In:
Contributions to Entomology, Pensoft Publishers, Vol. 73, No. 2 ( 2023-09-29), p. 131-136
Kurzfassung:
Shrinking pupal cocoons of Rhyacophila lezeyi were often found during summer in Shibukuro Stream, a highly acidic mountain stream in northern Japan (pH = 2.82 on average). We performed both field surveys and laboratory rearing experiments to clarify the mechanisms of R. lezeyi cocoon shrinkage. The R. lezeyi cocoon shrinkage proportion increased in years with high stream water temperatures and was related to water temperatures before and after pupation at the study site. Approximately 90% of the prepupae and pupae inside the shrinking cocoons died during the rearing experiment, implying that cocoon shrinkage caused by high water temperature strongly influenced R. lezeyi pupal survival. Laboratory experiments showed that R. lezeyi ’s pupal cocoon membranes were semi-permeable and that the cocoon fluids were always hyperosmotic, indicating that water molecules can continuously enter the cocoon fluids from the stream water until the turgor of the cocoon wall is reached. However, the shrinking cocoons showed lower fluid volume and higher osmolarity than the normal turgescent cocoons. The reduction of osmotic gradient across the membrane during decreased stream flow due to less precipitation and/or the damage to the cocoon membrane and pupal body from high and fluctuating water temperatures and low pH are possible mechanisms for R. lezeyi pupal cocoon shrinkage.
Materialart:
Online-Ressource
ISSN:
2511-6428
,
0005-805X
DOI:
10.3897/contrib.entomol.73.e107479
DOI:
10.3897/contrib.entomol.73.e107479.figure1
DOI:
10.3897/contrib.entomol.73.e107479.figure2
DOI:
10.3897/contrib.entomol.73.e107479.figure3
DOI:
10.3897/contrib.entomol.73.e107479.figure4
DOI:
10.3897/contrib.entomol.73.e107479.figure5
Sprache:
Unbekannt
Verlag:
Pensoft Publishers
Publikationsdatum:
2023
ZDB Id:
2882838-0
SSG:
12
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