The roles and the fate of the larval nervous system of the marine bryozoan bugula neritina

Abstract

The bryozoan Bugula neritina is a cosmopolitan marine fouling organism. Unlike the majority of fouling organisms, induction of larval settlement of B. neritina does not require any chemical cues. Furthermore, B. neritina has received a substantial amount of research attention and is a good model for studies of morphogenesis and evolutionary history. Previous studies demonstrated that different neurotransmitters can be either inductive or inhibitive to larval settlement of B. neritina, highlighting the role of larval nervous system in the process of larval settlement. In the present thesis study, we examined the larval nervous system of B. neritina by immunostaining the neurotransmitter serotonin and acetylated α-tubulin and captured the changes of its nervous system through settlement from free-swimming larvae to the juvenile stage. The results provided the evidence for the involvement of larval nervous system in larval settlement and showed that the larval nervous system was largely reduced or even completely abolished during the metamorphosis process. Nervous system regulates the endocrine system to control the body function by processing signals. The neuropeptides and hormones, as the major intercellular messengers in nervous and endocrine systems, may play a key role in mediating larval settlement of marine invertebrates. To investigate the roles of the neuronal signals underlying larval settlement of B. neritina, neuropeptides and peptide hormones were extracted from a transcriptome database by insilico prediction. Subsequently, the predicted genes were further confirmed by Rapid Amplification of cDNA Ends and their potential functions were investigated using in situ hybridization technology. As a result, 22 transcripts encompassing 15 neuropeptide precursor sequences were discovered, generating 34 deduced mature peptides. We confirmed the expression of 11 neuropeptide precursors by gene cloning, while 4 of them which exhibited clear homology to known neuropeptides could not be isolated by cloning experiment. We have also examined the gene expression of 4 neuropeptide genes (FDSIG, INS1, GPB and 7B2) in the coronate larvae of B. neritina and the results indicated their potential involvement in the larval settlement. Overall, this study provided significant insight into the role and fate of larval nervous system of B. neritina.

Date of Award	2016
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology