Population Ecology Group, Department of Biology, University of New Brunswick, Fredericton, New Brunswick, E3B 6C2 Canada.
J Insect Physiol. 2010 Jun;56(6):610-5. doi: 10.1016/j.jinsphys.2009.12.009. Epub 2009 Dec 29.
Aphids are phloem feeders that occasionally ingest xylem sap. The duration of xylem consumption by Macrosiphum euphorbiae (Hemiptera: Aphididae) was positively correlated with the level of dehydration of alate aphids of different ages after a period of starvation, supporting the hypothesis that aphids ingest xylem sap to replenish their water balance. However, the duration of xylem sap ingestion but not phloem sap consumption varied in unstarved alate adults of different ages. Furthermore, both alate and apterous aphids ingested xylem sap at the end of their life, when aphids were not dehydrated but when fecundity started to decrease. Fecundity was negatively correlated with the proportion of time spent ingesting xylem sap, and that over the entire reproductive life of alate and apterous aphids. The lower proportion of xylem ingested by apterous than by alate aphids during the first few days of adult life may be related to a higher symbiont density in apterous morphs. As previous studies have demonstrated a relationship between sucrose assimilation, which is directly influenced by fecundity and symbiont density, and osmoregulation, we suggest that xylem consumption may play a role in the osmoregulation of haemolymph of aphids.
蚜虫是韧皮部取食者，偶尔也会摄入木质部汁液。在一段时间的饥饿后，不同龄期的有翅蚜脱水程度越高，其取食木质部的时间就越长，这支持了蚜虫摄入木质部汁液以补充水分平衡的假说。然而，在未饥饿的不同龄期有翅成蚜中，取食木质部汁液的时间（而非取食韧皮部汁液的时间）会发生变化。此外，有翅蚜和无翅蚜在生命末期，即当蚜虫没有脱水但生殖力开始下降时，也会摄入木质部汁液。生殖力与取食木质部汁液的时间比例呈负相关，与有翅蚜和无翅蚜整个生殖期的时间比例也呈负相关。无翅蚜在成虫期最初几天摄入的木质部比例比有翅蚜低，这可能与无翅型中共生体密度较高有关。由于之前的研究表明，蔗糖的同化与生殖力和共生体密度直接相关，而蔗糖的同化又与渗透调节有关，因此我们推测，蚜虫可能会通过摄入木质部汁液来调节血淋巴的渗透压。
