Genetic data from the extinct giant rat from Tenerife (Canary Islands) points to a recent divergence from mainland relatives

Evolution of vertebrate endemics in oceanic islands follows a predictable pattern, known as the island rule, according to which gigantism arises in originally small-sized species and dwarfism in large ones. Species of extinct insular giant rodents are known from all over the world. In the Canary Islands, two examples of giant rats, †Canariomys bravoi and †Canariomys tamarani, endemic to Tenerife and Gran Canaria, respectively, disappeared soon after human settlement. The highly derived morphological features of these insular endemic rodents hamper the reconstruction of their evolutionary histories. We have retrieved partial nuclear and mitochondrial data from †C. bravoi and used this information to explore its evolutionary affinities. The resulting dated phylogeny confidently places †C. bravoi within the African grass rat clade (Arvicanthis niloticus). The estimated divergence time, 650 000 years ago (95% higher posterior densities: 373 000–944 000), points toward an island colonization during the Günz–Mindel interglacial stage. †Canariomys bravoi ancestors would have reached the island via passive rafting and then underwent a yearly increase of mean body mass calculated between 0.0015 g and 0.0023 g; this corresponds to fast evolutionary rates (in darwins (d), ranging from 7.09 d to 2.78 d) that are well above those observed for non-insular mammals.     

Description of the Type Specimen of the Extinct Tenerife Giant Rat (Canariomys bravoi)

The holotype of the Tenerife (Canary Islands) giant rat, Canariomys bravoi, an almost complete cranium from the Late Pleistocene site of Cueva de las Palomas, is described for the first time. This species is characterized by its large size, robust skull with a short rostrum, dorsal inflation at the level of the infraorbital foramen, and moderately high-crowned upper molars which develop partial stephanodonty at advanced wear stages. Canariomys tamarani from Gran Canaria Island, the only other species of this genus known so far, is slightly smaller and further differs in its higher crowned molars with cusps arranged in a lamellar pattern. However, their crania are remarkedly similar and present a distinctive anatomy of the zygomatic plate, which is very high on the rostrum, so that its dorsal border is nearly on level with the zygomatic process of the maxilla instead of considerably below it as usually seen in murines. This is also observed in other insular, often large-sized, murines but certainly evolved in parallel as an adaptation to herbivory. Molar morphology is congruent with recent analyses of ancient molecular data of C. bravoi which place it in the tribe Arvicanthini (mostly African murines), more concretely within the Arvicanthis niloticus species complex. Even though genetic data indicate that both species diverged very recently, just 650,000 years ago, cranial and dental anatomy of C. bravoi are very derived. Conversely, C. tamarani presents a molar morphology reminiscent of that of A. niloticus albeit associated with a similarly highly derived cranial anatomy.

     

The hypoglycemic activity of Euclea undulata Thunb. var. myrtina (Ebenaceae) root bark evaluated in a streptozotocin–nicotinamide induced type 2 diabetes rat model

The hypoglycemic activity of a crude acetone extract of the root bark of Euclea undulata var. myrtina was evaluated in a streptozotocin–nicotinamide induced type 2 diabetes rat model after positive results were obtained by in vitro screening of glucose utilization by C2C12 myocytes, 3T3-L1 preadipocytes and Chang liver cells and alpha-glucosidase inhibition. Thirty male Wistar rats were used for the experiment. Type 2 diabetes was induced by a single intraperitoneal injection of streptozotocin and administration of nicotinamide 15 min after. Animals exhibiting fasting glucose levels of 140–200 mg/dl after 7 days were screened as type 2 diabetes. Extract was administered for 21 days orally at a concentration of 50 mg/kg and 100 mg/kg respectively. Glibenclamide (1 mg/kg) was used as positive control. On day 21, blood lipid profiles and body weight were determined by using standard enzymatic colorimetric kits before the rats were sacrificed by cervical decapitation. The crude acetone extract of E. undulata root bark at a concentration of 100 mg/kg body weight significantly lowered fasting blood glucose levels as well as elevated cholesterol and triglyceride levels to near normal without any weight gain. The results indicate that the crude acetone root bark extract of E. undulata exhibit antidiabetic activity in type 2 induced diabetic rats. It confirms the in vitro screening results as well as its use in the treatment of diabetes by traditional healers and herbalists in southern Africa.     

Morphological variations of an invasive cyprinid fish (Carassius gibelio) in lentic and lotic environments inferred from the body,otolith, and scale shapes

This study investigated the morphological variation of gibel carp Carassius gibelio collected from various water bodies in Türkiye. The fish samples were obtained from three dams (Karacaören-1, Karakaya, and Keban), two natural lakes (Beyşehir and Suğla), and a river (the Tigris River). The dimorphism in body shape was examined with geometric morphometrics, while elliptic Fourier analysis and shape indices were used to describe the variation in lapilli otoliths (hereafter “otoliths”) and scale shapes. The body of C. gibelio revealed higher variations, particularly in the body depth, snout length, caudal fin, and caudal peduncle, among different stations. Geometric morphometric analysis determined a streamlined body shape of C. gibelio in the Tigris River compared to other stations, while C. gibelio from the natural lakes had a deeper body shape. The body of C. gibelio exhibited a significant homogenous shape between the Beyşehir and Suğla lakes, providing the lowest Procrustes distance. The elliptic Fourier analysis revealed that the otolith shape varied significantly between all stations. However, the scale shape was remarkably similar among nearby areas such as Karacaören dam, Suğla, and Beyşehir lakes. These results evinced high degree of intra-population morphological variation in C. gibelio in response to prevailing environmental conditions that probably facilitate their successful establishment in a novel environment.     

A Contribution to the Morphology and Phylogeny of Chlamydodon,with Three New Species from China (Ciliophora,Cyrtophoria)

Three new cyrtophorian ciliates isolated from coastal areas of China were described based on morphological and genetic data. The Chlamydodon mnemosyne‐like species Chlamydodon similis sp. n. differs from its congeners mainly by its number of somatic kineties. Chlamydodon oligochaetus sp. n. is distinguished from its congeners mainly by having fewer somatic kineties, and/or an elongated body shape. Chlamydodon crassidens sp. n. is characterized mainly by an inverted triangular body shape, a posteriorly interrupted cross‐striated band (5–6 μm wide), and a large cytostome. Moreover, we provided small‐subunit (SSU) rDNA sequences of C. similis sp. n. and C. oligochaetus sp. n. Maximum likelihood (ML) and Bayesian inference (BI) consistently placed C. similis sp. n. as a sister to C. paramnemosyne, but showed different branching position of C. oligochaetus sp. n., which may be due to a low taxon sampling in the Chlamydodontidae and/or an insufficient resolution of the marker gene at species level.     

Thermoconformity strategy in the freshwater turtle Hydromedusa tectifera (Testudines,Chelidae) in its southern distribution area

Ectotherm species are not capable of generating metabolic heat; therefore, they present different strategies for regulating their body temperatures, ranging from a precise degree of thermoregulation to a passive thermoconformity with ambient temperatures. In reptiles, aerial basking is the most common mechanism for gaining heat. However, among aquatic reptiles, such as freshwater turtles, aquatic basking is also frequent. Hydromedusa tectifera is a turtle of exclusively aquatic and nocturnal habits widely distributed in South America. We studied the relationship between body temperature (Tb) of H. tectifera and its habitat, and explored the effects of sex, life stage and body size and mass on Tb. Fieldwork was conducted in two streams of a mountain area of central Argentina. We recorded cloacal temperature, size and mass of 84 turtles. We also determined individuals’ sex and life stage (adult/juvenile). Regarding ambient temperatures, we measured water temperature on the surface (Tsurf) and at depth of turtle capture (Tdepth) and air temperature. Mean Tb was 18.58 °C (Min = 10.20 °C; Max = 25.70 °C). Tsurf and Tdepth were highly correlated. Multi-model analysis using Akaike criterion indicated that Tb was strongly associated with water temperature, whereas air temperature and body size and mass did not show a significant effect. There was also no effect of turtle sex or life stage on Tb. Our results indicate that H. tectifera is a thermoconformer and eurythermal species. A nocturnal pattern of activity and a fully aquatic lifestyle are suggested as determinant factors.     

Multivariate morphometry and rates of morphologic evolution within the Pennsylvanian fusulinid Beedeina (Ardmore Basin,Oklahoma, USA)

Ten species in the genus Beedeina from Desmoinesian (Middle Pennsylvanian) rocks in the Ardmore Basin (southern Oklahoma, USA) were discriminated on the basis of 29 measured variates. Each species was characterized by its mean scores on the first and second axes in canonical variates analysis (CVA) and by its lowest stratigraphic occurrence in order to identify evolutionary lineages. The pumila → plattensis → erugata lineage involved overall size increase without appreciable changes in shape. The insolita → haworthi → aff. whitakeri → acme and insolita → cf. novamexicana → euryteines lineages both exhibited axial lengthening, but the former involved relative elongation and the latter involved relative inflation. CVA function coefficients were used to identify taxonomically important characters for the analysis of rates of morphologic evolution, and it was discovered that three of the five most important characters occur in the embryonic portion of the shell (proloculus diameter, half-length and wall thickness of the first volution). Rates of evolution are variable among ancestor-descendant pairs in the three lineages, but they do not differ significantly from rates documented in other groups of fossil and extant organisms. Apparent variation in rates is an artifact of the unequal time intervals over which morphologic change was measured, with shorter intervals resulting in faster rates. Among the five variates examined in all ancestor-descendant pairs (i.e., across a range of time intervals), proloculus size and half-length of the first and sixth volutions exhibited the fastest mean rates of change, whereas wall thickness in the first volution and radius vector of the fifth volution exhibited slower mean rates of change.     

Onosma hispidum L. extract reverses hyperlipidemia,hypertension, and associated vascular dysfunction in rats

Onosma hispidum.L (O. hispidum) belongs to the family Boregineacea. A preliminary study and its medicinal use suggested its role in the management of hyperlipidemia. The present study aimed to assess the effect of methanolic root extract of O. hispidum in hyperlipidemia and associated vascular dysfunction. Oral administration of O. hispidum crude extract (Oh. Cr) to tyloxopol and high fat diet-induced hyperlipidemic Sprague-Dawley rats for 10 and 28 days significantly reduced total triglycerides and cholesterol (p < 0.001), compared to hyperlipidemic rats. Oh. Cr 250 mg/kg orally treated rats significantly (p < 0.001) reduced both the total body weight and atherogenic index in tylaxopol and HFD rats. In HMG-CoA assay, the inhibition of the enzyme was significant in Oh.Cr (250 mg/kg) treated group. Histopathological studies indicated that the group treated with Oh.Cr 250 mg/kg/day showed regular morphology of aortic intima, media and adventitia, and improved the endothelial damage. To investigate the vascular dysfunction, isolated rat aorta rings from all groups were pre-contracted with 1 µM phenylephrine (PE), and the effect of acetylcholine (Ach) was monitored. In the aorta isolated from Oh.Cr (50 mg/kg) treated group, Ach completely relaxed the PE-induced contraction with EC₅₀ value of 0.05 µg/mL 0.015 (0.01–0.2) compared to the hyperlipidemic control group (<30% relaxation). In atorvastatin (10 mg/kg) treated rat aorta, Ach showed 50% relaxation. The Oh.Cr extract also reduced (105.92 ± 1.14 to 66.63 ± 0.85 mmHg) mean arterial pressure in hyperlipidemic hypertensive rats. These findings suggest that extract of O. hispidum is an effective remedy for hypercholesterolemia, and hypertriglyceridemia, which acts through inhibition of HMG-CoA and improving vascular dysfunction.     

Geographic variation of body morphology of the Atlantic bluefin tuna, (Thunnus thynnus,Linnaeus, 1758)

Geometric morphometric methods were used to explore body shape morphology in 260 Atlantic bluefin tuna, Thunnus thynnus, collected in Sardinia (Western Mediterranean) during the breeding phase and in the Bay of Biscay (North Eastern Atlantic) during the feeding phase. The shape of each specimen was captured by high resolution digital images and recording the 2‐D coordinates of seven morphological landmarks. A general procruste analysis (GPA) was applied in order to eliminate any morphological variations resulting from size, position or orientation of specimens. A thin plate‐spline (TPS) method was then used to provide a graphical representation of the shape conformation between two sets of data. Results of the regression model between the direct and indirect measurements accounted for a R² = 0.98. The Principal Components Analysis shows differences linked to the two sampling areas, accounting for 37% and 19.97% of the body shape variation in the first (PC1) and second (PC2) principal component, respectively. Specifically, the deformation grid projection highlights the major differences regarding the anterior‐ventral part of the body (landmark 5‐6‐7). These differences might not necessarily be linked to an actual population substructure. Instead, it was hypothesized that such body shape differences were due to the diverse life phases during which specimens were collected, since the reproductive specimens show a ‘pot‐bellied’ shape, which was larger than for the feeding specimens that showed a ‘slimmer’ shape. Analyses of likely sexual dimorphism conducted on Sardinian specimens did not reveal any significant differences; whereas body shape differences related to the pre‐ and post‐reproductive sizes were detected.     

A new large barn owl (Aves, Strigiformes, Tytonidae) from the Middle Pleistocene of Sicily, Italy, and its taphonomical significance

A new species of Tytonidae, Tyto mourerchauvireae, is described from the Sicilian cave deposits of Spinagallo, Luparello and Marasà, which have yielded a common vertebrate fossil assemblages referred to the early Middle Pleistocene. T. mourerchauvireae nov. sp. shows a pronounced increase in body size compared to other congeneric taxa. It is larger than the extant Tyto alba and the extinct Tyto balearica and Tyto sanctialbani and comparable in size among the Mediterranean taxa only with the extinct Tyto robusta, which differs in some morphological characteristics of the long bones. The insular adaptations of T. mourerchauvireae nov. sp. and the differences from the other forms of the genus Tyto which spread through the Mediterranean area during Neogene and Pleistocene are discussed. The fossil assemblages of the early Middle Pleistocene of Sicily are dominated by extinct giant Gliridae of the genus Leithia and Maltamys; these taxa are regarded as the primary prey items of T. mourerchauvireae nov. sp. The Gliridae remains were analysed microscopically to detect possible modifications of bones and teeth caused by ingestion and digestion processes. This type of analysis, together with the qualitative study of the fossil assemblages, allows to show the taphonomical importance of T. mourerchauvireae nov. sp. as agent of accumulation in such Sicilian fossil assemblages. Incidentally the taxonomic validity of T. robusta is discussed and confirmed.     

An improved,chromosome-level genome of the giant panda (Ailuropoda melanoleuca)

BackgroundThe iconic giant panda (Ailuropoda melanoleuca), as both a flagship and umbrella species endemic to China, is a world famous symbol for wildlife conservation. The giant panda has several specific biological traits and holds a relatively small place in evolution. A high-quality genome of the giant panda is key to understanding the biology of this vulnerable species.FindingsWe generated a 2.48-Gb chromosome-level genome (GPv1) of the giant panda named “Jing Jing” with a contig N50 of 28.56 Mb and scaffold N50 of 134.17 Mb, respectively. The total length of chromosomes (n = 21) was 2.39-Gb, accounting for 96.4% of the whole genome. Compared with the previously published four genomes of the giant panda, our genome is characterized by the highest completeness and the correct sequence orientation. A gap-free and 850 kb length of immunoglobulin heavy-chain gene cluster was manually annotated in close proximity to the telomere of chromosome 14. Additionally, we developed an algorithm to predict the centromere position of each chromosome. We also constructed a complete chromatin structure for “Jing Jing”, which includes inter-chromosome interaction pattern, A/B compartment, topologically associated domain (TAD), TAD-clique and promoter-enhancer interaction (PEI).ConclusionsWe presented an improved chromosome-level genome and complete chromatin structure for the giant panda. This is a valuable resource for the future genetic and genomic studies on giant panda.     

Cryptosporidium equi n. sp. (Apicomplexa: Cryptosporidiidae): Biological and genetic characterisations

The horse genotype is one of three common Cryptosporidium spp. in equine animals and has been identified in some human cases. The species status of Cryptosporidium horse genotype remains unclear due to the lack of extensive morphological, biological, and genetic data. In the present study, we have conducted biological and whole genome sequence analyses of an isolate of the genotype from hedgehogs and proposed to name it Cryptosporidium equi n. sp. to reflect its common occurrence in equine animals. Oocysts of C. equi measured 5.12 ± 0.36 μm × 4.46 ± 0.21 μm with a shape index of 1.15 ± 0.08 (n = 50). Cryptosporidium equi was infectious to 3-week-old four-toed hedgehogs (Atelerix albiventris) and mice, with a prepatent period of 2–9 days and a patent period of 30–40 days in hedgehogs. It was not infectious to rats and rabbits. Phylogenetic analyses of small subunit rRNA, 70 kDa heat shock protein, actin, 60 kDa glycoprotein and 100 other orthologous genes revealed that C. equi is genetically distinct from other known Cryptosporidium species and genotypes. The sequence identity between C. equi and Cryptosporidium parvum genomes is 97.9%. Compared with C. parvum, C. equi has lost two MEDLE genes and one insulinase-like protease gene and gained one SKSR gene. In addition, 60 genes have highly divergent sequences (sequence differences ≥ 5.0%), including those encoding mucin-like glycoproteins, insulinase-like peptidases, and MEDLE and SKSR proteins. The genetic uniqueness of C. equi supports its increasing host range and the naming of it as a valid Cryptosporidium species. This is the first known use of whole genome sequence data in delineating new Cryptosporidium species.     

A new genotype of Cryptosporidium from giant panda (Ailuropoda melanoleuca) in China

Fifty-seven fecal samples were collected from giant pandas (Ailuropoda melanoleuca) in the China Conservation and Research Centre for the Giant Panda (CCRCGP) in Sichuan and examined for Cryptosporidium oocysts by Sheather's sugar flotation technique. An 18-year-old male giant panda was Cryptosporidium positive, with oocysts of an average size of 4.60 × 3.99 μm (n = 50). The isolate was genetically analyzed using the partial 18S rRNA, 70 kDa heat shock protein (HSP70), Cryptosporidium oocyst wall protein (COWP) and actin genes. Multi-locus genetic characterization indicated that the present isolate was different from known Cryptosporidium species and genotypes. The closest relative was the Cryptosporidium bear genotype, with 11, 10, and 6 nucleotide differences in the 18S rRNA, HSP70, and actin genes, respectively. Significant differences were also observed in the COWP gene compared to Cryptosporidium mongoose genotype. The homology to the bear genotype at the 18S rRNA locus was 98.6%, which is comparable to that between Cryptosporidium parvum and Cryptosporidium hominis (99.2%), or between Cryptosporidium muris and Cryptosporidium andersoni (99.4%). Therefore, the Cryptosporidium in giant pandas in this study is considered as a new genotype: the Cryptosporidium giant panda genotype.     

Effects of salinity, temperature and individual variability on the reproduction of Eurytemora affinis (Copepoda; Calanoida) from the Seine estuary: A laboratory study

The brackish water copepod Eurytemora affinis is the most abundant copepod species in the low salinity zone (2-15) of the Seine estuary. Despite its ecological importance, little is known about its population dynamics in the Seine. We studied the effects of temperature (10 °C and 15 °C) and salinity (5, 15 and 25) on reproduction under non-limiting food conditions. We used experiments to determine multiple reproductive parameters for E. affinis. In all experiments, we fed E. affinis a mixture of Rhodomonas marina and Isochrysis galbana. Couples of pre-adult females (C5) and adult males were mated until the female extruded a clutch of eggs and then individual females were observed every 6-12 hours until death to determine (a) embryonic development time, (b) inter clutch time and (c) clutch size throughout their adult lifespan. All reproductive parameters were negatively affected by low temperature (10 °C) and by high salinity (25). At 10 °C and a salinity of 25, mortality during the post-embryonic period was extremely high (85%). Differences in all reproductive parameters between salinities 5 and 15 were minimal. From 15 °C to 10 °C mean latency time (time between hatching of eggs and extrusion of new ones) increased from 0.8 to 2.25 days, the mean embryonic development time from 2.2 to 3.2 days and the mean clutch size decreased from 38 to 22 eggs female^- 1. The mean clutch size decreased when females reached a critical age. The hatching success was high (near 95%) under all conditions except at high salinity. Egg production rates showed no significant differences between salinities 5 and 15 and were significantly higher at 15 °C (13 eggs female^- 1 day^- 1 at salinity 5 and 15) than at 10 °C (4 eggs female^- 1 day^- 1). These values at 15 °C were higher compared to those from other populations of E. affinis in estuaries or lakes. The high reproductive potential of E. affinis from the Seine estuary at 15 °C and low salinities explain its high densities in the low salinity zone during spring and early summer.     

Morphological and molecular characterization of Isospora amphiboluri (Apicomplexa: Eimeriidae), a coccidian parasite,in a central netted dragon (Ctenophorus nuchalis) (De Vis, 1884) in Australia

An Isospora species, Isospora amphiboluri, originally described by Canon in 1967 and later by McAllister et al. (1995), was isolated from a central netted dragon (Ctenophorus nuchalis) housed at a wildlife rehabilitation centre in Perth, Western Australia. Sporulated oocysts of Isospora amphiboluri (n = 30) are spherical, 24.2 (26.5–23.0) μm in length and 23.9 (22.4–25.9) μm in width, with a shape index of 1.01. The bilayered oocyst wall is smooth and light-yellow in color. Polar granule, oocyst residuum and micropyle are absent. The sporocysts are lemon-shaped, 15.7 (15.2–18.0) × 10.2 (8.9–11.2) μm, with a shape index (length/width) of 1.53. Stieda and substieda bodies are present, the Stieda body being small and hemidome-shaped and the substieda half-moon-shaped. Each sporocyst contains four vermiform sporozoites arranged head to tail. The sporozoites are 11.7 (9.9–16.2) × 3.0 (2.4–3.5) μm, with a shape index (length/width) of 3.87. A sporocyst residuum is present. Sporozoites contain a central nucleus with a finely distributed granular residuum. Comparison of oocyst measurements and their features with other valid Isospora species from hosts in the Agamid family confirmed that this Isospora species is Isospora amphiboluri. Molecular characterization of I. amphiboluri at the 18S rRNA and MTCOI loci showed the highest similarity with I. amphiboluri from the central bearded dragon, 99.8% and 99.7% respectively. This is the first report of I. amphiboluri from a central netted dragon in Australia.     

The evolution of the adult body form of the crested newt (Triturus cristatus superspecies,Caudata, Salamandridae)

We characterized the adult body form of the crested newt (Triturus cristatus superspecies) and explored its evolution. From seven morphometric traits, we determined that body size, interlimb distance and head width define the body form. None of the morphometric traits showed a phylogenetic signal. Three body‐shape morphotypes (Triturus dobrogicus + T. cristatus, Triturus carnifex + Triturus macedonicus and Triturus karelinii + Triturus arntzeni) and three body‐size morphotypes (T. dobrogicus, T. cristatus and all other crested newts) could be recognized. The ancestral phenotype (a large body with a short trunk and a wide head) characterized T. karelinii and T. arntzeni. Triturus carnifex and T. macedonicus had a somewhat different phenotype (large body and wide head, accompanied by mild body elongation). The most derived phenotype included body size reduction and more pronounced body elongation in T. cristatus and, especially, in T. dobrogicus. Body elongation occurred by trunk lengthening but not head and tail lengthening. Additionally, contrary to other tetrapods, evolutionary axis elongation in crested newts was followed by a decrease in body size. We advocate the hypothesis that ecology drives the evolution of body form in crested newts.     

Biometric analyses as a tool for the differentiation of two coccolith species of the genus Crepidolithus (Pliensbachian,Lower Jurassic) in the Basque-Cantabrian Basin (Northern Spain)

Biometric analyses were performed on 20 Pliensbachian samples from the Santotis section (Basque-Cantabrian Basin, N Spain), in order to separate the species Crepidolithus crassus and Crepidolithus crucifer based on their size, and to evaluate the role, if any, of the paleoenvironmental conditions on C. crassus and C. crucifer size changes. In each sample, 100 specimens of both C. crassus and C. crucifer were randomly selected and imaged for taking measurements of their length and width. The length/width ratio or eccentricity was calculated for each specimen. Our results show that C. crucifer is around 2 μm longer and 1.3 μm wider than C. crassus. Based on length measurements, two groups were statistically differentiated. Crepidolithus crucifer coccoliths are longer than 8.2 μm. However, an overlap has been observed for C. crassus and C. crucifer in the 8–8.5 μm range; in these cases, central area structure and crystallographic properties are essential for species separation. A trend towards a progressive increase in the size of both taxa has been observed throughout the studied interval and no obvious relationships have been recognized between the lithology, TOC values and coccolith size. However, the size increment in both C. crassus and C. crucifer coincides with a cooling period, suggesting a potential environmental control on coccolith size.Size shifts have been recorded first in C. crassus and later in C. crucifer. Based on the sizes of both species, we speculate that the large C. crucifer, perhaps inhabited a slightly deeper portion of the photic zone and, that the diachronous size variations in the two investigated taxa could be related to the transgressive phase recorded during the Late Pliensbachian. The discrepancy between size variations of C. crassus and C. crucifer specimens in the uppermost part of the studied section might be indicative of modifications of specific portions of the photic zone. We propose that the stratification of water masses probably reduced the ecologic niche of C. crucifer that was forced to reach shallower depths by reducing its size.     

The reproductive ecology of two subspecies of the bitterling Rhodeus atremius (Cyprinidae, Acheilognathinae)

The reproductive ecology of two endangered subspecies of the bitterling Rhodeus atremius was investigated in two rivers in Okayama and Fukuoka Prefectures, Japan. Several other bitterling species, R. ocellatus, Tanakia limbata, T. lanceolata, Acheilognathus tabira and A. rhombeus, are also found in these rivers. Spawning of both R. atremius subspecies was recorded between late March and August 2007, peaking between April and July. Females of R. atremius began to mature at small body size (minimum 25 mm). They had small clutch sizes (maximum 16 eggs) and developed a short ovipositor (mean 13.6 mm), which was used to deposit a bulb-shaped egg of comparatively large size (3.2 mm³, major and minor axes 2.8 and 1.5 mm). Clutch size, ovipositor length and egg size appear to be a function of female body size. Both the body size and ovipositor length of R. atremius with ripe ova and the size and shape of the eggs varied seasonally. Rhodeus a. suigensis achieved maturity at a smaller body size, had a longer ovipositor and produced smaller eggs, with the minor axis being wider relative to the major axis than those of R. a. atremius. Rhodeus atremius may be adapted for depositing small numbers of eggs in a much shallower position inside the gills of smaller host mussels than other bitterling species.     

Morphological and genetic differentiation of Eremina desertorum (Gastropoda,Pulmonata, Helicidae) in Egypt

To understand the processes that result in morphological and genetic diversity, we studied the differentiation of the land snails Eremina d. desertorum and Eremina desertorum irregularis in the deserts of northern Egypt. These two taxa are differentiated with regard to shell size and shape and are separated by a narrow hybrid zone west of Alexandria. The lack of differences in the genitalia and the lack of reciprocal monophyly of the mitochondrial haplotypes of E. d. desertorum and E. desertorum irregularis support their classification as subspecies rather than distinct species. Low genetic distances indicate that the differentiation is probably less than half a million years old. The genetic data indicate a population expansion in agreement with other evidence that the Nile region in northern Egypt was more humid well into historical times than today. Shell size and shape are correlated with a climatic gradient from cooler and more humid conditions along the Mediterranean coast to arid and hot conditions in the interior. The decrease of body size with decreasing precipitation and increasing temperature might be explained by limited time for food intake in the more arid regions. The shape differences between the taxa are partly an indirect consequence of selection for body size, but are also directly affected by selection for reduction of aperture size.