Paola Zarattini

A preliminary study in the use of RAPD markers in detecting genetic differences in hatching patterns of Chirocephalus diaphanus Prévost, 1803 (Crustacea: Anostraca)

Randomly amplified polymorphic DNA (RAPD) was used to detect intra-clutch genetic differences of the anostracan Chirocephalus diaphanus Prévost, 1803. Thirty primers were tested on 130 nauplii from three different clutches. Two primers produced five repeatable and well-defined amplification products, that were used as genotype markers. Nauplii hatched after three successive dehydration and rehydration cycles. Consistent genetic differentiation was observed among nauplii from the same clutch. Significant association between presence or absence of three polymorphic amplification products and hatching after different stimuli was observed. These results suggest that RAPD markers might be related to the difference in nauplii hatching and provide reasonable support to the hypothesis that the source of the observed variation in hatching phenology are genetic as well as epigenetic.

Further evidence of the synonymy between Branchipus schaefferi and B. visnyai (Crustacea, Anostraca)

Abstract In this study, the systematic position of Branchipus visnyai, recently put into discussion by previous Authors on the basis of merely morphological characters, is reconsidered. The comparison of electrophoretic allozyme patterns between two natural populations of B. visnyai and B. schaefferi from central Italy revealed a very high genetic identity. Thus, the use of allozymic analysis, only rarely applied to Anostraca, indicates that the separation of B. visnyai from B. schaefferi as a distinct species is unfounded.

Life history adaptation of Tanymastix stagnalis (Crustacea, Branchiopoda) to habitat characteristics

Life histories of two populations of Tanymastix stagnalisfrom sites in central Italy, differing in climate and altitude above sea level, were compared to obtain information on the tolerance limits of this species.Temperature was the main factor affecting the biology of Tanymastix stagnalis. Significant differences in growth patterns occurred at different sites. A colder climate induced delayed hatching, slower differentiation and maturation, but a longer life span in the mountain population (Forca Canapine) than in the plain (Fosso dei Mergani).Both populations exhibited an initial fluctuating sex ratio, which later became female biased, a pattern which could be the consequence of adaptation to the unstable nature of the biotopes studied.

Assessing anostracan (Crustacea: Branchiopoda) cyst bank size: An attempt at a standardized method

Egg (cyst) banks play a fundamental role in the survival strategy of the hydrobionts of temporary pools. Therefore a quantitative estimate, as accurate as possible, of their size is the starting point for all the possible considerations concerning the life history of the inhabiting populations. We describe here, in some details, a sampling procedure to evaluate the number of cysts laid by the anostracan Chirocephalus ruffoi Cottarelli & Mura, 1984, in an experimental pool and we show that this procedure results in a good estimate of the cyst bank consistency. A pool 150 cm in diameter was divided into five concentrical rings, 13 cm apart from each other, and a central core (with a 10 cm radius). The number of samples needed to obtain an accurate estimate was calculated by taking into account that, to perform uniform sampling, the total volume of the samples must be proportional to the volume of the pool bed in each ring. The number of cysts in each of the rings was then estimated by considering the mean of the experimental results of a previous study (61 core samples along six transects across the pool itself), multiplied by the number of samples ideally performed in each sector. Evaluating the cyst bank size by the above method resulted in an estimate with an error of only 4% compared to the real cyst bank size. We also show that the number of samples needed can significantly be reduced, with an error on the total number of cysts that can be controlled. This result, that follows from statistical considerations on the confidence interval for the mean, allows us to obtain a general sampling procedure that can be applied to statistically comparable pools.

THE EFFECTS OF FOOD TYPE ON LENGTH-WEIGHT GROWTH, SEXUAL DIFFERENTIATION, AND SURVIVAL IN CHIROCEPHALUS RUFFOI (ANOSTRACA) CULTURED UNDER STANDARD CONDITIONS

Abstract Nauplii of the anostracan Chirocephalus ruffoi were grown until sexual differentiation under standard laboratory conditions (18 ± 1°C temperature; 12L/12D photoperiod; 1600 lux intensity; 200 individuals L−1 density) and fed algae (Selenastrum capricornutum), bakers yeast (Saccharomyces cerevisiae), or a lipid-enriched yeast (Lansy PZ). In parallel experiments, we evaluated survival, development, and increase in body length and weight (wet and dry). Differences among the treatments were analyzed by ANCOVA and Newman-Keuls multiple range tests. The length-weight growth data, log-transformed, were fitted using an orthogonal least squares method. The results show that food type has marked effects on the growth rate and survival of the animals. As previously shown in terms of nutritional effectiveness, enriched yeast produces the best culture results.

Biometrical key-characters for species separation during ontogenesis in fairy shrimps (Crustacea, Anostraca)

Species identification at the larval stage in Anostraca is a major problem, particularly in field studies when two or more species are co-occuring. Investigation into the possibility of telling larval species apart was performed by means of a biometrical study on wild larvae and juveniles of six fairy shrimp species of the genera Chirocephalus, Branchipus and Tanymastix. A total of ten characters and their relationships with body length were analysed within each of the six developmental stages considered. Most of the variables differed significantly (P<0.001) among the taxa examined. Discriminant analysis allowed individuals to be differentiated according to species and to provided evidence of the existence of a few diagnostic traits of use as key-characters.