What kind of clam is the mulberry wine in "The Eternal Moon"?

Recently, the Xianxia drama "Chang Yue Jin Ming" was broadcasted on Youku, and unexpectedly set off a delicacy - clam vermicelli. The heroine "Sang Jiu" in the drama is the princess of the "Mohe Clam Clan" - from the perspective of animal taxonomy, it can be understood that the heroine of this drama is a "bivalve animal that has become a spirit."

For netizens who like the couple in the drama, the most familiar bivalve is probably the "clam". Fans of bivalve can therefore be called "clam fans" - it is said that the sales of "clam fans" on food delivery platforms have also increased significantly recently. Some merchants even renamed the "clam fans" they sell according to the names of the characters in the drama, such as "Sangjiu Qingtang Clam Noodles", "Mohe Family Portrait Clam Noodles", "Mingye (the male protagonist in the drama) Sad Clam Noodles", etc., to attract attention.

But here comes the question: What kind of spirit is Princess Sangjiu? Are she and the "Clams" in Clam Noodles from the same family?

01

What kind of clam is Princess Sangjiu?

The name of the Mohe Clam Tribe comes from both the river and the clam. At the same time, the shell of Princess Sangjiu shown in the drama is about 20 cm long, white on the surface and with a beautiful luster on the inside. From this, we can know that Princess Sangjiu should be a river clam living in freshwater areas.

The clam shells used to make mulberry wine in the drama. Image source: Screenshot from the drama

River mussels are a collective name for nearly a thousand species in the order Mussels of the class Bivalvia of the phylum Mollusca, and are the most common type of molluscs in freshwater areas. Most of them are only distributed in freshwater, and only a very small number of toothless clams live at the mouth of rivers.

China is one of the countries with the richest river mussel species in the world. In his book River Mussels, Guo Liang, a river mussel researcher, recorded 145 species of mussels in China, of which 102 are known species, accounting for about 10.3% of the 982 known mussel species in the world.

Due to the diversity of habitats, different species of river clams vary greatly in shape, size, and shell decoration:

Sinosolenaia carinata has a long and narrow shell, like a sharp knife, and can reach a length of more than 41cm. It is the longest river clam known in China.

Dragon bone Chinese razor clam. Image source: DOI:10.37828/em.2021.39.1

The Sinohyriopsis cumingii shell has a slightly triangular shape and one side of the shell is unusually extended like a sail. It is often cultivated artificially for growing pearls.

The cumingian fan clam. Image source: Wikipedia

The Cristaria plicata is slightly oblong in shape and is the largest river clam known in China. Large individuals can weigh more than 5kg. It is also one of the most common river clams in the Yangtze River Basin.

Pleated crown clam. Image source: Wikipedia

The shell of the river clam is composed of three layers. The outermost layer is the fibrous "cuticle", which is the shell skin, usually brown or dark brown; the middle is the white "prismatic layer", which is the shell layer, which is the main body of the shell; the innermost is the "nacre layer", which is shiny.

You must be confused after reading this: But the shell of Princess Mulberry Wine in the play is white! This is probably because the production team felt that the brown-black cuticle layer was not good-looking, so they polished the prop clam shell to reveal the white prism layer.

So, which kind of river clam is Princess Sangjiu most likely to be?

The props in the play are slightly oblong in shape. Using the hand and the bowl as reference, we can roughly infer that the shell length is at least 20cm. Among the common types of river clams, the most likely corresponding one is the Cordon rufous .

Of course, this is just a guess based on the images in the drama. If we really want to match it to a species, it would be best to ask Princess Sangjiu to do a genetic comparison and confirm it at the molecular level.

Image source: Screenshot of the series

02

What exactly is “Sixty-year-old”?

"Flower clams" (called flower clams in some places) is a general term for some species of the family Ruditapes in the order Ruditapes of the class Bivalvia of the phylum Mollusca. All of them are marine, and the most common one is the Manila clam (Ruditapes philippinarum).

The colorful Philippine clams. Image source: Wikipedia

In some coastal areas, there are also "flower clams" with local characteristics, such as the equilateral shallow clam (Macridiscus aequilatera), the semi-cloth shallow clam (Macridiscus donacinus), the green clam (Cyclina sinensis), etc.

Their common characteristics are that their shells are laterally flattened and have many patterns, so they are collectively called "flower clams" (or clams).

Equilateral shallow clam. Picture from the Internet

Semi-bullus clam. Image source: conchology.be

Green clam. Image source: Wikipedia

Take the Philippine clam as an example. This shellfish contains a variety of amino acids, trace elements and rich protein. It is a good and cheap seafood and is loved by everyone. If you want to choose the most popular seafood dish, it must be fried clams (fried clams).

In recent years, "clam noodles" have also blossomed everywhere. Judging from the pictures of "clam noodles" posted by netizens, most of the "clams" are Manila clams, and a few are Paratapes undulatus.

The undulating clam Paphia undulata. Image source: Wikipedia

03

Are “flower clams” and “river clams” from the same family?

Although they are both bivalve mollusks, clams and river clams are quite different. Generally speaking, there are three obvious differences:

First, the distribution areas are different. All "flower clams" are marine and live in seawater (or brackish water), while "river clams" are mostly only distributed in freshwater areas;

Secondly, their taxonomic status is different. The "flower clams" belong to the order Venerida, while the "river clams" belong to the order Unionoida, which can only be regarded as "distant relatives among distant relatives";

Finally, the size is different. The "flower clams" are relatively small, with a shell length of usually no more than 5 cm, while the "river clams" in the play, the pleated crown clams, are larger, with a shell length of nearly 20 cm.

Interestingly, in addition to "clam powder", many netizens also took photos of some mollusks or their shells to "find family" for Princess Sangjiu in the play.

We invited shellfish scholar He Jing to make a preliminary confirmation of the species involved in the photos. The species in two of the photos are both from the family of the order Mussels of the class Bivalvia. In biological classification terminology, the name of the classification unit family just comes from the word "family". In this sense, they are indeed the "family" of Princess Sangjiu.

Image source: Weibo screenshot

However, the other photo basically contains snails. Except for a kind of gorgeous large clam, the rest basically belong to the class of gastropods, which are definitely five generations apart from Princess Sangjiu.

Image source: Weibo screenshot

04

Does Princess Sangjiu have pearls?

Since Princess Sangjiu is a "river clam that has become a spirit", a new question naturally arises: Can she produce pearls?

There are three common misconceptions about pearls:

First, only a few species of shellfish produce pearls;

Second, pearls are formed when the shellfish's mantle contains sand;

Third, pearls are usually round, oval, or pear-shaped.

In fact, this is not the case.

First of all, in theory, all mollusks can produce pearls because they all have mantles and can secrete nacre; secondly, most natural pearls are caused by parasites, and only a few are caused by sand particles; finally, the shape of the pearl is related to the "trigger (trigger source)", so it is normal for it to have strange shapes.

The common round, oval and pear shapes nowadays are mostly artificially cultivated and screened for commercialization.

Cultured pearl oysters. Copyrighted images from the gallery, unauthorized reproduction

Regardless of whether the Princess of Mulberry Wine is a "spirit of the pleated crown clam", as long as she is a mollusk, she has the potential to produce pearls. Perhaps, the "immortal marrow" of mulberry wine mentioned in the drama is the pearl that the fans of the drama have eaten out of this bowl of "clam powder".

In fact, river mussels are one of the most vulnerable animal groups in the world to extinction. With the influence of global climate change, modern development, pollution, fishing, and the extinction of native fish species that have a parasitic relationship with river mussels, more and more river mussel groups are facing the threat of extinction. In the IUCN Red List of Endangered Species, there are about 200 species of river mussels on the verge of extinction. As of 2008, 37 species of river mussels have become extinct and 168 species are critically endangered.

Perhaps in the "Prajna Floating Life" fantasy in the play, we can only watch the extinction of the clam population, but in the real world, we still have the opportunity to make our best efforts to contribute to the reproduction and survival of the river clam population.

Author: Liu Yi, PhD in Environmental Science, Xiamen University, Chairman and Executive Director of the Mangrove Conservation Alliance

Reviewer: Zeng Yan, Senior Engineer, Institute of Zoology, Chinese Academy of Sciences