Large Claw Research Articles

Disparate occurrences of a chalicotheriine and a schizotheriine chalicothere (Mammalia, Chalicotheriidae) at the Late Miocene hominid locality Hammerschmiede (Germany)

Chalicotheres are enigmatic perissodactyls that had large claws instead of hooves. The present study concerns the material of Chalicotheriidae from the Late Miocene hominid locality of Hammerschmiede in Germany. The HAM 5 fossil site (11.62 Ma) consists of six isolated dental and postcranial chalicothere elements. Based on the morphology and dimensions of the dentition, the material can be assigned to the chalicotheriine Anisodon sp. This genus is the most common representative of Chalicotheriidae in Central Europe during the Middle Miocene but becomes much rarer during the Late Miocene. The HAM 4 fossil site (11.44 Ma) has yielded a patella belonging to a schizotheriine and a skull fragment that could possibly also belong to a schizotheriine. Thus, the schizotheriine and the chalicotheriine occur in different horizons in Hammerschmiede. Both taxa probably had a rather similar diet but different locomotion, and their disparate occurrences are most plausibly associated with environmental differences among the two fossiliferous levels.

Two new species of Strandesia Stuhlmann, 1888 (Crustacea: Ostracoda) from Thailand, with first record of a male S. martensi Savatenalinton, 2015

Two new species of Strandesia Stuhlmann, 1888 are described from the northeastern part of Thailand: S. karanovicae sp. nov. and S. amnatcharoenensis sp. nov. Strandesia karanovicae is characterized by a tumid carapace in dorsal view, a small anterior overlap, the absence of a dorso-subapical seta on the first segment of the antennule (A1), a large aesthetasc Y on the antenna, an α seta shape with a needle-like tip and a large β seta on the mandibular palp (Md-palp), serrated bristles on the maxilla, a long h1 seta on the second thoracopod (T2) and a slender caudal ramus (CR). Strandesia amnatcharoenensis has a small compressed posterior part of the right valves (RV) which makes it closely related to S. pholpunthini Savatenalinton, 2015. The new species can be distinguished primarily by a considerably small anterior overlap of the left valve over the right valve (RV), a postero-ventral flange of the RV, a remarkably large claw Ga of the CR and the chaetotaxy of the limbs, especially A1, Md-palp and T2. In addition, in the present study, the sexual population of S. martensi Savatenalinton, 2015 is recorded for the first time, and thus the first description of the male is provided here. Moreover, the morphological examination of both males and females revealed differences between asexual and sexual females and also points to the fact that S. martensi is a mixed reproduction species. This is the first record of the mixed reproductive mode in the genus Strandesia or even in the Cypricercinae.

Human disturbance affects behavioural time allocation in a fiddler crab (<em>Austruca annulipes</em>) in Southern Thailand

Human disturbances affect the macroinvertebrate populations in coastal regions. They respond to disturbances by altering their density and behaviour. Therefore, many of them are used as bioindicator species of human disturbance. Here, we pioneer the use of fiddler crabs to examine whether they alter their behaviour under human disturbance. Male fiddler crabs possess one large claw used for courting (waving) and fighting, and one small feeding claw, whereas females have two feeding claws. They show several surface activities. This study investigates (1) the effects of human disturbance on density and sex-ratio, and (2) the effects of human disturbance, and sex on behavioural time allocations in Austruca annulipes. Their density, sex-ratio, and time allocations were investigated in human-disturbed area (DA) and nondisturbed area (NDA). They showed feeding, feeding and walking, walking, running, standing/vigilance, inside burrows, burrowing, grooming, fighting, and waving. The results showed that crab density was higher and the sex ratio was more male biased in NDA than in DA. Human disturbance and sex affected time allocations but their interaction had no effect. Crabs in DA spent more time running, standing, and inside burrows but less time walking, burrowing, fighting, and waving than crabs in NDA. Between sexes, males spent more time standing, burrowing, grooming, and fighting but less time feeding, and walking than females. This indicates that human disturbances force the crabs to spend more time on anti-predator and escape behavior (standing/vigilance, running, inside burrows) rather than courting (waving) and constructing burrows (mating/breeding sites), which are important for breeding.

New evidence for the unique coexistence of two subfamilies of clawed perissodactyls (Mammalia, Chalicotheriidae) in the Upper Miocene of Romania and the Eastern Mediterranean

Chalicotheres are a peculiar group of large herbivorous mammals, closely related to extant tapirs, rhinoceroses, and horses, but with large claws instead of hooves. The family Chalicotheriidae consists of two subfamilies, the Schizotheriinae and the Chalicotheriinae. Herein we present chalicothere remains from the Upper Miocene locality of Pogana 1 in Romania, identifying the schizotheriine Ancylotherium pentelicum and an indeterminate chalicotheriine that were both found in the same stratigraphic layer. Thus, the Pogana 1 locality represents one of the very few confirmed cases of the co-occurrence of the two subfamilies within one fossiliferous horizon in the same fossil site. A detailed review of all localities where the two subfamilies have been reported to co-occur shows that this is a rare phenomenon that is almost exclusively observed in the Turolian of the Balkan-Iranian zoogeographical province. This is probably due to provincial differences in the palaeoenvironment. The data presented here support the hypothesis of a diverse mosaic environment in the Balkan-Iranian province with both closed environments and open habitats that was able to sustain a rich and diverse large mammal fauna.

Length of a sexually selected ornament-armament in fiddler crabs (Decapoda: Brachyura: Ocypodidae): One way, over deep time and space

Abstract Using three data sources, we measured claw lengths of the extremely large major claws of 70 species of fiddler crabs, spread over four major biogeographic regions and all 11 genera, as a function of carapace length. Despite a diversity of biogeography, body size, type of sexual signaling and mating behavior, and details of claw morphology, all species groupings follow the same linear relationship. No subgroupings could be determined, by region, among diverse genera, by ancestral-derived status, or by data source. Major claw size is known to be implicated in female selection of mates, which might be expected to diversify claw lengths among species and genera, as might differences in combat might be expected to diversify claw length, as it does in other claw traits. The constancy suggests a possible functional constraint on major claw length across the fiddler crabs, which is to be determined. Efficient folding of the claw as the male rapidly retreats into a burrow, or a protection of the carapace from frontal attack by predators or combatants in an initial aggressive encounter might select for this pervasive relationship. Tests are suggested. The sexually selected major claw is more variable than the naturally selected minor claw, but this difference in variability could be attributed partially to regeneration of the major cheliped and even variation in shape. A surprising similar trend of closing force index for the major claw exists for a large number of species spread throughout the genera and major regions occupied by fiddler crabs, but a considerable variation exists in a variety of functional traits. Thus, the constancy of length relationship stands out distinctly from a considerable background variation in form. As a sexually selected trait, the claw length constancy begs for an explanation.

Distinguishing between unreliability and dishonesty: A comparative study of aggressive communication in crayfish

Abstract A major challenge in the study of animal communication is distinguishing whether signals convey honest or dishonest information. Biologists infer the honesty of a signal from its correlation with the information being signalled (e.g. fecundity or fighting ability)—the better the correlation, the more honest the signal. However, this view of signalling potentially conflates unreliable indicators with dishonest signals. Just because a trait conveys unreliable information does not mean that the structure serves as a dishonest signal; developmental noise, genetic drift and environmental constraints can reduce the covariation between a putative signal and an organism's quality. Moreover, a trait must influence the behaviour of other organisms to qualify as a signal. We studied how a putative signal, claw size, affects physical performance and social dominance in three species of stream‐dwelling crayfish, which fight routinely over resources. For comparison, we measured the relationship between claw size and claw strength in three species of burrowing crayfish, which do not fight. In all species, crayfish with larger claws were not necessarily stronger, indicating that claw size poorly indicates claw strength. However, claw size is unlikely to function as a dishonest signal of fighting ability in these species for two reasons. First, claw size unreliably indicates claw strength in both the stream‐dwelling species and the burrowing species. Second, relative claw size poorly predicted whether stream‐dwelling crayfish would escalate aggression, questioning whether claw size serves as a signal. Instead, stream‐dwelling crayfish escalated aggression based on their relative body size. Our results highlight the importance of observing behaviour when determining the honesty of a signal. As such, future studies must distinguish between phenotypes that are unreliable indicators (or reliable indicators) from phenotypes that have been selected for dishonest (or honest) signalling. A free Plain Language Summary can be found within the Supporting Information of this article.

Social interaction in males of the Amazon river prawn Macrobrachium amazonicum (Heller, 1862) (Decapoda, Palaemonidae)

Abstract The large size variation of Macrobrachium amazonicum reflects a complex population structure that consists of four morphotypes, called TC (Translucent Claw), CC (Cinnamon Claw), GC1 (Green Claw 1), and GC2 (Green Claw 2). The effect of the largest morphotype (GC2) claws on development and behaviour of the smallest male morphotype (TC) was analysed through manipulations of the large prawn’s second pair of claws. TC males were paired for 75 days in aquaria with (a) an intact GC2, (b) a GC2 with immobilized dactyls, and (c) a GC2 without chelipeds. Isolated TC males served as a control. The maintenance activities of TC males and social interactions with the GC2 morphotype were monitored. Survival and growth of TC males was lower in relation to the control when they were paired with intact GC2 males. Aggressive interactions were carried out almost exclusively by GC2 and strongly affected the behaviour of the small prawns. The absence of chelipeds and immobilization of dactyls in GC2 prawns reduced the negative effect on the development of TC males and agonistic behaviour. The social interactions between GC2 and TC prawns reflect a stable dominance hierarchy. The large claw of the GC2 morphotype plays a major role in the social interaction.

The combined effects of ocean acidification and warming on a habitat-forming shell-crushing predatory crab

In mid rocky intertidal habitats the mussel Perumytilus purpurarus monopolizes the substratum to the detriment of many other species. However, the consumption of mussels by the shell-crushing crab Acanthocyclus hassleri creates within the mussel beds space and habitat for several other species. This crab uses its disproportionately large claw to crush its shelled prey and plays an important role in maintaining species biodiversity. This study evaluated the consequences of projected near-future ocean acidification (OA) and warming (OW) on traits of A. hassleri linked with their predatory performance. Individual A. hassleri were maintained for 10–16 weeks under contrasting pCO2 (~500 and 1400 μatm) and temperature (~15 and 20 °C) levels. We compared traits at the organismal (oxygen consumption rate, survival, calcification rate, feeding rates, crusher claw pinching strength, self-righting speed, sarcomere length of the crusher claw muscles) and cellular (nutritional status ATP provisioning capacity through citrate synthase activity, expression of HSP70) level. Survival, calcification rate and sarcomere length were not affected by OA and OW. However, OW increased significantly feeding and oxygen consumption. Pinching strength was reduced by OA; meanwhile self-righting was increased by OA and OW. At 20 °C, carbohydrate content was reduced significantly by OA. Regardless of temperature, a significant reduction in energy reserves in terms of protein content by OA was found. The ATP provisioning capacity was significantly affected by the interaction between temperature and pCO2 and was highest at 15 °C and present day pCO2 levels. The HSP70 levels of crabs exposed to OW were higher than in the control crabs. We conclude that OA and OW might affect the amount and size of prey consumed by this crab. Therefore, by reducing the crab feeding performance these stressors might pose limits on their role in generating microhabitat for other rocky intertidal species inhabiting within mussel beds.

Harder, better, faster, stronger: Weapon size is more sexually dimorphic than weapon biomechanical components in two freshwater anomuran species.

Sexual selection influences the evolution of morphological traits that increase the likelihood of monopolizing scarce resources. When such traits are used during contests, they are termed weapons. Given that resources are typically linked to monopolizing mating partners, theory expects only males to bear weapons. In some species, however, females also bear weapons, although typically smaller than male weapons. Understanding why females bear smaller weapons can thus help us understand the selective pressures behind weapon evolution. However, most of our knowledge comes from studies on weapon size, while the biomechanics of weapons, such as the size of the muscles, efficiency, and shape are seldom studied. Our goal was to test if the theoretical expectations for weapon size sexual dimorphism also occur for weapon biomechanics using two aeglid crab species. Males of both species had larger claws which were also stronger than female claws. Male claws were also more efficient than females' claws (although we used only one species in this analysis). For weapon shape, though, only one species differed in the mean claw shape. Regarding scaling differences, in both species, male claws had higher size scaling than females, while only one species had a higher shape scaling. However, male weapons did not have higher scaling regarding strength and efficiency than females. Thus, males apparently allocate more resources in weapons than females, but once allocated, muscle and efficiency follow a similar developmental pathway in both sexes. Taken together, our results show that sexual dimorphism in weapons involves more than differences in size. Shape differences are especially intriguing because we cannot fully understand its causes. Yet, we highlight that such subtle differences can only be detected by measuring and analysing weapon shape and biomechanical components. Only then we might better understand how weapons are forged.

Marine protected areas rescue a sexually selected trait in European lobster.

Marine protected areas (MPAs) are increasingly implemented worldwide to maintain and restore depleted populations. However, despite our knowledge on the myriad of positive responses to protection, there are few empirical studies on the ability to conserve species’ mating patterns and secondary sexual traits. In male European lobsters (Homarus gammarus), the size of claws relative to body size correlates positively with male mating success and is presumably under sexual selection. At the same time, an intensive trap fishery exerts selection against large claws in males. MPAs could therefore be expected to resolve these conflicting selective pressures and preserve males with large claws. We explored this hypothesis by contrasting claw size of males and females in three pairs of MPAs and nearby fished areas in southern Norway. By finding that male lobsters have up to 8% larger claws inside MPAs compared to similarly sized males in fished areas, our study provides evidence that MPAs rescue a secondary sexual trait. Recovery from harvest selection acting on claws is the most likely explanation; however, the higher abundance of lobster inside MPAs does not rule out a plastic response on claw size due to increased competition. Regardless of the underlying cause, our study demonstrates (a) the value of protected areas as a management tool for mitigating fisheries‐induced evolution and (b) that MPAs help maintaining the scope for sexual selection in populations with vulnerable life histories and complex mating system.

Virile crayfish escalate aggression according to body size instead of weapon size

Many crustaceans use their large claws to signal fighting ability during territorial contests. However, the size of a claw does not always reflect its strength or the bearer's ability to fight. If strength predicts the outcome of a fight, the mismatch between the size and strength of a claw creates dishonest signalling. Still, only a handful of species have been studied, leaving a gap in our knowledge of the taxonomic diversity and evolutionary history of dishonest signalling. To help fill this gap, we studied signalling and fighting between virile crayfish, Faxonius virilis. First, we measured the relationship between the size and strength of a claw in males and females. Then, we staged encounters between members of the same sex to determine how carapace length, claw size and claw strength influence the probability of fighting and the probability of winning. Both males and females possessed claws whose size poorly predicted their strength, especially at larger sizes. Unlike other species, which escalate aggression based on claw size, virile crayfish escalated aggression based on relative body size. When fighting occurred, however, both body size and claw strength determined the winner. Likely, virile crayfish ignore claw size because body size provides a more reliable signal of dominance. Our results stress the importance of observing behavioural dynamics in addition to functional relationships when studying the potential for dishonest signalling.

Continuously choosy males and seasonally faithful females: sex and season differences underlie size-assortative pairing

In monogamous mating systems, pair mates frequently share similar characteristics, such as size or ornamentation, a pattern suggesting mutual mate choice. When pairs persist across multiple seasons, preferences for familiar pair mates can either reinforce or disrupt patterns of assortative pairing. Snapping shrimp (Alpheus angulosus) are socially monogamous shrimp that can be found in size-assortative pairs year-round; both sexes could benefit from pairing with larger individuals. To determine the role of pair mate preferences for either size or established pair mates in size-assortative pairing, we performed simultaneous choice trials to test whether (1) either or both sexes prefer larger pair mates, (2) females prefer males with larger claws, or (3) either or both sexes prefer current pair mates over size-matched unfamiliar potential mates. Males, but not females, preferred larger potential pair mates in both the reproductive and nonreproductive seasons; males also showed more mate-searching behaviour, switching more frequently between choice options than females. Females, but not males, preferred their current pair mate over a novel potential pair mate; females also engaged in more frequent switching between pair mates and novel males, but only during the nonreproductive season. Thus, while both males and females exhibit preferences in pairing, size-assortative pairing in snapping shrimp does not result from mutual mate choice for size, but rather preferences for size in one sex, with size-assortative pairing reinforced by preferences for established pair mates in the other. Furthermore, pairing behaviour may be dynamic, shifting across seasons even in a year-round socially monogamous species.

The oldest freshwater crabs: claws on dinosaur bones

With approximately 1,500 extant species, freshwater crabs (Decapoda: Brachyura) are among the most diverse decapod crustaceans. Nevertheless, their fossil record is extremely limited: only Potamidae, Potamonautidae and Trichodactylidae are reported up to the Eocene of the Neotropics so far. This work documents unusually large decapod claws from the Upper Cretaceous (Campanian) continental deposits of Velaux and vicinity (southern France), in close association with large vertebrate remains. In addition to (1) the systematic assignment of these claws, the study addresses (2) the salinity trends in the deposit environment from its faunal assemblage and the elementary chemical patterns of fossils, and (3) the likely scenario for their auto/allochthony in the Velaux fluvial system. These claws belong to a new taxon, Dinocarcinus velauciensis n. gen. n. sp., referred to as Portunoidea sensu lato, a group of “true” crabs nowadays linked to marine systems. However, the faunal assemblage, the claw taphonomy and the carbonates Y/Ho signatures support their ancient freshwater/terrestrial ecology, making them the oldest reported continental brachyurans and extending the presence of crabs in freshwater environments by 40 Ma. Either as primary or as secondary freshwater crabs, the occurrence of these portunoids in Velaux is an evidence for the independent colonizations of continental environments by multiple brachyuran clades over time, as early as the Campanian.

Frequency and latency of autotomy of a sexually selected fiddler crab appendage

Autotomy is a predator defence mechanism by which individuals voluntarily release an appendage to escape a predator or escape a fouled moult. The decision to autotomize is driven by the costs of autotomy (i.e., the loss of the appendage) vs. the risk of predation. In many cases, autotomized appendages have few alternative functions, yet male fiddler crabs autotomize the sexually selected large claw that is critical for mate attraction. We conducted an experiment with Austruca mjoebergi to understand the role of claw autotomy by males during the mating season. Males more readily autotomized a leg relative to the enlarged claw, reflecting the much greater cost of being without the major claw. Larger crabs had a lower probability of claw autotomy than did small crabs, reflecting the greater fitness cost of claw autotomy experienced by larger crabs. The sexually selected fiddler crab claw is a multifunction structure with benefits that may outweigh the survival probability resulting from autotomy when individuals are threatened by predation.

Sexual dimorphism in the claws of the European terrapin (<em>Emys orbicularis</em>): potential implications for the reproductive fitness of the species.

There are many biometric differences between the males and females of the European pond turtle (Emys orbicularis) as regards their size, colouring, the shape of the plastron, tail, etc. The males use their claws to grasp the female during copulation and hence sexual selection should favour the males that have larger claws, which allow them to grasp the female better. Here, we address this type of sexual dimorphism in a comparative analysis of indices obtained from claw length, the length of the carapace and the locality where individuals were sampled. The results show that the curvature of the claws differs between the two sexes, being longer in males and increasing with age, size, and hence, the state of sexual maturity, than in females. Greater claw length could confer advantages for males when grasping the carapace of females, and hence, improve their reproductive fitness. Importance in the reproductive success that might have this feature in males could originate future studies that will relate the shape, thickness, length and other measures of the claws in males with their reproductive success in different populations, genetic variety, and most importantly, viability of populations.

It takes two: Seasonal variation in sexually dimorphic weaponry results from divergent changes in males and females.

Sexually dimorphic weaponry often results from intrasexual selection, and weapon size can vary seasonally when costs of bearing the weapon exceed the benefits outside of the reproductive season. Weapons can also be favored in competition over nonreproductive resources such as food or shelter, and if such nonreproductive competition occurs year‐round, weapons may be less likely to vary seasonally. In snapping shrimp (Alpheus angulosus), both sexes have an enlarged snapping claw (a potentially deadly weapon), and males of many species have larger claws than females, although females are more aggressive. This contrasting sexual dimorphism (larger weaponry in males, higher aggression in females) raises the question of whether weaponry and aggression are favored by the same mechanisms in males and females. We used field data to determine whether either sex shows seasonal variation in claw size such as described above. We found sexual dimorphism increased during the reproductive season due to opposing changes in both male and female claw size. Males had larger claws during the reproductive season than during the nonreproductive season, a pattern consistent with sexual selection. Females, however, had larger claws during the nonreproductive season than during the reproductive season—a previously unknown pattern of variation in weapon size. The observed changes in female weapon size suggest a trade‐off between claw growth and reproduction in the reproductive season, with investment in claw growth primarily in the nonreproductive season. Sexually dimorphic weaponry in snapping shrimp, then, varies seasonally due to sex differences in seasonal patterns of investment in claw growth, suggesting claws may be advantageous for both sexes but in different contexts. Thus, understanding sexual dimorphisms through the lens of one sex yields an incomplete understanding of the factors favoring their evolution.

The importance of strength and stamina varies with ownership status in sand fiddler crab contests for breeding burrows

In sand fiddler crabs, Uca pugilator, contests between residents and intruders for breeding burrows often escalate to forceful pinching. In these contests, we found that winners had greater claw armature, greater claw pinching strength, and greater pinching stamina (the ability to persist in pinching at a strength close to the initial level). Winners were not superior to opponents in body size, claw length, or pinching resilience (the ability to quickly return to former pinching strength and stamina). There was also a strong resident advantage such that residents usually won when strength and claw armature were similar among contestants. A field experiment that controlled pinching strength and stamina revealed that (1) residents readily retreat into their burrows when challenged by a male of relatively high pinching strength and (2) only intruders with high stamina win contests in which residents retreat. Contests with burrow retreats are twice as long as other contests, suggesting that high stamina enables intruders to persist in engaging residents. Intruders who lost experimental contests were more likely to immediately engage another resident if they were of high resilience. The ability to engage in multiple contests in short periods of time could prove favorable to residents and may explain their relatively high resilience. This study indicates that strength is a component of RHP and that residents, by retreating into burrows, can force upon intruders the additional requirement of high stamina before they can usurp burrow ownership. Strength and stamina have long been associated with victory in contests between males for breeding territories. However, territory owners may utilize features of their territories to gain an advantage over rivals who possess greater fighting ability. In sand fiddler crabs, Uca pugilator Bosc, males with larger claws usually win contests for breeding burrows but there is an ownership advantage. We show that greater strength (revealed in claw pinching force) leads to victory for burrow owners but that among intruders it only leads to an additional requirement for victory, the display of stamina (revealed in the ability to persist in forceful pinching). This is because weaker owners take refuge in burrows, forcing intruders into lengthy contests. Thus, the ownership advantage derives from the need of owners to display strength but of intruders to display strength and stamina.

Individual Morphology and Habitat Structure Alter Social Interactions in a Range-Shifting Species

Ecosystem engineers that serve as foundation species shape the ecology and behavior of the species which depend on them. As species shift their geographic ranges into ecosystems they have not previously inhabited, it is important to understand how interactions with novel foundation species alter their behavior. By employing behavioral assays and morphological analyses, we examined how individual morphology and foundation species structure impact the ritualistic aggression behavior of the range shifting mangrove tree crab Aratus pisonii between its historic and colonized habitats. Structure of the foundation species of the colonized salt marsh ecosystem increases the incidence and risk of this behavior over the historic mangrove habitat, potentially negating benefits of ritualizing aggression. Further, docks within the salt marsh, which are structurally analogous to mangroves, mitigate some, but not all, of the increased costs of performing ritualized aggression. Crabs in the salt marsh also had relatively larger claws than conspecifics from the dock and mangrove habitats, which has implications for the risk and outcomes of ritualized interactions. These changes to morphology and behavior highlight the impacts that foundation species structure can have on the morphology, ecology, and behavior of organisms and the importance of studying these impacts in range shifting species.

Color changes of fiddler crab between seasons and under stressful conditions: Patterns of changes in lightness differ between carapace and claw

In animals, coloration on the body surface could have various functions, such as thermoregulation, camouflage, and intraspecific communication. Because individuals often experience different ecological and social contexts/environments, changes of coloration due to these contexts/environments would be adaptive. The functions of coloration, in addition, may differ between different body regions. In this study, I compared the changes in coloration (lightness) between the carapace and the large claw of male fiddler crabs, Austruca lactea, to estimate the function of coloration in each body part in this species. I conducted monthly field surveys to assess seasonal changes of coloration of the crabs' carapace and large claw. I also carried out a field experiment to determine short-term changes in coloration under stressful conditions. Monthly surveys revealed that claw color was always lighter than the carapace color. Both of these were lightest during the breeding period. Interestingly, carapace lightness positively correlated with carapace width in the peak of the breeding season (July), while it was negatively correlated with carapace width in the non-breeding season (May and September). Claw lightness also differed significantly between months, although claw lightness was less variable than carapace lightness. In the field experiment, carapace coloration rapidly (within ten minutes) became darker under stressful conditions, but claw coloration changed very little, even after crabs were exposed to stressful conditions for 30 min. These results suggest that the function of coloration differs between carapace and claw. Carapace coloration may have functions related to thermoregulation and/or camouflage, and may therefore rapidly respond to fluctuating contexts/environments. Carapace coloration may also have a nuptial function for courtship that is related to body size. Claw coloration could be used to convey relatively more stable information, and may play a role in species recognition for mate choice, and resource holding potential for territorial fighting. Multiple factors, including physical and social factors, may affect each other, and consequently influence coloration of each body part in this species.

Parapygmephorus crossi (Acari, Heterostigmata, Neopygmephoridae), a mite species new to fauna of Iran

There are 21 genera in the family Neopygmephoridae (Acari: Heterostigmata: Pygmephoroidea) (Khaustov and Mandelshtam 2017) in which many of them are associated with various arthropods including Chilopods, spiders, bees, ants, beetles and termites (Khaustov 2017). One of the neopygmephorid genera is Parapygmephorus encompassing eight species, associated with bees of the families Halictidae, Apidae, Colletidae and Megachilidae, and in one case on a spider wasp, Pompilidae (Fan et al . 2014). These phoretic mites feed on fungi in the nests of their bee hosts and are clinging them by a large and strong single claw on their first tibiotarsus (Cross 1965). During a sampling of bees and their associate mites in Iran, the mite Parapygmephorus crossi Mahunka, 1974 (Figures 1A and 1B) recovered from Halictus ( Halictus ) resurgens Nurse, 1903 (Halictidae) (Figure 1C and 1D) in city park (Park Jangali) close to Yasouj, capital of Kohgiluyeh and Boyer Ahmad province (Southwestern Iran) on 7 Septamber 2014. Twelve specimens of phoretic mites were found attaching to body hairs of a bee host. The materials are deposited in the Acarological Collection, Department of Entomology, Faculty of Agriculture, Tarbiat Modares University, Tehran, Iran. Mite Parapygmephorus crossi was collected and described for the first time on Halictus holtzi (Schultz) from Afghanistan (Mahunka 1974) characterized by setae ps 1 longer than ps 2 and setae ps 3 distinctly shorter than ps 2 . So, it is first record of this species in Iran and second record in the world including Palaearctic. Previously, three other species of the Parapygmephorus were collected from Iran: P . khorasanicus Hajiqanbar and Khaustov, 2011 on Halictus quadricinctus (Fabricius); P . delyorum Mahunka, 1980 on an unidentified halictid bee; and P . magnisetosus Khaustov and Zaloznaya, 2011 on Amigella sp. and Eucera sp. (Apidae), Halictus spp. and Lasioglossum sp. (Halictidae), and Lithurgus chrysurus Fonscolombe, 1834 (Megachilidae) (Hajiqanbar et al. 2011a; Hajiqanbar et al. 2011b; Hajiqanbar and Rakhshani 2011; Loghmani et al . 2014; Sobhi et al . 2017).