具有寄生生活方式的生物在水生和陆地环境中占生物多样性的比例很高。然而,它们获取营养的方式有相当大的差异。嗜血是一些陆地人使用的一种常见的消费策略,水生,和海洋生物,寄生虫从宿主中去除和消化血液。类等足动物是海洋吸血寄生虫,从潮间带到深渊生活在底栖底物中。虽然在生态上类似于蜱和蚊子,他们只在3个青少年阶段中的每一个阶段进食,成年人不进食。它们长期以来被认为是通才的鱼类寄生虫,迄今为止,目前还没有关于它们成功以无脊椎动物为食的报道。根据从光陷阱收集的软体无脊椎动物附着的gnathiids的观察,我们进行了一项实验室实验,在该实验中,我们收集并单独饲养了各种常见的加勒比无脊椎动物,并将它们放在装有gnathiids的容器中,以查看gnathiids是否会以它们为食。随后将所有饲喂的gnathiids从容器中取出,并有机会变质到下一个发育阶段。总的来说,到第二天早上,在4种潜在无脊椎动物寄主中的1种出现的260种gnathiids中,有10种已经进食。具体来说,以生菜海su(Elysiacrispata)为食的可能的120种gnathiids中的9种,和可能的20种以胡须火虫(Hermodicecarunculata)为食的1种。这10个喂食的gnathiids中的8个变质到下一阶段(5个成年雄性,2至成年女性,和1到第三阶段少年)。尽管无脊椎动物的摄食率大大低于实验室对鱼类的研究,这项研究提供了第一个记录在案的gnathiids\'以无脊椎动物膳食为食和变质的案例。这些发现表明,当鱼类宿主不容易获得时,gnathiids可以转换为软体无脊椎动物。他们进一步提供了对该家族成员中从活宿主取食液体的演变的见解。
Organisms with a parasitic lifestyle comprise a high proportion of biodiversity in aquatic and terrestrial environments. However, there is considerable variation in the ways in which they acquire nutrients. Hematophagy is a common consumption strategy utilized by some terrestrial, aquatic, and marine organisms whereby the parasite removes and digests blood from a host. Gnathiid isopods are marine hematophagous parasites that live in benthic substrates from the intertidal to the abyss. Although ecologically similar to ticks and mosquitoes, they feed only during each of 3 juvenile stages and adults do not feed. They have long been considered as generalist fish parasites and to date, there have been no reports of their successfully feeding on invertebrates. Based on observations of gnathiids attached to soft-bodied invertebrates collected from light traps, we conducted a laboratory experiment in which we collected and individually housed various common Caribbean invertebrates and placed them in containers with gnathiids to see if the gnathiids would feed on them. All fed gnathiids were subsequently removed from containers and given the opportunity to metamorphose to the next developmental stage. In total, 10 out of the 260 gnathiids that were presented with 1 of 4 species of potential invertebrate hosts had fed by the next morning. Specifically, 9 of a possible 120 gnathiids fed on lettuce sea slugs (Elysia crispata), and 1 of a possible 20 fed on a bearded fireworm (Hermodice carunculata). Eight of these 10 fed gnathiids metamorphosed to the next stage (5 to adult male, 2 to adult female, and 1 to third-stage juvenile). Even though feeding rates on invertebrates were considerably lower than observed for laboratory studies on fishes, this study provides the first documented case of gnathiids\' feeding on and metamorphosing from invertebrate meals. These findings suggest that when fish hosts are not readily available, gnathiids could switch to soft-bodied invertebrates. They further provide insights into the evolution of feeding on fluids from live hosts in members of this family.