Ekologiya Morya (5): 65-76, 1981

ISSN 0704-3716

CANADIAN TRANSLATION OF FISHERIES AND AQUATIC SCIENCES lqo. 4818

Energy balance in prolific species of crustacea from the Indian Ocean

by T.V. Pavlovskaya, and Gj. Abolmasova

Original Title; Energeticheskiy balans u massovykh vidov rakoobragnykh indiyskogo okeana

From: Ekologiya Morya (5): 65-76, 1981

Translated by the Translation Bureau (NDE) Multilingual Services Division Department of the Secretary of State of Canada

Department of Fisheries and Oceans Bedford Institute of Oceanography Dartmouth, NS

1982

21 pages typescript ' crews- Li e • • DEPARTMENT OF THE SECRETARY OF STATE SECRÉTARIAT D'ÉTAT

TRANSLATION BUREAU BUREAU DES TRADUCTIONS

MULTILINGUAL SERVICES DIVISION DES SERVICES CANADA DIVISION MULTILINGUES

TRANSLATED FROM TRADUCTION DE INTO EN Russian English

AUTHOR - AUTEUR T.V. Pavlovskaya , G.I. Abolmasova

TITLE IN ENGLISH TITRE ANGLAIS Energy balance in prolific species of Crustacea from the Indian Ocean

TITLE IN FOREIGN LANGUAGE (TRANSLITERATE FOREIGN CHARACTERS) TITRE EN LANGUE ÉTRANGÉRE (TRANSCRIRE EN CARACTÉRES ROMAINS) Energeticheskiy balans u massovykh vidov rakoobraznykh indiyskogo okeana

REFERENCE IN FOREIGN LANGUAGE (NAME OF BOOK OR PUBLICATION) IN FULL. TRANSLITERATE FOREIGN CHARACTERS. RÉFÉRENCE EN LANGUE ÉTRANGÉRE (NOM DU LIVRE OU PUBLICATION), AU COMPLET, TRANSCRIRE EN CARACTÈRES ROMAINS. Ekologiya morya

REFERENCE IN ENGLISH - RÉFÉRENCE EN ANGLAIS

Marine Ecology

PUBLISHER - ÉDITEUR PAGE NUMBERS IN ORIGINAL DATE OF PUBLICATION NUMÉROS DES PAGES DANS DATE DE PUBLICATION L'ORI GI HAL "Naukova dumka" YEAR ISSUE NO. 65-76 VOLUME PLACE OF PUBLICATION ANNÉE NUMÉRO NUMBER OF TYPED PAGES LIEU DE PUBLICATION NOMBRE DE PAGES DACTYLOGRAPHIÉES Kiev, USSR 1981 5 21

REQUESTING DEPARTMENT D F 0 TRANSLATION BUREAU NO. MINISTÈRE-CLIENT NOTRE DOSSIER N° 861144

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Client's No.—No du client Department — Ministère Division/Branch — Division/Direction aw - Ville D F 0 S.I.P.B. Dartmouth, N. Bureau No.-1\10 du bureau Umguage — Langue Translator (Initials) — Traducteur (Initiales) 861144 Russian N. De. MAR 12 1982 Ekologiya morya (Marine Ecology), 1981, No. 5, pp. 65-76 (65)* UDC 591.531.31:595.3:577.475 Energy balance in prolific species of Crustacea ' from the Indian Ocean by T.V. Pavlovskaya & G.I. Abolmasova The determination of the feeding relations between organisms an the quantitative tendencies of the transformation of matter and energy by ecological groups within communities are the major points when studying the flow of energy through an ecosystem. These in- vestigations are based on the determination of the rate of consump- th tion of various types of food andYlndividual elements of the energy balance in the most prolific species of the zooplankton. Investi- gations of this type have been carried out on organisms from the

L&J Z legvl boreal zone of the ocean [10, 11, 19-22, 26, etc.], but not very 0 ›- < g CC E many have been conducted in the tropical zone of the World Ocean

0 If) C 2 nr. Z o 0 g [9, 14, 16, 23, 25]. The energy balance in the organisms of the < z e (66) e E z ô Indian Ocean has not been studied at all During the fourth run E of the "Professor Vodyanitsky" research vessel, we studied the C) o D ch g following questions: the composition and size of the rations in prolific species of crustaceans during mixed feeding on live algae, phvtogenic detritus and small animals, the effectiveness of assimilation and the ratio of the inàividual elements of their energy

*The numbers in the right-hand margin are the pages of the Russian text - translator

SEC 5-25T (Rev. 6/78) balance, and the diurnal rhythm in the feeding of crustaceans.

Material and Method

The object of our study were six of.the.-most prolific species of crustaceans in the study areas, Scolecithrix danae Lubbock,

Pleuromamma abdominalis Lubbock, Euchaeta marina Prestandrea, Eu- chirella cu.rticauda Giesbr., Rhincalanus nasutus Gièsbr. and Cypri- dina serrata G.W. Mtlller.

The material was collected with DZhOM* nets with an intake dia- meter of 80 cm, made with. silk gauze No. 23 (mesh size 0.333 mm).

Nets made with gauze No. 49 (mesh size 0.112 mm) were used to catch the small animals which were used as food in the experiments. After being caught, the animals were sorted according to species and size, and then placed in large containers where they were kept until ready for use.

Some of the selected animals were measured, cleansed of salt with an isotonic solution of ammonium carbonate, and then used to determine the energy equivalent of body mass.

The energy balance of copepods was studied by the radiocarbon method [1. 8]. One-litre containers were used in the experiments.

From 3 to 23 specimens were used in each experiment, depending on the size of the animals. The experiments were carried out only with females. A mixture ofsmall animals,unicellular algae and phytogenic detritus was used as food in all the experiments. The consumption of the various components from the mixture was determined by the method of alternate labelling of the items.

*acronym unknown, transliterated from the Russian - translator -3-

As shown by a preliminary and detailed study of the qualitative composition of the phytoplankton [2], small species of the genus Gymnodinium comprised the bulk of its biomass. Therefore, a mono- culture of Gymnodinium lanskaya and detritus prepared from these algae were given to the animals as aphytogenic, foOd. -In , some s experiments, the crustaceans were fed Ditylum brightwellii which had been brought back from the Indian Ocean by L.M. Sergeyeva l . The small zooplankton in the study areas consisted mainly of Temora and Oncaea species which were used as food in the experiments.

The unicellular algae Gymnodinium lanskaya and Ditylum brightwellii were grown on liquid media with 500 pC.1 -1 in diffused light.

The detritus was prepared from unicellular algae, G. lanskaya, by

a method described earlier [7]. The detrituà decomposed for a period of 7 days at a temperature of 22-25°C. In order to obtain a radioactive animal food, small crustaceans were first kept on

t the food components labelled unicellular algae for 2-3 days. The concentration- in the balance experiments corresponded approximately to their abun- dance in the 0-100 m layer. According to our calculations, this amounted to about 0.5 - ca1.1 -1 of phytoplankton, the same amount of detritus and 1.1-2.0 cal.1 -1 of small zooplankters. The experiments were conducted during the day and night in

order to determine the diurnal rhythm of the feeding rate. , The temperature was 21-22 °C in the experiments with S. danae, P. abdominalis, E. marina and E. curticauda, and 24 °C in the experiments with

R. conutus and C. serrata.

1We wish to thank L.A. Lanskaya and L.M. Sergeyeva for the cultures of unicellular algae. (67) The daily food balance of the crustaceans was determined by the sum of the individual elements, i.e. C = C d +R e +ReR s , where c denotes the ration, cd - the amount of energy accumulated in the body, R 0 .-energy expended on respiration, cd+R c - the amount of assimilated food (A), R s - solid excreta, R d - liquid excretions in the form of a dissolved organic substance, and R d+Rs - the unassimilated part of the ration (F). Food assimilability was determined by the equation a = Cd+Re

In order to determine C d , the animals were removed from the experimental containers, washed with an isotonic solution of ammonium carbonate, ground in a mortar, transferred onto a sheet of foil and dried at 60 °C. The water, which_contained the excreta of the animals, was passed through a membrane filter ("Synpor-3"), and the value R s was calculated. In the filtrate, we determined the amount of CO 2 released by the animals during respiration (R e ) and the content of dissolved organic matter (Re). The radioactive pre- parations were counted on an automatic VAV-100 radiation counting scaler with a SBT-13 end-type counter. All the experimental results obtained in carbon units were converted to energy coefficients The 24-hr values of all the elements of the food balance of the animals were obtained from the corresponding initial components of the balance, which were determined in brief experiments. The animals in these experiments were kept on labelled food for the length of time required for its digestion, and this vai.ied from 30 min to 1.5 hrs, depending on the type of food and the time of day, and they were kept on unlabelled food for 2.5-3 hrs.

The method of wet combustion with a 15% correction for incom- plete oxidation of organic matter was used to determine the specific

activity of the food items (Cr) and the energy equivalent of the body mass of the animals. [4]. The values of the energy equivalent of body mass and the size characteristics of the study animals are given in table 1.

Table 1. Size characteristics and energy equivalents of body mass of the prolific species of crustaceans of the Indian Ocean

alleprenviecKurt 2 c p 31. - 4Hcao thtcno Hui; *HBO/. , 3KonumenT D Naccu /e.la ce_ 1 mufflumelloro Hamepe- p„mep al liblX x Iniel I, MM 4npso6e x 7— Oncaea sp. 15 1,22 0,03 25 0,130 0,096 — • 41 0,062 Temora sp. 8 1,55 0,04 50 0,114 • • 0,116 — 50 0,118 Rhincalanus nasutus 18 4,12 0,09 10 0,500 0,482 — • 10 0,467 Cypridina serrata 16 2,10 0,04 10 0,567 10 0,711 0,536 0,09 10 0,411 Scolecithrix dana .e 15 2,15 0,02 10 0,944 10 0,931 0,938 0,004 • 10 0,938 Euchaeta marina 5 3,26 •,-, 0,03 4 1,095 — — •Pleuromamma abdominalis 10 4,40 0,04 3 1,806 3 1,679 1,771 0,05 - 3 1,829 Pleuromamma abdominalis 9 4,37 0,04 4 1,600 4 1,141 1,50 0,06 4 1,490 Euchirella curticauda 10 4,05 0,07 3 3,560 3 3,657 3,647 0,05 3 3,724

•Key to table 1: 1 - Species of animal; 2 - Number of measure- ments; 3 • Average length, mm; 4 - Number of animals in sample; 5 - Energy equivalent of body mass

The method of preparing the food and carrying out the experiments has already been described [9, 16]. -6-

Results The experiments with the animais on mixed food showed (table 2) that the crustaceans studied consumed all the types of food supplied, but the degree of consumption of the plant and animal food differed sharply. For instance, the daily rations during feeding on plant food (including live algae and detritus) varied from 1.2% of body mass in E. rostrata and E. marina to 20.4% in R. nasutus. The consumption of live algae and detritus also differed, i.e. S. danae,

E. curticauda, E. marina and P. abdominalis preferred detritus, while C. serrata and R. nasutus preferred algae. The rations were considerably larger during feeding on animal food, and varied from

13.2% of body mass in S. danae to 178.9% in C. serrata. The amount of expended energy was unevenly distributed between the elements of the energy balance in crustaceans fed individual foods (table 2). In the majority of anima i s consuming allthe types pe of food, the energDon respiration (R e ) greatly exceeded the energy accumulated in the body (cd ). The exception was E. marina, in which Cd accounted for 67.5-70% of the assimilated food; further- more, the accumulated energy was higher than the energy expended for respiration in S. danae and R. nasutus which were fed several types of food. During feeding on plant food, the solid undigested remains (Re) usually constituted 80-90% of the total amount of unassimilated food, whereas the proportion of liquid excreta (R d ). increased significantly in the majority of crustaceans feèding on animal food (to 46-56%). Table 2. Daily average values of the energy balance of planktonic crustaceans, % of the energy equivalent.of body mass ......

^x ô 1 21 3-â Ï ^1 4 °^ 06ZeKT ô x s ~ 1 ^^ Cd RC Rs Rd A C EC Çd Rs A F x ^ô l û x x ^Ox X

Scolecith- G. Ian - 1,1 0,5 14 0,06 0,14 0,18 0,02 0.2 0,4 30,0 90,( rix danae skaya ,i1;eT.- 4,0 0,5 13 0,46 0,34 0,55 0,05 0,8 1,4 15,0 57,5 91,( a puT b Men, 86,0 1,0 13 1,03 4,47 6,60 1,10 5,5 13,2 18,7 85,-) tcue Kone•+ noAM Pleura- ` G.lan•- 0,87 0,7 4 0,10 0,10 0,19 0,01 0,2 0,4 50,0 96,( mamma skaya abdomi- j.l',eT- 4,4 0,5 3 0,41 1,49 1,12 0,72 1,9 3,7 61,4 21,5 62,; nalis a pnT b Mea- 550,0 1,9-2,2 4 12,08 20,81 17,96 6,44 32,9 57,3 36,7 73,( xne r:one- no:iW Euchi- G.lan•- 0,8 0,7 4 0,01 0,08 0,10 0,02 0,1 0,2 11,1 83,1^ rella skaya curticaudt, ,L(eT- 4,4 0,5 5 0,01 0,50 0,37 0,05 0,5 0,9 27,1 1,9 88,( p11n On- 605,0 1,9 5 0,71 19,09 2,75 3,45 19,8 26,9 3,7 44,12 caea Euchaeta G. lan• 0,8 • 0,5 5 0,07 0,03 0,08 0,02 0,1 0,2 70,0 80,( marina skaya I)eT 4,4 0,5 6 0,27 0,13 0,40 0,20 0,4 1,0 42,0 67,5 66,( a pnT On- 86,0 2,8 5 21,91 9,49 6,95 2,45 31,4 40,8 69,7 73; caea Rhinca- D. 3,2 0,2 11 0,08 0,92 12,66 1,04 1,0 14,7 8,0 92,= lanus briôht- nasutus wellii a ,,TeT- 4,4 1 0.9 9 0,24 0,06 1,05 0,35 0,3 1,7 178,9 80,0 75,( PUT Temo- 445,0 1 2,3 8 10,53 21,07 70,33 60,57 • 31,6 162,5 33,3 53,1 ra Cypridi- D. 3,2 0,2 14 0,02 0,82 1,50 1,50 1,0 4,0 2,0 50,( na serrata bright• wellii a Zt,e- 4,4 0,9 18 0,09 0,41 1,70 1,10 0,5 2,3 186,1 18,0 94; Tp11T Temo- 445,0 2,3 15 10,05 19,75 80,90 69,20 29,8 179,9 33,7 53,£ ra

Key to table 2: 1- Object; 2 - Type of food, - detritus, b - smalcopepods; 3 - cr•10-5 of food, cal x imp-^; 4 - Concentration of food, cal x 1-1; 5 - Number of animals in experiment

(68) We conducted experiments with R. nasutus in order to establish the effect of the morphometric characters of unicellular algae on the rate of their consumption by animals. The crustaceans were fed a mixture consisting of the - small alga G. lanskaya, the large Ditylum brightwellii, detritus and animals. As a result of these experiments, we established a similarity in the rates of food consumption and assimilation, as well as in the ratios of the individual elments of the energy balance during feeding on two types of algae. For example, during the night, the intensity Of consumption for both species of algae amounted to 2.0 and 1.0% of the body mass, and the effectiveness of assimilation was 0.43 and 0.39. The following is noted when we study the values of food assimilation and consumption, as well as the individual elements of the energy balance during a 24-hr period. The amount of plant food consumed during the_day and at night was approximately the same in the majority of animals studied (table 3). Statistically significant differences were observed only in S. danae for the consumption of live algae, in P. abdominalis and C. serrata for detritus, and in C. serra ta for the consumption of animal food. Since the proportion of plant food in the ration of the animals was comparatively small, the noted difference did not have a significant effect on the diurnal rhythm of food consumption by the copepods. This rhythm was traced quite clearly only in C. serrata, i.e. its night ration was 5 times greater,than the daytime ration, and was due to a change in the rate of consumption 404 animal food. Table 3. Food consumption (10-4 cal•specimen-1) by crustaceans during the day and at night''

5 BpeMa S. danae L. curticauda L. marina R. nasutns C. serrata 1 BnA xopnca CVTn!C P. abdominalls

2OAHOKJTeTOlIHb[e ;^CIIb 10,1 ^ 1,6 41,9 51,9-}-7,5 650,0 116,0 BoJr,opoc.IH I101Ib 32,6 f7,1. 35,1-{-2,4 31,7±9,9 10,8 500,0+200,0, 110,0+30,0 3 3a cyzxlI 42,7 77,0 83,6 700,0 226,0 500,0 83,0 (DIlTorellHbll4 ]Zen 70,1113,4 161,6 189,6 ±23,6 jjeTpHT 1-Iovb 76,0± 9,8 518,4 148,7-F39,1 61,3 400,0 + 130,0 40,0-}-6,0 3a cyTxH 146,1 6?i0.0 338,3 900,0 123,0 4Me,.Iisne Copepoda AcHb 553.0 -I-55,0 4s190,0±290,0 3790,0 3780,0 1132,0 I-Ionb 722,3T190,0 5`10,0T210,0 5653,0+1105 2540,0+410,0. 3690,0 ±1750 9000.0 3a CyTRx 1276,2 10000,0 6032,0 7470,0 10132,0

Table 4. Effectiveness of food assimilation depending on the time of day or night in planktonic crustaceans

I : C. serrata 5 P. danac ' E. curticauda E. marina R. nasutus tD 1 Bnt uop+ta P. abdominal(s I •

0,39± 0,04 20JUI0ICJICTO1I11ble Z.I,eüb 0,50±0"11 0.30 0,22 _I.- 0,03 0,16±0,12 0,12±0,U6 BoAopocrIH Hotlb 0,39±0,06 0,52+0,04 0,62-h0,10 0,51 0,39±0.07 0,26 CpeAxee 0,45 0,41 0,43 0,51 0,27 0,24-I-0,06 3oIITÔrcHHbHi ACHb 0,72 ± 0,03 0,69 0,90 ±O, 16 0,23 AeTpxT Houb 0,40-{-0,09 • 0,44 0,76±0,03 0,43 0,32 ± 0,08 0,23±0,06 4 CpcAHee 0,57 0,57 0,55 0,43 0,28 0,23 Menxxe Copepoda T^exb 0,54-I-0,05 0,62± 0,08 0,57 0,39±0,15 0,32+0,03 0,10±0,03 0,14 1-lo4b 0,38 f0,09 0,54 0,82 ±0,04 0,77± 0,13 CpcAHee 0,42 0,58 0,70 0,77 ±0,13 0,25 0,23

Key to tables 3 and 4: 1 - Type of food, 2 IInicellular alggae, 3 - Phytogénic detritus, 4-'Small Copepoda;.5 - Time, a - daytime, b nighttime, c - for a 24-hr period, d - average The assimilability of both animal and plant food varied in many of the crustaceans throughout the 24-hr period (table 4). Due to these differences in the effectiveness of assimilation, the amount (69) of the total assimilated energy during mixed feeding differed during the 24-hr period. For instance, these values were twice as high during the night in E. curticauda and C. serrata, and 4 times greater during the day in R. nasutus. We observed no diurnal rhythm in the amount of assimilated energy in S. danae and P. abdominalis. It should be noted that the daily average values of assimilability were similar in the majority of copepods consuming unicellular algae and detritus (0.41-0.51 and 0.43-0.57 respectively), whereas the effectiveness of assimilation varied within a much wider range (from 0.42 to0.77) when animal food was consumed. The daily average values of assimilability for all types of food were considerably lower in R. nasutus and C. serrate, than in any of the other copepods studied (0.23-0.28). (70; Discussion Our experiments have shown that all of the crustacean studied are euryphages. However, the rate of consumption was considerably lower for plant food, than for animal food. The amount of plant food consumed in all of the crustaceans studied did not ex- ceed 12% of the total ration (see fig.), i.e. the crustaceans displayed a high degree of predaciousness in the study areas. Similar data were previously obtained for copepods from the tropical zone of the Pacific Ocean [14]. According to these data, the ration of the majority of crustaceans consisted 80-90% of small animals. Like the authors of tef. “41i we believe that with the great species diversity of the planton and its small biomass, the copepods in the tropical regions of the oceans have a broad feeding spectrum, but prefer animal food. Therefore, when conducting experiments on the feeding of mature 1.5-2 mm copepods in the oligotrophic regions of the ocean, we believe we can confine ourselves to studying the quantitative indices of animal food consumption and assimilation, and then add 10-15% to this ration to account for the plant food consumed

%IZ:la1. IMiS EMC

Ratio of the individual types of food in the ration of crustaceans from the Indian Ocean: a - animal food, b - live algae, c - detritus; 1 - S. danae, 2 - P. abdominalis, 3 - E. curticauda, 4 - E. marina, 5 - R. nasutus, 6 - C. serrata

Analysis of the effect of the morphometric characters of the phytoplankton on the ration of copepods based on the example of

R. nasutus showed that the crustaceans displayed no selectivity in the presence of an equal, fairly low concentration of small -1 unicellular G. lanskaga and large D. brightwellii (0.5 cal.1 each). Perhaps, size selectivity with regard to algae could not be clearly traced in the areas with a small phytoplankton biomass, where the crustaceans fed mainly on animais. All the animals fed very actively in our experiments. Their total daily rations constituted from 15 to 186.6% of the body mass. The minimum value was observed in the comparatively small copepod

S. danae which we expected would show a higher rate of food consumption. This was apparently due to the fairly low concentration -1 of food in the experiments (1.1 cal.1 animal and 1.0 cal•1-1 phytogenic). Our new data on the feeding rate of animals from the In- dian Ocean are quite consistent with the data available in the literature for certain crustaceans, particularly E. marina, P. abdominalis and R. nasutus 1 8, 9, 14, 15] which are found in similar feeding conditions (table 5). The daily rations of these animals, which have been determined by various authors, differ insignificantly.

For instance, the daily ration of E. marina feeding on animal food constituted 38.0-48.5% of the body mass in the majority of cases, and 180% in only one case. Very similar ration values were obtained in all the experiments where E. marina were fed on phytogenic food. A good similarity of results was noted when comparing the consumption of both animal (35.0-57.0%) and phytogenic food (3.7-4.4% of body mass) in P. abdominalis. The rate of plant food consumption in R. nasutus was also similar in the different experiments (3.0- 14.7% of body mass), but there was an 8-fold difference in the consumption of animal food (with the saine food concentration of 2.2 cal-1 -1 ). At the same time, according to T.S. Petipa and coauthors

[15], the ration of R. nasutus constituted 108.9% of the body mass -1 at a - lower concentration of animal food (0.68 ca1 -1 ), i.e. this (72) value is comparable to our results (162.5%). The small ration in

R. nasutus [14] can apparently be attributed to two causes, i.e. either the copepods were in a suppressed physiological condition,

or they were rapidly reproducing at this time. As established [15],

the rate of food consumption in crustaceans decreases significantly

during rapid reproduction.

Table 5. Daily average rates of food consumption and the effectiveness of food assimilation in tropical copepods

Daily ^ Energy Food 1 Species of equiva- Composition concent ratï.on .^.,j consumer lent of of food ration % of H. Source body, mass cal•1 -i body N ...... cn rtS. . câl: -'s 'p mass

Etzchaeta 0.5 Calanidae 2.5 38.0 0.62 Petipa marina Amphidinium 0.2 2.6 0.21 et al.[14] Bacteria 0.3 0.9 0.47

0.9 Artemia nauplia 1.0 180.0 0.60 Our data Proroc-ent?rum 1.0 16.3 0.25 [9] Chlorella detr. 1.0 2.7 0.59 Bacteria 1.0 37.3 0.58

1.2 Artemia nauplia 1.0 48.5 0.63 Our data Peridinium 1.0 6.3 0.88 [8] Gymnodinium lanskaya detr. 1.0 0.3 0.58

l.l Oncaea 2.8 40.8 0.77 Data of Gymnodinium 0.5 0.2 0.51 present Gymnodinium paper detritus 0.5 1.0 0.43

Pleuromamma 1.4 Calanidae 2.5 35.0 0.64 Petipa abdominalis Amphidinium+ et al. [141 +Glenodinium 0.3 4.4 0.57 Bacteria 0.5 3.4 0.56

1.8 Small Copepoda 2.2 57.3 0.58 Gymnodinium 0.5 3.7 0.41 Data of Gymnodinium present detritus 0.5 0.4 0.57 paper

Rhincalanus 0.7 Calanidae 2.2 20.0 0.59 Petipa nasutus Amphidinium 0.3 3.0 0.36 et al.[15] R. cornutus Bacteria 0.4 3.5 0.21

0.6 Calanoida 0.68 108.9 0.39 Petipa Infusoria+algae 4.3 7.2 0.43 et al.[15] Bacteria 2.1 3.6 0.21

(table continued on next page)

(table 5 continued)

0.5 Temora 2.2 162.5 0.25 Data of Ditylum 0.5 14.7 0.27 present Gymnodinium 0.5 0 paper Gymnodinium detritus 0.5 1.7 0.28

When analyzing the daily average effectiveness of food assimilation in these crustaceans, we should also note the great simi-

larity of our results with those obtained earlier for E. marina,

P. abdominalis and R. nasutus (table 5). The daily average assimilability on a mixed ration in animais caught in the first two

areas (S. danae, P. abdominalis, E. curticauda, E. marina) amounted to 0.47-0.57, which, in the opinion of T.S. Petipa et al. [15], is characteristic of ocean waters; it was considerably lower (0.24-

0.26) in R. nasutus and c. serrata from the third study area which is described in ref. [13]. (73) During our study of the diurnal variations in the energy balance, we found that, in the majority of cases, the crustaceans fed round the clock and no distinct changes were observed in their

feeding rate. The exception was C. serrata which consumed 5 times morè food during the night. At the same time, a diurnal rhythm could be traced when studying the effectiveness of assimilation and the ratios of the individual elements of the energy balance. For instance, there was a change in the amount of energy assimilated

during a 24-hr period in E. curticauda, R. nasutus and C. serrata, which was due to the irregularity of assimilability. We observed no tendency in the variation of this value, i.e. the assimilability of à11 the food types was higher during the night in E. rostrata, -15-

whereas animal food was assimilated more effectively during the daytime and phytogenic food during the night in E. nasu tus and

C. serrata. The same irregularity of assimilability has been observed in certain Pacific and Atlantic copepods [8, 14]. It is difficult to explain this phenomenon at the present time. T.S. Petipa et al. [14] believe that neither the food composition, the j-(2119-' etr;:ity, nor the feeding rate has any decisive effect on the diurnal changes in assimilability, and food assimilation as a physiological process has its own diurnal rhythm. This does not explain the cause of the observed phenomenon, and apparently re- quires more detailed investigation. While the literature does contain a certain amount of data on the feeding of oceanic copepods, this type of information on Ostracoda is very scarce and deals mainly with the qualitative aspect of this question [1, 23, etc.]. Our results are quite consistent with the data of Ye.G. Arashkevich [1] who, after dissect- intestines, established that, in the mesotrophic zone of the Pacific Ocean, they contained mainly the remains of crustaceans, predominantly copepods. Radiolaria, Diatomeae, Flagellata and other algae were also found in the intestines. The minimum size of the particles encountered was 20 1.t. According to our data, ridini may also consume smaller algae (the size of G. lanskaya is 11-12 p). We should also note certain deviations when comparing the quantitative aspect of feeding in crustaceans. According to _cypridinids, Ye.G. Arashkevich, the daily ration of------constituted 25- 30% of body mass, the calculation being based on the assumption that the intestine did not renew itself during intensive nighttime feeding. No such phenomenon was observed in our experiments; during the night hours, the ostracods actively excreted labelled feces after feeding on unlabelled food for 3-4 hrs. If there were no defecation, all of the consumed food would have remained in the body and the assimilability value would have approximated 1.0. According to our data, the daily average assimilability amounted to 0.23, and the ration constituted 186.1% of body mass. The data obtained on the feeding and total metabolism [5] of crustaceans, as well as the data on standard (basal) .Inetebolism in these animals [3], have made it possible to compare the amount of assimilated energy with the food requirements of individual species. If we compare the values of assimilated energy with basal metabolism, we can say that the minimum food requirements of all the crustaceans studied are satisfied. The exception is S. danae in which basal metabolism exceeded the energy assimilated (table 6). If we compare. the data on feeding with the energy expended on total metabolism, we see that the amount of assimilated energy exceeded total metabolism only in E. curticauda and C. sere rata; these values were similar in P. abdominalis, E. marina and

R. nasutus. However, as shown by T.S. Petipa, Ye.V. Pavlova, L.V. Tsareva and S.A. Piontkovsky [6, 12, 17], the availability of food greatly reduces the locomotory activity of the animals, which in (74) turn should result in lower oxygen consumption. Therefore, the respiration of the copepods in our experiments should apparently be higher than the values of . basal metabolism, but.lower than the values determined in large containers without food. On the basis of this, it can probably . _ be assumed that, in the given study areas and with food organisms in a concentration of about -17-

-1 2-3 cal-1 and consisting mainly of small animals, all of the crustaceans studied, except for S. danae, satisfy their minimum food requirements and, in addition to that, some of the assimilated energy is left over for other energy needs.

Table .6. Daily values of assimilated energy and the respiration requirements of crustaceans in the Indian Ocean (% of the energy equivalent of body mass) Assimi- Energ expended Species of animal lated 0n m tabolism food total standard

Scolecithrix danae 6.5 20.0 13.3 Euchirella curticauda 20.5 15.0 9.6 Cgpridina serrata 31.3 21.6 Euchaeta marina 32.0 40.0 12.8 Rhincalanus nasutus 33.7 44.0 15.5 Pleuromamma abdominalis 35.0 43.0 11.6

Conclusions 1. Wb have determined the main elements of the energy balance in six prolific species of crustaceans from the tropical region of the Indian Ocean with a low trophic level. All of the species studied are euryphages with the predominance of predatory feeding; food of animal origin accounts for up to 90% of the total expended energy. 2. The total daily rations of certain species constitute 15.0- 186.1% of the energy equivalent of body mass. 3. Similar daily average values of assimilability are noted in the majority of copepods during feeding on unicellular algae and detritus (0.41-0.51 and 0.43-0.57 respectively); the assimilability of animal food varies from 0.42 to 0.77. The daily average values of assimilability of all food types are considerably lower in R. nasutus and C. serrate (0.23-0.28). 4. We noted a single tendency in the ratio of the individual elements of the energy balance as a whole, i.e. the bulk of the assimilated energy was expended on the respiration of the animals, and the unassimilated food consisted 60-80% of solid excreta on the average.

5. The majority of animals studied did not show any diurnal rhythm in feeding; this rhythm manifested itself to the greatest extent only in C. serrata which consumed 5 times more food during the night. The ratios of the individual elements of the energy balance varied during the 24-hr period.

6. A comparison of the experimental data on the feeding of crustaceans in a medium with a food concentration of approximately

2-3 cal-1-1 and consisting mainly of small invertebrates with their respiration requirements has shown that all the species, with the exception of s. danae, not only satisfy their minimum food requirements, but also have enough energy left over to meet their other energy needs.

References

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T. V.. PlVLOVSKAYA, G. I. ABOLMASOVA ENERGY BALANCE IN COPEPODS MASS SPECIES FROM THE INDIAN OCEAN . • Summary The basic elements of energy balance are determined for 6 copepod mass species (Scolecithris danae, - Pleuromamma abdominalis, Euchaeta marina; Euchirella rostrata, Rhincalanus nasutus, Cypridina serrata from the tropic region of the Indian Ocean with reduced trophicity. All the studied species are euryphagous organisms, with carni- vorous nutrition prevailing. The total day diets of certain species accounted for 15.0-186.1 .%, of the body mass energy equivalent. Close average diurnal values of assimilation efficiency were marked for most copepods when they fed on unicellular algae and detritus (0.41-0.51 and 0.43-0.57, respectively), assimilation of animal food ranged from. 0.42 to 0.77. No diurnal feeding rhythm was observed in most animals under study, it was most pronounced in C. serrate only.

A.O. Kovalevskay Institute of South Sea Biology of the Received on 28 Feb 1979 Ukrainian Academy of Sciences