Notes on Gammarus pulex in the English Lake District

✍ Scribed by T. T. Macan; Jean C. Mackereth

• Book ID: 104643225
• Publisher: Springer
• Year: 1957
• Tongue: English
• Weight: 559 KB
• Volume: 9
• Category: Article
• ISSN: 1573-5141
• DOI: 10.1007/bf00150055

✦ Synopsis

down from the plateau about 1 in 12 .5 . In three summers, the highest temperature recorded on a thermograph in a tributary at a point not far below the moss was 19°C and generally in fine weather the maximum did not go much above 16°C . Lower down, the main stream was a degree or two warmer .

Smooth Beck differed in three features : 1 . It flowed down a steep hill for most of its length and the fall was 1 in 11 .5, that is a little steeper than the steepest part of Ford Wood Beck . 2 . It originated in a series of tarns . 3 . For most of its length it flowed in a wooded gorge .

BREEDING SEASON

Most of the information is derived from collections made approximately once a week in Smooth Beck from April 1949 to March 1952 .

Collecting was on a time basis and for the first seven months was by means of a pipette, subsequently by means of a hand net . All the collections in Ford Wood Beck were made with a hand net .

No measurements were made but all specimens which, according to our experience, were large enough to be sexually mature were picked out for examination . Throughout the springs and summers of the two years, 50-100 % of females bore eggs, except in the whole of July 1949 and on March 23 1950 when the percentage was lower . Breeding began to come to an end in October and the resting period lasted till the end of the year (table 1) . The others who have observed Gammarus record a similar cycle, though BERG (1948) found a lower percentage of egg-bearing females particularly in summer and autumn . TABLE I The breeding season of Gammarus pulex no pairs found Oct. 6 -Dec. 15 Oct . 12 -Jan . 18 1) no egg-bearing females found Nov . 3 -Jan . 12) 2) Nov. 16 -Jan. 4 1) one on Dec. 28th. 2) one on Nov. 24th.