• Henningsen Zacho posted an update 6 months, 4 weeks ago

    We find no evidence of all-unisexual spinicaudatan taxa (clam shrimp) in the fossil record, but do find evidence of both androdioecious and dioecious clam shrimp. We find that clades with many androdioecious species are less speciose but persist longer than their mostly dioecious counterparts. These data suggest that all-unisexual lineages likely do not persist long whereas mixtures of unisexual and sexual breeding can persist for evolutionarily long periods but tend to produce fewer species than mostly sexual breeding.This special volume of Zoological Studies is the result of a symposium entitled “Fossil and Modern Clam Shrimp” held at the midyear meeting of The Crustacean Society in May of 2019. This symposium is the first ever focusing on clam shrimp, and the first conference where both palaeontologists and biologists specialising in these animals were able to come together. The papers presented here provide insight into the palaeontology, biology, ecology, taxonomy and phylogeny of the clam shrimp. This chapter introduces the symposium, its aims, and the resulting research, presented in the subsequent chapters. In addition, in this symposium we celebrate our great friend Brian V. Timms, who has mentored so many of us, brought us on various excursions across Australia, and has done more to advance Australian branchiopod studies than anyone else in history.This study provides a checklist of cladocerans and evaluates the species richness and composition of this order in Côte d’Ivoire. A checklist of cladocerans was created by evaluating data from the literature and fauna surveys focused on zooplankton in different types of aquatic environments over the past 50 years. In total, 39 Cladocera species have been reported from Côte d’Ivoire. This richness includes 24 genera and seven families, with Chydoridae being the most diversified family (16 species, 41% of the total Cladocera diversity in Côte d’Ivoire), followed by Daphniidae (eight species, 21%); Moinidae (four species, 10%); Bosminidae, Macrothricidae, and Sidiidae (three species, 8% each); and Ilyocriptidae (two species, 5%). Ceriodaphnia cornuta, Moina micrura, and Diaphanosoma excisum were the most frequently encountered species.Some nudibranchs are predators of scleractinian corals, but little is known about their diversity. Here we describe Phestilla fuscostriata sp. nov., the first species of nudibranch that preys on Pavona decussata, a structure-forming agariciid species in the South China Sea. This new species has a white body with brown pigmentation on the dorsum and cerata, and exhibits excellent mimicry by matching the colour of its coral host. The nudibranch lays crescent-shaped egg masses on the coral surface, where the embryos develop and hatch in 2-3 weeks. This new species possesses a large number of cerata that are arranged in widely-spaced rows, with each row having one dorsal ceras and zero to several ventral cerata, which distinguishes it from all other congeneric species. A comparison of the mitochondrial COI and 16S rRNA genes and the nuclear H3 gene between P. fuscostriata sp. nov. and other Phestilla spp. found that their interspecific distances are large enough to justify the recognition of the new species.Phyllohartmania Pettibone, 1961 is a monotypic genus in the subfamily Polynoinae Kinberg, 1856. It is characterized by having lateral antennae with ventral ceratophores, cephalic peaks and neuropodia with pre-chaetal lobes being longer than post-chaetal lobes. Phyllohartmania taylori Pettibone, 1961 was described using only one specimen collected at Bird Point, Seahorse Key, Florida. During a study of Polynoids from the Grand Caribbean to corroborate features and records, the holotype and additional material of P. taylori housed at the National Museum of Natural History, Smithsonian Institution were examined and an unknown genus of Eulagiscinae Pettibone, 1997 confused with Phyllohartmania was found; the present study erects this as a new genus. Kristianides gen. nov. is distinguished by having prostomium without cephalic peaks, lateral antennae inserted terminally on indistinct ceratophores and notopodia and neuropodia with projecting acicular lobes well developed. Kristianides cylindricum sp. nov. differs from the other species of Eulagiscinae by having ventral lamellae; 15 pairs of elytra with fringe of papillae, surface with sclerotized microtubercles and macrotubercles; being conical the microtubercles and cylindrical the macrotubercles. In addition, two records of P. Sodium Desoxycholate taylori from the northern Gulf of Mexico are published herein, as is a taxonomic key to differentiate Kristianides gen. nov. from its congeners in Eulagiscinae. This finding also increases the number of species with ventral lamellae, a convergent feature.Lacydonia japonica sp. nov. (Annelida, Lacydoniidae) is described based on material found in sediments collected off the Pacific coast of northern Honshu, Japan, at depths of 262 m and 407 m. The sediments were obtained by a remotely operated vehicle equipped with a suction sampler during a Tohoku Ecosystem-Associated Marine Sciences (TEAMS) project in 2019. Lacydonia japonica sp. nov. belongs to the eyeless group of lacydoniids and is discriminated from the morphologically most similar congener, Lacydonia papillata Uschakov, 1958 by its reddish pigments on both the dorsal and ventral parapodial cirri and four pigment spots on the pygidium. To assess the phylogenetic position of the new species among other lacydoniids for which sequence data are available in public databases, analyses were performed using the mitochondrial cytochrome c oxidase subunit I (COI) and 16S rRNA, as well as the nuclear 18S rRNA and 28S rRNA genes. We additionally obtained some lacydoniids by sledging off western Japan, but these were severely fragmented and broken during collection. Using the paucity of morphological data, they were left unidentified as Lacydonia sp. but included in the molecular analyses. Genetic distances between Lacydonia eliasoni Hartmann-Schröder, 1996, Lacydonia japonica, and Lacydonia sp. off western Japan were 10.4-17.1% uncorrected p-distance (11.3-18.6% K2P) in terms of 658-bp COI sequences.

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