Interactions of Ovary and Hepatopancreas During the Reproductive Cycle of Crangon Crangon (L.).: I. Weight and Volume Relationships

Abstract

Changes in weight and water content of the hepatopancreas and ovary of Crangon crangon are described in relation to body weight and ovarian development. Percentage of water content of the organs in relation to ovarian stage was determined for 43 females; organ wet weight data were obtained from another 137 animals. All stages ofgonadal development (oogenesis, previtellogenesis, vitellogenesis, and depleted) were represented in the sample population of ovigerous, nonovigerous, and postovigerous females. The ovary and hepatopancreas progress through cycles of progressive and retrogressive changes in weight and volume which are characterized by a phase shift between the two organs. This resembles a Volterra-Lotka system, for which equations were derived. Wet weight of the ovary increases by 69% through previtellogenesis, and by 282% from preto secondary vitellogenesis. This represents an increase of 5.5% of body weight occupied by the ovary during development. The hepatopancreas nearly doubles in size from early oogonial development through previtellogenesis, but decreases markedly during vitellogenesis. The net result is an increase from a minimum value of 4% to a combined organ volume occupying 9.5% of total body weight when the ovary is fully vitellogenic. Increase in ovarian mass during development is not due to water increase. Water content decreases from > 70% in immature ovaries to 46% in vitellogenic organs. The hepatopancreas also loses water, but to a lesser extent: from 73% in oogenic individuals to 67% in vitellogenic animals. Female decapod crustaceans progress through a cycle that includes proliferation of gonial cells (gametogenesis), growth of gametes to maturation (gamete production), ovulation and oviposition (egg extrusion), and incubation of embryos until hatching (Sastry, 1983). Numerous papers contain descriptions of various aspects of crustacean reproduction, with emphasis on oogenic and ovarian cycles (see, e.g., Adiyodi and Adiyodi, 1970; Aiken and Waddy, 1980). Quantitative studies of the period and amplitude of ovarian growth of crustaceans are relatively scarce, and even fewer have adequately correlated ovarian development with changes in the hepatopancreas (physically, in terms of mass and water content, and biochemically) (Chang and O'Connor, 1983; Sastry, 1983). Such is the case for the common brown shrimp Crangon crangon, which is exploited commercially in the North Sea (Tiews, 1970). The reproductive cycle of coastal populations has been well documented (Boddeke, 1989), and increase in the size of the ovary during its development has been described (Meredith, 1952). This paper documents changes in weight and water content of the ovary and hepatopancreas relative to ovarian develpment in C. crangon, and derives mathematical equations for the phase shift between the two organs. MATERIALS AND METHODS Specimens of Crangon crangon were collected from the Waddenzee from March through June 1992 and held in an aquarium supplied with running sea water at ambient salinity (n28%oo) and temperature (= 15?C). They were fed frozen shrimp ad libitum until processed. The percentage of water content of the ovary and the hepatopancreas was determined for 43 females. These individuals were blotted dry and weighed to the nearest mg; the ovigerous condition and the presence of egg remnants on the pleopods were noted. The stage of the ovary was identified according to Meredith's (1952) illustrations of size and shape in proportion to the gastric mill and thoracic cavity (Table 1). The ovary and hepatopancreas were removed intact, weighed, dried at 60?C for 16-18 h and weighed again. From these data, the percentage of water content of each organ was determined. Regression equations were derived for the relationships of dry weight to wet weight for the ovary and the hepatopancreas. Wet weights of the entire specimen, ovary, and hepatopancreas were also obtained from another 137 individuals (dry weights were not obtained from these animals). The percentage of the body wet weight (BW)