Rafael Campos-Ramos

Analysis of repetitive DNA sequences in the sex chromosomes of Oreochromis niloticus.

In the Nile tilapia, Oreochromis niloticus, sex determination is primarily genetic, with XX females and XY males. While the X and Y chromosomes (the largest pair) cannot be distinguished in mitotic chromosome spreads, analysis of comparative hybridization of X and Y chromosome derived probes (produced, by microdissection and DOP-PCR, from XX and YY genotypes, respectively) to different genotypes (XX, XY and YY) has demonstrated that sequence differences exist between the sex chromosomes. Here we report the characterization of these probes, showing that a significant proportion of the amplified sequences represent various transposable elements. We further demonstrate that concentrations of a number of these individual elements are found on the sex chromosomes and that the distribution of two such elements differs between the X and Y chromosomes. These findings are discussed in relation to sex chromosome differentiation in O. niloticus and to the changes expected during the early stages of sex chromosome evolution.

CHROMOSOME STUDIES ON THE MARINE SHRIMPS PENAEUS VANNAMEI AND P. CALIFORNIENSIS (DECAPODA)

ABSTRACT Chromosome numbers were obtained from eggs of Penaeus vannamei and Penaeus californiensis,They had 2n = 88 chromosomes. This was confirmed by the haploid chromosome number of n = 44 in testes. No evident karyological difference was observed between these species, in which 4 metacentric, 10 submetacentric, 56 subtelocentric, and 18 acrocentric chromosomes were observed. To obtain mitotic metaphase chromosomes from marine shrimp eggs, 2 methods are described. The effect of colchicine incubation for chromosome condensation was investigated.

Mixture of parthenogenetic and zygogenetic brine shrimp Artemia (Branchiopoda: Anostraca) in commercial cyst lots from Great Salt Lake, UT, USA

The brine shrimp Artemia is one of the most studied animals in the world. A large part of the knowledge of this crustacean is based on cysts harvested from two main sources; the Great Salt Lake, UT (GSL), and the San Francisco Bay salterns, CA (SFB), USA. Artemia populations from these habitats are recognized to belong to a single zygogenetic species, Artemia franciscana Kellogg, 1906. However, the GSL Artemia has been in doubt for more than a century about the existence of parthenogenetic reproduction. By using morphological, reproductive, and molecular analyses, we report that commercial GSL cyst lots contained two different brine shrimp species; a parthenogenetic (60%) and a zygogenetic (A. franciscana) (40%). From this finding, at least three hypotheses can be drawn. The parthenogenetic Artemia is native of GSL, or it was introduced to GSL, or foreign parthenogenetic cysts were mixed with A. franciscana cysts and canned for commercial distribution. Researchers using brine shrimp cysts from GSL should therefore pay careful attention to the correct identity of the species under study. The potential of an easy and unnoticed introduction of parthenogenetic Artemia into America is discussed.

Results of spontaneous spawning of yellow snapper (Lutjanus argentiventris peters, 1869) reared in inland ponds in La Paz, Baja California Sur, México

Maturation and fecundity in two-year cycle of the yellow snapper (Lutjanus argentiventris) was studied as a potential fish-culture species in northwest Mexico. The results of this work will be used in future experiments to control sexual maturation by manipulation of photoperiod and temperature.

Histology of the Androgenic Gland and Expression of the Insulin-like Androgenic Gland Hormone Precursor Gene in the Genital Organ of Pacific White Shrimp Litopenaeus vannamei

The location of the androgenic gland in the genital organ in male Pacific white shrimp Litopenaeus vannamei (Boone, 1931) was analyzed by histology and expression of the insulin-like androgenic gland hormone precursor gene (Lv-IAG). The androgenic gland in L. vannamei is a group of three conspicuous semicircular cellular masses interconnected by cord-like androgenic gland cells, in parallel and attached to the distal vas deferens and terminal ampoule, which form a hook-like morphology. Lv-IAG expression occurs mainly at the terminal ampoule, but also at the distal part of the descending medium vas deferens and the narrow distal vas deferens. These specific regions of Lv-IAG expression basically match the anatomical localization of the androgenic gland observed by histology. The complete cDNA nucleotide sequence of Lv-IAG precursor had 87% to Fenneropenaeus chinensis (Osbeck, 1765), 84% identity to Penaeus monodon Fabricius, 1798 (Pm-IAG), and 82% to Marsupenaeus japonicus (Bate, 1888) (Maj-IAG). The deduced encoding sequence from an open reading frame of 507 bp contained a signal peptide, a B chain, a C peptide, and an A chain that correspond to the androgenic gland insulin-like hormone polypeptide in decapods, where six highly conserved cysteine residues of the A and B chains fold the mature peptide through disulfide bridges. The amino-acid sequence showed high identity to P. monodon (80%), F. chinensis (80%), and M. japonicus (72%), whereas the match to other decapod families Palaemonidae, Parastacidae, and Portunidae was low (24-32%). This study extends our knowledge of the molecular structure of insulin-like peptides related to sex differentiation in malacostraca.

Description of peripheral blood cells and differential blood analysis of captive female and male leopard grouper Mycteroperca rosacea as an approach for diagnosing diseases

The peripheral blood cells and differential blood profile of captive female and male leopard grouper Mycteropercarosacea are described for aquacultural purposes. Basophilic, polychromatic, and orthochromic erythroblasts were observed as immature erythrocytes that develop into mature erythrocytes. Young erythrocytes were not evident, and bi-lobed erythrocytes were extremely scarce. Types of leukocytes included lymphocytes; three types of granulocytes (basophiles, eosinophiles, and neutrophiles); monocytes; and a specialized amoeboid-like macrophage in the blood, which has not been previously described in fish-blood literature. Thrombocytes were commonly observed. There was significantly higher erythropoiesis in males. Granulocytes and lymphocytes of females were significantly higher than males, whereas monocytes and thrombocytes were not.

FIRST REPORT OF GYNANDROMORPHY IN PARTHENOGENETIC ARTEMIA (BRANCHIOPODA: ANOSTRACA)

Abstract We describe three diploid gynandromorphs in Artemia. Two belong to A. parthenogenetica and represent the first report of gynandromorphy for the species. One specimen was a female with a globular brood-pouch and gynandromorphic second antennae, whilst the other was a female with a closed malformed brood-pouch filled with live nauplii, and a long, mobile, penis-like structure projecting from the left side of the genital segments. Offspring from the latter parthenogenetic gynandromorph developed as normal all-female parthenogenetic Artemia. The third gynandromorph belongs to the zygogenetic species A. franciscana, being a female with claspers as previously reported in the same taxon. The occurrence of parthenogenetic gynandromorphs is best explained in light of sex determination mechanisms supporting the view that gynandromorphy might be triggered by a mitotic chromosomal mutation during early embryonic development.

Leukophilia during maturation of the leopard grouper Mycteroperca rosacea

Abstract In spring, peripheral blood of mature-ripe female leopard groupers showed leukophilia after an increase of lymphocytes and thrombocytes, followed by a differential increase of monocytes and granulocytes. In mature-ripe males, granulophilia and thrombophilia were evident. Leukocytes were distinguishable in some ovarian blood vessels where post-ovulatory follicles were present. These observations suggest coordination of endocrine-immune activity, where, after one spawning event, leukocytes infiltrate the gonad tissue from the peripheral blood to aid with immune surveillance and phagocyte activity, while a feedback of sex steroids and vitellogenesis occurs in preparation for the next spawning. An abundance of leukocytes may also aid in gonad reabsorption during post-spawning. Leukophilia coincided with high plasma concentrations of oestradiol and testosterone, which together with leukocytes, decreased greatly in immature-active groupers in summer. Blood cell counts, erythroblasts, and haematocrit of mature-ripe groupers in spring were significantly lower than immature-active groupers in summer, suggesting mild anorexia induced by reproductive behaviour.

Description of Meiosis in Female and Male Pacific White Shrimp Litopenaeus vannamei (Decapoda: Penaeidae)

Abstract The first meiotic prophase was analyzed in both genders of Pacific white shrimp Litopenaeus vannamei. Progression through meiosis, from the formation of the synaptonemal complex to diplotene is described during molting stages. Most of the meiotic cells in both genders were observed at pachytene, recognized by complete synapsis of bivalents. In both genders, the zygotene, pachytene, and diplotene stages occurred at inter-molt, pre-molt, and post-molt stages in all individuals, which suggests that there is no relationship between molting and the first meiotic prophase. Sperm counts from the vas deferens and spermatophores support a continuous production of male gametes. The nature of the synaptonemal complex in gonad cells shows that each pair of homologous chromosomes synapses end to end, revealing a high chromatin density and a complex tangled arrangement in the nucleus. Both genders have 44 bivalents, of which around 40 have an o-ring configuration, and the rest have a v-shape, meaning that most bivalents present chiasmata at both ends, each representing two crossing-over events per bivalent per meiosis.

Simultaneous Germinal Vesicle Migration and Oil Droplet Coalescence Predict Final Oocyte Maturation in the Leopard Grouper

AbstractThe size of oocytes during germinal vesicle migration (GVM) and germinal vesicle breakdown (GVBD) was revised for the Leopard Grouper Mycteroperca rosacea. Histology of ovaries, plasma levels of estradiol-17s (E2), and testosterone (T) were analyzed in Leopard Grouper at 0, 12, 16, and 24 h after a priming dose of 1,000 IU/kg body weight of human chorionic gonadotropin (hCG) and were compared with control females injected with saline solution. Histological observations were verified in hormonally induced females by observing in vivo intraovarian biopsies after using the same priming dose and a second resolving dose of 500 UI/kg body weight of hCG 16 or 24 h later, which served to analyze spawning performance. Histological and in vivo intraovarian biopsies showed that in full-yolk oocytes (~455 μm diameter) GVM and GVBD were concomitant with coalescence of a single oil droplet 16 and 24 h after the first injection. The oil droplet became a morphological marker as well as a predicting indicator of t...