Rangia: cleaning up a bad reputation 



You could hardly call it a seafood delicacy. Until 

 twenty years ago it wasn't even found along our 

 coast. But a sudden, unexplained extension of its 

 range in the mid-1950s firmly established the Rangia 

 clam as a regular resident of the shallow, brackish 

 waters of North Carolina's estuaries. 



It's hard to mistake the Rangia for a surf or hard 

 clam. Its heavy, brown shell is shaped more like a 

 mussel than a clam. And its taste . . . well, ask people 

 who have bitten into the meat of a Rangia clam, and 

 they will tell you that it is far different from any 

 clam they've eaten before. Some say it tastes 

 "musty." Others claim that it tastes similar to the 

 smell of a rotten log. 



Yet people do eat the Rangia. And some North 

 Carolina seafood dealers, always on the lookout for 

 new products, have hopes of reviving the Rangia 

 market. In the late 1890s Rangia was marketed in 

 Texas as the "Texas little neck." During the 1960s, a 

 North Carolina seafood dealer sold the clam to 

 markets in New York City for use in a clam cocktail. 



But suddenly things began to turn sour for the 

 Rangia in North Carolina. A shipment of fresh, 

 shucked Rangia clams bound for markets in New 

 York City failed to pass an inspection by New York 

 health authorities. The reason: the clams contained a 

 higher than acceptable level of bacteria. The entire 

 shipment was seized and $10,000 worth of Rangia 

 clams was destroyed. 



Concerned by the incident, results from his own 

 tests and the questions being raised by other North 

 Carolina dealers interested in marketing the clam, 

 Bob Benton, N. C. Shellfish Sanitation Program 

 supervisor, turned to Sea Grant for help. 



Immediately researchers Barney Kane and Donald 

 Jeffreys of East Carolina University set out to deter- 

 mine the cause of the high bacterial counts and 

 whether they posed a public health hazard. 



With the assistance of graduate researcher Paul 

 Comar, the scientists sampled Rangia clams at four 

 different sites in Albemarle Sound over a 12-month 

 period. The studies included waters that were both 

 opened and closed to shellfishing, representing ex- 

 tremes in environmental and sanitary conditions. 



In the laboratory, each sample was analyzed for 

 bacterial content. And after a year of study, the re- 

 searchers determined that the Rangia clams had a 

 naturally high level of bacteria. More importantly, 

 they found that samples taken from waters open to 

 shellfishing did not contain any pathogenic (disease 

 causing) bacteria. 



If the bacteria in the clams were not pathogenic, 

 why did New York health authorities reject the ship- 

 ment of North Carolina Rangia? 



New York, like many states including North Caro- 

 lina, uses what is known as a standard plate count 

 (SPC) to test for bacteriological safety. The test es- 

 timates the total bacterial content of a food; 



Kane with pasteurized Rangia meat 



theoretically, a food with lots of bacteria (a high plate 

 count) has somehow been contaminated. 



Unfortunately, the SPC cannot discriminate be- 

 tween those bacteria which are harmful or patho- 

 genic and those which aren't. As a result, the test 

 does not always accurately reflect the true health 

 hazard of a particular food. 



According to Kane, a similar situation exists with 

 the Rangia. "We have demonstrated that the high 

 standard plate count is not at all indicative that these 

 organisms [the Rangia] are accumulating higher 

 levels of disease organisms than any other seafood," 

 observes Kane. "There isn't a shred of evidence which 

 indicates that they are more dangerous than any 

 other shellfish," he adds. 



While the Kane and Jeffreys study indicates that 

 the Rangia may be safe to market from a bacterio- 

 logical standpoint, there are still many questions that 

 need to be answered before the clam can be given a 

 completely clean bill of health. 



Because the Rangia grows best in waters that are 

 only slightly brackish, such as those found in the up- 

 per reaches of estuaries, it is exposed to more concen- 

 trated levels of waste runoff than are many other es- 

 tuarine organisms. From a public health standpoint 

 that's an important distinction. As filter feeders the 

 clams ingest water and suspended sediments which 

 pass around them. If toxic substances, such as 

 pesticides and heavy metals, are present in the water, 

 (See "Taste, " page 1+) 



