It has been previously suggested that there is a conservative program for neural development amongst the arthropods, on the basis that a stereotyped set of cells involved in establishing the axon tracts in the CNS of insect embryos is also present in crayfish embryos. We have examined the spatiotemporal pattern of axon growth from a set of early differentiating central neurons in the embryo of two crustaceans, the woodlouse Porcellio scaber and the freshwater crayfish Cherax destructor, and drawn comparisons with insect neurons whose somata lie in corresponding positions within the CNS. While many of the woodlouse and crayfish neurons show a similar pattern of axon growth to their insect counterparts, the axon trajectories taken by others differ from those seen in insects. We conclude that this aspect of early neural development has not been rigidly conserved during the evolution of the crustaceans and insects. However, the extent of similarity between the insects and the crustaceans is consistent with the idea that these groups of arthropods share a common evolutionary ‘Bauplan’ for the construction of their nervous systems. While the pattern of early axon growth in the woodlouse and crayfish embryos is sufficiently similar that many neurons could be confidently recognised as homologues, several differences were noted in both the relative order of axon outgrowth and axon morphologies of individual neurons.

Ballard
J. W. O.
,
Olsen
G. J.
,
Faith
D. P.
,
Odgers
W. A.
,
Rowell
D. M.
,
Atkinson
P. W.
(
1992
)
Evidence from 12s ribosomal RNA sequences that onychophorans are modified arthropods.
Science
258
,
1345
1348
Dohle
W.
,
Scholtz
G.
(
1988
)
Clonal analysis of the crustacean segment: the discordance between genealogical and segmental borders.
Development
104
,
147
160
Goodman
C. S.
,
Bastiani
M. J.
,
Doe
C. Q.
,
duLac
S.
,
Helfand
S. L.
,
Kuwada
J. Y.
,
Thomas
J. B.
(
1984
)
Cell recognition during neuronal development.
Science
225
,
1271
1279
Harvey
J. J.
,
Raff
R. A.
(
1990
)
Evolutionary change in the process of dorsoventral axis determination in the direct developing sea urchin, Heliocidaris erythrogramma.
Dev. Biol
141
,
55
69
Jacobs
J. R.
,
Goodman
C. S.
(
1989
)
Embryonic development of axon pathways in the Drosophila CNS. 2. Behavior of pioneer growth cones.
J. Neurosci
9
,
2412
2422
Patel
N. H.
,
Poole
S. J.
,
Coleman
K. G.
,
Goodman
C. S.
,
Ellis
M. C.
,
Martinblanco
E.
,
Kornberg
T. B.
(
1989
)
Expression of engrailed proteins in arthropods, annelids, and chordates.
Cell
58
,
955
968
Raper
J. A.
,
Bastiani
M. J.
,
Goodman
C. S.
(
1983
)
Pathfinding by neuronal growth cones in grasshopper embryos: II selective fasciculation onto specific axonal pathways.
J. Neurosci
3
,
31
41
Sink
H.
,
Whitington
P. M.
(
1991
)
Location and connectivity of abdominal motoneurons in the embryo and larva of Drosophila melanogaster.
J. Neurobiol
22
,
298
311
Thomas
J. B.
,
Bastiani
M. J.
,
Bate
M.
,
Goodman
C. S.
(
1984
)
From grasshopper to Drosophila: a common plan for neuronal development.
Nature
310
,
203
207
Wray
G. A.
,
Raff
R. A.
(
1990
)
Novel origins of lineage founder cells in the direct developing sea urchin, Heliocidaris erthyrogramma.
Dev. Biol
141
,
41
54
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