the neuroblast
number in the 10th abdominal segment was extremely 耳mall， 担 nd it was likely
七hat this seg賠 色 nt shows i七s own functional speci品
工 ization or difference.

. tib且よis th申 segmental specialization of ganglia of the madibularThus，inE
and 10th abdominal segm日nts occurs in the 日arly neurogenesis.
工nE.
.主主主主主主主， the pro七ocerebruぉ consists of 4 pairs of lobes， that isof the 1st to 4th protoc巴 rebral lobes. It is generally conceded that n巴 uroω
blasts do not take part in the formation of optic lobes in insects，but the
1st protocerebr丘 1 lobes of this species 呂 古 車 compos申 d‑̲of larg控 neuroblast‑lik巴cells.

工t is thought that these large neuroblast‑like cells of the 1st protoゅι

cerebral or optic lobes in 旦
. ム主主主よよ三 correspond to usual neuroblasts infollowing pointsi they are as large as the neuroblasts of other lobes，and 丑主 e
stained lightly with haematoxylin.

Therefore，it m呂 Y b色 postulated that theneuroblasts take part in the formation of th巴 optic lobes in五・L辿比よム三‑The 4th protocerebral lobes ar日 observed 昌 s in C三五主主主主主主役ゑ主主主主主 and主主主 i‑.
!
2l:.
主主
ゑ
主a am告 ricana (羽 alz昌 cher， 1968; Rohrschneider， 1雪68; SCholl， 1ヲ6雪)， but
the present author could not decide whether they were the paired gangl工a ofthe pr日antennal segment.
In general， in insec七s no commissure is formed be七百 een the lobes of thedeutocerebrum，but in ~.斗亙語弘~ the deutocerebral commissure taking part in
the formation of the supraoesophageal commissure or pars intercerebralis，exists. The neuroblasts of the tritocerebrum inE. 主主主主ゑ主主立丑 ppe呂 r in theintercalary segment and anterolateral region of the stomodaeum，on the oth日 r
hand，those of many other insects appear only in the int巴 rcalary segm日 nt.

References
Bate，C. M. (1976) J. Embryol. exp. Morphol.，35:107‑123.
Malzacher，P. (1ヲ68) Z. Morphol. Tiere，62:103‑161.
Miyamoto，T. (1983) Zool. Magazine，92:332‑341.
Miyamoto，T. and T. Shimozawa (1983) ZooLMagazine，92:317‑331.
Rohrschneid
邑 r，1. (1号68) Zool. Jab. An
丑t.，85:537‑578.

，
巴 65:1 142.
Scholl，G. (1969) Z. Morphol. Tierpr
口c.Arthropod.Embry
口l.Soc..Jpn.，
1985