Videnskabelige meddelelser

Videnskabelige meddelelser


In deeper lakes it seems that its home is the middle layers

of water; by means of nets with wide meshes I have from 20 to

25 m in Furesø got a peculiar plancton consisting of Bythotrephes

longimanns, Leptodora hijalina, Atax crassipes and some larvæ

of Corethra pliimicornis. It is most common over the submerged

meadows of Characeæ, Elodea a. a. in the large bay Store Kalven

in Furesø.

Further investigations may show whether a periodicity can be

pointed out. It seems as if there are seasons when all the mites

caught are nymphs, but more thorough studies are desirable.

The metamorphosis of the mite is very remarkable. As stated

above Koenike (1890, p. 138) showed that the nymph which

Claparéde (1868, p. 471) supposed to be that of Atax crassipes

really belonged to a new species ^4. aciilealus Koen. Wolcott

(1899, p. 209) and Kelly (1899, p. 414) mention Atax crassipes

as parasite in mussels.

From Europe a long series of observations shows that A. cras-

sipes at all events can accomplish its metamorphosis in Spongilla

colonies. Twenty five years ago I found in Teglgaardsø, Hillerød,

some fine colonies of Spongilla, in which numerous black mites

were parasites. They were determined as Alax crassipes. They

were found in all stages as sixlegged larvæ, in the first pupa stage,

as newly hatched nymphs and in the second pupa stage. The co-

lonies were brought to the zoological museum at Copenhagen. In the

following years I have cut hundreds of Spongilla-colonies through,

but I never again saw a single colony with mites. Piersig (1900,

p. 56) indicates that Alax crassipes in all probability in the larva

stages is parasitic in Spongilla-colonies but is free swimming as

adult. So ar (1906, p. 365) reports that he in England (Sutton

Broad) found A. crassipes in great numbers in Spongilla and

„Die figures a piece with mites. In :

Koenike (1909, p. 96) mentions :

Suszwasserfauna Deutschlands"

„Imagines und Nymphe freilebend,

die Larve bei Spongilla schmarotzend". Micoletzky

(1912, p. 42!) reports that he found Atax crassipes in Spongilla

lacuslris in Niedertrummersee in Salzburg; they were present

partly in young stages, partly as imagines. Musselius (1914, p.

63) communicates that 16 VIII he found a Spongilla lacnstris with

numerous eggs from which the sixlegged larval stage of Alax cras-

sipes was hatched a few days later.

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