A comparative study of the sulfhydryl groups in the gastrocnemius of the normal and X-irradiated PET mouse

It has been recognized that hyperpigmentation of the skin is the result of eliminating the. -SH inhibition when treatment is by x-irraidiation. The results of a. study by fieams and Schaeffer indicate : a progressive increase of melanocytes in the skin with an increasing dosage of x-irradiation. However, it was also noted that the effect of x-irradiatin on the gastrocnemius of the PET mouse resulted in a decrease in the number of intramuscular melanocytes. The present study was designed to determine whether the changes in the x-irradiated muscle is related to possible changes in -SH concentration.The technique employed is a quantitative measurement of moles ~SH by azo-aryl mercaptide coupling in the normal and the x-irradiated muscles

Assessment of estuarine habitats for resident and estuarine-dependent species: tools for conservation and management

My research in coastal Ecuador and the northern Gulf of Mexico (GOM) elucidated differences in value of shallow estuarine habitats for fishes and invertebrates. I focused on mangrove and tidal river habitats in Ecuador, and oyster reef, vegetated marsh edge, and nonvegetated bottom habitats in the GOM. Coastal Ecuador has lost 20-30% of mangrove wetlands over the past 30 years. Such habitat loss can impair the ecological functions of wetlands. In this study I identified the fish community of the remaining mangrove wetland in Rio Palmar, Ecuador. For comparison, an adjacent tidal river without mangroves, Rio Javita, was also sampled. I found that although Rios Palmar and Javita are characterized by relatively low fish-species richness compared to other tropical estuarine systems, they appear to provide important habitat for several economically- and ecologically-valued species. In the GOM, I examined the fish and invertebrate communities of adjacent oyster reef (oyster), vegetated marsh edge (VME), and nonvegetated bottom (NVB) habitats. Three main relationships emerged: 1) Oyster and VME provide habitat for significantly more species (as a measure of richness) relative to NVB; 2) Oyster and VME provide habitat for uncommon and rare species; and 3) Many of the species collected in multiple habitats occurred at higher abundances in oyster or VME habitat. Contrary to the current low value ranking of oyster habitat relative to other estuarine and salt marsh habitats, oyster provides high quality habitat for many species. Understanding how key species utilize estuarine habitats is critical for future conservation and management efforts. My research indicated that VME habitat may provide better foraging options for juvenile pinfish (Lagodon rhomboides), and together with corroborating evidence from other studies, suggest that VME provides a critical nursery function for juvenile pinfish, especially in estuaries where seagrass habitat is sparse or nonexistent. Additionally, I documented that juvenile white shrimp (Litopenaeus setiferus) select for oyster habitat because of higher food availability and not because of refuge needs from predation by blue crabs. Oyster habitat appears to provide a nursery function for juvenile white shrimp. Overall, my research demonstrated that structurally complex habitats, such as mangroves, VME, and oyster provide essential habitat at the community, population, and individual levels

Replicated shape variation between simple and complex habitats in two estuarine fishes

A replicated pattern of habitat-associated morphology among different lineages may represent adaptive convergence. Deviation from the replicated (shared) pattern of diversification reflects unique (e.g. species specific) effects resulting from site- or species-specific selection, intrinsic factors (e.g. G matrix differences) or chance historical events (e.g. genetic drift). For two distantly-related estuarine fishes [Lagodon rhomboides (Sparidae; Linnaeus) and Leiostomus xanthurus (Sciaenidae; Lacepede)], we examined shared and unique instances of body shape variation between seagrass (complex) and sand (simple) microhabitats at four sites. We found extensive shape variation between microhabitats for both species. As a shared response, both species from sand had subterminal snouts and long caudal peduncles, whereas those from seagrass had terminal snouts and deep bodies. Unique responses involved a greater difference in Lagodon rhomboides head shape between microhabitats compared to L. xanthurus. Patterns of shape variation fit ecomorphological predictions for foraging in the respective microhabitats (simple versus complex) because deep bodies are expected for fish that must negotiate complex habitats and subterminal snouts facilitate benthic foraging common in barren habitats. Parallel differentiation between microhabitats simultaneously suggests that individuals of each species use a particular microhabitat within estuaries for development and the differentiation in shape represents adaptive convergence. Spatial variation in the magnitude of shape differences between microhabitats was an unexpected finding and suggests that phenotypic variation operates at multiple scales within estuaries

Morphological Diversity of the Cynoscion Group (Perciformes: Sciaenidae) in the Gulf of Guayaquil Region, Ecuador: A Comparative Approach

We assess morphological diversity of species of the Cynoscion group in the Gulf of Guayaquil (GOG) using traditional morphometric methods. Five species from the GOG assemblage (C. albus, C. analis, C. phoxocephalus, C. squamipinnis, and Isopisthus remifer) are compared to four species from a relatively well-studied assemblage in the western Atlantic (C. arenarius, C. nebulosus, C. nothus, and C. regalis). The two regional species assemblages broadly overlap in morphology, but sympatric species segregate relatively well within each assemblage. The GOG species segregate primarily along the major axis of shape variation in the study, which is associated with variation in the anal, second dorsal, and caudal fins. The western Atlantic species segregate primarily along the second major axis of shape variation, which is most strongly associated with variation in gill raker length, and less strongly with pectoral fin length, eye diameter, and length of the third dorsal spine. Patterns of morphological divergence among the western Atlantic species support the hypothesis that morphological divergence is associated with ecological divergence. Comparisons across assemblages indicate that morphological divergence among species in the GOG is substantial. Consequently, Cynoscion species in the GOG may be highly divergent in ecological habits, which would have important management implications, but further ecological research is needed. This study provides a first glimpse into the major patterns of morphological diversification in the Cynoscion group

Puzzling parrotfishes: Radiocarbon age validation and updated longevity estimates for western Atlantic species in support of sustainable fisheries management.

For management efforts to succeed in Caribbean fisheries, local fishers must support and be willing to comply with fishing regulations. This is more likely when fishers are included in a stock assessment process that utilizes robust scientific evidence, collected in collaboration with fishers, to evaluate the health of fish stocks. Caribbean parrotfishes are important contributors to coral reef ecosystem health while also contributing to local fisheries. Scientifically robust stock assessments require regional species-specific information on age-based key life history parameters, derived from fish age estimates. Evaluation of the accuracy of age estimation methods for fish species is a critical initial step in managing species for long-term sustainable harvest. The current study resulted from a collaborative research program between fish biologists and local fishers investigating age, growth, and reproductive biology of the seven parrotfish species landed in U.S. Caribbean fisheries; specifically, we validated age estimation for stoplight parrotfish Sparisoma viride and queen parrotfish Scarus vetula. This is the first study to directly validate age estimation for any parrotfish species through analysis of Δ14C from eye lens cores. Our age estimation validation results show that enumeration of opaque zones from thin sections of sagittal otoliths for a Sparisoma and a Scarus species provides accurate age estimates. The oldest stoplight parrotfish and queen parrotfish in the Δ14C age estimation validation series were 14 y and 16 y; while the oldest stoplight parrotfish and queen parrotfish we aged to-date using the Δ14C validated age estimation method were 20 y and 21 y, respectively. Fish longevity (maximum age attained/life span) is a key life history parameter used for estimation of natural mortality, survivorship, and lifetime reproductive output. Past reviews on parrotfishes from the Pacific and Atlantic concluded that most Caribbean/western Atlantic parrotfish species are relatively short-lived with estimated maximum ages ranging from 3-9 y. However, information from our collaborative research in the U.S. Caribbean combined with recently published age estimates for Brazilian parrotfish species indicate that many western Atlantic parrotfishes are relatively long-lived with several species attaining maximum ages in excess of 20 y