Aquaculture Nutrition 2001 7; 91^99 ......
Cultivation of Paracentrotus lividus (Echinodermata: Echinoidea) on extruded feeds: digestive eciency, somatic and gonadal growth
C. SPIRLET2,3, P. GROSJEAN1 & M. JANGOUX1,2,3 1 Laboratoire de Biologie Marine CP 160/15, Universite Libre de Bruxelles, 50 Av. F.D. Roosevelt, B-1050 Brussels, Belgium; 2 Centre reÂgional d'eÂtudes coÃtieÁres, Universite de Caen, Station marine ± B.P. 49, F-14530 Luc-sur-Mer, France; 3 Laboratories de Biologie Marine, Universite de Mons-Hainaut, 19 rue Maistriau, B-7000 Mons, Belgium
urchins and these must satisfy both size and quality (taste, Abstract ®rmness and colour) criteria. This study assessed the use of extruded feeds, in the form of Paracentrotus lividus is an echinoid that occurs along the pellets, for the growing of echinoid Paracentrotus lividus coasts of Western Europe and the Mediterranean region. The within a closed-culture system. Two feed types, one with in¯uence of abiotic factors (i.e. temperature and photoperiod) soya-bean protein, the other with both soya-bean and ®sh and frequency of feeding on somatic growth (SG) and protein were compared with dried Lessonia sp. and fresh gonadal growth (GG) have been examined for sea urchins Laminaria sp. as food sources. Pellets present a very high held in a closed-rearing system (Spirlet et al. 1998a, 2000). conversion eciency (about 80%) against about 50% for The development of formulated feeds is desirable on the Laminaria and 35% for Lessonia. However, as pellets are less grounds of availability, consistency of quality and composi- absorbed, somatic growth (SG) is statistically equivalent for tion, water stability, and ease of use in comparison with fresh the sea urchins fed with pellets and Laminaria between 2 and algae (Caltagirone et al. 1992; Fernandez 1996). 2.2% g soma day±1. Sea urchins fed with pellets produced The present study compares SG and GG of P. lividus fed signi®cantly more gonadal tissue in a shorter time, resulting with two formulated feeds, i.e. a dried alga (Lessonia sp.) and in a gonadal index (GI) twice higher (6.5%) than Laminaria an alga (Laminaria sp.) that constitutes the natural food of (3%) in the second month of the experiment. Dry Lessonia this sea urchin species. does not promote gonadal growth (GG). This study shows that extruded feeds are well assimilated by P. lividus and Materials and methods promote both SG and production of gonadal tissue. The P. lividus (Lamarck 1816) used were produced in the laboratory using methods described by Le Gall (1989) and KEY WORDS: aquaculture, arti®cial food, digestion, roe, sea urchin, somatic growth Grosjean et al. (1996, 1998). Individuals of 15±25 mm ambital diameter (excluding spines) were selected. The four foods tested (see Table 1) were extruded foods Received 8 September 1999, accepted 31 May 2000 based on soya-bean protein (soya-bean pellets ± SBP) or a Correspondence: C. Spirlet, Laboratoire de Biologie Marine CP 160/15, Universite Libre de Bruxelles, 50 Av. F.D. Roosevelt, B-1050 Brussels, mixture of soya-bean and ®sh proteins (mixed-food pellets ± Belgium. E-mail: [email protected] MFP), dried Lessonia sp. algae imported from Chile and presented as `sticks' of 1±4 cm long and fresh Laminaria sp. algae collected from the shore at low tide (Luc-sur-Mer, France). Introduction Two experiments were run, the ®rst in aquaria designed for Interest in cultivation of sea urchins has increased over the feeding and digestion studies (Fig. 1), and the second in the last two decades owing to the depletion of wild stocks as a rearing units described by Grosjean et al. (1998). result of over-®shing (e.g. Byrne 1990; Fernandez 1996). It is Four 160-L aquaria (one per diet) were each equipped with the gonads or roe, which represent the edible part of the eight individual holding baskets (Fig. 1) and were connected
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Table 1 Chemical composition of the Haug & Jensen (1954); food in dry mass (g kg)1) Klinger et al. Soya-bean Mixed-food Jensen (1956); (1998) pellet pellet Gayral & Cosson (1973) Laminaria sp. Lessonia sp.
Fish 286 Carbohydrates 1^2 No information could be obtained Wheat 259 275 Proteins 8^15 Soya-bean 445 232 Fat 1^2 Lecithin 9 9 Potassium 1.3^3.8 Vitamins 26 26 Sodium 0.9^2.2 Minerals 153 91 Magnesium 0.5^0.8 Cholesterol 5 5 Iodine 0.3^1.1 Fish oil 24 Cellulose 59 59
(¯ow rate of 50 L h±1) to ensure similar physico-chemical matter content was determined on 10 additional food parameters in all aquaria. Water temperature was portions each day (after drying for 48 h at 70 °C). The dry 201°C, salinity 33.5 g L±1 and pH NBS 7.95±8.05, and weight of food remains was assessed daily. The three empty photoperiod was set for 12 l:12 d. Water renewal, with baskets in each aquarium received portions of food for 50 lm-®ltered sea water, was ®xed at 500% per day. Prior to estimation of weight ¯uctuation with time, and correction of entering the aquaria, water was ®ltered on a 1-lm diatom ingestion rates. mechanical ®lter so that solid particles cannot get to the Immersed weight (batches weighed in sea water), stan- drawers with the faeces and the food leftovers. dardized according to Grosjean et al. (1999) is measured at Five holding baskets in each aquarium received batches of the beginning (just after the acclimatization) and at the end 15 sea urchins of mixed sex. Individuals were distributed at of the experiment. A direct relationship exists between the random and acclimatized to the rearing conditions during standard immersed weight (SIW in g) and the dry weight of 4 days before the start of a 15-day experiment. Portions of the soma S in g (Grosjean et al. 1999) which is: food were provided in excess and replaced every 24 h. The food was weighed fresh before distribution, and the dry- S 1:74SIW0:98; R2 0:999; n 224 1
Figure 1 Feeding aquarium, arrows indicate direction of water ¯ow. (1) rearing cylinders with perforated bare (5 or 10 mm mesh); (2) faeces collecting drawer (250 lm mesh); (3) pump; (4) re¯ector and lighting; (5) air diusor; (6) seawater inlet; (7) pre®lter; (8) dia- tom ®lter (1 lm); (9) ®lter pump; (10) over¯ow.
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Hence, the measure of SIW allows estimation of the initial the experiment. This is important for the accuracy of the and ®nal dry weight of the soma. Its precision is good enough results. to allow the calculation of relative growth rate of the soma The following parameters are calculated: the apparent SG (over a short period of time: 15 d) as: conversion eciency of the food (GrConv), the conversion S S eciency (Conv) and the apparent absorption eciency SG t max 0 2 t max S (Abs), which are calculated: respectively, as: SG SG where SG is expressed in percentage dry weight of the soma GrConv  100; Conv  100; per day, S and S are the initial and ®nal dry weights of GrI I 7 0 tmax A the soma in g, and S is their mean value. No mortality was Abs  100 I observed during the course of the experiment. They are all expressed in percentages. The apparent consumption is the amount of food that The second experiment was run in rearing units of the type disappears with time in the aquaria. It is calculated as described by Grosjean et al. (1998). A water renewal of follows: P 200% per day maintains the quality of the sea-water during tmax t1 Ft 1 Lt the experiment. The sea urchins used were 25 2 mm of GrI 3 t max S ambital diameter. where GrI is the apparent consumption in % of soma in dry A total of 240 sea urchins had been deprived of food for ±1 weight day ; t is time (days), tmax is the length of the 2 months to ensure that most of the nutrients present in the
experiment (15 d); Ft±1 is the dry weight (g) of the food gonads were resorbed.
portion distributed 24 h before t, Lt is the dry weight (g) of Prior to the experiment, four batches consisting of ten sea the leftovers at time t and S is the mean somatic dry weight urchins were weighed in water (standard immersed weight) (g) during the considered period of time. We de®ne the soma and dissected. The gonads and integuments were dried for by the animal excluding gonads. 48 h at 70 °C and weighed separately. The ingestion rate corresponds to the amount of food The 200 individuals were separated in four groups, each really ingested by the sea urchins, and is calculated after fed ad libitum with a dierent type of food. A total of 10 correcting the apparent consumption (food controls). Cor- individuals from each group were then killed after 30, 65 and rection coecient C is calculated as: 92 days of treatment, respectively. P tmax La At the end of the experiment, the immersed weight was C P t1 t 4 tmax determined before the echinoids were dissected and processed t1 Fat 1 with the aforementioned procedure. The SG was calculated where La is the quantity of leftovers in the controls at time t t as equation 2. and Fa is the amount of food introduced in the same t±1 Gonadal growth was assessed as follows: baskets 24 h before (in g of dry weight). Gdw Gdw Gdw Considering that the ingestion rate and variation of food GG t max 0 with Gdw c SIW 8 t max 0 SIW 0 are both continuous (food is nonlimiting and sea urchins feed c very slowly), the ingestion rate I (% g dry soma day±1)is where Gdw0 and Gdwt max are the estimated initial and the calculated as: ®nal measured dry weights of the gonads, respectively, SIW0 P hiis the initial standard immersed weight, and Gdwc and SIWc t max CFt 1 Lt Ft 1 Lt =C t1 2 2 are the mean dry weight of the gonads and the mean I 5 t max S standard immersed weight of the initial samples. Every 24 h, the faecal pellets produced by each basket of The dierential allocation of resources to gonads was sea urchins were collected separately, rinsed in 50 mL evaluated as the ®nal gonad index (GIt max) expressed as: distilled water and dried at 70 °C during 48 h before being Gdwt max GIt max 9 weighed. The apparent absorption rate is given by the St max Gdwt max following equation: Maturity stages were assessed by histological observation P t max Faeces and classi®ed according to an 8-stage scale (Spirlet et al. A I t1 t 6 t max S 1998b). The maturity index (MI) of a batch was calculated as: X8 MCnMC where Faecest is the faeces dry weight (g) collected at time t. MI 10 n GrI, I and A are thus calculated over the whole period of MC1 tot
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Figure 2 Rates of ingestion, absorption and somatic growth (SG) with the four dierent diets in the experimental aquaria. There are no signi®cant dier- ences between pellets. Signi®cant dier- ences between pellets and algae are indicated with * (Fisher's test, P 0.01).
with MC the maturity stage ranging from 1 to 8, n the MC Results number of individuals presenting that coecient, and ntot the total number of individuals in the batch. As no dierence There was a large discrepancy between the apparent and could be established between males and females in previous actual consumption of pellets (Fig. 2). This was owing to the studies on wild populations of P. lividus in Morgat (Spirlet disintegration of the pellets in sea water. Further, as sea et al. 1998b) and cultivated specimens (personal observa- urchins feed slowly, there may be additional losses during tions, v2 test, P < 0.05), data for the sexes were pooled in all grazing. All particles larger than 250 lm were collected in the analysis. drawers (see Fig. 1), and these losses would then be estima- In both experiments, the conditions and the eect of ted. There were no dierences in ingestion between pellet feeding were compared using one-way ANOVAs and Fisher's types, nor were there signi®cant dierences between the algae least signi®cant dierence tests (levels of signi®cance: types, in terms of ingestion rate, although dierences were P 0.05) after arcsine transformation for proportions recorded between pellets and algae. (Sokal & Rohlf 1981). A Mann±Whitney nonparametrical Being related to the actual ingestion rate (see equation 6), U-test was used for the GI (level of signi®cance: P 0.05) absorption rate is signi®cantly lower for the pellets than for and a Watson's U2-test was performed on the polar trans- the other foods, and also signi®cantly lower for Lessonia than formed values for MI (Zar 1996). for Laminaria. Hence, the absorption eciency is signi®cantly
Figure 3 Absorption and conversion eciencies with the four tested diets in the experimental aquaria. No signi®cant dierences were observed between pel- lets. Other signi®cant dierences are indicated with * (inferior to pellets) or (inferior to Laminaria) (Fisher's test, P 0.01).
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lower for the Lessonia than for the three remaining foods Lessonia does not grow. The ®nal results for the SG show no (Fig. 3). Lessonia results therefore in a lower SG rate signi®cant dierences and are comprised between 0.18 and (Fig. 2). The SG observed with pellets are not signi®cantly 0.39% day±1 individual±1. dierent than the one obtained with Laminaria. Figure 5 shows the evolution of GG. During the ®rst Finally, as a consequence of the large discrepancy between month, only the pellets promote GG. Although it is minor in apparent and actual ingestion rates of the pellets, the Conv absolute weight, it does represent a growth, respectively, 31% (one of the most important criteria from the point of view of (0.11% day±1 individual±1) for the individuals fed with MFP a commercial aquaculture activity) is very dierent if we and 47% (0.19% day±1 individual±1) for the individuals fed consider apparent or actual conversion ratio. They give with soya-bean pellets. There is no signi®cant dierences better results than Laminaria only in the second case. between treatments. After 2 months, gonads produced by sea Figure 4 shows the results for SG in the second experi- urchins fed with Laminaria are signi®cantly less than those ment. Somatic growth is measurable although relatively low fed with pellets. At the end of the experiment, the sea urchins during the ®rst month, between 0.14 and 0.46 g individual±1 with Lessonia treatment produced a measurable but very low corresponding to a weight increase between 0.30 and amount of gonad. The GG is similar for the other treatments. 0.41% day±1. There are no signi®cant dierences between Figure 6 shows the evolution of the GI. Individuals fed food types. In the second month, Laminaria promotes SG: with pellets have a signi®cantly higher GI than the others in we measured over 0.46% day±1. Only the batch fed with the ®rst month. The GI of the batch fed with Lessonia algae
Figure 4 Somatic growth depending on food treatment after 1, 2 and 3 months. Data are calculated in % day±1 indivi- dual±1. The unfed batch shows negative growth (loss of weight). MFP: Mixed- food pellets; SBP: soya-bean pellets; LAM: Laminaria; LES: Lessonia.
Figure 5 Gonadal growth (GG) depending on food treatment after 1, 2 and 3 months evaluated from the initial mean value of gonad weight. Data are calculated in % day±1 individual±1. The unfed batch, the ®rst two Lessonia fed batches and the ®rst Laminarian fed batch show negative growth (loss of weight). MFP: Mixed-food pellets; SBP: soya-bean pellets; LAM: Laminaria; LES: Lessonia.
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Figure 6 Gonad index (GI) expressed in percentage including the value for the initial batch. MFP: Mixed-food pellets; SBP: soya-bean pellets; LAM: Lamina- ria; LES: Lessonia.
remains very low through out the experiment. As it (dotted arrow), is signi®cantly higher the ®rst month (MFP increases, the GI of the individuals fed with Laminaria 1). After 2 months of treatment, gametogenesis is insigni®- algae remains signi®cantly lower than the GI of the ones fed cant in the Lessonia batch as opposed to that fed with with pellets. Laminaria (stage 3) and those fed with pellets which have For the maturity aspect (Fig. 7), during the ®rst month, reached stages 4 and 5 (Spirlet et al. 1998b). The dierences only the batch fed with MFP has started gametogenesis by are signi®cant. At the end of the experiment, the sea urchins means of multiplying the number of gametocytes (presence of fed with pellets have reached an MI close to 6 (mature) but stage 3 or recovery stage in the scale de®ned by Spirlet et al. the batches are actually composed of individuals presenting 1998b). Others are still in the spent stage. Except for the stages 5 (premature) and 7 (partly spawned). The batches fed Lessonia batch, all have accumulated nutrients in their with Lessonia and Laminaria algae have reached an MI nutritive phagocytes. The MI of the batch fed with MFP between 4 and 5. Thus, the gametogenic process is slower for
Figure 7 Polar representation of the maturity index (MI) for both parts of the experiment. The framed numbers represent the maturity stages. The numbers 1, 2 and 3 following the symbols correspond to 1, 2 or 3 months of treatment with Lessonia algae (LES), Laminaria algae (LAM), soya-bean pellets (SBP) or mixed-food pellets (MFP). The underlined data represent the results after 1 month of feeding. The dotted arrow shows the MI for the batch fed with mixed-food pellets, signi®cantly higher than the others after one month of treatment. The other arrows represent the MI for the batches fed with pellets, signi®cantly higher than the other two after 2 months of treatment.
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the Laminaria-fed individuals than for the pellet-fed ones. As somatic production could be owing to the very poor quality of for the Lessonia batch, gametogenesis proceeds only during food (in composition or in assimilation potential) consider- the third month of treatment. Furthermore, the aspect of the ably slowing the recovering process. Thus, after 1 month of gonads is very dierent: the diagnosis of the maturity stage is treatment, the individuals would only be starting to recover possible because the sexual cells are recognizable but they are the digestive functions. With Laminaria, the process seems to very few in a very light mesh of nutritive cells. be slightly quicker as there is SG but still no growth of the The compilation of these results indicates that the dry gonads, in the ®rst month. Other studies have shown growth Lessonia alga allows poor GG and SG after 3 months of of gonads in a few weeks' time (see Lawrence et al. 1991; treatment. Thus, the GI remains very low. The pellets promote notably for P. lividus and Klinger et al. 1997 for Strongylo- SG, GG and gametogenesis. Fresh Laminaria appears to give centrotus droebachiensis) in aquaria conditions but the spec- better SG and minor GG results over the same period. imens used were ®eld animals ®shed with empty gonads in autumn. Thus, the individuals' vital functions were not really disturbed by starving and no recovery was necessary. Discussion During a long starving period, the gonadal tissue is During the study, the pellets are readily consumed by the resorbed and the nutrients stored in the phagocytes are used echinoids. This might be because their texture and form is for maintenance (Lawrence & Lane 1982; Lares & Pomory convenient: easy to grab and manipulate with the minimum 1998). When fed later the echinoids recover their gonads ®rst eort. [Klinger (1982) discussed the importance of the shape by storing de novo nutrients in their phagocytes and then of the foods given to sea urchins.] Figure 2 shows that sea multiplying gametocytes that will eventually follow the urchins ingest more Laminaria than pellets. Fresh algae may gametogenic process. Relative latency in gonad maturation imply a greater energy in manipulation and in chewing as the during the ®rst month can be owing to the time necessary to volume to ingest is larger. recover from starvation. For similar GI and GG values, the As a reminder, we indicated our apparent values so that signi®cant dierence in maturity between the pellets suggests our results could be compared with other echinoid studies. that the mixed food might favour the multiplication of However, we insist on the necessity to correct those values. gametocytes and/or gametogenesis. Gonads of individuals Indeed, there is an inevitable weight variation of food in fed with Lessonia are similar to the starved individuals water. Therefore, apparent ingestion is not really represen- con®rming the inadequacy of this food. tative as it does not take this variation into account. As this Somatic growth, which was low during the ®rst month, correction is minor on the algae, it makes a drastic dierence becomes important during the second month and drastic at the for the pellets (Fig. 2). Thus, the sea urchins ingest much less third month: the sea urchins' somatic weight has increased pellets than Laminaria for the same SG, implying that the over 150% from the initial value (results not shown). Lessonia Conv is higher for the arti®cial food (Fig. 3). Degradation of is consumed as abundantly as Laminaria. However, SG is the pellets could also have implication in water pollution, lower in aquaria. In the structures, the SG occurs in the third especially in closed systems. month. As the food was distributed ad libitum and was Somatic growth is statistically equivalent for Laminaria consumed regularly, there is no reason a priori why important and pellet treatments both in the aquaria and in the rearing SG should occur so late. No such example was found in units. If SG is measurable and non-negligible, the GI can be literature. Results from this study suggest that Lessonia biased and not representative of gonadal production. There- promotes SG exclusively. In addition to lower conversion rate fore, the GG (in % day±1 individual±1) seemed a priori a and poor SG, it con®rms that dried Lessonia is not an accurate more accurate parameter to assess the production of roe. food for this species. The nutritive properties seem too low to Usually, the growth of the gonads is associated with the grow anything but skeleton. Bedding®eld & McClintock ingestion of nutrients (Lawrence & Lane 1982). In this (1998) showed that when Lytechinus variegatus was fed with experiment, Lessonia consumption did not promote GG. It Lessonia, the gut did not attain a level sucient to initiate the seems that feeding the echinoids with Lessonia (at least for a translocation of nutrients to the gonads. The lack of eciency short period after starving) promotes primarily SG if any. It is might be enhanced by the drying process as fresh Lessonia is a de®nitely impossible. Bishop & Watts (1992) showed in privileged food in south America for certain echinoid species Lytechinus variegatus that recovery of the vital functions was such as Loxechinus albus (Zamora & Stotz 1992). composed of two stages preceding the recovery of gameto- Results show that in 3 months growth is similar for all genic activity. The apparent direction of the nutrients towards treatments except Lessonia (Fig. 5). There are dierences in
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intermediate analysis. Thus, pellets enhance the production echinoid Lytechinus variegatus (Lamarck) fed natural diets. J. Exp. of gonadal tissue quicker than Laminaria. However, it is Mar. Biol. Ecol. 226, 195±215. Bishop, C.D. & Watts, S.A. (1992) Biochemical and morphometric unsure if it is from greater ingestion or better quality, or study of growth in the stomach and intestine of the echinoid both. The only reliable fact is that the GI is considerably Lytechinus variegatus (Echinodermata). Mar. Biol. 114, 459±467. higher (30%) than the maxima observed in the ®eld (Spirlet Byrne, M. (1990) Annual reproductive cycles of the commercial sea urchin Paracentrotus lividus from an exposed intertidal and a et al. 1998b). These results agree with those of Lawrence sheltered subtidal habitat on the west coast of Ireland. Mar. Biol. et al. (1997) for L. albus for which the GG was superior for 104, 275±289. the individuals fed with extruded feeds. The same should Caltagirone, A., Francour, P. & Fernandez, C. (1992) Formulation encourage the use of this type of food in cultivation, as it of an arti®cial diet for the rearing of the urchin Paracentrotus lividus: I. Comparison of dierent binding agents. In: Echinoderm seems to promote both SG and GG. Moreover, for the MFP Research (Scalera-Liaci, L. & Canicatti, C., eds.), pp. 115±119. treatment, the GG is similar between the second and third Balkema, Rotterdam. month, while for soya-bean pellets and Laminaria treatments, Fernandez, C. (1996) Croissance et nutrition de Paracentrotus lividus dans le cadre d'un projet aquacole avec alimentation arti®cielle. the growth is signi®cantly superior during the third month. PhD thesis, Universite de Corse, Faculte des sciences et techniques, We can suppose that the individuals fed with MFP reached Ecologie marine. maximal production during the second month. It would be Gayral, P. & Cosson, J. (1973) Expose synoptique des donne es biologiques sur la laminaire digite e Laminaria digitata. Fish interesting to know if after the fourth month of treatment (1) Synopsis FAO, 89, 45. the individuals fed with soya-bean pellets would have larger Grosjean, P., Spirlet, C., Gosselin, P., Vaitilingon, D. & Jangoux, M. gonads than the ones fed with MFP, and if (2) the individuals (1998) Land-based closed cycle echiniculture of Paracentrotus fed with Laminaria would have caught up with the others. lividus Lamarck (Echinodermata: Echinoidea): a long term experi- ment at a pilot scale. J. Shell®sh Res. 17, 1523±1531. The levels of production observed indicate that the Grosjean, P., Spirlet, C. & Jangoux, M. (1996) Experimental study of echinoids consumed sucient quantities of arti®cial feeds growth in the echinoid Paracentrotus lividus (Lamarck, 1816) to be well nourished. High production of somatic and (Echinodermata). J. Exp. Mar. Biol. Ecol. 201, 173±184. Grosjean, P., Spirlet, C. & Jangoux, M. (1999) Comparison of three gonadal tissues indicate that both feeds will support nutrient body-size measurements for echinoids. In: Proceedings of the 5th store even after a period of starvation, when nutrient European Echinoderm Conference (Candia Carnevali, M.D. & allocation can be diverted from gut to gonad production. Bonasoro, F., eds.), pp. 31±35. Balkema, Rotterdam. Haug, A. & Jensen, A. (1954) Seasonal variations on the Either food is sucient for maintenance of P. lividus and for chemical composition of Alaria esculenta, Laminaria saccharina, promoting both SG and GG. However, there are two main Laminaria hyperborea and Laminaria digitata from Northern drawbacks to the pellets in their present formulation. First, Norway. Reports of the Nowegian Institute of Seaweed the positive nutritional gain is partially overwhelmed by the Research, no. 4. Jensen, A. (1956) Component sugars of some common brown algae. substantial degradation of the food in sea-water and the lost Reports of the Nowegian Institute of Seaweed Research, no. 9. nutrient can cause water pollution in intensive cultivation. Klinger, T.S. (1982) Feeding rates of Lytechinus variegatus Lamarck Manufacturers need to improve their food in terms of (Echinodermata: Echinoidea) on diering physiograms of an arti®cial food uniform composition. In: International Echinoderms stability in sea-water in time. Conference, Tampa Bay (Lawrence, J.M., ed.), pp. 29±32. Balk- ema, Rotterdam. Klinger, T.S., Lawrence, J.M. & Lawrence, A.L. (1997) Gonad and Acknowledgements somatic production of Strongylocentrotus droebachiensis fed man- ufactured feeds. Bull. Aquacul. Assoc. Canada, 1, 35±37. We thank A. Rouillet for her help in the laboratory work. Klinger, T.S., Lawrence, J.M. & Lawrence, A.L. (1998) Digestion, We are grateful to J.M. Lawrence who supplied the arti®cial absorption, and assimilation of prepared feeds by echinoids. In: food. This research has been supported by a EC research Echinoderms: San Francisco, Proceedings of the 9th International Echinoderm Conference (Mooi, R. & Telford, M., eds.), pp. 887± grant attributed to C.SPIRLET (ref. ERB 4001 GT92 0223), 892. Balkema, Rotterdam. in the framework of the Sea Urchin Cultivation contract no. Lares, M.T. & Pomory, C.M. (1998) Use of body components during AQ 2.530 BFE (EC `FAIR' Research Program). This paper is starvation in Lytechinus variegatus (Lamarck) (Echinodermata: Echinoidea). J. Exp. Mar. Biol. Ecol. 225, 99±106. a contribution to the `Centre Interuniversitaire de Biologie Lawrence, J.M., Fenaux, L., Corre, M.C. & Lawrence, A. (1991) The Marine' (CIBIM). eect of quantity and quality of prepared diets on production in Paracentrotus lividus (Echinodermata: Echinoidea). In: Echino- derm Research (Scalera-Liaci, L. & Canicatti, C., eds.), pp. 107± References 110. Balkema, Rotterdam. Lawrence, J.M. & Lane, J.M. (1982) The utilization of nutrients by Bedding®eld, S.D. & McClintock, J.B. (1998) Dierential survivor- post-metamorphic echinoderms. In: Echinoderm Nutrition (Jan- ship, reproduction, growth and nutrient allocation in the regular goux, M. & Lawrence, J., eds.), pp. 331±371. Balkema, Rotterdam.
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Lawrence, J.M., Olave, S., Otaiza, R., Lawrence, A.L. & Bustos, E. Spirlet, C., Grosjean, P., Jangoux, M. (2000) Optimization of gonad (1997) Enhancement of gonad production in the sea urchin growth by manipulation of temperature and photoperiod in Loxechinus albus in Chile fed extruded feeds. J. World Aquacult. cultivated sea urchins, Paracentrotus lividus (Lamarck) (Echino- Soc. 28, 91±96. dermata). Aquaculture 185, 85±99. Le Gall, P. (1989) Echinoculture. In: Aquaculture. (Barnabe, G. (ed.), Zamora, S. & Stotz, W. (1992) Reproductive cycle of Loxechinus Vol. 1, pp. 468±491. Lavoisier, France. albus (Molina 1782) (Echinodermata: Echinoidea) at Punta Sokal, R.R. & Rohlf, F.J. (1981) Biometry (2nd edn.). Freeman and Lagunillas, IV Region, Coquimbo, Chile. Revista Chilena Historia Co., New York. Natural. 66, 155±169. Spirlet, C., Grosjean, P. & Jangoux, M. (1998a) Optimizing food Zar, J.H. (1996). Biostatistical Analysis (3rd edn.), Prentice Hall distribution in closed-circuit cultivation of edible sea-urchins International Ltd., London. (Paracentrotus lividus: Echinoidea). Aquat. Living Resour. 11, 273±277. Spirlet, C., Grosjean, P. & Jangoux, M. (1998b) Reproductive cycle of the echinoid Paracentrotus lividus: analysis by means of the maturity index. Invert. Reprod. Develop. 34, 69±81
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