Bowman Clive E
Mathematical Institute, University of Oxford, Oxford, OX2 6GG, UK.
Exp Appl Acarol. 2017 May;72(1):35-59. doi: 10.1007/s10493-017-0137-7. Epub 2017 May 24.
The occurrence of refractive crystals (aka guanine) is characterised in the Malpighian tubules of the free-living predatory parasitiform soil mite Pergamasus longicornis (Berlese) from a temporal series of histological sections during and after feeding on larval dipteran prey. The tubular system behaves as a single uniform entity during digestion. Malpighian mechanisms are not the 'concentrative' mechanism sought for the early stasis in gut size during the second later phase of prey feeding. Nor are Malpighian changes associated with the time of 'anal dabbing' during feeding. Peak gut expansion precedes peak Malpighian tubule guanine crystal occurrence in a hysteretic manner. There is no evidence of Malpighian tubule expansion by fluid alone. Crystals are not found during the slow phase of liquidised prey digestion. Malpighian tubules do not appear to be osmoregulatory. Malpighian guanine is only observed 48 h to 10 days after the commencement of feeding. Post digestion guanine crystal levels in the expanded Malpighian tubules are high-peaking as a pulse 5 days after the start of feeding (i.e. after the gut is void of food at 52.5 h). The half-life of guanine elimination from the tubules is 53 h. Evidence for a physiological input cascade is found-the effective half-life of guanine appearance in the Malpighian tubules being 7.8-16.7 h. Crystals are found present at all times in the lumen of the rectal vesicle and not anywhere else lumenally in the gut at all. No guanine was observed inside gut cells. There is no evidence for the storage in the rectal vesicle of a 'pulse' of Malpighian excretory products from a discrete 'pulse' of prey ingestion. A latent egestive common catabolic phase in the gut is inferred commencing 12.5 h after the start of feeding which may cause the rectal vesicle to expand due to the catabolism of current or previous meals. Malpighian tubules swell as the gut contracts in size over time post-prandially. There is evidence that at a gross level the contents of the rectal vesicle are mechanically voided by the physical mechanism of overall gut expansion altering the effective idiosomal volume available during prey ingestion. A complete cycle of feeding, digestion, egestion and excretion is approximately 9 days. Hunger/starvation likely commences at 10 days after the start of feeding. Up to 15 days may be needed to completely clear the idiosoma of excretory material. Nomograms for predicting the likely feeding time of mites from observations of idiosomal guanine in field samples indicate that as few as 5-6 mites scoring positive for Malpighian tubule guanine out of 20 infers a high probability that the typical time from start of feeding in a population sample was about 6 days (range 3-8 days) ago.
在自由生活的捕食性寄生土壤螨长角巨螯螨（Pergamasus longicornis，Berlese）取食幼虫双翅目猎物期间及之后的一系列组织学切片中，对屈光晶体（即鸟嘌呤）的出现情况进行了表征。在消化过程中，管状系统表现为一个单一的统一实体。马尔皮基氏机制并非猎物取食第二后期肠道大小早期停滞所寻求的“浓缩”机制。马尔皮基氏变化也与取食期间的“肛门擦拭”时间无关。肠道扩张峰值以滞后的方式先于马尔皮基氏小管鸟嘌呤晶体出现峰值。没有证据表明马尔皮基氏小管仅通过液体就能扩张。在液化猎物消化的缓慢阶段未发现晶体。马尔皮基氏小管似乎不具有渗透调节功能。仅在取食开始后48小时至10天观察到马尔皮基氏鸟嘌呤。消化后，扩张的马尔皮基氏小管中的鸟嘌呤晶体水平在取食开始后5天（即肠道在52.5小时排空食物后）达到脉冲式高峰。鸟嘌呤从小管中消除的半衰期为53小时。发现了生理输入级联的证据——马尔皮基氏小管中鸟嘌呤出现的有效半衰期为7.8 - 16.7小时。在直肠泡的管腔中始终发现有晶体，而在肠道的其他任何管腔部位均未发现。在肠道细胞内未观察到鸟嘌呤。没有证据表明从离散的猎物摄入“脉冲”中产生的马尔皮基氏排泄产物“脉冲”储存在直肠泡中。推断在取食开始12.5小时后肠道进入潜在的排泄性共同分解代谢阶段，这可能由于当前或先前餐食的分解代谢导致直肠泡扩张。餐后随着时间推移肠道收缩，马尔皮基氏小管肿胀。有证据表明，总体而言，直肠泡的内容物通过肠道整体扩张的物理机制机械性排空，从而改变了猎物摄入期间可利用的有效体躯体积。完整的摄食、消化、排泄和排遗周期约为9天。饥饿/饥饿状态可能在取食开始后10天开始。可能需要长达15天才能完全清除体躯中的排泄物质。根据野外样本中体躯鸟嘌呤的观察结果预测螨类可能的取食时间的列线图表明，在20只螨中，马尔皮基氏小管鸟嘌呤呈阳性的螨类少至5 - 6只，这意味着群体样本中从取食开始的典型时间很可能是大约6天（范围为3 - 8天）前。
