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The Devonian saw the emergence and subsequent diversification of the clam shrimp. To date, there are no credible records of any clam shrimp prior to the Devonian. Therefore, discoveries and taxonomic studies of early forms, especially the Early Devonian species, are essential to broaden our knowledge of the origin and early evolution of clam shrimp. An Early Devonian clam shrimp community that consists of four species, Cornia cheni n. sp., Pseudestheria cf. P. diensti, Palaeolimnadiopsis zhangi n. sp., and ?Palaeolimnadia sp. is described and discussed in detail in this study. These species are the oldest clam shrimp in China and among the oldest worldwide. This discovery indicates that clam shrimp communities with high diversity existed since the late Early Devonian and that their early forms may have had a profound effect on the origin and evolutionary trends of the following forms.

Large branchiopods are a key component of the fauna of temporary ponds and play an important role in the functioning of these vulnerable ecosystems. Owing to the establishment of new settlements and agricultural expansion, temporary ponds in Tanzania are disappearing at an alarming rate whilst little is known about their diversity and ecology. We contrasted temporary ponds from a protected area with those in communal lands to detect associations between land-use types and large branchiopod community structure. Six large branchiopod species were collected, five of which have been previously reported from Southern Africa, whilst one turned out to be new to science: Streptocephalus manyarensis n.sp. Kafula and Brendonck (2023). The clam shrimp Cyzicus sp., fairy shrimps Streptocephalus lamellifer Thiele (1900) and S. bourquinii Hamer and Appleton (1993) were the most abundant and widely occurring. Variation in large branchiopod community structure was explained by the presence of Nothobranchius killifish and orthophosphate concentration. The large branchiopod community structure was different in settlement and protected areas. Our study on the occurrence and structure of large branchiopod communities in relation to land-use types serves as a base for formulation of guidelines and management tools to regulate land-use practices adjacent to temporary pond ecosystems.

With about 500 known species worldwide, the large brachiopods are a relatively small group of primitive crustaceans. With few exceptions they live in temporary aquatic systems that are most abundant in arid and semi arid areas. As many regions remain unexplored and as especially the number of species in clam shrimps and tadpole shrimps is underestimated due to difficult identification, the species list will increase with future surveys. The Branchiopoda are monophyletic, but inter-ordinal relationships, as well as many evolutionary relationships at lower taxonomic levels are still unclear. Ongoing molecular studies will more accurately depict species diversity and phylogenetic patterns. With the exception of some anostracan families, most families are not restricted to the northern or southern hemisphere or specific zoogeographical regions. Large branchiopods are used for the assessment of the quality and function of temporary wetlands. Due to the reduction in number and quality of temporary wetlands, several species became endangered and are red listed by the IUCN.

This study main goal was to characterize biodiversity in tropical pristine wetlands of two protected areas from central Brazil under a multi-taxonomic approach, with special interest on the distribution and identity of those taxa that most represent these reference conditions. Samplings were conducted during dry and rainy seasons (2009), in nine wetlands. We reported 114 herbaceous macrophytes, 334 algae/cyanobacteria, 45 microcrustaceans and 139 testate amoebae. Macrophytes presented the highest beta diversity compared to the other groups (βw = 3.2), while microcrustaceans showed the lowest one (βw = 1.4). The microorganism diversity associated with the dominating emergent macrophytes (e.g., Poaceae and Cyperaceae) was mainly composed of zygnematophycean algae, branched heterocytous cyanobacteria, along with Chydoridae (Cladocera) and Cyclopoida (Copepoda) microcrustaceans and Lesquereusiidae testate amoebae. Many tropical rare/endemic taxa were reported, e.g., among genera Parallela (green algae) , Placocista and Quadrulella (testate amoebae) , Celsinotum, Ephemeroporus, Metacyclops and Paracyclops (microcrustaceans); also, the genus Paralimnetis (Laevicaudata) is cited for the first time in Brazil. These findings reinforce these small wetlands as potential biodiversity hotspots and stepping stones for dispersing organisms. Finally, the presence of temporary environments among Cerrado wetlands may contribute as an additional beta diversity driver that deserves more attention in future studies.

Clam shrimps are freshwater branchiopod crustaceans which often present complicated breeding systems including asexual reproduction (parthenogenesis) and mixed mating systems (in androdioecious species both selfing and outcrossing occurs due to the co-presence of hermaphrodites and males). Reproductive patterns of Spinicaudata, which contains most clam shrimp species, have received much attention. Another group of clam shrimps, Laevicaudata, which holds a key position in branchiopod phylogeny, has practically not been studied. As a part of the mating process, males clasp to the carapace margin of the females with a pair (or two pairs) of anterior trunk limbs modified as claspers. Previous studies have shown that clasper morphology is important in a phylogenetic context, and that some parts of the claspers in Spinicaudata and Laevicaudata may have undergone a remarkable parallel evolution. Here we have used video microscopy to study aspects of the mating behaviour, egg extrusion, and fertilization in Lynceus brachyurus (Laevicaudata). It is shown that fertilization is likely to be external and that the peculiar tri-lobed lateral lamellae of female's hind body assist in guiding the egg mass to the exopodal egg carriers where they are collected by their distal setation. The functional morphology of the male claspers was studied in detail by close-up video recordings. The movable \"finger\" of the clasper bends around the female's carapace edge and serves to hold the female during mating. The larger palp grasps around the female carapace margin in a way very similar to the movable \"finger\", possibly indirectly providing sensory input on the \"finger\" position. A brief comparative study of the claspers of a spinicaudatan clam shrimp showed both similarities and differences to the laevicaudatan claspers. The presence of two pairs of claspers in Spinicaudata seems to give males a better hold of the female which may play a role during extended mate guarding.

A survey of the large branchiopod fauna of the Eastern Cape Karoo region of South Africa was undertaken to provide baseline biodiversity information in light of impending shale gas development activities in the region. Twenty-two waterbodies, including nine dams and thirteen natural depression wetlands, were sampled during November 2014 and April 2015. A total of 13 species belonging to four orders were collected, comprising five anostracans, one notostracan, six spinicaudatans and one laevicaudatan. was most common, occurring in 46% of the waterbodies. Species co-occurred in 87% of the waterbodies, with a maximum number of six species recorded from the same waterbody. Our new distribution records for , and represent substantial expansions of the previously known ranges for these species. Tarkastad is now the westernmost record for , while Jansenville now constitutes the southernmost record for . Large branchiopod distribution data from previous Eastern Cape records were combined with our current data, demonstrating that a total of 23 large branchiopod species have been recorded from the region to date. As the Karoo is one of the few major shale basins in the world where the natural baseline is still largely intact, this survey forms a basis for future reference and surface water quality monitoring during the process of shale gas exploration/extraction.

Zooplankton generally distributes patchily. Distributional patchiness could be adaptive to survival and reproduction, especially for large branchiopods that live in temporary pools with variable aquatic environments. We focused on spatial utilization by three sympatric large branchiopods in a subtropical temporary pool (Siangtian Pond, northern Taiwan): Branchinella kugenumaensis (Ishikawa, 1895) (Anostraca), Eulimnadia braueriana Ishikawa, 1895 (Spinicaudata), and Lynceus biformis (Ishikawa, 1895) (Laevicaudata). Sampling along transects were conducted across four hydroperiods. The number of adults for each species was recorded to describe patchiness, edge aggregation, and hotspots of peak density. We found that the three species showed patchy distribution, which could reflect resource heterogeneity. Only B. kugenumaensis consistently aggregated toward the edge, and we hypothesize that this distributional tendency correlates with mating behavior. Hotspots of L. biformis were concentrated in the deepest locations, possibly due to late maturation and limited utilization area available for adults. In contrast, the early-maturing E. braueriana was scattered widely throughout the basin without an obvious pattern. Patchy distribution could be a common phenomenon for large branchiopods in temporary pools, whereas species-specific distribution patterns depend on multiple factors.

We present records of 3 clam shrimp species from New York: 2 spinicaudatan species— Eulimnadia agassizii (Agassiz Clam Shrimp; the first record for the state) and Cyzicus sp. (the second record of the genus from the state)—and Lynceus brachyurus (Laevicaudata; Holarctic Clam Shrimp; first reported from New York in 1883, is herein documented from the Hudson Valley). Some of the temporary waters that these species inhabit are protected by wetland regulations, but rain-puddle habitat on or along unimproved roads has no such protection.

Abstract Large branchiopod crustaceans are among the most threatened freshwater invertebrates of the world. They are regarded as a flagship group in the conservation of temporary waters, and knowledge of their ecology and conservation has developed rapidly in recent years, especially in the Mediterranean region. Little is known, however, about population functioning in species associated with vernal pools in cooler temperate areas, despite recent data showing a significant decline in their localities. The present study was conducted in western Poland, on a cluster of vernal pools known to host a Central European diversity hotspot of large branchiopods. We collected data on water and sediment quality, as well as hydroperiod length, to determine their effect on the occurrence of four large branchiopod species present in the ponds during our samplings: Eubranchipus grubii (Anostraca), Lynceus brachyurus (Laevicaudata), Cyzicus tetracerus (Spinicaudata) and Lepidurus apus (Notostraca). According to the statistical analyses, the presence or absence of particular species was affected by hydroperiod length, heavy metal content in the sediments of the marginal zone of the pond, total water phosphorus content, and pH value. Since previous studies show that deep and relatively small kettle-hole ponds seem to be the most vulnerable to human-induced changes in water nutrient contents and acidification, large branchiopod populations of this type of pools should be the first target for monitoring and active forms of protection, with the aim of maintaining the good water quality. Shallow shore-bursting type ponds are subject to increased heavy metal contamination and require activities reducing the influx of these elements from their agricultural catchment. Possible forms of protection are suggested, and the use of large branchiopods as an umbrella group in temporary waters of temperate climate is also discussed.