ICES Journal of Marine Science, 62: 886e896 (2005) doi:10.1016/j.icesjms.2005.02.010 Energy storage and utilization in relation to the reproductive cycle in the razor clam Ensis arcuatus (Jeffreys, 1865) Susana Darriba, Fuencisla San Juan, and Alejandro Guerra Downloaded from https://academic.oup.com/icesjms/article/62/5/886/856445 by guest on 29 September 2021 Darriba, S., San Juan, F., and Guerra, A. 2005. Energy storage and utilization in relation to the reproductive cycle in the razor clam Ensis arcuatus (Jeffreys, 1865). e ICES Journal of Marine Science, 62: 886e896. Seasonal changes in condition indices and biochemical components of the digestive gland, anterior adductor muscle, foot, and gonad of Ensis arcuatus (Jeffreys, 1865) were analysed from February 1998 to June 1999 in relation to environmental conditions and reproductive events. During summer, E. arcuatus accumulated lipids, particularly triacylglycerols, in the digestive gland and glycogen in the anterior adductor muscle and foot while the gonad was in sexual rest. Phytoplankton blooms caused by the upwelling of cold waters, rich in nutrients, from offshore are responsible for the high availability of food during reserve storage. In autumn, when gametogenesis started, oceanographic conditions changed to a situation with low temperature throughout the water column because of the vertical mixing, and food became scarce. At that point in time, the energy requirements for basal metabolism and the reproductive process were provided by the mobilization of triacylglycerols and glycogen stored in the digestive gland and muscle tissues, respectively. The pattern exhibited by E. arcuatus based on the accumulation of reserves in summer and the subsequent mobilization during gonadal development seems to follow a conservative pattern. Ó 2005 International Council for the Exploration of the Sea. Published by Elsevier Ltd. All rights reserved. Keywords: carbohydrates, chlorophyll, condition indices, Ensis arcuatus, gametogenesis, temperature, total proteins, triacylglycerols. Received 5 February 2004; accepted 20 February 2005. S. Darriba, and A. Guerra: Centro de Investigacio´ns Marin˜as, Consellerı´a de Pesca e Asuntos Marı´timos, Xunta de Galicia, Aptdo n( 13, 36620 Vilanova de Arousa, Pontevedra, Spain. F. San Juan: Facultade de Ciencias do Mar, Universidade de Vigo, Campus Lagoas- Marcosende 36200 Vigo, Spain. Correspondence to S. Darriba: tel:C34 986500155; fax: C34 986506788; e-mail: [email protected]. Introduction (Ansell, 1974; Gabbott, 1975; Barber and Blake, 1983; Pazos et al., 1997). Reproduction, on the other hand, is Seasonal variations in the metabolic activities of marine influenced by environmental conditions (Barber and Blake, bivalves reflect the complex interactions between the 1981; MacDonald and Thompson, 1985) and by genetic available food, environmental conditions, and reproductive characteristics (Barber and Blake, 1991) that determine activity. This is demonstrated in several papers on different differences between species and between populations of the species of the families Mytilidae (Waldock and Holland, same species. 1979; Emmett et al., 1987; Jaramillo and Navarro, 1995), In marine invertebrates, the energy storage and gonad Ostreidae (Mann, 1979; Ferna´ndez-Castro and De Vido-De development cycles may occur simultaneously or they may Mattio, 1987; Ruiz, 1992; Ruiz et al., 1992a, b; Rosique be clearly separated (Bayne, 1976). The relationship between et al., 1995), Cardiidae (Newell and Bayne, 1980; Navarro the two cycles defines the reproductive pattern of the species. et al., 1989), Veneridae (Adachi, 1979; Beninger and So, in a conservative pattern, gametogenesis takes place at Lucas, 1984), Pectinidae (Taylor and Venn, 1979; Barber the expense of energy stored in some body tissues, while in an and Blake, 1981; Lubet et al., 1987a, b; Epp et al., 1988; opportunistic pattern gametogenesis occurs when the avail- Pazos, 1993; Roma´n et al., 1996; Pazos et al., 1996, 1997), ability of food in the water is plentiful enough to support the and Arcidae (Galap et al., 1997). energy required by the process. The energy required to carry out the gametogenic process Ensis arcuatus is the most important species of Solenidae can be covered by using directly ingested food or the in Spain and its commercial value has increased recently. In previous storage of reserves in the gonad or other tissues contrast to other bivalve molluscs, there are only few 1054-3139/$30.00 Ó 2005 International Council for the Exploration of the Sea. Published by Elsevier Ltd. All rights reserved. Energy storage and utilization in Ensis arcuatus 887 publications on the Solenidae family despite the economic the biochemical analyses of total proteins, total lipids, interest in this species. The objective of the work was to triacylglycerols, glycogen, and free glucose. study energy storage in different body tissues of Total proteins were determined according to Lowry et al. E. arcuatus, its relation to the gametogenic cycle, and to (1951). The samples had been previously deproteinized by describe the reproductive pattern of the species. dilution in 12% perchloric acid (PCA), at a 1:4.5 ratio (w:v) for soft tissues and at a 1:7.5 ratio for hard tissues. Proteins were collected in the precipitate after centrifugation at 7800 rpm, and resuspended with 10 ml of 1 N NaOH in Material and methods a bath at 40(C for 1 h, then diluted with distilled water for Measurements of body parts the determination. Downloaded from https://academic.oup.com/icesjms/article/62/5/886/856445 by guest on 29 September 2021 and histological analysis Lipid extraction was done according to the method of Folch et al. (1957), as modified by Beninger and Lucas Twenty adult specimens of Ensis arcuatus were collected, (1984). The quantification of total lipids was determined approximately every 2 weeks, from the natural bed of the using spectrophotometric methods in relation to Tri- Cı´es Islands (Rı´a de Vigo e Northwest Spain) (Figure 1) estearine, after acid hydrolysis, according to Marsh and from February 1998 to June 1999. Samples were taken by Weinstein (1966). professional ‘‘apnea’’ divers who harvest this resource on For the quantification of triacylglycerols the method of a daily basis. After collection, the samples were transported Wahlefeld (1974) was followed and consisted of the to the laboratory covered with damp cloths and placed in enzymatic hydrolysis of triacylglycerols with the subsequent a portable fridge to be processed after 24 h. determination of liberated glycerol by colorimetry (kit Each specimen was measured to record the following Triglycerides GPO-PAP 701912 e Boehringer Mannheim). parameters: total length, total weight, shell dry weight, Carbohydrates (glycogen and free glucose) were ana- anterior adductor muscle fresh weight, foot fresh weight, lysed by the method of Keppler and Decker (1984), and gonad fresh weight. modified by Crespo (1989), after the deproteinization of the Dissection of the tissues was carried out in vivo, each sample by precipitation with PCA as described earlier. The tissue being placed on a filter paper to drain the excess method was based on enzymatic hydrolysis of glycogen of water, then weighed (fresh weight). Next, they were with the amyloglucosidase enzyme. Next, the glucose was immediately frozen in liquid nitrogen and stored at ÿ80(C oxidized by glucose-oxidase to gluconate and hydrogen until analysis. The shells were weighed after 3 h at 60(C. peroxide, which reacts with phenol to produce quinonimine, Condition indices of each dissected tissue were calculated and which is detectable by spectrophotometry (kit glucose using the formula tissue fresh weight/shell dry weight. GOD-PAP/Trinder e Spinreact). Each specimen was examined histologically to determine All determinations were done in triplicate, applying the sex and the gametogenic stage according to the scale average value to the graphic representations. defined for E. arcuatus by Darriba et al. (2004), based on seven stages: (0) sexual rest, (I) start of gametogenesis, (II) advanced gametogenesis, (IIIA) ripe, (IIIB) start of Environmental parameters spawning, (IIIC) restoration, and (IV) exhaustion. The Centro de Control do Medio Marin˜o (CCMM) recorded temperature and chlorophyll a concentration of the water column at a point located in the Rı´a de Vigo Biochemical analyses (42(13#75$N8(52#20$W) on a weekly basis. Values e e e For each sample, we pooled tissues of specimens of the referred to depth ranges of 0 5, 5 10, and 10 15 m. same sex and gametogenic stage. The use of pooled tissue Temperature was measured using a CTD temperature of many individuals to determine the average biochemical sensor and chlorophyll by spectrofluorometry. composition was recommended by Giese (1966) and Giese et al. (1967). Statistical analysis e ( Each pool obtained was homogenized, at 0 4 C, in Statistical analyses were performed using the statistical e a buffer (40 mM Tris HCl buffer, pH 7, 0.12 M KCl) with package SPSS for Windows, version 9.0.1, applying the a 1:2 ratio (weight:volume) for the gonad and digestive ManneWhitney U-test. gland and 1:4 ratio for muscle tissues (anterior adductor muscle and foot). Different homogenizing techniques were used: soft tissues (gonad and digestive gland) were Results homogenized at 2000e2500 rpm with a Tri-R homogenizer (Tri-R Stir-R model 43), and hard tissues (anterior adductor Environmental parameters muscle and foot) were homogenized at 15000 rpm with Figure 2a shows temperature data in three depth ranges a Tempest IQ squared homogenizer (Virtix). The homo- during the sampling period. From January to May 1998 genate obtained was frozen at ÿ80(C in 1 ml aliquots for temperature was similar at all depths, ranging between 888 S. Darriba et al. Downloaded from https://academic.oup.com/icesjms/article/62/5/886/856445 by guest on 29 September 2021 Figure 1. Location of the natural bed of Ensis arcuatus. The left arrow signifies the Cı´es Islands at the mouth of the Rı´a de Vigo. 14(C and 15(C, which would indicate a vertical mixing of onwards, vertical mixing re-occurred and the temperature the water column.