Ghost Shrimp Research Articles

Observações morfológicas no camarão-fantasma Callichirus seilacheri (Bott, 1955) (Decapoda, Callianassidae)

Callichirus seilacheri (Bott, 1955) é considerado um dos camarões-fantasmas mais comuns em zonas intertidais de praias arenosas, ao longo do Pací­­fico oriental tropical. O presente estudo fornece novas observações sobre a morfologia de C. seilacheri, com base numa revisão de material abundante coletado ao longo da costa do Pací­­fico, na América Central, incluindo espécimes da localidade tipo desta espécie (Playa Los Blancos, El Salvador). As caracterí­­sticas inéditas de C. seilacheri, incluem: carapaça com pequeno rostro triangular, e sem cerdas na extremidade; Pereiópodos 1 muito desiguais em machos adultos, mas não nas fêmeas e juvenis, de ambos os sexos; Primeiro pleópodo sexualmente dimórfico; Fêmeas com gonóporos ovais, cada um na porção ventral da coxa do terceiro par de pereiópodos, e poros genitais extras na porção ventral da coxa do quinto pereiópodo, estes últimos não funcionais (não conectados aos ovários). Aparentemente, a presença de gonóporos extras em fêmeas de C. seilacheri é um caráter vestigial, compartilhado com outros representantes do mesmo gênero.

Examining heat treatment for stabilization of the lipidome.

To confidently determine lipid-based biomarkers, it is important to minimize variation introduced during preanalytical steps. We evaluated reducing variation associated with lipid measurements in invertebrate sentinel species using a state-of-the-art heat treatment technique. Earthworms (Eisenia fetida), house crickets (Acheta domestica) and ghost shrimp (Palaemonetes paludosus) were euthanized either by flash freezing or heat treatment. For both experiments, samples were either immediately extracted after removal from -80°C storage or incubated on ice for one hour prior to sample weighing and extraction. Lipidomics was performed on resulting extracts using liquid chromatography high resolution tandem mass spectrometry. LipidMatch and LipidSearch were used for lipid identification. Lipid enzymatic products (e.g., phosphatidylmethanols, diglycerides, lysoglycerophospholipids and ether-linked/oxidized lysoglycerophospholipids), were in higher concentrations in flash-frozen samples, when compared with heat-treated samples. Results suggest that heat treatment reduces phospholipase A and phospholipase D activity. Heat treatment reduced enzymatic products and increased precursors of these enzymatic products. We believe heat treatment warrants a closer interrogation for improving the robustness of lipid biomarker research, especially in tissue samples, where enzyme stabilizers are difficult to apply, and for use in field studies, where the stabilization of the collected sample is critical.

Dynamics of oogenesis in ghost shrimp Callichirus major (Crustacea: Axiidea): a morphofunctional and histochemical study

Callichirus major, popularly known as ghost shrimp, is a species of great importance in the fishing industry, because of its use as live bait. This study aimed to describe the different stages of the developing ovaries in C. major. Shrimps were collected along the Corujão beach, Piuma, Brazil (20°50'41.6“S 40°44'15.7“W), and the gonads were dissected for histological and histochemical analysis. The ovary consists of two elongated filaments covered by a connective tissue that divides the organ into lobules, where somatic and germ cells are found. It was possible to classify five types of germ cells: Oogonia (Oog), previtellogenic oocyte (Oc1), early vitellogenic oocyte (Oc2), late vitellogenic oocyte (Oc3) and mature oocyte (Oc4) based on their vitellogenic stage, cytoplasmic, nuclear and morphometric characteristics. The histochemical analysis demonstrated an intense reaction for proteins and polysaccharides in peripheral cytoplasm of Oc3 comparing to others cell types. According to size, volume, color intensity and distribution of oocyte types the gonads were classified into: immature, developing, developed and spent, being in females at this last stage, observed empty follicles and oocytes in reabsorption process. During oogenesis was observed a gradual increase in cytoplasmic acidophilia due to accumulation of yolk granules and the intense histochemical reaction in periphery of Oc3, which indicate the beginning of an extravitellogenic source of nutrients. Based on the microscopic analysis of the vitellogenesis, shrimp C. major showed the initial short phase of oocyte growth following with a fast vitellogenic cycle.

N2 production and fixation in deep-tier burrows of Squilla empusa in muddy sediments of Great Peconic Bay

Global marine N budgets often show deficits due to dominance of benthic N2 production relative to pelagic N2 fixation. Recent studies have argued that benthic N2 fixation in shallow water environments has been underestimated. In particular, N2 fixation associated with animal burrows may be significant as indicated by high rates of N2 fixation reported in muddy sands populated by the ghost shrimp, Neotrypaea californiensis (Bertics et al., 2010). We investigated whether N2 fixation occurs at higher rates in the burrow-walls of the deep-burrowing (~0.5–4m) mantis shrimp, Squilla empusa, compared to ambient, estuarine muds and measured seasonal in-situ N2 concentrations in burrow-water relative to bottom-water. Acetylene reduction assays showed lower N2 fixation in burrow-walls than in un-populated sediments, likely due to inhibitory effects of O2 on ethylene production. Dissolved N2 was higher in burrow-water than proximate bottom-water at all seasons, demonstrating a consistent balance of net N2 production relative to fixation in deep-tier biogenic structures.

Family, generic and species synonymies of recently published taxa of ghost shrimps (Decapoda, Axiidea, Eucalliacidae and Ctenochelidae): cautionary tales

Re-examination of the holotype of Calliaxiopsis madagassa Sakai & Türkay, 2014 has led to the conclusion that the genus is a synonym of Calliaxina Ngoc-Ho, 2003 and the species is a senior synonym (by 6 months) of Calliaxina thomassini Ngoc-Ho, 2014, now Calliaxina madagassa (Sakai & Türkay, 2014). Both are from Madagascar. Comparison of the holotype of Tosacallianassa hatasagaensis Sakai, 2016 with several published figures of Ctenocheles balssi Kishinouye, 1926 has similarly found their genera and species synonymous. Further, the family Tosacallianassidae is synonymous with Ctenochelidae Mannning & Felder, 1991. Both species are from the same limited area in Japan. The nephropid species Thaumastochelopsis plantei Burukovsky, 2005 is transferred to Ctenocheles.

Gilvossius chichijimaensis Sakai, 2015 (Crustacea: Decapoda: Axiidea: Callianassidae), a junior subjective synonym of Paratrypaea bouvieri (Nobili, 1904)

Sakai (2015) erected a new callianassid ghost shrimp taxon Gilvossius chichijimaensis diagnosed on the basis of Komai & Tachikawa’s (2008) text and figures of a male specimen originally identified as Paratrypaea bouvieri (Nobili, 1904). A holotype was designated “CBM-ZC 7244, holotype male (cl 7.4 mm), Chichijima Island, Tokyo Prefecture”. This registration number appears to be a mistranscription from Komai & Tachikawa’s (2008) list of specimens which includes “Chichi-jima Island: … CBM-ZC 7422, 2 males (5.2 mm, 7.4 mm), 1 ovigerous female (cl 6.9 mm), Okumura River, rivermouth, tidal flat, 7 August 2002,”. It can be assumed that the second male was selected as the holotype. Although Sakai (2015) did not designate paratypes, he based his comparison of the new species on “the male specimen (CMNH-ZC 2422) identified by Komai & Tachikawa (2008) as Paratrypaea (= Gilvossius) bouvieri”, not the male he selected as holotype. By this he was probably referring to CMNH-ZC 2240.

Population dynamics and secondary production of the ghost shrimp Callichirus major (Thalassinidea): A keystone species of Western Atlantic dissipative beaches

We describe the autoecology of the thalassinid crustacean Callichirus major, a dominant macrofaunal species, on a relatively non-impacted Brazilian dissipative beach. At Rasa Beach (22°45’S, 41°56’W, southwestern Atlantic), monthly sampling was carried out during spring low tides at two sites, 1.3 km apart. Seasonal von Bertalanffy growth curves were adjusted by the ELEFAN routine (FiSAT-II) for the entire population and for each gender separately. Considerable differences in density, biomass, secondary production and size composition of C. major from the two sites indicate that it is not possible to extrapolate our results to the entire beach since there are significant heterogeneities between the two sampling sites. The higher secondary production at one of the sites may be caused by its higher populational density, associated with the occurrence of a higher proportion of juveniles. The renewal rate of the local population of C. major (P/B ratio from 0.85 to 2.19) is smaller than for other beach macrocrustaceans studied in different localities worldwide.

A lithostratigraphic and palaeoenvironmental framework for the late Miocene El Caracolar section (Granada Basin, Betic Cordillera, Spain) and description of decapod crustaceans

The locality of El Caracolar in the Granada Basin (Central Betic Cordillera, southern Spain) has yielded a rich late Miocene assemblages composed of marine invertebrates and vertebrates, accompanied by microfossils, macroflora and trace fossils. Exposed strata consisting of sands, sandy siltstones, silty sandstones, siltstones and calcirudites are divided into four local units. Lithostratigraphically, the studied section is placed between the top of the La Peza Formation and the Quéntar Formation. Based on foraminifers, the age of units 2 and 3 is estimated to be early Tortonian (11.0–9.9 Ma), whereas units 1 and 4 do not yield any reliable biostratigraphic markers. The diverse biotic association suggests that deposition took place in a near-shore outer neritic zone of a narrow to open seaway in a mesotrophic regime, responsible for the establishment of a chemosynthetic community under (sub)tropical conditions. The palaeo-depth of the depositional setting is estimated between 70 and 130 m. We further focused on decapod crustaceans that represent the first formally reported fossil decapod assemblage from the Granada province. The faunule consists of eight genera from two assemblages representing different palaeoenvironments. The assemblage of units 1 and 4 is dominated by the ghost shrimp “Callianassa” cf. almerai and accompanied by the hermit crab Petrochirus, whereas the assemblage from unit 3 includes the ghost shrimp Ctenocheles and the brachyuran crabs Raninoides, Calappa, Goneplax, Styrioplax, and Typilobus. Unit 2 does not yield any identifiable decapod remains. Styrioplax sp. represents the first occurrence of the genus outside the Central Paratethys, substantially expanding its palaeogeographical distribution. The decapod faunule from El Caracolar shows affinities with assemblages from the Proto-Mediterranean and Paratethys. This study provides a lithostratigraphic and palaeoenvironmental framework for further palaeontological studies in this unique Western Mediterranean outcrop.

Decapoda (Crustacea) of the Coon Creek Formation (Maastrichtian) of Mississippi and Tennessee

The Upper Cretaceous (Maastrichtian) Coon Creek Formation of Mississippi and Tennessee possesses a diverse and abundant assemblage of decapods including lobsters, ghost shrimp, and crabs. The formation lies in a temporally and paleogeographically significant location, situated between the Atlantic Coastal Plain and the Western Interior Seaway, shortly before the closing of the seaway and the K-Pg mass extinction. Coon Creek decapods have been little studied since the fauna was first described in the 1920s. A large collection of specimens, ranging in preservation from poor to excellent, has recently become available for study. Analysis of the elemental composition of the sediment and cuticle of six species of decapods from six families (Palinuridae, Nephropidae, Callianassidae, Dakoticancridae, Raninidae, and Retroplumidae) collected at the Blue Springs locality in Mississippi reveals phosphatic replacement of cuticle and trace amounts of iron and sulfur in the surrounding sediment. Concretions bearing decapods and a decapod burrow were observed in thin section and were mapped for elemental distribution using Energy-dispersive X-Ray spectroscopy and dot mapping indicating consistent elemental results with the surrounding sediment. The six species of decapods were analyzed using the same techniques and suggest diagentic affects in cuticlar structure and the presence of silica forming on the cuticle of a single specimen. Taphonomic data supports preservation ranging from well preserved phosphatization to secondary alteration to silica-rich exterior and weathering clay minerals. Because the silica is not replacing the phosphatized exocuticle and microscopic structure of cuticle in cross section is not preserved in the silica layer, the cause of this alteration is uncertain. The systematics and taxonomy of the decapod species from the Coon Creek Formation were reassessed. Sixteen species are identified, including two new species: Hoploparia tennesseensis, Hoploparia mcnairyensis, Linuparus keyesi sp. nov., Linuparus sp., Palaeopetrochirus enigmus, Seorsus wadei, Bournelyreidus ericksoni sp. nov., Cristipluma mississippiensis, Lithophylax flectus new combination, Hoploparia georgeana, Mesostylus mortoni, Tetracarcinus subquadratus, Avitelmessus grapsoideus, Cretacoranina testacea, Dakoticancer australis, Prehepatus harrisi, and ?Latheticocarcinus atlanticus, as well as two fragments belonging to the Majidae. This decapod fauna has species in common with correlative units of the Western Interior Seaway, the Gulf Coastal Plain, and the Atlantic Coastal Plain, supporting the hypothesis that the Mississippi Embayment is an ecotone for North American decapods.

Two new species ofClausidiumcopepods (Crustacea, Poecilostomatoida) associated with ghost shrimps from Iran

Two new species ofClausidiumcopepods were collected on the bodies of ghost shrimps from the Iranian coast of the Gulf of Oman.Clausidium makranensissp. nov. andClausidium sariisp. nov. are described from the large chelipeds ofNeocallichirus natalensisandCorallianassa martensi, respectively.Clausidium makranensissp. nov. is distinguishable from its congeners by the unique anal somite that is armed with sclerotized hooks on each side.Clausidium sariisp. nov. can be differentiated from its congeners by the armature and shape of leg 5.

Digging deeper: new gene order rearrangements and distinct patterns of codons usage in mitochondrial genomes among shrimps from the Axiidea, Gebiidea and Caridea (Crustacea: Decapoda).

BackgroundWhole mitochondrial DNA is being increasingly utilized for comparative genomic and phylogenetic studies at deep and shallow evolutionary levels for a range of taxonomic groups. Although mitogenome sequences are deposited at an increasing rate into public databases, their taxonomic representation is unequal across major taxonomic groups. In the case of decapod crustaceans, several infraorders, including Axiidea (ghost shrimps, sponge shrimps, and mud lobsters) and Caridea (true shrimps) are still under-represented, limiting comprehensive phylogenetic studies that utilize mitogenomic information.MethodsSequence reads from partial genome scans were generated using the Illumina MiSeq platform and mitogenome sequences were assembled from these low coverage reads. In addition to examining phylogenetic relationships within the three infraorders, Axiidea, Gebiidea, and Caridea, we also investigated the diversity and frequency of codon usage bias and mitogenome gene order rearrangements.ResultsWe present new mitogenome sequences for five shrimp species from Australia that includes two ghost shrimps, Callianassa ceramica and Trypaea australiensis, along with three caridean shrimps, Macrobrachium bullatum, Alpheus lobidens, and Caridina cf. nilotica. Strong differences in codon usage were discovered among the three infraorders and significant gene order rearrangements were observed. While the gene order rearrangements are congruent with the inferred phylogenetic relationships and consistent with taxonomic classification, they are unevenly distributed within and among the three infraorders.DiscussionOur findings suggest potential for mitogenome rearrangements to be useful phylogenetic markers for decapod crustaceans and at the same time raise important questions concerning the drivers of mitogenome evolution in different decapod crustacean lineages.

Identification of Burrowing Shrimp Food Sources Along an Estuarine Gradient Using Fatty Acid Analysis and Stable Isotope Ratios

Two species of burrowing shrimp occur in high densities in US West Coast estuaries, the ghost shrimp, Neotrypaea californiensis, and the blue mud shrimp, Upogebia pugettensis. Both species of shrimp are considered ecosystem engineers as they bioturbate and irrigate extensive galleries within the sediment. While their burrows comprise a dominant habitat type in west coast estuaries, little is known about these shrimps’ diet and their role in estuarine food webs. The primary goals of this study were to identify major components of burrowing shrimp diets and detect variation in these diets along an estuarine gradient using combined fatty acid (FA) and stable isotope (SI) analyses. Shrimp and potential food sources including eelgrass blades, epiphytes, Ulva, sedimentary particulate organic matter (SPOM), burrow walls, and particulate organic material (POM) were sampled at different locations within Yaquina Bay, Oregon in August 2012. Both SI and FA analyses indicated differences in food resources assimilated by shrimp along the estuarine gradient. SI values showed that diets for U. pugettensis consisted of carbon sources derived primarily from POM and SPOM, while POM and epiphytes were primary carbon sources for N. californiensis. Shrimp from lower estuarine sites had high levels of 16:1ω7 and 20:5ω3 FAs suggesting their diet is enriched with marine diatoms. Shrimp from upriver showed greater proportion of FA associated with dinoflagellates and terrestrial sources as indicated by a high percentage of C18 polyunsaturated FAs (PUFAs). This is the first study to evaluate diets of these two shrimp species using complimentary FA and SI approaches.

The complete mitochondrial genome of the burrowing ghost shrimp, Nihonotrypaea harmandi (Bouvier, 1901), (Crustacea, Decapoda, Axiidea, Callianassidae) – a validation of the genus and species classifications

The complete mitochondrial genome of the burrowing ghost shrimp Nihonotrypaea harmandi was reconstructed using the Illumina HiSeq platform. The genome was 15,272 bp in length made up of 37 mitochondrial genes (13 CDSs, 22 tRNAs, and 2 rRNAs) in the same order as other Nihonotrypaea species. Phylogenetic analyses suggested that Nihonotrypaea is a valid genus, and that N. harmandi can be phylogenetically marginally separated from N. japonica, though some authors considered the former as a synonym of the latter.

Persistence, Extinction, and Recolonization of an Epibenthic Gastropod Population on an Intertidal Sandflat: 35-Y Contingent History of a Key Species of the Benthic Community in Metapopulation and Metacommunity Contexts

For marine benthos with planktonic larval stages, demographic metapopulation and empirical metacommunity studies are scarce. Asink nature was shown for a local intertidal sandflat population of the gastropod Umbonium moniliferumin an estuarine to coastal oceanic region in Amakusa, Kyushu, Japan. The gastropod has a 3-day planktonic larval duration (PLD). It inhabited 11 sandflats, which were shared by the ghost shrimp Nihonotrypaea harmandi. The shrimp is a burrow-dwelling bioturbator with a 30-day PLD. On one sandflat (hereafter U0) in Amakusa, the density and distribution of the two species was monitored from 1979 to 2014. All their main local populations were surveyed in 1998. In July 1979, the gastropod and shrimp were distributed on the lower and upper zones of U0 separately, with mean densities of 1,740 and 170 ind/m2. The gastropod population declined to extinction in 1986, associated with the increase in shrimp density to 440 ind/m2 and distribution to the lowest shore. Shrimp sediment destabilization was most likely to inhibit gastropod recruitment. The gastropod population began to recover in 1997 owing to shrimp population shrink. The regional survey results showed that (1) eight local populations (U0–U7 sandflats) of the two species along a 25-km shoreline of Amakusa, presumably, constitute each substantial metapopulation, and (2) their largest populations were at the shoreline opposite ends. These features would be generated by the interaction of speciesspecific larval dispersal traits and shoreline physiography. The threshold shrimp density of 160 ind/m2 precluding gastropod recruitment was detected from U1–U7. In 2001 and 2009, gastropod population density on U0 reached respective peaks comparable to that in 1979. This population fluctuation was due to varying recruit abundance, which corresponded well with the year-to-year change in shrimp population density across that threshold. The recolonization of the U0 gastropod population ought to be made by allochthonous larvae from the U1–U7 populations, especially U6–U7, suggesting a rescue effect in the source—sink relationship. The degree of self-persistency of the U0 gastropod population was estimated by calculating net reproductive rate (R0) based on the parameters about pre-settlement larval return-home and survival rates and post-settlement juvenile and adult survival rates. The availability of data set restricted the estimation to potential R0 for four year-segments, with each 1-y parameter set extrapolated to the gastropod 4-y life span. On U0 in 1979 to 1981, despite with minimum shrimp influences, the gastropod population could still be a demographic sink probably due to a limited larval return-home rate and due to a low post-settlement survival rate of juveniles caused by epibenthic predation or storm for their first 1 y to reach sexual maturity.

Associations between the pink wormfish, Microdesmus longipinnis (Weymouth), and the ghost shrimp, Lepidophthalmus louisianensis (Schmitt), in artificial burrows

Microdesmus longipinnis (Weymouth) is a small estuarine teleost fish that is known to feed on the eggs of the callianassid shrimp, Lepidophthalmus louisianensis (Schmitt). In the course of collecting M. longipinnis for physiological studies we noticed that there seemed to be a higher preference towards burrows of non-gravid and male shrimp than one would expect if the driving force behind this relationship was exclusively egg predation. In an attempt to expand upon the understanding of the relationship between these two animals we tested the hypothesis that the fish are not seeking out burrows based solely on the presence of eggs but rather the presence of the shrimp. Laboratory experiments demonstrated that M. longipinnis positively associated with male L. louisianensis when compared to empty burrows supporting the idea of a more complex relationship that has previously been reported in the literature. Further study is needed to fully determine the nature of the relationship between M. longipinnis and L. louisianensis.

New Early Cenozoic ghost shrimps (Decapoda, Axiidea, Callianassidae) from Pakistan and their palaeobiogeographic implications.

A new set of Paleocene and Eocene decapod crustaceans is described from the Kirthar Range of Pakistan. Two new ghost shrimps (Crustacea, Decapoda, Callianassidae) are described: Neocallichirus khadroensis Hyžný & Charbonnier, n. sp. from the Paleocene (Danian, Khadro Formation) of Gawar Band, Ranikot District, and Neocallichirus lakhraensis Hyžný & Charbonnier, n. sp. from the Early Eocene (Ypresian, Lakhra Formation) of Rbod Nala, Jhirak District. Both new species exhibit chelipeds which are morphologically surprisingly close to extant Neocallichirus karumba (Poore & Griffin, 1979) from the Indo-West Pacific. A group of species sharing this same cheliped morphology is provisionally called the "karumba group" based on Neocallichirus karumba, best documented species. The "karumba group" encompasses seven fossil species: the two new Pakistani species, Neocallichirus tuberculatus (Lőrenthey in Lőrenthey & Beurlen, 1929) n. comb. from the Eocene of Hungary, Neocallichirus borensis Beschin, De Angeli, Checchi & Mietto, 2006 from the Eocene of Italy, Neocallichirus birmanicus (Noetling, 1901) n. comb. from the Miocene of Myanmar, Neocallichirus dijki (Martin, 1883) from the Miocene of Java and Philippines, and the subfossil Neocallichirus maximus (A. Milne-Edwards, 1870) from Thailand. Based upon the extant and fossil occurrences, it is difficult to reconstruct migration pattern of the "karumba group". For now, it can be concluded, that at the genus level, a relative homogeneity of the ghost shrimps is observed between the Eastern and the Western Tethyan regions, as already suggested by Merle et al. (2014) for the assemblage of volutid gastropods from the Lakhra Formation.

Leptalpheus pereirai sp. nov., a new alpheid shrimp from Panama and Venezuela (Decapoda: Caridea).

A new species of the infaunal alpheid shrimp genus Leptalpheus Williams, 1965 is described based on material from three localities on the Caribbean coast of Panama and Isla Chimana Grande, Venezuela. Leptalpheus pereirai sp. nov. belongs to a group of species characterised by the presence of well-developed adhesive disks on the major chela and appears to dwell in burrows of the large callianassid ghost shrimp, Glypturus acanthochirus Stimpson 1866.

A new species ofParaglypturus(Crustacea: Decapoda: Axiidea: Callianassidae) from a vent field in the Tonga Arc of the south-western Pacific Ocean

A new species of callianassid ghost shrimp,Paraglypturus tonganussp. nov., is described and illustrated on the basis of five specimens that were collected from sediments in a vent field of the Tonga Arc, south-western Pacific Ocean. This new species is morphologically very similar toP. calderusTürkay & Sakai, 1995, the type species of the genusParaglypturusTürkay & Sakai, 1995. It differs fromP. calderusmainly in the absence (vs. presence inP. calderus) of an anterolateral row of setal pores on the carapace; the endopod of the second maxilliped, with a dactylus bearing stiff and thick serrate setae at the apex (vs. without inP. calderus); a yellow circular structure located on the ventral surface on the uropodal endopod (vs. on the dorsal surface on the uropodal exopod inP. calderus); and the articulation structure of the first pleopod in males (uniarticulate inP. tonganusvs. biarticulate inP. calderus). The new species is the first record of a ghost shrimp from a vent field of the Tonga Arc, and also the second reported species of the genusParaglypturus.

Tide-related biological rhythm in the oxygen consumption rate of ghost shrimp (Neotrypaea uncinata).

The effects of tidal height (high and low), acclimation to laboratory conditions (days in captivity) and oxygen level (hypoxia and normoxia) were evaluated in the oxygen consumption rate (OCR) of the ghost shrimp Neotrypaea uncinata We evaluated the hypothesis that N. uncinata reduces its OCR during low tide and increases it during high tide, regardless of oxygen level or acclimation. Additionally, the existence of an endogenous rhythm in OCR was explored, and we examined whether it synchronized with tidal, diurnal or semidiurnal cycles. Unexpectedly, high OCRs were observed at low tide, during normoxia, in non-acclimated animals. Results from a second, longer experiment under normoxic conditions suggested the presence of a tide-related metabolic rhythm, a response pattern not yet demonstrated for a burrowing decapod. Although rhythms persisted for only 2 days after capture, their period of 12.8 h closely matched the semidiurnal tidal cycle that ghost shrimp confront inside their burrows.

Second finding of the south western Atlantic ghost shrimp Ctenocheloides almeidai Anker & Pachelle, 2013 (Crustacea: Axiidea)

The ghost shrimp Ctenocheloides almeidai Anker and Pachelle, 2013 was described based on a single specimen collected at Ponta Verde, Maceio, state of Alagoas, northeastern Brazil. Here, we report the species from Porto Seguro, Bahia (~16o23'S), extending its distribution in the Brazilian coast in approximately 7 degrees south from the type locality in Maceio, Alagoas (~9o40'S). Notes on morphological variation of the species are provided based on the present material.