California Smoothtongue, Leuroglossus stilbius
The California Smoothtongue, Leuroglossus stilbius, whose common Spanish name is lengualisa californiana, is a member of the Pencilsmelt or Microstomatidae Family, known collectively as peces boquita in Mexico. Their common name is derived from their relative absence of teeth. Globally, there are only three species in the genus Leuroglossus with the species described being the only one found in Mexican waters of the Pacific.
The California Smoothtongues have slender and laterally compressed bodies with a depth that is 20 to 22% of standard length. Their body tapers toward the tail which has a wide base. They are silvery to brassy in color being darker ventrally and having pale to transparent fins. Their head has a pointed snout that is greater in length than their eye diameter. Their anal fin has 11 to 14 rays; their caudal fin is deeply forked; their dorsal fin is set well back on the body and has 9 to 12 rays; their small pectoral fins are located ventrally and have eight or nine rays; and their pelvic fins have eight to ten rays. They have 21 to 26 gill rakers.
The California Smoothtongues are a bathypelagic species found from the surface to depths of 2,800 feet. They reach a maximum length of 17.2 cm (6.8 inches). They are vertical migrators that move to the surface at night to feed and return to the ocean depths for protection during the day. They consume copepods, larvaceans, ostracods, salps, and fish eggs. In turn they provide a valuable food source for a wide variety of marine life including birds, dolphins, the Humboldt Squid, sea lions, and numerous fish. They have a double-chambered stomach, the first chamber having a lining with a black pigment that prevents the light from digested luminescent prey from being visible from the exterior. Reproduction is oviparous with planktonic eggs and larvae. They are believed to have a lifespan of five years. They are a poorly studied species and very little is known about their behavioral patterns.
In Mexican waters the California Smoothtongues are found in all waters of the Pacific with the exception of along the coast of the mainland south to Guatemala.
The California Smoothtongue is straightforward to identify and cannot be confused with any other species.
The California Smoothtongue are a small and very deep-water species that are abundant but seldom seen by humans. They are of limited interest to most. From a conservation perspective, they are currently considered of Least Concern.
California Smoothtongue, Leuroglossus stilbius. Fish collected in a deep water trawl net off Point Loma, California, August 2010. Length: 10.5 cm (4.1 inches). Collection and identification courtesy of H.J. Walker, Jr., Scripps Institution of Oceanography, La Jolla, CA.