Monoamine content during the reproductive cycle of Perna perna depends on site of origin on the Atlantic Coast of Morocco

Abstract

Bivalve molluscs such as Perna perna display temporal cycles of reproduction that result from the complex interplay between endogenous and exogenous signals. The monoamines serotonin, dopamine and noradrenaline represent possible endocrine and neuronal links between these signals allowing the molluscs to modulate reproductive functions in conjunction with environmental constraints. Here, we report a disruption of the reproductive cycle of mussels collected from two of three sites along the Moroccan atlantic coast soiled by industrial or domestic waste. Using high pressure liquid chromatography, we show that the temporal pattern of monoamine content in the gonads, pedal and cerebroid ganglia varied throughout the reproductive cycle (resting, developing, maturing, egg-laying) of mussels from the unpolluted site. Marked modification of monoamine tissue content was found between sites, notably in noradrenaline content of the gonads. Discriminant statistics revealed a specific impact of mussel location on the temporal variations of noradrenaline and serotonin levels in gonads and cerebroid ganglia. Correlation analyses showed profound and temporal changes in the monoamine content between organs and ganglia, at the two sites where the reproduction was disrupted. We suggest that environmental constraints lead to profound changes of monoaminergic systems, which thereby compromises the entry of mussels into their reproductive cycle.

Structure-Function of Serotonin in Bivalve Molluscs

“…Results confirm aforementioned differences in 5-HT content among various parts of the nervous system, for instance it is higher in the CG than the VG of gaper clam (Tresus capax) and bent-nose clam (Macoma nasuta) [117]. In addition, the metabolite of 5-HT (5-HIAA) is detected in the nervous system of the brown mussel (Perna perna) [110] and Atlantic deep-sea scallop [114], suggesting that metabolism of 5-HT takes place in the nervous system.…”

“…As the blue mussel spawns from late spring to late summer [129,130], these data suggest that 5-HT content increases during spawning. 5-HT content also correlates with the content of its metabolite (5-HIAA), suggesting that metabolism of 5-HT is in parallel to its biosynthesis in the nervous system [110].…”

“…Further studies have shown that 5-HT content in the nervous system undergoes seasonal variation along with gonadal development in bivalves ( Table 2). Content of 5-HT increases in the nervous system from early gonadal development to maturity stage in the brown mussel [110] and decreases following spawning in Peruvian scallop (Argopecten purpuratus) [113]. York and Twarog [120] reported that 5-HT in the PG of blue mussel is higher in April than March.…”

“…Using spectrofluorometric or HPLC-EC method, 5-HT content has been measured in the gonad of the Atlantic deep-sea scallop [114,115], surf clam [112], Pacific lion's paw scallop (Nodipecten subnodosus) [111], and brown mussel [110]. Matsutani [131] reported a tendency toward an increase and a decrease of 5-HT content in the testis and ovary of Japanese scallop (Chlamys farreri nipponensis) during spawning, respectively.…”

“…Studies used spectrofluorometric method [26,47,56,[118][119][120] or electrochemical detection coupled with a high-performance liquid chromatography (HPLC-EC) to study 5-HT content in the nervous system of bivalves [90,110,114,115,117] ( Table 2). Results confirm aforementioned differences in 5-HT content among various parts of the nervous system, for instance it is higher in the CG than the VG of gaper clam (Tresus capax) and bent-nose clam (Macoma nasuta) [117].…”