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The assessment of life history traits can help to better understand the population dynamics of the respective species. We present some life history traits of the freshwater crab Potamon ibericum (Bieberstein, 1809) from the western Alborz Mountains, Iran. Carapace size at the onset of morphometric maturity was estimated using the breakpoint of the relative growth of the chela and abdomen in males and females, respectively, by implementing piecewise linear regressions. In order to quantify variations in the estimated breakpoint, a bootstrap resampling method was applied. Allometric trajectories of chelar dimensions were also applied to juveniles and adults. Sexual size dimorphism was evaluated using the dimensions of the carapace and chelae, and patterns of the carapace shape dimorphism were investigated by implementing geometric morphometric analysis. The results showed that females reach morphometric maturity at smaller sizes than males, which could be of advantage in the fluctuating environment of their freshwater habitat in order to mate as soon as possible and increase fecundity. Positive allometric trends in the length of the major chela was observed in adults of both sexes, and the possible adaptive forces on the evolution of this pattern are discussed. Results of sexual dimorphism analyses confirmed male-biased sexual size dimorphism and functional adaptation of carapace shape in both sexes.

To highlight adaptation of an endemic species to an oceanic island environment, adult morphological characteristics and growth patterns were compared between a mitten crab endemic to the Ogasawara Islands ( Eriocheir ogasawaraensis ) and a congener from mainland Japan ( E. japonica ). Mean carapace width of E. ogasawaraensis was nearly 1.6 times larger than that of E. japonica in both sexes. A difference was detected in the carapace length versus carapace width relationship between these two species. Comparing chela propodus height versus carapace width, a sexual difference was detected similarly in both species, but males had only one growth phase in E. ogasawaraensis , whereas males of E. japonica were dimorphic due to two growth phases. The regression line obtained for male E. ogasawaraensis (chela propodus height versus carapace width) was nearly on the extending line of small-phase male E. japonica . Female E. ogasawaraensis had relatively larger chelipeds than female E. japonica . As for ambulatory legs, E. japonica males had relatively longer legs than females, but no sexual difference was detected in E. ogasawaraensis. Eriocheir ogasawaraensis had relatively shorter legs than male E. japonica but longer legs than female E. japonica . Therefore, in E. ogasawaraensis sexual dimorphism was not as differentiated as in E. japonica , and the adult male dimorphism recognized in E. japonica was absent. The large body size of E. ogasawaraensis is consistent with island gigantism that is commonly found in response to a lack of large predators on isolated islands. Evolution of dimorphism can be explained by sexual selection, and the differences between the island and mainland species are presumed to be correlated with differences in the mating behavior and/or environmental factors in their habitats.

A new palaemonid shrimp genus, Unesconia gen. nov., is established to accommodate a peculiar, small, presumably sponge-associated species, Unesconia coibensis gen. et sp. nov. The description of the new genus and species is based on several specimens found in the shallow marine waters of the Coiba Archipelago, Pacific coast of Panama. Unesconia gen. nov. does not seem to have close affinities to other eastern Pacific or western Atlantic palaemonid genera, including those harbouring sponge symbionts. On the other hand, it shares many characters with three Indo-West Pacific genera, which contain sponge-associated species, viz. Paraclimenaeus Bruce, 1988, Apopontonia Bruce, 1976 and Climeniperaeus Bruce, 1996. The most important diagnostic features of Unesconia gen. nov. are the strongly carinate, dorsally dentate rostrum, with its lateral carinae greatly expanded basally and armed with strong supraorbital teeth; the non-filtering mouthparts, with mandible lacking palp; the first pereiopod chela with excavated fingers and strongly tridentate fingertips; the asymmetrical second pereiopods (chelipeds), with the major chela bearing a double-fossa mechanism on the finger cutting edges; the ambulatory pereiopod dactylus armed with one large tooth and at least two small spinules on the ventral margin of the corpus, in addition to the terminal unguis; the lateral section of the uropodal diaeresis armed with five spiniform setae, the latter not extending to the lateral margin of the exopod; and the telson with two pairs of stout long cuspidate setae on dorsal surface and three pairs of strong, elongate spiniform setae on the posterior margin.

The sulphur-rich and acidic vent waters of a shallow hydrothermal vent field next to Kueishan Island in Taiwan provide a specific and generally toxic environment. Among only a few aquatic organisms able to survive there, the grapsoid crab Xenograpsus testudinatus is the dominant species with a high population density in the vent area. Here we study the gender-specific distribution, morphological traits, and relationship of wet weight vs. carapace width of this crab. A total of 1120 individuals including 831 male and 289 female (included 15 ovigerous) were examined during August and September in 2011 and May and September in 2012. Except in August 2011, there are no significant differences in the distribution of X. testudinatus in the hydrothermal vent area from the vent spout during most months. Among crabs, the weight of male (6.87 ± 2.90 g) was significantly heavier than that of females (4.17 ± 1.25 g) (p < 0.001, Student's t-test). As for the wet weight of crabs, significant differences were noted in both the length of chela and the width of carapace between males and females. Sexual dimorphism of X. testudinatus is evident in three morphological traits. Pearson's correlation showed a significant and positive correlation (p < 0.001) of wet weight, width of carapace and length of chela of the two sexes. Ovigerous crabs (shortest carapace width: 1.93 cm) were present in the specimen collected from August 2011 and May 2012. The ovigerous crabs were not found in the samples collected from September in both years 2011 and 2012, indicating that reproduction may have ceased during the period of sampling. The present results suggested that the reproductive period of X. testudinatus was before September. The distribution pattern and sexual dimorphism of X. testudinatus provided a better understanding of the idiobiology of this dominant metazoan in the hydrothermal vent area.

Despite growing evidence that crustaceans produce and detect sounds, the behavioural and biological function of these sounds is still poorly understood. Here, we describe sounds produced by the New Zealand paddle crab, Ovalipes catharus, and provide evidence of intraspecific communication using underwater sound. Acoustic and video analyses of tank-based experiments show that O. catharus produce at least three distinct sounds: the rasp, zip and bass. Notably, two of these sounds, the zip and bass, were directly correlated with post-copulatory mate-guarding and courtship behaviour and produced only by competing adult male crabs in the presence of a receptive female. Rasp sounds were produced by both sexes; the occurrence significantly increased in the presence of food, and play-back experiments of these sounds initiated a foraging-like behaviour. Responses to rasps might have evolved as a result of acoustic spying. Further, we show that both the rasp and bass sounds were produced by an alternative mechanism than stridulation of the chela ridges. This refutes widespread assumptions that Ovalipes crabs use only stridulation of ridges along their chelae to produce rasp-like sounds. Our results suggest that sound production in decapod crustaceans may be more widespread than previously presumed.

Coloration, gene-sequence data (H3, 12s, 16s), and subtle features in morphology support the description of two new species, both formerly regarded to represent accepted variants of Phimochirus holthuisi s.l. While color in life consistently separates these species from P. holthuisi s.s. and from each other, morphological distinctions are subtle and less than absolute in small specimens, being based on ventral spine counts of walking leg dactyls and relative development of the superior crest on the major chela. Molecular phylogenetic analyses clearly support the separation of sister clades, representing two new species, from P. holthuisi s.s. as well as other congeners available for analysis. Both of the new species are presently known to occur widely throughout the northern Gulf of Mexico, though one occurs more commonly in the northeastern and southeastern Gulf, and may range as far south as Suriname. The other has been taken primarily in the northwestern Gulf, and is not known from outside Gulf waters. While both of the new species appear restricted to relatively deep subtidal waters of the continental shelf, Phimochirus holthuisi s.s. is instead more commonly found in shallow nearshore tropical waters on or near coral reefs. Previous literature reports of P. holthuisi usually represent, at least in part, one or both of these two new species.

A new species of the alpheid shrimp genus Salmoneus Holthuis, 1955, probably an obligate associate of ghost shrimp burrows, is described based on material from Oman (type locality: Darsait near Muscat), Iran and the Philippines. Salmoneus durisi sp. nov. is characterised principally by both chelipeds enlarged, robust, with ventral and dorsal margins of chelae carrying long fine setae, and with minor chela fingers armed with a few large teeth on cutting edges. All specimens of Salmoneus durisi sp. nov. were collected either directly from burrows of larger decapod crustaceans with the aid of a suction pump, or by exposing burrows dug under large subtidal rocks. The Iranian specimen was found together with its presumed host, Neocallichirus calmani (Nobili, 1904). Two additional specimens from Indonesia and the Solomon Islands are tentatively assigned to S. cf. durisi sp. nov., awaiting further studies.

A new snapping shrimp, Alpheus perlas sp. nov., is described based on a single complete male specimen collected on a shallow mudflat at Casayeta Island in the Las Perlas Archipelago, Gulf of Panama. The new species belongs to the large A. edwardsii (Audouin, 1821) species group characterised essentially by the presence of two notches on the major chela palm, with the dorsal notch extending posteriorly on the mesial surface. Within the eastern Pacific members of the A. edwardsii group, A. perlas sp. nov. appears to be morphologically closest to A. latus Kim & Abele, 1988 and A. burukovskyi Anker & Pachelle, 2015. Alpheus perlas sp. nov. does not seem to be specially adapted for digging and may be inquiline of a larger burrowing host, which currently remains unknown.

The present study deals with five species of the alpheid shrimp genus Salmoneus Holthuis, 1955 from the tropical eastern Pacific. One of them is new to science and is described as Salmoneus tiburon sp. nov. The new species is presently known only from the Las Perlas Archipelago in Panama and can be distinguished from all other congeners by the dentition on the cutting edges of the major chela, with some dactylar teeth reminiscent of shark teeth. It is also one of the largest species of the genus, with the carapace length of both type specimens surpassing 8.0 mm. Salmoneus serratidigitus (Coutière, 1897), a species with an ample distribution across the Indo-Pacific, is recorded for the first time from the Pacific coast of Panama and is confirmed from Colombia. Salmoneus malagensis Anker & Lazarus, 2015, previously known only from Bahía Málaga in Colombia, is recorded from Panama’s Azuero Peninsula. The remaining two species, S. excavatus Anker, 2011 and S. alvarezi Anker & Lazarus, 2015, are recorded regionally from Las Perlas Archipelago in Panama and Playa Tarcoles in Costa Rica, both for the first time since their original descriptions. An identification key to the five currently known eastern Pacific species of Salmoneus is provided. However, several immature and/or incomplete specimens herein preliminarily reported as Salmoneus spp., as well photographic records from southern California, USA, indicate the presence of further undescribed species in the eastern Pacific.

A new species of sponge–dwelling snapping shrimp , Synalpheus amintae sp. nov. from the Parque Nacional Natural Isla Gorgona, Pacific coast of Colombia, is described. This new species pertains to the denominated Synalpheus “ Gambarelloides ” species group sensu Coutiere (1909)—previously known as “ Laevimanus ” group. It was collected in the southern part of the Island, during episodes of extreme low tides, known locally as “puja”. Synalpheus amintae sp. nov. is closely related to the only two other known species of the S. “ Gambarelloides ” species group from the eastern Pacific: Synalpheus occidentalis Coutiere, 1909, from Gulf of San Jose, Lower California, and Synalpheus mulegensis Rios, 1992, from Bahia Concepcion, Gulf of California, and can be differentiated from them by the poorly developed distal portion of pollex of the major cheliped, the armature of the distal segment of third maxilliped, and the number of acute teeth of exopodal uropod. A discriminative analysis dealing with other three species of Synalpheus from the western Atlantic, with distinctive pollex of major chela reduced, is presented. A dichotomous key was elaborated to identify the species of Synalpheus “ Gambarelloides” species group from the eastern Pacific. The number of valid species described of Synalpheus from the eastern Pacific is increased to 23.

A new species of semi-terrestrial sesarmid crab of the genus Geosesarma De Man, 1892, is described from central Taiwan. Geosesarmamirumsp. nov. is distinct in possessing a strong transverse crest on the inner surface of the male chela and a diagnostic male first gonopod which is relatively long and stout, with the distal chitinous part broad and spatuliform. Like most Geosesarma species, G.mirumsp. nov. has large eggs and direct development, contrasting with the only other species known from Taiwan, G.hednon Ng, Liu and Schubart, 2004, which has small eggs and planktotrophic larvae.

Lobithelphusa Rodriguez, 1982 is endemic to southern Mexico. Assigned to this monotypic genus is the freshwater pseudothelphusid crab, L. mexicana Rodriguez, 1982. The original description based on an old, dry, male specimen in the collections of the Natural History Museum, London, is brief and the crab was only partially figured. Lobithelphusa mexicana has subsequently never been recorded from Mexico and, consequently, the conservation status of this species is unknown. The type specimen has a complete, but detached left chela; is devoid of the left ambulatory pereiopods 1–3, with the fourth missing the carpus, propodus and dactylus; and its left first gonopod detached but retained in a glass tube kept adjacent to the crab. In spite of this damage the crab is still in remarkably good condition for a specimen registered in 1860. The purpose of this study is to apply computed tomography (CT) scanning techniques on the extant type, including its first gonopod, in order to provide detailed illustrations of the crab. These, in turn, shall be used to re-describe the species in order to help establish the current distribution status of L. mexicana in Mexico, and clarify its systematic position within the Pseudothelphusidae Ortmann, 1893.

The palaemonid shrimp genus Palaemon Weber 1795 is currently represented by 87 species worldwide, of which 36 species inhabit freshwater environments. In this study, we describe a new species of the genus, P. septemtrionalis, primarily based on material collected from rivers in Miyagi Prefecture, Tohoku District, northeastern Japan. The present new species is morphologically and genetically close to Palaemon paucidens De Haan, 1841, but it is morphologically distinguishable from the latter by the chela of the pereopod 2 being longer than the carpus (versus shorter than the carpus in P. paucidens) and the possession of a low, laminar convexity on the flexor margin of the pereopod 3 dactylus just proximal to the base of the unguis (such a laminar structure is absent in P. paucidens). Comparison of partial sequences of the mitochondrial 16S rRNA gene supports the recognition of the new species. Examination of museum collections and a BLAST search on GenBank revealed that the geographical range of the new species includes the Sea of Japan side ranging from Hokkaido to Hyogo Prefecture and the Pacific side ranging from Aomori to Miyagi Prefecture. An identification key to the 13 Japanese species of the genus is presented.

A new secretive, yet brightly colored hermit crab species of the family Paguridae, Pylopaguropsis mollymullerae sp. n., is fully described based on specimens from the reefs of Bonaire, Lesser Antilles, southern Caribbean Sea. Populations of this new species were discovered and photographed in the Bonaire National Marine Park under a large coral ledge, at a depth of 13.7 m, living in crevices known by scuba divers to serve as den to a pair of “flaming reef lobsters” Enoplometopus antillensis, or a “broad banded moray” Channomuraena vittata. This new species is only the second species of Pylopaguropsis Alcock, 1905 known from the western Atlantic, the 20th named worldwide, and belongs in the teevana group of species of the genus. It is remarkably similar, and herein considered geminate, to the tropical eastern Pacific congener, Pylopaguropsis teevana (Boone, 1932), the two being characterized and uniquely different from all other species of the genus, by the striking and deeply excavated, scoop-like ventral surface of the chela of the right cheliped. Minor differences separate this new species from Pylopaguropsis teevana in the relative length of the antennal acicles (exceeding the corneas versus not exceeding the corneas in Pylopaguropsis teevana); dorsal armature of the right chela (smooth or with scattered minute tubercles versus with numerous small tubercles in Pylopaguropsis teevana); surface shape of the lateral face of the dactyl of right pereopod 3 (evenly convex versus flattened in Pylopaguropsis teevana); and coloration (red bright red stripes versus brown stripes in Pylopaguropsis teevana). The highly visible color pattern of bright red stripes on white background typical of decapods known to have cleaning symbioses with fish, dense setation on the flagella of the antennae, and preference for a crevicular habitat, combined with brief in situ nocturnal observations, suggests the possibility that Pylopaguropsis mollymullerae sp. n. engages in “cleaner” activities or functions as a “den commensal” with moray eels. The morphology and possible meaning of the observed behavior is discussed. A tabular summary of the distribution, habitat, and published information on all species of Pylopaguropsis is presented. Supplemental photographs and a video of live Pylopaguropsis mollymullerae sp. n. are included.

The nominal genera Chelomalpheus Kim, 1998 and Cavipelta Hayashi, 1998 were treated as synonyms of Stenalpheops Miya, 1997 in the paper by Anker et al. (2001). Therefore, the type species of those genera (Chelomalpheus koreanus Kim, 1998 and Cavipelta yamashitai Hayashi, 1998, respectively) were synonymized with S. anacanthus Miya, 1997. Actually, those authors ignored that the morphological characters of the three species mentioned above show differences. For instance, all type specimens of Chelomalpheus koreanus Kim, 1998 are without a caudal appendix; the large male specimens of Cavipelta yamashitai Hayashi, 1998 have an abnormal shaped chela, which corresponds with the middle stage in a growth series of another nominal species, i.e., S. anacanthus. The opportunity to study abundant specimens from the China seas established that the type specimens of S. anacanthus Miya, 1997 are in fact composed of two species, and the same was found for the type specimens of Cavipelta yamashitai Hayashi, 1998; in addition, Chelomalpheus koreanus Kim, 1998 was found to be a valid species and is transferred to Stenalpheops; and S. crangonus (Anker, Jeng & Chan, 2001) is herein synonymized with S. anacanthus Miya, 1997, which name has priority, and this valid species is now re-described herein.

A new sponge-associated species, Paraclimenaeus michaeli sp. nov. from Sulawesi, Indonesia, and Singapore, is described and illustrated. The new species can be distinguished from its congenerics by: (1) the downwards curved rostrum with 2 acute dorsal teeth subdistally, (2) the absence of subdistal teeth on the fixed finger of the major second chela, (3) the pairs of dorsal telson spines at about 0.33 and 0.66 of the telson length, (4) the caudal fan sparsely setose, and (5) the second pereiopods without subdistal teeth on fixed finger. To evaluate its relationship with congenerics and species of the related genera Apopontonia and Climeniperaeus, a phylogenetic analysis based on the 16S mitochondrial gene is presented. A key for the identification of the species in Apopontonia, Climeniperaeus and Paraclimenaeus is proposed.

This paper uses Chela Sandoval’s (2000) concept of meta-ideologizing to examine how definitions of ‘access’ are reframed to further the goals of social justice activists. Meta-ideologizing refers to re-operationalizing liberal, widely-accepted terms to fit the needs of a community. The paper draws from 14 semi-structured interviews with individuals pivotal to the passing and implementation of Toronto’s ‘Students Without Legal Immigration Status Policy’, also known as a ‘Don’t Ask, Don’t Tell’ policy. It also employs data from literature developed by stakeholders as well as the author’s experiential knowledge. It examines how organizers have reframed the concept of ‘access’ by extending its focus beyond entry into schools and including the need for undocumented migrants to be safe and have access to other social services. It also analyzes the ways bureaucratic logic can invisibilize the gains made by developing procedures that reify illegalization.

The distribution and occurrence of epibionts on the dorsal carapace, ventral carapace and chela of 325 specimens of Callinectes amnicola (De Rocheburne, 1883) (103.4 – 138.7 mm carapace width) from the Qua Iboe (QIRE) and Imo River (IRE) estuaries in southeast Nigeria was determined. The only ectosymbiont observed was cirriped barnacle, Chelonibia patula, mostly of smaller sizes (2.25 mm), infesting only 25-29% of intermoult crabs, more on females and in the Imo River estuary, with an average of four barnacles per crab, presupposing low level of epibiont-host interaction. There was no significant difference (P>0.05) in spatial distribution but epibionts were highest in the dry season in low salinity IRE (0.53‰) and in wet season in the medium-salinity QIRE (17.4‰). No public health risk has been reported among crab consumers in the study area. This study highlights epibiont-host interaction in the study area largely unknown for proper management of the fishery., Određena je distribucija i pojava epibionta na leđnoj i trbušnoj strani oklopa i kliještima kod 325 uzoraka Callinectes amnicola (De Rocheburne, 1883) (103,4 - 138,7 mm širine oklopa) s ušća rijeka Qua Iboe (QIRE) i Imo (IRE) u jugoistočnoj Nigeriji. Jedini uočeni ekosimbiont je rak vitičar, Chelonibia patula, uglavnom manjih dimenzija (2,25 mm) na samo 25-29% rakova, više kod ženki na ušću rijeke Imo, s prosjekom od četiri vitičara po raku, što ukazuje na nisku interakciju epibionta-domaćina. Nije bilo statistički značajne razlike (P > 0,05) u odnosu na prostornu rasprostranjenost, ali epibionti su bili najviši u sušnom razdoblju u IRE niske slanosti (0,53 ‰), te u vlažnoj sezoni u QIRE srednje slanosti (17,4 ‰). Nije bilo utvrđenih rizika za zdravlje među konzumentima rakova u području istraživanja. Ovo istraživanje naglašava interakciju epibionta-domaćina u području istraživanja koje je u velikoj mjeri nepoznato po pravilnom upravljanju ribarstvom.

Successful invasion by nonindigenous species is often attributed to high propagule pressure, yet some foreign species become widespread despite showing reduced genetic variation due to founder effects. The signal crayfish (Pacifastacus leniusculus) is one such example, where rapid spread across Japan in recent decades is believed to be the result of only three founding populations. To infer the history and explore the success of this remarkable crayfish invasion, we combined detailed phylogeographical and morphological analyses conducted in both the introduced and native ranges. We sequenced 16S mitochondrial DNA of signal crayfish from across the introduced range in Japan (537 samples, 20 sites) and the native range in western North America (700 samples, 50 sites). Because chela size is often related to aggressive behavior in crayfish, and hence, their invasion success, we also measured chela size of a subset of specimens in both introduced and native ranges. Genetic diversity of introduced signal crayfish populations was as high as that of the dominant phylogeographic group in the native range, suggesting high propagule pressure during invasion. More recently established crayfish populations in Japan that originated through secondary spread from one of the founding populations exhibit reduced genetic diversity relative to older populations, probably as a result of founder effects. However, these newer populations also show larger chela size, consistent with expectations of rapid adaptations or phenotypic responses during the invasion process. Introduced signal crayfish populations in Japan originate from multiple source populations from a wide geographic range in the native range of western North America. A combination of high genetic diversity, especially for older populations in the invasive range, and rapid adaptation to colonization, manifested as larger chela in recent invasions, likely contribute to invasion success of signal crayfish in Japan. © 2016 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.

A small morphological variation of an organ may cause a major change of its function in animal evolution. The function of decapod chela varies considerably among taxa, between sex, and even within an individual, but also retains a simple mechanism of motion. Therefore, the decapod chela is a suitable structure to study the evolutionary process of functional diversifications, although the relationship of form and function is inadequately understood, yet. We estimated the mechanical advantages of pinching and passive disarticulation resistance, and chela size relative to the carapace in 317 chelae of 168 decapod specimens, and compared these indices with the functions of each chela. Our study revealed that mechanical advantages of pinching efficiency and passive disarticulation resistance were greatest in shell-crushing chelae, followed by gripping and pinching chelae, whereas the chela size relative to the carapace was not related to differences among these functions. We also found that the chelae are designed to retain the ratio between depth and width of the proximal dactylus. In the evolutionary process of decapods, the diversifications of chela functions were accompanied by the diversifications of the mechanical advantages, and played an essential role in their ecological diversification. J. Morphol., 2016. © 2016 Wiley Periodicals, Inc.

We studied the ontogenetic allometry pattern in the freshwater brachyuran crab Potamon fluviatile (Herbst, 1785) to describe some new sexual dimorphic features on the ontogenic trajectories of the chelae. We surveyed carapace width, chela length and width, dactylus length, and propodus length of both chelae of 93 females and 114 males to the nearest 0.05 mm using a vernier caliper. Our main result was the identification of morphological biometry showing a variability of the chela linked to growth allometry, with some different between-sex ontogenic trajectories. Specifically, we emphasized how the morphometric features of the chelae change during body-size growth with different increasing rates. Particularly, the observed significant shape changes are mainly due to positive allometries in both sexes, although negative allometries (the latter visible only in the propodus length of females) and isometries were observed as well. Our study confirms that a form of sexual dimorphism exists in the ontogenetic allometric trajectories of P. fluviatile in both the large and small chelae, these trajectories being related to mechanical aspects in predation, food manipulation, mate acquisition, and between-sex differences in aggressiveness during antagonistic fights.

We have investigated the microstructures and mechanical properties of four crab species Paralithodes brevipes, Eriocheir japonicas, Geothelphusa dehaani, and Telmessus acutidens and analyzed the molecular and elemental data of their chela. In the visible brown region (BR) at the distal end of the dactylus tip in Paralithodes brevipes and Eriocheir japonicas, the elastic modulus and calcium (Ca) content were lower than in the white region (WR). Near the interface between BR and WR, Ca, and carbon (C) composition changed continuously. Molecular analysis shows that the dactylus tips of the chela in P. brevipes and E. japonicas were composed of chitin and calcium carbonate. In G. dehaani and T. acutidens, the Ca concentration was homogeneous in the top portion (TP) of the dactylus dentitions. The lowest value of Ca concentration was found near the surface of the bottom portion (BP) on the dactylus dentitions. In G. dehaani, the elastic modulus distribution in the TP was maximum near the outermost surface, and gradually decreased in the inner layers; the lowest elastic modulus in the BP was near the outermost surface, and the distribution increased in the inner layer. These results show that the biological composite was as a continuous structure near the interface of the dactylus tip. Understanding the microstructures of the dactyla of crabs might help the study and development of bio-inspired composites for pinching.

The additive genetic correlations of processing traits (two traits, abdominal meat weight and yield) with growth (body weight) and morphometrics (seven traits, chela length, chela width, cephalothorax length, cephalothorax width, abdominal length, abdominal width and abdominal depth) in red swamp crayfish (6 months old) were first estimated within two sexes based upon the additive-dominance genetic model under two rearing environments. Three geographic broodstocks of Procambarus clarkii (Guantan, Dapu and Yanghe) were used. The genetic mating design was incomplete diallel cross, in which three mating combinations (Guantan ♂ × Dapu ♀, Guantan ♂ × Yanghe ♀, and Dapu ♂ × Yanghe ♀) were produced. Path analysis method was then used to ascertain the overall genetic determinations of growth and morphometric traits on processing traits. The objective of this study is to recommend feasible strategy for improvement of processing traits in P. clarkii. The results indicated that body weight was highly positively correlated with processing traits; chela traits were negatively correlated with abdominal meat weight and positively correlated with abdominal meat yield, but very small in magnitude; negative genetic correlations occurred between cephalothorax dimensions and processing traits; abdominal dimensions were positively correlated with processing traits. Upon pursuing indirect selection for processing traits, body weight should be the primary candidate for direct selection, and at the same time smaller cephalothorax or larger abdominal dimensions also should be taken into consideration.

Dryinidae are parasitoid wasps within the aculeate (Hymenoptera) superfamily Chrysidoidea that are known for the pincer-like chela that most females use to restrain their hosts and prey (Auchenorrhyncha). Herein, a new species of the genus Hybristodryinus Engel, 2005 is described from mid-Cretaceous Kachin (Burmese) amber. Hybristodryinus moutesoe sp. nov. is diagnosed, described, and incorporated into the pre-existing key to Hybristodryinus. The new species is most similar to H. mon Perkovsky, Olmi, Muller and Martynova, 2019, but differs in characteristics of the pronotum, greater distance between notauli, and greater distance between inner edges of the lateral ocelli (POL). A review of the Dryinidae from Kachin (Burmese) amber is also included.

Raptodryinus patrickmuelleri gen. et sp. nov., that belongs to Raptodryininae subfam. nov. (Hymenoptera: Dryinidae), is described from Burmese amber. Raptodryininae subfam. nov. represents one of the first fossil groups of chelate dryinids, documenting the fact that the evolution of chela still took place at the earliest Late Cretaceous. It is characterized by a very peculiar chela, composed of a proximal lobe of the fifth protarsomere opposable on a complex composed of the fifth protarsomere + arolium + both claws. This type of chela differs completely from the common chelae of extant and known fossil pincer wasps (composed of one enlarged claw opposable on a more or less strongly projecting fifth protarsomere). The chela of R. patrickmuelleri represents probably an early evolutionary stage of pincer wasps close to the basal Dryinidae, whose females were achelate. This discovery enabled us to outline the evolution of the chela of Dryinidae. In the evolution of pincer wasps, the oldest known fossil species, Aphelopus palaeophoenicius Olmi 2000, from Barremian Lebanese amber is of special importance as a basal exemplar. We had re-examined this species and attributed it to a new genus, Archaeodryinus gen. nov., and a new subfamily, Archaeodryininae subfam. nov., documenting the first known basal achelate pincer wasp. The emended data on the subfamily Aphelopinae suggest that this taxon is known only since the Miocene and that its females had secondarily lost their chelae. The discussion on biological features of Aphelopus that enabled parasitism on Typhlocybinae (Hemiptera: Cicadellidae) is also given.

Some brachyuran crabs from the Pliocene of a new outcrop nearby Borgomanero (Novara, Piedmont, NW Italy) are reported. This study allows us to recognize a peculiar brachyuran crabs assemblage including: Macropipus cf. M. tuberculatus Prestandrea, 1833 (Polybiidae Ortmann, 1893), first report for this species from the Pliocene fossil record, and an indeterminate representative of Mursia Leach in Desmarest, 1822 (Calappidae De Haan, 1833), genus never recorded previously in the Mediterranean basin. Finally, a single chela is referred to Calappa sp. (Calappidae De Haan, 1833).

A new species of the stenopodidean shrimp genus Odontozona Holthuis, 1946 is described and illustrated on the basis of 3 specimens recently collected from submarine caves of Okinawa-jima and Ie-jima Islands, the Ryukyu Islands, southwestern Japan, Indo-West Pacific. Odontozona okunoi sp. nov. closely resembles O. anaphorae Manning & Chace, 1990 described from Ascension Island, South Atlantic Ocean, but differs from it by a combination of morphological characters, including the large cardiac spine on the carapace, the spines on the pleural surface, the posterior tooth of the telson, the irregular row of small spines on the dorsomesial surface of the third pereopod chela, as well as the length ratio of the third pereopod chela against carpus and merus. This study increases the total number of species described in the genus Odontozona to 21, nine of which occur the Indo-West Pacific.

A new species of caridean shrimp of the family Alpheidae, Automate isabelae sp. nov., found in stomach analysis contents of the lane snapper Lutjanus synagris (Linnaeus, 1758), from the Keys and SW coast of Florida, Gulf of Mexico, is described. The abdomen and portions of the cephalic appendages were damaged in holotype, but remainder of the body and the chelipeds, whith the most important diagnostic characters are in decent or perfect condition, the description was further supplemented based on intact morphological parts of the paratypes. The presence of tubercles on the dorsal and ventral margins of the major chela palm, shows this new species to be related to the eastern Pacific Automate rugosa Coutière, 1902. Both congeners can be easily discriminated by the proportions and shape of the third maxilliped, the proportions and ornamentation of the carpus, merus, and chela of the major cheliped, the ventral seta of the carpus of the minor cheliped, the presence of a distoventral spine on the propodi of third and fourth pereopods, the armature of dorsal surface of telson, and their geographical distribution. The description of this new species increases the number of worldwide valid species known of the genus Automate to 12.

Crabs of the family Pinnotheridae have been considered a phylogenetically heterogeneous group and taxonomically problematic (Palacios-Theil 2009, 2016; Tsang et al. 2018). The lack of knowledge of sexual dimorphism and morphological variation throughout the life history for many species have complicated its taxonomy and has resulted in errors in its classification (Campos 1989, 1993, 2016). Consequently, if the taxonomy of these symbiotic crabs had been based on juveniles and undeveloped character states, the problems get even more serious (Campos 1989, 1993). Melzer & Schwabe (2008) studied three juvenile crabs living in the chiton Tonicia chilensis (Frembly, 1827) (Polyplacophora: Chitonidae) collected in Muelle Dichato, Chile, and they identified them as the putative invasive stage of a species of Orthotheres Sakai, 1969. The crabs are of the typical juvenile pinnotherid form with a masculine habitus, including a suborbicular carapace, large eyes and a slender pleon (= abdomen) with the telson well defined (Ocampo et al. 2017). Unpublished observations on juveniles and adults of several species of pinnotherid crabs by the author, for example, Juxtafabia muliniarum (Rathbun, 1918), Dissodactylus lockingtoni Glassell, 1935, D. xantusi Glassell, 1936, Calyptraeotheres granti (Glassell, 1933), Austinotheres angelicus (Lockington, 1877) and Tumidotheres margarita (Smith, 1870) have revealed that the third maxilliped exhibit little morphological variation through the post-larval stages of development (from juvenile to adult). This appendage, including the partial or total fusion of the ischium and merus (Fig. 1A–G; Fig 2A, C–G), has been considered a valuable feature for distinguishing genera in the family Pinnotheridae (Bürger 1895; Rathbun 1918; Manning 1993; Ahyong & Ng 2007; Campos 2009). According to Melzer & Schwabe (2008) the ischium and merus of the third maxilliped are completely fused, the carpus is larger than the propodus and the small dactylus is subterminally inserted on the propodus (Fig 1C), and as such the juveniles studied are possibly members of the genus Orthotheres Sakai, 1969. A detailed re-examination of the third maxilliped, chela of pereiopod 1 (cheliped) and pleon, however, has shown otherwise. Campos (1989) discussed the taxonomy of Orthotheres and treated all the species he recognised as belonging to this genus; characterising its members by its diagnostic third maxilliped palp structure. Ng & Ho (2014) rediagnosed the genus based on the type species, O. turboe Sakai, 1969, from Japan, and restricted it for three Indo-West Pacific species; commenting that the American species as well as some Indo-West Pacific taxa will need to referred to other genera when a full revision is done. This revision is now in progress by the author, PKL Ng and ST Ahyong. Until the revision is complete, the genus is treated here in the broader sense of Campos (1989) and Geiger & Martin (1999).

A new snapping shrimp is described based on several specimens collected on a shallow coral reef off Isla Popa in Bocas del Toro, on the Caribbean coast of Panama. All specimens of Alpheus naranjo sp. nov. were extracted from dead colonies of the thin-leaf lettuce coral, Agaricia tenuifolia Dana, at a depth of about 2 m. Based on its morphological characteristics, the new species belongs to a small species complex that also includes A. blachei Crosnier & Forest, 1965 from the tropical eastern Atlantic, and A. felgenhaueri Kim & Abele, 1988 and A. confusus Carvacho, 1989, both from the tropical eastern Pacific. Alpheus naranjo sp. nov. can be separated from all of them by the relatively longer fingers of the minor chela, which are devoid of balaeniceps setae, as well as some other morphological details. In the western Atlantic, A. naranjo sp. nov. is the only large uniformly orange-red snapping shrimp, hence its proposed new name. The colour patterns of A. blachei and A. confusus are illustrated for the first time.

A new species of pinnotherid crab, Arcotheres shahi n. sp., is described on the basis of specimens collected during a crustacean survey along the coastal areas of Pamban fishing harbor in the Gulf of Mannar, Tamil Nadu state, east coast of India. The new species resembles A. pernicola (Bürger, 1895), A. winckworthi (Gordon, 1936) and A. rayi Ahyong & Ng, 2007, in having the dactyli of the longer fourth pereopod longer than that of fifth pereopod. Arcotheres shahi n. sp. differs from these three known species in the shape of female carapace, frontal region and chela, setal pattern on the dactyli of the fourth and fifth pereopods and relative length of the ambulatory pereiopods.

Based on extended surveys in Kuala Belalong Field Studies Centre, Brunei Darussalam, one new species of Kuzicus is described here: Kuzicus mirabilis sp. nov. This represents the first species described from Borneo for this Asiatic genus. The female of Pulchroteratura huiqing Tan et al., 2017 is described here, first time for the genus. The females of Leptoteratura (Rhinoteratura) chela Tan et al., 2017 and Pseudoteratura (Pseudoteratura) kenuan Tan et al., 2017 are also described for the first time.

A new species of deep-sea yeti crab, Kiwa araonae , is described from a hydrothermal vent field, Mujin (“Misty Harbor”), at a depth of about 2000 m on the Australian-Antarctic Ridge (AAR), Southern Ocean. The Mujin vent field (62°11.79′S), in a large, unexplored gap in the Circum-Antarctic Ridge system, is the most southern record for a yeti crab to date. Kiwa araonae n. sp. is the fourth described species in the family Kiwaidae Macpherson, Jones and Segonzac, 2005, and the second known from the Southern Ocean. This new species differs morphologically from its three congeners by the having a nearly flat branchial region, relatively short rostrum, third sternite with parallel lateral margins, slender chela, straight fingers of the chela, and propodi of pereiopods 2-4 with three corneous spines on the flexor margins. The Bayesian phylogenetic tree and the genetic distance based on the mitochondrial 16S rRNA gene (408 bp) clearly indicate the distinctiveness of this species. The discovery of Kiwa araonae in the AAR suggests a possible biogeographic connection of the Southern Ocean vent faunas. The presence of a new hydrothermal vent field with endemic species in the AAR provides additional information on the global biogeography of deep-sea vent faunas.

A new species of the alpheid shrimp genus Salmoneus is described and illustrated from Aqaba, the Red Sea. Salmoneus chadwickae, sp. n., is the fifth member of the S. cristatus species-group, it is distinguishable from all congeners by a strongly hooked, right-angled tip of the fixed finger on the major chela. The new species is compared with known species from the Red Sea, and with other species of the S. cristatus species-group from other Indo-West Pacific regions, and confirmed also with the combined analysis of mitochondrial and nuclear gene sequences (16S and H3, respectively). A 19th century sample of Salmoneus spp. donated by H. Coutiere to the Museum National d’Histoire Naturelle, Paris, was examined; it revealed a mix of several species that are reported and illustrated here. New records of S. auroculatus from the Philippines, S. aff. cristatus from Papua New Guinea (PNG), S. gracilipes from PNG, and of S. tricristatus from Taiwan, are provided, and a possible occurrence of S. aff. gracilipes and S. aff. seticheles in the Red Sea is discussed. Five species of the Indo-West Pacific S. cristatus species-group have been analysed using morphological and molecular comparisons. An identification key to the species of the S. cristatus species-group is provided.

The contribution deals with crab remains from Middle Eocene flysch beds of environs of ]opi in central Istria, Croatia. Two specimens belong to the relatively abundant species Lophoranina marestiana (Konig, 1825). A part of carapace and a segment of chela belong to the species Lessinicarcinus euglyphos (Bittner, 1875). A smaller crab stone cast could not be taxonomically interpreted due to its poor state of preservation.

A new species, Ilyoplax sayajiraoi , belonging to the family Dotillidae is described from Gujarat state, India. It differs from its closely related species, Ilyoplax stevensi and Ilyoplax frater by differences in shape and proportions of the carapace, shape, and setae arrangement pattern on chela and morphologies of male and female abdomen. The details on the morphological differences are presented in this study.

Euscorpiops artemisae sp. nov. from Myanmar and Euscorpiops orioni sp. nov. from Thailand are described and compared with other species of the genus Euscorpiops Vachon, 1980. A key to the species of Euscorpiops is provided. Sexual dimorphism is present, as males of some species have a narrower pedipalp chela than females, while in other species the shape of the chela is the same in both sexes. Males of both new species have the pedipalp chela very narrow, in the male holotype of E. artemisae sp. nov. the chela length to width ratio is 4.13 and in the male holotype of E. orioni sp. nov. it is 4.58. In addition to morphological analysis, we describe also the karyotype of male holotype and paratype of E. orioni sp. nov. Both analyzed specimens have achiasmatic meiosis and the same number of chromosomes (2n=103) with predominance of acrocentric chromosomes gradually decreasing in size. During the first meiotic division we observed one trivalent in both males. This type of multivalent indicates centri...

Observations of behavior and direct measurements of force indicated that the cancrid crab Cancer productus could directly crush only the smallest specimens of Protothaca staminea, a venerid bivalve. Crabs opened larger P. staminea by repeatedly loading the same region of the bivalve's shell with a chela; we hypothesized that this repeated loading caused fatigue of the shell material. To test whether significant fatigue damage would accumulate in the number of cycles a crab was likely to exert, live bivalves and cleaned valves were cyclically loaded in a mechanical testing machine to loads of a constant maximum amplitude of 70-100% of the bivalves' predicted static strength. Failure frequently occurred in fewer than 200 cycles. Recordings from strain gauges attached to the chelae of crabs showed that during an attack on a bivalve a crab would squeeze more than 200 times and that failure of the bivalve could occur during a force pulse which was weaker than previous force pulses. We conclude that repeated loading enables crabs to open larger bivalves than could be crushed outright; by greatly increasing the maximum size of prey vulnerability this expands the size range of molluscan prey available to crabs.

Background: The present finding describes third-stage larvae (L3) nematode (Gnathostomatidae) cysts parasitizing the intestinal serosa of the digestive tract of Sillago sihama (Forsskal, 1775) and Argyrops spinifer (Forsskal, 1775, King soldier bream) fishes collected from the Arabian Gulf. Objective: Two species of Gnathostomatidae are recorded, Gnathostoma sp and Gnathostoma binucleatum Almeyda-Artigas, 1991. The gross clinical pathology examination showed extensive damage to the host intestinal tissue, including epithelial necrosis, hemorrhaging, worm encapsulation, and the presence of live larvae encysted and adult in skeletal muscles of fishes causing lesions including mild hyperplasia of fibrous connective tissue around the parasite. The cross examination of fish intestines revealed food items containing parts of the animal body, appendages, Chela, and parts of the carapace of crustaceans. Most food items found in all months also including annelids (polychaetes) in high percentage in November Volume of food items were related to fish size. Juveniles appear to feed mainly on crustaceans and the adults mainly feed on crustaceans, molluscs, polychaetes, echinoderms, and teleosts, among other items. The summer was apparently not the season of parasite infection. The prevalence of infection with Gnathostoma binucleatum was low (6 of 57 fish), whereas the prevalence of infection with Gnathostoma sp. was 3 of 57 fish. These findings of Gnathostomatids represent new records of these parasites in Arabian Gulf fishes. More study needed to recognize on the larval stage parasite infection and their clinic pathology to provide a basic understanding of the general principles of the pathogenesis and pathology of Gnathostomiasis, and the relationship between fish length, food items and infection.

A new genus of the deep-sea pontoniine shrimps, Bathymenes gen. nov., is established for the ‘Periclimenes alcocki species group’ of the genus Periclimenes Costa, 1844. The new genus is distinguished from other genera of the Pontoniinae by a combination of characters: the posteriormost dorsal rostral tooth remote from other teeth, situated in the epigastric position, cornea usually reduced, the propodus of second pereiopods covered with fine granules, the dactylus of the major second chela being generally flanged, the ambulatory pereiopods with the dactyli being biunguiculate and telson with more than two pairs of dorsolateral spines. The genus is mainly distributed in the tropical to warm-temperate Indo-West Pacific waters at depths greater than 200 m. Fifteen species previously recognized as belonging to the ‘P. a lcocki species group’ are now placed in Bathymenes gen. nov. A key for their identification and a checklist of congeneric species are provided.

A new species of crayfish, Cambarus (Lacunicambarus) erythrodactylus, is separated from the Cambarus (L.) diogenes complex. The new species is morphologically similar to C. (L.) diogenes but differs from it in the presence of three or four spines along the cervical groove, greatest depth anterior mid-horizontal beneath the antennal scale, the presence of two rows of tubercles along the distal medial palm, with an additional two or three partial or full rows of tubercles on the palm, subpalm of the chela with one to four (mode = three) tubercles, and a gonopod extending greater than 90° and bent cephalodistally 20° at the shoulder. The species occurs in the Pea, Choctawhatchee, Sepulga, and Conecuh River systems of southeastern Alabama, in the Black Warrior and Tombigbee River systems in western Alabama and eastern Mississippi, in the Alabama River in central Alabama, and Bear Creek drainage of the Tennessee River, and Yazoo River drainages and occurring throughout the central and eastern portions...

Shield length-weight relationship (LWR) and relative growth were studied in three tropical hermit crab species, Diogenes moosai Rahayu & Forest, 1995, Diogenes lopochir Morgan, 1989, and Clibanarius infraspinatus (Hilgendorf, 1869). Overall, the length exponent (b) for LWR ranged between 2.67 to 3.28 with males of both Diogenes species showing positive allometry () and females showing negative allometry (), whereas that of both sexes of C. infraspinatus showed negative allometry. Males had larger b values than females in all species, indicating that males are heavier than females of equal shield length. In all species, relative growth of cheliped and chela exhibited positive allometry () with distinct sexual dimorphism whereby males bear longer chelipeds and chelae compared to females of equal shield lengths. Intra- and interspecific variations in growth of body and cheliped among the three sympatric hermit crab species allow for the resource partitioning of their vital shell resources.

A new iurid species, Protoiurus kumlutasi sp. nov. is described from the Hidirellez Cave, located in the coastal southwestern Antalya Province, Turkey. This species was collected both inside and at the entrance of the cave, and does not exhibit any troglomorphic characteristics. Its closest relative is P. kraepelini , which shares the distinctive shape of pedipalp chela in mature males. The new species can be distinguished from P. kraepelini , however, by its hemispermatophore, which conforms to subtype 1a . Additional hemispermatophores were analyzed from several specimens of P. kraepelini collected in close proximity to its type locality, further endorsing existence of unique subtype 1b in this species. The description of the new species brings the number of species in the genus Protoiurus to six.

A new species of symbiotic palaemonid shrimp, Periclimenaeus mcmichaeli sp. nov., is described based on a single male specimen collected near Dry Tortugas, Florida, in the southeastern Gulf of Mexico. This new species, the 14th now known for the genus Periclimenaeus Borradaile 1915 from the western Atlantic, is morphologically most similar to P. wilsoni (Hay, 1917), from which it can be separated by the presence in the new species of two small subdistal teeth on the ventral margin of the rostrum, absence of small spinules or tubercles on ventral margin of the meri of the major and minor chelipeds, presence of three teeth on the cutting edge of the dactylus of the minor chela, and position of dorsal spines on the telson. The presence in this new species of a prominent acute projection on each pleurae of the third and fourth somite is documented, and appears to be a character previously overlooked in the taxonomic literature of species of the genus. This new species is compared with other similar congeners from the western Atlantic as well as other oceanic regions. An updated diagnosis for P. wilsoni, and a key to identify the western Atlantic species of the genus, are also presented.

The Erymidae Van Straelen, 1925 had a worldwide distribution during the Jurassic and the Cretaceous. Twenty-seven species among four genera were reported in the Late Cretaceous, but confusions in diagnoses have led to wrong generic identifications of many erymid species. In the light of recent clarifications of the diagnoses of erymid genera, the Late Cretaceous species are here reviewed. We recognize thirteen of them including three European species which benefit of new descriptions: Palaeastacus sussexiensis (Mantell, 1824), Enoploclytia leachi (Mantell, 1822) and Enoploclytia seitzi Glaessner, 1932. Furthermore, a comparison of the Late Cretaceous erymid fauna with that from the Early Cretaceous emphasizes some changes. A decrease in diversity on genus and species level is noted with the absence of Eryma Meyer, 1840 in the Late Cretaceous and the predominance of Enoploclytia M’Coy, 1849 (including almost half of the species). Despite the scarcity of the fossil record, our palaeobiogeographic interpretations led us to propose hypotheses about the provenance of North American populations in the end of Early Cretaceous and in Late Cretaceous: (1) their supposed absence since the Callovian (Jurassic) is due to collecting and/or reporting bias or (2) they were the result of migrations of European populations. Moreover, the report of a chela assigned to Stenodactylina cf. armata (Secretan, 1964) in France confirms the existence of migration routes between European and Malagasy faunas during the Late Cretaceous.

Chaneke fogoso gen. nov. et sp. nov., are described based on specimens collected near the coast in southeastern Guerrero, Mexico. The genus is characterized by the peculiar rhomboidal shape of the subaculear tubercle, and the lack of at least one trichobothrium on the femur, patella and chela of the pedipalp, which make it the second known buthid genus with decreasing neobothriotaxy on those three pedipalpal segments, together with Alayotityus Armas 1973. Tityopsis aliciae Armas & Martin-Frias 1998, from Oaxaca, Mexico, is transferred to the new genus, resulting in Chaneke aliciae (Armas & Martin-Frias 1998), comb. nov. A cladistic analysis including all other New World “microbuthids” with decreasing neobothriotaxy, with 30 morphological characters, indicates that Chaneke is monophyletic, clearly distinct from Alayotityus Armas 1973 (from eastern Cuba) and Tityopsis Armas 1974 (from western Cuba).

We describe Synalpheus jejuensis n. sp. on the basis of 17 specimens collected around Jejudo Island, Korea. The new species is most similar to S. tumidomanus but can be distinguished from that species by shorter scaphocerite, upturned blunt tubercle rather than an acute spine on the superior margin of major chela, and teeth on the ventral margin of the pleura. The DNA barcoding using the mitochondrial cytochrome c oxidase subunit I (COI) gene fragment was employed in these two species. The intraspecific sequence divergence of the COI gene of S. jejuensis n. sp. ranges between 0% and 2.1%, while that of S. tumidomanus ranges between 0.2% and 0.4%. The sequence divergence between two species is 20.1%. DNA barcoding results provide further evidence that these two species are distinct. The discovery of S. jejuensis n. sp. is biogeographically important because the species diversity of Synalpheus is low in temperate region.

To understand the role of the eyestalk neurosecretory system in regulation of larval morphogenesis, we performed eyestalk ablation on swimming crab Portunus trituberculatus lar- vae at various times during zoeal development. We measured the length of the chelae and pleopods, which become enlarged during development, and the dorsal spine and telson furcae, which are resorbed during metamorphosis in the final (fourth) stage zoeae and subsequent larval stages, including a supernumerary fifth stage zoeae and megalopae (fifth-instar larvae). The length of the chela and pleopod of fourth stage zoeae decreased when the bilateral eyestalks were ablated earlier during development. Eyestalk ablation had little effect on the zoeal dorsal spine and furcae. In fifth-instar larvae, the effects of eyestalk ablation changed radically depending on the time when the ablation was performed, and a critical period during the premoult of the third zoeal stage was identified. Ablation before this period caused retention of a large dorsal spine and furcae and resulted in moult to the supernumerary fifth zoeal stage. Ablation after this period allowed larvae to metamorphose into normal megalopae. Ablation during this period resulted in megalopae with immature morphology, whereby the larvae retained small dorsal spines and tel- son furcae. The results demonstrated that the eyestalk neurosecretory system most likely regu- lates larval morphogenesis during metamorphosis in 2 ways: the morphogenesis of body parts that are enlarged are continuously controlled throughout the zoeal stages, whereas the resorption of body parts is controlled instantaneously at a critical point during the premoult of the third zoeal stage.