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Sessility of barnacles

Sessility is the property of an organism to remain attached to a substance. Barnacles can live in a single spot for the entirety of their lives. The benefits of sessility are self-protection and a stable environment for filter-feeding but what happens when barnacles exist where they should not? Many ships are plagued by barnacles on their hulls that cause the ships to increase fuel consumption up by 86%. So how do barnacles adhere to a single spot and remain there for the entirety of their lives? Barnacle adhesion was studied by Nick Aldred et al. and focused on observing the cement glands of barnacles that secretes the adhesive that allows for sessility. Nick Aldred et al. hypothesized that because chitin is an integral component of the adhesive used by barnacles, then degrading chitin should affect the integrity of the adhesive.

 

Figure 1: Imaging of cyprids showing cement glands, protein content, lipid content, and chitin.

Figure 1, provided by the study by Nick Aldred et al., shows the imaging of a cyprid and its cement glands. The cement glands are epithelial, chitin is shown as red, lipid content is shown as yellow, and protein content is shown as green. Parts h and i show cement deposited onto a surface and the presence of proteins, chitin, and lipids are shown.  The study incorporated using cyprids, juveniles, and mature adults to observe the effects of introducing chitinase on adhesion. Chitinase was found to cause detachment of cyprids but not in the other forms. This results means that chitin is an integral part of barnacle adhesion and chitinase can be used to degrade the adhesive used by barnacles. The cement glands were also analyzed by gel electrophoresis to isolate the chitin-protein complex and the chitin-protein was analyzed using mass spectroscopy.

While chitin has been found to be a key component for barnacle adhesion, the exact function of the adhesive protein complex remains unknown and remains a topic for further study. This research can also be used to further the development of adhesives, as well as the removal of the barnacle plague from ships. Finding the perfect adhesive that has strong bonding strength but is also easily removable could change how society develops structures. 

 

Aldred, N., Chan, V.B.S., Emami, K. et al. Chitin is a functional component of the larval adhesive of barnacles. Commun Biol 331 (2020). https://doi.org/10.1038/s42003-020-0751-5

https://www.nature.com/articles/s42003-020-0751-5

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Living in a single spot with cement

One of the most unique traits of acorn barnacles is their simple lifestyle through sessility. Sessility is the permanent attachment of an organism to a surface. The life of an acorn barnacle starts from a free-moving larval stage and ends as a sessile adult. But how is sessility achieved? At some point in their lives, late-stage cyprid larvas use cement glands to achieve sessility. 

The figure above shows the location of cement glands (c.g.) in a cyprid larva. These cement glands originate from the epithelial layer and are composed of α-cells and β-cells. α-cells are protein-based and β-cells are lipid-based. The secretion from these cells forms a protein-lipid substance that is used for adhesion to surfaces. Much is unknown about the chemistry about adhesion and cohesion but understanding this method of adhesion could further technologies for natural safe adhesives. 

A study was performed by Nick Aldred et al. to understand the composition of the cement produced by the cement glands. In the study, cyprid larvae were allowed to adhere to a surface using their cement. After a period of time, chitinase (an enzyme that denatures chitin) was introduced to the subjects and detachment of all cyprid larvae occurred after 8 hours. The study concluded that a key component of the cement produced by cyprid larvae is chitin, the same component used for the exoskeleton of Arthropods. Chitin does not exist purely in nature but is more commonly found as a chitin-protein complex. Understanding this complex seems to be key to understanding the cement that can allow for acorn barnacles to remain sessile for most of their lifetime.

 

Citation:

Aldred, N., Chan, V.B.S., Emami, K. et al. Chitin is a functional component of the larval adhesive of barnacles. Commun Biol 331 (2020). https://doi.org/10.1038/s42003-020-0751-5

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Inside Acorns?

I was laying in my bed and all of a sudden, the pitter-patter of feet sounded from my ceiling. It’s those squirrels again… Why can’t they leave me alone??? If only they didn’t just wake up from hibernation. If only they didn’t like to sleep in houses. If only they didn’t eat acorns. Why do they eat acorns anyway? Acorns are relatively simple: shells, kernels, and whatnot. Acorn barnacles, however, are much more complex. 

 

Figure 1: Anatomy of acorn barnacle highlighting female gonads

The figure above shows the anatomy of an acorn barnacle. The mantle, formed from the body wall, can be seen as the outer fleshy layer that makes that the shell. Not only does the shell protect the main body but the mantle cavity also serves to cushion the main body by allowing for space for the main body to move during impacts. While acorn barnacles are hermaphroditic, having both male and female genitalia, the figure displays only the female gonads, the ovaries, because the study, that the figure is from, focuses on the female reproductive system on barnacles. Cement glands connect to the inner canals to allow for the deposition of cement from the base plate to the substrate. The cirri, tentacle-like structures above the main body, are used for feeding.   

From an evolutionary standpoint, these anatomical features derived for specific purposes. Acorn barnacles are soft body and the hard shell does a great job protecting that soft body. This hardshell feature is common among relatives, such as those from the Crustacea subphyla. The hermaphroditic feature of acorn barnacles allows for the species to find mates easier and is also a common trait for close relatives. The cement glands allow for acorn barnacles to be sessile, remain in one spot for the majority of their lives, and is a common trait among order Sessilia. The cirri are used for filter-feeding food, such as plankton, and is a common trait among infraclass Cirripedia. While acorn barnacles do possess similar features to their relatives, they are more complex than simple acorns. 

Citation:

Wang, Chenyue⨯ Janna N SchultzhausTaitt, Chris RLeary, Dagmar HShriver-Lake, Lisa C; et al.PLoS One; San Francisco Vol. 13, Iss. 12,  (Dec 2018): e0208352. DOI:10.1371/journal.pone.0208352

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Giant Acorn Barnacles

Walking in a street with trees, you step on something. It’s an acorn and the crushed bits have gotten into all the grooves of your shoe. Taking a minute to brush your shoe off, your mind starts to wander and ponder on the most meaningful question of life, “are there other acorns out there?” Certainly, there must be other acorns because there are many types of trees and not all trees produce the same shaped acorns or produce acorns for that matter. But you really wonder… are there other acorns out there?

Well look no further, the giant acorn barnacles are here! Giant acorn barnacles, balinus nubilus, are the new acorns of the future! Sure normal acorns can grow trees but giant acorn barnacles’ claim to fame is that their max growth can reach 15 cm in diameter and 30 cm in height, roughly the size of a softball. That size is the largest of any known barnacle species! Have you ever seen a softball-sized normal acorn? I think not! Throughout the semester, I will be following and learning new things about these creatures but let’s get started on getting to know them better.

Giant acorn barnacles are a species of crustaceans in class Maxillopoda, subclass Cirripedia, which includes many other types of barnacles. Barnacles start off their life the same as many other crustaceans where they are free swimmers and later reside on a single spot, such as rocks, piers, or even hard-shelled animals. After determining that special spot, giant acorn barnacles create a limestone shell of calcium carbonate. They possess cement glands that cause the shells to be impossible to remove even after death. This particular species of barnacles live along the coast from Southern Alaska all the way to California. Following these species throughout the semester should prove more exciting than following some simple acorns.

 

citations:

Bailey, Regina. Acorn Barnacle Facts. Thoughtco. Retrieved February 1, 2020 from https://www.thoughtco.com/acorn-barnacles-4772301

Richard, Martin (1997). “View from on top: mine’s bigger than yours!”WaveLength Magazine. Archived from the original on March 3, 2016. Retrieved February 2, 2020.

 

 

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