Barnacle biology before, during and after settlement and metamorphosis: a study of the interface

Abstract

Mobile barnacle cypris larvae settle and metamorphose, transitioning to sessile juveniles with morphology and growth similar to that of adults. Because biofilms exist on immersed surfaces on which they attach, barnacles must interact with bacteria during initial attachment and subsequent growth. The objective of this study was to characterize the developing interface of the barnacle and substratum during this key developmental transition to inform potential mechanisms that promote attachment. The interface was characterized using confocal microscopy and fluorescent dyes to identify morphological and chemical changes to the interface and the status of bacteria present as a function of barnacle developmental stage. Staining revealed patchy material containing proteins and nucleic acids, reactive oxygen species amidst developing cuticle, and changes in bacteria viability at the developing interface. We found that as barnacles metamorphose from the cyprid to juvenile stage, proteinaceous materials with the appearance of coagulated liquid were released into and remained at the interface. It stained positive for proteins, including phosphoprotein, as well as nucleic acids. Regions of the developing cuticle and the patchy material itself stained for reactive oxygen species. Bacteria were absent until the cyprid was firmly attached, but populations died as barnacle development progressed. The oxidative environment may contribute to the cytotoxicity observed for bacteria and has the potential for oxidative crosslinking of cuticle and proteinaceous materials at the interface.

Hypothesis Testing With Proteomics: A Case Study Using Wound Healing Mechanisms in Fluids Associated With Barnacle Glue

“…Barnacle secretions and hemolymph associated with cuticle expansion during molting must manage the same issues as in other arthropods, which is to harden new cuticle and kill microbes. As in all crustaceans, wounding is an inherent part of barnacle molting and growth and leaking of fluids between the base and the surface occurs (Bourget and Crisp, 1975;Crisp and Bourget, 1985;Burden et al, 2012Burden et al, , 2014Essock-Burns et al, 2017). Barnacle fluid deposition is spatiotemporally dynamic and related to growth and molting.…”

“…Barnacle fluid deposition is spatiotemporally dynamic and related to growth and molting. First a cyprid adhesive is secreted via antennules in a bi-phasic system of lipids and proteins, some of which are phosphorylated (Walker, 1971(Walker, , 1973Gohad et al, 2014), followed by complex biopolymeric materials associated with reactive oxygen species during the metamorphic molt (Essock-Burns et al, 2017). As juveniles and adults molt and grow, several distinct proteinaceous materials are released (Burden et al, 2012).…”

“…Using precursor material collected from the periphery of barnacle bases, two enzymes, trypsin-like serine protease and transglutaminase, were isolated and characterized to participate in barnacle glue curing. Concurrent with a release of proteinaceous fluids under the cuticle during settlement and metamorphosis, reactive oxygen species are present, and contribute to observed antimicrobial activity (Essock-Burns et al, 2017;Fears et al, 2018). The ability to study glue curing as barnacle larvae undergo the metamorphic transition to the adult form and as they continue to grow and adhere, is a strength to this system of study.…”

Acorn Barnacles Secrete Phase‐Separating Fluid to Clear Surfaces Ahead of Cement Deposition

“…A lipidaceous fluid accumulates at the leading edge, and infuses with the cuticle (Figure 2h,i). After the infused portion is exposed to ASW, the fluid phase separates into a nonlabeled phase, and a phase rich in lipids and reactive oxygen species (Figure 4c; Videos S1–S5, Supporting Information)—the latter of which have been shown to exhibit broad spectrum antimicrobial activity 15, 36. Organic matter within 10 µm of this secretion positively stains for reactive carbonyl species, indicating oxidation has occurred (Figure 4d).…”

Off the Shelf Fouling Management

“…They share biochemical parts, equipment, and pathways. For example, barnacles and humans, separated by about a billion years of evolution, share active sites of enzymes, sequences of proteins, hormones, neurotransmitters, and immune system components [9,33,34,35,36,37,38,39,40,41]. …”