Spinal deformities in a wild line of Poecilia wingei bred in captivity: report of cases and review of the literature

Genes and elements involved in the regulation of the nervous system and growth affect the development of spinal deformity in Cyprinus carpio

Spinal deformity is a serious economic and animal welfare problem in intensive fish farming systems, which will be a significant unsolved problem for the fish sector. The aim of this study was to determine the relative expression of genes (Akt1 substrate 1, Calreticulin, Collagen type I alpha 2 chain, Corticotropin-releasing hormone, Chromodomain-Helicase DNA-binding, Growth hormone, Insulin like growth factor 1, Myostatin, Sine oculis-related homeobox 3, Toll-like receptor 2) in different tissues associated with spinal deformity and to determine the macroelement (calcium, magnesium, phosphorus, potassium, sodium, sulfur) and microelement (barium, copper, iron, manganese, strontium, zinc) content of spine in healthy and deformed common carps (Cyprinus carpio) in Hungary. The mRNA levels of the genes were measured in 7 different tissues (abdominal fat, blood, brain, dorsal muscle, genitals, heart, liver) by qRT-PCR. Correlations between gene expression and element content were analyzed by using linear regression and Spearman rank correlation. In a total of 15 cases, we found a statistically significant connection between gene expression in a tissue and the macro- or microelement content of the spine. In these contexts, the genes Akt1 substrate 1 (3), Collagen type I alpha 2 chain (2), Corticotropin-releasing hormone (4), Insulin-like growth factor 1 (4), and Myostatin (2), the tissue’s blood (3), brain (6), heart (5), and liver (1), the macroelements sodium (4), magnesium (4), phosphorus (1) and sulfur (2) as well as the microelement iron (4) were involved. We also found statistically significant mRNA level differences between healthy and deformed common carps in tissues that were not directly affected by the deformation. Based on our results, genes regulating the nervous system and growth, elements, and tissues are the most associated components in the phenomenon of spinal deformity. With our study, we wish to give direction to and momentum for the exploration of these complex processes.

Axial Skeletal Malformations in Genetically Modified Xenopus laevis and Xenopus tropicalis

Skeletal malformations in captive-bred, adult Xenopus spp., have not previously been reported. Here we describe 10 sexually mature, genetically modified laboratory frogs (6 Xenopus laevis and 4 Xenopus tropicalis) with axial skeletal abnormalities. The young adult frogs were described by veterinary staff as presenting with "hunchbacks," but were otherwise considered to be in good health. All affected frogs were genetically engineered using various techniques: transcription activator-like effector nucleases (TALEN) editing using thyroid hormone receptor α TALEN mRNA, restriction enzyme-mediated integration methods involving insertion of the inducible transgene pCAR/TRDN, or via I-SceI meganuclease transgenesis using either pDRTREdpTR-HS4 or pDPCrtTA-TREG-HS4 plasmid sequences. Radiographic findings (6 frogs) and gross necropsy (10 frogs) revealed vertebral column malformations and sacroiliac deformities that resulted in moderate to severe kyphosis and kyphoscoliosis. These findings were confirmed and additional skeletal abnormalities were identified using computed tomography to create a 3D reconstruction of 4 frogs. Additional findings visible on the 3D reconstructions included incomplete vertebral segmentation, malformed transverse processes, and a short and/or curved urostyle. Histopathologic findings included misshapen intervertebral joints with nonconforming articular surfaces, narrowed joint cavities, flattened or irregularly-formed articular cartilage, irregular maturation lines and nonpolarized chondrocytes, excess fibrocartilage, and evidence of irregular bone resorption and growth. While the specific etiology of the vertebral skeletal abnormalities remains unclear, possibilities include: 1) egg/oocyte physical manipulation (dejellying, microinjection, fertilization, etc.), 2) induction and expression of the transgenes, 3) inactivation (knockout) of existing genes by insertional mutagenesis, or 4) a combination of the above. Furthermore, the possibility of undetected changes in the macro or microenvironment, or a feature of the genetic background of the affected frogs cannot be ruled out.

Evolution in caves: selection from darkness causes spinal deformities in teleost fishes

Only few fish species have successfully colonized subterranean habitats, but the underlying biological constraints associated with this are still poorly understood. Here, we investigated the influence of permanent darkness on spinal-column development in one species (Midas cichlid, Amphilophus citrinellus) with no known cave form, and one (Atlantic molly, Poecilia mexicana) with two phylogenetically young cave forms. Specifically, fish were reared under a normal light : dark cycle or in permanent darkness (both species). We also surveyed wild-caught cave and surface ecotypes of P. mexicana In both species, permanent darkness was associated with significantly higher rates of spinal deformities (especially in A. citrinellus). This suggests strong developmental (intrinsic) constraints on the successful colonization of subterranean environments in teleost fishes and might help explain the relative paucity of cave-adapted lineages. Our results add depth to our understanding of the aspects of selection driving trait divergence and maintaining reproductive isolation in cave faunas.

Physiological effects and reduced tolerance following maternal metal exposure in the live-bearing fish Gambusia affinis

The present study assessed the effects of maternal copper or cadmium exposure in a live-bearing fish. After a 10-d exposure to background levels (control) or 0.15 μM copper or cadmium, gravid females were transferred to clean water. Once a female gave birth, the authors analyzed her newborn offspring for lipid peroxidation, elemental composition (copper, cadmium, and calcium), and metal tolerance. The authors raised other offspring until sexual maturity and analyzed their growth rate, incidence of abnormalities, and sex ratio. Their earlier research, using the same species and exposure design, demonstrated that cadmium and copper were transferred from gravid females to their offspring. The present study showed that offspring of copper-exposed females had a reduced size at birth, developmental abnormalities, elevated tissue cadmium levels, and reduced tissue calcium levels. Offspring of cadmium-exposed females had elevated levels of lipid peroxidation, developmental abnormalities, and lower tissue levels of both copper and calcium. No effects were detected with respect to offsprings' growth rate or sex ratio. Offspring of metal-exposed fish had a reduced tolerance to the metal that their female parent had been exposed to, and the tolerance showed an inverse relationship to the tissue metal level in the offspring. The latter indicates that the reduced tolerance was the result of an increased body burden prior to the tolerance quantification. The present study constitutes the first report in live-bearing fishes showing that maternal metal exposure has a wide range of negative impacts on the offspring.

Pathology survey on a captive-bred colony of the Mexican Goodeid, nearly extinct in the wild, Zoogoneticus tequila (Webb & Miller 1998)

The Mexican Goodeid, Zoogoneticus tequila, is considered nearly extinct in the wild and it is maintained in captivity by the nonprofit international “Goodeid Working Group.” The unique Italian colony has produced about 180 fish so far. The observable diseases were registered and some fish were submitted, immediately after spontaneous death, to necroscopic and histopathologic exams. Encountered diseases included the following: 7 cases of scoliosis (2 males and 5 females); 2 fish with a similar congenital deviation of ocular axis; 1 adult male with left corneal opacity, presumably of traumatic origin; 1 female fish with a large subocular fluid-filled sac, histologically referable to a lymphatic cyst, similarly to the eye sacs of a Goldfish variety (Carassius auratus) called bubble eye; and 1 female fish with recurrent abdominal distension consequent to distal bowel dilation and thinning, associated with complete mucosal atrophy, and comparable to intestinal pseudo-obstruction syndromes described in humans and various animal species. The absence of infectious or parasitic diseases, as well as the low incidence of diseases potentially related to environmental alterations or nutritional disorders such as spinal deformities, suggests the adequacy of breeding management techniques of Z. tequila for its conservation and reintroduction in to the original habitat in the near future.