Innate immunity in arthropods is achieved largely through melanization which is in turn the result of the prophenoloxidase (ProPO) activation cascade; a series of biochemical reactions triggered by the immune identification of pathogen-recognition proteins (PRPs). Within this activation cascade, inactive proPO is cleaved to form the reactive enzyme phenoloxidase (PO). Methods of detecting PO are used to assess an arthropod's ability to respond to immune challenges. These detection assays have been described for some arthropods, especially those of commercial value, but none are available for Euastacus, a genus within the superfamily Parastacoidea. This study is the first step in developing a standardized protocol for the detection and quantification of PO activity in wild or captive Murray crayfish Euastacus armatus. Hemolymph extracts from 49 crayfish were assessed for PO activity using an assay measuring the conversion of l-dopa (3,4-dihydroxy-l-phenylalanine) into dopachrome. Short periods (up to 15 min) out of water did not cause any measurable change in PO activity. Phenoloxidase activity was detected in captive (n = 24, stressed) and wild (n = 25, healthy) crayfish with captive crayfish showing lower levels of PO possibly indicating immunosuppression. The proven protocol is the first of its kind to propose a standardized methodology for the detection and quantification of PO activity in Murray crayfish hemolymph as a means of determining stress.

节肢动物的先天免疫主要通过黑化来实现，而黑化又是酚氧化酶原（ProPO）激活级联的结果。免疫识别病原体识别蛋白（PRP）引发的一系列生化反应。在该活化级联内，非活性的proPO被裂解以形成反应性酶酚氧化酶（PO）。检测PO的方法用于评估节肢动物对免疫挑战的反应能力。这些检测方法已针对某些节肢动物进行了描述，尤其是那些具有商业价值的节肢动物，但没有针对Euastacus（超家族Parastacoidea属）的一个种类进行检测。这项研究是开发用于检测和定量野生或圈养Murray小龙虾PO活性的标准化方案的第一步Euarmascus armatus。使用测定1-多巴（3,4-二羟基-1-苯丙氨酸）向多巴色素的转化的测定法评估了49只小龙虾的血淋巴提取物的PO活性。短时间内（最多15分钟）出水不会导致PO活性发生任何可测量的变化。在圈养小龙虾（n = 24，应激）和野生小龙虾（n = 25，健康）中检测到酚氧化酶活性，而圈养小龙虾的PO含量较低，可能表明存在免疫抑制作用。经过验证的协议是第一个提出用于检测和定量Murray小龙虾血淋巴中PO活性的标准化方法的方法，以此来确定压力。