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.