FATTY ACID COMPONENT OF SENEGALMANATEE FATS
SHINGO ITOHANDHIDEO TSUYUKI
Departmeni of Food Engineering, College of Agriculture & Veterinary Medicine, Nikon Universiry, Tokyo.

ABSTRACTThe fats in cerviel, thoracic and dorsal fatty tissues, and thoracic muscle
tissue of Senegal manatee, Trichechus senegalensis, were analyzed for total lipid
content and fatty acid components. Although the above three fatty tissues
of Senegal manatee contained very rich amounts of fat, the muscle tissue contained consisderably small quantity of fat.
The fatty acid components of Senegal manatee fats contained high levelsof C14:0 (14.97-18.66%), C16:0 (24.57-27.78%), C16:1 (6.69-7.32%) andC1s:1 acids (36.86-39.75%), and had a unique proportion with higher levelsof saturated acids (50.16-52.93%). Although the fatty acid component anddistribution pattern in Senegal manatee fats deviated from most of marine
and fresh water mammals, those was nearly closed to that of Dugong fat.
INTRODUCTION

Manatees-sea cows-are completely aquatic and live solely on vegetation beneaththe water along coasts, and in estuaries and rivers. They are named as Trichechus
manatus in rivers and off coasts of Florida to British Guiana, as T. inunguis in riversof Brazil and as T. selegalensis in rivers of West Africa. Their adults reach up to
3 m in length and have remarkably fatty tissue body.
We have investigated the fatty acid component of Senegal manatee, T. senegalensis, fats. No previous studies of T. senegalensis fat have been reported in theliterature.
Greatest thanks are due to Mr. Kazue Nakamura of the Kanagawa Prefectural
Museum who was kindly enough to present us the Senegal manatee fat.
MATERIAL AND METHODSThe Senegal manatee, T. senegalensis, studied was caught by trawling at 60 km ofupper stream from the estuary of the Gambia river of West Africa in January 1973.
The mammal was an immature male of about 158.0 cm in length. The portions ofcervical, dorsal and thoracic fatty tissues, and thoracic muscle tissue were cut
up into small pieces and respectively extracted several times with chloroformmethanol (2: 1) using a high-speed blender. The solvent was dried with anhydrous
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308

sodium sulfate and completely distilled off under high vacuum. The properties
ofrecovered sample fats are shown in Table 1. Each sample fat was then subjected
to preparative thin layer chromatography on 0.25 mm thick layers of silicic acid
(Wakogel B-5, Wako-Junyakaku-Kogyo) developed with petroleum ether-ethyl
ether-glacial acetic acid (90: 10: 1). The fats in the above three fatty tissues
were almost entirely triglycerides and slightly the spots of cholesterol and cholesterolesters. On the other hand, the fat from thoracic muscle tissue was almost triglycerides similar to other sample fats. It had not only cholesterol and cholesterolesters, but also slightly phosphatides. The sample fats in cervical, dorsal and thoracic
fatty tissues were softenend at 33.9-34.2°C and cleared finally at 35.4-36.0°C in
1 mm id capilary. The fat from thoracic muscle tissue was softened at 32.6-34.1°Cand cleared at 35.0°C.
The sample fats converted to fatty acid methyl esters by the method of Metcalfe et al. (1966), using BF 3-methanol reagent. So as to purify, the fatty acid methyl
esters were then subjected to preparative thin layer chromatography on 2.00 mm
thick layers of Wakogel B-5 developed with petroleum ether-ethyl ether-glacialacetic acid (90: 10: 1).
TABLE 1.

PROPERTIES OF DIFFERENT TISSUE FATS OF SENEGAL MANATEE.
Fatty tissues

Appearance (at 30°C)
Oil content (%)
Refractive index (at 50°C)
Acid value
Iodine value
Saponification value
Unsaponifiables (%)

CervicalDorsalThoracicThoracicmuscletissueWhitishsemi-solid
78.0
1.4527
0.21
48.1
209.1
0.34

Whitishsemi-solid
69.1
1.4531
0.29
47.3
210.8
0.38

Whitishsemi-solid
71.8
1.4532
0.24
46.9
209.2
0.35

Yellowish
semi-solid
5.8
1.4536
0.32
47.4
207.7
0.51

The gas liquid chromatography (GLC) analyses of methyl ester samples were
performed with Shimadzu Model 4PTF apparatus using a hydrogen ionization
detector under the following conditions: 267 cm by 3 mm diameter glass column
containing 5 %DEGS on Chromosorb W (AW, DMCS), and operating at the temparature programmed from 70-190°C, 4°C per minute for short-chain components
and isothermally at the temparature 205°C for long-chain components. The carrier gas was flowed at the rate of 35 ml per minute by nitrogen gas.
The fatty acids were identified by comparison with standard mixtures (Applied Science Laboratories, Inc.) and GLC analyses with the same apparatus under
the same conditions between before and after hydrogenation by platinum black
reagent at the regular intervals. All fatty acid peaks were caluculated as weightpercentages of total known fatty acids presented by the method of Ettre and Kabot(1962).
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309

FATTY ACID COMPONENT OF DIFFERENT TISSUE FATS OFSENEGAL MANATEE.
Fatty tissues
CervicalDorsalThoracicThoracicmuscletissue

6:0
8:0
10: 0
12: 0!so 14: 0
14: 0
15: 0!so 16 :0
16: 0
17: 0
18: 0
19: 0
20: 0
Total saturated

0.81
0.31
3.14
1.65
0.04
15.98
0.50
0.31
24.82
0.54
2.73
0.09
0.74
51.66

trace
0.19
1.59
1.30
trace
14.97
0.28
0.37
27.78
0.47
2.53
0.05
0.63
50.16

0.72
0.27
2.52
1.54
trace
18.66
0.42
0.3524.57
0.36
2.77
0.04
0.70
52.93

0.16
2.09
1. 70
0.05
15.72
0.33
0.08
26.12
0.55
2.84
0.02
0.54
50.21

Monounsatrated
12: 1
14: 1
16: 1
18: 1
20: 1
22: 1
Total monounsaturated

0.14
0.41
7 .18
37.60
0.33
0.26
45.92

trace
0.28
7.30
39.75
0.21
0.20
47.74

0.09
0.36
6.69
36.86
0.25
0.19
44. 71

0.11
0.33
7.32
39.17
0.21
0.24
47.38

Polyunsaturated
14: 2
16: 2
16 :3
18: 2
18: 3
20: 2
20:3
20 :4
22: 2
22: 3
22: 5
22: 6
Total polyunsaturated

0.36
0.24
0.49
0.32
0.41
0.20
0.04
0.06
0.06
0.04
0.09
0.11
2.42

0.27
0.42
0.42
0.22
0.28
0.22
0.05
0.04
0.05
trace
0.06
0.07
2.10

0.35
0.28
0.43
0.34
0.40
0.24
0.03
0.04
0.04
0.02
0.08
0.11
2.36

0.33
0.30
0.46
0.41
0.51
0.13
0.02
0.02
0.05
0.01
0.07
0.10
2.41

100.00100.00100.00100.00Fatty acids
Saturated

RESULTS AND DISCUSSION
The properties of fats extracted from different tissues of the experimental Senegal
manatee are shown in Table I. High amounts of fat content were observed incervical, dorsal and thoracic fatty tissues as 78.0 %, 69.1 % and 71.8 % respectively.
But thoracic muscle tissue contained only a small amount fat of 5.8 %· It can be
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ITOH AND TSUYUKI

seen that other properties are nearly closed to each other.
The fatty acid components of fats contained in different tissues of the African
manatee are listed in Table 2. The sample fats were found to consist of 31 kindsof fatty acids with 6 to 22 carbon atoms, but the proportion of C6:o acid absents inthoracic muscle tissue fat. The fatty acid components and distribution patterns
were very closed to each other. High amounts of C14:o (14.97-18.66 %), C 16 :o(24.57-27.78%), C16:1 (6.69-7.32%) and C1s:1 acids (36.86-39.75%) were observedin all tissue fats. The combined percentages of C14: i, C16: o, C16: 1 and C 18: 1 acids
were respectively 85.58 % of cervical fat, 89.80 % of dorsal fat, 87.05 % of thoracic
fat and 91.53 % of thoracic muscle fat in total each fatty acid. The main constituents of the saturated acid were similarly C14:o and C 16:o acids whereas the monounsaturated acids were C 18 : 1 and C16:t acids. The least amounts of polyunsaturated
acids with more than double bonds were contained 2.42 % of cervical fat, 2.10% of
dorsal fat, 2.36 % of thoracic fat and 2.41 % of thoracic muscle fat. It is interesting
to note that 97.58 %-97.90 % of total fatty acids were only saturated and monounsaturated acids. The African manatee fats consist of the highest amounts of total
saturated acids. The ratio of total saturated acids vs unsaturated acids is about
half and half as followed: 51.66 % vs 48.34 % of cervical fat, 50.16 % vs 49.84 % ofdorsal fat, 52.93 % vs 4 7.07 % of thoracic fat and 50.21 % vs 49. 79 % of thoracic
muscle fat, respectively.
In the comparison with the fat contained in Dugong, Halicore dugong (Tsuyukiand Itoh, 1967), the Senegal manatee fats are most nearly allied to its fat. TheDugong fat was observed the high amounts of C 14 :o (9.8%), C16:0 (23.0%), C16:17.7%) and C 18 : 1 acids (41.3%) being similar to the Senegal manatee fats. The
fatty acids ofC 10 :o (0.1 %), C 12 , 0 (0.2%) and C 14:o (9.8%) contained in the Dugong
fat were slightly smaller levels than those of the Senegal manatee fats. But the
fatty acids of C14:o (0.8 %), C14:2 (0.9 %), C16:2 (1.6 %), C11:0 (1.2 %), C1s:2 (3.4 %)and C 18 :3 (4.1 %) contained in the Dugong fat were reversely higher levels thanthose of the Senegal manatee fats. It is a point of interest that the fatty acids withmore than 20 carbon atoms were not observed in the Dugong fat with exception ofC20:o (I. 7 %) and C20 ,4 (1.5 %). Although the fatty acid component and distribution pattern between the Senegal manatee and the Dugong fats were nearly symmetrical for most fatty acids, those deviated from most of marine and fresh water mammal fats.
SUMMARY

1. The properties of fats contained in different tissues of Senegal manatee,
T. senegalensis, was studied.
2. The fatty acid components of different fatty tissues and muscle tissue fats
extracted from the mammal had been determined by GLC analysis.
3. It was confirmed that four main fatty acids of C14:o, C16:0, C16:1 and C1s:1
accounted about 90 % of total fatty acids in those tissue fats; 26 others were foundin only low quantities.
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4. The Senegal manatee fat was nearly similar to the Dugong fat in the fatty
acid component and distribution pattern.
REFERENCESETTRE, L. S. and F.J. KABOT, 1963. Relative response of fatty acid methyl esters on the flame ionization
detector. J. Chromatog., 11: 114-116.
METCALFE, L. P., A. A. SCHMITZ and L. R. PELKA, 1966. Rapid preparation offatty acid esters from lipids
for gas chromatographic analysis. Anal. Chem., 38: 154-155.
TsUYUKI, H. and S. ITOH, 1967. Fatty acid composition of the Dugong oil. Bull. Jap. Soc. Sci. Fish., 33:
1035-1037.

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No. 26, 1974