This paper presents the results from two ring-tests addressing the feasibility, robustness and reproducibility of a reproduction toxicity test with the freshwater gastropod Lymnaea stagnalis (RENILYS strain). Sixteen laboratories (from inexperienced to expert laboratories in mollusc testing) from nine countries participated in these ring-tests. Survival and reproduction were evaluated in L. stagnalis exposed to cadmium, tributyltin, prochloraz and trenbolone according to an OECD draft Test Guideline. In total, 49 datasets were analysed to assess the practicability of the proposed experimental protocol, and to estimate the between-laboratory reproducibility of toxicity endpoint values. The statistical analysis of count data (number of clutches or eggs per individual-day) leading to ECx estimation was specifically developed and automated through a free web-interface. Based on a complementary statistical analysis, the optimal test duration was established and the most sensitive and cost-effective reproduction toxicity endpoint was identified, to be used as the core endpoint. This validation process and the resulting optimized protocol were used to consolidate the OECD Test Guideline for the evaluation of reproductive effects of chemicals in L. stagnalis.

Free-swimming larvae of five perciform species were collected with tow nets in large numbers in Lake Opinicon from May to August of 1969 and 1970. The species appeared in the same seasonal sequence during the 2 yr: first yellow perch (Perca flavescens) followed by logperch (Percina caprodes), black crappies (Pomoxis nigromaculatus), and pumpkinseeds and bluegills (Lepomis gibbosus and L. macrochirus). Peaks of larval abundance, and also hatching, occurred earlier in 1970, when nest-site temperatures from early May to mid-June showed faster lake warm-up than in 1969.

Zooplankton surface samples were taken with a number 12 silk bolting cloth net towed by a Clark-Bumpus quantitative plankton sampler in Narragansett Bay for 12 months. The samples were collected twice weekly, except during December, January, and February, at night at one position in the West Passage of Narragansett Bay. Ten calanoid, three cyclopoid, and one harpacticoid species of free-swimming copepod nauplii were collected from July 1957 through June 1958. The structure and arrangement of elements of the caudal armatures of these copepod nauplii showed certain differences which were utilized to develop a key.

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The open water of two northern Wisconsin lakes was sampled for larval fish at night with fine-mesh conical townets. Those collected were identified to genus or species and enumerated. The majority of larval fish were captured in the limnetic region but a few never strayed from the littoral region.The seasonal changes of the limnetic species were similar for the two lakes and 3 years of study. Their abundance varied greatly from year to year but yellow perch, sunfish, and black crappies always dominated.

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Larval fishes are difficult animals to illustrate for several reasons but it is not necessary to be an accomplished artist to produce acceptable illustrations. Symbolic representations are recommended for illustration of such morphological structures as fin‐rays, thickening tissue in the ventral caudal fin region, yolk materials, and eyes. As general guidelines, we recommend that myomeres be omitted (except for species that possess unusually shaped ones), that three views (dorsal, lateral, ventral) be portrayed, that artistic shading avoided (because it causes confusion with patterns of pigmentation), that illustrations be composed from more than one specimen (when necessary), and that all melanophores be shown accurately because of the importance of pigmentation patterns.

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