Distribution of Domoic Acid in the Digestive Gland of the King Scallop Pecten maximus

Abstract

The king scallop Pecten maximus retains the amnesic shellfish poisoning toxin, domoic acid (DA), for a long time. Most of the toxin is accumulated in the digestive gland, but this organ contains several cell types whose contribution to the accumulation of the toxin is unknown. Determining the time-course of the depuration by analyzing whole organs is difficult because the inter-individual variability is high. A sampling method, using biopsies of the digestive gland, has been developed. This method allows for repetitive sampling of the same scallop, but the representativeness of the samples obtained in this way needs to be validated. In this work, we found that the distribution of DA in the digestive gland of the scallops is mostly homogeneous. Only the area closest to the gonad, and especially its outer portion, had a lower concentration than the other ones, probably due to a transfer of the toxin to the intestinal loop. Samples obtained by biopsies can therefore be considered to be representative. Most of the toxin was accumulated in large cells (mostly digestive cells), which could be due to differences during the toxin absorption or to the preferential depuration of the toxin from the small cells (mostly secretory).

Transcriptional Response in the Digestive Gland of the King Scallop (Pecten maximus) After the Injection of Domoic Acid

“…Several authors have shown [ 14 , 15 , 16 ] that the digestive gland in the king scallop P. maximus accumulates most of the domoic acid. This agrees with the results obtained in the present work that found that domoic acid content in the digestive gland accounts for 84% of the total domoic acid burden in the body tissues of P. maximus ( Table 1 ).…”

“…The digestive gland of Pecten maximus contains principally two types of cells, secretory cells and digestive cells [ 16 , 40 , 76 , 77 ]. Vesicle-mediated transport and regulated exocytosis were enriched biological processes identified in protein networks obtained with the up-regulated genes ( Figure 2 and Supplementary File S8 ), therefore the activity of secretory cells in the digestive gland may be stimulated by domoic acid.…”

“…In the digestive gland of P. maximus , domoic acid was found to be present in the cytosol in soluble form [ 21 ], therefore Mauriz and Blanco [ 21 ] suggested that the lack of an efficient membrane transporter could be the cause of the low depuration rate. In a recent work, Blanco et al [ 16 ] showed that this toxin, in the digestive gland, is mainly accumulated in large cells (digestive cells) and the concentration was lower in small cells (secretory cells).…”

“…Unlike mussels and oysters [10][11][12][13], with high domoic acid depuration rates, in the king scallop (Pecten maximus) the depuration rate of domoic acid is very low [14,15]. Due to the blooms of domoic acid-producing species of the genus Pseudo-nitzschia and the low depuration rate of P. maximus [14,15], the domoic acid concentration in this scallop is usually above the regulatory limits (20 µg of domoic acid g −1 ) in many areas [16]. There are other scallop species (Placopecten magellanicus and Argopecten purpuratus) that do not show this slow domoic acid depuration [17,18].…”

First Report of Domoic Acid Production from Pseudo-nitzschia multistriata in Paracas Bay (Peru)

“…Recently, these toxic outbreaks have been reported in the United States from 2015 to 2016, affecting the fisheries of the razor clam (Siliqua patula), Dungeness crab (Metacarcinus magister) and rock crabs (Cancer productus, Metacarcinus anthonyi and Romaleon antennarium) [3,[24][25][26]. Likewise, in Europe, the DA-producing diatoms of genus Pseudo-nitzschia have led to bans on harvesting the natural populations of the king scallop Pecten maximus, and to the discouragement of aquaculture efforts for this species [27,28], due to its high capability to retain the toxin [29,30].…”