Unionoid淡水贻贝(Bivalvia:Unionidae)是自由生活的,强制寄生,感染鱼类宿主的幼虫阶段,妊娠雌性贻贝已经进化出一系列策略,用它们的幼虫感染鱼类宿主。在许多北美物种中,这涉及展示地幔诱饵:一种色素多肉的延伸,充当宿主鱼猎物的攻击性模仿,从而引发导致宿主感染的摄食反应。Lampsilisfasciola的地幔诱饵特别令人感兴趣,因为它显然是多态的,具有两种不同的主要诱饵表型。一,被描述为“像飞镖一样”,有“眼点”,斑驳的身体颜色,突出的边缘延伸,和一个独特的“尾巴”。另一个,描述为“类似蠕虫”,缺乏这些功能,并有橙色和黑色的颜色。我们用基因组学研究了这种现象,圈养,生物地理,和行为分析。对具有不同诱饵的个体的亲源内诱饵变异和种群内系统基因组(ddRAD-seq)分析证实,这种现象是真正的多态性。在生态时间段内,这两种形态的相对丰度似乎是稳定的:2017年葡萄干河(MI)种群中两种诱饵表型的比例与六十年前在同一地点收集的博物馆样本的比例一致。葡萄干河内,四个主要的“类似于飞镖的”诱饵图案在视觉上近似四个同时出现的飞镖物种(Etheostomablennioides,E.流亡,E.microperca,和斑点石),“蠕虫状”的诱饵类似于一种普遍的普通水蛭,MacrobdellaDecora.Darters和水蛭是Micropterusdolomieui(小嘴鲈鱼)的典型猎物,L.Fiscoola的主要鱼类宿主。在现场现场录制的“飞毛虫”和“水蛭”引诱显示行为,以及同时发生的同源体Cardium的引诱显示,被捕获。尽管在不同的门中有假定的模型,两种L.fisroola诱饵变体的展示行为与同伴L.cardium个体有很大差异。观察到两种L型之间的行为存在一些微小差异。但我们没有发现明确的证据表明多态性的行为成分。发现诱饵多态性的离散育龄遗传暗示了单个遗传位点的潜在控制,并将L.fasciola鉴定为一个有前途的研究系统,可以鉴定控制淡水贻贝关键适应性性状的调节基因。
Unionoid freshwater mussels (Bivalvia:
Unionidae) are free-living apart from a brief, obligately parasitic, larval stage that infects fish hosts, and gravid female mussels have evolved a spectrum of strategies to infect fish hosts with their larvae. In many North American species, this involves displaying a mantle lure: a pigmented fleshy extension that acts as an aggressive mimic of a host fish prey, thereby eliciting a feeding response that results in host infection. The mantle lure of Lampsilis fasciola is of particular interest because it is apparently polymorphic, with two distinct primary lure phenotypes. One, described as \"darter-like\", has \"eyespots\", a mottled body coloration, prominent marginal extensions, and a distinct \"tail\". The other, described as \"worm-like\", lacks those features and has an orange and black coloration. We investigated this phenomenon using genomics, captive rearing, biogeographic, and behavioral analyses. Within-brood lure variation and within-population phylogenomic (ddRAD-seq) analyses of individuals bearing different lures confirmed that this phenomenon is a true polymorphism. The relative abundance of the two morphs appears stable over ecological timeframes: the ratio of the two lure phenotypes in a River Raisin (MI) population in 2017 was consistent with that of museum samples collected at the same site six decades earlier. Within the River Raisin, four main \"darter-like\" lure motifs visually approximated four co-occurring darter species (Etheostoma blennioides, E. exile, E. microperca, and Percina maculata), and the \"worm-like\" lure resembled a widespread common leech, Macrobdella decora. Darters and leeches are typical prey of Micropterus dolomieui (smallmouth bass), the primary fish host of L. fasciola. In situ field recordings of the L. fasciola \"darter\" and \"leech\" lure display behaviors, and the lure display of co-occurring congener L. cardium, were captured. Despite having putative models in distinct phyla, both L. fasciola lure morphs have largely similar display behaviors that differ significantly from that of sympatric L. cardium individuals. Some minor differences in the behavior between the two L. fasciola morphs were observed, but we found no clear evidence for a behavioral component of the polymorphism given the criteria measured. Discovery of discrete within-brood inheritance of the lure polymorphism implies potential control by a single genetic locus and identifies L. fasciola as a promising study system to identify regulatory genes controlling a key adaptive trait of freshwater mussels.