QTL mapping for two commercial traits in farmed saltwater crocodiles (Crocodylus porosus).

The recent generation of a genetic linkage map for the saltwater crocodile (Crocodylus porosus) has now made it possible to carry out the systematic searches necessary for the identification of quantitative trait loci (QTL) affecting traits of economic, as well as evolutionary, importance in crocodilians. In this study, we conducted genome-wide scans for two commercially important traits, inventory head length (which is highly correlated with growth rate) and number of scale rows (SR, a skin quality trait), for the existence of QTL in a commercial population of saltwater crocodiles at Darwin Crocodile Farm, Northern Territory, Australia. To account for the uncommonly large difference in sex-specific recombination rates apparent in the saltwater crocodile, a duel mapping strategy was employed. This strategy employed a sib-pair analysis to take advantage of our full-sib pedigree structure, together with a half-sib analysis to account for, and take advantage of, the large difference in sex-specific recombination frequencies. Using these approaches, two putative QTL regions were identified for SR on linkage group 1 (LG1) at 36 cM, and on LG12 at 0 cM. The QTL identified in this investigation represent the first for a crocodilian and indeed for any non-avian member of the Class Reptilia. Mapping of QTL is an important first step towards the identification of genes and causal mutations for commercially important traits and the development of selection tools for implementation in crocodile breeding programmes for the industry.

Standardized reference ideogram for physical mapping in the saltwater crocodile (Crocodylus porosus).

Basic cytogenetic data, such as diploid number and general chromosome morphology, are available for many reptilian species. Here we present a detailed cytogenetic examination of the saltwater crocodile (Crocodylus porosus) karyotype, including the creation of the first fully annotated G-band standard ideogram for any crocodilian species. The C. porosus karyotype contains macrochromosomes and has a diploid number of 34. This study presents a detailed description of each chromosome, permitting unambiguous chromosome identification. The fully annotated standardized C. porosus ideogram provides the backbone to a standard nomenclature system which can be used to accurately identify specific band locations. Seven microsatellite containing fosmid clones were fluorescently labeled and used as fluorescent in situ hybridization (FISH) probes for physical localization. Chromosome locations for each of these FISH probes were successfully assigned, demonstrating the utility of the fully annotated ideogram for genome mapping.

Dominant inheritance of cleft palate, microstomia and micrognathia--possible linkage to the fragile site at 16q22 (FRA16B).

We report a family in which a father and his three children are affected with microstomia, micrognathia and partial or complete cleft of the hard and soft palate. The probands were non-identical twins, a boy and a girl, both noted to have the above features soon after birth. Their father was diagnosed with a submucous cleft of the palate at the age of 4 years and their older brother has milder facial features and a bifid uvula. All affected family members were demonstrated to have a fragile site on chromosome 16q22 but otherwise normal karyotypes. Of interest is a previously described family with autosomal dominant inheritance of U-shaped cleft palate, microstomia, micrognathia and oligodontia where all affected members were shown to have the fragile site at 16q22 in a proportion of their cells [Bettex et al. (1998) Eur J Pediatr Surg 8:4-8]. We propose that these two conditions are the same and represent a distinctive syndrome involving aberrant orofacial development that may be linked to the fragile site at 16q22.

Ciguatera fish poisoning and fisheries development in the South Pacific Region.

Ciguatera fish poisoning represents an impediment to the development of fisheries based on shallow water reef fish stocks and to the food security of islands where agriculture is limited. Although fisheries development initiatives in the past 20 years in the Pacific have focused on the development of deep slope fisheries and fisheries for large pelagics such as tuna, shallow reef fisheries continue to be a major animal protein source for Pacific Islanders and a source of commercial revenue for fishermen. Statistics on ciguatera outbreaks in the Pacific are limited to local databases in Hawaii and French Polynesia, and to the compilation by the South Pacific Commission of "fish poisonings" reported by the medical departments of the countries of the region. A new database was established at the South Pacific Commission during 1990 to serve as a focus for detailed reporting of fish poisoning and ciguatera in the South Pacific. Some preliminary results from this database are presented and the importance of such information to the development of coastal reef fisheries is discussed.

Multiple exostoses in a patient with t(8;11)(q24.11;p15.5).

The occurrence of multiple exostoses in a carrier of a balanced translocation t(8;11) (q24.11;p15.5) is described. The breakpoint on chromosome 8 is at proximal q24.1 within the critical region reported for Langer-Giedion syndrome.