Alonella excisa
Alonella excisa is a littoral species which is characterized as moderate acid sensitive. The structure of the shell consists of polygons with small longitudinal lines inside.
Key characteristics
Alonella excisa (female)
Alonella excisa (male)
Alonella excisa has an oval look. The structure of the shell is characteristic and consists of polygons with small longitudinal lines inside. This criterion distinguishes this species from its close relative A. exigua. Furthermore the postabdomen of A. excisa is longer and more slender compared with A. exigua. The rostrum is relatively short and the ventral posterior corner has 2–4 small teeth. The colour is greyish-brown.
Female: Length 0.3–0.5 mm
Male: Length 0.2–0.3 mm
Ecology and distribution
A. excisa is a littoral species which occurs in more than one third (37 %) of the localities, and is distributed all over the country. It is found from sea level and up to 1387 m a.s.l. with its highest frequency between 500 and 700 m a.s.l. It is common in water bodies of all sizes, and is associated with different sorts of substrates and vegetation. The species have a wide tolerance towards pH (3.7–8.1) but occurs with its highest frequency at pH<5.0. A.excisa has been found under slight brackish conditions (154 mS/m), as well as in dilute mountain lakes (0.4 mS/m).
| Vitenskapelig navn | < 4,5 | 4,5 - 4,9 | 5,0 - 5,4 | 5,5 - 5,9 | 6,0 - 6,4 | 6,5 - 7,0 | 7,0 - 7,4 | > 7,5 |
|---|---|---|---|---|---|---|---|---|
| 73 | 69 | 35,3 | 37,5 | 34,9 | 30,5 | 33,2 | 16,7 |
| Vitenskapelig navn | < 1,0 | 1,0 - 1,4 | 1,5 - 1,9 | 2,0 - 2,9 | 3,0 - 3,9 | 4,0 - 4,9 | 5,0 - 6,9 | 7,0 - 9,9 | > 10,0 |
|---|---|---|---|---|---|---|---|---|---|
| 26,9 | 37,6 | 47,2 | 46,8 | 45,7 | 40,7 | 40,6 | 28,7 | 23,8 |
| Vitenskapelig navn | < 0,01 | 0,01 - 0,09 | 0,1 - 0,9 | 1,0 - 9,9 | 10,0 - 99 | 100 - 999 | > 1000 |
|---|---|---|---|---|---|---|---|
| 44,1 | 34,3 | 36 | 34,3 | 36,8 | 38,1 | 43,5 |
| Vitenskapelig navn | < 100 | 100-299 | 300-499 | 500-699 | 700-999 | >1000 |
|---|---|---|---|---|---|---|
| 30,4 | 39 | 40,1 | 54,1 | 39 | 16,5 |
Look-alikes
Alonella exigua
