Protogynous hermaphroditism in Chrysoblephus laticeps (Cuvier) and C. cristiceps (Cuvier) (Teleostei: Sparidae)

A histological study of the gonads of two sparid fishes, Chrysoblephus laticeps and C. cristiceps showed that these species are protogynous hermaphrodites. Both species are also monandric in which all males are derived from functional females. Intersexual individuals were restricted to a narrow size range between females and males, and no evidence for simultaneous hermaphroditism was found. Similar to other sparids, the development of the ovary and testis was delimited by a connective tissue layer

Larval development of laboratory-reared carpenter, Argyrozona argyrozona (Pisces: Sparidae)

The larval development of the sparid Argyrozona argyrozona is described and illustrated from 16 individuals, representative of a batch reared in the laboratory from artificially spawned eggs. A general account of development is given as well as detailed descriptions of pigmentation, fin development, head spination, myomere counts and morphometries. The general developmental pattern is similar to other sparids but is unique in regard to preopercular spination, premaxillary and medio-lateral pigmentation and morphometries

The Biology of the bronze bream, Pachymetopon grande (Teleostei: Sparidae) from the south-east Cape coast, South Africa

The biology of the sparid fish, Pachymetopon grande, was investigated from data collected on the southeastern Cape coast between August 1984 and March 1987. Sectioned sagittal otoliths revealed that they are a slow-growing, long-lived species capable of reaching ages in excess of 40 years. Detailed histological examination of gonadal development showed that they are rudimentary hermaphrodites, males and females maturing after a non-functional intersexual stage. The breeding season is restricted to between January and June, and observations suggest that they are group spawners with pelagic eggs. Maturity was reached at 300 mm fork length or approximately 5,5 years old. P.grande is primarily herbivorous, feeding selectively on rhodophytes found on inshore reefs down to approximately 20 m. Minor dietary components included hydrozoans, octocorals and other small invertebrates. Macroalgal degradation by gut endosymbbnts or the utilization of macroalgal epibionts was not evident, suggesting that storage and extracellular carbohydrates of the macroalgae were utilized in the diet. The importance of P.grande to the inshore recreational angling fishery, together with certain aspects of its biology, underline the need for conservation measures aimed at ensuring the sustainability of this resource

Feeding, defaecation and absorption efficiency in the seaurchin, Parechinus angulosus Leske

No Abstract

The subtidal gully fish community of the eastern cape and the role of this habitat as a nursery area

The fish fauna of rocky subtidal gullies between Chelsea Point and Skoenmakerskop (South Africa) was sampled between October 1985 and September 1986 using rotenone to investigate the species composition and the importance of this habitat as a nursery area for marine linefish species. A total of 59 species belonging to 28 families were collected. The majority of these were cryptic fishes such as Clinidae and Cheilodactylidae. Sparidae and Serranidae were represented by juveniles of inshore species. The findings are discussed in relation to previous studies of intertidal pools in the eastern and western Cape, and it is concluded that shallow rocky inter-and infratidal areas are important nursery areas for numerous inshore fishes, including some species caught by recreational line fishermen. The results from this study suggest that previous intertidal studies have over-emphasized the importance of rock pools as nursery areas

Notes on the diet of Rhabdosargus holubi (Steindachner) and Rhabdosargus globiceps (Cuvier) in the marine environment

No Abstrac

Age, growth and feeding of the blue hottentot Pachymetopon aeneum (Pisces: Sparidae) with notes on reproductive biology

The sparid Pachymetopon aeneum is a benthic carnivore feeding predominantly on hydroids, tunicates and octocorals. Juveniles and subadults occur on shallower reefs than the adults but the diet of all sizes is similar. The species is a protogynous hermaphrodite, sex reversal occurring between 200 and 300 mm forklength. Fifty per cent maturity in females occurs between 200 and 250 mm forklength. Peak reproductive activity was recorded between September and March. Otoliths were used to determine growth rate. Growth in length was described by the equation, Lt(mm) = 467,06(1 -e-0,1328(t-0,2473)). The relationship between length and weight, W(g) = 0,00001L(mm)3,149, was used to determine somatic growth as, Wt(g) = 2545,98(1 - e-0, 1328(t-0, 24731))3,149. P. aeneum have a potential for exploitation but the combination of late maturation and protogynous hermaphroditism could lead I to over-exploitation in a size-selective fishery

A preliminary ichthyoplankton survey of the Tsitsikamma National Park

An ichthyoplankton survey using bongo nets was conducted within the Tsitsikamma National Park over an 18-month period between January 1991 and July 1992. Four sampling stations along the coast were chosen, approximately 5 km apart. At each station four samples were taken along a transect perpendicular to the coast, between 0,35 km and 3,8 km offshore. Horizontal tows were taken at three and 15 m below the surface over reef and sand substrata respectively. Larvae belonging to 24 of the 35 families and 55 of the 97 species known to occur in the area were captured. Engraulid larvae completely dominated the catches while amongst the reef-associated taxa sparids and blenniids were prominent. Seasonally occurring cold upwelling events impacted negatively on egg and larval abundance. Mean values for egg and larval abundances were 1207 and 282 per 100 m3 respectively. A relationship between larval number and plankton volume was revealed. Most larvae captured were between 2,0 and 20,3 mm (SL), and in the preflexion condition. The absence of larger size classes in samples was attributed to net avoidance

The audit process and medical organisation

This article has been made available through the Brunel Open Access Publishing Fund and is available from the specified link - Copyright © 1992 BMJ Publishing Group Ltd

Modelling spectral and timing properties of accreting black holes: the hybrid hot flow paradigm

The general picture that emerged by the end of 1990s from a large set of optical and X-ray, spectral and timing data was that the X-rays are produced in the innermost hot part of the accretion flow, while the optical/infrared (OIR) emission is mainly produced by the irradiated outer thin accretion disc. Recent multiwavelength observations of Galactic black hole transients show that the situation is not so simple. Fast variability in the OIR band, OIR excesses above the thermal emission and a complicated interplay between the X-ray and the OIR light curves imply that the OIR emitting region is much more compact. One of the popular hypotheses is that the jet contributes to the OIR emission and even is responsible for the bulk of the X-rays. However, this scenario is largely ad hoc and is in contradiction with many previously established facts. Alternatively, the hot accretion flow, known to be consistent with the X-ray spectral and timing data, is also a viable candidate to produce the OIR radiation. The hot-flow scenario naturally explains the power-law like OIR spectra, fast OIR variability and its complex relation to the X-rays if the hot flow contains non-thermal electrons (even in energetically negligible quantities), which are required by the presence of the MeV tail in Cyg X-1. The presence of non-thermal electrons also lowers the equilibrium electron temperature in the hot flow model to <100 keV, making it more consistent with observations. Here we argue that any viable model should simultaneously explain a large set of spectral and timing data and show that the hybrid (thermal/non-thermal) hot flow model satisfies most of the constraints.Comment: 26 pages, 13 figures. To be published in the Space Science Reviews and as hard cover in the Space Sciences Series of ISSI - The Physics of Accretion on to Black Holes (Springer Publisher