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Raninoidea. A-F, Lyreididae; A-C, Lysirude nitidus (=Lyreidus bairdii), USNM 66638; A, dorsal view of female; B, SEM image of small right eye in a stout podophthalmite; C, details of the cornea bearing hexagonal facets in hexagonal packing. D-F, Lysirude griffini, USNM 216726; D, dorsal view of male; E, SEM image of small right eye; C, details of the cornea bearing hexagonal facets in hexagonal packing. G-I, Raninidae: Cyrtorhininae: Cyrtorhina granulosa, MNHN-IU-2016-2020 (= MNHN-B16181); G, dorsal view of female; H, SEM image of small right eye; I, details of the cornea bearing hexagonal facets in hexagonal packing. J-L, Raninidae: Symethinae: Symethis sp., uncatalogued specimen; J, dorsal view of male; K, Confocal microscope image of small right eye showing the different shapes and sizes of facets through the cornea; L, details of the cornea bearing hexagonal facets in hexagonal packing. Figure by J. Luque.
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Image-forming compound eyes are such a valuable adaptation that similar visual systems have evolved independently across crustaceans. But if different compound eye types have evolved independently multiple times, how useful are eye structures and ommatidia morphology for resolving phylogenetic relationships? Crabs are ideal study organisms to explo...
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... nitidus (A. Milne-Edwards, 1880) (=Lyreidus bairdii) ( Fig. 8A-C) and Lysirude griffini 200! Goeke, 1985 ( Fig. 8D-F 8G-I), Symethis sp. (Fig. J-L), Cosmonotus grayi White, 1848 ( Fig. 9A-C), Notopus dorsipes (Linnaeus, 1758) ( Fig. 9D-F), Ranilia muricata H Milne Edwards, 1837 ( Fig. 9G-I), Ranina . CC-BY-NC-ND 4.0 International license It is made available under a was not peer-reviewed) is the ...
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... nitidus (A. Milne-Edwards, 1880) (=Lyreidus bairdii) ( Fig. 8A-C) and Lysirude griffini 200! Goeke, 1985 ( Fig. 8D-F 8G-I), Symethis sp. (Fig. J-L), Cosmonotus grayi White, 1848 ( Fig. 9A-C), Notopus dorsipes (Linnaeus, 1758) ( Fig. 9D-F), Ranilia muricata H Milne Edwards, 1837 ( Fig. 9G-I), Ranina . CC-BY-NC-ND 4.0 International license It is made available under a was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to ...
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... nitidus (A. Milne-Edwards, 1880) (=Lyreidus bairdii) ( Fig. 8A-C) and Lysirude griffini 200! Goeke, 1985 ( Fig. 8D-F 8G-I), Symethis sp. (Fig. J-L), Cosmonotus grayi White, 1848 ( Fig. 9A-C), Notopus dorsipes (Linnaeus, 1758) ( Fig. 9D-F), Ranilia muricata H Milne Edwards, 1837 ( Fig. 9G-I), Ranina . CC-BY-NC-ND 4.0 International license It is made available under a was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. ...
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... lyreidid crab Lyreidus nitidus ( Fig. 8A) has small sub-conical eyes resting in stout and much longer podophthalmite, nearly 66% larger than the corneal eye, and covered in fibrous setae ( Table 1). The studied specimen of Lysirude griffini ( Fig. 8D) has even more reduced sub-conical eyes and a longer and broader podophthalmite than L. nitidus; the podophthalmite is nearly ...
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... lyreidid crab Lyreidus nitidus ( Fig. 8A) has small sub-conical eyes resting in stout and much longer podophthalmite, nearly 66% larger than the corneal eye, and covered in fibrous setae ( Table 1). The studied specimen of Lysirude griffini ( Fig. 8D) has even more reduced sub-conical eyes and a longer and broader podophthalmite than L. nitidus; the podophthalmite is nearly twice as long as the corneal eye, and it is partly covered in small setae (Fig. 8E). Both eye and eyestalk are barely protected by a narrow orbit with one supraorbital fissure, and a short, 370! blunt, triangular ...
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... podophthalmite, nearly 66% larger than the corneal eye, and covered in fibrous setae ( Table 1). The studied specimen of Lysirude griffini ( Fig. 8D) has even more reduced sub-conical eyes and a longer and broader podophthalmite than L. nitidus; the podophthalmite is nearly twice as long as the corneal eye, and it is partly covered in small setae (Fig. 8E). Both eye and eyestalk are barely protected by a narrow orbit with one supraorbital fissure, and a short, 370! blunt, triangular outer orbital spine directed anteriorly (Fig 8D). The cornea width is approximately 1.5% the length of the carapace, and it is constituted by a few hundred small hexagonal facets that are packed in hexagonal ...
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... studied specimen of Lysirude griffini ( Fig. 8D) has even more reduced sub-conical eyes and a longer and broader podophthalmite than L. nitidus; the podophthalmite is nearly twice as long as the corneal eye, and it is partly covered in small setae (Fig. 8E). Both eye and eyestalk are barely protected by a narrow orbit with one supraorbital fissure, and a short, 370! blunt, triangular outer orbital spine directed anteriorly (Fig 8D). The cornea width is approximately 1.5% the length of the carapace, and it is constituted by a few hundred small hexagonal facets that are packed in hexagonal array, with an average facet diameter of 23 µm . ...
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... copyright holder for this preprint (which . http://dx.doi.org/10.1101/786087 doi: bioRxiv preprint first posted online Oct. 7, 2019; ( Fig. 8C; Table 1). Hexagonal facets in hexagonal array have been reported for Lyreidus tridentatus (see Scholtz and McLay, 2009), suggesting a shared lack of 'mirror' eyes among 375! crabs of the family ...
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... all the podotreme crabs studied, those of the family Raninidae have the broadest range of eye shapes, sizes, and orbital constructions. In the subfamily Cyrtorhininae, Cyrtorhina granulosa ( Fig. 8G) shows a considerable reduction of the corneal region compared with the rest of the eyestalk. Its cornea is sub-conical and dorsally truncated by an extension of the cuticle of 380! the podophthalmite that extends towards the pole of the eye, further reducing the area occupied by the cornea (Fig. 8H). The cornea width is approximately ...
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... subfamily Cyrtorhininae, Cyrtorhina granulosa ( Fig. 8G) shows a considerable reduction of the corneal region compared with the rest of the eyestalk. Its cornea is sub-conical and dorsally truncated by an extension of the cuticle of 380! the podophthalmite that extends towards the pole of the eye, further reducing the area occupied by the cornea (Fig. 8H). The cornea width is approximately 1.8% the length of the carapace, and it is constituted by small hexagonal facets in hexagonal array, with an average facet diameter of 35 µm ( Fig. 8H, I; Table 1 Fig. 8K, L; Table ...
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... truncated by an extension of the cuticle of 380! the podophthalmite that extends towards the pole of the eye, further reducing the area occupied by the cornea (Fig. 8H). The cornea width is approximately 1.8% the length of the carapace, and it is constituted by small hexagonal facets in hexagonal array, with an average facet diameter of 35 µm ( Fig. 8H, I; Table 1 Fig. 8K, L; Table ...
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... of the cuticle of 380! the podophthalmite that extends towards the pole of the eye, further reducing the area occupied by the cornea (Fig. 8H). The cornea width is approximately 1.8% the length of the carapace, and it is constituted by small hexagonal facets in hexagonal array, with an average facet diameter of 35 µm ( Fig. 8H, I; Table 1 Fig. 8K, L; Table ...
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... the substratum during the day, emerging at night to search for food (Skinner and Hill, 1986). Some taxa like Ranilia, Ranina, and 605! particularly Cosmonotus, have relatively large eyes covered in small facets of nearly the same size throughout the cornea, and have long podophthalmite eyestalks that can be held outside the sediment when buried (Fig. 8). Conversely, raninid crabs like Symethis (Fig. 7J) show an . CC-BY-NC-ND 4.0 International license It is made available under a was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in ...
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... nitidus (A. Milne-Edwards, 1880) (=Lyreidus bairdii) ( Fig. 8A-C) and Lysirude griffini 200! Goeke, 1985 ( Fig. 8D-F 8G-I), Symethis sp. (Fig. J-L), Cosmonotus grayi White, 1848 ( Fig. 9A-C), Notopus dorsipes (Linnaeus, 1758) ( Fig. 9D-F), Ranilia muricata H Milne Edwards, 1837 ( Fig. 9G-I), Ranina . CC-BY-NC-ND 4.0 International license It is made available under a was not peer-reviewed) is the ...
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... nitidus (A. Milne-Edwards, 1880) (=Lyreidus bairdii) ( Fig. 8A-C) and Lysirude griffini 200! Goeke, 1985 ( Fig. 8D-F 8G-I), Symethis sp. (Fig. J-L), Cosmonotus grayi White, 1848 ( Fig. 9A-C), Notopus dorsipes (Linnaeus, 1758) ( Fig. 9D-F), Ranilia muricata H Milne Edwards, 1837 ( Fig. 9G-I), Ranina . CC-BY-NC-ND 4.0 International license It is made available under a was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to ...
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... nitidus (A. Milne-Edwards, 1880) (=Lyreidus bairdii) ( Fig. 8A-C) and Lysirude griffini 200! Goeke, 1985 ( Fig. 8D-F 8G-I), Symethis sp. (Fig. J-L), Cosmonotus grayi White, 1848 ( Fig. 9A-C), Notopus dorsipes (Linnaeus, 1758) ( Fig. 9D-F), Ranilia muricata H Milne Edwards, 1837 ( Fig. 9G-I), Ranina . CC-BY-NC-ND 4.0 International license It is made available under a was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. ...
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... lyreidid crab Lyreidus nitidus ( Fig. 8A) has small sub-conical eyes resting in stout and much longer podophthalmite, nearly 66% larger than the corneal eye, and covered in fibrous setae ( Table 1). The studied specimen of Lysirude griffini ( Fig. 8D) has even more reduced sub-conical eyes and a longer and broader podophthalmite than L. nitidus; the podophthalmite is nearly ...
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... lyreidid crab Lyreidus nitidus ( Fig. 8A) has small sub-conical eyes resting in stout and much longer podophthalmite, nearly 66% larger than the corneal eye, and covered in fibrous setae ( Table 1). The studied specimen of Lysirude griffini ( Fig. 8D) has even more reduced sub-conical eyes and a longer and broader podophthalmite than L. nitidus; the podophthalmite is nearly twice as long as the corneal eye, and it is partly covered in small setae (Fig. 8E). Both eye and eyestalk are barely protected by a narrow orbit with one supraorbital fissure, and a short, 370! blunt, triangular ...
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... podophthalmite, nearly 66% larger than the corneal eye, and covered in fibrous setae ( Table 1). The studied specimen of Lysirude griffini ( Fig. 8D) has even more reduced sub-conical eyes and a longer and broader podophthalmite than L. nitidus; the podophthalmite is nearly twice as long as the corneal eye, and it is partly covered in small setae (Fig. 8E). Both eye and eyestalk are barely protected by a narrow orbit with one supraorbital fissure, and a short, 370! blunt, triangular outer orbital spine directed anteriorly (Fig 8D). The cornea width is approximately 1.5% the length of the carapace, and it is constituted by a few hundred small hexagonal facets that are packed in hexagonal ...
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... studied specimen of Lysirude griffini ( Fig. 8D) has even more reduced sub-conical eyes and a longer and broader podophthalmite than L. nitidus; the podophthalmite is nearly twice as long as the corneal eye, and it is partly covered in small setae (Fig. 8E). Both eye and eyestalk are barely protected by a narrow orbit with one supraorbital fissure, and a short, 370! blunt, triangular outer orbital spine directed anteriorly (Fig 8D). The cornea width is approximately 1.5% the length of the carapace, and it is constituted by a few hundred small hexagonal facets that are packed in hexagonal array, with an average facet diameter of 23 µm . ...
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... copyright holder for this preprint (which . http://dx.doi.org/10.1101/786087 doi: bioRxiv preprint first posted online Oct. 7, 2019; ( Fig. 8C; Table 1). Hexagonal facets in hexagonal array have been reported for Lyreidus tridentatus (see Scholtz and McLay, 2009), suggesting a shared lack of 'mirror' eyes among 375! crabs of the family ...
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... all the podotreme crabs studied, those of the family Raninidae have the broadest range of eye shapes, sizes, and orbital constructions. In the subfamily Cyrtorhininae, Cyrtorhina granulosa ( Fig. 8G) shows a considerable reduction of the corneal region compared with the rest of the eyestalk. Its cornea is sub-conical and dorsally truncated by an extension of the cuticle of 380! the podophthalmite that extends towards the pole of the eye, further reducing the area occupied by the cornea (Fig. 8H). The cornea width is approximately ...
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... subfamily Cyrtorhininae, Cyrtorhina granulosa ( Fig. 8G) shows a considerable reduction of the corneal region compared with the rest of the eyestalk. Its cornea is sub-conical and dorsally truncated by an extension of the cuticle of 380! the podophthalmite that extends towards the pole of the eye, further reducing the area occupied by the cornea (Fig. 8H). The cornea width is approximately 1.8% the length of the carapace, and it is constituted by small hexagonal facets in hexagonal array, with an average facet diameter of 35 µm ( Fig. 8H, I; Table 1 Fig. 8K, L; Table ...
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... truncated by an extension of the cuticle of 380! the podophthalmite that extends towards the pole of the eye, further reducing the area occupied by the cornea (Fig. 8H). The cornea width is approximately 1.8% the length of the carapace, and it is constituted by small hexagonal facets in hexagonal array, with an average facet diameter of 35 µm ( Fig. 8H, I; Table 1 Fig. 8K, L; Table ...
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... of the cuticle of 380! the podophthalmite that extends towards the pole of the eye, further reducing the area occupied by the cornea (Fig. 8H). The cornea width is approximately 1.8% the length of the carapace, and it is constituted by small hexagonal facets in hexagonal array, with an average facet diameter of 35 µm ( Fig. 8H, I; Table 1 Fig. 8K, L; Table ...
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... the substratum during the day, emerging at night to search for food (Skinner and Hill, 1986). Some taxa like Ranilia, Ranina, and 605! particularly Cosmonotus, have relatively large eyes covered in small facets of nearly the same size throughout the cornea, and have long podophthalmite eyestalks that can be held outside the sediment when buried (Fig. 8). Conversely, raninid crabs like Symethis (Fig. 7J) show an . CC-BY-NC-ND 4.0 International license It is made available under a was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in ...
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Decapod crustaceans, such as alvinocaridid shrimps, bythograeid crabs and galatheid squat lobsters are important fauna in the hydrothermal vents and have well adapted to hydrothermal vent environments. In this study, eighteen mitochondrial genomes (mitogenomes) of hydrothermal vent decapods were used to explore the evolutionary history and their ad...
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... Although it is evident that the genes we and others have used are insufficient to resolve deep relationships even with current taxon sampling ( Supplementary Fig. S14), many regions of the tree are strongly supported. For example, the broadest strokes of our topological results (Fig. 2) contribute to the chorus of molecular and morphological analyses rejecting the monophyly of podotremes (e.g., Ahyong et al. 2007;Tsang et al. 2014Tsang et al. , 2022Luque et al. 2019aLuque et al. , 2019bTan et al. 2019) andheterotremes (e.g., von Sternberg andCumberlidge 2001;Tsang et al. 2014;Ma et al. 2019;Tan et al. 2019). Our divergence time estimates are older than most previous publications, except the deeper ages inferred by Wolfe et al. (2019) and the hypotheses of Guinot et al. (2019), but see below for evaluation. ...
For much of terrestrial biodiversity, the evolutionary pathways of adaptation from
marine ancestors are poorly understood, and have usually been viewed as a binary trait. True
crabs, the decapod crustacean infraorder Brachyura, comprise over 7,600 species representing a
striking diversity of morphology and ecology, including repeated adaptation to non-marine
habitats. Here, we reconstruct the evolutionary history of Brachyura using new and published
sequences of 10 genes for 344 tips spanning 88 of 109 brachyuran families. Using 36 newly
vetted fossil calibrations, we infer that brachyurans most likely diverged in the Triassic, with
family-level splits in the late Cretaceous and early Paleogene. By contrast, the root age is
underestimated with automated sampling of 328 fossil occurrences explicitly incorporated into
the tree prior, suggesting such models are a poor fit under heterogeneous fossil preservation. We
apply recently defined trait-by-environment associations to classify a gradient of transitions from
marine to terrestrial lifestyles. We estimate that crabs left the marine environment at least seven
and up to 17 times convergently, and returned to the sea from non-marine environments at least
twice. Although the most highly terrestrial- and many freshwater-adapted crabs are concentrated
in Thoracotremata, Bayesian threshold models of ancestral state reconstruction fail to identify
shifts to higher terrestrial grades due to the degree of underlying change required. Lineages
throughout our tree inhabit intertidal and marginal marine environments, corroborating the
inference that the early stages of terrestrial adaptation have a lower threshold to evolve. Our
framework and extensive new fossil and natural history datasets will enable future comparisons
of non-marine adaptation at the morphological and molecular level. Crabs provide an important
window into the early processes of adaptation to novel environments, and different degrees of
evolutionary constraint that might help predict these pathways.
... In fact, a hexagonal tile pattern is obtained by following the principle of circumference minimization due to cortical tension as described above. However, ordered tetragonal tile patterns can be found in the compound eyes of several different arthropod groups, such as the decapod crustaceans (crabs, lobsters, and shrimp) (Luque et al., 2019), the extinct trilobites (Strausfeld et al., 2016), as well as groups within at least a few insect orders (e.g., Odonata, Diptera, Hymenoptera). These occurrences suggest that the tile pattern of compound eyes is not controlled solely according to physical stability based on the same principle as that of soap bubbles. ...
... Based on the criteria mentioned by Herter [24], Kühl [29], Schäfer [51], and Hartnoll [21], typical P5-swimmers are Liocarcinus depurator, "Polybius" henslowii Leach, 1820 (we here follow [12] in putting Polybius in quotation marks as the genus has repeatedly been recognized to be nested within Liocarcinus Stimpson, 1871, which is then paraphyletic; see also [40,54]), Macropipus rugosus (Doflein, 1904), Necora puber (Linnaeus, 1767) and Parathranites orientalis (Miers, 1886) (all six Carcinidae MacLeay, 1838 sensu [12]), Ovalipes ocellatus (Herbst, 1799) (Geryonidae Colosi, 1923), Callinectes sapidus Rathbun, 1896 and Portunus inaequalis (Miers, 1881) (both Portunidae Rafinesque 1815; Portunus has recently been shown to be paraphyletic [34]; The recent suggestion to transfer Portunus inaequalis into a genus Achelous came too late to be fully considered herein [28]). Outgroup taxa are Sternodromia monodi (Forest & Guinot, 1966) representing Dromiidae De Haan, 1833 of Podotremata Guinot, 1977 (which may be paraphyletic, see for example Luque et al. [32]), Eriochier sinensis H. Milne Edwards, 1853 and Varuna litterata (J. C. Fabricius, 1798) as representatives of Thoracotremata Guinot, 1977, the putative sister taxon to Heterotremata Guinot, 1977 (to which Portunoidea belong), and Medorippe lanata (Linnaeus, 1767) (Dorippidae MacLeay, 1838, Dorippoidea MacLeay, 1838) as putative basal heterotrematan species [9,10,19,25]). ...
... Shape and proportion of overall axial skeleton An overview of axial skeleton morphology in most of the taxa is given in Figs. 1, 2, 3, 4, 5 and 6. High resolution 3D models of these species' axial skeletons including some of the extrinsic musculature of the pereiopods are supplied in the "Appendix" in Additional files 2, 3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27. Low resolution 3D models of some of the species' axial skeletons (Medorippe lanata, "Polybius" henslowii, Thia scutellata, Ovalipes ocellatus, Libystes nitidus) without extrinsic musculature are supplied in the "Appendix" in Additional files 28,29,30,31,32. No apparent differences in the shape of the axial skeleton or the extrinsic musculature of the pereiopods are found between sexes, except in Medorippe lanata (see below). No distinct differences were found between a juvenile and adult specimen of Necora puber either. ...
Portunoidea (Heterotremata) is a morphologically disparate taxon of true crabs (Brachyura) best-known for many of its representatives being considered “swimming crabs”. The term “swimming crab”, however, sometimes refers to a distinct taxon (traditionally to Portunidae within Portunoidea), and sometimes to a certain morphotype in which the 5th pereiopod (P5) has a specific shape that facilitates swimming. We use the term “P5-swimming crab” or “P5-swimmer” herein, not only to restrict it to the morphotype, but also to distinguish the swimming in question from other kinds of swimming in Brachyura. The evolution of P5-swimming crabs has not yet been satisfactorily investigated. In particular, it is not known whether the morphotype evolved several times independently in different lineages of Portunoidea or whether it evolved only once and was lost in several lineages. Ours is the first approach combining molecular with morphological data to result in a new phylogenetic positioning of some members of Portunoidea. For the first time, data from the axial skeleton and extrinsic musculature are used. Morphological examinations reveal that the axial skeleton and extrinsic musculature in P5-swimming crabs are more diverse than previously thought, with the exception of the P5 anterior coxa muscle, which originates at the median plate in all P5-swimmers. Ancestral state reconstructions based on parsimony reveal that the stem species of Portunoidea already showed the morphotype of a P5-swimming crab, but with a long merus which probably resulted in less effective P5-swimming than in extant P5-swimming crab species with a short merus. Several other extant taxa represent a reversal of the P5-swimmer morphotype to varying degrees, with some extant species showing a complete reversal of unambiguous P5-swimming crab character states—one example being the well-known common shore crab Carcinus maenas . The absence of a connection between interosternite 7/8 and the sella turcica (the secondary loss of the “brachyuran sella turcica”) in the stem species of Heterotremata, resulting in a junction plate which forms a cavity that offers room and attachment sites for the P5 extrinsic musculature is uncovered as preadaptation to the P5-swimmer morphotype in Heterotremata. This preadaptation is missing in Podotremata and Thoracotremata, the other two traditional main taxa of Brachyura.
... Specifically, semiterrestrial crabs (for example, fiddler crabs; Fig. 1a, centre) 10 possess flattened corneas that enable amphibious imaging. Other types of crab, such as terrestrial [16][17][18][19][20] and aquatic [21][22][23] crabs (for example, vampire crabs and spanner crabs; Fig. 1a, left and right, respectively) that do not need amphibious imaging have curved corneas. Supplementary Table 1 provides more information about the ocular structures of crab families. ...
Biological visual systems have inspired the development of various artificial visual systems including those based on human eyes (terrestrial environment), insect eyes (terrestrial environment) and fish eyes (aquatic environment). However, attempts to develop systems for both terrestrial and aquatic environments remain limited, and bioinspired electronic eyes are restricted in their maximum field of view to a hemispherical field of view (around 180°). Here we report the development of an amphibious artificial vision system with a panoramic visual field inspired by the functional and anatomical structure of the compound eyes of a fiddler crab. We integrate a microlens array with a graded refractive index and a flexible comb-shaped silicon photodiode array on a spherical structure. The microlenses have a flat surface and maintain their focal length regardless of changes in the external refractive index between air and water. The comb-shaped image sensor arrays on the spherical substrate exhibit an extremely wide field of view covering almost the entire spherical geometry. We illustrate the capabilities of our system via optical simulations and imaging demonstrations in both air and water. In an approach inspired by the functional and anatomical structure of fiddler crab eyes, an amphibious and panoramic artificial vision system can be created by integrating a flat and a microlens array with a graded refractive index as well as a flexible comb-shaped silicon photodiode array on a spherical structure.
... Meyer-Rochow and Gál (2004) suggested that such clear zones enhance light sensitivity and they may be relatively large in species inhabiting dim-light environments. Apposition eyes are thought to be an ancestral crustacean trait and may be present in the early life stages of most decapods (reviewed in Luque et al., 2019). However, the compound eyes of slipper lobsters with their superposition optical structures may improve vision under dimlight conditions (reviewed in Meyer-Rochow, 2001;Cronin and Porter, 2008). ...
... However, the compound eyes of slipper lobsters with their superposition optical structures may improve vision under dimlight conditions (reviewed in Meyer-Rochow, 2001;Cronin and Porter, 2008). Such refracting superposition eyes have also been reported for other benthic decapods in deep-water systems, such as the crab superfamilies Homolodromioidea, Dromioidea, and Homoloidea (Luque et al., 2019), and this type of eye is associated with some nocturnal arthropods (Meyer-Rochow and Gál, 2004). Given their possession of these specialized eye structures, we infer that these slipper lobsters have excellent dim-light vision, which would assist them in their nocturnal activity patterns Goldstein et al., 2015) and facilitate adaptation to habitats of different depths. ...
... The 90% confidence level is shown (dashed lines). crustacean visual systems have been shown to vary according to ecological and phylogenetic constraints (reviewed in Luque et al., 2019). Therefore, a trade-off between visual sensitivity and temporal resolution has been hypothesized, since increased photoreceptor integration time may enhance photon capture and contribute to greater sensitivity to dim light. ...
The light characteristics of an ecosystem drive evolutionary adaptations in visual traits, enhancing the diversity and abundance of species living there. The visual systems of crustaceans are highly diverse and often correspond to the optical properties of their preferred environments. Although habitat depth is known to greatly influence visual specialization in marine crustaceans, it remains unclear whether depth drives visual adaptions in nocturnal species. Slipper lobsters (Scyllaridae) are nocturnal benthic marine crustaceans distributed throughout a wide range of depths. In order to understand the visual adaptive capabilities of slipper lobsters inhabiting different depths, we characterized the eye structures of a shallow-water species (Parribacus japonicas), an intermediate-depth species (Scyllarides squammosus) and a deep-water species (Ibacus novemdentatus). Moreover, we measured by electroretinogram (ERG) the spectral sensitivities and temporal resolutions for each species using the following light stimuli: UV (λmax 386 nm), blue (λmax 462 nm), green (λmax 518 nm), yellow (λmax 590 nm), and red (λmax 632 nm). Our histological experiments show that all three species possess a typical superposition compound eye with square facets, and their ERG measurements revealed a single sensitivity peak for each species. Notably, peak spectral sensitivity corresponded to habitat depth, with the estimated peak for I. novemdentatus (493.0 ± 9.8 nm) being similar to that of S. squammosus (517.4 ± 2.1 nm), but lower than that of P. japonicus (537.5 ± 9.9 nm). Additionally, the absolute sensitivities at respective peak wavelengths for I. novemdentatus and P. japonicus were higher than that of S. squammosus. No differences were observed among the three species for maximum critical flicker fusion frequency (CFFmax) across light stimuli. However, P. japonicus had lower CFFmax values than the other two species. These data suggest that all three nocturnal slipper lobsters are likely monochromatic and well adapted to dim light environments. Significantly, the deep-water slipper lobster displayed higher spectral sensitivities at shorter wavelengths than the shallow water species, but temporal resolution was not compromised.
... Eubrachyurans are the most diverse group of crabs today in terms of anatomy, ecology, and species richness. They fall into two main categories based on the position of their sexual openings: the heterotremes (including primarily and secondarily freshwater crabs), with openings on the legs in males and thorax in females, and thoracotremes (including semiterrestrial and terrestrial crabs), with openings on the thorax in both sexes (4)(5)(6). The consensus is that heterotremes and thoracotremes together form a monophyletic clade Eubrachyura (7)(8)(9)(10). ...
Amber fossils provide snapshots of the anatomy, biology, and ecology of extinct organisms that are otherwise inaccessible. The best-known fossils in amber are terrestrial arthropods—principally insects—whereas aquatic organisms are rarely represented. Here we present the first record of true crabs (Brachyura) in amber—from the Cretaceous of Myanmar (~100–99 Ma). The new fossil preserves large compound eyes, delicate mouthparts, and even gills. This modern-looking crab is nested within crown Eubrachyura, or ‘higher’ true crabs, which includes the majority of brachyuran species living today. The fossil appears to have been trapped in a brackish or freshwater setting near a coastal to fluvio-estuarine environment, bridging the gap between the predicted molecular divergence of non-marine crabs (~130 Ma) and their younger fossil record (latest Cretaceous and Paleogene, ~75 to 50 Ma) while providing a reliable calibration point for molecular divergence time estimates for ‘higher’ crown eubrachyurans.
... Anatomically, these crabs lie in between Anomura and Eubrachyura, and all current data strongly support a paraphyletic podotreme grade with brachyuran affinity. [31] Analysis of eight Sanger sequenced genes including 58 of ∼100 brachyuran families, [27] analyses of mitogenomes, [30,32] and a recent transcriptomic analysis [33] each recovered podotreme paraphyly (the former with weak support). Relationships recovered among podotremes were entirely contradictory between those analyses. ...
... Meanwhile, morphological trees, including fossils, have sampled more extensively from podotreme lineages. [2,31] Thus, a major goal of future research should represent all meiuran families with morphological data, and all extant families with strongly supported phylogenomic data, for a well-resolved total evidence phylogeny. ...
A fundamental question in biology is whether phenotypes can be predicted by ecological or genomic rules. At least five cases of convergent evolution of the crab-like body plan (with a wide and flattened shape, and a bent abdomen) are known in decapod crustaceans, and have, for over 140 years, been known as "carcinization." The repeated loss of this body plan has been identified as "decarcinization." In reviewing the field, we offer phylogenetic strategies to include poorly known groups, and direct evidence from fossils, that will resolve the history of crab evolution and the degree of pheno-typic variation within crabs. Proposed ecological advantages of the crab body are summarized into a hypothesis of phenotypic integration suggesting correlated evolution of the carapace shape and abdomen. Our premise provides fertile ground for future studies of the genomic and developmental basis, and the predictability, of the crab-like body form.
... As of yet, molecular phylogenetics has been insufficient to resolve the puzzle of podotremes, therefore our depiction of their extant relationships in Figure 2 relies on morphological data. Anatomically, these crabs lie in between Anomura and Eubrachyura, though all current data strongly support a paraphyletic podotreme grade with brachyuran affinity (Luque et al. 2019a). Analysis of eight Sanger sequenced genes including 58 of ~100 brachyuran families (Tsang et al. 2014), analyses of mitogenomes (Tan et al. 2018b(Tan et al. , 2019, and a recent transcriptomic analysis ) each recovered podotreme paraphyly (the former with weak support). ...
... Of 11 extant podotreme families, however, over one third lack molecular data: no sequences have been published for Poupiniidae, Lyreididae, and Phyllotymolinidae, and only a single 18S sequence is available for Homolodromiidae. Meanwhile, morphological trees, including fossils, have sampled more extensively from podotreme lineages (Luque et al. 2019a(Luque et al. , 2019b. Thus, a major goal of future research should represent all meiuran families with morphological data, and all extant families with strongly supported phylogenomic data, for a well-resolved total evidence phylogeny. ...
A fundamental question in biology is whether phenotypes can be predicted by ecological or genomic rules. For over 140 years, convergent evolution of the crab-like body plan (with a wide and flattened shape, and a bent abdomen) at least five times in decapod crustaceans has been known as 'carcinization'. The repeated loss of this body plan has been identified as 'decarcinization'. We offer phylogenetic strategies to include poorly known groups, and direct evidence from fossils, that will resolve the pattern of crab evolution and the degree of phenotypic variation within crabs. Proposed ecological advantages of the crab body are summarized into a hypothesis of phenotypic integration suggesting correlated evolution of the carapace shape and abdomen. Our premise provides fertile ground for future studies of the genomic and developmental basis, and the predictability, of the crab-like body form.
Animal colour vision is based on comparing signals from different photoreceptors. It is generally assumed that processing different spectral types of photoreceptor mainly serves colour vision. Here I propose instead that photoreceptors are parallel feature channels that differentially support visual-motor programmes like motion vision behaviours, prey capture and predator evasion. Colour vision may have emerged as a secondary benefit of these circuits, which originally helped aquatic vertebrates to visually navigate and segment their underwater world. Specifically, I suggest that ancestral vertebrate vision was built around three main systems, including a high-resolution general purpose greyscale system based on ancestral red cones and rods to mediate visual body stabilization and navigation, a high-sensitivity specialized foreground system based on ancestral ultraviolet cones to mediate threat detection and prey capture, and a net-suppressive system based on ancestral green and blue cones for regulating red/rod and ultraviolet circuits. This ancestral strategy probably still underpins vision today, and different vertebrate lineages have since adapted their original photoreceptor circuits to suit their diverse visual ecologies.
The raninid genus Cyrtorhina Monod, 1956, is revised and restricted to Cyrtorhina granulosa Monod, 1956, from West Africa. A new genus, Flaberhina, is established for C. balabacensis Serène, 1971 from the Philippines and New Caledonia. Despite their superficial similarities, the two genera can easily be separated by the structures of the carapace, eye, antenna, pterygostome, thoracic sternum, pleon and penis. The taxonomy of the subfamily Cyrtorhininae Guinot & Ng, 2020, which contains both fossil and extant taxa, is also reviewed.
