 Shares of Natera Inc. NTRA, -32.05 plummeted 32.9 in active afternoon trading Wednesday toward a 22-month low, enough to pace all of the Nasdaqs decliners, after noted short seller Hindenburg Research called the Texas-based genetic testing services company, Pioneers in deceptive medical billing. Trading volume ballooned to 33.9 million shares, compared with the full-day average of less than 1 million shares. 