Biological ballistics-no longer a shot in the dark

Established methods of genetic transformation, such asAgrobacterium transfection and DNA uptake by protoplasts have not been successfully applied to some of the world’s major crops. This article reviews the evolution of microprojectile bombardment, from its inception to establishment at the method of choice for transformation of otherwise recalcitrant crops such as maize, wheat and barley. The potential of microprojectile bombardment, as a universal method of transformation, is discussed in the context of the wide range of species transformed, together with the transformation of plastid genomes and the contribution of this technology beyond the boundaries of the plant kingdom.     

A shot in the dark: same-sex sexual behaviour in a deep-sea squid

Little is known about the reproductive habits of deep-living squids. Using remotely operated vehicles in the deep waters of the Monterey Submarine Canyon, we have found evidence of mating, i.e. implanted sperm packages, on similar body locations in males and females of the rarely seen mesopelagic squid Octopoteuthis deletron. Equivalent numbers of both sexes were found to have mated, indicating that male squid routinely and indiscriminately mate with both males and females. Most squid species are short-lived, semelparous (i.e. with a single, brief reproductive period) and promiscuous. In the deep, dark habitat where O. deletron lives, potential mates are few and far between. We suggest that same-sex mating behaviour by O. deletron is part of a reproductive strategy that maximizes success by inducing males to indiscriminately and swiftly inseminate every conspecific that they encounter.     

YOLO-Fish: A robust fish detection model to detect fish in realistic underwater environment

Over the last few years, several research works have been performed to monitor fish in the underwater environment aimed for marine research, understanding ocean geography, and primarily for sustainable fisheries. Automating fish identification is very helpful, considering the time and cost of the manual process. However, it can be challenging to differentiate fish from the seabed and fish types from each other due to environmental challenges like low illumination, complex background, high variation in luminosity, free movement of fish, and high diversity of fish species. In this paper, we propose YOLO-Fish, a deep learning based fish detection model. We have proposed two models, YOLO-Fish-1 and YOLO-Fish-2. YOLO-Fish-1 enhances YOLOv3 by fixing the issue of upsampling step sizes of to reduce the misdetection of tiny fish. YOLO-Fish-2 further improves the model by adding Spatial Pyramid Pooling to the first model to add the capability to detect fish appearance in those dynamic environments. To test the models, we introduce two datasets: DeepFish and OzFish. The DeepFish dataset contains around 15k bounding box annotations across 4505 images, where images belong to 20 different fish habitats. The OzFish is another dataset comprised of about 43k bounding box annotations of wide varieties of fish across around 1800 images. YOLO-Fish1 and YOLO-Fish2 achieved average precision of 76.56% and 75.70%, respectively for fish detection in unconstrained real-world marine environments, which is significantly better than YOLOv3. Both of these models are lightweight compared to recent versions of YOLO like YOLOv4, yet the performances are very similar.     

No OTA in fresh cocoa beans

The presence of ochratoxin A (OTA) in cocoa and chocolates has been reported. There is no previously published data available on the source and development of OTA producing moulds and OTA itself in cocoa,i.e. where the mycotoxin enters the cocoa supply chain. A selection of fresh and undamaged cocoa pods from various growing regions was examined for mycotoxin OTA content. In addition, a small selection of damaged or mouldy cocoa pods was included in the examination. It was shown that the ripening phase of healthy cocoa pods from the tree up to being harvested was not a critical period for the occurrence of the mycotoxin OTA. The mycotoxin OTA was not detectable in any of the analysed cocoa pods. Presented at the 28^th Mykotoxin-Workshop, Bydgoszcz, Poland, May 29–31, 2006     

Edible zombis: fresh fish and the industry of cosmetic corpses

Doing research on fishery commodities in Portugal led us to an enigma: for a dead fish to be fresco (fresh) it must be alive. This paradox manifests at a popular, commercial, and legal level. It denotes the interruption of the difference between being dead and being alive in the commodity form. In Portugal, we suggest, the commercialization of peixe fresco (fresh fish) is based on the production and consumption of edible ‘zombis’: seafood corpses technologically and symbolically crafted as undead. An open concept, ‘edible zombis’ is part of an experimental vocabulary that foregrounds the productive agency of undeadness, both biological and commercial, in the seafood economic complex. It relates to the ordinary practice of necromancy in the commodity-based world. Edible zombis are commodity fetishes that fetishize their producers and consumers, suspending them from the capitalist system in which they live.     

Conservation status of the North American fish fauna in fresh water

The status of the North American fish fauna includes 292 species of fishes in the categories of endangered, vulnerable, rare, indeterminate, and extinct. This constitutes 28% of the known fauna. The status of fishes and their habitats continues to decline, especially in the arid regions of western U.S.A. and northern Mexico. The Endangered Species Act is the most powerful tool currently available to protect rare fishes. While many fishes probably have been saved from extinction by this Act, surprisingly few have improved enough to be removed from under its protection.     

One shot,one kill: the forces delivered by archer fish shots to distant targets

Archer fishes are skillful hunters of terrestrial prey, firing jets of water that dislodge insects perched on overhead vegetation. In the current investigation, we sought an answer to the question: are distant targets impractical foraging choices? Targets far from the shooter might not be hit with sufficient force to cause them to fall. However, observations from other investigators show that archer fish fire streams of water that travel in a non-ballistic fashion, which is thought to keep on-target forces high, even to targets that are several body lengths distant from the fish. We presented targets at different distances and investigated three aspects of foraging behavior: (i) on-target forces, (ii) shot velocity, (iii) a two-target choice assay to determine if fish would show any preference for downing closer targets or more distant targets. In general, shots from our fish (Toxotes chatareus) showed a mild decrease (less than 15% on average) in on-target forces at our most distant target offered (5.8 body lengths) with respect to the closest target offered (2.3 body lengths). One individual in our investigation showed slightly, but significantly, greater on-target forces as target distance increased. Forces on the furthest targets offered were found to double that of attachment forces for 200 mg insects, even for individuals whose on-target forces showed mild decreases with increases in target distance. High-speed video analysis of jet impact with the target revealed that the shot was traveling in a non-ballistic manner, even to our most distant target offered, corroborating previous suppositions that on-target forces should remain high. Fish were able to accomplish this without large changes to shot velocity, but we did find evidence that the water jets appeared to differ in the timing of their acceleration as target distance increased. Our two-target choice experiment revealed that fish show preference for downing the closer target first, even though impact forces on distant targets only showed mild decreases. Our overall findings (and the findings of others) suggest that archer fish modulate many aspects of their shooting behavior: from target selection to active control over the water jet that allows the fish to deliver reliably forceful impacts to prey over a wide range of distances.     

Effects of pollutants in fresh waters on European non-salmonid fish I: Non-metals

As part of a programme of acquiring data for preparing standards to safeguard European, nonsalmonid, freshwater fish from pollution, toxicity tests were carried out in hard, well-aerated water. Asymptotic median lethal concentrations (LC50s) of undissociated ammonia, cyanide, nitrite and phenol to one or more of three species were determined. The LC50s were as follows: to common carp 16mg1^-1 as NO₂–N; to perch 0.1 mg1^-1 as HCN; to roach 0.35 mg1^-1 as NH₃-N, 0-11mg1^-1 as HCN, 10.1 mg1^-1 asNO₂-Nand 10mg^-1 as phenol. In order to define these LC50s, exposure periods within the range 0.3 days (phenol) to 14 days (nitrite) were required. Comparisons are made with other data and the tentative water quality 'criteria' proposed by the European Inland Fisheries Advisory Commission.     

Arsenic accumulation in organs of the fresh water fish Tribolodon hakonensis.

The fish Tribolodon hakonensis lives in good health in Lake Usoriko, which has been acidified and naturally contaminated with arsenic by volcanic activities. We have determined the contents of various metals in various fish organs of T. hakonensis, collected at Lake Usoriko. We found that a large amount of arsenic was accumulated in the eye, especially in the choroid-retina part. The arsenic concentrations in the liver and kidneys were about 0.4 microgram/g (wet), whereas the muscle contained less arsenic. The arsenic accumulation in the skin was also observed, especially in the epaxial part. Zinc and arsenic contents in various fish organs correlated well.     

Immunocytochemical localization of taurine in the fish retina under light and dark adaptations

Summary. Previously we have observed the lack of immunoreactivity of taurine in the rod outer segments from light-adapted fish, such as the ayu Plecoglossus altivelis and lefteye flounder Paralichthys olivaceus. This finding prompted us to investigate if there is a difference in the immunocytochemical localization of taurine in the rod outer segments between the dark- and light-adapted states. In the retinas of the glass eel Anguilla japonica and the young goldfish Carassius auratus, extremely intense immunostaining was found in the cone outer segments, rod inner segments, photoreceptor supranuclear region and outer plexiform layer. The rod outer segments were not immunostained in the light-adapted state, while they were intensely immunostained in the dark-adapted state. Consequently, it was suggested that the lack of immunoreactivity in the rod outer segment may depend on light stimulation. In addition, the conspicuous immunocytochemical localization of taurine was discussed with the possible functional roles for taurine in the fish retina. Received January 25, 2000/Accepted January 31, 2000     

Site preference of myxozoans in the kidneys of Hungarian fishes

Myxozoans are common parasites of fish kidneys, with most having specific sites of development. Five specific sites of development include (1) the lumen of renal tubules, (2) the renal corpuscles followed by location in renal tubules, (3) intracellular location within the tubular epithelium followed by a stage in the lumen of the ducts, (4) haematopoietic tissue with dispersed trophozoites, and (5) haematopoietic tissue with large, localized plasmodia. A coelozoic development preceded by presporogonic multiplication characterises most Sphaerospora spp. Early plasmodial stages of Myxidium and Chloromyxum spp. are frequently found in the renal glomerules, while spores develop in the urinary channels in plasmodia released from the renal corpuscles. In Hoferellus and Myxobilatus spp., spores are formed in small plasmodia inside the lumen of the urinary ducts after several internal cleavages in the epithelium of renal tubules. The presence of dispersed trophozoites among haematopoietic tissue cells of the renal interstitium characterises the development of Sphaerospora tincae and Tetracapsuloides bryosalmonae, the causative agent of proliferative kidney disease (PKD). Spores of S. tincae are formed at the place of plasmodial development, while spore formation of PKD is in the renal tubules. A large mass of spores, often surrounded by a connective tissue capsule, can appear in the renal interstitium during infections by several Myxobolus spp.; furthermore, a large number of these spores formed in plasmodia in distant tissues can also accumulate in melano-macrophage centres.     

Orientation in the dark: brain circuits involved in the perception of electric signals in mormyrid electric fish.

Weakly electric fish produce electric signals with a specialised organ in their tail. In addition, they are electrosensitive and can perceive their self-generated signals (for electrolocation) and electric signals of other electric fishes (for electrocommunication). Mormyrids possess three types of peripheral electroreceptor organs, one used for electrocommunication and two types involved in electolocation. They are innervated by afferent fibres, which project to different zones in the electrosensory lateral line lobe (ELL) in the medulla. Brain circuits for electrolocation and electrocommunication are separated almost throughout the whole brain. Electrolocation pathways run from the ELL-cortex to the torus semicircularis of the midbrain and then via the valvula cerebelli towards the telencephalon. Pathways involved in electrocommunication run from the nucleus of the ELL to another part of the torus and from there through the isthmic granule nucleus to the valvula. In addition, a pathway via the preglomerular complex to the telencephalon might exist. In both the electrolocation and the electrocommunication circuits, prominent recurrent pathways are present.     

Echo-sounding can discriminate between fish and macroinvertebrates in fresh water

1. Acoustic scattering from fish and macroinvertebrates was studied in a boreal Finnish lake at three echosounder frequencies (38, 120 and 200 kHz). Split-beam transducers with partly overlapping 7° beams were employed. Acoustic, fish and invertebrate sampling were undertaken simultaneously. Vertical gradients of temperature and oxygen concentration were measured during the exercise.
2. At all frequencies, a narrow scattering layer coincided with the thermocline. At 38 kHz, fish were detected well with practically no reverberation from invertebrates while 200 kHz detected both fish and invertebrates.
3. Minor differences in the magnitude of acoustic scattering from fish were found between frequencies and between depth layers, but scattering at different frequencies was correlated at all depths. Acoustic scattering and fish density indices from trawl catches, consisting mostly of smelt ( Osmerus eperlanus ) (97%) and vendace ( Coregonus albula ) (3%), were significantly correlated.
4. Acoustic scattering from invertebrates increased with sound frequency. Correlation analysis suggested that the invertebrate scattering was mostly induced by Chaoborus flavicans . A low frequency is recommended for estimating fish abundance without bias from reverberation induced by invertebrate scattering. Although fish and invertebrates can also be successfully discriminated at a single frequency by thresholding and cross filtering, the combination of a low and a high frequency is a more robust tool for effective fish-invertebrate discrimination.     

Aminopeptidase from the skeletal muscle of fresh water fish Tilapia mossambica

An aminopeptidase from the skeletal muscle of fish, Tilapia mossambica, was partially purified to 96-fold using salt precipitation, ion-exchange chromatography and molecular sieve chromatography. The enzyme showed optimum activity between pH 6.5-7.5 at 43 degrees C and Vmax and Km of 14.36 units/mg and 0.059 mM respectively with alanine beta-naphthylamide as the substrate. The aminopeptidase having a molecular weight of 305 kDa was activated by sulphydryl compounds and Co2+ and inhibited by bestatin, puromycin and metal chelators. Inhibition caused by metal chelators could be reversed by the addition of Co2+. Inclusion of L-amino acids, particularly isoleucine and leucine, in the assay medium caused inhibition of the enzyme activity. Substrate specificity together with inhibition and activation pattern indicated that the enzyme is alanine aminopeptidase.     

Free imidazole compounds in white and dark muscles of migratory marine fish

1. Extractive nitrogenous components were analyzed in specimens of white and dark muscles of three tunas and the Pacific saury. 2. Tunas contained high concentrations of histidine, anserine and creatine in white muscle, and of taurine, anserine and creatine in dark muscle. 3. Imidazole compounds were determined in both muscles of 11 migratory marine fish. Histidine was found in great quantities in all species except swordfish, anserine was found in relatively large amounts in tunas and swordfish, but carnosine was only present in small amounts in yellowfin and skipjack tunas. 4. The dark muscle had a lower content of imidazole compounds than white muscle.