Developmental dynamics is revealed in the early Cambrian arthropod Chuandianella ovata

Abstract

Summary Segmentation and tagmatization have contributed to the preeminent success of arthropods since their first appearance in the Cambrian. However, the exact mechanism of segmentogenesis is still insufficiently known in living and extinct groups. Here, we describe the postembryonic development of a Waptiid arthropod Chuandianella ovata from the early Cambrian Chengjiang biota, South China. The new data illuminate a complex dynamic pattern of anamorphosis and epimorphosis, and a three-step process of segmentogenesis, i.e., the elongation of the terminal segment, delineation of an incipient segment, and full separation of a new segment. Compensatory growth is accomplished by rapid growth of new segments and/or generation of additional segments, which results in the trimorphism of the posterior tagma. Such complex developmental dynamics has rarely been known in the arthropod fossil record and its presence in early history helps to understand the rapid diversification of arthropods in the early Cambrian.

A quantitative assessment of ontogeny and molting in a Cambrian radiodont and the evolution of arthropod development

“…Hemianamorphic development, with new segments generated from a posterior segment addition zone, is widespread in euarthropods and has been generally held to be ancestral for the phylum (Waloszek and Maas 2005; Fusco and Minelli 2021). Hemianamorphosis is found in virtually every major group of Cambrian euarthropods, including trilobites (Hughes et al 2021), marrellomorphs (García-Bellido and Collins 2006), megacheirans (Liu et al 2014), isoxyids (Fu et al 2014), fuxianhuiids (Fu et al 2018), pancrustaceans (Waloszek and Maas 2005; Haug et al 2014), and probably hymenocarines (Izquierdo-López and Caron 2021; Liu et al 2022). By contrast with euarthropods, tardigrade development is epimorphic, with all segments arising roughly simultaneously during embryogenesis (Smith and Goldstein 2017; but see Maas and Waloszek [2001] for a possible Cambrian exception).…”

“…The adult representatives of these taxa often remain obscure, although a few connections with Burgess Shale–type macrofossils have been proposed (Aria et al 2015; Aria and Caron 2017; Moysiuk and Caron 2019a). In addition, Burgess Shale–type deposits have yielded rare examples of juvenile arthropods alongside adults of the same species, enabling conclusions about segment addition and allometry (García-Bellido and Collins 2006; Zhang et al 2007; Haug et al 2011; Fu et al 2014, 2018; Aria et al 2015; Liu et al 2016; Mayers et al 2018; Izquierdo-López and Caron 2021; Yang et al 2021; Liu et al 2022). Finally, related evidence for how fossil arthropods underwent growth comes from the preserved record of ecdysis (Daley and Drage 2016).…”

Ontogeny and brooding strategy of the early Cambrian arthropod Isoxys minor from the Qingjiang biota

“…Among Cambrian bivalved arthropods, allometric growth is relatively common, for instance the carapace development of †Isoxys communis (García-Bellido et al, 2009a) and Tuzoia bispinosa (Wen et al, 2015), the ontogeny and trunk segmentation of †Isoxys auritus (Fu et al, 2014), and the development of the posterior tagma of †Chuandianella ovata (Liu et al, 2022). By contrast, isometric growth is rare in Cambrian bivalved arthropod postembryonic development, having been only reported in the carapace of †Branchiocaris?…”

“…minor are attached between the inner surface of the carapace and the body, like †Waptia fieldensis and †C. ovata (Caron and Vannier, 2016;Ou et al, 2020;Liu, 2022). By contrast, the eggs of †K.…”

Rapid growth in a large Cambrian apex predator

“…Insights into the development of early euarthropods are also important for furthering our understanding of the ecology of Cambrian ecosystems, as juvenile euarthropods can occupy different niches to adults of the same species [ 5 , 6 ]. Such studies have been conducted on a range of upper stem-group and crown-group euarthropods, including fuxianhuiids [ 7 ], hymenocarines [ 8 ], isoxyids [ 9 , 10 ], megacheirans [ 5 , 11 ] and trilobites [ 12–14 ]. Our knowledge of ontogeny within the lower stem-group of Euarthropoda ( sensu [ 15 ]), which charts the evolution from a lobopodian-like ancestor to the earliest diverging euarthropod group with arthropodized appendages, Radiodonta ( Amplectobelua, Anomalocaris, Hurdia and relatives) [ 2 , 15 , 16 ], is more limited.…”