Stomatopod Biology and Ecology Principal Investigator: Roy L. Caldwell, Department of Integrative Biology, University of California, Berkley

See Dr. Caldwell's August 1999 Mission Journal for spectacular pictures of stomatopods.

Stomatopod crustaceans are a major component of Florida offshore ecosystems, but their biology is poorly known. Interestingly, they have one of the most highly developed visual systems in the animal kingdom, and not surprisingly many aspects of the daily light cycle influence important aspects of their biology. For example, cycles of day and night control when they feed, affect reproductive periods, and direct larval dispersal and recruitment of young juveniles to the reef. The physical properties and intensity of light also dictate how and when animals can use visual signals to communicate. In a previous Aquarius mission (August, 1999) we measured the physical characteristics of the light environment (intensity, quality of light including polarized light) around the underwater laboratory, and investigated the use of color as visual signals by stomatopods. In this Aquarius mission additional light measurements will be collected and several interesting discoveries made on the previous mission involving stomatopod ecology, communication and reproductive behavior, will be studied in more detail. New studies on the larval biology and recruitment juvenile stomatopods will be started, and because stomatopods are sensitive to environmental disturbance we will start a monitoring program to evaluate their abundance and distribution. The monitoring program will help test whether or not stomatopods can be used as "indicator species" of environment change in south Florida.

The research team includes Roy Caldwell as the principal investigator (stomatopod behavior), Tom Cronin (sensory ecology), Mark Erdmann (reef conservation and crustacean biology) and Pamela Jutte (stomatopod larvae). Additional team members include Alex Cheroske (stomatopod vision), Helen Fox (reef restoration and recruitment), and Kirsten Lindstrom (stomatopod larvae).

There are several major mission objectives.

Objective I. Physical Measurements of the Light Environment. During previous Aquarius missions, light measurements were made during the day, particularly with respect to variation in the spectrum (color) and intensity, as well as reflectance from local reefs. In this mission, these measurements will be extended to focus on how the light environment influences behavior in stomatopods. The transmission properties of polarized light in the vicinity of the Aquarius habitat throughout the day and in different water quality conditions will be measured to establish the potential for polarized-light to affect signaling by stomatopods and other marine animals.

Objective II. Stomatopod Biology. Conch Reef is inhabited by a diversity of stomatopod crustaceans, many found only at depths greater than 15 meters. Specific projects include:

A. Polarized visual signals in Odontodactylus havanensis. During a previous Aquarius mission we discovered that O. havanensis adults (collected during our 1999 Aquarius mission) have dramatic polarized light patterns on their antennal scales and uropods. Such extensive and strongly polarized signals appear unique among animals (with the possible exception of a few cephalopods). Coupled with the recent demonstration that Odontodactylus can actually detect polarized signals with their specialized eyes, we now have the opportunity to study the function and relevance of these signals in the field. Nothing is known about communication or social behavior in this group of organisms. Therefore, we will monitor activity at and around burrows (stomatopods dig deep burrows in the sands surrounding Aquarius) using video cameras equipped with polarizing filters, and we will make observations and conduct experiments of behavior while on scuba. We will also collect about a dozen adult male and female O. havanensis for laboratory studies in Berkeley looking specifically at sexual recognition. Females are sexually receptive only when they have developed ova. Unfortunately, the chances of finding several receptive females in the field are low. In the laboratory, however, females can be maintained until they become receptive.

B. Monogamous mating systems in lysiosquillid stomatopods. We previously discovered that the adults of several species in the family Lysiosquillidae live in what appear to be monogamous pairs. During our last mission, four lysiosquilloids were found within a few meters of the base of Aquarius including two undescribed species of Nannosquilla. We managed to establish a breeding pair of one of the new Nannosquilla species in our home laboratory and have followed their behavior (in a cut-away burrow) for the last six months. Not only do the male and female remain together in the burrow, but the male participates in caring for the eggs. Such biparental care is unknown in crustaceans and is extremely rare in invertebrates. We plan to carefully excavate entire burrow systems to collect all residents and then conduct paternity analyses on any eggs found (using genetic techniques). In addition, we will use epoxy resins to cast selected burrow systems to see if burrows are connected. This should allow us to determine if these are truly monogamous pairs or if, as is known for some "monogamous" vertebrates, cheating exists between pairs or individuals who sneak into burrows through connecting tunnels.

Objective III. Larval biology. Almost nothing is known about the behavior of larval stomatopods. In fact, for most species, we don't even know which larval form develops into which adult. At night, because it is well lit, Aquarius attracts large numbers of stomatopod larvae, many more than at the surface. This provides an unique opportunity to identify larvae and observe their behavior.

A. Larval identification. Many stomatopod early and late stage larvae, particularly those just hatching and those ready to settle, are attracted to lights at night. They are easily collected using a flashlight and hand net. We will collect as many forms of stomatopod larvae as possible (during the last mission we saw at least a dozen) and preserve them for genetic analysis. Using a library of previously collected specimens from the Caribbean and western Atlantic, we should be able to match larvae and adults as to species. Some individuals will also be passed on to the surface team for rearing. Each larval growth stage will be preserved and figured and at the end of the mission the postlarvae will be taken to Berkeley where we have had success rearing juveniles to a size where they can be identified morphologically. This will allow use to begin to compile a key to the stomatopod larvae and postlarvae of the region.

B. Larval behavior. It is becoming increasingly obvious that adult abundance, distribution and population structure is strongly influenced by larval dispersal and recruitment behavior. Unfortunately, such information on larval biology is non-existent for most marine invertebrates. This is certainly the case for stomatopods. We have almost no information on where and for how long the larvae of any stomatopod species remain in the plankton or on their dispersal and foraging behavior. A major objective of the proposed mission will be to begin to rectify this situation. We will sample various habitats throughout the day and night to determine what stomatopod larvae are present. Perhaps the most unusual aspect of the proposed mission will be attempts to follow free-swimming larvae for as long as possible to observe their behavior and to determine at what depth and how far they travel. This technique is being successfully employed to study settling behavior of larval reef fish. Large, late stage stomatopod larvae (Lysiosquillina glabriuscula and Alima sp.?) will be captured at a night light, marked with a reflective spot, and released at dawn. These larvae are 2-3 cm in length, swim at moderate speed and should be relatively easy to follow without interfering with their behavior. Following larvae may prove difficult or even impossible, but the potential rewards are great and we think it is worth the attempt.

Objective IV. Stomatopod distribution and abundance. During our last mission, we obtained qualitative information on what species occur in the habitats around Aquarius, but no attempt was made to quantify species composition or abundances. Previous work by our team in Panama and Indonesia has shown that stomatopods are excellent bioindicator species responding quickly to environmental perturbations. We propose to conduct quantitative surveys that will provide information on current stomatopod distribution and abundance that will aid in interpreting our other projects, but which also could be used as the basis for future monitoring programs.

A. Adult densities. We will quantify burrowing stomatopod densities by recording burrow entrances along transects that extend away from the habitat and at more distant locations. The shape and size of burrow entrances provides information on both the species and size of the residents. Determining stomatopod densities will be important in interpreting our data on mating systems and may prove useful to other behavioral and ecological studies conducted near Aquarius.

B. Larval recruitment. We will directly measure recruitment at several locations by sieving sediment to collect postlarvae and juveniles. This can be done by placing a clear cover on the top of a sieve and then collecting animals that remain after the sand has been processed. Alternatively, sand can be sealed in plastic bags for transport and processing at the surface.