several hours and is controlled by about 100 neuroendocrine cells in the cerebral ganglion (caudodorsal cells). These cells secrete various peptides
which probably arise from more than one large
precursor. The best-known of these peptides is
the ovulation hormone CDCH (Fig. 8.6c), which
agrees in 16 of its 36 amino acids with the ELH of
Aplysia. Taking into account the fact that the prosobranchs and the pulmonates separated about
400 million years ago, these peptides appear to
be very highly conserved [57].
8.8.2 Peptide Hormones of Arthropods
Although many studies have been carried out of
the regulatory peptides of insects and crustaceans
[20], the other arthropod groups have been rather
neglected. Of the insect neuropeptides, the bestknown are those of the silkworm Bombyx mori.
Four types are found, in some cases with several
variants: the prothoracicotropic hormone
(PITH), the diapause hormone, the hatching
(eclosion) hormone (EH) , and the melanizing
and
red-pigment
concentrating hormone
(MRCH). The enormous number of individuals
needed for the isolation of these peptides is most
easily attained with the silkworm; Japanese
research groups made use of 10 million male
insects for this purpose. The prothoracicotropic
hormone is produced from a pair of neurosecretory cells in the brain and stimulates ecdysterone
release from the prothorax glands. PITH has
109 amino acids and arises from a precursor of
224 amino acids [97]. In addition to the speciesspecific PTTH, the Bombyx brain contains several peptides of about 5 kDa, the bombyxins,
which in fact affect ecdysone release from the
prothorax glands of Samia cynthia and were,
therefore, earlier known as 4K-PITHs; their
function in Bombyx mori is, however, not yet
clear. They belong to the insulin family and have
the typical dime ric structure with A and B chains
linked by a disulphide bridge. They are encoded
by a gene family with many members which can
be subdivided into three classes, A-C. The probombyxins have the same domain organization,
B-C-A, as the pro-insulins [89]. An insulinrelated peptide (LIRP) of unknown function
from Locusta migratoria has been sequenced via
the cDNA; LIRP shows no greater sequence
similarity to the bombyxins than to the insulins
[113]. Insects contain further peptides with glandotropic hormone effects, for example, allatotropin, a 13-residue peptide from Manduca sexta
8.8.2 Peptide Hormones of Arthropods
307
which stimulates the secretion of the juvenile hormone from the corpora allata; allostatins (8-13
amino acids), isolated from the cockroach
Diploptera punctat, have an antagonistic effect
[96, 237]. The production of sexual attractants by
the females of the lepidopterans Bombyx mori
and Heliothis zea is stimulated by the 33-aminoacid pheromone-biosynthesis-activating neuropeptides (PBANs) [102, 176].
The eclosion hormone synthesized in the neurosecretory brain cells of the silkworm controls
the hatching of the adult animal from the pupal
case; the earlier moultings are also regulated by
EH produced in abdominal tissues. In addition
to the full-length form of 62 amino acids
(Fig. 8.6d), Bombyx EH is also found in N- and
C-terminal shortened forms. Manduca EH differs
at 12 positions from that of Bombyx [82, 106].
The paragonial peptide from males of Drosophila
funebris (Fig. 8.6f) influences the courting behaviour of the female and is, therefore, effectively a
pheromone. At least three variants of the melanizing and red-pigment concentrating hormone
are found in Bombyx mori but, as yet, only the Nterminal sequences are known. These show only
small differences to each other but, as in the case
of PTTH, have some similarity to insulin and
IGF-II [135].
Proctolin is a pentapeptide which was known
already in 1967 to initiate contractions in the musculature of the posterior gut (proctodaeum) of
the cockroach Periplaneta americana (hence the
name); it was first characterized structurally in
1975 using material extracted from 125000 individuals (Fig. 8.6 e). Proctolin is found in most, but
by no means all, insects; for example, it is apparently absent from Manduca sexta. It has also been
found in crustaceans, the xiphosuran Limulus
polyphemus, the leech Hirudo medicinalis, and
even in the hypothalmus of the rat [162]. Many
other insect myotropic peptides have been found
and sequenced in recent years. The pyrokinins,
which stimulate contractions of the posterior gut
and the oviduct, are characterized by the Cterminal sequence - FXPRL-amide. Several such
peptides are known from the cockroach Leucophaea maderae and from Locusta migratoria
[149, 163, 195]. Locusta also contains peptides,
the locustatachykinins, which have some similarity to the vertebrate tachykinins and affect the gut
musculature [194]. A myotropic peptide with
similarity to the vertebrate gastrin has been isolated from the cockroach Leucophaea maderae
(Fig. 8.6 k). The cardioactive peptide known from
the brachyuran Carcinus maenas (CCAP, carcinus
which probably arise from more than one large
precursor. The best-known of these peptides is
the ovulation hormone CDCH (Fig. 8.6c), which
agrees in 16 of its 36 amino acids with the ELH of
Aplysia. Taking into account the fact that the prosobranchs and the pulmonates separated about
400 million years ago, these peptides appear to
be very highly conserved [57].
8.8.2 Peptide Hormones of Arthropods
Although many studies have been carried out of
the regulatory peptides of insects and crustaceans
[20], the other arthropod groups have been rather
neglected. Of the insect neuropeptides, the bestknown are those of the silkworm Bombyx mori.
Four types are found, in some cases with several
variants: the prothoracicotropic hormone
(PITH), the diapause hormone, the hatching
(eclosion) hormone (EH) , and the melanizing
and
red-pigment
concentrating hormone
(MRCH). The enormous number of individuals
needed for the isolation of these peptides is most
easily attained with the silkworm; Japanese
research groups made use of 10 million male
insects for this purpose. The prothoracicotropic
hormone is produced from a pair of neurosecretory cells in the brain and stimulates ecdysterone
release from the prothorax glands. PITH has
109 amino acids and arises from a precursor of
224 amino acids [97]. In addition to the speciesspecific PTTH, the Bombyx brain contains several peptides of about 5 kDa, the bombyxins,
which in fact affect ecdysone release from the
prothorax glands of Samia cynthia and were,
therefore, earlier known as 4K-PITHs; their
function in Bombyx mori is, however, not yet
clear. They belong to the insulin family and have
the typical dime ric structure with A and B chains
linked by a disulphide bridge. They are encoded
by a gene family with many members which can
be subdivided into three classes, A-C. The probombyxins have the same domain organization,
B-C-A, as the pro-insulins [89]. An insulinrelated peptide (LIRP) of unknown function
from Locusta migratoria has been sequenced via
the cDNA; LIRP shows no greater sequence
similarity to the bombyxins than to the insulins
[113]. Insects contain further peptides with glandotropic hormone effects, for example, allatotropin, a 13-residue peptide from Manduca sexta
8.8.2 Peptide Hormones of Arthropods
307
which stimulates the secretion of the juvenile hormone from the corpora allata; allostatins (8-13
amino acids), isolated from the cockroach
Diploptera punctat, have an antagonistic effect
[96, 237]. The production of sexual attractants by
the females of the lepidopterans Bombyx mori
and Heliothis zea is stimulated by the 33-aminoacid pheromone-biosynthesis-activating neuropeptides (PBANs) [102, 176].
The eclosion hormone synthesized in the neurosecretory brain cells of the silkworm controls
the hatching of the adult animal from the pupal
case; the earlier moultings are also regulated by
EH produced in abdominal tissues. In addition
to the full-length form of 62 amino acids
(Fig. 8.6d), Bombyx EH is also found in N- and
C-terminal shortened forms. Manduca EH differs
at 12 positions from that of Bombyx [82, 106].
The paragonial peptide from males of Drosophila
funebris (Fig. 8.6f) influences the courting behaviour of the female and is, therefore, effectively a
pheromone. At least three variants of the melanizing and red-pigment concentrating hormone
are found in Bombyx mori but, as yet, only the Nterminal sequences are known. These show only
small differences to each other but, as in the case
of PTTH, have some similarity to insulin and
IGF-II [135].
Proctolin is a pentapeptide which was known
already in 1967 to initiate contractions in the musculature of the posterior gut (proctodaeum) of
the cockroach Periplaneta americana (hence the
name); it was first characterized structurally in
1975 using material extracted from 125000 individuals (Fig. 8.6 e). Proctolin is found in most, but
by no means all, insects; for example, it is apparently absent from Manduca sexta. It has also been
found in crustaceans, the xiphosuran Limulus
polyphemus, the leech Hirudo medicinalis, and
even in the hypothalmus of the rat [162]. Many
other insect myotropic peptides have been found
and sequenced in recent years. The pyrokinins,
which stimulate contractions of the posterior gut
and the oviduct, are characterized by the Cterminal sequence - FXPRL-amide. Several such
peptides are known from the cockroach Leucophaea maderae and from Locusta migratoria
[149, 163, 195]. Locusta also contains peptides,
the locustatachykinins, which have some similarity to the vertebrate tachykinins and affect the gut
musculature [194]. A myotropic peptide with
similarity to the vertebrate gastrin has been isolated from the cockroach Leucophaea maderae
(Fig. 8.6 k). The cardioactive peptide known from
the brachyuran Carcinus maenas (CCAP, carcinus