Surtsey - The Volcanho Island, Iceland. Insects.

Our Beautiful World

The volcano island: Surtsey, Iceland

INSECTS

	*Plants*
	Birds
	Bird migration
	*Sealife*
	Fossils on Surtsey
	How life developed
	*The eruption*
	*Picture-review*

Sample of different species within Arthropods.
Arthropods are animal with external skeletons. They include Insects, Arachnids (spiders),
Crustaceans (Crabs, Lobsters, etc.) and the extinct Trilobites.
From the excellent page of Arthropod.net (not valid as per Sept. 2010)

Believe it or no, but the population on Surtsey today has passed 1 million inhabitants.
Of course, not all individualls are visuable to the human eye at first. Some of those individuals
living on Surtsey you can only see through a microscope. But they are still there.

Some of them are bigger. So lets have a look at them first.

A collembolan. More info at:
http://research.amnh.org/grants/REUHTML01/james/sld003.htm

The first collembolans were found on the shore in 1967 and apparently they had floated to
the island on the sea. Since then, new collembolans have arrived each year.. All collembolans
collected in the periode from 1967 to 1972 were found in connection with the shore.
However, in 1976 collembolans were for the first time found in mossy vegetation on the
southern lava fields far from the shore.

As per 1978 16 species of collembolans had been found on Surtsey, and it is presumed that
they all have arrived either by the sea, the birds or the wind.

Collembolans together with the mites, enchytraeids and nematodes constitute the soil
meso-fauna. Collembolans live in the air-filled pore system of the soil and cannot
make their own burrows like larger soil animals (macrofauna) as earthworms.
Collembolans and earthworms also inhabit the litter layer at the soil surface.

And that brings us to the earthworms. The first ones were found on the island in 1993,
in soil samples taken in the gull colony. Two approximately 3 cm long juvenile individuals of
the species Lumbricus castaneus. No earthworms were found in July 1995, in spite of a
thorough search and sampling fo the same area.

There is no single answer to how the earthworm dispersed to Surtsey. Most likely they were
dispersed by birds from the other islands or from the mainland of Iceland.

Back to the collembolans again: Five species of collembolans were found in the plots on
Surtsey in 1995, and one species in Racomitrium-moss in the crater Gamli Surtur (Old Surtur).
Four of these six species hav not been found previously on the island. The dominant species
in the plots outside the gull colony were Mesaphorura macrochaeta and
Hypogastrura purpurescens in the plots inside the colony. Four species were also found
in samples taken in 2000, and two additional species were then also found in the plots.

In the gull-colony the density was as high as 74.724 collembolans in one square-meter,
but much lesser in some other plots (10.000 - 20.000 per m²). In 1995, 7 sepcies were
found in the soil samples investigated and 1 species on drifting wood on the northern sea
shore. The occurance of collembolans per m² in the different areas in 1995 are shown here:

Area	number per m²	number of species
J1	10.033	4
J5	72.956	6
J6	67.797	4
J6 E	97.369	4

78 individuals of OXnychiurus duplopunctatus were found under driftwood, not in any
of the areas. The two extra species found in J5 were 81 Iisotomiella minor and
41 Pseudisotoma sensibilis.
Ceratophysella succinea was only found in J1 (2.397 individuals).
The one species dominating all over, was the Hypogastrura purporescens, which however
was absent in J1, which is the pioneer plant community with Honkenya peploides and
Leymus arenarius.

You might be interested knowing that the total number of both collembolans and mites per
square-meter has been counted up to 340.000 individuals in the J6 E area.
All together in J1, J5, J5F, J6 and J6E, that equals 5 square meters, there was counted
a total of 1.024.064 induviduals.

So far we have had certain difficulties obtaining pictures/photos of those tiny
creatures, but we are working on the problem.
Any assistance will be highly appreciated!

Slugs were found for the first time on Surtsey in 1998, and they were also present one
year later. The slugs were found in ta dense grass sward in the gull colony. Identification to
species has not been carried out, but the specimens found on Surtsey are similar to slugs commonly found in moist grassland and gardens in southern Iceland.

Sampling of insects etc by an entomolog on Surtsey.
© c/o www.vulkaner.no

Since the volcanic island Surtsey emerged from the sea the dispersal of organisms to the
island and the development of biotic communities there have been studied by a number of biologists .The following is a report on the status of the land-arthropod fauna on
the island observed during a visit in July 1981.

Theweather was generally unsettled. Only on the first day of the research (July 10-16) the
weather was favourable for collecting flying insects, warm south-easterly gentle breeze and sunshine. The remaining days the wind was sometimes too strong for field-work, mostly rainy
but sandstorms when dry.

1.244 specimens of land-arthropods and 2 oligochaetes. (What's that?). Collembola
dominated with 723 specimens (see above on this page). The most dominating species
collected were Acyrthosiphon auctus of the Hemiptera-group, 81 Heleomyza borealis,
52 Meoneura lamellata, both belonging to Diptera, then 43 Erigone arctica (Araneae)
and finally 71 Neomolgus sp. and 131 Indet.spp (Acari). The largest group of species
belonged to the Diptera.

So far, so good. But to me this means just that a lot of different insects were collected.
So as usual the net has to be searched to see what to find out about those latin names.

From the excellent page of Arthropod.net (not valid as per Sept. 2010) the following were found regarding the Diptera:

'Although many winged insects are commonly called "flies," the name is strictly applicable
only to members of the Diptera. It is one of the largest insect orders and contains over
85,000 species; all are relatively small and have soft bodies. Mouth parts are of the sucking type,
but there is great variation. Some, like the blood-suckers, are serious pests. Flies are
beneficial as scavengers and predators or other insect pests.

Diptera are divided into three large groups: Nematocera (crane flies, midges, gnats,
and mosquitoes); the Brachycera (horse flies, robber flies and bee flies); and Cyclorrhapha
(flies that breed in vegetable or animal material, both living and dead.)'

It is obvious that some of the species observed on Surtsey have found a suitable habitat and
have settled permanently on the island. The island may sometimes be rather inhospitable
to some of the smaller organisms. Nonetheless some other species obviously settled on the
island for good such as some species of Diptera, some spiders and perhaps also one or
two staphylinid beetles.

The first opportunities insects were offered to survive and multiply on the island were
probably connected with carcasses drifted ashore and birds dying on the island. A certain
amount of competition for carcasses is likely to occur between gulls and the saprophagous
insects. In 1981 a number of carcasses were found that had been covered by tephraq,
thus inaccessible to gulls. These were inhabited by Heleomyza borealis larvae, a species
that proved to be very common on the island in 1981.

Many questions concerning development and succession of the soil formation and soil fauna
on Surtsey and its possible interaction with the vegetation and gull colony development still
remains a challenging subjects for future research.

Text mainly extracted from reports made by
Peter Gjelstrup, The Natural History Museum, Aarhus, Denmark,
and Hólmfriður Sigurdardóttir, Iceland (frida@skipulag.is).
Surtsey Research Report No. XI