Camp. Biochem. Physiol. Vol. 88A, No. 3. pp. 549-551. 1987 Printed in Great Britain

0300-9629/87 $3.00 + 0.00 80 1987 Pergamon Journals Ltd

BIOCHEMICAL AND CALORIFIC CONTENT OF DEEP-SEA

ASPIDOCHIROTID HOLOTHURIANS FROM THE

NORTHEAST ATLANTIC OCEAN

Department of Biological

Department of Earth Sciences,

M. WALKER

Sciences, Bristol Polytechnic, Frenchay, Bristol BS16 1QY. UK,

P. A. TYLER*

University College. Swansea SA2 8PP. UK. Telephone: (0792) 205678

and

D. S. M. BILLETT

Institute of Oceanographic Sciences, Wormley, Godalming. Surrey GU8 5UB. UK

(Received 16 March 1987)

Abstract-l. The organic composition of the body tissues of eight species of deep-sea aspidochirotid holothurian, collected between 500 and 4100 m depth in the NE Atlantic Ocean, was obtained by the biochemical analysis of protein, lipid, carbohydrate and % ash.

2. The major organic class was protein with soluble lipid the major soluble fraction in the ovary. Carbohydrate values were consistently low.

3. The calorific value was significantly higher in the ovary than in the other tissues, 4. The total body caiorific content for two selected species. Benthothuria,funehri.~ and Mesothuria lactea.

was 25.62 and 26.24 J/mg ash-free dry weight (AFDW).

INTRODUCTION

The analysis of biochemical constituents and the

determination of calorific content is central to the

understanding of energetics in echinoderms as well as

in other animals (Lawrence, 1985). Until recently our knowledge of the organic composition of echino- derms was limited (Giese, 1966) but there is a growing body of data for the biochemical and calorific content of a variety of tropical, temperate and polar species (Prim et al., 1976; Lawrence and Kafri, 1979; Lane and Lawrence, 1981; Lawrence and Guille, 1982; Feral, 1985). However, data for the biochemical composition of deep-sea species is extremely limited (Barnes et al., 1976; Sibuet and Lawrence, 1981; Walker et al., in press). This paper presents the biochemical and calorific analysis of the body tissues of a variety of deep-sea aspidochirotid holothurians from the families Stichopodidae and Synallactidae.

MATERIALS AND METHODS

The aspidochirotid holothurians used in this study (Table I) were collected at a variety of stations between 500 and 4100 m depth in the Porcupine Seabight and Abyssal Plain in the northeast Atlantic Ocean by an epibenthic sledge (Aldred ef al.. 1976). The specimens were deep frozen on board ship for transfer to the laboratory where they were dissected into ovary, testis, gut wall. body wall (including muscle and calcareous ring where present) and respiratory trees (where possible). The separate organs were weighed, refrozen and freeze-dried.

Freeze-dried tissue was coarsely ground and 34 mg subsamples were homogenized with 600~1 of water in a ground glass homogenizer. The fractionation scheme was a

*Author to whom correspondence should be addressed.

modification of Holland and Gabbott (1971) and the follow- ing constituents were analysed: protein (Lowry et ul., 1951), total lipid (Marsh and Weinstein, 1966). and total poly- saccharide (Folin and Malmros. 1929). The residual ma- terial was assumed to be insoluble protein (Lawrence and Kafri, 1979). Ash content was determined gravimetrically by heating at 450°C. Calorific conversions followed the scheme of Brody (1945). The data are presented as J/mg ash-free dry weight (AFDW) for all tissues (1 joule = 0.239 Cal).

For direct calorific determination by microbomb cal- orimetry a piece of freeze-dried tissue was pelletized and combusted in a Phillipson microbomb calorimeter using Benzoic Acid as a standard (26433 J/mg). All the data are presented as J/mg AFDW. The data have not been corrected for the endothermic effects of calcium carbonate decom- position (Paine, 1971).

None of the species examined, with the exception of Stichopus tremulus, reproduces seasonally (PAT, pers. obs.) so data obtained at different times of the year have been pooled.

RESULTS

The composition of the main soluble constituents,

insoluble protein and % ash are given in Table 1. For each tissue biochemical data are given on the top line and the calorific content determined from the bio- chemical data in the parentheses underneath. Protein was the dominant organic constituent in all tissues of all species although most of the protein is in the insoluble form. Of the soluble biochemical constitu- ents lipid is significantly higher in the ovary than other tissues whilst soluble protein was usually the dominant fraction in the testis. The % ash varies from 1625% in the ovary to 42-64% in the body wall. Some of this ash will be calcium carbonate as the body wall in some species contains numerous calcareous ossicles (Hyman, 1955).

549

550 M. WMscER et al.

Table I. Biochemical and calorific content of aspidochirotid holothurians. All biochemical values are in pg/mg ash-free dry weight (+ I SD). All calorific values for individual constitutents in parentheses. and total tissue are in J/mg ash-free dry weight

Species

Number of specimens

Soluble Tissue protein

Sfichopus rremulus

Bathyplores naluns

Testis 1 239.0 286.7 (5.65) (I 1.34)

Gut I 89.4 48.3 (2.1 I) (1.91)

Body wall 6 122.7 + 53.7 66.1 k 20.6 (2.90) (2.61)

Ovary 1 70.4 k 26.3 245.7 f 60.8 (I .66) (9.71)

Testis I 147.2 29.2 (3.47) (1.15)

Body wall 38 143 + 61.3 126.9 i 112.2 (3.38) (5.01)

5.7 486.6 19.4 (0.10) 7.6

(0.13) 19.5 * 12.2

(0.34)

17.3 f II.0

(0.3) 10.9 (0.19)

18.7 i 8.4 (0.32)

(11.08) 854.7 38.4 (20.2)

791:8 f i3.7 42.7 k 5.8 (18.72)

666.7 k 54.0 17.5 f 4.0 (15.76) 811.8 19.4 (19.19)

710.4 + 141.1 43.9 k7.5 (16.8)

Mesorhuriu Ovotestis I 214.5 199.2 3.1 583.2 16.0 infestinalis (5.07) (7.87) (0.05) (12.12)

Body wall I 110.2 43.7 21.4 824.7 48.9 (2.hl) (1.73) (0.37) (19.5)

Mesolhuria Ovary I 22. I cerrilli (0.52)

Teals 2 189.2 f 86.3 (4.47)

Gut I 68.4 (1.63)

Body wall I 79.3 (1.87)

323.9 (12.8)

58.6 i 6.8 (2.32) 72.99 (2.89) 33.8 (I .34)

13.8 (0.24)

8.7 i 5.7 (0.15)

9.4 (0.16) 17.4 (0.3)

640.4 24.9 (15.15)

745.9 f 76.1 22.5 & I.5 (17.63) 848.7 32.5 (20.06) 869.4 42.3 (20.55)

Mesuthuria lacrea

Ovary 2 31.2 f 26.2 324.5 * 92.1 14.6 k 5.9 630. I f 50.3 18.2 k 14.0 (0.74) (12.83) (0.25) (14.89)

Testis 3 179.5 + 53.1 65.9 t 22. I 17.6 t 3.4 136.2 + 55.9 27.9 k 8.5 14.24)

85.0 + i8.2 (2.61) (0.3) (17.4)

Gut 4 84.8 & 71.8 26.7 + 14.1 803.5 k 96.5 43.2 f 8.6 (2.01) (3.35) (0.46) (1X.99)

Body wall I3 127.9 F 76.0 133.9 * 100.1 24.6 f 15.7 713.6 k 163.9 63.3 + 6.8 (3.02) (5.3) (0.42) (16.86)

Benthothuria Ovary 4 88.9 f 61.3 133.5 + 36.8 22.8 k 12.4 554.8 + 59.4 21.5 i 16.2 ./inebris (2.10) (13.19) (0.39) (13.1 I)

Testis 2 81.2 + 75.8 I 14. I +_ 54.2 I I .9 & 5.5 792.9 k 135.5 Il.5 i 3.1 (1.91) (4.51) (0.2) (18.74)

Gut IS 142.5 * 45.8 112.6 + 53.1 33.4 f 9.5 711.5k83.6 36.1 t9.2 (3.36) (4.45) (0.57) (16.81)

Body wdll I9 112.4 k 46.2 130.2 + 112.7 19.3 k 9.2 738.1 k 96.7 50.7 k I I .8 (2.66) (5.15) (0.33) (14.44)

Paeloparides Body wall I I 66. I + 28.2 40.4 + 14.6 21.5 i 4.6 872.1 + 96.7 57.3 k 4.5 grisra (1.56) (1.60) (0.37) (20.61)

Pseudostichopus Body wall I 59.8 23.22 20.4 896.6 51.8 atlunrrcus (1.41) (0.92) (0.35) (21.19)

Soluble lipid

Soluble Organic Total tissue caloritic content (Biochemical (Microbomb

carbohydrate remainder’ % Ash determination) determination)

28.17 22.01

24.35 ND

25.57 14.33

27.43

24.0

25.51

24.03

18.83

16.74

25.71 23.61

24.2 I 14.87

28.69

24.57

24.74

24.06

27.22

17.83

23.84

13.66

28.71

24.55

24.81

25.6

21.26

IX.99

12.31

13.84

28.79 21.89

25.36 19.73

25. I9 16.38

25.5x 13.63

24. I4 13.03

23.87 12.26

*Usually considered to be insoluble protein (Lawrence and Kafri. 1979)

The calorific content of each tissue determined from the biochemical analyses (Table I) indicates a significantly higher value in the ovary than the other tissues (Table 2) although when the calorific content of the different tissues, calculated by microbomb calorimetry, is compared the ovary has a significantly higher value than the testis and body wall but not the

Table 2. Paired I -values for the comparison of the calorific content of the different tissues of aspidochirotid holothurlans by the bio- chemical method (top right) and microbomb method (bottom left). Data for the hermaphrodite Mesothuria inkwin& omitted.

Number of hairs tested in parentheses

Ovary Testis Gut Body wall

Ovary 18.45 (4)t 34.92 (3)t 5.80(4)t Testis 3.84 (4)’ 0.9 (4) 0.09 (5) Gut 2.24 (3) 0.35 (3) I .44 (4) Body wall 6.4 (4)t 5.38 (5)t I.11 (3) -

*Significant difference at the 95% level. tsignificant difference at the 99% level.

gut owing to the high variability in the gut calorific value in a small data set (Table 2).

When the calorific content of each tissue deter- mined by the two methods is compared (Table I) the values determined from the biochemical analyses are significantly higher for the testis and body wall (Table 3). The lower values obtained by direct calorimetry may be a function of the endothermic decomposition of calcium carbonate in the tissues during ignition in the microbomb.

Table 3. Paired t-values for the comparison of the calorific content of tissues determined by biochemical and microbomb methods for

aspidochirotid bolothurians

I n Sigmficance level

ovary* 2.57 4 NS Testis* 21.49 5 99.9% Gut 2.16 3 NS Body wall 26.0 8 99.9%

*Excludes the hermaphrodite Mesofhuria inrestinalis.

Holothurian calorific content 551

Table 4. The calorific values of two species of aspidochirotid holothurian

Bodv comuosition % ash-free dry weight

Ovary Gut Body wall J/mg Cal/g

Benfholhurio jiinebris 2 4 94 25.62 6123 Mesorhuria lack-a 24 I4 62 26.24 6212

Calculation of total body calorific value from biochemical data gives a value for Benthothuriufun-

abris and Mesothuria lactea of 25.62 and 26.24 J/mg, respectively (Table 4).

DISCUSSION

Data on biochemical and calorific analyses of echi- noderm tissues are limited and for deep-sea species even more so. All the tissues examined here have a low level of soluble carbohydrate whilst the testis has a high level of soluble protein and the ovary a high level of soluble lipid. In all tissues insoluble protein is the dominant constituent. The ovary of each species contains oocytes in various stages of develop- ment (PAT, pers. obs.) and yolk, determined by histochemistry, tends to be dominated by a protein/ carbohydrate complex but with a considerable amount of neutral lipid. This lipid is the main energy store having a higher calorific value per unit weight than the other constitutents and may also aid the buoyancy of the spawned egg.

The determination of calorific value by both bio- chemical and microbomb methods indicate signifi- cantly different values for each tissue except the gut. This may be a function of the calcium carbonate content of the body tissues (Paine, 1971) although it would not be expected to affect the microbomb data by more than 10%.

The total body calorific value for two species is 25.62 and 26.24 J/mg (6123 and 6271 Cal/g) AFDW, respectively. This compares with 5800 Cal/g AFDW for Benthogone rosea and Psychropotes longicauda

from the Bay of Biscay (Sibuet and Lawrence, 1981). These data suggest that deep-sea holothurians are macroconsumers (Cummins and Wuycheck, 1971) which usually have large deposits of energy-rich lipids. Lipids are particularly evident in the very large eggs found in deep-sea holothurians. The lack of lipid storage in the body wall may be owing to the size and thickness of the body wall where storage space is not limited. Protein is the main deposit in the body wall and is found primarily in thick layers of connective tissue (Krishnan, 1968).

Acknowledgements-We wish to thank the Master and crew of RRS Challenger for their assistance at sea. This research was carried out under contract for the Department of the Environment as part of its radioactive waste management research programme. While the results may be used in the formation of Government policy, at this stage they do not necessarily represent Government policy.

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