Giant clams typically present viewers with a prominent gape, which is enhanced in living animals by a colourful and fleshy mantle filled with photosynthetic zooxanthellae that convert sunlight into energy for themselves and their sedentary host. Prompted perhaps by this benthic visage, German-born soldier-turned-naturalist Georgius Everhardus Rumphius was led to coin, in his parvum opus, The Ambonese Curiosity Cabinet, the binomial Chama Aspera for large shellfish that he encountered, or was presented with, in the town of Hiru on the northern coast of Ambon, where he lived in the latter half of the 17th century.
Chama, explains Rumphius scholar E.M. Beekman, comes from chema, Greek for a "gaping mussel", while aspera means "rough". Today, the former term is attached to heterondont bivalves in the family Chamidae, which in common parlance are known as jewelbox shells. Rumphius' coinage, which arose from his own deliberations and pre-dated modern conchology, denotes Chamae as
"all those Shells which, lying bare on the ground, for the most part gape, and could, therefore, be called Gapers."
He later adds:
"Chametrachea or Chama Aspera, are those that have a rough shell, either through ribs that stick out, or because of scales and nails."
This description would ring a bell for those who are familiar with Southeast Asian reef assemblages as well as the way baselines for shallow-water fauna have shifted over the centuries to render the common rare and erase gaps in the chain of life under the tides. Tridacnines (for the family Tridacnidae is now buried within the true cockles) once occurred in densities that could support littoral populations across the Indian Ocean and Asia-Pacific, and may have persisted as a sustainable fishery in Rumphius' time, when he gave the name Chama squammata to an ill-defined taxon, known in Ambonese Malay as Bia garu, "that is Scratchers, because one could scratch someone badly with them, or because they scratch the hands, when one handles them." Bia is a broad term for "shell" while garu can mean "harrow" or "rake", a reference perhaps to the toothed fringe of the valves or more possibly to the sharp scutes on the shell's outer surface.
(Rumphius also took pains to distinguish Chamma from what he termed Klipkoussen, a "vulgarism" that combines the Dutch words for "rock" (Klip) and "stocking" (Kous). The great naturalist observed that some contemporaries used the term to refer to snails that we now recognise as cowries, but found some impropriety in it, as Klipkoussen was also applied to female genitalia, and by extension, women. Beekman, who translated Rumphius for a late 20th century audience, chose to render the word as "clack dish", a Shakespearean euphemism that refers to a beggar's bowl for alms but which the Bard employed to refer to a lady's pudendum in Measure for Measure, in which the Duke "put a ducat in her clack-dish".)
(A more sober footnote on etymology comes with Beekman's annotations on the origin of the modern genus for giant clams, which he explains arose from a "funny anecdote" by the elder Pliny "that the name tridacna, from the Greek tris for "three" and daknō "I bite", came about because someone jested that he would like to have the oysters that reputedly came from the 'Indian Sea' because they were so big that they needed three bites to be consumed.")
Rumphius was quick to discern between what he called Pelagiae, "the largest of all Shellfish", which grew to a length of 5 feet and were so bulky that "6 or 8 people have more than enough to carry just one" and were confined to deeper waters, and smaller Littorales, which could be found around beaches. The latter was sexually dimorphic, he added, with the female being
"the most common, its shell is divided into 4 or 5 round ridges that jut out, making deep furrows between both, with sharp edges that are jagged, so that the shell goes up and down like waves, both inside and outside; on the back are large curved scales, very similar to human nails, round and sharp in front, but most of them, especially the old ones, are broken off and damaged."
Male Chamma, on the other hand, were
"more oblong, divided into 9 or 10 ridges, and the scales are closer together, but are shorter than those of the Female, and the opening on the one side is much larger: otherwise it has the same shape."
Beekman has suggested that the male animals may have been Tridacna maxima, a species that exhibits relatively weak vertical folds and close-set, scarcely prominent scutes, and which partially embeds itself into coral rubble and other reef substrates. The females were probably the Tridacna squamosa of modern nomenclature, a giant clam with deeply fluted valves and a formidable array of scutes (scales), which serve in young individuals as an adaptation against predatory crabs and fish. Rumphius may have been sexually confused, but his comments on mature specimens ring true; large giant clams, such as one encountered in repeated surveys of patch reefs near Pulau Semakau, may have shells bereft of their "nails" after years of bites and being rocked against nearby rocks by unruly waves.
Rumphius was also fascinated by the appearance of older Bia garu, which had outer shells that were "very much overgrown with moss, lime, and other sea grit, even with other shells, mussels and coral trees, so that one would hold it to be a rock, rather than a shell." Young specimens, he noted, "are a dirty white on the outside, without luster, inside a yellow-white like ivory."
He was rather less fond of the "Beast that lives within", however, which he found
"dreadful to behold, because if one looks upon one that is gaping, one sees nothing but a taut skin, full of black, white, yellow, and lead-coloured veins, painted like a snake's skin."
Despite this distaste, Rumphius was able to muster enough scientific curiosity to describe morphological features such as the clam's inhalant and exhalant siphons, beard-like "coarse and tough threads" that the animals use to "cling to the rocks so they will not be tossed around", and a thick tendo fastened to both halves of the shell, which is surrounded by a fleshy disk that was judged to be "the best for eating".
Unfortunately, Rumphius was to veer into more outlandish territory in his, almost certainly second-hand, observations of Pelagiae, which he wrote was capable of snapping off anchor ropes and careless limbs, and furthermore, had a predatory bent:
"They gape almost always when on the ground, especially in order to catch the little fishes that come in multitudes to swim and play therein, until all of them together are suddenly locked in there, and come to serve as the Beast's food."
Collaborating with Tridacna gigas in this macabre trap, according to Rumphius, is a
"kind of little Shrimp... which pinches its flesh when it sees that there is a great deal of prey in its house, whereupon the shell snaps shut, and one believes that the Beast cannot live, if that little Pinna Guard happens to be away from it, because the Beast cannot see, and cannot be on guard for robbers."
Rumphius' discourse on Bia garu goes on to cover methods for capture, culinary and organoleptic aspects, local superstitions, and the formation of precious stones, even light-emitting ones, within the gape. Species believed to be Tridacna crocea, which burrows into rock and even concrete, and Hippopus are also discussed, in what is thought to be the first systematic description of living tridacnines, their habits and natural habitats in modern conchology. More than three centuries after his tour of duty in the Spice Islands, Georg Everhard's nocturnal submissions still take no prisoners in their celebration of antiquity, on which the former mercenary heaps a mélange of lore from the Malay archipelago, and his lifelong desire to capture the living treasures of the East Indies and set them loose in an imaginarium of words that draw no line between the material world and the magic of reality.