Giant planktic larvae of anomalan crustaceans and their unusual compound eyes

Abstract

Crustacean larvae are usually recognised as small organisms, below one millimeter body size. However, in different crustacean groups such as Stomatopoda, Polychelida, or Achelata, also very large larvae occur with sizes of 20 mm and beyond. Also from few meiuran species ("short-tailed" crustaceans, including crabs, hermit crabs, or squat lobsters), rather large larvae are known, though still considerably smaller than 20 mm. We present here two specimens of anomalan meiuran larvae, each with a total length of 24 mm, which by far exceed the previously known/ reported maximum sizes of meiuran larvae. Yet, both specimens exhibit characters that indicate their identity as zoea larvae (first larval phase with several stages), most likely shortly before the metamorphosis to the megalopa (second larval phase with one stage). Due to this early developmental state, it is difficult to provide a narrower systematic identification of the larvae. In addition to the description of the developmental status of all appendages, we also investigated the gizzard and especially the compound eyes. The latter possess a mixture of hexagonal, intermediate, and square-shaped facets in an unusual arrangement. We documented the exact arrangement of the facets in both specimens and discuss the possible restructuring during metamorphosis. The arrangement of the different types of facets indicates that transformation to an adult eye structure takes place over several moults and that the facets are being rearranged in this process. The findings demonstrate that also meiuran larvae contribute to the fraction of the macro-plankton.

Developmental dynamics is revealed in the early Cambrian arthropod Chuandianella ovata

“…The consistent morphology of the four phenotypes indicates that these specimens acquired adult morphology during the postembryonic development. Therefore, it is less likely that the significantly increased five-segment specimens represented “giant larval” as seen in the extant and extinct crustacean larvae ( Gundi et al., 2020 ; Nagler et al., 2017 ). The size decrease during the postembryonic development is presently unknown among extant and extinct arthropods.…”

Methods to study organogenesis in decapod crustacean larvae II: analysing cells and tissues

“…c Maxilliped of late Zoea of a false sand crab (Hippidae; modified from [164]); note the well apparent muscles. d Compound eye of late Zoea of an anomalan crustacean (modified from [165]). e Zoea of an undetermined brachyuran crab, lateral view, confocal laser-scan microscopy (C. Haug, J. T. Haug, unpublished).…”

Methods to study organogenesis in decapod crustacean larvae. I. larval rearing, preparation, and fixation

“…Cancer anthonyi PH [116] Portunus trituberculatus PH [117] Carcinus maenas µCT, 3D [35] Maja brachydactyla µCT, 3D [92] Mouthparts and digestive tract Several Anomura EF, LiMi [112] Maja brachydactyla µCT, PH, SEM, TEM [118,119] Hyas araneus STH, TEM [84,120] Scylla olivacea PH [121] Scylla serrata PH [122][123][124] Ucides cordatus PH [125] Dyspanopeus sayi SEM, LiMi [126] Sesarma curacaoense PH [127] Several Brachyura SEM [128] Ranina ranina PH [129] Menippe mercenaria SEM [130] Paralithodes camtschaticus PH [131] Homarus americanus TEM, SEM, STH [97,130,132] Astacus astacus, Procambarus fallax f. virginalis SEM, TEM, PH [133,134] Jasus edwardsii SEM [135] Macrobrachium amazonicum SEM [136] Palaemon elegans SEM, TEM [34,136] Lysmata amboinensis PH, SEM [137] Porcellio scaber STH, SEM, TEM [138] Osmoregulatory epithelia…”

“…At the experimental level, we cover aspects of the execution (i.e. larval rearing); yet, many aspects of the experimental design depend on the question asked by the researcher and Hippolyte inermis clsm, SEM [108] Carcinus maenas µCT, 3D [35] Portunus acuminatus SEM [32] Xantho poressa, Xantho pilipes SEM [109] Gnathophyllum elegans SEM [110] Periclimenes amethysteus SEM [111] Several Anomura EF, LiMi [112] Several Stomatopoda EF [113] Several Polychelida EF [114] Hippidae EF [115] General anatomy…”