Margaret Barnes

EGG SIZE, NAUPLIUS SIZE, AND THEIR VARIATION WITH LOCAL, GEOGRAPHICAL, AND SPECIFIC FACTORS IN SOME COMMON CIRRIPEDES

Where possible the eggs, separated from the egg-masses, were measured fresh; when the material had to be preserved Gilsons fluid was used. This helps to break up the egglamellae and, if they are reasonably ripe, eggs are separated on gentle agitation. Ova were shaken out of the ripe ovaries and allowed to round off for 30 min before being measured. Nauplii were measured lying on their dorsal side; for stage I the total length from anterior to posterior and the greatest width of the carapace were measured. The measurements were made under a binocular microscope using a scaled eye-piece which was read to the nearest 0 5 division; the magnification was such that the eggs were about 40 scale divisions, with 1 division -6-0 It. When focusing problems on ellipsoid eggs at higher magnifications are taken into account a moderate magnification of this order seems adequate even though higher magnification may give an appearance of greater accuracy. Where possible at least 200 eggs, obtained by pooling aliquots from a number of individuals, were measured.

Egg numbers, metabolic efficiency of egg production and fecundity; Local and regional variations in a number of common cirripedes

Abstract The various terms which have been used to describe some quantitative parameters of considerable importance in the reproductive cycle of marine invertebrates are discussed; egg number, fecundity and the metabolic efficiency of egg production are defined in a way applicable to animals such as many crustaceans in which the number of eggs produced is a function of adult size. The variation with tidal level and latitude of egg numbers as well as their changes from one season to another are described and discussed for a number of common cirripedes. Local factors may often obscure latitudinal variations. There is no evidence that egg numbers or fecundity are greatest under poor conditions or at the limits of distribution; indeed the reverse seems to be the case. The metabolic efficiency of egg production, namely, the weight of egg tissue produced per unit time per standard increase in body weight is relatively constant for many operculate species even when they are of different adult or different egg size. It follows that fecundity, the number of eggs produced per unit time per standard increase in body size, is largely a function of egg size. The importance of these factors to the ecology of the animals and to their distribution is discussed.

Seasonal changes in the acutely determined oxygen consumption and effect of temperature for three common cirripedes, Balanus balanoides (L.), B. Balanus (L.) and Chthamalus stellatus (Poli)

Abstract The QO2 of three common cirripedes has been measured at four temperatures and on each of four occasions during a year: dissected bodies were used. Statistical analysis indicates that only infrequently is the Q10 weight dependent. Such dependence seems to be related to the nutritional conditions in the environment rather than to the internal state or species habitat. Q10 varies widely even in a given species. In Balanus balanoides there is a marked homeostasis at certain seasons as there is in Chthamalus stellatus at other seasons: Balanus balanus shows somewhat less marked homeostasis. A low Q10 of basal metabolic rate in littoral invertebrates has been observed by others in a variety of animals. The results of some relevant previous work are critically examined and compared with those of the present investigation.

Studies on the reproduction of cirripedes. I. Introduction: Copulation, release of oocytes, and formation of the egg lamellae

Abstract A brief outline is given of the sequence of events leading to the production of egg lamellae in operculate and pedunculate cirripedes. Details are given of the copulatory act as regards random and possibly directed movements of the penis; the question of mutual ‘recognition’ is discussed. The time spent by a spermatozoon in the penis is estimated. The release of ripe oocytes is described and the results of some experiments suggesting the presence of an agent suppressing their release in the earlier stage of maturation are given. It is shown that seminal plasma can induce muscle contractions and the possible significance of this is discussed. The behaviour subsequent to copulation is described. Fully motile spermatozoa are found in the mantle cavity and may be expelled in the mantle cavity current. The bulk of the semen sets to a translucent jelly which is eventually lost from the mantle cavity. The formation of this gel is due to general autolysis. The production, properties, and functions of the egg membranes and the oviducal sac are discussed.

The effect of starvation and feeding on the time of production of egg masses in the boreo-arctic cirripede Balanus balanoides (L.)

Abstract The effect of starvation for various periods and also at various times during the development of the ovaries of Balanus balanoides (L.), followed by feeding, has been investigated. The total feeding time to full maturation shows little variation. The time at which the egg masses are laid down can, however, be to some extent manipulated by controlling the starvation period.

The rate of development of the embryos of Balanus balanoides (L.) from a number of european and American populations and the designation of local races

Abstract A summary is given of the distribution of Balanus balanoides (L.) and of earlier work on differences — racial and otherwise. The variation in the date at which different populations are fertilized is considered. Data are given on the time required for the development of the embryos of this species in vitro at 10 °C, with eggs from a number of populations from the eastern and western Atlantic and examined soon after collection, and also after transplantation and maintenance under ambient laboratory conditions over the next breeding season. Both aspects of reproduction are under genetic control. There is no correlation between the date of fertilization and the time required for development. Oocyte and egg size appear to be largely controlled by temperature. On both sides of the Atlantic there is a general tendency for the time of development to decrease with decreasing latitude. The population at Millport, Scotland appears unusual. The southernmost populations on European shores resemble those at the extreme south in North America. A study of the effect of temperature has shown that at lower temperatures the time of development of the embryos in vitro from all populations tends to be the same; the difference lies in the Q 10 values. The results are discussed relative to palaeontological data and the existence of clines in other features.

The nauplius stages of the cirripede Tetraclita squamosa rufotincta Pilsbry

Abstract The nauplius stages of the cirripede Tetraclita squamosa rufotincta Pilsbry from Elat have been cultured and described. There are the usual six larval stages followed by the cypris but the increase in size during development is small compared with many other species. This small increase compares favourably with other species having very large embryos containing an excess of yolk and which do not take external food during larval development. The setation of the larval appendages is less than in other species and on the antenna and mandible does not increase after stage III. It is suggested that the lack of setation, coupled with a reduced development of the labrum, may be a consequence of the lack of a necessity for this species to feed externally during its planktonic life.

Some cirripedes of the French Atlantic coast

Abstract New records for Elminus modestus Darwin, and a single one for Balanus eburneus Gould are given for the western coast of France. The local population of B. balanoides (L.) at Arcachon (Gironde) has increased in extent and population density over the past few years; a curious growth form of this species — probably resulting from intense competition with Chthamalus stellatus (Poli) — is described.

Studies on the reproduction of cirripedes. II. Setting of the lamellae; action of protease and disintegration of the oviducal sac

Abstract The possible modes of breakdown of the oviducal sac which comes to surround the egg lamellae in cirripedes, has been investigated in a variety of common species. Bacterial action appears to be unimportant. The effect of protease on the sac has been investigated. The rate of breakdown is unrelated to season when it is considered relative to the stage of embryonic development. Apart from Verruca stroemia Muller which is not attacked, the initial rate of ‘dissolution’ is rapid, reaches a minimum, and then increases. Although the time course is similar in all the species examined, there are quantitative differences between species. The differences may only reflect differences in the protein composition of the sac and their resistance to protease. Under the action of its own enzyme species may show much less differences. It is considered that the results indicate that the enzyme necessary for proteolysis is produced by the embryos themselves at a certain stage in their development. The results are discussed relative to other known hatching enzymes.

The general biology of Verruca stroemia (O. F. Müller). V. Effect of feeding, temperature, and light regime on breeding and moulting cycles

Abstract That the absence of breeding in natural populations of Verruca stroemia (O. F. Muller) during the autumn and early winter is due to the absence of food has been confirmed; animals brought into the laboratory and held under ambient light and temperature conditions produce viable egg masses throughout this period when liberally fed. Breeding is not inhibited in either constant light or dark. A temperature of 20°C is lethal even over moderate periods. There is no increase of moulting frequency between 10° and 15°C.