The Neuroendocrine System in the Intestinal Tract and Pancreas of Antarctic Fish
249
actinopterygians, and the endocrine portion forms a large aggregation of
islet cells, the Brockmann body, with some smaller accessory islets [22].
Only one Brockmann body was observed in Cryodraco antarcticus,
Pagetopsis macropterus and Pleuragramma antarcticum but in
Notothenia coriiceps three islets of 1 cm diameter were found [24].
The enteropancreatic NES has been studied in three channichthyid
species: Chionodraco hamatus, Cryodraco antarcticus, Pagetopsis
macropterus and in four nototheniids: Notothenia coriiceps,
Pleuragramma antarcticum, Trematomus bernacchii, Trematomus
newnesi [23-26]. The data concerning the enteropancreatic NES of nonAntarctic teleosts are also reported for comparison.
Intestinal Endocrine Cells
Numerous immunoreactive (IR) endocrine cells were seen in the intestinal
epithelium of C. hamatus, C. antarcticus, P. macropterus, N coriiceps, P.
antarcticum, T. bernacchii and T. newnesi; their immunopositivity to the
different antisera slightly varied according to the species [23-26].
Gut endocrine cells are always of the open type (Fig. 1). Generally at
the base of the cell there is a more intense immunostaining, which
corresponds to a greater concentration of the immunodetected substance.
Most showed some basal cytoplasmic extensions that make contact with
neighboring cells (Fig. 2). Endocrine cells positive to serotonin, substance
P (sub P), cholecystokinin octapeptide (CCK 8), cholecystokinin
decapeptide (CCK 10), glucagon, gastrin, pancreatic polypeptide (PP),
VIP and PHI antisera were observed in all species. Sub P-, CCK 8- and
serotonin-IR cells were equally frequent along the gut, while gastrin-,
glucagon-, VIP-, PACAP- and PHI-IR cells seemed to be more numerous,
sometimes exclusive, in the proximal intestinal portion.
In the intestinal epithelium of T. bernacchi and T. newnesi we also
found big-gastrin- and bombesin-IR cells. Fewer somatostatin-, serotonin-,
gastrinlCCK-IR cells were seen, and, on the contrary, more numerous
VIP- and PP-IR cells were present.
Somatostatin-IR cells could be found in both channichthyid species, but
were particularly abundant in C. antarcticus; on the contrary, serotonin-IR
cells appeared more frequent in C. hamatus. In C. antarcticus numerous
insulin immunoreactive endocrine cells were found along the entire gut
(Fig. 3). This endocrine cell type was instead rarely, if ever, seen in the
nonAntarctic perciformes Serranus cabrilla (Serranidae) and Diplodus
annularis (Sparidae) [25,26). The pattern of distribution of peptides in
these temperate water teleosts is more similar to that of nototheniids than
that of channichthyids.
249
actinopterygians, and the endocrine portion forms a large aggregation of
islet cells, the Brockmann body, with some smaller accessory islets [22].
Only one Brockmann body was observed in Cryodraco antarcticus,
Pagetopsis macropterus and Pleuragramma antarcticum but in
Notothenia coriiceps three islets of 1 cm diameter were found [24].
The enteropancreatic NES has been studied in three channichthyid
species: Chionodraco hamatus, Cryodraco antarcticus, Pagetopsis
macropterus and in four nototheniids: Notothenia coriiceps,
Pleuragramma antarcticum, Trematomus bernacchii, Trematomus
newnesi [23-26]. The data concerning the enteropancreatic NES of nonAntarctic teleosts are also reported for comparison.
Intestinal Endocrine Cells
Numerous immunoreactive (IR) endocrine cells were seen in the intestinal
epithelium of C. hamatus, C. antarcticus, P. macropterus, N coriiceps, P.
antarcticum, T. bernacchii and T. newnesi; their immunopositivity to the
different antisera slightly varied according to the species [23-26].
Gut endocrine cells are always of the open type (Fig. 1). Generally at
the base of the cell there is a more intense immunostaining, which
corresponds to a greater concentration of the immunodetected substance.
Most showed some basal cytoplasmic extensions that make contact with
neighboring cells (Fig. 2). Endocrine cells positive to serotonin, substance
P (sub P), cholecystokinin octapeptide (CCK 8), cholecystokinin
decapeptide (CCK 10), glucagon, gastrin, pancreatic polypeptide (PP),
VIP and PHI antisera were observed in all species. Sub P-, CCK 8- and
serotonin-IR cells were equally frequent along the gut, while gastrin-,
glucagon-, VIP-, PACAP- and PHI-IR cells seemed to be more numerous,
sometimes exclusive, in the proximal intestinal portion.
In the intestinal epithelium of T. bernacchi and T. newnesi we also
found big-gastrin- and bombesin-IR cells. Fewer somatostatin-, serotonin-,
gastrinlCCK-IR cells were seen, and, on the contrary, more numerous
VIP- and PP-IR cells were present.
Somatostatin-IR cells could be found in both channichthyid species, but
were particularly abundant in C. antarcticus; on the contrary, serotonin-IR
cells appeared more frequent in C. hamatus. In C. antarcticus numerous
insulin immunoreactive endocrine cells were found along the entire gut
(Fig. 3). This endocrine cell type was instead rarely, if ever, seen in the
nonAntarctic perciformes Serranus cabrilla (Serranidae) and Diplodus
annularis (Sparidae) [25,26). The pattern of distribution of peptides in
these temperate water teleosts is more similar to that of nototheniids than
that of channichthyids.