Presence and distribution of FMRFamide‐like immunoreactivity in the cyprid of the barnacle Balanus amphitrite (Cirripedia, crustacea)

Abstract

The presence and distribution of FMRFamide-like peptides (FLPs) in the cyprid larvae of the barnacle Balanus amphitrite were investigated using immunohistochemical methods. Barnacles are considered to be one of the most important constituents of animal fouling communities, and the cyprid stage is specialized for settlement and metamorphosis in to the sessile adult condition. FLPs immunoreactive (IR) neuronal cell bodies were detected in both the central and the peripheral nervous system. One bilateral group of neurons somata was immunodetected in the brain, and IR nerve fibers were observed in the neuropil area and optic lobes. Intense immunostaining was also observed in the frontal filament complex: frontal filament tracts leaving the optic lobes and projecting towards the compound eyes, swollen nerve endings in the frontal filament vesicles, and thin nerve endings in the external frontal filament. Thin IR nerve fibers were also present in the cement glands. Two pairs of neuronal cell bodies were immunodetected in the posterior ganglion; some of their axons appear to project to the cirri. FLPs IR neuronal cell bodies were also localized in the wall of the dilated midgut and in the narrow hindgut; their processes surround the gut wall and allow gut neurons to synapse with one another. Our data demonstrated the presence of FLPs IR substances in the barnacle cyprid. We hypothesize that these peptides act as integrators in the central nervous system, perform neuromuscular functions for thoracic limbs, trigger intestinal movements and, at the level of the frontal filament, play a neurosecretory role.

Transcriptomic Analysis of Neuropeptides and Peptide Hormones in the Barnacle Balanus amphitrite: Evidence of Roles in Larval Settlement

“…The neuropeptide precursor sequences and predicted structures are listed in Table S2. In comparison with the previous studies in which only pigment dispersing hormone, crustacean cardioactive peptide and RFamide family had been characterized by immunohistochemistry [29], [30], [31], our results tremendously expand our knowledge of the molecular endocrinology of barnacle species.…”

“…trp (Tachykinin-related peptide) was down-regulated in cypris and early juvenile stage compared to naupliar and adult stages (Tukey test, p <0.05); irp (Insulin-related peptide) was down regulated in early juvenile compared to other stages ( p <0.05, One-way ANOVA); expression level of npf (neuropeptide F), burb (bursicon subunit β), calcib (B isoform of calcitonin-like diuresis hormone), orco (orcokinin), sulf (sulfakinin), eh (eclosion hormone), asta and astc (A- and C- type allatostatin) remained unchanged among naupliar VI, cypris, juvenile stages, but were down-regulated in adults. The down regulation of neuropeptide genes in adults could be due to the degenerated neural system since the central nervous system of adult barnacle is highly reduced in the sessile mode [29], [42]. There was, however, an exception, which is the high expression of tachykinin-related peptide ( trp ) in both naupliar VI and adult stages.…”

A review of FMRFamide- and RFamide-like peptides in metazoa

“…Using in silico analyses of ESTs, two NPFs have been identified in Marsupenaeus japonicus and Daphnia magna, (Gallus et al 2009). The actions of FLPs have been examined on a range of crustacean tissues in addition to the stomatogastric and cardiac ganglion circuits; and in general, they appear to be excitatory (Mercier et al 2003).…”

G‐protein alpha subunits distribution in the cyprid of Balanus amphitrite (=Amphibalanus amphitrite) (Cirripedia, Crustacea)

“…The anatomy of cyprids, in particular of the species Balanus amphitrite (=Amphibalanus amphitrite) (Clare and Høeg,2008; Darwin,1854; Walker,1992) and B. improvisus , has been accurately studied, paying special attention to the nervous system (Harrison and Sandeman,1999). The function of neuroactive substances was studied in barnacle cyprid and adult: dopamine (Kon‐Ya and Endo,1995; Okano et al,1996), serotonin (Callaway et al,1989; Gallus et al,2005; Yamamoto et al,1996), Choline Acetyl‐Transferase, AcetylCholine‐Esterase (Faimali et al,2003; Gallus et al,2006b), FMRFamide‐like peptides (FLPs) (Gallus et al,2009a, 2006a, 2001), γ‐aminobutyric acid (GABA) and GABAergic molecules (Callaway et al,1989; Gallus et al,2009b, 2010a, b). Recently, adrenergic molecules were proposed as antifouling (Elwing and Martensson,1999, United States Patent 6,762,227) and an octopamine receptor was cloned (Lind et al,2010) in B. improvisus to identify the targets of the settlement inhibitor medetomidine, an α2‐adrenoceptor agonist (Dahlström and Elwing,2006).…”