Juvenile Morphology Research Articles

The effect of rearing temperature in larval development of pejerrey, Odontesthes bonariensis: morphological indicators of development

It is well known that in pejerrey water temperature not only affects growth rates but also directs the sexual differentiation process. This fact rise the question of how different the development of pejerrey larvae of the same age is when reared at different temperatures. A description of developmental stages for the embryonic and larval periods of the pejerrey, Odontesthes bonariensis, and the influence of rearing temperature on larval development are presented. Then, larval development was studied at three rearing temperatures, and changes in general morphology, fin morphology, and caudal fin structure have been taken into consideration within the thermal range involved in the temperature sex determination of this species. Fin fold reabsorption, caudal fin formation, and body shape were selected to follow the events leading to the acquisition of the juvenile morphology. The juvenile phenotype was defined when the fin fold was reabsorpted and the caudal fin acquired its definitive homocercal structure. The moment at which the juvenile phenotype was achieved, was evaluated in relation to larval age, size and, shape. The size resulted as the best indicator of development in pejerrey.

Scrutinising snail shells

Scrutinising snail shells

Early juvenile development of Mediterranean Liocarcinus depurator (Crustacea: Decapoda: Brachyura: Portunidae)

The early juvenile crab stages (C1 to C5) of the portunid crab Liocarcinus depurator (Linnaeus, 1758) were obtained in the laboratory from megalopae captured from the plankton in the northwest Mediterranean. Morphological development through these stages is described and compared with previous juvenile descriptions and adult morphology. The definitive adult morphology of carapace teeth is only apparent from stage C4. The incision on the lower orbital margin of the carapace and the mesial lobe (“portunid lobe”) of the endopod of the first maxilliped starts to be evident from C3. Stage C5 is already very similar to that of the typical adult crab. Male and female crabs can be distinguished from stage C2 onwards, based on sexual dimorphism in pleopods. The morphology and size of Mediterranean juvenile crabs was compared with the previous description of individuals reared in the laboratory from ovigerous females from British North Atlantic waters.

Cranial Ontogeny in Stegoceras validum (Dinosauria: Pachycephalosauria): A Quantitative Model of Pachycephalosaur Dome Growth and Variation

Historically, studies of pachycephalosaurs have recognized plesiomorphically flat-headed taxa and apomorphically domed taxa. More recently, it has been suggested that the expression of the frontoparietal dome is ontogenetic and derived from a flat-headed juvenile morphology. However, strong evidence to support this hypothesis has been lacking. Here we test this hypothesis in a large, stratigraphically constrained sample of specimens assigned to Stegoceras validum, the best known pachycephalosaur, using multiple independent lines of evidence including conserved morphology of ornamentation, landmark-based allometric analyses of frontoparietal shape, and cranial bone histology. New specimens show that the diagnostic ornamentation of the parietosquamosal bar is conserved throughout the size range of the sample, which links flat-headed specimens to domed S. validum. High-resolution CT scans of three frontoparietals reveal that vascularity decreases with size and document a pattern that is consistent with previously proposed histological changes during growth. Furthermore, aspects of dome shape and size are strongly correlated and indicative of ontogenetic growth. These results are complementary and strongly support the hypothesis that the sample represents a growth series of a single taxon. Cranial dome growth is positively allometric, proceeds from a flat-headed to a domed state, and confirms the synonymy of Ornatotholus browni as a juvenile Stegoceras. This dataset serves as the first detailed model of growth and variation in a pachycephalosaur. Flat-headed juveniles possess three characters (externally open cranial sutures, tuberculate dorsal surface texture, and open supratemporal fenestrae) that are reduced or eliminated during ontogeny. These characters also occur in putative flat-headed taxa, suggesting that they may also represent juveniles of domed taxa. However, open cranial sutures and supratemporal fenestrae are plesiomorphic within Ornithischia, and thus should be expected in the adult stage of a primitive pachycephalosaur. Additional lines of evidence will be needed to resolve the taxonomic validity of flat-headed pachycephalosaur taxa.

Comparison of Burrow Morphology of Juvenile and Young Adult Ocypode ceratophthalmus from Sai Kaew, Thailand

Burrow architecture of the ghost crab, Ocypode ceratophthalmus was studied at Sai Kaew beach (a pristine sandy habitat) in southern Thailand. The burrows of 131 individuals were cast with molten wax and carefully excavated. Only complete burrow casts with crab-occupant |$(n = 67)$| were used in the data analyses. Burrows were grouped into categories according to their shapes: J, U or Y-burrows; and further classified into those excavated by juvenile and young adult crabs based on carapace width: juvenile, Juv, (⁠|${\rm{CW}} \lt 20\;{\rm{mm}}$|⁠; |$n = 53$|⁠) and young adults, YgA (⁠|${\rm{CW}} \ge 20\;{\rm{mm}}$|⁠; |$n = 14$|⁠). All J, U and Y-burrows have an ascending arm that opens on the surface of the substrate (= Open Arm, OA). The other ascending arm of U and Y-burrows terminates a short distance from the surface of the shore (= Blind-ending Arm, BeA). Y-burrows were predominant |$(66\% )$| as compared to J and U-burrows (⁠|$13\% $| and |$21\% $| respectively). Juvenile Y-burrows had a steeper angle of descent of the OA which may provide better protection from predators through rapid retreat to deeper depths. Smaller |${{\rm{\beta }}_{{\rm{Juv}}}}$| (cf. |${{\rm{\alpha }}_{{\rm{Juv}}}}$|⁠) indicates a gentler gradient that may facilitate escape. |${{\rm{\beta }}_{{\rm{Juv}}}}$| is also not significantly different from |${{\rm{\beta }}_{{\rm{YgA}}}}$| suggesting an optimal gradient for crabs to push through the last cm or so of sand above the BeA to escape from predators. The larger |${\rm{\theta }}$| in YgA burrows could improve maneuverability down the shaft as YgA have larger body volumes than Juv. |${{\rm{\alpha }}_{{\rm{Juv}}}}$| and |${{\rm{\alpha }}_{{\rm{YgA}}}}$| of J, U and Y-burrows and |${\rm{\beta }}$| of U and Y-burrows were not significantly different. The arm depths of juvenile J, U and Y-burrows were also similar. Comparison of the relationship between arm depth and shaft depth against the total depth in Juv and YgA Y-burrows indicates that the deepening of Y-burrows occurs mainly by the lengthening of the shafts. Results from this study provide evidence that the J and U-shaped burrows could be the precursors of Y-shaped burrows in the excavation process.

Intersexual Trophic Niche Partitioning in an Ant-Eating Spider (Araneae: Zodariidae)

BackgroundDivergence in trophic niche between the sexes may function to reduce competition between the sexes (“intersexual niche partitioning hypothesis”), or may be result from differential selection among the sexes on maximizing reproductive output (“sexual selection hypothesis”). The latter may lead to higher energy demands in females driven by fecundity selection, while males invest in mate searching. We tested predictions of the two hypotheses underlying intersexual trophic niche partitioning in a natural population of spiders. Zodarion jozefienae spiders specialize on Messor barbarus ants that are polymorphic in body size and hence comprise potential trophic niches for the spider, making this system well-suited to study intersexual trophic niche partitioning.Methodology/Principal FindingsComparative analysis of trophic morphology (the chelicerae) and body size of males, females and juveniles demonstrated highly female biased SSD (Sexual Size Dimorphism) in body size, body weight, and in the size of chelicerae, the latter arising from sex-specific growth patterns in trophic morphology. In the field, female spiders actively selected ant sub-castes that were larger than the average prey size, and larger than ants captured by juveniles and males. Female fecundity was highly positively correlated with female body mass, which reflects foraging success during the adult stage. Females in laboratory experiments preferred the large ant sub-castes and displayed higher capture efficiency. In contrast, males occupied a different trophic niche and showed reduced foraging effort and reduced prey capture and feeding efficiency compared with females and juveniles.Conclusions/SignificanceOur data indicate that female-biased dimorphism in trophic morphology and body size correlate with sex-specific reproductive strategies. We propose that intersexual trophic niche partitioning is shaped primarily by fecundity selection in females, and results from sex-differences in the route to successful reproduction where females are selected to maximize energy intake and fecundity, while males switch from foraging to invest in mating effort.

Post-larval morphology, growth, and development of Uca cumulanta Crane, 1943 (Crustacea, Decapoda, Ocypodidae) under laboratory conditions

Studies on the post-larval morphology and growth of crabs can allow correct identification of their early life stages, supporting studies on phylogenetic relationships and ecological aspects. Nevertheless, little is known about the juvenile morphology of ocypodoid crabs worldwide. Uca cumulanta Crane, 1943 is a fiddler crab commonly found in the intertidal zone of the tropical and subtropical western Atlantic. This study describes the morphology of the first juvenile stage of U. cumulanta, its absolute and relative growth, and the appearance and development of its secondary sexual characters. The antennules of U. cumulanta show morphological peculiarities and could probably be used as a distinguishing feature for crabs of this genus. The maxillule and the maxilla have sets of setae forming specialised structures for sorting particles from the sediment. The absolute growth pattern differed statistically between sexes. The study of relative growth revealed differences in the relationships cheliped propodus length (CPL), cheliped propodus height (CPH), and abdomen width (AW) vs. carapace length (CL). These differences between sexes showed that males diverge from females (in the chelipeds) from 3.04±0.11 mm (VI juvenile stage), and females diverge from males (in the abdomen) from 3.84±0.13 mm (VII juvenile stage). The pleopods, rudimentary in the first stage, disappear in the second stage, and then arise in different numbers for each sex from the third juvenile stage on. The spoon-tipped setae found on the second maxilliped, which are used to sort food particles, are evident only from the fourth juvenile stage and increase linearly with carapace growth. The absence of these setae may be the reason why juveniles settle on organic-rich substrates where they can obtain food.

Differentiation of body form of Gustavioidea (Acari: Oribatida) in the light of ontogeny of three species

Differentiation of body form of Gustavioidea in the light of ontogeny of Dorycranosus curtipilis (Liacaridae), Ceratoppia sphaerica and Ceratoppia quadridentata (Peloppiidae) was investigated, and morphology of juveniles of these species was described and illustrated for the first time. The juveniles of D. curtipilis differ distinctly from those of Ceratoppia species mainly by stronger chelicerae, more elongated body, and convex gastronotum, oval cross section, small and clavate sensillus, and rather thin, and pliable setae. The protonymphs of all these species lose gastronotal setae of d-series, and these setae are absent in subsequent nymphs and adult. The adult loses further notogastral setae, such that 11 pairs remain in D. curtipilis, but only two pairs in Ceratoppia species. Diagnoses of these species are enriched with morphological characters of juveniles, and the morphology of Ceratoppia bipilis is briefly compared, as are aspects of Gustavia fusifer (Gustaviidae).

The taxonomy of Ogyris halmaturia (Tepper, 1890) stat. nov. (Lepidoptera: Lycaenidae)

Ogyris halmaturia (Tepper, 1890) was unwittingly founded on two different taxons, comprising the O. halmaturia and also O. otanes (C. & R. Felder, 1865). For the past 116 years, O. halmaturia has been treated primarily either as a geographical subspecies or as a synonym of Ogyris idmo (Hewitson, 1862). Recently in 2008, it was proposed to synonymise O. halmaturia with O. otanes, and Ogyris waterhouseri (Bethune-Baker, 1905) was elevated as the replacement name for O. halmaturia. In this paper the taxonomic status of O. halmaturia is reviewed and it is considered to be valid, while O. waterhouseri is considered to be a junior subjective synonym of O. halmaturia. Comparisons of adult and juvenile morphologies for allied species, and of DNA attributes indicate O. halmaturia is specifically distinct. The common name Eastern Large Bronze Azure is proposed for O. halmaturia.

Implications of stunting on morphology of freshwater fishes

The purpose of this study was to assess morphological differences between stunted and non-stunted white perch Morone americana and green sunfish Lepomis cyanellus. Few female M. americana were captured; thus, morphological differences between adult males and juveniles were assessed for M. americana. Similarly, few immature (juvenile) L. cyanellus were captured for the stunted morphotype; thus, male and female morphological differences were assessed for L. cyanellus. Features of the head tended to be relatively larger in stunted fish of both species, whereas the mid-body tended to be relatively larger in non-stunted M. americana, but not in non-stunted L. cyanellus. Adult and juvenile morphology overlapped considerably in non-stunted M. americana, but there was a clear distinction between adult and juvenile morphology of stunted M. americana. There was little sexual dimorphism in shape in stunted L. cyanellus, whereas sexual dimorphism was evident in non-stunted L. cyanellus. It appears that selective forces imposed by predation and food limitation may contribute to morphological diversification between stunted and non-stunted fishes.

Juvenile development of Uca (minuca) burgersi HOLTHUIS, 1967 (CRUSTACEA, BRACHYURA, OCYPODIDAE) in the laboratory

The fiddler crab Uca (Minuca) burgersi has been recorded in eastern American coast, from Florida to Brazil (from Maranhao to Sao Paulo). The juvenile stages of U. burgersi are described here based on material reared under laboratory conditions. Additionally a comparison of juvenile morphology is given for the juvenile of other species already studied with occurrence in the Brazilian coast. Larvae of U. burgersi were obtained from one ovigerous female hatched in the laboratory, which reached until the tenth juvenile stage. Rearing was conducted in a temperature-controlled climatic chamber at 25±1oC, 34‰ salinity and 12/12 (L/D) photoperiod. The first juvenile crab appeared at 43 days after hatching. Only one individual reached the tenth stage 174 days after hatching. The morphology of first juvenile crab was described as well as morphological changes throughout juvenile development. The sexual definition occurs in the fourth juvenile stage, abdominal dimorphism occurs in the sixth juvenile stage and chelipeds dimorphism occurs in the seventh juvenile stage

The contributions of evolutionary divergence and phenotypic plasticity to geographic variation in the western fence lizard, Sceloporus occidentalis

3 Local genetic adaptation and phenotypic plasticity are two mechanisms that can have marked effects on the morphology, performance, and behaviour of animals, producing geographic variation among populations. However, few studies have examined how these mechanisms interact during ontogeny to shape organismal phenotypes. We incubated eggs of the western fence lizard, Sceloporus occidentalis, from four populations (representing two latitudes and altitudes) in either a warm or cool environment in the laboratory. We then raised the hatchlings under common laboratory conditions, measured morphological and performance traits until 5 weeks of age, and compared juvenile morphology with that of field-caught adults from each population. The results obtained indicate that some phenotypic traits that contribute to performance (body size, hindlimb length, head shape) were relatively canalized in juveniles and differed among populations in a way that was consistent with adults from their population of origin. However, other traits (forelimb length, inter-limb length, mass, tail length), showed significant effects of incubation temperature, and this environmentally induced variation persisted throughout the experi- ment. Although selection pressure may be stronger for traits that are integral to survival, developmental effects might still have a lasting impact on traits less important to organismal fitness. We discuss the results obtained in the present study the context of the life history of these animals. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99, 84-98. ADDITIONAL KEYWORDS: development - incubation - local adaptation - morphology - ontogeny - performance - reaction norm - temperature.

DNA Methylation in Acacia mangium In vitro and Ex-vitro Buds, in relation to their Within-shoot Position, Age and Leaf Morphology of the Shoots

Abstract DNA methylation was analyzed in Acacia mangium Willd. buds collected from in vitro and field growing shoots from the same clone and its juvenile offspring. Shoot tips from in vitro microshoots showed higher levels of DNA methylation for juvenile (23.4%) than for mature (21.8%) plant material, irrespective of their morphology. Likewise, under the same in vitro conditions, the apical buds collected from microshoots exhibiting the juvenile morphology displayed higher DNA methylation rates (23.2%) than those characterized by the mature phyllode morphological type (22.1%), regardless of the age of the plant material source. In outdoor conditions, apical buds collected from mature tree growing shoots were significantly less methylated (20.9%) than the resting axillary buds located just underneath (25.2%) and than the apical buds from the in vitro microshoots of the same clone and mature-like phyllode morphology (22.6%). Overall, the DNA methylation levels found for our Acacia mangium plant materials were consistent with those reported for other Angiosperms, but showed, similarly to other recent findings in different species, that DNA methylation in plants does not always increase with ageing. This was discussed in relation to other phase-related traits and more particularly foliage characteristics, which are conspicuous markers of ageing in this heteroblastic species.

Morphology of three species of Crotonioidea Thorel, 1876 (Acari: Oribatida), and relations between some genera

The morphology of juveniles of Archegozetes longisetosus Aoki, 1965 (Trhypochthoniidae), and two members of Malaconothridae, Trimalaconothrus angulatus Willmann, 1931, and Malaconothrus monodactylus (Michael, 1888) is described and illustrated, and the tritonymph of A. longisetosus and all juvenile stages of T. angulatus are described and illustrated for the first time. The juveniles of these species differ mainly by the presence of setae f 2 and h 3 in the larva, seta exs and pattern of cuticle in the nymphs, and some setal formulae. Based on the morphology of juvenile stages and adults, the relationship between Malaconothridae and Trhypochthoniidae is discussed, and keys to the larvae and nymphs of some European species of these families are presented.

Diversity and disparity ‘down under’: Systematics, biogeography and reproductive modes of the ‘marsupial’ freshwater Thiaridae (Caenogastropoda, Cerithioidea) in Australia

We systematically revise here the Australian taxa of the Thiaridae, a group of freshwater Cerithioidea with pantropical distribution and “marsupial” (i.e. viviparous) reproductive modes. On this long isolated continent, the naming of several monotypic genera and a plethora of species have clouded both the phylogenetical and biogeographical relationships with other thiarids, in particular in Southeast Asia, thus hampering insight into the evolution of Australian taxa and their natural history. Based on own collections during five expeditions to various regions in Australia between 2002 and 2007, the study of relevant type material and the comparison with (mostly shell) material from major Australian museum collections, we describe and document here the morphology (of adults and juveniles) and radulae of all relevant thiarid taxa, discussing the taxonomical implications and nomenclatural consequences. Presenting comprehensive compilations of the occurrences for all Australian thiarid species, we document their geographical distribution (based on over 900 records) with references ranging from continent-wide to drainage-based patterns. We morphologically identify a total of eleven distinct species (also corroborated as distinct clades by molecular genetic data, to be reported elsewhere), of which six species are endemic to Australia, viz. “Thiara australis ”, Plotiopsis balonnensis, and “Stenomelania ” denisoniensis with wide distribution and Melasma onca, Sermyla venustula, and Ripalania queenslandica with more restricted ranges. In contrast, Thiara amarula and Stenomelania cf. aspirans as well as Melanoides tuberculata, Plotia scabra, and Sermyla riqueti are widely distributed also outside Australia, in particular in the Malay Archipelago and the Indo-West Pacific, respectively. The occurrences especially of the latter three species are discussed, concluding on quite distinct historical contingencies. Three thiarids species, viz. Stenomelania cf. aspirans, Sermyla riqueti and Plotia scabra, are recorded here for the first time for Australia. Based on a new taxonomic framework for the Thiaridae we point out some of the pertinent problems with naming and artificial delineation of species, revealing why typology and earlier practice of splitting was misleading in case of these truly “Darwinian snails”. We also report on finding two clearly distinct viviparous modes in Australian thiarids, discussing their distribution in certain fluvifaunal provinces and major drainage systems in concert with these reproductive features of life history tactics. While the live-bearing T. amarula, S. cf. aspirans, and R. queenslandica, that release veligers (ovo-viviparity), are found to have very restricted occurrences in rivers and streams in the Jardinian province of NE Queensland only, the five more widely distributed Australian endemics Plotiopsis balonnensis and “Stenomelania ” denisoniensis as well as “Thiara australis ”, Sermyla venustula and Melasma onca in the Leichhardtian province all brood and release shelled juveniles (eu-viviparity). Finally, we hypothesize on the evolutionary history and colonization of Australia by different lineages of these freshwater Cerithioidea. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Growth and morphological development of laboratory-reared larval and juvenile snakeskin gourami Trichogaster pectoralis

Morphological development, including that of fins, labyrinth organ, body proportions, and pigmentation, in laboratory-hatched larval and juvenile snakeskin gourami Trichogaster pectoralis is described. Body lengths (BL; mean ± SD) of larvae and juveniles were 2.3 ± 0.1 mm just after hatching (day 0) and 8.2 ± 0.6 mm on day 22, reaching 14.1 ± 2.3 mm on day 48. Aggregate fin ray numbers attained their full complements in juveniles >11.8 mm BL. Preflexion larvae started feeding on day 2 following upper and lower jaw formation, the yolk being completely absorbed by day 12. Subsequently, oblong conical teeth appeared in postflexion larvae >8.2 mm BL (day 16). Melanophores on the body increased with growth, with a large dark spot developing on the lateral midline at the caudal margin of the body in flexion larvae >6.1 mm BL. Subsequently, a broad vertical dark band from the eye to the caudal peduncle developed in postflexion larvae >8.9 mm BL. Proportions of head and pre-anal lengths became constant in postflexion larvae greater than ca. 9–10 mm BL, whereas those of maximum body depth, eye diameter, and snout length failed to stabilize in fish of the size examined in this study. First soft fin ray of the pelvic fin elongated, reaching over 40% BL. The labyrinth organ differentiated in postflexion larvae >7.4 mm BL (day 22). Comparisons of larval and juvenile morphology with another anabantoid species Anabas testudineus were also made, revealing several distinct differences, particularly in the numbers of myomeres and fin rays in the dorsal/anal fins, mouth location and body shape.

Microgeographic variation in the effects of larval temperature environment on juvenile morphology and locomotion in the pool frog

AbstractIn animals with complex life cycles, the environment experienced early during the development may have strong effects on later performance and fitness. We investigated the intraspecific variation in the effects of larval temperature environment on the morphology and locomotory performance of juvenile pool frogs Rana lessonae originating from three closely located populations of the northern fringe metapopulation in central Sweden. Tadpoles were raised individually at two temperatures (20 and 25 °C) until metamorphosis. We measured the morphology of the metamorphs and tested the jumping performance of the froglets after complete tail absorption. We found that early temperature environment affected juvenile morphology, metamorphs from high‐temperature environments having relatively longer hindlimbs (tibiofibulas) and longer tails when weight at metamorphosis was accounted for. In absolute terms, froglets from low temperature jumped significantly longer; however, after correcting for size differences the relationship was reversed, individuals raised at high temperature performing better. In both temperatures, relative jumping performance was positively associated with tibiofibula and body length. Populations differed both in metamorphic traits and in jumping capacity, especially at low temperature, suggesting microgeographical variation in temperature sensitivity within the metapopulation. Our results indicate that the temperature environment experienced during the early aquatic stages can influence the morphology and performance of juvenile frogs, and that these effects can be population specific.

Morphology and function of the head in foetal and juvenile Scolecomorphus kirkii (Amphibia: Gymnophiona: Scolecomorphidae)

The external and musculoskeletal morphology of the head is described for an ontogenetic series of the scolecomorphid caecilian Scolecomorphus kirkii. The rostral region of foetuses and juveniles is expanded into large, posterolaterally pointing paraoral processes that are formed by the maxilla. Extraoral teeth are present on the underside of the rostrum and laterally on the paraoral processes. In the foetuses, teeth are covered by epidermal tissue. The endoskeletal part of the foetal skull is largely cartilaginous, but all of the dermal bones, with the exception of the squamosal, are present. The foetal chondrocranium is extensively developed and shows a peculiar, posterolateral process of the nasal capsule that is connected to the trabecula cranii by a transverse bar posterior to the choana, and extends further posterior beyond the level of the posterior end of the pila antotica. Only two mm. adductor mandibulae are present, together with two pterygoideus muscles that insert onto the lower jaw. The palatoquadrate and quadrate of foetuses and juveniles, respectively, are highly mobile. It is suggested that the derived head morphology of Scolecomorphus foetuses and juveniles is an adaptation to specialized postparitive feeding. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 96, 491–504.

Delimitación y Estatus de Handroanthus Heptaphyllus y H. Impetiginosus. (Bignoniaceae, Tecomeae)

Two species of the genus Handroanthus with pink (eventually white) flowers are recognized in Argentina: Handroanthus heptaphyllus and H. impetiginosus . Those two species, treated as synonyms by some authors, are closely related by their morphology, and often mis-identified, particularly at juvenile stages. We studied adult and juvenile morphology of both entities to establish both their taxonomic boundaries and status. One hundred herbarium specimens were analyzed, new collections of native and cultivated individuals were made, and some of these were cultivated from seeds, so that young seedlings could also be studied. We found clear morphological differences that support the recognition of two different species. Descriptions, keys and illustrations are provided for both species as adult and seedlings. We also present a table summarizing differences between both species at different developmental stages and a map with their distribution in Argentina.

Re-examination of the type material of Cambaroides schrenckii (Kessler, 1874) (Decapoda: Cambaridae) with a lectotype designation, re-description, and discussion on its phylogenetic position

ABSTRACT The syntypes of the Russian freshwater crayfish, Cambaroides schrenckii (Kessler, 1874) and Cambaroides sachalinensis (Birstein & Winogradow, 1934), that were considered lost, were recently found at the Zoological Institute of the Russian Academy of Sciences, St. Petersburg. Our re-examination has shown that C. sachalinensis is a junior synonym of C. schrenckii. A lectotype of C. schrenckii is designated, and a description is made on the basis of type material and supplemental material recently collected from the Russian Federation. Detailed information on geographic distribution of this species is provided. Morphology and behavior of juveniles, and the position of spermatophores attached to the adult females also are recorded. The phylogenetic position of this genus is evaluated based on these characteristics.