The Deep Reef Observation Project (DROP) is a Smithsonian initiative in the island of Curaçao which began in 2011 with support from the Consortium for Understanding and Sustaining a Biodiverse Planet. I have been studying hermit crabs and other crabs that have been filmed or photographed using a manned submersible named Curasub, which can dive down to 300 m in depth. A rich and spectacularly colored fauna of hermit crabs, never seen before alive in their original habitats, has been discovered.
The DROP program is providing an extraordinary and unique opportunity for taxonomists like me to make direct, live observations of many species that have previously been known exclusively from preserved and colorless specimens in museum collections. The study of these samples, such as those of Pylopagurus discoidalis shown here, is serving to expand and complement collaborative studies on hermit crabs systematic from the Caribbean at large. The specimens are being used to obtain molecular data such as barcodes and DNA sequences, which will be useful for biodiversity assessments, long-term faunal monitoring, and evolutionary studies.
With the theme of the exotic species living in the Oosterschelde (the Netherlands), after the success of the ”Gorishoek excursion” (see: LINK) and the great stories we’ve heard about Yerseke made Frans de Jong and I decided to go on excursion to Yerseke on July 22th, 2012.
After meeting each other on the parking lot next of Youth Centre ”De Zealte” on the Korringaweg we looked for a suitable location to go down of the sea dyke. When we arrived without sliding at the foot of the dyke, and skimmed the inventarisation area, it seemed pretty similar to Gorishoek. Only it is much dirtier and full of blue mussels (Mytilus edulis). If you look to the ground you can easily pick empty shells of the common limpet (Patella vulgata) and single valves of The queen scallop (Aequipecten opercularis). Still no Atlantic oyster drill (Urosalpinx cinerea) of the bristly crab (Pilumnus hirtellus), species for which we actually did come to Yerseke. A few meters to the water, in some pools, I saw impressive big examples of the
some of them are near the 3 centimetres. During the return to our car we saw a nice crab, not a bristly crab, but I think it is a brush-clawed shore crab (Hemigrapsus takanoi), an exotic species that repulse our aboriginal crabs, but I’m not sure about the determination. Collected that one and went to the car, and on to the other search spot near Yerseke …
… or not. The places we wanted to visit were not hardly accessible by car. If we would have walked, we would have risked missing the low tide for
the breakwaters. After a short discussion we decided to go to work island Neeltje Jans and continue our search on the North sea side of the island. There we only saw much common limpets, flat periwinkles (Littorina fabilis), a large grey top shell (Gibbula cineraria), some pullet carpet shells (Venerupis senegalensis), one living dog whelk (Nucella lapillus), a nice coloured crab, I think it is Japanese shore crab (Hemigrapsus sanguineus) and some smaller shells of the Cuttlefish (Sepia officinalis) at the south of the island.
Afterwards we enjoyed a delicious barbecue at the campsite where I stayed. Altogether it was not a bad day.
Bruyne, R.H. de (2004): Veldgids Schelpen. — KNNV Uitgeverij, 234 pp.
It’s Sunday morning 6. may, 9 o’clock in the morning. A group of 7 people walk from the parking behind restaurant ‘de Zeester’ to the already dry mud banks of the Oosterschelde. Full of hope we defy the cold (8°C) on our way to our collecting spot. One thing catches the eye immediately, everywhere we look lie empty doublets of Venerupis philippinarum (Adams & Reeve, 1850). We were already informed in advance about this phenomenon by Frans de Jong, who was there a month ago (see: LINK). We don’t know the reason of the mass beaching of these shells but it was a good start of the day. Between the V. philippinarum we found a striking number of recent single valves of Glycymeris glycymeris (Linnaeus, 1758) a species with the Channel for it northernmost limit of its range. But there lives a small population in the Oyster wells of Yerseke. After collecting a sample of both exotic species, we walk further.
Then we come to the place with the species that Gorishoek is famous for. After turning some stones we found many living Urosalpinx cinerea (Say, 1822) and fewer but still large parties of Ocenebra inornata (Récluz, 1851). The nice yellow eggs are a sight for sore eyes and very fascinating. Between these two species of Muricidae are lots of living Littorina littorea (Linnaeus, 1758), Gibbula cineraria (Linnaeus, 1758) and Patella vulgata Linnaeus, 1758. Of all the five species I collect some. In the next month I try to prepare the radula of my collected P. Vulgata.
A little further we come to an area with Nucella lapillus (Linnaeus, 1758). This is the species of Muricidae which belongs to this place but it is slowly supplanted by exotic species of that family. But there is some hope. This species has laid eggs too, so we can enjoy the beauty of this animal for one more generation. We hope it will be more. I’ve also found an unusually big specimen of N. lapillus, which was around 50mm.
Another eyecatcher are the lots of empty shells of P. vulgata which are spread throughout the searched area. I’ve collected around 30 empty shells. That’s very different from the small samples of empty shells I’ve collected at Hoek van Holland and Borssele. Also there laid many single valves of Aequipecten opercularis (Linnaeus, 1758) and doublets of Ostrea edulis Linnaeus, 1758. So that is a indication that Crassostrea gigas (Thunberg, 1793) has not completely displaced O. edulis. But I don’t think it could be saved. Maybe they were the last Dutch doublets of the shell I’ll see in my life.
Some other interesting finds are a single valve of Arctica islandica (Linnaeus, 1767) and that, at the end of the Oosterschelde looks like a great specimen. A recent right valve of Pecten maximus (Linnaeus, 1758) with a size of 115mm is uncommon, which lives on higher depths in the Northsea. Shells of of adult animals beach infrequently.
After some two hours searching, we return to the cars. Over a cup of tea we talk about our finds and then we leave the sea and go back home. When I arrived home I inspectedt my shells. And found on the shells three Lepidochitona cinerea (Linnaeus, 1767). I’ve searched for that species there but I haven’t found it.
Later I will attach a full species list of this day.
Bruyne, R.H. de (2004): Veldgids Schelpen. — KNNV Uitgeverij, 234 pp.
Faasse, M.A. & Ligthart, A.H.M. (2007): The American oyster drill, Urosalpinx cinerea (Say, 1822), introduced to The Netherlands – increased risks after ban on TBT? — Aquatic Invasions 2(4): 402-406
Faasse, M.A. & Ligthart, A.H.M. (2009): American (Urosalpinx cinerea) and Japanese oyster drill (Ocinebrellus inornatus) (Gastropoda: Muricidae) flourish near shellfish culture plots in The Netherlands. — Aquatic Invasions 4(2): 321-326