One new species and records of Ichthydium Ehrenberg, 1830 (Gastrotricha: Chaetonotida) from Sweden with a key to the genus
Author
Kånneby, Tobias
Author
Todaro, Antonio
Author
Jondelius, Ulf
text
Zootaxa
2009
2278
26
46
journal article
10.5281/zenodo.191157
3709de53-c30a-4ec4-9676-30edc0511523
1175-5326
191157
Ichthydium squamigerum
Balsamo & Fregni, 1995
(
Figures 8E–G
;
Table 3
)
Localities:
Trösvattnet, Västmanland,
Sweden
(
59º33.211’N
;
14º29.232’E
); Lake Siljan, Dalarna,
Sweden
(
60º53.039’N
;
15º06.467’E
); Stora Skuggan,
Norra
Djurgården, Stockholm,
Sweden
(
59º22.068’N
;
18º04.152’E
).
Material:
7 specimens
, 3 measured.
TABLE 2.
Morphometric data (µm) for
Ichthydium diacanthum
(n=1). For comparison morphometrics from Balsamo & Todaro (1995) are included. L=Length, W=Width; Na, Not available.
Character Specimen
1
Balsamo & Todaro (1995)
Total body L 125 111–143 Head W 30 33–34 Neck W 25 Na
Body W 35 Na
Furca base W ~15 Na
Furca L 18–19 15–22 Adhesive tube L 10 Na
Pharynx L 32 17–33 Mouth ø Na Na
Furca spine L ~10 8.9–13.5 Anterior sensory bristle L ~20 Na
Posterior sensory bristle L ~22 Na
Remarks:
The specimens of
I. squamigerum
agree well with the morphometric data provided by
Balsamo & Fregni (1995)
. The distribution and shape of the rounded keeled scales at the base of the furca as well as the subrectangular ventral terminal scales also agree with the original description. A peculiar difference between the Swedish and the Italian specimens is that the former lack the bi-keeled scales anchoring the posterior sensory bristles. The bristles originate from papillae instead of scales.
Fregni
et al
. (1998)
found
I. squamigerum
exclusively in freshwater sand. Six of the Swedish specimens were found at a sandy beach at lake Siljan and one specimen in a very small sandy patch at lake Trösvattnet. The findings of
I. squamigerum
in
Sweden
are the first records outside
Italy
where the species was described. PhIJ at U28; ASB at U23; PSB at U78.
Associated gastrotrich fauna:
Chaetonotus benacensis
Balsamo & Fregni, 1995
,
C. hystrix
Metschnikoff, 1865
,
C. mutinensis
Balsamo, 1978
,
Lepidodermella squamata
and
Polymerurus rhomboides
(
Stokes, 1887
)
.
TABLE 3.
Morphometric data (µm) for
Ichthydium squamigerum
(n=3). For comparison morphometrics from Balsamo & Fregni (1995) are included. L=Length, W=Width; Na, Not available.
Character Specimen