An Overview of Jim Morin's Research:

Over the years most of my research has been devoted toward understanding the mechanisms, functions and evolution of light emission by organisms. This emphasis has been augmented by my fascination with marine invertebrates and their interactions, particularly at night. My interests are on the organisms themselves, not technology per se. I have consistently taken a broad-based approach that examines all aspects of luminescence from chemistry to ecology and evolution. I and my students have done field studies, often underwater in the dark of night, off all the continents and major oceans. We have worked on a variety of organisms including bacteria, cnidarians, ctenophores, polychaetes, ophiuroids, crustaceans and fishes. My current research focuses on luminescent behavior in ostracode crustaceans and photocyte function in hydrozoans.

Courtship and Antipredatory Signals in Ostracode Crustaceans:

I have been working on luminescent ostracodes since 1980 when I first described their courtship displays above St Croix reefs at dusk. Ostracode courtship displays over Caribbean reefs are among the most spectacular natural light shows ever reported. Males of the sesame seed-sized crustaceans leave the reef and enter the water column about 35-50 minutes post-sunset if there is no moon in the sky or just post moon-set if the moon is up at sunset. Males secrete a substrate (cypridinid luciferin, a tripeptide) from one set of tiny nozzles on their upper lips, an enzyme (cypridinid luciferase, a protein) from another set lateral to them, and mucous from a third set. These mix in the water to produce a sustained, discrete pulse of bright blue light. They repeat this as they swim to produce a species-specific, coded display.

Courtship Displays: Each species' display is unique. Most species display for less than an hour each night, a few go longer. Male ostracodes swim rapidly -- they cover the equivalent of one and a half football fields in a second for you or me -- while they're squirting their coded pattern of luminescence in their wake. Some species' displays are just a few cm long while others may extend many meters; some move downwards in the water column, others upwards, and still others laterally or obliquely. Some make relatively long-lasting pulses of luminescence (10-20sec) while others are like little strobe lights (50-100msec). Some even swim and display in formation. As many as 7 or 8 different species from up to 4 genera may display in the same vicinity; most show microhabitat specificity and specific display periods. They occur throughout the Caribbean and each island has different species from most others; there is high endemism. We have discovered over 60 species so far in the Caribbean but there are certainly many more. The displays appear to be restricted to the Caribbean and have not been observed anywhere else.

The distinctive patterns produced by male ostracodes attract females of the appropriate species. Females can luminesce to deter predators but do not signal during courtship. These ostracodes practice internal fertilization, and once having mated, the females go off to incubate their embryos (which also can luminesce) inside their bivalved shells; they apparently do not mate again. Thus mating removes so many eligible females from the mating pool that the male-to-female operational sex ratio becomes highly skewed toward males (>>100:1). Thus males compete heavily for scarce sexually-receptive females and the luminescent display come under strong sexual selection. Males often compete by signaling in synchrony and also other males may follow along as "silent," non-signaling males that try to sneak copulations.

Predator Deterrence: A display would seem to make males vulnerable to predators, but it does not. Instead, these ostracodes produce another kind of signal if they are attacked by a predator such as a nocturnal planktivore (e.g. cardinal fish or silverside). If eaten they produce an extensive pulse of light that glows for about a minute and silhouettes the whole fish. The ostracode is usually regurgitated. The luminescence sometimes attracts the predators' predators (jacks and snappers), which consumes the threat to the ostracode. This is the so-called "burglar-alarm effect." Thus it is dangerous for planktivores to eat these ostracodes and predators seem only to do so by mistake just prior to the start of the display period; it does not occur during the displays. As a result, ostracodes enjoy immunity from predation during their very obvious visual displays.

Evolution, Systematics and Phylogenetics of Cypridinid Ostracodes:

From recording the details of each species' luminescent display and making collections of the displaying individuals, we have been able to identify, describe and determine the phylogenetic relationships of the myriad of luminescent ostracode species in the Caribbean. The description of new species is based on detailed morphological studies. Determining the evolutionary relationships among these and other species within the family Cypridinidae is based on both morphological and molecular phylogenetics. From these analyses we have been able to determine the sequence of evolutionary events that has led to the complex courtship displays seen in this remarkable group. This has been a first for any luminescent organism. We now know more about the entire luminescent system (from biochemical mechanisms to evolutionary origins) of ostracodes than any luminescent system including the bacteria and fireflies.

Mechanisms and Function of Luminescence in Marine Organisms, particularly Cnidarians:

During my early years at UCLA, I and my students examined more closely the ecological and behavioral roles that luminescence plays in the lives of marine organisms, especially brittle stars, sea pens, hydrozoans, scale worms and some fishes. We began studying the predators of luminescent species and how they react to emitted light. Because field work on luminescence is arduous and stressful, few individuals have chosen to examine bioluminescence in situ under ambient conditions. I have spent endless nights underwater in many parts of the world watching a plethora of types of luminescence. We now have a fundamental understanding of the integration of light emission in the lives of marine organisms. These observations clearly lead to the conclusion that light emission has many direct as well as indirect effects on a host of marine communities.

My early work also focused on how primitive nervous systems control light emission and other behaviors in hydrozoans. During that work I made the initial discoveries of an important energy transfer protein (the green fluorescent protein [GFP]) that has become a field unto itself in genetics, cell biology and development where it is being used as a vital reporter molecule in gene expression. With the aid of fluorescence microscopy, GFP acts as a natural reporter for the presence of photocytes in most hydrozoan and anthozoan cnidarians. By combining this work with our findings of nocturnal luminescent functions, I and my students are currently using this technique to examine developmental questions in these colonial organisms and also the plasticity of the luminescent system to variations in the abundance of visually-orienting, nocturnal aggressors.

Luminescent Flashlight Fishes:

My studies of flashlight fishes in the Red Sea, Indonesia, the Philippines and the Caribbean, and ponyfishes in Indonesia and the Philippines have shown that, in different situations, they use their light for attracting and detecting prey, deterring predators, and intraspecific communication for both forming schools and sexual pair bonds. Because both these groups of fishes produce light by virtue of a mutualistic relationship with enteric luminescent bacteria, I became interested in the details of this relationship in these and other fishes. I and my students have examined the behavioral and ecological aspects of the relationship, the microarchitecture of the light organs, the physiological and morphological changes that occurred in both partners from the association, and the ways the light was expressed.

Other studies:

I maintain a strong interest in the overall natural history of marine organisms. While studying luminescent organisms in their natural communities, I and several students began a long-term study of a shallow subtidal sand community and its dynamics. This community is dominated by sand dollars and we have an impressive data base concerning their population dynamics, feeding biology and reproductive patterns. This approach has led to some novel insights into foraging and antipredatory behavior in crepuscularly and nocturnally active organisms.