On botulinum neurotoxin variability

The rapidly growing number of botulinum neurotoxin sequences poses the problem of the possible evolutionary significance of the variability of these superpotent neurotoxins for toxin-producing Clostridium species. To progress in the understanding of this remarkable phenomenon, we suggest that researchers should (i) abandon an anthropocentric view of these neurotoxins as human botulism-causing agents or as human therapeutics, (ii) begin to investigate in depth the role of botulinum neurotoxins in animal botulism in the wilderness, and (iii) devote large efforts to next-generation sequencing of soil samples to identify novel botulinum neurotoxins. In order to compare the fitness of the different toxins, we suggest that assays of all the steps from toxin production to animal death should be performed

Context-dependent evaluation of prospective mates in a fish

Female choice is often assumed to be based on absolute preference, driven by a threshold value of mate attractiveness. However, increasing evidence suggests that females may instead perform a comparative evaluation of prospective mates, possibly incurring in violation of rational decision rules (e.g. independence from irrelevant alternative, IIA). A prototypical case is the ‘asymmetrically dominated decoy’ effect where the preference for a target option over a competitor is altered by the addition of an irrelevant alternative. Here, we test for this effect in the peacock blenny Salaria pavo. Females, in binary test (i.e. focal option dyad differing in body size and extension of a yellow spot), strongly preferred one of the options. The effect of decoys, asymmetrically dominating the focal options for either yellow spot extension or body size, varied according to the initially preferred trait and the decoy type. Indeed, the addition of a decoy caused a shift in preference only when the decoy exhibited the intermediate expression of the trait less preferred initially. By contrast, females did not modify their preference in the presence of the decoy for their preferred trait. Although females’ evaluation was context-dependent, the violation of IIA was clearly observed only with respect to the initially less preferred trait. This does not exclude that females are in any case using comparative decision rules. Indeed, when faced with three alternatives, two of which are proportionally closer to each other than to the third one, they might not be able to discriminate among them, perceiving stimulus absolute magnitude

Multiple paternity and hybridization in two smooth-hound sharks

Multiple paternity appears to be a common trait of elasmobranch mating systems, with its occurrence likely driven by convenience, due to females seeking to minimize the stress of male harassment. Here we use molecular markers to analyse the frequency of multiple paternity in two related viviparous sharks, Mustelus mustelus and Mustelus punctulatus. We first applied molecular methods to assign pregnant females, embryos and additional reference adults (N\u2009=\u2009792) to one of the two species. Paternity analysis was performed using a total of 9 polymorphic microsatellites on 19 females and 204 embryos of M. mustelus, and on 13 females and 303 embryos of M. punctulatus. Multiple paternity occurs in both species, with 47% of M. mustelus and 54% of M. punctulatus litters sired by at least two fathers. Female fecundity is not influenced by multiple mating and in 56% of polyandrous litters paternity is skewed, with one male siring most of the pups. Genetic analyses also revealed hybridization between the two species, with a M. punctulatus female bearing pups sired by a M. mustelus male. The frequency of polyandrous litters in these species is consistent with aspects of their reproductive biology, such as synchronous ovulation and possible occurrence of breeding aggregations

Inhibition of the deubiquitinase USP8 corrects a Drosophila PINK1 model of mitochondria dysfunction.

Aberrant mitochondrial dynamics disrupts mitochondrial function and contributes to disease conditions. A targeted RNA interference screen for deubiquitinating enzymes (DUBs) affecting protein levels of multifunctional mitochondrial fusion protein Mitofusin (MFN) identified USP8 prominently influencing MFN levels. Genetic and pharmacological inhibition of USP8 normalized the elevated MFN protein levels observed in PINK1 and Parkin-deficient models. This correlated with improved mitochondrial function, locomotor performance and life span, and prevented dopaminergic neurons loss in Drosophila PINK1 KO flies. We identified a novel target antagonizing pathologically elevated MFN levels, mitochondrial dysfunction, and dopaminergic neuron loss of a Drosophila model of mitochondrial dysfunction.his work was supported by grants from the Italian Ministry of Health “Ricerca Finalizzata” (GR-2011-02351151), Rita Levi Montalcini “Brain Gain” program, and Michael J Fox RRIA 2014 (Grant ID 9795) to E Ziviani and by ERC FP7-282280, FP7 CIG PCIG13-GA-2013-618697, and Italian Ministry of Research FIRB RBAP11Z3YA_005 to L Scorrano. AJ Whitworth is funded by MRC Core funding (MC_UU_00015/6)

The embryological origin of the juxtatesticular body in jawfishes (Opistognathidae)

A male accessory sex organ, termed the juxtatesticular body (JTB), is located in the posterior part of the trunk, outside the coelomic cavity, lying ventral to the urinary ducts and dorsal to the urinary bladder and testes in jawfishes. Its microscopic structure is unusual for an accessory sex organ because it is highly vascularized, organized in small follicles, and ductless. The embryological origin of the JTB and the development of the urogenital apparatus was studied in juveniles of Opistognathus whitehurstii and O. maxillosus. Both sexes possess a structure located outside the coelomic cavity in the posterior part of the trunk. In females this structure showed the same histological organization as the kidney, however in males it was different and recognized as the JTB. The degree of development of the JTB followed that of the testes, being represented in youngest recognizable males only by a small mass of mesenchymal cells while it was fully developed in males with spermatogenic testes. In most immature males renal structures, such as tubules and glomeruli, were found in the dorsal part of this structure. On the basis of anatomical and cytological features a nephrogenic origin for the JTB is proposed

Male reproductive apparatus of some blennioidei (Pisces: Teleostei)

I performed a comparative study of the morphology of the male genital apparatus on 11 species of blennies: Acanthemblemaria spinosa (Chaenopsidae), Enneanectes pectoralis, E. boelkei (Tripterygiidae), Gillellus rubrocinctus (Dactylopteridae), Labrisomus nuchipinnis, L. haitiensis, L. bucciferus, Paraclinus nigripinnis, Malacoctenus versicolor, M. triangulatus, and M. macropus (Labrisomidae). In the chaenopsid fish, an unpaired testis and a single seminal vesicle occurred. The seminal vesicle consisted of a single chamber containing no sperm and was filled with an homogeneous secretion. In the tripterygiid, dactyloscopid, and labrisomid species testes were paired, with a testicular gland interposed between the seminiferous lobules and the spermduct of each testis. Interspecific differences were noted in the volume of the testicular gland, relative to that of the testis, and in the development of the spermduct. Histochemical stainings in the testicular gland of Malacoctenus triangulatus and M. macropus revealed the secretion of glycogen and nonsulphated mucins. The possible involvement of the testicular gland, seminal vesicle, and spermduct in the nutrition of germ cells, production of a viscous seminal fluid and storage of sperm is discusse