Technological advances in photography have enabled photographers to document the extraordinary reproductive lives of tiny creatures found in the underwater world as never before, often leading to scientific discovery and understanding of little-known species. Underwater photographer Franco Tulli takes a closer look.
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For biologists, the study of reproductive dynamics is fundamental to the survival of every species and has always been one of the most important aspects to analyse and describe. However, it is also often the most challenging, due to the many difficulties encountered in direct observation. This is true for most living organisms, but even more so for beings that live and reproduce in aquatic habitats, except for the few species that can be observed in captivity in aquariums.
The marine world, and the aquatic world in general, is an environment that is unsuitable for human life. Therefore, several problems must be addressed and overcome in order to study it. It is only thanks to scuba diving and new, high-definition filming technologies that scientists have been able to begin observing and describing the sexual habits and reproductive characteristics of many marine creatures.
Thus, photography and filmmaking have not only become a form of visual art but also an extraordinary, fundamental tool for scientific research. The development of new techniques and increasingly sophisticated equipment has made it possible to study even the smallest marine creatures, measuring only a few millimetres.
Finally, we can appreciate the incredible colours and shapes that these small creatures’ eggs can take on. In some cases, they are true works of art, with perfect Giottesque circles, logarithmic spirals and beautiful concentric spheres in various shades and colours. We have also discovered the incredible ways in which some species incubate their eggs until they hatch.
Benefits of technological advances
The evolution of optical technologies, high-resolution sensors and controlled-spectrum LED lighting has made underwater photography a crucial scientific tool.
• High resolution enables microscopic details, such as reproductive organ structures and larval interactions, to be captured.
• Long exposure and time-lapse photography are essential for observing nocturnal reproductive behaviour and egg hatching cycles.
• Fluorescence and polarised light techniques have made transparent and biochemical structures, which were difficult to observe with the naked eye, visible.
• Using drones or miniaturised ROVs for underwater microphotography has made it possible to document behaviour in inaccessible or deep environments without disturbing the organisms.
Documenting reproduction and broods
Nudibranchs. Thanks to these techniques, it has been possible to document the mating ritual and egg-laying behaviour of Flabellina affinis, a common Mediterranean nudibranch, with detailed macro photographs showing its eggs forming fascinating translucent spirals. The same goes for its close relative, Flabellina rubrolineata, which lives mainly in warm seas and is one of the most beautiful and colourful Flabellina species.
The reproductive behaviour of Halgerda batangas, a hermaphroditic nudibranch, can be observed, where both partners fertilise each other, and the eggs are arranged in gelatinous spirals or ribbon-like veils, often near or above their prey.
Another species of hermaphroditic nudibranch, the Hypselodoris infucata, lays eggs in the shape of a white ribbon, resembling an extraordinary piece of knitting. They are laid in a suitable substrate, such as a tiny fragment of wood, in this case.
Fish. You can also observe the male yellow pygmy goby, Lubricogobius exiguus, a tiny fish, preparing a nest in a small cavity and courting the female to lay her eggs. The male then guards the eggs, fanning them with his fins to keep them oxygenated and protect them from mould and predators.
The eggs of Plagiotremus rhinorhynchos, a species of comb-toothed blenny found in the Indo-Pacific region, are bright red. They are laid inside abandoned polychaete worm tubes or in small crevices in coral rocks. Typically, it is the male that guards the nest after laying. He protects the eggs from predators and ensures water exchange (and therefore oxygenation) by moving his fins. During this phase, the male becomes extremely territorial and may attempt to “bite” even much larger intruders, including divers, using his sabre-like teeth.
The male Cheilodipterus macrodon, or large-toothed cardinal fish, certainly has one of the most unusual methods of incubating eggs. Despite its large teeth, the male manages to keep the eggs in its mouth until they hatch, removing them briefly to oxygenate them. However, female cardinalfish have their own concerns: The male is very likely to swallow some eggs by mistake or necessity. To avoid this, females have developed an ingenious strategy: They lay “dummy” eggs without a nucleus alongside the real ones. If the male swallows some, many of them will be lifeless.
Crustaceans. The extreme defence of the eggs by the female Lybia tessellata, also known as the boxer crab due to the way it wields small sea anemones like boxing gloves, is interesting to observe. (See this issue’s cover photo.)
Finally, who could forget Phycocaris simulans, a microscopic, highly camouflaged shrimp that is often mistaken for algae or debris? Measuring only 5mm, it is almost impossible to see with the naked eye, thanks to its great camouflage. It is one of the “ghosts” of the reef, and its eggs, which the female carries under her body, are practically invisible unless observed in photographs taken with powerful macro lenses.
Conclusion
These are just a few examples of what underwater photography and filming allow us to achieve today: making the invisible visible, thrilling the viewer, and documenting a fragile and extraordinary world that is often ignored because it is hidden on a microscopic scale! ■
