Inachus

Posted on March 9, 2024 by An Bollenessor under anemones, cnidarians, crustaceans, diving, Macro, Silver Steps

This seems like a familiar way to start a blog post but here I go again: ‘the weather has been terrible lately and I have not been in the water!’. March used to be my favourite time for snorkeling because the seaweeds look at their best, but the last three years it has been windy and wet, surely because of climate change…

To keep the blog going (a bit), I have dug out some images from a few dives last year featuring Inachus spider crabs. There are three species, I. phalangium, I. dorsettensis and I. leptochirus, which can be told apart by the arrangement of tubercules on their carapace, but these are often obscured by epiphyte growth, and so I am keeping it to Inachus sp. All species are associated with Snakelocks Anemone (Anemonia viridis) hosts. The photo above is taken using a weird ‘wide angle macro’ wetlens (INON UFL-M150 ZM80). This perspective always fascinated me but it is difficult to achieve. This lens does the job, although it is incredibly ‘soft’, especially around the edges. The close focusing also makes it difficult to direct the strobe light on the subject. So there is a tradeoff between getting the surroundings in view and sharpness. Below first some sharper shots using my 60mm macrolens, followed by some macro wide angle shots (they happen to be each of the different Anemonia colour morph):

I will leave you with the following interesting bit on the biology of these crabs by Diesel (Ethology, 1986):

I. phalangium females are site-constant, and live in the protection of one anemone or group. Males travel frequently between anemones harbouring females due to spawn; they copulate and guard the females until spawning, after which the male leaves again. A male operates in a patrol area containing 3-8 anemone groups and up to 8 females, visiting each female in turn repeatedly just before it is due to spawn. Patrol areas of different males may overlap, with resulting competition to fertilize a female’s next brood. Large males have higher reproductive success than small ones. Females live up to 8 months after the moult of puberty and hatch up to six broods, and males live up to 7 months as adults. A male could fertilize a calculated 26,000 eggs, whilst a female’s reproductive potential is ca. 4,200 eggs. Mortality risks are higher for males than for females, probably because of increased predation while leaving the protection of anemones in order to visit females. Males learn the positions of anemones harbouring females in their patrol areas, and when these are due to spawn. This allows a male to travel with a target and arrive punctually to fertilize the next brood due in his circuit. I. phalangium is the first marine invertebrate reported to use a “schedule” of localities and times for visiting prespawning females. In this way males minimize searching time and mortality risk, and maximize the number of broods fertilized.

Monster in a Barrel

Posted on November 14, 2023 by An Bollenessor under beach combing, crustaceans, Macro, tunicates

Last Sunday we made the trek to Sennen Cove beach in the far west of Cornwall. I have not been in the water for weeks due to the windy weather (and it might be a few weeks before conditions improve), so the only way to get my fix is by going beach combing… With strong westerlies, this spot jutting out into the Atlantic seemed a safe bet, although when we arrived the strandline appeared quite sparse and I did not have hope of finding much. A single find by my eagle-eyed son however made the trip all worth it!

The photos above show the amphipod Phronima sedentaria inside its home, a hollowed-out salp. These small crustaceans use their claws to carve a home out of their barrel-shaped gelatinous host. This offers protection, and a space to rear their young. They occur worldwide in the open sea and are believed to vertically migrate from depths up to a kilometer to the surface each night. Although it was still actively wriggling about, it was essentially doomed after being washed up, so it was taken back in a margarine container filled with seawater and handed over to David Fenwick (www.aphotomarine.com) for further examination. He made some excellent photos of it, making clear why it provided inspiration for the ‘Alien’ movie! As I suspected from the size, this was a female, and brood was found in the salp tunic as well.

These things have been found before a few times in the UK (in Sennen and in the Scillies) but not commonly (4 records on the NBN Atlas and 0 on iNaturalist). I have recorded mine on the latter database (which means it can make its way to NBN as well). Let’s see what else the sea throws up this winter!

Dog Whelks at Kynance Cove

Posted on July 16, 2023 by An Bollenessor under crustaceans, molluscs, mzuiko60mm

A trip to one of our favourite places today: Kynance Cove on the Lizard Peninsula. The weather was such that snorkeling was a big no, but after some wind and rain, luckily the sun came out for a bit (which it should, it is July!). I took some macro shots of the rocks at low tide using my new Cygnustech diffuser. This contraption makes the flash light much less harsh, and is pretty much essential when taking (non-natural light) macro shots. This is one of the best diffusers out there and I can highly recommended it (are plenty of reviews are available online). Some of the shots were taken with the Raynox DCR-250 macro attachment in front of the macro lens for a little bit of extra magnification.

Anyway, there is not a lot of animal diversity on this battered coast of green and red serpentine rock: barnacles, dog whelks, mussels and limpets mainly. Above a selection of photos highlighting some small Dog Whelks (Nucella lapillus). This predatory species can come in many more colour varieties than we found today (see here for example). The limpets are either the Common Limpet (Patella vulgata) or the Blackfooted Limpet (P. depressa); you need to be able to see the animal to be sure. The barnacles are Montagu’s Stellate Barnacles (Chthamalus montagui) (I might have this wrong; I must confess I never really gave barnacles the attention they deserve). Not too spectacular but you gotta try something when you cannot take photos underwater!

Tiny critters under rocks

Posted on July 1, 2023 by An Bollenessor under anemones, bryozoans, chitons, cnidarians, crustaceans, echinoderms, fish, Macro, molluscs, mzuiko60mm, rock pooling, snorkeling

When the viz is bad, I take my macrolens (sometimes with the Nauticam CMC-1 wetlens for a bit of extra magnification) out to the pools. Sometimes I stick to the surface of rocks and seaweeds (to look for stalked jellyfish for instance), but other times I turn over rocks under water to see what hides beneath. Quite a lot! There are larger animals, such as Topknots and different types of crabs (and Worm pipefish as pictured here) but mainly they are quite small (around a centimetre or even less). See the selection below (Tricolia, Bittium and Limacia were not from under rocks but I had to make the grid fit!).

Buoy Biodiversity

Posted on March 3, 2023 by An Bollenessor under bryozoans, buoys, crustaceans, fisheye, Flushing, invasive species, non-native species, Olympus OM-E-M1 Mark II, photography, seaweeds, snorkeling, sponges, tunicates, wide angle

A while ago I played around with taking pics of the underside of a buoy, which was fun, and so i wanted to practice this some more. My mistake the first time (see here) was to use a fast shutterspeed (the buoy was bobbing about after all) which made the water look unnaturally dark. I tried again this weekend and it went a bit better, although I already know I can improve things. This time I thought it would be nice to put some names to the amazing fouling biodiversity (I did this before for some seaweed images, see here). Crustaceans (tube-dwelling Jassa), Sponges, Bryozoans, Seaweeds but especially a lot of Tunicates (seasquirts; both solitary and colonial species). David Fenwick (of AphotoMarine fame) had a quick look to help with some IDs; there is a more there but this was not meant to be exhaustive. I have underlined species that are invasive. Anyway, I am sure I will post more of these types of images: the buoys are always there and these organisms do not swim off when you try to take a photo!

Muddy Adventures

Posted on November 17, 2021 by An Bollenessor under crustaceans, fish, mud flats

I went to the foreshore of our village with my son (9y) a week ago as he is always keen on some bare-handed eel catching. No pretty rock pools in this estuarine site, just mud, rubble, worms, oysters and sponges. Also Velvet Swimming Crabs (Necora puber) (named Devil Crabs locally as they are quite pinchy) and Rock Gobies (Gobius paganellus). I tried my hand at some TSCFWANF (Top Side Close Focus Wide Angle No Flash). This obviously resulted in a blown out sky. Next time I will try to use a home-made (milk container) softbox for a strobe to light up the foreground. Have not been in the water much, so long time no post. Hope to do some snorkelling or diving soon, weather permitting…

Rockpooling on St. Martins

Posted on May 1, 2021 by An Bollenessor under crustaceans, echinoderms, fish, rock pooling

Although St. Martins does not seem to have any rockpools, the beach that was nearest to us (called ‘Lawrences’) has a stretch of rocks lying on the sand that can be turned over at low tide, and so we did! A nice find was a small Sevenarmed Starfish Luidia ciliaris (these can grow up to half a meter across, although you will not find them that size in rockpools). We also found a Bootlace Worm Lineus longissimus, which is (probably) the longest animal on the planet. These nermertean worms secrete a powerful toxin in their mucus, but luckily for us it affects arthropods and not mammals. They are not very rare btw, I see them here in Flushing and Falmouth too. It was about 5 meters long (without stretching it), but they can grow ten times the size of this! In the second photo you can see it in its natural habitat, under a rock, with some photobombing crabs and worm pipefish. Another cool find was a juvenile Conger Eel Conger conger. Otherwise we found the usual suspects, lots of crabs and a bunch of fish, see for a small selection below.

More Macro 2

Posted on July 10, 2020 by An Bollenessor under crustaceans, echinoderms, molluscs

After half a year of strobe troubles (probably a mix of different faults, making it difficult to troubleshoot), I seem to finally have a working set-up again. Although the stalked jellyfish season passed me by, I am now raring to go. I went in today and yesterday and although I did not manage to spot any nudibranchs, there is always something to see. For instance, the White Tortoiseshell Limpet Tectura virginea above, which is very common on coralline algae. Below, the chiton Callochiton septemvalvis (stuck to the same rock as a week earlier), a tiny gastropod, probably Rissoa parva, a Cushion Star Asterina gibbosa, the Sea Ghurkin (a sea cucumber) Pawsonia saxicola and a baby squat lobster (<1 cm). There is currently a large influx of Crystal Jellies, which are not jellyfish but the medusa stage of hydrozoa. It probably is Aequorea vitrina. I have seen several being eaten by Snakelock anemones (slightly too large to take a good photo of with a macrolens). Below a detail. Finally, another, very different-looking, hydrozoan (I have to have a look at the biology of these things some time). It is Candelabrum cocksii, a species which was originally described based on specimens collected from this very beach. (I have posted a photo of this species before, but they look very blobby abovewater). The second pic is for scale. Hopefully a dive sometime soon!

Rockpooling

Posted on June 15, 2020 by An Bollenessor under crustaceans, echinoderms, molluscs, rock pooling, worms

I have not been in the water recently but went good oldfashioned rockpooling instead a week ago. No ‘lifers’ but there is always something interesting to see. For instance, my first albino cushion star (Asterina gibbosa). This small species (these individuals are only a little over a centimetre) is incredibly common here. Btw, I must confess this shot was staged, I placed these seastars together. Below, a Candy-striped flatworm (Prostheceraeus vittatus), also about a centimetre. Next, the Yellow-plumed or Side-gilled seaslug (Berthella plumula). Another common species but it is difficult to get a decent photo of this blob! This mollusc has an internal shell and, interestingly, glands that secrete sulphuric acid when it is attacked. You can see a little slug right beside it, maybe a juvenile Sea Lemon. Finally a photo that I had wanted to take for a while: can you spot the crabs? One of the most common invertebrates here is the Furrowed Crab or Montagu’s Crab Xantho incisus. Xantho species are known as Pebble Crabs which is the name I prefer; although highly variable in colouration they are very good at blending in amongst the pebbles! How many can you spot? There might be a stray Risso’s Crab Xantho pilipes in there as well, as they are quite similar (except for a fringe of hairs on the legs and carapace) and also common here. High time to have a look again underwater as well.

Macro Practice VI

Posted on December 8, 2019 by An Bollenessor under anemones, crustaceans, Macro, molluscs, mzuiko60mm, Olympus OM-D E-M5 Mark II, photography, snorkeling, worms

The tide was bad (i.e. low and too early to catch it on time), the water was cold and it was very windy but it was good to go for a dip this morning. I now have a different strobe arm which makes it easier to position my strobe, which has often been tricky. Time for some macro practice. The photos are not that special but I hope interesting enough for you blog readers! Above a Peacock worm Sabella pavonina sticking out of an abandoned piddock hole. Below a common Hermit crab Pagurus bernhardus, a Grey chiton Lepidochitona cinerea, a very small Dahlia anemone Urticina felina (note the warty, adhesive column) and some Daisy anemones Cereus pedunculatus.