Tiny individuals attached to a new Silurian arthropod suggest a unique mode of brood care

Abstract

The ∼430-My-old Herefordshire, United Kingdom, Lagerstätte has yielded a diversity of remarkably preserved invertebrates, many of which provide fundamental insights into the evolutionary history and ecology of particular taxa. Here we report a new arthropod with 10 tiny arthropods tethered to its tergites by long individual threads. The head of the host, which is covered by a shield that projects anteriorly, bears a long stout uniramous antenna and a chelate limb followed by two biramous appendages. The trunk comprises 11 segments, all bearing limbs and covered by tergites with long slender lateral spines. A short telson bears long parallel cerci. Our phylogenetic analysis resolves the new arthropod as a stem-group mandibulate. The evidence suggests that the tethered individuals are juveniles and the association represents a complex brooding behavior. Alternative possibilities-that the tethered individuals represent a different epizoic or parasitic arthropod-appear less likely.arthropod | Silurian | brood care | juvenile | Herefordshire Lagerstätte

Structural specialties, curiosities, and record‐breaking features of crustacean reproduction

“…The long history and persistence of giant sperm in ostracods since the Cretaceous makes them a unique model to study the evolutionary significance and function of this unusual sperm type in animals (Matzke‐Karasz et al, ; Smith et al, ). The embryo fossils demonstrate that brooding of the offspring in specialized body compartments has repeatedly evolved in the early history of crustaceans and related arthropods (Briggs et al, ). However, brood care has not replaced broadcast spawning completely, despite its apparent advantages.…”

Anamorphic development and extended parental care in a 520 million-year-old stem-group euarthropod from China

“…s6e, f], not dissimilar from that observed in some extant marine crustaceans [38][39][40]43]. Thus, F. protensa provides the phylogenetically and stratigraphically earliest evidence of XPC in the euarthropod fossil record [13-16, 41, 44], and reveals a greater diversity and complexity of reproductive strategies during the early Cambrian well beyond that of egg brood-care within a bivalved carapace [13][14][15][16].…”

“…Some studies have produced remarkable insights on the postembryonic development in other Lower Palaeozoic stem-group euarthropods, such as the recognition of limb rudiments in a juvenile of the megacheiran Leanchoilia illecebrosa [11], and the changes in bivalved carapace morphology and body segment count during growth in Isoxys auritus [12]. However, detailed information on the ontogeny and reproduction of Lower Palaeozoic euarthropods is for the most part only available from crown-group members [13][14][15][16][17][18][19][20][21][22], precluding the ancestral reconstruction of these traits during the early evolution of the phylum. Here we describe the post-embryonic development of Fuxianhuia protensa from the Cambrian (Stage 3) Chengjiang biota in South China [1,5].…”

Caught in the act of hatching – a group of heteropteran nymphs escaping from their eggs preserved in Dominican amber

“…Comparable to the Orsten-type fossils in their threedimensionality are fossils from the Herefordshire Lagerstätte. Some of these fossils have been reported to co-occur with their offspring (siVeter et al 2007;BriGGs et al 2016a). Yet, here the smaller individuals are so small that resolution prohibits the access of details.…”