Marine Invertebrates of Bermuda Amber Pen Shell (Pinna carnea) By Cassandra Becker and James B. Wood and Abel Valdivia (Eds) Taxonomy  Abstract  Habitat  Ecology  Recent Research  Commercial Importance  Bermuda Laws  Personal Interest  References  Links

Taxononmy


Phylum: Mollusca
  Class: Bivalvia
    Order: Pterioida
      Family: Pinnidae


Abstract


Pinna carnea, or the Amber Pen Shell, is also known as the Spanish Oyster or Sand Oyster. It is a long, thin bivalve that is found partially buried in sand or mud. It has large, almost transparent, triangular fragile fan shaped shells that vary in color from amber to light orange. The exterior appears dull while the interior of the shells has an iridescent coating. They are sessile and attach to the substratum with long byssal threads which extend from the base of the shell. Shells grow to a maximum length of approximately 40cm and are known to be able to repair or regrow these shells when breakage occurs. (Yonge 1953, Sterrer 1986) Recent research has focused on how it has been effected by El Niño and La Niña (Jörg Urban, 2002; Rowe 2002; Soto et al. 2002), its larval growth patterns (Narvàez et al. 2000). It has no commercial importance and no laws concerning it. I became interested in the Amber Pen Shell when I discovered its hidden beauty while snorkeling in Bailey’s Bay and Ferry Reach Flats.


Habitat


Pinna carnea must live embedded vertically into a soft substrate. Therefore it is generally found in sand or small grained gravel, but will occasionally anchor in sandy mud. They have been known to occur at depths up to 20m and occasionally the intertidal zone, but are most common in shallow, protected water. In Bermuda they are found between islands and in the lagoon. Once a larvae has settled, it will embed and does not move for the rest of its life. On occasion, if the animal is uprooted and lands upright in a new spot, it will reattach itself to the sand. (Yonge 1953)
Pinna carnea are often found around seagrass beds, and can be difficult to see, as they become covered in algae and other sessile invertebrates such as polychaete worms. P, carnea attaches itself to the substrate with long byssal threads which extend from the muscular foot down into denser sediment below the surface. Using these threads and the retractor muscle, the animal can “burrow” its way further into the sediment as it grows, keeping the majority of its shell protected (Yonge 1953).


Ecology


Pinna carnea are suspension feeders. They draw water into the shell using a combination of muscles and ligaments (Yonge 1953). Water rushes into a part of the mantle cavity called the inhalant chamber on one side of the ctenidium. The ctenidium is a sort of membrane containing gill like structures. When the ctenidia are extended water flows over them and particles are trapped by cilia and passed along the marginal groove to the mouth. Pinna carnea has a full digestive system and waste is excreted through a distinctive canal only found in Family Pinnidae (Yonge 1953). It releases waste into the posterior end of the inhalant mantle cavity where the water flow takes it out of the animal. Pinna carnea also has an open circulatory system and obtains oxygen through the ctenidium. By bringing water in and expelling it out of the top part of the exposed shell, it avoids causing excess turbation in the sediment which would make filtration and feeding more difficult (Yonge 1953).
Pinna carnea has an incredible ability to repair its shell when it breaks, which happens frequently due to fish and water flow. The outer prismatic layer of shell can be reformed by the mantle which secretes the shell. It can repair over 3mm in 24 hours (Dietl & Alexander 2005; Yonge 1953). Pinna carnea are hermaphroditic, containing both spermatozoa and ova in their gonads. Whether or not they can self fertilize or are protandrous or alternating hermaphrodites is not known (Yonge 1953).
Pinna is found widely distributed geographically and temporally. Pinna cretacea fossils have been found dating to the cretaceous period ranging from Brazil to Russia to Tunisia and South Africa. This ancestor is supposed to be very similar to living species in the genus Pinna (Seeling & Bengtson 2003).


Recent Research


Most recent research has focused on the cousin of Pinna carnea, P. nobilis, but some research has also been done on the Amber pen shell. One study investigated juvenile pen shell growth and settlement (Narvàez et al. 2000). They looked at how various factors such as temperature and availability of food. They found that though Pinna carnea grows very quickly in its first 4-5 months, edible muscle production does not peak until 14 months and is highly dependant on the availability of food. This makes Pinna carnea less than optimal for commercial aquaculture (Narvàez et al. 2000).
Other research has focused on the effect of El Niño and La Niña on the seagrass communities which include Pinna carnea. El Niño and La Niña created greater amounts of upwelling along the coasts where Pinna carnea is found. Entire food webs were shifted, but the effect was found to be minimal on Pinna carnea. (Tewfik et al. 2005; Jörg Urban, 2002; Rowe 2002; Soto et al. 2002).
Pinna carnea is smaller than European, protected cousin P. nobilis, which grows to 86cm and can live for up to 20 years in the Mediterranean(Richardson et al. 1998). P. nobilis grows more slowly than P. carnea and can act as a bioindicator, and keeps a record of climate conditions in its calcitic shell. By closely examining P. nobilis shells, scientists have found that the growth and composition of the shell is directly related to climate conditions and water quality during the growth period. This has not yet been examined in P. carnea, but it is quite possible that it has a similar property(Richardson et al. 1998). Very recently scientists also found that P. nobilis has two new proteins in its shell called caspartin and calprismin which seem to be unrelated to any other known protein (Martin et al. 2005). Again, no one has yet investigated whether or not P. carnea has these proteins.


Commercial Importance


Pinna carnea has no direct commercial importance to Bermuda. It adds to biodiversity, which could be helping ecotourism, but as the pen shell is not very “showy,” it is often overlooked. The interior of the shell is occasionally used for jewelry, but this is a very minor contributor to the economy.


Bermuda Laws


There are no Bermuda laws directly relating to the pen shell (Wood & Jackson 2005).

Personal Interest


I became interested in the Amber Pen Shell after observing them in Bailey’s Bay and the flats of Ferry Reach. From the outside they appear dull, and are often covered with algae and polychaetes. However, on the inside they are a beautiful iridescent amber. Pen shells are also thought to be a delicacy in some Asian cuisines, where it is known as matairagi or tairagi though it is more commonly a species in a related genus, Actrina pectinata, that is used for this. I have personally tried it and found them quite delicious.


References


Dietl G, Alexander RR (2005) High frequency and severity of breakage-induced shell repair in western Atlantic Pinnidae (Bivalvia). Journal of Molluscan Studies 71(3):307-311

Jörg Urban H (2002) Indirect El Niño effects on reproductive strategies of the Carribbean bivalves Pteria colymbus, Pinctada imbricate and Pinna carnea. Investig. Mar. Symposium Valparaiso 30(1)

Martin F, Amons R, Guichard N, Stigter M, Hecker A, Luquet G, Layrolle P, Alcaraz G, Riondet C, Westbroek P (2005) Caspartin and Calprismin, two proteins of the shell calcitic prisms of the Mediterranean fan mussel Pinna nobilis. J Biol. Chem. 280(40):895-908

Narvaez N, Lodeiros C, Freites L, Nunez M, Pico D, Preto A (2000) Abundance and growth of Pinna carnea (Mytiloida: Pinnacea) juveniles in suspended frame cultures. Rev Biol Trop 48(4):785-797

Richardson CA, Kennedy H, Duarte CM, Kennedy DP, Proud SV (1999) Age and growth of the fan mussel Pinna nobilis from south-east Spanish Mediterranean seagrass (Posidonia oceanica) meadows. Marine Biology 133:205-212

Rowe GT (2002) Food wed responses to La Niña and El Niño events. Investig. Mar. Symposium Valparaiso 30(1)

Seeling J, Bengtson P (2003) The bivalve Pinna cretacea (Schlotheim, 1813) from the Cretaceous of Brazil. Acta Paleontologica Polonica 48(3):475-480

Soto RM, Muñoz SM, Moreno RA (2002) Biological Background of “El Niño” and “La Niña” in Intertidal and Subtidal Communities of the Northern Zone of Chile. Investig. Mar. Symposium Valparaiso 30(1)

Sterrer, Wolfgang (1986) Marine Fauna and Flora of Bermuda; A systemtic Guide to the Identification of Marine Organisms. © John Wiley & Sons, Inc

Tewfik A, Rasmussen JB, McCann KS (2005) Anthropogenic enrichment alters a marine benthic food web. Ecology 86:2726-2736

Wood JB, Jackson KJ (2005) Bermuda. Caribbean Marine Biodiversity: the Known and the Unknown. Pennsylvania: DEStech Publications, Inc. 19-35.

Yonge CM (1953) Form and Habitat in Pinna carnea Gmelin. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences Vol. 237, No. 648, 335-374

Links

Bermuda Biodeversity Project
Bermuda Biological Station for Research
Duke University Homepage
One way to prepare tairagi