Continuous Breeder Research Articles

Ecology of fouling bryozoans at Visakhapatnam harbour

Twelve species of bryozoans occur in the fouling communities at Visakhapatnam Harbour, of which the encrusting cheilostome-Electra bengalensis (Stoliczka) is by far the most common. The horizontal distribution of bryozoans at four selected stations in the harbour is recorded. Quantitative data on the seasonal abundance and settlingrates ofE. bengalensis and some of the prevailing hydrographical conditions, i.e. temperature, salinity and turbidity data, are given for one year (December 1966 to November 1967). The observations indicate thatE. bengalensts is a continuous breeder and also a fast growing species. The influence of temperature and salinity on its breeding and abundance is discussed.

Studies on the breeding habits and development of the brood-pouch of a viviparous prosobranch; Melania scabra

Studie son the breeding habits and development of the brood-pouch of a freshwater prosobranch, Melania scabra, have revealed that the snail is ovoviviparous, showing parthenogenetic reproduction. The embryos complete their development in a special incubatory pouch called the brood-pouch or brood chamber, and hatch out in a form completely resembling that of the adult. The snail was found to be a continuous breeder, showing gravid condition throughout the year. General structure, development and functions of the brood-pouch were studied in detail. The brood-pouch was found to contain a slightly alkaline albuminous fluid with a pH 7.2, Qualitative and histochemical studies of the brood-pouch revealed the presence of glycogen, fat and protein as the major constituents. These probably play an important role in the nutrition of embryos.

Quantitative and qualitative aspects of the zooplankton and breeding patterns of copepods at two Caribbean coral reef stations

Zooplankton samples collected in inshore waters overlying similar coral reef areas at Barbados and Jamaica are compared. Although a good correlation exists between zooplankton numbers, wet volumes and dry weight the fluctuations of these variables appear random with no signs of seasonality at either site. Evidence of an ‘island mass’ effect, expressed in terms of zooplankton biomass, is manifested for both islands. The zooplankton quantitative data, plus nutrient and phytoplankton data from previous studies at the same stations, indicate a similar scale of energy conversions at different trophic levels. A species list of the total zooplankton collected off the two islands is presented. Copepods constitute the major faunal component accounting for 84.4% and 76.0% of the total inshore zooplankton at Barbados and Jamaica, respectively. The differences in the order of importance of zooplankton species common to both stations suggest that unknown factors may place constraints on population sizes of these organisms at either locality. Breeding patterns of various copepods are determined. Reproductive activities of the selected species lack synchronization and seasonal regularity. The copepods investigated are classified into two main groups: (a) continuous breeders and (b) sporadic breeders with or without protracted periods of activity. Only one species, Farranula gracilis, is a continuous breeder at both sites, while Clausocalanus furcatus and Paracalanus aculeatus, numerically the most important organisms at Barbados and Jamaica respectively, are sporadic breeders. Miracia efferata is the only copepod expressing any kind of recognizable periodicity. It is suggested that data on egg production may be used as an index to the biotic potential (BP) of a given species.

Regulation of the Annual Testis Cycle by Photoperiod and Temperature in the Lizard Anolis Carolinensis

Males of the lizard Anolis carolinensis are potentially continuous breeders but an annual testicular cycle is induced by seasonal climatic changes. Both photoperiod and temperature are involved as proximate factors in the regulation of testes activity but the importance of each varies with the phase of the cycle. The regenerative phase of spermatogenesis between late fall and spring is controlled primarily by temperature, whereas, the maintenance and eventual regression of the testis in late summer depends primarily on photoperiod. The male reproductive system shows a discrete period of photosensitivity; in nature the lizard shows photo—sexual responses only between late June and mid—October. It is the reduction in day length below about 13.5 hours (the critical day length) in August that induces gonadal regression. The onset and rate of regression is slightly retarded by high temperatures (32 degrees C). The critical day length and temperature dependence of these photoperiodic responses gradually change during the 4—month photosensitive period; and some photorefractoriness is evident early in this period. The factors that determine the onset of the photosensitive phase are poorly understood; short day lengths appear to be important for the termination of this phase. Photoperiod may also affect appetite and growth but these photoperiodic responses differ in several respects from the photo—sexual responses. The two types of photoperiodic responses have different seasonalities, critical day lengths and temperature dependencies. Analysis of the photo—thermal relations of testis activity in A. carolinensis in light of phenological and experimental data for testis cycles in other species indicates that considerable interspecific variation exists in saurian physiological adaptations.

Reproductive and nutritional cycles of the crabPortunus pelagicus (Linnaeus) (Decapoda: Brachyura) of the Madras coast

The gonadal and hepatic indices were determined. Even though the crabPortunus pelagicus is a continuous breeder, there appears to be three maximal periods of development of the gonad and hepatopancreas. The gonad index is high in the months of November-January and June and the hepatic index shows the greatest development in the months of November-January and August. There appears to be a direct relationship between gonadal and hepatopancreatic development. These results have been discussed in the light of previous work.

The Influence of Season on Semen Production in the Domestic Fowl

SINCE the superior breeds and strains of domestic fowl produce eggs throughout the entire year, they have been generally classified as continuous breeders in contrast to non-domesticated fowl which reproduce only during limited portions of the year. Continuous breeding should, however, be more properly described in relative terms, for in most species thus far investigated the intensity or efficiency of reproduction is not constant throughout the year.It has been observed at the Purdue Poultry Farm (Hogue and Schnetzler, 1937) and by poultrymen and hatcherymen throughout the Mid-West that large numbers of infertile hatching eggs are obtained during the late summer and early fall months. McKenzie and Berliner (1937) found that the ram exhibits marked seasonal differences in semen quantity and quality and Erb, Andrews, and Hilton (1942) reported that in the bull, semen quality is significantly superior during the months of April, May, and June and of the poorest .