A review of Palaemonella (Decapoda: Caridea: Palaemonidae), with clarification of the taxonomic status of Cuapetes americanus, Eupontonia and Vir.

The pantropical genus Palaemonella Dana, 1852 (Caridea: Palaemonidae) currently includes 27 species of free-living and symbiotic marine shrimps. The monophyly of Palaemonella with respect to several closely related genera, however, has been questioned by recent analyses. We tested the monophyly of Palaemonella based on multigene phylogenetic analysis and the genus was revealed to be a paraphyletic assemblage by inclusion of species of the genera Eupontonia Bruce, 1971 and Vir Holthuis, 1952, and two genetic lineages of the western Atlantic Cuapetes americanus (Kingsley, 1878). We recognise one of the latter lineages as the previously described Periclimenes rhizophorae Lebour, 1949. Eupontonia and Vir are synonymised with Palaemonella . We also transfer Cuapetes americanus and Periclimenes rhizophorae to Palaemonella . Species previously assigned to Vir were revised; V. colemani Bruce, 2003, V. orientalis (Dana, 1852), V. philippinensis Bruce & Svoboda, 1984 and V. smiti Fransen & Holthuis, 2007 are regarded as valid species of Palaemonella ; Vir longidactylus Marin, 2008 is synonymised with P. smiti ; and the status of V. euphyllius Marin & Anker, 2005 remains unresolved. Palaemonella is currently regarded as a taxon with variable states of two main diagnostic characters, i.e. the plesiomorphic mandibular palp (fully reduced in P. americana ) and the hepatic tooth (fully reduced in former species of Vir and Eupontonia - evidently due to symbiotic modes of life). ZooBank: urn:lsid:zoobank.org:pub:7EEBC655-7EDE-4E46-BCB2-2A3BA16ED7DD.

Revision of Salmoneus cristatus (Coutière, 1897) and Allied Forms (Decapoda: Caridea: Alpheidae).

Salmoneus cristatus (Coutière, 1897) is one of the first described species in the alpheid genus Jousseaumea Coutière, 1897, a name later invalidated and replaced by Salmoneus Holthuis, 1955. The species was described based on material from Djibouti and was initially characterised by the presence of a pronounced, posteriorly extending carina on the mid-dorsal line of the carapace, a shoulder-like elevation of the orbital hoods, and a red-banded colour pattern. Relying mainly on morphological features, various authors reported S. cristatus from several localities in the Indo-West Pacific, from the Red Sea to southern China and Australia. However, recently collected material attributable to S. cristatus on morphological grounds allowed for the combination of morphological characters, molecular data and colour patterns, demonstrating the existence of at least four species under the name of S. cristatus, including three species that are morphologically similar to, but phylogenetically distant from S. cristatus s. str. Therefore, S. cristatus is redescribed herein based on recent material from Saudi Arabia and Iran, as well as older material from Israel and Madagascar, with designation of a neotype from the Red Sea coast of Saudi Arabia. Three new species, viz. S. paracristatus sp. nov., S. franseni sp. nov., and S. alius sp. nov., are described based on recent material from Papua New Guinea for the former two species, and New Caledonia, Papua New Guinea and the Solomon Islands for the latter species. However, at least two of these new species seem to have wider distributions in the Indo-West Pacific.

Molecular phylogeny and historical biogeography of marine palaemonid shrimps (Palaemonidae: Palaemonella-Cuapetes group).

Palaemonidae is the most speciose shrimp family within the infraorder Caridea, composed predominately of freshwater species and marine symbiotic species. The subject of this study is a clade of mainly free-living marine taxa representing a basally separated lineage from most of the symbiotic marine palaemonid genera. Phylogenetic and biogeographic relationships were explored by analysing sequence data from two mitochondrial and four nuclear markers. Maximum likelihood and Bayesian analyses, based on sequences from 52 species of 11 genera, provided similar tree topologies revealing the genera Palaemonella, Cuapetes and Eupontonia as non-monophyletic groups. Divergence time and S-DIVA analyses reveals that the focal clade originated during the Late Cretaceous in the Paleotethys region respective to the present Indo-West Pacific area, a minor part of which spread out to the eastern Pacific during the Paleocene, followed by further migration into the Atlantic (before the closure of the Panama Isthmus). The ancestral state reconstruction of host associations revealed eight independent symbiotic lineages originating from free-living ancestors, entering primary symbioses. The first associations with Cnidaria are estimated to have evolved in the Eocene. This study points to the need of taxonomic revisions of the non-monophyletic genera concerned.

Madangella koumacensis, a new species of palaemonid shrimps (Decapoda: Palaemonidae) from New Caledonia.

A second species of the recently established genus Madangella Frolová Duris is described from New Caledonia. Although the single available specimen lacks both second pereiopods, the new species distinctly differs from the only other representative of the genus, M. altirostris Frolová Duris, 2018 from Papua New Guinea, and can be easily distinguished from the latter by the more elongate and distally tapering rostrum, two subterminal ventral rostral teeth, the carpus of the first pereiopod being subequal to the merus length, and the sixth pleomere being short and stout, distinctly less than 2 times longer than deep. The examined specimen was confirmed as representative of a species separate from M. altirostris also by molecular comparisons of the 16S rRNA and COI mtDNA gene markers. The genus Madangella thus currently consists of two southwestern Pacific species.

A new species and a new record of alpheid shrimps of the genus Salmoneus Holthuis, 1955 (Crustacea: Decapoda: Alpheidae) from Iran.

Extensive samplings of benthic fauna along the Iranian coastlines of the Persian Gulf and Gulf of Oman during 2018-2019 resulted in a small series of shrimps of the alpheid genus Salmoneus. Based on a thorough examination of this material, as well as previously collected specimens, one new species, S. rashedi n. sp., is described, whilst a significant range extension of S. chadwickae Duris Horká, 2016 is reported. Salmoneus rashedi n. sp. is a member of S. gracilipes species group. The present new species differs from other species of the group by a longer rostrum with a short dorsal crest and a single ventral rostral tooth; the species occurs in two colour forms from yellow to reddish orange with some transverse red bands.

Comparative morphology of crayfish mandibles, with insight into their evolution.

Mandibles of representatives of the Holarctic crayfish families Astacidae, Cambaridae, and Cambaroididae were examined using SEM, and the results were analyzed in a phylogenetic framework. The intraspecific variability of the incisor process was found to be higher than its interspecific variability, mainly due to extensive abrasion of its ridge during intermolt periods. The plesiomorphic state of the crayfish mandibles highlights the dentate-crenate type of the incisor process and the extensive ribbed molar field with a multicuspidate caudal part, typical of the two parastacid crayfish examined for comparison. For Holarctic crayfish, the initial evolutionary type of the incisor is also the dentate-crenate one, but the molar field has a bowl-shaped caudal part and reduced cephalic part, both of which have been shown, for example, for Cambaroides. Similar mandibles are also widely present in American cambarids, which further evolved a blade-like incisor process (some Faxonius spp.) or a tricuspidate or double-bladed caudal molar field (some Procambarus spp.). The molar field in Astacidae crayfish is subdivided and rugose. The results of the present study indicate that little phylogenetic information is conveyed by the mandible shape at the species or genus level. Evolutionary changes are indicated mainly on the level of the main crayfish families. RESEARCH HIGHLIGHTS: Mandible shape can be an additional characteristic to distinguish crayfish families and selected genera. Obvious differences exist in the molar process rather than in the incisor ridge.

Cinetorhynchus gabonensis, a new species of hinge-beak shrimp (Crustacea: Decapoda: Rhynchocinetidae) from the eastern Atlantic.

A new species of the rhynchocinetid genus Cinetorhynchus, C. gabonensis sp. n. from the Atlantic waters of Gabon, is described based on morphological and molecular comparisons and its distinctive colour pattern. This is the second known species of the genus in the eastern Atlantic, and the third species in the Atlantic as the whole. The new species is more closely related to the western Atlantic C. manningi, both having quadrispinose ambulatory dactyli (i.e. with unguis + 3 ventral spinules), but differs from the latter by the presence of an arthrobranch on the three anterior pereiopods (vs only on the first pereiopod in C. manningi). The branchial formula of the new species is consistent with most of the Indo-West Pacific congeners, and with the amphi-Atlantic C. rigens; the latter possessing trispinose ambulatory dactyli. Other distinctions of the new species from its congeners are in the carpal and meral spinulation of the ambulatory legs, and in the posterolateral and posteroventral armament of pleomeres IV and V. Cinetorhynchus gabonensis sp. n. differs from both known Atlantic congeners also by a specific colour pattern which is dense deep-red mottled with a pair of small white spots delineated by deep-red broad rings on the top of the third pleomere.

Xiphonectes aculeatus sp. nov., a new swimming crab (Crustacea: Decapoda: Portunidae) from Madagascar.

Here we describe a new species of Xiphonectes A. Milne-Edwards, 1873 (Brachyura: Portunidae) from southern Madagascar. Xiphonectes aculeatus sp. nov. is morphologically most similar to X. latibrachium (Rathbun, 1906) from Hawaii, and X. paralatibrachium Crosnier, 2002, from the Marquesas Islands, French Polynesia. All three species have a carapace with six anterolateral teeth, a long spine on the inner dorsal margin of the cheliped carpus, and a produced, flattened, anterior region on the third maxilliped merus. Among these species, Xiphonectes aculeatus sp. nov. is easily distinguished by the acutely produced posterodistal angle on the meri of its swimming legs, dorsal and marginal structures on its carapace, and most notably, the shape of its frontal teeth.

Madangella altirostris, a new genus and species of palaemonid shrimps (Crustacea: Decapoda: Palaemonidae) from Papua New Guinea.

A single ovigerous female specimen of marine shrimp of the family Palaemonidae collected from Madang Province, N.E. Papua New Guinea, was recognized as a representative of a new genus and species. Due to the presence of a sternal thoracic process, 3 pairs of posterior telson cuspidate setae, and the simple ambulatory dactyli, as well as the lack of branchiae on the two posterior maxillipeds, the new species clearly belongs to the assemblage of primarily free-living palaemonid taxa surrounding the speciose genera Cuapetes and Palaemonella. As the specimen possesses a short leaf-like rostrum, slender second pereiopods with small chelae similar to and not noticeably longer than the first pereiopods and very slender simple ambulatory dactyli, the specimen is without parallel within this assemblage and clearly represents a new genus. Its position within the Cuapetes/Palaemonella lineage of genera is also confirmed by a molecular comparison. The specimen is described and illustrated as a new genus and species.

Kaviengella jeffkinchi, a new genus and species of symbiotic shrimp (Crustacea: Decapoda: Palaemonidae) from Papua New Guinea.

A very small adult specimen of symbiotic palaemonid shrimp collected from Kavieng Lagoon, N.W. New Ireland Island, Papua New Guinea, is described as a new genus and species. Due to the slender subcylindrical body, reduced rostrum, elongated eyes and distolaterally produced uropodal exopods, the new species is somewhat similar to shrimps of the endosymbiotic sponge genus Nippontonia. Both second pereiopods are lost, but the specimen is unique by its bidentate scaphocerites, an apical corona of spiniform teeth on the mandibular molar process, five posterior telson cuspidate setae from which the median and intermediate ones are long, hooked, and the broadly spoon-like dactyli of the first pereiopods chelae with marginal pectination. Based on those characters, the new genus is without parallel among all symbiotic palaemonid shrimps. Its close phylogenetic relationship to the spongobiotic genera Nippontonia, Onycocaridella, and Thaumastocaris, is also confirmed by molecular comparison.

Madeirasquilla tuerkayi, a new genus and species of mantis shrimps from Madeira Island, eastern Atlantic (Crustacea: Stomatopoda: Nannosquillidae).

Madeirasquilla tuerkayi is described as a new genus and species of the nannosquillid mantis shrimps (Stomatopoda) based on a single specimen collected from Madeira, eastern Atlantic. That specimen is remarkable by a combination of the following morphological characters: rostral plate with three sharp anterior projections; antennal protopod with two mesial and one ventral papillae; cornea subglobular; raptorial claw dactylus with 11 or 12 teeth, and with acute proximal tooth on outer margin; pleonite 6 with strong posterolateral spine and two posteriorly directed sternal spines; telson bearing smooth shield-like dorsal prominence with acute median spine posteriorly; four pairs of fixed primary teeth posteriorly on the telson; outer primary spine of uropodal protopod longer than inner primary spine. The separate position of the new genus is supported also by molecular comparison. A key to the genera of the family Nannosquillidae is proposed.

Monomia lucida sp. nov., a new swimming crab (Crustacea: Decapoda: Portunidae) from the South China Sea.

A new species of the portunid genus, Monomia Gistel, 1848, is described from the South China Sea in Vietnam. Monomia lucida sp. nov. is morphologically most similar to M. argentata (A. Milne-Edwards, 1861), which was originally described from Sarawak, on the island of Borneo. In addition to the stout, forward-directed anterolateral teeth of the carapace, the subrectangular sixth segment of the male pleon, and the long and slender laterally bent first gonopods, adults of the new species reach a greater size, and can also be distinguished from M. argentata by the colour pattern on the natatory dactylus. The independent specific status of M. lucida sp. nov. is also supported by molecular evidence. Aside from a comparison of this new species with other known congeners, new photographs of the holotype of M. samoensis (Ward, 1939) are also provided.

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.

Periclimenoides tyrannodentatus, a new species of symbiotic shrimps (Crustacea: Decapoda: Palaemonidae) from Taiwan.

A new species of sponge-endosymbiotic shrimps, Periclimenoides tyrannodentatus, is described and illustrated. The species is remarkable for its stout subspatulate first pereiopods chelae with lateral fan-shaped pectination on their dactyli. Due to this character and simple ambulatory dactyli, the new species is similar to the type species of the genus, P. odontodactylus. Another remarkable character is in the unique shape of the minor chela of the second pereiopods; the distal cutting edges of its compressed fingers are distinctly expanded and armed with quite impressive dentitions. An identification key to the three currently recognised species of the genus Periclimenoides is provided. The new species represents the first record of the genus Periclimenoides from Taiwan.

Towards a revision of the genus Periclimenes: resurrection of Ancylocaris Schenkel, 1902, and designation of three new genera (Crustacea, Decapoda, Palaemonidae).

Based on recently published molecular phylogenies of Indo-West Pacific palaemonid shrimps and further morphological evidence, the systematic position of several species of the polyphyletic genus Periclimenes is revised. The generic name Ancylocaris Schenkel, 1902 is re-established for the anemone-associated Periclimenes brevicarpalis. Actinimenesgen. n., is proposed for the anemone-associated Periclimenes inornatus, Periclimenes ornatellus and Periclimenes ornatus, all of which have a subspatulate first pereiopod. Cristimenesgen. n., is designated for the echinoderm-associated species, Periclimenes commensalis, Periclimenes cristimanus, and Periclimenes zanzibaricus, all with a unique carpo-propodal articulation of the second pereiopods. Rapimenesgen. n. is established for the hydroid and antipatharian-associated Periclimenes brucei, Periclimenes granulimanus, and Periclimenes laevimanus, for which the long, slender and unequal second pereiopods and prehensile ambulatory propodi are the main synapomorphic characters.

The 'scorpion shrimp', a new species of the genus Metapontonia (Crustacea: Decapoda: Palaemonidae) from Taiwan, with new generic record from Papua New Guinea.

A new species of shrimp Metapontonia scorpio symbiotic with scleractinian coral Diploastrea heliopora is described from Taiwan. The species belongs to the smallest symbiotic shrimps of the family Palaemonidae. It is remarkable by a unique ability to turn its last two pleonites with tail fan dorsally over the 4th and preceding pleonal segments, thus resembling scorpions. For such movement, the respective opposing dorsal margins of the 4th-6th segments are deeply concave. The new species is characterized by a short dorsally directed rostrum, incomplete orbit, semicircular scaphocerite, and medially concave basal antennular segment. The only species of the genus, M. fungiacola, is compared with the new species based on morphology and DNA. Metapontonia fungiacola is for the first time reported from Taiwan and Papua New Guinea. The morphological and colour variability of the species is discussed. The scleractinian corals Platygyra lamellina (Merulinidae), Lobophyllia hemprichii, cf. Micromusa sp., Symphyllia cf. radians (Lobophylliidae), and Galaxea sp. (Oculinidae), are new host records for the species.

Multiple host switching events shape the evolution of symbiotic palaemonid shrimps (Crustacea: Decapoda).

The majority of the almost 1,000 species of Palaemonidae, the most speciose family of caridean shrimp, largely live in symbioses with marine invertebrates of different phyla. These associations range from weak epibiosis to obligatory endosymbiosis and from restricted commensalism to semi-parasitism, with the specialisation to particular hosts likely playing a role in the diversification of this shrimp group. Our study elucidates the evolutionary history of symbiotic palaemonids based on a phylogenetic analysis of 87 species belonging to 43 genera from the Indo-West Pacific and the Atlantic using two nuclear and two mitochondrial markers. A complementary three-marker analysis including taxa from GenBank raises this number to 107 species from 48 genera. Seven larger clades were recovered in the molecular phylogeny; the basal-most one includes mostly free-living shrimp, albeit with a few symbiotic species. Ancestral state reconstruction revealed that free-living forms likely colonised cnidarian hosts initially, and switching between different host phyla occurred multiple times in palaemonid evolutionary history. In some cases this was likely facilitated by the availability of analogous microhabitats in unrelated but morphologically similar host groups. Host switching and adaptations to newly colonised host groups must have played an important role in the evolution of this diverse shrimp group.

Monomia calla, a new species of swimming crab (Decapoda, Portunidae) from Madagascar and the Philippines.

A new species of portunid crab (Brachyura: Portunidae) from southern Madagascar and central Philippines is described. Monomia calla sp. nov. is most similar in morphology to M. lecromi (Moosa, 1996) from the Chesterfield Islands in the southwestern Pacific Ocean, and M. rubromarginata (Lanchester, 1900) from the South China Sea, Singapore, Malay Archipelago and the northern half of Australia. The new species can be easily distinguished from all congeners by the distinctive morphology of the male first gonopod. The number of species of the Indo-West Pacific genus Monomia now stands at 12.

A new species of shrimp of the genus Anachlorocurtis Hayashi, 1975 from the Red Sea, with range extension of A. commensalis Hayashi, 1975 (Crustacea, Decapoda, Pandalidae).

A new species of pandalid shrimp Anachlorocurtis occidentalis sp. n., associated with antipatharian corals, is described and illustrated from the north-eastern Red Sea. This new species is closely related to Anachlorocurtis commensalis Hayashi, 1975, the only other species in the genus, and can be distinguished by the more slender body and appendages; the carapace with 3 large, and one small, subtriangular lobes in the middorsal line; a flattened dorsal outline of the third abdominal segment; the sixth abdominal segment twice as long as fifth one; propodi of the ambulatory pereiopods bearing only a single posterior spinule; and harbouring 3-5 pairs of dorsolateral spines on the telson. A revised generic diagnosis is provided here to accommodate the present new species. The genetic divergence of mitochondrial gene cytochrome c oxidase subunit I (COI) between Anachlorocurtis occidentalis sp. n., and A. commensalis is 15.2-15.4%. Molecular analysis also confirmed a sister position of the genus Anachlorocurtis to Miropandalus. The present records of A. commensalis from Taiwan constitute an extension of the known range of the species.

Athanas manticolus sp. nov., a new stomatopod-associated alpheid shrimp from Vietnam (Crustacea, Decapoda).

A new species of the alpheid shrimp genus Athanas Leach, 1814 is described based on a single specimen, an ovigerous female from Nha Trang Bay, Vietnam. Athanas manticolus sp. nov. differs from all other species of Athanas by the presence of a small post-rostral tubercle, combined with a minutely toothed rostrum, reduced extra-corneal teeth, and the absence of infra-corneal and supra-corneal teeth. In addition, the new species is characterised by its unique colour pattern, particularly by the red chromatophores disposed in randomly oriented, short, narrow streaks. As its name suggests, A. manticolus sp. nov. is commensally associated with the burrows of the nannosquillid mantis shrimp Bigelowina phalangium (Fabricius, 1798).