Tag Archives: #Amphipod thursday

Door #20 The Hitchhikers Guide to the Ocean

The sea is for most of its inhabitants a vast place where danger can get to you anywhere. This might be especially true when you are one of those small and mostly harmless species spending your life slowly swimming around, minding your own business (eating and reproducing), somewhere in the upper 200m or so of water. Because there are many big-mouthed and possibly big eyed animals out there that think you might be one of the best things there is to eat.

Hyperiella antarctica with Spongiobranchaea australis. Photo: C Havermans, AWI.

For the small pelagic (living in the open ocean and not close to the sea floor) amphipods in the suborder Hyperiidea this is one of the dangers of everyday life. The genus Hyperiella can be found in the Southern Ocean, and one of their main predators are the icefishes (Nototheniidae). So what do you do when you are a small and quite tasty animal that is not a very fast swimmer and there are a lot of fishes out there to eat you?

Don´t panic!

Hyperiella antarctica with Spongiobranchaea australis (a and b) and Hyperiella dilatata with Clione limacina antarctica (c). Figure 2 Havermans et al 2018.

Two of the three Hyperiella-species have found a quite ingenious solution. They hitchhike with a group of other small slow-swimming pelagic animals – pteropods. Pteropods (from the greek “wing-foot”) are sea snails (gastropods). Hyperiella australis pics up a life with Spongiobranchaea australis, and Hyperiella dilatata hangs out with Clione limacina antarctica. Both pteropods are from the group we call Sea Angels (Gymnosomata), and in a way they are saving angels for the amphipods: the ice fish don´t eat these strange couples. Why?

It seems the pteropods have developed a chemical protection against predation. They obviously taste extremely bad, for observations of icefish trying to eat the hitchhiking amphipods together with the pteropods result in them both being spit out again. Most times, the fish would see what it thought was good food, and then swim away when they discovered what they were almost eating. Not so very strange, then, that Hyperiella are holding on to their colleagues for their life!

 

 

Clione limacina antarctica. Photo C Havermans, AWI.

It might not be hitchhiking after all, but rather kidnapping – or brute force. The amphipods hold on to the pteropods with their to-three hindmost pairs of legs, and keep the sea angel on their back – much like a backpack. Observations are that they are repositioning them there all the time – almost like kids running with bumpy backpacks on the way to school. They don´t even let go when the researchers preserve them!

Hyperiella antarctica with Spongiobranchaea australis backpack. Photo: C Havermans, AWI

What this treatment do to the pteropods we still don´t know. But it does not seem they are able to eat very much when being held hostage as chemical defence-backpacks. That may not be the biggest problem in a short time-scale – their Arctic relatives have been shown to survive almost a year without food. What happens when they really get hungry we do not know. The amphipods are still able to feed, even though the pteropods can be up to 50% of the amphipod size. Maybe the pteropods do some of the swimming for the amphipods?

This behaviour is much more common close to the coast than in the open sea: close to the McMurdo area, 75% of the Hyperiella were seen hitching with a pteropod. Now we know that this pairing can be found in the open sea, and maybe is it more common that we think. It is not the first thing we have looked for so far when examining samples. When the University Museum of Bergen joins the Norwegian Polar Institute and the Institute of Marine Research to the Southern Ocean in the austral autumn this coming March, we will make a special effort to search for such collaborators.

Anne Helene


Literature

Havermans C, Hagen W, Zeidler W, Held C, Auel H 2018. A survival pack for escaping predation in the open ocean: amphipod-pteropod associations in the Southern Ocean. Marine Biodiversity https://doi.org/10.1007/s12526-018-0916-3

McClintock JB, Janssen J 1990. Pteropod abduction as a chemical defence in a pelagic Antarctic amphipod. Nature 346:424-426.

 

 

Door #13: The story you can find in a picture…

It is often said that a picture is worth a thousand words. We use both drawings and photos (and sometimes even films) when we are describing species, and without these illustrations, we would often have to make guesses as to what the author meant when describing the morphology of the species in interest.

Generally, the old literature did not make as much room for illustrations as we have the possibility to do today – the printing often needed entire plates (pages) produced much in the same way an artist still produces a carved or engraved print today – and when there is a plate in an old publication it quite often is a piece of art. But – the plates (figure-pages) were expensive to print (even more than the text-pages), and thus often limited to the bare necessities.

There are exceptions! C. Spence Bate and J. O. Westwood (both with so many letters behind their names that they included “etc” at the front page) commissioned J van Voorst in London to print  their book “ A History of the British Sessile-Eyed Crustacea” in two volumes. The first came in 1863, the second in 1868.

And it is enjoyable reading. “Sessile-eyed” crustaceans are explained as those crustaceans who do not have stalked eyes (as for instance the crabs and shrimp have) and it was used to classify crustaceans since Leach in 1814 named the gruop “Edriophthalma” (sessile-eyed in greek). This group included Isopods and Amphipods – but the discussion was still going strong about what taxa should be included in these groups, and how they were “connected” with the other crustaceans. The gentlemen Bate and Westwood decided to describe and discuss each of the species they knew of as sessile-eyed in Britain. This would be a basis for the further discussions on higher groupings. Interspersed in the text are figures of the species and special morphological structures they are discussing, making the book easy to follow and understand. An introduction on the general morphology, physiology, reproductive biology and geographical distribution of the sessile-eyed crustaceans, the rest of part 1 discusses the Amphipoda.

They really mention every species they have come across – ever – from anywhere in Britain. Sometimes that may be one single specimen of what they think must be a new genus and species (and that seems to have been forgotten later),  and in addition to the drawings of the morphology they add a drawing of the location where it was found.

It is at the end of volume 1 that we come to the picture that captures my imagination the most. Under the discussion of Corophium longicorne  (accepted name: Corophium volutator) they discuss the extraordinary strong second antennae of the species:

“The inferior antennas are very powerful, and in the male are longer than the animal itself; the pentultimate joint of the peduncle being armed upon the inferior distal extremity with a strong tooth, which appears to assist considerably in holding any object when the extremity of the antennae is folded upon itself; this organ appearing to possess the strongest prehensile power, and being no doubt used as a weapon of offence in its battles with other animals in its struggle for existence.”

Corophium are known from sandy and muddy shores – where they “dwell in small tubular galleries, excavated in the mud, over which the tide flows and ebbs”.  They go on to discuss their ecology – as predators of other shore-living invertebrates.

They cite “Rambles of a Naturalist” of Quaterfages on the feeding habits of this fierce amphipod:
at about the end of April they come from the open sea in myriads (they are called Pernis by the fishermen of the coast of Saintoge) to wage war with the annelids, which they entirely destroy before the end of May; they then attack the mollusca and fish all through summer, and disappear in a single night about the end of October, and return again the following year.

Bate and Westwood do not follow up the story from Quaterfages with any other documentation, but they ask their readers to send them more data if they have. Corophium volutator was described already in 1766 by Pallas, and is found on sandy or muddy beaches all around the North Sea. Maybe you will see a battle between a Corophium and an annelid? All later research into this species and the close group of related amphipods show us that these are detrivorous (eating organic matter from the mud where it lives). We might never know what inspired the fishermen that Quaterfages talked to. But if you see something like this, we would really like to know!

-Anne Helene

Literature:
Bate CS, Westwood JO.1863. A history of the British Sessile-Eyed Crustacea. Part 1. John van Voorst, London (Paternoster Row). 580 pp.

Door # 6: The key to the question

We often say that without knowing the species you examine, you really can’t know a lot about whatever it is you are examining. But how do you get from knowing for example “this is an amphipod” to knowing “this is Amphilochoides serratipes”?

Three different Amphilochidae from Iceland

Most researchers would usually stop at the “this is an amphipod”-stage, and many specialists  would call it a day at “this amphipod belongs to the familily Amphilochidae”. but then there are the one or two researchers who have gone on to specialise in this family (I think there are three of us in the world at the moment).

But finally – those days are over!
As a special gift on this Nicholaus-day when all German colleagues get a special gift from St Nicholaus (who is Father Christmas) we present to all of you – regardless of nationality or faith:

The interactive and illustrated key to the NorthEast Atlantic species of Amphilochidae

The key is a product of a collaboration between the NorAmph-project and the German-lead IceAGE project that examines benthic animals around Iceland, and the technical production and web-hosting of the key is from the Norwegian Taxonomy Initiative (Artsprosjekt) (who – we have to say – also have financed the NorAmph-project!) Hurrah for a great collaboration!

Figure 14 from Tandberg et al

You might still wonder what an Amphilochid amphipod is?

The family Amphilochidae are amphipods that are quite small (1-6mm in length) and quite stout. They are not extremely good swimmers, though much of that can be from their small size – and from their short appendages. They can be found all over the world, and are common at many depths in our cold waters. Even though they are small and easily overlooked, they sometimes occur in relatively large numbers, and can contribute significantly to both the biomass and diversity of a sample. They have been found on hydrothermal vents at the southern part of the Mid-Atlantic ridge, and some have been found as loose associates of other invertebrates.

Also – they are quite cute, don’t you think?  Good luck with the identification!

-Anne Helene

Literature:

Brix S et. al. 2018. Amphipod family distributions around Iceland. ZooKeys 731: 1-53. doi: 10.3897/zookeys.731.19854

Tandberg AHS, Vader W 2018. On a new species of Amphilochus from deep and cold Atlantic waters, with a note on the genus Amphilochopsis (Amphipoda, Gammaridea; Amphilochidae). ZooKeys 731: 103-134. doi: 10.3897/zookeys.731.19899