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Observations on the pilot whale Globicephala melaenaOrganweight and growth.

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Observations on the Pilot Whale Globicephala
rnelarena: Organ Weight and Growth'
DANIEL F . COWAN2
Department of Pathohgy, Pathological Institute, McGiZl University,
Montreal, Canada
The organ weights of 55 Pilot whales (GZobicephaZu m e l a e n a ) of
known age, sex and length were determined by direct measurement. These weights
were compared with body length and statistical analysis demonstrated a high degree
of correlation between non-endocrine organ weight and body length, and by extension
0.1).
with body weight. Non-endocrine organs are not significantly related ( p
Graphs demonstrated the essentially parabolic nature of the weight and growth
curves.
Statements regarding organ weights in this, and presumably i n related species
are meaningless unless taken in conjunction with either body length or weight.
ABSTRACT
>
The North Atlantic Pilot whale Globicephala melaena (Traill) has been the
object of seasonal hunting in Newfoundland and the Faeroe Islands for many
years. Although thousands of individuals
had been taken, the basic biology of the
species had not been studied extensively
until the work of Sergeant ('62). In the
study reported here, which resulted from
a survey into the diseases of the Pilot
whale, an attempt is made to establish approximate normal vaIues for the weights
of various organs, and to demonstrate the
relation of the weights to age and body
size. The data were gathered in commercial whaling stations on the east coast
of Newfoundland.
MATERIALS AND METHODS
The Pilot or Pothead whale is a small
odontocete, measuring at the maximum
about 610cm (20 ft.1 in length for the
males and 511 cm (16.8 ft.) for females.
They are typically found in herds of from
10 to 250 individuals of both sexes and
of all ages. The range is in the North
Atlantic from Newfoundland through the
Laborador Sea, around Iceland and the
Faeroe Islands to the northern Scottish
islands. Their diet is essentially limited
to the squid Illex illecebrosus, or, when
that is not available, the cod Gadus marhua (Sergeant, '62). They are hunted
for their flesh and fat which have various
values, the
hunting
ANAT. REC.,155: 623-628.
area being the deep bays of eastern Newfoundland.
Peculiarities of behavior of the whale
and of the geology of the bay floors on
the Newfoundland coast make it possible
to drive entire herds inshore where they
are EIIed by lancing O r drowning through
Panic, 01 both. The carcasses are then
hmled ashore onto flensing Slips where
they are stripped of meat and fat.
We examined 55
These mimals are taken from the Course of their
daily routine, and may be said to be representative of the species in that the only
selection practiced by the hunters was as
to which herd was most readily captured.
The determination of body length was by
direct measurement in the conventional
manner, from the tip of the snout to
the apex of the notch of the flukes in
a straight line, not following the curve of
the body. Organ weight was determined
by direct measurement on a certified
beam balance. Only freshly killed, nonautolyzed material was included. Large
organs, beyond the capacity of our 50 Ib.
balance were weighed piecemeal.
Determination of age
Determination of the age of individuals
was by the method of Nishiwaki and Yagi
1This study was supported in part by a grant from
the Arctic Institute of North America, Moiitreal and
in part by Medical Research Council of Cahada
Grant-in-aid MT 60.
ZPresent address: Penrose Research Laboratory,
Philadelphia zoological Garden, Philadelphia, Pa.
19104.
623
624
DANIEL F. COWAN
('53), first applied to Globicephala melaena by Sergeant ('59, ' 6 2 ) , which depends on the occurrence of concentric
annual growth layers in the dentine and
cement layers of the teeth. In brief, a
tooth is sectioned in the long axis through
the pulp cavity and the dentine layers
thus exposed are counted under magnification. In older animals in which the
pulp cavity has closed and the dentine
layers no longer reflect the true age, transverse sections through the root just below
the gum-line are taken and ground to
translucency. These are then examined
under magnification ( X 250) and the
cement layers counted. The layering of
cementoblasts and alternation of opaque
and translucent ground-substance present
an appearance similar to the annual rings
of trees.
For a complete discussion of the theoretical basis and technical details o f age
determination by dentine and cementum
layering, the reader is referred to the
papers of Nishiwaki and Yagi ('53) and
of Sergeant ('59, '62).
While teeth were taken for age determination from every animal examined,
we were obliged to delete from the series
some which were mixed, or suspected to
have been mixed up by boys on the flensing slips. However, enough data remained to construct the curves below
(fig. 1 ) which relate sex, age, and body
length, based on 44 animals, which compare quite well with that of Sergeant ('62,
p. 17) based on 400 animals.
It will be noted (fig. I ) , especially in
the organ weight graphs, that there is a
gap in the scatters of points at about the
475-525 cm length level. This is an =tifact o f selection. Our primary purpose
was to search for disease, and we deliberately turned most attention to the largest,
and therefore oldest members of either
sex on the assumption that these old animals would have accumulated more lesions. Five-hundred and eleven centimeters
represents about the extreme length for females. However, none that large were
found and the gap represents smaller and
generally younger males exclusively.
The smallest division on our 50 lb.
capacity balance was the ounce, which
was our limit of accuracy. Arithmetic
conversion to the metric system was performed and it is this combination of the
limits of accuracy and conversion, taken
with the low weights involved which produced the alignment artifact seen on the
adrenal, thyroid, and spleen graphs. This
artifact is felt to be of little consequence,
the true point scatter falling presumably
in a random pattern within the range of
TABLE 3
r
Organ
P
< 0.001
< 0.001
< 0.001
< 0.001
< 0.001
> 0.1
0.848
0.909
0.901
Heart
Liver
Kidney
Lung
Spleen
Thyroid
Adrenal
0.809
0.721
0.142
0.131
> 0.1
cm
Body length
6o01
0
0
500.
00
0
A
A
O0 0
o o o
0
6 o0o
+
400.
,
A
A
A
a.A
A
A
O2
0
d
n
3000
Age in years
200-
n
52
51
54
55
53
37
53
625
PILOT WHALE ORGAN WEIGHT AND GROWTH
error about the alignments within the outlines of the distribution.
RESULTS
0
35
Statistical analysis of the data reveals
a very high degree of correlation between
organ weight and body length, with the
exception of the endocrine organs. The
following table summarizes this relationship.
The nature of the relationship is expressed in the following graphs. In figures 2-6 round symbols denote males;
triangles, females. In figures 7-8 open
symbols denote one animal; solid, two
congruent points.
.'
40
-
.
.
.
LIVER
KG
b
30-
0
.*
.
.
0.
*.
25-
. . ...
**
.A
z
DISCUSSION
The degree of correlation between nonendocrine organ weight and body length
is not unexpected as the body proportions
.
9
I
8
I
I
100
200
300
400
HEART
....
. ..
Fig. 3
..
.
@.
...
....
Liver Weight (KG) - Body length.
*. *'.
7
KG
6
. .
5
KG
%-
3.
2.
0
..
6
.
A
Body length crn
I
200
I
300
I
1
400
Heart Weight (KG)
500
-
660
Body length.
I
1
.i
4
1.
Fig. 2
.*
10.
4
1
KIDNEYS
12.
600
500
0
I
100
Fig. 4
A
Body length
*:A*
I
I
I
cm
I
200
300
400
500
6C0
Kidneys Weight (KG) - Body length.
626
DANIEL F. COWAN
.
35.
0
30-
The nature of this weight-length relationship is not expressed as a regression
analysis, as our data is numerically insufficient in the lower end of the length
spectrum (calves and fetuses). However,
the general slope of the array of points in
the scatter graphs suggests strongly that
the regression is a parabolic curve.
Organ weight is compared to body
length rather than to body weight as body
weight could not be measured directly.
.
LUNGS
KG
.
25.
0
0 :
THYROID
150
1751
O
1
125
Body length
cm
0
A
i i n
0
GM
10
I
100
200
Fig. 5
Lungs Weight (KG) - Body length.
300
400
500
600
.
.
.
. .
.
e
0
I lo/
'5
50
I
*
1
I
I
I
100
200
300
400
0
0
0
Fig. 7
I
I
500
600
Body length cm
Thyroid Weight (GM)
- Body length.
4s
. ..
.. .
.-... ...
.:
01
0
0
.
1
0
. A
200
1
.A.
-
.
ADRENALS
9)
0
GM
1
Body
cm
*
length
I
100
Fig. 6
length.
200
300
400
600
500
Spleen Weight (GM x 100)
-
Body
do not seem to alter much as the individual enlarges. Male and female are of
the same proportions; the only external
way to distinguish sex in individuals o€
equal length is by examination of the genital slits.
100
l5OI
Body
0
length cm
I
100
Fig. 8
200
300
400
500
600
Adrenals Weight (GM) - Body length.
PILOT W H A L E ORGAN WEIGHT AND GROWTH
0
O @
0
%0°
0
0
0
0
0
0
0
Fig. 9
go
Body
length cm
o o
300
400
500
600
Testis Weight (KG) -Body length.
* o
200
o
However, Sergeant ('62) derives the forand presents
mula W = 0.000025 X LZMs5
arguments for its validity. In this expression weight ( W ) is related to length (L).
Using this formula he predicted with accuracy the measured weight of an individual of a closely related species ( G .
scammoni) from its length. In addition,
the actual weights of fats and meat produced by a n individual tally well with the
weights predicted by the formula. As a n
example of the orders of weight involved,
the calculated weight of a large male,
590 cm, would be about 2600 kg, and a
large female, 465 cm, would weigh about
1320 kg.
The scattergram relating testis weight
to body length (fig. 9 ) is in excellent
agreement with a similar graph prepared
by Sergeant ('62). The abrupt rise in the
distribution reflects, of course, rapid
growth at puberty.
Of all the organs included in this study,
only the lungs contained any pathological
alteration likely to affect the weight. The
changes found included edema, pneu-
627
monia, aspiration of water and debris,
parasitism and granulomata, all of which
would tend to increase the weight. Nearly
all the lungs examined were at least
edematous to a mild degree, and so to
exclude pathological specimens would be
to reduce the data to a level that would
not produce a usable curve. As a consequence, all lung weights were plotted.
Surprisingly, the points representing lungs
grossly and microscopically least affected
by disease are not the lowest ones; they
are buried in the scatter along the appropriate length lines. A possible explanation
for this is that the normal lungs of cetacea are extremely heavy due to anatomic
peculiarities; namely, cartilage bars extending to terminal bronchioles, thick
smooth muscle sphincters throughout the
lower airway, thick, double alveolar walls,
and a thick dense pleura. Any pathological alteration of a degree sufficient to
change the weight by a significant percentage might well be catastrophic, and
the animal would die at sea.
It is evident from the data presented
above that any statement of organ weight
in this, and presumably in related species,
is meaningless if not considered together
with the body length. I n this species,
non-endocrine organ weight and body
length are closely related. It is considered
that as total body weight is related mathematically to body length, as expressed in
Sergeant's equation, inferences relating
organ weight to body weight are valid.
The graphs presented, in that they express changing organ weight in relation
to changing body length, may be said to
express organ growth i n the species.
The age-sex-length and the tcstis-weightbody length relationships are in excellent
agreement with previous observations
made by Sergeant ('62).
ACKNOWLEDGMENTS
The author is deeply indebted to many
people for advice and assistance, and
would like to express his gratitude to Dr.
G. C . McMiUan, Strathcona Professor of
Pathology and Dr. H. Sheldon, Associate
Professor of Pathology, McGill University,
Montreal; to Dr. James Roberts, Jr., Robert Brownell, Jr. and Robert Boice of the
Cetacean Research Laboratory, Little Com-
628
DANIEL F . COWAN
pany of Mary Hospital, Torrance, California; to Dr. D. E. Sergeant, Arctic Unit,
Fisheries Research Board of Canada, Montreal, and to Miss Elspeth Angus of the
Pathological Institute of McGill University.
LITERATURE CITED
Nishiwaki, M., and T. Yagi 1953 On the age
and growth of the teeth in a dolphin (Pro-
delphinus caeruleo-albus). Sci. Repts. Whales
Res. Inst., 8: 133-146, Tokyo.
Sergeant, D. E. 1959 Age determination of
odontocete whales from dentinal growth layers.
Norwegian Whaling Gazette No. 6, pp 273-288.
1962 The biology of the pilot or pothead whale
Globicephala meluena (Traill) in Newfoundland waters. Bull. 132, Fisheries Research
Board of Canada. Ottawa.
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