{"id":885,"date":"2016-05-25T20:02:08","date_gmt":"2016-05-26T03:02:08","guid":{"rendered":"https:\/\/sites.evergreen.edu\/vms-spring\/?p=885"},"modified":"2016-06-07T14:01:45","modified_gmt":"2016-06-07T21:01:45","slug":"semibalanus-balanoides","status":"publish","type":"post","link":"https:\/\/sites.evergreen.edu\/vms-spring\/semibalanus-balanoides\/","title":{"rendered":"Semibalanus Balanoides"},"content":{"rendered":"
\"barnaclestipple\"

Acorn barnacles can reach up to 15 mm. in diameter<\/p><\/div>\n

ACORN BARNACLE<\/h2>\n

<\/p>\n

 <\/p>\n

Scientific name: Semibalanus balanoides<\/em><\/span><\/p>\n

Kingdom: Animalia<\/span><\/p>\n

Phylum: Arthropoda<\/span><\/p>\n

Class: Maxillopoda<\/span><\/p>\n

Order: Sessilia<\/span><\/p>\n

GENERAL INFORMATION:<\/strong> \u00a0 \u00a0 \u00a0\u00a0<\/span><\/p>\n

The acorn barnacle is a common and widespread intertidal organism that can be <\/span>up to 15 millimeters in diameter (White, 2008). The barnacle starts out as a <\/span>nauplius, a <\/span>free-swimming larva hatched from a fertilized egg. It goes through five different stages of growth over 6 <\/span>months. It <\/span>eventually evolves into the cyprid larvalstage. The cyprid\u2019s goal is to find a place to find a suitable place to <\/span>spend the rest <\/span>of it\u2019s life, since the adult barnacle is sessile. The time it takes to find this place varies, but once it is\u00a0<\/span>found, the cyprid <\/span>glues it\u2019s head to it\u2019s new home. The barnacle, now a juvenile, starts the process of forming\u00a0<\/span>six <\/span>hard plates around <\/span>it\u2019s body (Fish, 1996). Once this process is complete and the barnacle reaches sexual maturity, the\u00a0<\/span>barnacle is <\/span>finally an adult. This <\/span>usually takes 1-2 years. The acorn barnacle uses it\u2019s cirri (feet) to capture it\u2019s food\u00a0<\/span>through a small <\/span>opening in the top of <\/span>it\u2019s outer shell. The barnacle has valves it can use to seal off this small hole, which\u00a0<\/span>serves as <\/span>protection from <\/span>predators(White, 2008). During winter<\/span>, barnacles do not feed and rely solely on reserves\u00a0<\/span>(White, 2008).<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span> Acorn barnacles are common and exist all over the world. This species is most commonly found in<\/span><\/p>\n

the upper mid <\/span>intertidal zone (Fish, 1996). Since they use their cirri to absorb oxygen, acorn barnacles<\/span><\/p>\n

can extract oxygen from both\u00a0<\/span>water and <\/span>air, making them extremely adaptable. You can often identify<\/span><\/p>\n

acorn barnacles habitat by the grayish-white\u00a0<\/span>\u201cbarnacle <\/span>zone\u201d found on coasts. It is less likely for there<\/span><\/p>\n

to be a barnacle zone when there is an abundance of seaweed, <\/span>because it <\/span>removes the juvenile<\/span><\/p>\n

barnacles from their place of settlement (Fish, 2008). Acorn barnacles are found on <\/span><\/p>\n

rocky shores spanning <\/span>from the Pacific Northwest all the way to north-west Spain, and many places in<\/span><\/p>\n

between. The <\/span>acorn barnacle is a <\/span>hermaphrodite, meaning it possesses both male and female<\/span><\/p>\n

reproductive organs (White, 2008).\u00a0<\/span>There is only one breeding <\/span>season and it occurs in fall. Acorn<\/span><\/p>\n

barnacles cross-fertilize with nearby barnacles by\u00a0<\/span>extending their penises outside of <\/span>their shells and<\/span><\/p>\n

testing other shells until they find a functional female. They have the <\/span>biggest penis to body ratio out of<\/span><\/p>\n

the entire animal kingdom. Fertilized\u00a0<\/span>eggs are stored within the <\/span>barnacle until they\u00a0<\/span>become nauplii.<\/span><\/p>\n

\u00a0 \u00a0 \u00a0 \u00a0 Acorn barnacles are adaptable, but they are still susceptible to environmental dangers. A study<\/p>\n

from 2009 done by the Marine Biology and Ecology Research Centre stated the negative affects of high<\/p>\n

CO2 levels on the survival of semibalanus balanoides. They found that the “Embryonic development<\/p>\n

rate was significantly slower in the high-CO2 treatment than in the control but still resembled \u2018natural\u2019<\/p>\n

rates seen in populations found in similar locations. There was an estimated 19 d delay in development<\/p>\n

under high-CO2 conditions, which resulted in a 60% reduction in the number of nauplii reaching<\/p>\n

hatching stage at the time when over 50% of the control nauplii had hatched. We conclude that ocean<\/p>\n

acidification could potentially further compromise embryonic development in a species already<\/p>\n

stressed by temperature, which could in turn impact naupliar development and recruitment. S.<\/p>\n

balanoides, the adults of which live in a highly variable environment, has been shown to be<\/p>\n

detrimentally impacted by a chronic change in chemical conditions (pH lowered beyond the current<\/p>\n

range) over a crucial period in their life cycle. Under experimental high-CO2 conditions, some adults<\/p>\n

were able to survive and larvae were able to hatch. This may indicate that there is still potential for<\/p>\n

organisms to find suitable habitats and for populations to develop and survive.”(Findlay, Kendall, et al.,<\/p>\n

2009). Basically, the embryonic development of Semibalanus balanoides is\u00a0being compromised by<\/p>\n

rising CO2 levels, but some of the test subjects survived under stressed conditions, so there is hope for<\/p>\n

the survival of their species. This is important because although there have been studies on other<\/p>\n

crustacean larva, before this there was no information concerning the affects of CO2 on Semibalanus<\/p>\n

Balanoides. There is now evidence backing up the negative consequences of high CO2 on these<\/p>\n

animals. In another article by the same organization one year later, they tested what ocean acidification<\/p>\n

can do to the population dynamics of\u00a0Semibalanus balanoides at it’s Southern range end. “Using<\/span><\/p>\n

empirical data, we forced a barnacle (Semibalanus balanoides<\/span>) population model to investigate the<\/span><\/p>\n

relative influence of sea surface temperature (SST) and ocean acidification on a population nearing the<\/span><\/p>\n

southern limit of its geographic distribution. Hindcast models were compared to observational data <\/span><\/p>\n

from Cellar Beach (southwestern United Kingdom). Results indicate that a declining pH trend (\u22120.0017 <\/span><\/p>\n

unit\/yr), indicative of ocean acidification over the past 50 years, does not cause an observable impact<\/span><\/p>\n

on the population abundance relative to changes caused by fluctuations in temperature. Below the<\/span><\/p>\n

critical temperature (here T<\/em>crit<\/sub> = 13.1\u00b0C), pH has a more significant affect on population dynamics at <\/span><\/p>\n

this southern range edge. However, above this value, SST has the overriding influence. At lower SST, a<\/span><\/p>\n

decrease in pH (according to the National Bureau of Standards, pHNBS<\/sub>) from 8.2 to 7.8 can significantly<\/span><\/p>\n

decrease the population abundance. The lethal impacts of ocean acidification observed in experiments<\/span><\/p>\n

on early life stages reduce cumulative survival by ~25%, which again will significantly alter the <\/span><\/p>\n

population level at this southern limit. Furthermore, forecast predictions from this model suggest that<\/span><\/p>\n

combined acidification and warming cause this local population to die out 10 years earlier than would<\/span><\/p>\n

occur if there was only global warming and no concomitant decrease in pH.”(Findlay, Burrows, et al., <\/span><\/p>\n

2010). This indicates that it in fact does have an affect on the population dynamics and would cause<\/span><\/p>\n

the species to die out prematurely.<\/span><\/p>\n

\"\"

Adult sessile barnacles mounted on a rock<\/p><\/div>\n

ACORN BARNACLES AND THE 21ST CENTURY:<\/p>\n

\u00a0The thing that interested me the most about acorn barnacles is their reproductive system. They have<\/p>\n

evolved to be hermaphroditic, having both female and male genitalia. They evolved this way for survival<\/p>\n

because they are sessile creatures. This got me thinking about the evolution of sexuality and gender in<\/p>\n

humans in the 21st century. Acorn barnacles evolved this way out of necessity, does that mean this<\/p>\n

generation of gender and sexual fluidity could be out of necessity too? What if the reason that gender<\/p>\n

and\u00a0sexuality are\u00a0<\/span>becoming more open-ended is not only because of cerebral growth, but also out of a<\/span><\/p>\n

biological need to\u00a0<\/span>be less heterosexual and therefore control\u00a0the size of the overabundant population<\/span><\/p>\n

we have?<\/span><\/p>\n

 <\/p>\n