by James OwensOur new series entitled The Reef after Dark or Things That Go Bump in the Brine is written so we might experience the 210-gallon reef tank’s deeper darker more secretive life. Let’s start by proclaiming that things that happen in our our eyes and often worst experienced with our sense of touch, in tones of poke, sting, or bite. The reef tank is designed to be at its very least a provocative peek into a lush but dangerous ocean habitat. As such we are usually limited in scope to the hours the Science Center is open and the opportunities in time where we have the tank lights lit for our luminous amusement and the various organisms’ good sense of circadian rhythm. The tank’s diurnal (daylight oriented) creatures, unlike us (as the late night word-smitty or insomniac), never stay active into the hours their body’s instinctual time clock tells them they belong not; they often hideaway lest this be the last time they venture thusly. As we shine our attention onto what happens in the darkness, after hours, in the cryptic nocturnal world, when the lights go dim and the actors change scenes, be prepared to look through new lenses to experience a world where we are not necessarily well prepared or welcomed.
This series begins with a creature that at first seems to do most of its labor in the light setting up a reef wash station––a fish-cleaning station on top of a section of the live rock. The Scarlet Shrimp waves its antennae in a signaling manner that says “open for business” until a large fish stops by. The shrimp then probes all over the fish, along the gills and even inside the mouth of the fish removing parasites and dead tissues. Rumor has it that this industrious creature also has an alter ego, a nocturnal presence as a gnarly scavenger. Now in science we abhor information relegated to rumor, so in the coming weeks we will investigate shrimp behaviors, especially after dark.
This we know: Scarlet Cleaner Shrimp, A.K.A. Northern Cleaner Shrimp, Skunk Cleaner Shrimp, Pacific Cleaner Shrimp, Lysmata amboinensis, or Lysmata (Lys meaning loose & mat, -aeo,eo meaning foolish as in foolhardy to be cleaning fishes mouths that are capable of eating you), is a member of the decapod family Hippolytidae Dana, a polyphyletic (many races) group of mostly small, benthic (bottom dwelling) shrimps of hard ocean substrates. The Scarlet Shrimp is festively attractive; its colors are light amber with one dorsal white and two lateral red longitudinal bands. There are two white spots on each side of the tail. Four antennae are white and as long as the body. It has ten walking legs and the first two have forceps; at the front it has one long pair of white maxillipeds held out like a dog begging.
A Scarlet Shrimp begins as a male but later becomes a hermaphrodite. It has four molts as a male before changing sexes to become an euhermaphrodite (eu-meaning true, and from hermaphroditus––the effeminate male son of the Greek God Hermes and Goddess Aphrodite). In the euhermaphrodite stage the shrimp acts as a male between moults and as a female immediately following a molt. During this euhermaphroditic stage, the shrimp gradually loses its male organs, likely because more energy is shifting to the development of female reproductive organs. The Scarlet Shrimp employs a ‘pure searching’ tactic for mate-finding in which the male is constantly searching for a receptive female. The male uses olfactory organs on its antennules to detect soluble female sex pheromones. These pheromones are released 2–8 hours prior to female molting. Guided by these chemical signals, the male makes its way to the female and will approach her. The male will then ‘taste’ the female’s contact pheromones to make sure she is a suitable mate. If the chemicals are right, courtship may commence and, if courtship goes well, copulation will ensue. This process is verybrief and occurs immediately post-molt, while the female’s cuticle is new and soft. (Paragraph information from Fiedler GC, “Functional, simultaneous hermaphroditism in female-phase Lysmata amboinensis,” (Decapoda: Caridea: Hippolytidae), Pac Sci 52(2), 1998).
Scarlet Shrimp are indigenous to the tropical Indo-Pacific and Red Sea regions and can be seen at the Headwaters Science Center during regular hours and occasionally after dark being investigated by our night viewing crew. While they are most famous for their ability to clean fishes, we are about to discover (or perhaps dispel) that they are active nightly as scavengers feasting on things both dead and alive. So we are now forming nighttime search parties, donning LED flashlights and with the aid of an underwater camera connected to a video feed. We will venture into parts unknown and into places previously unseen and find out for you, our loyal readers, what it is that actually does go bump in the brine.