The History of Sexual Dimorphism in Ostracoda (Arthropoda, Crustacea) Since the Palaeozoic

Ozawa, Hirokazu

doi:10.5772/55329

Cited by 22 publications

(27 citation statements)

References 41 publications

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“…The morphological differences between males and females, called sexual dimorphism, are known for ostracods since the Ordovician (Moore ). A recent compilation distinguishes three parts of the ostracods' body (carapace and soft parts) prone to sexually dimorphic patterns (Ozawa ): The appendages with the examples of males' asymmetric or larger limbs and the presence/absence of substructures on some limbs of living Podocopida and Myodocopida (Abe and Vannier , ; Ikeya and Abe ). Different eye structures are also documented for some Myodocopida (Abe and Vannier ; Ikeya and Abe ). The surface ornamentation of some female Podocopida is heavier than their male counterparts (Tsukagoshi ; Kamiya et al .…”

Section: Methodsmentioning

confidence: 99%

Precocious sexual dimorphism and the Lilliput effect in Neo‐Tethyan Ostracoda (Crustacea) through the Permian–Triassic boundary

et al. 2015

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The Elikah River section spanning the Lopingian (Late Permian) to the Griesbachian (Early Triassic) time interval in the Central Alborz Mountains (north Iran) was sampled for ostracod analysis. We report 79 species distributed among 38 genera. Four new species are described: Acratia? pervagata Forel sp. nov., Microcheilinella alborzella Forel sp. nov., Basslerella superarella Crasquin sp. nov. and Cavellina nesenensis Crasquin sp. nov. The ontogeny of 13 species is described and sexual dimorphism in the genus Microcheilinella is here undoubtedly recognized for the first time. Six species show precocious sexual dimorphism of their carapace as early as A‐5 juvenile. The Lilliput effect is for the first time recorded and quantified for two species. Rare long‐time span Palaeocopida species, known throughout the entire Permian, document relatively long‐term evolution, including the size and growth rate modifications associated with the earlier appearance of carapace sexual dimorphism through time. These patterns might be related to the Guadalupian–Lopingian events and/or to climatic modifications occurring during the Permian interval.

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Section: Methodsmentioning

confidence: 99%

Precocious sexual dimorphism and the Lilliput effect in Neo‐Tethyan Ostracoda (Crustacea) through the Permian–Triassic boundary

et al. 2015

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“…The somewhat oval carapace outline, the shape of the male copulatory organ, and the chaetotaxy of the mandibula and the maxillula of Loxoconcha sesokoensis sp. nov., are clearly different from those of other Loxoconcha species living in Japan and adjacent areas as shown by Ishizaki (1968), Okubo (1980), Nakao & Tsukagoshi (2002) and Ozawa (2013).…”

Section: Loxoconcha Santosi Sp Nov (Figs 6-9)mentioning

confidence: 99%

Three new species of the genus Loxoconcha (Crustacea, Ostracoda, Podocopida) from the Okinawa Islands, southern Japan

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Tsukagoshi

2014

Zootaxa

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Three new species of Ostracoda, Loxoconcha noharai sp. nov., L. santosi sp. nov. and L. sesokoensis sp. nov., are described from the Okinawa Islands, southern Japan. The two species Loxoconcha noharai sp. nov. and L. santosi sp. nov. live in estuaries, whereas the species L. sesokoensis sp. nov. lives in coral reefs. These species can be easily distinguished from other previously described Loxoconcha species by their morphological differences, mainly in the male copulatory organ, and distribution pattern of their pore systems. In addition, L. sesokoensis sp. nov. is suggested to be phylogenetically apart from any other Loxoconcha species which have been reported so far from Japan and the adjacent seas.

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“…Because of their strongly calcified valves, cytheroids have an extremely rich fossil record that extends back to the Ordovician [50, 51]. Sexual dimorphism of the valves depends on the internal soft anatomy and underlying biology, and thus the fossil record of these structures represents a valuable archive of character evolution.…”

Section: Discussionmentioning

confidence: 99%

Correlation between investment in sexual traits and valve sexual dimorphism in Cyprideis species (Ostracoda)

et al. 2017

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Assessing the long-term macroevolutionary consequences of sexual selection has been hampered by the difficulty of studying this process in the fossil record. Cytheroid ostracodes offer an excellent system to explore sexual selection in the fossil record because their readily fossilized carapaces are sexually dimorphic. Specifically, males are relatively more elongate than females in this superfamily. This sexual shape difference is thought to arise so that males carapaces can accommodate their very large copulatory apparatus, which can account for up to one-third of body volume. Here we test this widely held explanation for sexual dimorphism in cytheroid ostracodes by correlating investment in male genitalia, a trait in which sexual selection is seen as the main evolutionary driver, with sexual dimorphism of carapace in the genus Cyprideis. We analyzed specimens collected in the field (C. salebrosa, USA; C. torosa, UK) and from collections of the National Museum of Natural History, Washington, DC (C. mexicana). We digitized valve outlines in lateral view to obtain measures of size (valve area) and shape (elongation, measured as length to height ratio), and obtained several dimensions from two components of the hemipenis: the muscular basal capsule, which functions as a sperm pump, and the section that includes the intromittent organ (terminal extension). In addition to the assessment of this primary sexual trait, we also quantified two dimensions of the male secondary sexual trait—where the transformed right walking leg functions as a clasping organ during mating. We also measured linear dimensions from four limbs as indicators of overall (soft-part) body size, and assessed allometry of the soft anatomy. We observed significant correlations in males between valve size, but not elongation, and distinct structural parts of the hemipenis, even after accounting for their shared correlation with overall body size. We also found weak but significant positive correlation between valve elongation and the degree of sexual dimorphism of the walking leg, but only in C. torosa. The correlation between the hemipenis parts, especially basal capsule size and male valve size dimorphism suggests that sexual selection on sperm size, quantity, and/or efficiency of transfer may drive sexual size dimorphism in these species, although we cannot exclude other aspects of sexual and natural selection.

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The History of Sexual Dimorphism in Ostracoda (Arthropoda, Crustacea) Since the Palaeozoic

Cited by 22 publications

References 41 publications

Precocious sexual dimorphism and the Lilliput effect in Neo‐Tethyan Ostracoda (Crustacea) through the Permian–Triassic boundary

Precocious sexual dimorphism and the Lilliput effect in Neo‐Tethyan Ostracoda (Crustacea) through the Permian–Triassic boundary

Three new species of the genus Loxoconcha (Crustacea, Ostracoda, Podocopida) from the Okinawa Islands, southern Japan

Correlation between investment in sexual traits and valve sexual dimorphism in Cyprideis species (Ostracoda)

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