News
Nudibranchs and the fabulous Spanish Dancer (Hexabranchus sanguineus)
Every good Dive Master/photographer has a problem. They must look after their clients while still taking pictures. They have no time to vary the depth of focus, no time to change camera settings; their dive clients must always come first. Colin Ogden of Amoray Diving at Sodwana Bay solved the problem by shooting nudibranchs, and his study of these amazing creatures has become a passion. I spent a spellbinding evening with him learning about them.
Nudibranchs come in brilliant colours, with fabulous markings, and they can vary in size from 1mm to 600mm. They are primarily carnivores and will eat hydroids and other species of nudibranchs but most of them feed on sponges; all of which are animals. A few will eat algae or seaweed. They feed where food is available so they frequent areas where coral growth is limited; even the cold Northern European waters harbour these colourful sea slugs and nudibranch hunting has become a global passion.
Nudibranch means exposed gills. Hexabranchus, for example, has six sets of exposed gills. All but two nudibranchs are called by their Latin names. The scientific community frowns on them being given common names so the study of these creatures is not for the faint-hearted.
Most of them breath using the exposed bunches of gills on their backs, and their sensual organs are contained in a pair of rhinophores, on the front of their heads. These look like horns. All are hermaphrodite, with both male and female sex organs, which are always on the right hand side, below the neck. These can be expelled to accommodate a large meal, and then re-ingested. All of them are poisonous to fish, and a single nudibranch can kill an entire aquarium full of fish if it becomes stressed and lets off a toxin. This occasionally benefits the palatable flatworm. He sometimes mimics the shape and rhinophores of the poisonous nudibranch, escaping predators and protecting himself.
There is even a species that farms algae in its gills. It is long and thin and has many sets of gills or cerata which he uses to collect algae. You will sometimes find it spread out along the top of the reef on a sunny day, cerata exposed to catch the sun so the algae will grow faster.
The spectacular Spanish Dancer (Hexabranchus sanguineus) is one of the very few nudibranchs that goes by its common name. They grow up to 600mm long, so are clearly identifiable. “They are nocturnal animals in our waters, so we rarely spot them in Sodwana Bay. However, we found two on the point of mating on Seven Mile in broad daylight. They lined up neck to neck, and then they exchanged sperm, fertilising each other. After five or six days each lays a long egg ribbon in a continuous circle, and you can see these on the reef looking like soft rosettes.”
They are normally pink, reddish or orange. These ribbons are preyed upon by other nudibranchs of the Favourinus family and the survivors hatch into tiny nudibranchs that look nothing like their imposing parents.
Other species lay egg ribbons that hatch into tiny veligers, which are a larval stage, and they can float around in the ocean, following currents for months on end. When they sense that there is a food source, they will descend onto the reef and metamorphose into small nudibranchs. The study of these creatures is still in its infancy, although some were described as early as the 1700s, but they are fascinating creatures, and there are still many unnamed and quite rare species in our waters. Once you know what you are looking for, you can find them almost everywhere.
Words: Jill Holloway
Pictures and technical data: Colin Ogden, Amoray Diving
Copyright Ocean Spirit 2017 – www.osdiving.com
Jake Davies boards Ghazala Explorer for an unforgettable Red Sea diving experience…
The second day’s diving was a day full of wreck diving at Abu Nuhas, which included the Chrisoula K, Carnatic, and Ghiannis D. The first dive of the day was onto the Chrisoula K, also known as the wreck of tiles. The 98m vessel remains largely intact where she was loaded with tiles which can be seen throughout the hold. The stern sits at 26m and the bow just below the surface. One of the highlights of the wreck is heading inside and seeing the workroom where the machinery used for cutting the tiles are perfectly intact. The bow provided some relaxing scenery as the bright sunlight highlighted the colours of the soft coral reef and the many reef fish.
Following breakfast, we then headed to the next wreck, which was the Carnatic. The Carnatic is an 89.9m sail steamer vessel that was built in Britain back in 1862. She ran aground on the reef back in 1869 and remains at 27m. At the time, she was carrying a range of items, including 40,000 sterling in gold. An impressive wreck where much of the superstructure remains, and the two large masts lay on the seafloor. The wooden ribs of the hull provide structures for lots of soft corals, and into the stern section, the light beams through, bouncing off the large shoals of glass fish that can be found using the structure as shelter from the larger predators that are found outside of the wreck.
The final wreck at Abu Nuhas was the Ghiannis D, originally called ‘Shoyo Maru,’ which was 99.5m long and built in Japan back in 1969 before becoming a Greek-registered cargo ship in 1980. The ship then ran aground on the reef on April 19th, 1983, and now sits at the bottom at a depth of 27m. Heading down the line, the stern of the ship remains in good condition compared to the rest of the hull. The highlight of the wreck, though, is heading into the stern section and down the flights of stairs to enter the engine room, which remains in good condition and is definitely worth exploring. After exploring the interior section of the ship, we then headed over to see the rest of the superstructure, where it’s particularly interesting to see the large table corals that have grown at the bow relatively quickly considering the date the ship sank. After surfacing and enjoying some afternoon snacks, we made sure everything was strapped down and secured as we would be heading north and crossing the Gulf of Suez, where the winds were still creating plenty of chop.
The next morning, it was a short hop to Ras Mohammed Nature Reserve for the next couple of days of diving. The 6am wake-up call came along with the briefing for the first site we would be diving, which was Shark & Yolanda. The low current conditions allowed us to start the dive at Anemone City, where we would drift along the steep, coral-filled wall. These dives involved drifts, as mooring in Ras Mohammed wasn’t allowed to protect the reefs. As a dive site, Shark & Yolanda is well-known and historically had a lot of sharks, but unfortunately not so many in recent years, especially not so early in the season. However, there was always a chance when looking out into the blue.
The gentle drift took us along the steep walls of the site, with plenty of anemone fish to be seen and a huge variety of corals. It wasn’t long into the dive before we were accompanied by a hawksbill turtle, who drifted with us between the two atolls before parting ways. Between the two reefs, the shallow patch with parts of coral heads surrounded by sand provided the chance to see a few blue-spotted stingrays that were mainly resting underneath the corals and are always a pleasure to see. With this being the morning dive, the early sunlight lit up the walls, providing tranquil moments. Looking out into the blue, there was very little to be seen, but a small shoal of batfish shimmering underneath the sunlight was a moment to capture as we watched them swim by as they watched us.
Towards the end of the dive, we stopped at the wreck of the Jolanda where the seafloor was scattered with toilets from the containers it was carrying. This provided a unique site to make a safety stop, which was also accompanied by a large barracuda slowly swimming by, along with a hawksbill turtle calmly swimming over the reef as the sun rays danced in the distance.
For the next dive, we headed north to the Strait of Tiran to explore the reefs situated between Tiran Island and Sharm El Sheik, which were named after the British divers who had found them. We started on Jackson before heading to Gordons Reef, where we also did the night dive. All the atolls at these sites provided stunning, bustling coral reefs close to the surface and steep walls to swim along, which always provided the opportunity to keep an eye out for some of the larger species that can be seen in the blue. Midwater around Jackson Reef was filled with red-toothed triggerfish and shoals of banner fish, which at times were so dense that you couldn’t see into the blue. Moments went by peacefully as we enjoyed the slow drift above the reef, watching these shoals swim around under the mid-afternoon sun.
The night dive at Gordon’s Reef was mainly among the stacks of corals surrounded by sand, which was great to explore under the darkness. After some time circling the corals, we came across what we were really hoping to find, and that was an octopus hunting on the reef. We spent the majority of the dive just watching it crawl among the reef, blending into its changing surroundings through changes in colour and skin texture. It’s always so fascinating and captivating to watch these incredibly intelligent animals, in awe of their ability to carry out these physical changes to perfectly blend into the reef. Before we knew it, it was time to head back to the boat to enjoy a well-deserved tasty dinner prepared by the talented chefs onboard.
Check in for the 3rd and final part of this series from Jake tomorrow!
To find out more about the Northern Red Sea reef and wrecks itineraries aboard Ghazala Explorer, or to book, contact Scuba Travel now:
Email: dive@scubatravel.com
Tel: +44 (0)1483 411590
Photos: Jake Davies / Avalon.Red
The Shark Trust is excited to announce that, for two more days only, all donations, large or small, will be doubled in the Big Give Green Match Fund!
Donate to Basking in Nature: Sighting Giants
The Shark Trust is hoping to raise £10k which will be doubled to £20k. This will go towards Basking in Nature: Sighting Giants. And they need YOUR help to reach they’re goal.
The Shark Trust’s citizen science project is to monitor and assess basking sharks through sightings; encouraging data collection, community engagement, and promoting nature accessibility. This initiative aims to enhance health and wellbeing by fostering a deeper connection with British Sharks.
Campaign Aims
- Increase citizen science reporting of Basking Sharks and other shark sightings to help inform shark and ray conservation.
- Provide educational talks about the diverse range of sharks and rays in British waters and accessible identification guides!
- Create engaging and fun information panels on how to ID the amazing sharks and rays we have on our doorstep! These can be used on coastal paths around the Southwest. With activities and information on how you can make a difference for sharks and rays!
- Promote mental wellbeing through increasing time in nature and discovering the wonders beneath the waves!
Donate, and double your impact. Click Here
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