Maria quickly pointed out the water quality testing stations, the quarantine tanks for ill or injured animals, and the stairwell beside the shark acclimation pool that led down to a small observation room on a lower level. Although I couldn’t be sure what the animal husbandry area usually looked like, nothing appeared out of the ordinary.
I gestured to a two-meter-long metal basket on the deck near the acclimation pool. “Is that for transferring the sharks?”
Maria nodded. “We call it the Cradle. Some of the sharks weigh over a thousand pounds. Without that we wouldn’t be able to get them into or out of the acclimation pool.” She aimed her finger at the three-inch-long hook that hung from the cable above the Cradle, and then guided my eyes up the cable, past the place it coiled around a large drum, to the control panel on the wall. “It’s hydraulic,” she said.
I noted that a lifeguard’s backboard and a highly advanced automated external defibrillator were hanging on the wall beside the controls, readily available in case any of the divers needed to be rescued. Next to them was a phone.
Maria’s eyes jumped restlessly across the room toward the door.
“Cassandra’s OK, right? I mean, nothing bad happened to her or anything? Right?”
“As far as we know, Cassandra’s fine,” Lien-hua said.
“But why would her car be here if she was OK, though?”
“Maria,” Lien-hua said gently, “can you tell me a little more about Cassandra’s work? What exactly does she do here? Is she an educator?” I noticed that Lien-hua had unobtrusively positioned her digital voice recorder in her pocket. I assumed she had also pressed “record.”
“No, that’s more what I do. I coordinate the tour guides’ schedules. Cassandra’s a researcher. She’s always diving with the sharks.”
Maria tapped the first two fingers of each hand rapidly against her thumbs. “Mostly, she’s studying the ampullae of Lorenzini.
Government work. A grant, I think. It’s kind of a big deal to the aquarium, being one of the leaders in the world in understanding the ability of sharks to-”
“Wait,” I said. “I’m sorry. You’re going to have to back up for a minute. The ampullae of what?”
“Lorenzini. They’re these little organs on a shark’s head and snout that can sense electromagnetic fields.”
Lien-hua and I exchanged glances. “Sharks can sense magnetic fields?” I asked.
Maria nodded. “The ampullae are filled with a jellylike substance that acts like a semiconductor.”
She seemed to be relaxing somewhat now that she was in her element as a shark educator. She walked to a life-sized anatomical diagram of a lemon shark that hung from the wall, and pointed to a series of large pores on the shark’s head and snout. “Electric fields are produced whenever fish swim through the earth’s magnetic field, and naturally when muscles contract. Sharks can locate fish by sensing these minute charges. In fact, sharks can even find a flounder buried beneath the sand, just by its electronic impulses.”
“They can actually sense these impulses through matter, through sand?” Lien-hua said.
“Yes,” said Maria. “Other cartilaginous animals have the sensory organs too, but the ones on sharks are by far the most advanced.
Sharks can even use these organs to swim thousands of miles and return to their exact starting position in the ocean by using the earth’s magnetic field to track their navigation.”
Geomagnetic orientation. Electroreceptors. I was amazed. I’d never heard any of this before. “So, sharks can really do this? Really identify a fish’s location just by the electric or magnetic impulses created by muscle twitches?”
“Actually their sensory system is so precise they can even locate paralyzed prey. So really, she’s OK then? Cassandra is?”
Lien-hua is much more tactful than I am so I decided to let her address Maria’s question.
I noticed a door with Cassandra’s name on it, and with the words paralyzed prey ringing in my head, I entered her office.