Crustacean Taxa Research Articles

Larval neurogenesis in the copepod Tigriopus californicus (Tetraconata, Multicrustacea).

Arthropod early neurogenesis shows distinct patterns that have been interpreted in an evolutionary framework. For instance, crustaceans and Hexapoda form the taxon Tetraconata and share the differentiation of specific neural precursors, the neuroblasts, a character which sets them apart from Chelicerata and Myriapoda. Neuroblasts are relatively large stem cells that generate ganglion mother cells by asymmetric divisions. Ganglion mother cells typically divide once to give rise to neurons and glia cells. In hexapods, neuroblasts segregate from the neuroectoderm before they begin their characteristic proliferative activity. In the crustaceans studied so far, neuroblasts remain in the neuroectoderm. Yet, detailed studies on early neurogenesis of crustaceans at the cellular level are largely restricted to some malacostracan and branchiopod species. Crustaceans are very diverse and likely paraphyletic with respect to hexapods. Hence, knowledge about neural differentiation in other crustacean taxa might contribute to the understanding of evolution of neurogenesis in Tetraconata. Here, we describe the early neurogenesis during naupliar development of the copepod Tigriopus californicus. We show that neuroblasts are present that generate ganglion mother cells, which in turn divide to give rise to neurons of the ventral nerve cord. These two neural precursor cell types and their specific arrangement correspond to what has been found in other crustaceans. One obvious difference concerns the relative size of the neuroblasts, which are not much larger than their progeny. Our results complement the picture of neural differentiation in crustaceans and suggest that superficially located neuroblasts are likely the ancestral condition in Tetraconata.

Crustacean prey in the diet of fishes from deep waters of the Eastern Ionian Sea

The gut analysis of 26 fish species caught in the deep waters of the Eastern Ionian Sea showed that crustaceans were a substantial resource for fish found in deep- water environments, comprising 37 crustacean taxa. Among all species examined, 77% included crustaceans in their guts. Dendrobranchiata/Caridea shrimps were the most frequent crustacean prey found in the guts of almost all examined fishes, with high values of relative abundance (N%). Season (summer, autumn) and fish behaviour (demersal, benthic) were not found to affect the diet of the examined fish species. Galeus melastomus could be considered to be a separate case showing the most diverse diet comprising all the crustacean groups. Differences in the proportion of the main crustacean categories consumed by the examined fish species were observed. The low richness and preference towards specific crustacean taxa or different crustacean species could be considered as an indication of interspecific competition for the same food resource in the oligotrophic waters of the Eastern Mediterranean. The occurrence of different crustacean taxa in the gut of some species through the analysed seasons, could be related to differences in prey availability or to selective preference for certain prey which in turn could be linked to different energetic requirements for growth and reproduction of predators.

An updated checklist of groundwater crustaceans of India

AbstractOnly eight groundwater crustacean species were known in India till the end of 20thcentury. Analysis of about 4000 samples collected during 2000-2016 from diverse groundwater habitats, especially in certain pockets of the deltaic belt of the Rivers Krishna and Godavari in the southeastern peninsular India, has so far yielded about 90 new crustacean taxa. Of these, 67 new species have been described formally, which include, respectively, 34, 27, 3, 2 and 1 species each of Copepoda, Bathynellacea, Amphipoda, Isopoda and Ostracoda. The updated checklist presented herein includes a total of 87 species in 45 genera, 22 families and 8 orders. For each species, the reference to its original description, type locality, distribution, and ecological notes, co-occurring fauna, if any, and sampling method(s) are given. Besides map-pointing the type localities of the species, brief notes are given on the biogeography and conservation.

An insect-like mushroom body in a crustacean brain.

Mushroom bodies are the iconic learning and memory centers of insects. No previously described crustacean possesses a mushroom body as defined by strict morphological criteria although crustacean centers called hemiellipsoid bodies, which serve functions in sensory integration, have been viewed as evolutionarily convergent with mushroom bodies. Here, using key identifiers to characterize neural arrangements, we demonstrate insect-like mushroom bodies in stomatopod crustaceans (mantis shrimps). More than any other crustacean taxon, mantis shrimps display sophisticated behaviors relating to predation, spatial memory, and visual recognition comparable to those of insects. However, neuroanatomy-based cladistics suggesting close phylogenetic proximity of insects and stomatopod crustaceans conflicts with genomic evidence showing hexapods closely related to simple crustaceans called remipedes. We discuss whether corresponding anatomical phenotypes described here reflect the cerebral morphology of a common ancestor of Pancrustacea or an extraordinary example of convergent evolution.

Uniqueness of sampling site contributions to the total variance of macroinvertebrate communities in the Lower Mekong Basin

Species co-occurrence and site-specific characteristics have a great influence on biotic community composition at local scales and thus contribute to large variations at broad spatial scales. In this paper, we studied invertebrate communities in 63 river sites of the Lower Mekong Basin (LMB) sampled over 609thousandkm2. We identified important macroinvertebrate taxa of the component communities (i.e. annelids, crustaceans, mollusks and insects), and key geo-environmental factors that explained the total variance (BDTotal) of the communities at large spatial scale. We used the “Species Contributions to Beta Diversity” (SCBD) and “Local Contributions to Beta Diversity” (LCBD) approaches to partition total beta diversity (BDTotal), identified the important macroinvertebrate taxa (those with high SCBD indices), and estimated the uniqueness of sites in community composition (LCBD indices). SCBD indices showed which taxa were the most important in structuring the four component communities: there were 29 insect taxa, which mainly characterized the upstream sites, and 18 mollusk, 7 annelid and 6 crustacean taxa, which all represented the downstream sites. We used linear regression models to investigate the influence of geo-environmental factors and of component communities on LCBD indices. Our results showed great variation in composition within the LMB (BDTotal=0.80 on a 0-to-1 scale). Five sites of the main channel exhibited significant uniqueness (LCBD indices) in community composition. One of them was a hotspot location occupied by a community with exceptional taxonomic composition, which should be protected. Four other sites were degraded by human activity and in need of restoration. Multiple regressions indicated that the global LCBD indices are better explained by the environmental factors, i.e. water conductivity, river depth and Secchi depth (adjusted R2=0.26), than by the geographical factors. Among the component communities, mollusks’ and insects’ LCBDs were the determinants responsible for the variation in the global LCBD indices (adjusted R2=0.84). The uniqueness in community composition of the sites (i.e. LCBDs) that we estimated provides useful ecological information, which could be used to support restoration and conservation planning for the LMB.

A Phylogenomic Solution to the Origin of Insects by Resolving Crustacean-Hexapod Relationships

Insects, the most diverse group of organisms, are nested within crustaceans, arguably the most abundant group of marine animals. However, to date, no consensus has been reached as to which crustacean taxon is the closest relative of hexapods. A majority ofstudies have proposed that Branchiopoda (e.g., fairy shrimps) is the sister group of Hexapoda [1-7].However, these investigations largely excluded twoequally important taxa, Remipedia and Cephalocarida. Other studies suggested Remipedia [8-11] orRemipedia+ Cephalocarida [12, 13] as potential sister groups of hexapods, but they either did notinclude Cephalocarida or used only Sanger sequence data and morphology [9, 12]. Here we present the first phylogenomic study specifically addressing the origins of hexapods, including transcriptomes for two species each of Cephalocarida and Remipedia. Phylogenetic analyses of selected matrices, ranging from 81 to 1,675 orthogroups and up to 510,982 amino acid positions, clearly reject asister-group relationship between Hexapoda and Branchiopoda [1-7]. Nonetheless, support for a hexapod sister-group relationship to Remipedia or to Cephalocarida-Remipedia was highly dependent on the employed analytical methodology. Further analyses assessing the effects of gene evolutionary rate and targeted taxon exclusionsupport Remipedia as the sole sister taxon of Hexapoda and suggest that the prior grouping of Remipedia+ Cephalocarida is an artifact, possibly due to long branch attraction and compositional heterogeneity. We further conclude that terrestrialization of Hexapoda probably occurred in the late Cambrian to early Ordovician, an estimate that is independent of their proposed sister group [4, 8, 12, 14].

Common evolutionary trends underlie the four-bar linkage systems of sunfish and mantis shrimp.

Comparative biomechanics offers an opportunity to explore the evolution of disparate biological systems that share common underlying mechanics. Four-bar linkage modeling has been applied to various biological systems such as fish jaws and crustacean appendages to explore the relationship between biomechanics and evolutionary diversification. Mechanical sensitivity states that the functional output of a mechanical system will show differential sensitivity to changes in specific morphological components. We document similar patterns of mechanical sensitivity in two disparate four-bar systems from different phyla: the opercular four-bar system in centrarchid fishes and the raptorial appendage of stomatopods. We built dynamic linkage models of 19 centrarchid and 36 stomatopod species and used phylogenetic generalized least squares regression (PGLS) to compare evolutionary shifts in linkage morphology and mechanical outputs derived from the models. In both systems, the kinematics of the four-bar mechanism show significant evolutionary correlation with the output link, while travel distance of the output arm is correlated with the coupler link. This common evolutionary pattern seen in both fish and crustacean taxa is a potential consequence of the mechanical principles underlying four-bar systems. Our results illustrate the potential influence of physical principles on morphological evolution across biological systems with different structures, behaviors, and ecologies.

Spring and autumn spatial distribution of zooplankton carbon requirement across the Mediterranean Sea

ABSTRACTZooplankton represents a key contributor to the ocean biological pump through its consumption of sinking and suspended carbon. A specific and highly sensitive method to evaluate zooplankton carbon requirement from the sinking flux is through the estimation of the activity of the electron transport system. The present study was carried out from samplings in 2006, and it was focused on the spatial 200–0 m zooplankton carbon demand across 24 sampling stations, along the Mediterranean Sea, from the island of Crete to the Strait of Gibraltar. Its potential day/night variability was evaluated. The zooplankton composition, abundance and biomass were investigated. The carbon demand per unit zooplankton biomass indicates geographical and diel differences among the sampling stations. A higher mean carbon demand was seen for the western Mediterranean with respect to the eastern Mediterranean, which can be justified through the observed ratio of gelatinous:crustacean taxa and the water temperatures recorded. Higher carbon demand was measured in samples collected during the dark hours. The relation to the presence and abundance of actively migrating euphausiids and copepods was discussed. A comparison with data from another of our study carried out in the same study area but in another seasonal period was done.

Disentangling the counteracting effects of water content and carbon mass on zooplankton growth

Abstract Zooplankton vary widely in carbon percentage (carbon mass as a percentage of wet mass), but are often described as either gelatinous or non-gelatinous. Here we update datasets of carbon percentage and growth rate to investigate whether carbon percentage is a continuous trait, and whether its inclusion improves zooplankton growth models. We found that carbon percentage is continuous, but that species are not distributed homogenously along this axis. To assess variability of this trait in situ, we investigated the distribution of biomass across the range of carbon percentage for a zooplankton time series at station L4 off Plymouth, UK. This showed separate biomass peaks for gelatinous and crustacean taxa, however, carbon percentage varied 8-fold within the gelatinous group. Species with high carbon mass had lower carbon percentage, allowing separation of the counteracting effects of these two variables on growth rate. Specific growth rates, g (d−1) were negatively related to carbon percentage and carbon mass, even in the gelatinous taxa alone, suggesting that the trend is not driven by a categorical difference between these groups. The addition of carbon percentage doubled the explanatory power of growth models based on mass alone, demonstrating the benefits of considering carbon percentage as a continuous trait.

Benthic taxa as potential indicators of a deep-sea oil spill

The effect of the Deepwater Horizon oil spill on benthic macrofauna in the deep-sea Gulf of Mexico was measured in September–October 2010. Macrofauna community diversity and abundance were lowest closest to the wellhead and increased with distance from the wellhead up to 10km. The macrofauna loss was primarily in surface sediments, which could be due to the deposition of oil and other toxic chemicals. Crustacean taxa appeared to be sensitive to the deep-sea blowout. Polychaete taxa varied in their sensitivity, but Dorvilleidae which is often associated with organic enrichment, was responsible for the largest amount of dissimilarity between stations close and far from the wellhead. Several other taxa were classified as sensitive or tolerant to the deep-sea blowout by comparing their distributions among impacted and non-impacted zones. The macrobenthic communities in the deep Gulf of Mexico exhibit a toxic response to the blowout on the Deepwater Horizon well, and this is correlated with barium and petroleum hydrocarbons.

Arthropod diversity associated with the non-indigenous macroalgae Asparagopsis armata Harvey, along the Atlantic coast of the Iberian Peninsula

Arthropod diversity associated with the non-indigenous macroalgae Asparagopsis armata Harvey, along the Atlantic coast of the Iberian Peninsula

Identification and characterization of five polymorphic microsatellite loci in the freshwater copepod Hemidiaptomus gurneyi (Copepoda: Calanoida: Diaptomidae)

Hemidiaptomus diaptomid copepods are known to be excellent biological indicators for the highly biodiverse crustacean communities inhabiting Mediterranean temporary ponds (MTPs), an endangered inland water habitat whose conservation is considered a priority according to the “Habitat Directive” of the European Union. This study reports on the characterization of five polymorphic microsatellite loci in Hemidiaptomus gurneyi, to be used as markers for fine-scale studies on the population genetic structure and metapopulation dynamics of a typical and obligate MTP dweller. The five selected loci proved to be polymorphic in the species, with three to five polymorphic loci per studied population. Overall, mean heterozygosity scored for all loci and populations was lower than that reported for the few other diaptomid species for which microsatellite loci have been to date described; this is possibly due to the intrinsically fragmented and isolated peculiar habitat inhabited by the species. Furthermore, the presence of indels within the flanking regions of selected loci was scored. This study, albeit confirming the technical difficulties in finding proper microsatellite markers in copepods, provides for the first time a set of useful polymorphic microsatellite loci for a Hemidiaptomus species, thus allowing the realization of fine-scale phylogeographic and population genetics studies of this flagship crustacean taxon for MTPs.

Naupliar and Metanaupliar Development of Thysanoessa raschii (Malacostraca, Euphausiacea) from Godthåbsfjord, Greenland, with a Reinstatement of the Ancestral Status of the Free-Living Nauplius in Malacostracan Evolution.

The presence of a characteristic crustacean larval type, the nauplius, in many crustacean taxa has often been considered one of the few uniting characters of the Crustacea. Within Malacostraca, the largest crustacean group, nauplii are only present in two taxa, Euphauciacea (krill) and Decapoda Dendrobranchiata. The presence of nauplii in these two taxa has traditionally been considered a retained primitive characteristic, but free-living nauplii have also been suggested to have reappeared a couple of times from direct developing ancestors during malacostracan evolution. Based on a re-study of Thysanoessa raschii (Euphausiacea) using preserved material collected in Greenland, we readdress this important controversy in crustacean evolution, and, in the process, redescribe the naupliar and metanaupliar development of T. raschii. In contrast to most previous studies of euphausiid development, we recognize three (not two) naupliar (= ortho-naupliar) stages (N1-N3) followed by a metanauplius (MN). While there are many morphological changes between nauplius 1 and 2 (e.g., appearance of long caudal setae), the changes between nauplius 2 and 3 are few but distinct. They involve the size of some caudal spines (largest in N3) and the setation of the antennal endopod (an extra seta in N3). A wider comparison between free-living nauplii of both Malacostraca and non-Malacostraca revealed similarities between nauplii in many taxa both at the general level (e.g., the gradual development and number of appendages) and at the more detailed level (e.g., unclear segmentation of naupliar appendages, caudal setation, presence of frontal filaments). We recognize these similarities as homologies and therefore suggest that free-living nauplii were part of the ancestral malacostracan type of development. The derived morphology (e.g., lack of feeding structures, no fully formed gut, high content of yolk) of both euphausiid and dendrobranchiate nauplii is evidently related to their non-feeding (lecithotrophic) status.

Identification and characterisation of hemocyanin of the fish louse Argulus (Crustacea: Branchiura).

Hemocyanin transports oxygen in the hemolymph of many arthropod species. Within the crustaceans, this copper-containing protein was thought to be restricted to Malacostraca, while other crustacean classes were assumed to employ hemoglobin or lack any respiratory protein. Only recently it has become evident that hemocyanins also occur in Remipedia and Ostracoda. Here we report for the first time the identification and characterisation of hemocyanin in the fish louse Argulus, which belongs to the class of Branchiura. This finding indicates that hemocyanin was the principal oxygen carrier in the stem lineage of the pancrustaceans, but has been lost independently multiple times in crustacean taxa. We obtained the full-length cDNA sequences of two hemocyanin subunits of Argulus foliaceus by a combination of RT-PCR, RACE and Illumina sequencing of the transcriptome. In addition, one full-length and one partial cDNA sequence were derived from the transcriptome data of Argulus siamensis. Western blot analysis confirmed the presence of at least two hemocyanin subunits in A. foliaceus, which are expressed at the mRNA level at a 1:3.5 ratio. The addition to the branchiuran hemocyanin subunits to a multiple sequence alignment of arthropod, hemocyanins improved the phylogenetic resolution within the pancrustacean hemocyanins. Malacostracan, ostracod and branchiuran hemocyanins are distinct from the hexapod and remipede hemocyanins, reinforcing the hypothesis of a close relationship of Remipedia and Hexapoda. Notably, the ostracod hemocyanins are paraphyletic with respect to the branchiuran hemocyanins, indicating ancient divergence and differential loss of distinct subunit types.

Refining the invertivore: diversity and specialisation in fish predation on coral reef crustaceans

Crustaceans are one of the most influential groups in aquatic trophic networks by providing a major connection between primary production and higher consumers. Although coral reefs support a high diversity and abundance of crustaceans and crustacean predators, their trophic interrelationships remain unclear. Using predator gut content analyses, we investigated trophic relationships between Crustacea and adult fishes of the family Labridae, which are one of the most abundant and diverse families of marine crustacean predators. Crustaceans were present within the guts of 93 % of the 30 wrasse genera investigated. We found a distinct division between micro- and macro-crustacean predators: wrasses 90 mm SL displayed a predominantly macro-Crustacea diet. Notably, micro-crustacean predators tended to specialise on certain crustacean taxa, whereas macro-crustacean predators consumed mostly brachyurans. Our findings highlight complex patterns of feeding diversity within crustacean predators that prompt a more nuanced approach to defining the role of crustacean-feeding fishes in coral reef trophodynamics.

Beautiful, but also potentially invasive

Abstract Introduction of non-indigenous exotic species to new areas, where they may establish viable populations and become invasive, is a considerable problem in the protection of nature worldwide, as these species may alter the indigenous species population structure and potentially even decrease the biodiversity. The European fauna underwent through major negative changes on the continent and nowadays, it experiences another new treat, represented by the expanding aquarium pet trade, and with it, associated species (and disease) introductions. Exotic freshwater crustaceans are one of the taxa widely incorporated in the business, counting a remarkable number of species. Recent records of the exotic marbled crayfish or Marmorkrebs (Procambarus fallax f. virginalis) in German in open ecosystems in Slovakia pointed to human-mediated introductions associated with aquarium pet trade in the country. In this regard, a study of the aquarium pet trade both in expositions and shops and online was assessed. Several crustacean taxa are available both in pet trade exhibitions and online through the Internet. Altogether 26 different species were identified in the aquarium trade in Slovakia. These are Procambarus fallax f. virginalis, P. clarkii, P. alleni, Cherax quadricarinatus, C. destructor, C. holthuisi, C. peknyi, Cambarellus patzcuarensis and C. diminutus occurring in the aquarium pet trade in Slovakia (n = 9). Procambarus fallax f. virginalis, P. clarkii and C. patzuarensis are the most common in this regard. There is also a quantity of other related taxa in the aquarium pet trade in Slovakia, mainly Caridina spp. (n = 5), Neocaridina spp. (n = 4), Atyopsis moluccensis, Atya gabonensis, Arachnochium kulsiense and several taxa of exotic crabs (n = 5) belonging to three different genera (Cardiosoma, Geosesarma and Gecarinus) present. Neocaridina davidi is identified as the most frequent in this regard. As some of the species can become established and form viable populations in natural ecosystems in Europe, we alert the public to handle the animals responsibly and thus maintain and protect indigenous European fauna.

The ventral nerve cord in cephalocarida (Crustacea): New insights into the ground pattern of tetraconata

ABSTRACTCover illustration. The horseshoe shrimp Hutchinsoniella macracantha belongs to the ancient crustacean taxon of Cephalocarida. Its external morphology and neuroanatomy exhibit several plesiomorphic structures and patterns dating back to the ancestor of all Tetraconata. In this issue of the Journal of Morphology, Stegner and coauthors (pp. 269–294) studied the ventral nerve cord of adult Hutchinsoniella macracantha in detail, combining immunolabeling (tubulin, serotonin, RFamide, histamine) and nuclear stains with confocal laser microscopy, complemented by 3D‐reconstructions based on serial semithin sections. The cover image shows lateral 3D‐overviews of the cuticle (white in top row, semitransparent in second row), the gut (green, third row), and the ventral nerve cord (neurites and neuropil in yellow, somata in dark grey, bottom row). Different from most other crustaceans, also the limb‐less abdomen in Cephalocarida comprises segmental ganglia.

Mesozooplankton carbon requirement in the southern Adriatic Sea: vertical distribution, diel and seasonal variability, relation to particle flux

Mesozooplankton plays a role in particulate organic carbon (POC) remineralisation from the pelagic sinking POC flux down the water column. The vertical distribution (to 1000 m depth), diel variability (during a 24 h cycle) and seasonal differences of the mesozooplankton carbon requirement (µg C g �1 d �1 ), estimated by measuring the activity of the electron transport system, were investigated at a fixed station in the southern Adriatic Sea during November 2006 and April 2007. To estimate the quantitative role of zooplankton in the carbon loss that occurs during organic particle sinking, the zooplankton carbon requirement was compared with organic carbon vertical fluxes measured using a sediment trap. Zooplankton abundance, biomass and community composition were investigated along with the diel vertical distribution of euphausiid migrating groups and the relative importance of crustaceans and gelatinous taxa to the potential community carbon requirement. Day/night zooplankton carbon requirement differences in the upper 100 m were shown in both sampling periods. They were not at all correlated to the vertical distribution pattern of euphausiids but were attributable to the amount of non-living specimens and/or the ratio between gelatinous and crustacean taxa. The mean metabolic requirement in the sampled layers of the water column was lower in November than in April, ranging from 0.02 to 9.10% and from 0.07 to 31.86%, respectively, of the measured carbon losses. In the epi- and meso- pelagic zones, the total percent contributions of mesozooplankton respiration to organic carbon losses were 0.18 and 18.45%, respectively, in November and 1.41 and 87.27%, respectively, in April. The higher remineralisation percentages detected in April compared to November could be linked to seasonal differences that involve higher primary production, zooplankton biomass, ver- tical amount of sinking POC flux and more intense heterotrophic metabolism, which take place mainly in the meso pelagic layer in each period.

Evolution of crabs – history and deconstruction of a prime example of convergence

Compared with the elongate bodies of shrimps or lobsters, crabs are characterised by a compact body organisation with a depressed, short carapace and a ventrally folded pleon. The evolutionary transformation from a lobster-like crustacean towards a crab is called ‘carcinization’ and has been interpreted as a dramatic morphological change. Nevertheless, the crab-shape evolved convergently in a number of lineages within Decapoda. Accordingly, numerous hypotheses about internal and external factors have been presented, which all try to explain these frequent convergent carcinization events despite the seemingly fundamental changes in the body organisation. However, what a crab is lies greatly in the eye of the beholder and most of the hypotheses about the lobster/crab transformation are biased by untested assumptions. Furthermore, there are two meanings of the word ‘crab’ within decapods: one, the phylogenetic meaning, refers to the clade Brachyura; the other, more general and typological use of the word crab, describes decapods with a certain body shape. These two meanings should not be confused when the issue of carcinization is discussed. Here, I propose a definition of what a crab is, i.e. what is meant when we speak about carcinization. I show that not all Brachyura are crabs in the typological sense. Carcinization occurred at least twice within the clade. Among Anomala there is further evidence that crab-shaped Lithodidae derived from a hermit-crab like ancestor. Carcinization is not restricted to Anomala plus Brachyura (Meiura) but is also found in Achelata, namely in slipper lobsters. A deconstruction of the crab-shape reveals that parts of it appear in various combinations among all decapod groups. Only a certain threshold of number and quality of crab-features makes us call an animal a ‘crab’. This reveals that carcinization does not involve such dramatic changes in morphology as has been suggested. Moreover similar alterations of body shapes appear frequently in other crustacean taxa and in various animal groups as diverse as sharks and sea urchins. Hence morphological constraints, macroevolution, trends, tendencies, or underlying synapomorphies of any kind are not necessary assumptions for the explanation of the evolution of crabs.

Crustacean biodiversity as an important factor for mosquito larval control

Newly established ponds, which are highly dynamic systems with changing levels of biological interactions among species, are common larval mosquito habitats. We investigated the impact of crustacean abundance and taxa diversity on mosquito oviposition and larval development. The effects of the biological larvicide Bacillus thuringiensis israelensis (Bti) on mosquito larvae were monitored according to fluctuations in crustacean communities. Populations of the mosquito Culex pipiens colonized artificial ponds that contained crustacean communities at different time points of colonization by crustaceans: 1) 'no colonization' (no crustaceans), 2) 'simultaneous colonization' by crustaceans and mosquitoes, and 3) 'head-start colonization' by crustaceans (preceding colonization by mosquitoes). All types of ponds were treated with three concentrations of Bti (10, 100, or 1,000 µg/liter). Colonization of all ponds by Cx. pipiens (in terms of oviposition, larval abundance, and larval development) decreased significantly with increasing diversity of crustacean taxa. The total abundance of crustaceans had a minor effect on colonization by Cx. pipiens. The presence of crustaceans increased the sensitivity of Cx. pipiens larvae to Bti treatment by a factor of 10 and delayed the time of recolonization. This effect of Bti was relevant in the short term. In the long term, the presence of Cx. pipiens was determined by crustacean biodiversity.