Ecological Transitions and the Shape of the Decapod Tree of Life.

Understanding the processes that shaped the distribution of species richness across the Tree of Life is a central macroevolutionary research agenda. Major ecological innovations, including transitions between habitats, may help to explain the striking asymmetries of diversity that are often observed between sister clades. Here, we test the impact of such transitions on speciation rates across decapod crustaceans, modeling diversification dynamics within a phylogenetic framework. Our results show that, while terrestrial lineages have higher speciation rates than either marine or freshwater lineages, there is no difference between mean speciation rates in marine and freshwater lineages across Decapoda. Partitioning our data by infraorder reveals that those clades with habitat heterogeneity have higher speciation rates in freshwater and terrestrial lineages, with freshwater rates up to 1.5 times faster than marine rates, and terrestrial rates approximately four times faster. This averaging out of marine and freshwater speciation rates results from the varying contributions of different clades to average speciation rates. However, with the exception of Caridea, we find no evidence for any causal relationship between habitat and speciation rate. Our results demonstrate that while statistical generalizations about ecological traits and evolutionary rates are valuable, there are many exceptions. Hence, while freshwater and terrestrial lineages typically speciate faster than their marine relatives, there are many atypically slow freshwater lineages and fast marine lineages across Decapoda. Future work on diversification patterns will benefit from the inclusion of fossil data, as well as additional ecological factors.

First record of the symbiotic palaemonid shrimp Pontonidessibogae Bruce, 2005 (Crustacea, Decapoda, Palaemonidae) from Korea.

Background: A single specimen of Pontonidessibogae was collected from a dendrophylliid coral by trimix SCUBA diving at a depth of 75 m during fieldwork around Jejudo Island, Korea in 2020. The morphology of the specimen corresponds closely to the main diagnostic characters of the holotype, especially in the presence of a distinct tubercle on the eyestalk, as well as the second pereiopod with fusiform setae along the dorsal border of the ischium. New information: The genus Pontonides had previously not been reported from Korean waters. Herein, colour photographs are provided, as well as an illustrated description including previously unreported characteristics.

Distinct suites of pre- and post-adaptations indicate independent evolutionary pathways of snapping claws in the shrimp family Alpheidae (Decapoda: Caridea).

One of the most notable evolutionary innovations of marine invertebrates is the snapping claw of alpheid shrimps (Alpheidae), capable of generating a powerful water jet and a shock wave, used for defense, aggression, excavation, and communication. Evolutionary analysis of this character complex requires the study of a suite of complementary traits to discern pre-adaptations or post-adaptations of snapping behavior. A comprehensive phylogenetic analysis of the Alpheidae based on two mitochondrial and four nuclear markers, covering 107 species from 38 genera (77.6% generic coverage), is presented. Ancestral state reconstruction analyses revealed five independent origins of snapping, two of which relate to the morphologically similar but phylogenetically distant genera Alpheus and Synalpheus, highlighting significant convergence. The evolution of the five complementary traits (adhesive plaques, tooth-cavity system, dactylar joint type, chela size enlargement, and orbital hood) did not always show a significant correlation with the evolution of snapping overall, sometimes only in a few lineages, suggesting different evolutionary pathways were involved and demonstrating the versatility in the evolution of the snapping mechanisms.

Two New Species and a Further Country Record of the Caridean Shrimp Genus Periclimenaeus Borradaile, 1915 from Korea (Decapoda: Palaemonidae).

Two new species of the palaemonid genus Periclimenaeus are described and illustrated from Korea; additionally, a third species is recorded from Korea for the first time. Periclimenaeus karantina sp. nov. was obtained from ascidian hosts. The species has a denticulate dactylus on both second pereiopods, considered to be typical for ascidian associates. It can be separated from related species by the combination of the following characters: the carpocerite overreaching the anterior margin of the scaphocerite; the distolateral tooth of the scaphocerite exceeding the anterior margin of the lamella; the dactylus of the minor chela exceeding the fixed finger; and the ambulatory dactyli furnished with a minute proximal tooth. Periclimenaeus apomonosi sp. nov. was obtained from sponge hosts, and belongs to the P. robustus species-group, on account of the developed anterior median lobe on the tergite of the first abdominal somite. It can be distinguished from related species by the combination of the presence of a supraorbital tooth; the presence of a pointed process on the inferior orbital angle; the distolateral tooth of the scaphocerite terminating level with the anterior margin of the lamella; the antennal carpocerite reaching about 0.6 of the scaphocerite; the first and second chelae with non-serrated cutting edges; the ischium and merus of the second pereiopods harbouring tubercles on the ventral margin; and the ambulatory dactyli with a distal accessory tooth and the corpus furnished with denticles, ventrally. The sponge associated species, Periclimenaeus djboutensis, relatively widespread across the Indo-Pacific, is reported for the first time from Korea in Geomundo Island. Asides from a morphological description of all three species, molecular information of two genetic markers (16S + COI) is provided to aid in future phylogenetic reconstructions of the genus.

Evolution of protective symbiosis in palaemonid shrimps (Decapoda: Caridea) with emphases on host spectrum and morphological adaptations.

Palaemonidae is the most speciose caridean shrimp family, with its huge biodiversity partially generated via symbiosis with various marine invertebrates. Previous studies have provided insights into the evolution of protective symbiosis in this family with evidence for frequent inter-phyla host switches, but the comprehensiveness of evolutionary pathways is hampered by the resolution of the previous phylogenetic trees as well as the taxon coverage. Furthermore, several critical issues related to the evolution of a symbiotic lifestyle, including the change in host spectrum and corresponding morphological adaptations, remain largely unresolved. We therefore performed a much extended phylogenetic comparative study on Palaemonidae, rooted in a comprehensive phylogeny reconstructed by a supermatrix-supertree approach based on a total of three mitochondrial and five nuclear markers. Ancestral state reconstruction of host associations revealed at least three independent evolutions into symbiosis, with potentially a drive to seek protection fuelling incipient symbiosis. Yet, most of the observed symbiotic species diversity was radiated from a single cnidarian associate. The evolution of mandibles and ambulatory dactyli suggests a general lack of correlation with host affiliation (except sponge endosymbionts), implying limited morphological adaptations following host switching, despite being putatively a major adaptive consequence of symbiosis. Our analyses of host spectrum, in terms of basic and taxonomic specificity, revealed no apparent phylogenetic signal but instead resolved a dynamic pattern attributable to frequent host switching. Uncoupling between host spectrum and the degree of morphological specialisation is the norm in palaemonids, suggesting that morphological characters are not fully in tune with host spectrum, in addition to host affiliation. This study demonstrates the complexity in the evolution of symbiosis, pointing to the presence of cryptic adaptations determining host spectrum and governing host switch diversification, and provides a clear direction for the evolutionary study of symbiosis in other marine symbiotic groups involving host switching.

On the genus Mesopontonia Bruce, 1967 (Crustacea: Decapoda: Palaemonidae) in Korea, with the description of a new species.

Mesopontonia verrucimanus and Mesopontonia kimwoni sp. nov. are recorded from high-latitude temperate waters in Munseom Islet, Jejudo Island, Republic of Korea, with both species collected on gorgonians and sponges by trimix diving between 50 and 75 m depth. Mesopontonia kimwoni sp. nov. is morphologically allied to M. brevicarpus, but can be distinguished by the cutting edges of the fingers of the first chela being entire. Significant morphological variation in the rostrum as well as the second pereiopods is documented in M. verrucimanus, although cytochrome c oxidase subunit I (COI) barcode analysis proves this to be infra-specific variation. A key to species of the genus Mesopontonia is provided.

On two species of the alpheid shrimp genus Salmoneus Holthuis, 1955 from Kuwait, one of them new to science (Malacostraca: Decapoda: Caridea).

The alpheid genus Salmoneus Holthuis, 1955 is reported from Kuwait for the first time, with two species. One species, Salmoneus ikaros sp. nov., is described based on a single specimen from Failaka Island, extracted from the burrow of the callianassid ghost-shrimp Balsscallichirus masoomi (Tirmizi, 1970), together with the host. The new species is characterised by its peculiar eyes, which together with other characters separate it from all previously described species of Salmoneus. The second species, Salmoneus gracilipes Miya, 1972, is reported from Kuwait based on three specimens from two different localities and different habitats. Two specimens were found under coral rocks at a depth of about 7 m off Kubbar Island, whereas the third specimen was extracted from the burrow of the echiuran worm, Listriolobus cf. brevirostris Chen Yeh, 1958, at the type locality of S. ikaros sp. nov. at Failaka Island. Material identified as S. gracilipes from across its wide distribution range appears to be morphologically heterogeneous, possibly containing more than one species, and thus will need further studies.

New records of decapod crustaceans from Kuwait (Malacostraca: Decapoda).

Seventeen species of shrimp-like decapod crustaceans (infraorders Caridea, Axiidea and Gebiidea) and two species of porcelain crabs (infraorder Anomura) are recorded for the first time from Kuwait, some of them also representing new records for the Arabian Gulf. The new records from Kuwait are: (1) Alpheus edamensis De Man, 1888; (2) Alpheus edwardsii (Audouin, 1826); (3) Alpheus macrodactylus Ortmann, 1890; (4) Alpheus maindroni Coutière, 1898; (5) Arete indicus Coutière, 1903; (6) Athanas parvus De Man, 1910; (7) Synalpheus gracilirostris De Man, 1910 [all Alpheidae]; (8) Latreutes mucronatus (Stimpson, 1860) [Hippolytidae]; (9) Thor paschalis (Heller, 1862) [Thoridae] (10) Periclimenella pettithouarsii (Audouin, 1826); (11) Anchistus custos (Forskål, 1775); (12) Urocaridella pulchella Yokes Galil, 2006 [all Palaemonidae]; (13) Chlorocurtis jactans (Nobili, 1904) [Chlorotocellidae]; (14) Upogebia carinicauda (Stimpson, 1860); (15) Upogebia octoceras Nobili, 1904 [Upogebiidae]; (16) Balsscallichirus masoomi (Tirmizi, 1970), (17) Michaelcallianassa indica Sakai, 2002 [Callianassidae]; (18) Raphidopus persicus Ng, Safaie Naser, 2012 and Polyonyx obesulus Miers, 1884 [Porcellanidae]. Most of these taxa have been previously recorded from other parts of the Arabian Gulf, mainly from the coasts of Iran and the United Arab Emirates, except for A. maindroni and U. pulchella, which are recorded from the Arabian Gulf for the first time. Most species are shown in colour photographs, some for the first time. In addition, the presence of Synalpheus quinquedens Tattersall, 1921 (Alpheidae), previously known from Kuwait based only on a questionable record in a popular field guide, is confirmed based on a single collected and preserved specimen.

Taxonomic notes on Alpheus inopinatus Holthuis amp; Gottlieb, 1958 and Alpheus cf. lobidens De Haan, 1849 from Kuwait (Malacostraca: Decapoda: Alpheidae).

The status of the common intertidal snapping shrimp, Alpheus inopinatus Holthuis Gottlieb, 1958, is discussed based on newly collected material from Kuwait. Alpheus inopinatus was previously confused with morphologically very similar species in the Alpheus lobidens De Haan, 1849 species complex, formerly identified as A. crassimanus Heller, 1862 and herein tentatively referred to as A. cf. lobidens. The material herein examined strongly supports the validity of A. inopinatus based on several morphological characters, as well as differences in the colour pattern, compared to other members of the A. lobidens complex.

A new species of Alpheus (Crustacea, Decapoda, Alpheidae) from the Arabian Sea, Kerala, India.

A new species of Alpheus, A. samudra nov. sp., is described from the bycatch of trawlers operating between 275-375 m depth on the Quilon Bank (Kerala, India). The new species belongs to the brevirostris group, but can be easily distinguished from all but one species, by the extremely laterally compressed major cheliped. Alpheus samudra nov. sp. is very similar to A. leptocheles Banner Banner, 1975 in the form of the major cheliped, but the proportions of the fingers to the palm and the shape of the fingers easily separate both species.

Documenting decapod biodiversity in the Caribbean from DNA barcodes generated during field training in taxonomy.

DNA barcoding is a useful tool to identify the components of mixed or bulk samples, as well as to determine individuals that lack morphologically diagnostic features. However, the reference database of DNA barcode sequences is particularly sparsely populated for marine invertebrates and for tropical taxa. We used samples collected as part of two field courses, focused on graduate training in taxonomy and systematics, to generate DNA sequences of the barcode fragments of cytochrome c oxidase subunit I (COI) and mitochondrial ribosomal 16S genes for 447 individuals, representing at least 129 morphospecies of decapod crustaceans. COI sequences for 36% (51/140) of the species and 16S sequences for 26% (37/140) of the species were new to GenBank. Automatic Barcode Gap Discovery identified 140 operational taxonomic units (OTUs) which largely coincided with the morphospecies delimitations. Barcode identifications (i.e. matches to identified sequences) were especially useful for OTUs within Synalpheus, a group that is notoriously difficult to identify and rife with cryptic species, a number of which we could not identify to species, based on morphology. Non-concordance between morphospecies and barcode OTUs also occurred in a few cases of suspected cryptic species. As mitochondrial pseudogenes are particularly common in decapods, we investigate the potential for this dataset to include pseudogenes and discuss the utility of these sequences as species identifiers (i.e. barcodes). These results demonstrate that material collected and identified during training activities can provide useful incidental barcode reference samples for under-studied taxa.

Further records of burrow-associated palaemonid shrimps (Decapoda: Palaemonidae).

Despite the ubiquitous nature of symbiosis in palaemonid shrimps (Caridea: Palaemonidae) which live in or on varied invertebrate hosts, such as echinoderms, sponges, ascidians, hard and soft corals, etc., very few taxa have been recorded living in burrows constructed by other animals. This is in sharp contrast to the rich burrow-dwelling diversity in the Alpheidae, in which numerous genera associate with a great variety of burrowing animals, including stomatopods (Hayashi 2002; Duris Anker 2014), echiurans (Anker et al. 2005, 2015), other alpheid shrimps (e.g. De Grave 2004; Anker Marin 2006), and especially numerous ghost and mud shrimps (e.g. Anker, 2011; Anker Lazarus 2015).

Two new species of Hippolyte from the Tropical Central and East Atlantic (Crustacea, Decapoda, Caridea).

Two new species of the caridean shrimp genus Hippolyte Leach, 1814 [in Leach, 1813-14] are described from the Tropical Central and East Atlantic. Hippolyte cedrici sp. nov., from Príncipe and São Tomé, can be distinguished from both the related H. holthuisi Zariquey Álvarez, 1953 and H. varians Leach, 1814 on the basis of rostral dentition, as well as meristics of the ambulatory pereiopods. Hippolyte karenae sp. nov., from St. Helena, is morphologically similar to H. coerulescens (Fabricius, 1775) and H. obliquimanus Dana, 1852, by having a well-developed tooth on the outer angle of the first peduncular article of the antennula. It differs from these species, amongst other characters, primarily in the armature of the ambulatory dactyli. Specimens were collected from hydrozoan, antipatharian and alcyonarian cnidarians.

Systematic analysis of the caridean shrimp superfamily Pandaloidea (Crustacea: Decapoda) based on molecular and morphological evidence.

One of the systematically controversial superfamilies in Caridea is the predominately deep-sea or cold water Pandaloidea, largely because this species-rich group of nearly 200 species in 25 genera exhibits a very high diversity of body forms and ecology. Although the relationships amongst the taxa within Pandaloidea have been repeatedly discussed based on morphology, no comprehensive molecular phylogeny exists. In this study, we present the first molecular phylogeny of the group, based on a combined dataset of two mitochondrial (12S and 16S rRNA) and six nuclear (ATP synthase ß-subunit, enolase, glyceraldehyde-3-phosphate dehydrogenase, histone 3, phosphoenolpyruvate carboxykinase and sodium-potassium ATPase α-subunit) markers, based on 62 species (about 1/3 of known biodiversity) in 22 genera (88% of genera) of two pandaloid families (Pandalidae, Thalassocarididae) and outgroups from seven other caridean families. With generally high support, the relationships within the clade are fully resolved. Pandalidae is shown to be paraphyletic with Thalassocarididae deeply nested within as a monophyletic group, and the latter is herein considered to be a synonym of Pandalidae. Five major clades are recovered, with the shallow water genera Anachlorocurtis, Chlorocurtis, Chlorotocella and Miropandalus forming a sister clade to the remaining genera. At the genus level, the phylogeny indicates Plesionika, Heterocarpus and Pandalus to be not monophyletic. The validity of Pandalopsis, Stylopandalus and Calipandalus is challenged and these genera are considered herein to be junior synonyms of Pandalus (Pandalopsis) and Plesionika (Stylopandalus and Calipandalus). Although not fully resolved, some evidence potentially considers Nothocaris to be a valid genus. Ancestral State Reconstruction successfully recovered 15 synapomorphies for the major clades, with 11 of them reported to be of systematic significance for the first time.

Freshwater transitions and symbioses shaped the evolution and extant diversity of caridean shrimps.

Understanding the processes that shaped the strikingly irregular distribution of species richness across the Tree of Life is a major research agenda. Changes in ecology may go some way to explain the often strongly asymmetrical fates of sister clades, and we test this in the caridean shrimps. First appearing in the Lower Jurassic, there are now ~3500 species worldwide. Carideans experienced several independent transitions to freshwater from marine habitats, while many of the marine species have also evolved a symbiotic lifestyle. Here we use diversification rate analyses to test whether these ecological traits promote or inhibit diversity within a phylogenetic framework. We demonstrate that speciation rates are more than twice as high in freshwater clades, whilst symbiotic ecologies are associated with lower speciation rates. These lower rates amongst symbiotic species are of concern given that symbioses often occur in some of the most diverse, delicately balanced and threatened marine ecosystems.

Multiple origins and strong phenotypic convergence in fish-cleaning palaemonid shrimp lineages.

Several species of palaemonid shrimps are known to act as fish-cleaning symbionts, with cleaning interactions ranging from dedicated (obligate) to facultative. We confirmed five evolutionarily independent origins of fish cleaning symbioses within the family Palaemonidae based on a phylogenetic analysis and the ancestral state reconstruction of 68 species, including 13 fish-cleaners from the genera Ancylomenes, Brachycarpus, Palaemon, Periclimenes, and Urocaridella. We focus in particular on two distantly related lineages of fish cleaning shrimps with allopatric distributions, the Indo-West Pacific Ancylomenes and the western Atlantic monophyletic Ancylomenes/Periclimenes group, which exhibit striking similarities in morphology, colouration and complex behaviour. Specifically, representatives of both lineages are similar in: (1) the general body shape and colour pattern; (2) the utilization of sea anemones as conspicuous cleaning stations; and (3) the use of sideways body swaying to visually promote their bright colour spots in order to attract fish clients. Such morphological, ecological and ethological convergences are apparently due to adaptations to fish cleaning linked to the establishment of similar modes of communication with fish clients in these species.

Global biogeography, cryptic species and systematic issues in the shrimp genus Hippolyte Leach, 1814 (Decapoda: Caridea: Hippolytidae) by multimarker analyses.

Hippolyte is a genus of small bodied marine shrimps, with a global distribution. Here, we studied the phylogenetic and biogeographic relationships amongst the species of this genus with two mitochondrial and two nuclear markers, using Bayesian Inference, Maximum Likelihood, genetic divergence, molecular clock and S-DIVA. In addition, the Indo-West Pacific genus Alcyonohippolyte was included. Based on sequences from 57 specimens of 27 species, we recovered a robust biogeographic scenario that shows the Indo-West Pacific as the probable ancestral area of the genus Hippolyte, which emerged in the Paleocene, followed by dispersal in three general directions: (1) South Pacific, (2) eastern Atlantic and Mediterranean Sea and (3) Americas, the latter with a primary colonization in the eastern Pacific followed by a radiation into the western Atlantic. Our analysis reveals that the species of the H. ventricosa group do not constitute a monophyletic group and Alcyonohippolyte does not constitute a reciprocally monophyletic group to Hippolyte, with both genera herein synonimised. The relationships and systematic status of several transisthmian and Atlantic species are clarified.

Molecular phylogeny of Pasiphaeidae (Crustacea, Decapoda, Caridea) reveals systematic incongruence of the current classification.

Caridean shrimps constitute one of the most diverse groups of decapod crustaceans, notwithstanding their poorly resolved infraordinal relationships. One of the systematically controversial families in Caridea is the predominantly pelagic Pasiphaeidae, comprises 101 species in seven genera. Pasiphaeidae species exhibit high morphological disparity, as well as ecological niche width, inhabiting shallow to very deep waters (>4000m). The present work presents the first molecular phylogeny of the family, based on a combined dataset of six mitochondrial and nuclear gene markers (12S rDNA, 16S rDNA, histone 3, sodium-potassium ATPase α-subunit, enolase and ATP synthase ß-subunit) from 33 species belonged to six genera of Pasiphaeidae with 19 species from 12 other caridean families as outgroup taxa. Maximum likelihood and Bayesian inference analyses conducted on the concatenated dataset of 2265bp suggest the family Pasiphaeidae is not monophyletic, with Psathyrocaris more closely related to other carideans than to the other five pasiphaeid genera included in this analysis. Leptochela occupies a sister position to the remaining genera and is genetically quite distant from them. At the generic level, the analysis supports the monophyly of Pasiphaea, Leptochela and Psathyrocaris, while Eupasiphae is shown to be paraphyletic, closely related to Parapasiphae and Glyphus. The present molecular result strongly implies that certain morphological characters used in the present systematic delineation within Pasiphaeidae may not be synapomorphies and the classification within the family needs to be urgently revised.

Phylogeographic patterning among two codistributed shrimp species (Crustacea: Decapoda: Palaemonidae) reveals high levels of connectivity across biogeographic regions along the South African coast.

We compare the genetic structuring and demographic history of two sympatric caridean shrimp species with distinct life history traits, one amphidromous species Palaemon capensis and one marine/estuarine species Palaemon peringueyi, in the historical biogeographical context of South Africa. A total of 103 specimens of P. capensis collected from 12 localities and 217 specimens of P. peringueyi collected from 24 localities were sequenced for the mitochondrial cytochrome oxidase one (CO1) locus. Results from analyses of molecular variance (AMOVA), pairwise ΦST comparisons and haplotype networks demonstrate weak to moderate genetic differentiation in P. capensis and P. peringueyi respectively. P. peringueyi exhibits partial isolation between populations associated with distinct biogeographic regions, likely driven by the region's oceanography. However, there is minimal evidence for the occurrence of discrete regional evolutionary lineages. This demonstrated lack of genetic differentiation is consistent with a marine, highly dispersive planktonic phase in both the amphidromous P. capensis and the marine/estuarine P. peringueyi. Bayesian skyline plots, mismatch expansions and time since expansion indicate that both species maintained stable populations during the Last Glacial Maximum (LGM), unlike other southern African aquatic species.

Presumed filter-feeding in a deep-sea benthic shrimp (Decapoda, Caridea, Stylodactylidae), with records of the deepest occurrence of carideans.

Using the remotely operated vehicle Deep Discoverer, we observed a large stylodactylid shrimp resting on a sedimented sea floor at 4826 m in the Marianas Trench Marine National Monument. The shrimp was not collected but most closely resembled Bathystylodactylus bathyalis, known previously only from a single broken specimen. Video footage shows the shrimp facing into the current and extending its upraised and fringed first and second pereopods, presumably capturing passing particles. The video footage is the first ever to show a living deep-sea stylodactylid and constitutes the deepest record for the family. We provide a list of the deepest reports of caridean shrimps world-wide.