THE BEHAMOUR AND PRYSIOLOQY OF HERRING AND OTHER CLUPEIDS 293
vertebral column and position of the fins in herring at this stage. There
was a forward movement of the dorsal fin and anus and a backward
movement of the pelvic fins.
The speed of metamorphosis at sea, is unknown but Blaxtor and
Hempel (1961) found it lasted about 10 days at 15°C in German coastal
herring reared in tanks.
The heart, which prior to metamorphosis is composed of an outer
myocardium with an endothelial lining, seems to be the source of
erythrocyte formation (John, 1932). The endothelium thickens and
megaloblasts bud off into the lumen of the atrium and ventricle, where
they pass through an erythroblast stage to become erythrocytes. The
spleen, which is the site of formation of erythrocytes in the adult, is not
present at this stage.
2 0 1 .
I
,
I
,
I
,
I
,
l
,
l
l
10
14
I8
22
26
30
34
Standard length, G, a t metamorphosis (mm)
FIQ. 6. Relationehip between standard length at metamorphose (G) and temperature
(Re-drawn with permiasion from
hietory of larval clupeids in month-degrees.
Harder, 1960.)
Buchmann (1940) observed a large increase of thyroid activity a t
metamorphosis, the cell heights in the follicles increasing and colloid
being formed and released. There was also a change in the proadenohypophysis which he believed was due to the production of
thyrotropic hormone. According to Holliday ( 1960a), however, the
application of a histochemical (P.A.S.) technique indicated that the
site of thyrotropin production was the meso-adenohypophysis, and
Buchmann may have been reporting the production of a growth
hormone.
The formation of the gonads seems to take place at about this stage,
at least in Sardina pilchardus where dos Santos Pinto and Andreu
(1956) established the formation of the gonad at a length of 37 mm and
sexual differentiation at 45 mm.
vertebral column and position of the fins in herring at this stage. There
was a forward movement of the dorsal fin and anus and a backward
movement of the pelvic fins.
The speed of metamorphosis at sea, is unknown but Blaxtor and
Hempel (1961) found it lasted about 10 days at 15°C in German coastal
herring reared in tanks.
The heart, which prior to metamorphosis is composed of an outer
myocardium with an endothelial lining, seems to be the source of
erythrocyte formation (John, 1932). The endothelium thickens and
megaloblasts bud off into the lumen of the atrium and ventricle, where
they pass through an erythroblast stage to become erythrocytes. The
spleen, which is the site of formation of erythrocytes in the adult, is not
present at this stage.
2 0 1 .
I
,
I
,
I
,
I
,
l
,
l
l
10
14
I8
22
26
30
34
Standard length, G, a t metamorphosis (mm)
FIQ. 6. Relationehip between standard length at metamorphose (G) and temperature
(Re-drawn with permiasion from
hietory of larval clupeids in month-degrees.
Harder, 1960.)
Buchmann (1940) observed a large increase of thyroid activity a t
metamorphosis, the cell heights in the follicles increasing and colloid
being formed and released. There was also a change in the proadenohypophysis which he believed was due to the production of
thyrotropic hormone. According to Holliday ( 1960a), however, the
application of a histochemical (P.A.S.) technique indicated that the
site of thyrotropin production was the meso-adenohypophysis, and
Buchmann may have been reporting the production of a growth
hormone.
The formation of the gonads seems to take place at about this stage,
at least in Sardina pilchardus where dos Santos Pinto and Andreu
(1956) established the formation of the gonad at a length of 37 mm and
sexual differentiation at 45 mm.