Evidence of doubly uniparental inheritance of the mitochondrial DNA in Polititapes rhomboides (Bivalvia,Veneridae): Evolutionary and population genetic analysis of F and M mitotypes

Doubly uniparental inheritance (DUI) is a particular mitochondrial DNA inheritance mode reported in a number of bivalves. DUI species show two types of mtDNA, one transmitted from females to daughters and sons (F mitotype) and another one from males to sons (M mitotype). In Veneridae, the existence of DUI has been investigated in several species but it was found in only two of them. In this study, we obtained partial sequences of rrnL, cytb and cox1 genes of males and females of Polititapes rhomboides from NW Spain and we demonstrated the existence of heteroplasmy in males, as expected under DUI. F and M mitotypes showed a taxon-specific phylogenetic pattern and similar evolutionary rates. We focused on cox1 for population genetic analysis, examining separately F and M mitotypes, but also F mitotypes from females (F_♀) and males (F_♂). In all cases, cox1 bears signs of strong purifying selection, with no apparent evidence of relaxed selection in the M genome, while the divergence between F and M genomes is in agreement with the neutral model of evolution. The cox1 polymorphism, higher at the M than at the F genome, also shows clear footprints of genetic hitchhiking with favourable mutations at other mtDNA loci, except for F_♂. In terms of population structure, results suggest that the pattern depends on the examined mitotype (F, F_♀, F_♂ or M).     

Postnatal cranial ontogeny of the Greater Bulldog Bat Noctilio leporinus (Chiroptera: Noctilionidae)

We studied the postnatal development of the skull of Noctilio leporinus, examining the relationship between ectocranial elements, including shape changes and sutures closure and fusion. Most shape changes and structure development were observed at subadults and adults; zygomatic arch, sagittal crest, occipital process and mandibular processes developed noticeably up to the adult stage. Cranial sutures closure and fusion sequences of N. leporinus agree with that of hystricomorph rodents, artiodactyls, primates, sirenians and carnivores, beginning with the cranial vault followed by the basicranium, supporting a conserved pattern for mammalia. Detailed comparisons exhibit a complete cranial sutures fusion reached earlier at Desmodus rotundus regarding N. leporinus and Pteropus sp., and an early fusion for the sutura coronalis plus late fusion for the sutura sagittalis at N. leporinus regarding Desmodus rotundus. The drastic shape changes of cranial elements, as well as sutures closure and fusion in N. leporinus at subadults and adults, seem to be closely related to the acquisition of morphological specializations during stages of development when the fisher bat begins to feed independently.     

Development and multiplex PCR amplification of microsatellite markers in the commercial clam Venerupis rhomboides (Mollusca: Bivalvia)

Venerupis rhomboides is a commercial clam whose production could be enhanced through effective management of natural and hatchery stocks. This study provides the first panel of microsatellite markers for the exploitation of this species according to genetic criteria. A total of 22 polymorphic microsatellite loci were isolated and characterized from two genomic libraries enriched for different motifs. The number of alleles per locus ranged from 2 to 14 in a sample of 20 clams from Spain, and the observed and expected heterozygosity from 0 to 0.95 and 0.05–0.901, respectively. Sixteen loci were in agreement with Hardy–Weinberg equilibrium after sequential Bonferroni correction and linkage disequilibrium between loci pairs was not detected. To reduce the cost of the genotyping process, tri- and pentaplex PCRs, amplifying a total of 13 microsatellites loci were optimized. The microsatellites developed here represent the first nuclear markers described in V. rhomboides and will be useful tools for genetic studies involving assessment of genetic variation and population structure of natural and cultivated populations, assignment testing, construction of genetic linkage maps and dissection of production traits.