Bivalves hold an important role in marine aquaculture and the identification of growth-related genes in bivalves could contribute to a better understanding of the mechanism governing their growth, which may benefit high-yielding bivalve breeding. Somatostatin receptor (SSTR) is a conserved negative regulator of growth in vertebrates. Although
SSTR genes have been identified in invertebrates, their involvement in growth regulation remains unclear. Here, we identified seven
SSTRs (
PySSTRs) in the Yesso scallop,
Patinopecten yessoensis, which is an economically important bivalve cultured in East Asia. Among the three
PySSTRs (
PySSTR-1,
-2, and
-3) expressed in adult tissues,
PySSTR-1 showed significantly lower expression in fast-growing scallops than in slow-growing scallops. Then, the function of this gene in growth regulation was evaluated in dwarf surf clams (
Mulinia lateralis), a potential model bivalve cultured in the lab, via RNA interference (RNAi) through feeding the clams
Escherichia coli containing plasmids expressing double-stranded RNAs (dsRNAs) targeting
MlSSTR-1. Suppressing the expression of
MlSSTR-1, the homolog of
PySSTR-1 in
M. lateralis, resulted in a significant increase in shell length, shell width, shell height, soft tissue weight, and muscle weight by 20%, 22%, 20%, 79%, and 92%, respectively. A transcriptome analysis indicated that the up-regulated genes after
MlSSTR-1 expression inhibition were significantly enriched in the fat digestion and absorption pathway and the insulin pathway. In summary, we systemically identified the
SSTR genes in
P. yessoensis and revealed the growth-inhibitory role of
SSTR-1 in bivalves. This study indicates the conserved function of somatostatin signaling in growth regulation, and ingesting dsRNA-expressing bacteria is a useful way to verify gene function in bivalves.
SSTR-1 is a candidate target for gene editing in bivalves to promote growth and could be used in the breeding of fast-growing bivalves.
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