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[Annelida] Swarming 'worm'

dfiege via annelida%40net.bio.net (by Dieter.Fiege from senckenberg.de)
Wed Dec 3 06:53:13 EST 2008


Hi all,

just to round this off here is a short account of what the German part 
of Spengel's 1909 paper says (rather freely translated and summarized by 
me). The info in the second paragraph below supports the identification 
of the specimens reported by Geoff as G. malayanus.

Cheers, Dieter

---------------------

Spengel comments [in German] that he described two species in his 
Siboga-Report: Glandiceps coromandelicus and G. eximius with the latter 
probably being the species observed by Ikeda and reported by him as G. 
hacksii.

Spengel reports a similar observation for G. malayanus , another species 
described by him in his Siboga-Report. G. malayanus had been observed 
swarming in enormous masses in spring 1899 near Surabaja. Unfortunately, 
only 6 specimens were preserved.

These observations on two species of the genus Glandiceps make it seem 
probable to Spengel that species of this genus – at least the smaller 
ones - are able to leave the bottom and swim at the surface for a while, 
where they gather in enormous masses.

Further Spengel discusses a flattening of the body posterior to the 
collar which Ikeda considers as acting as fins in swimming. Spengel does 
not follow Ikeda in this assumption since muscles are missing.

Spengel quotes Ikeda, who reported a different intensity in color for 
dorsal and ventral side, the former being darker than the latter – not 
observed for G. malayana. Ikeda considered his Glandiceps to be a 
swimmer and not a burrower but somehow contradicts himself in reporting 
burrowing movements for stranded individuals. Ikeda speculates about the 
diet of the species judging from the stomach content but Spengel holds 
against that they might well have emptied their stomach to increase 
buoyancy and that diatoms and dinoflagellates in the intestine – as 
found by Ikeda and himself - had been taken up during swimming which 
lasted at least a few days acc. to Ikeda.

Acc. to Spengel swarming appears not be correlated with reproduction 
since Ikeda reports individuals as not sexually mature. Spengel's own 
observations are not contradicting. But the swarming for feeding on a 
plancton bloom appears improbable to Spengel. Thus the reason for the 
swarming behaviour remains unknown and any analogy to epitoky in 
polychaetes speculation. The mass occurrence of the individuals and the 
stimulus for swarming remain without explanation.
-----------------




Geoff Read schrieb:

>Thanks Dieter, thanks Nicholas,
>
>I doubt there's much more in the lit than what you've come up with. Unfortunately I can't tell you any more about the event because I'm not in contact with the person who observed it. I speculate that it may be a curious fisherman or yacht person, and that no specimens exist. No film either.
>
>The Spengel is: Spengel, J.W. (1909). Pelagisches Vorkommen von Enteropneusten. Zoologischer Anzeiger, Leipzig 34: 54-59. 
>
>I attach a copy. There's a long English quote from Ikeda included. Dieter will be able to read the rest. I've ocr'd it.
>I looked at the Dawydoff (1952) - it just has a brief comment that one of three Glandiceps malayanus specimens was collected at the surface.
>
>Geoff
>
>
>
>
>
>NIWA is the trading name of the National Institute of Water & Atmospheric Research Ltd.
>

-- 
Dr. Dieter Fiege
Curator for Marine Invertebrates (Polychaeta)
Senckenberg Research Institute and Natural History Museum
Senckenberganlage 25
D-60325 Frankfurt/Main
Germany
ph: +49-(0)69-7542 1265
Fax: +49-(0)69-746238
www.senckenberg.de




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