In ecological studies of aquatic organisms which can not be aged directly, the analysis of size frequency distribution of the population is a popular method to reveal the genera-tion structure and some population parameters such as growth rate and survivorship in the population. However, this analysis is time consuming, and requires considerable effort, from preparation of data to calculation of size frequency distribution of each cohort. In the last decade, we have created a software package named PROGEAN (PROgram for GEneration ANalysis) which provides a quick processing environment in the analysis of size frequency distribution with a personal computer. The previous version of PROGEAN (Ver. 3.0, Japanese version for NEC PC9801 series) adopted a graphic method modified from HARDING' S method and required inputting size data of specimen, producing the re-sults of the analysis on the monitor of computer. In this version, PROGEAN Ver. 4. 0, the programs were totally updated with MicroSof t Quick Basic Ver. 4.5 and many functions were added. PROGEAN Ver. 4.0 is made up of 12 subprograms. A data file is created by inputting data from keyboard or graphic digitizer, or importing a text file from other sof twares. On the monitor, a chart of size frequency distribution is created and the results of cohort analysis are plotted on the chart. This chart can be printed with a XY-plotter. Cohort analysis in these programs includes two procedures, analysis of graphic method and optimization of the results produced by the graphic method. These two steps of cohort analysis provide more precise results and easier processing environment of data than the previous version. Two types of programs are available. One is PROGEAN 4. 0J for Japanese domestic personal computers, NEC 9801 series, and the other is PROGEAN 4. 0E for IBM PC/AT and its compatibles with CGA video adapter.

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This paper deals with brachyuran larvae of the families Grapsidae and Ocypodidae collected from the surf zone of Fukiage beach, Kagoshima Prefecture. Descriptions are given of zoea I -II of Hemigrapsus ?sanguineus, zoea I of Sesarminae sp., zoea I -IV of Scopimera ?globosa, zoea I -IV of Ilyoplax ?pusilla, and zoea I of Macrophthalmus sp. Seasonal abundance of these zoeae throughout the 18-month study period showed high concentrations during the summer months (June to August) followed by a steady decline in autumn. The occurrences of successive intermediate zoeal stages of S. ?globosa and I. ?pusilla suggest that the surf zone is a part of nursery ground for the larvae of these two species.

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This paper considers Brachyuran larvae of the families Leucosiidae, Xanthidae and Pinnotheridae collected from the surf zone of Fukiage beach, Kagoshima Prefecture. Descriptions are given of zoea I of Ebalia sp., Xanthinae sp., Pilumnus sp., Pinnotheres, pholadis, and P. ? sinensis. Seasonal abundance of these zoeae throughout the 18-month study period showed high concentrations in the summer months (June to August) followed by a steady decline in autumn. The occurrence of only zoea I in the surf zone suggests that the larvae of these species are transient and not dependent on the surf zone for their development.

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A crangonid shrimp, Argis crassa (RATHBUN, 1899), is reported from Japan for the first time based on the specimens collected from Wakkanai and Usujiri, Hokkaido. The identification is confirmed by the comparison with the Alaskan specimens. The species is characterized by the three acute median spines on the carapace and the presence of a median carina on the first and second abdominal somites.

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In Japan, a small semelid bivalve Theora f ragilis is common in the benthic communities in muddy or muddy sand bottoms of eutrophic semi-enclosed bays. The field populations of this bivalve are often exposed to the water of low dissolved oxygen with hydrogen sulfide during the summer. In this study, the tolerance of T. fragilis to sulfide (H₂S, HS^- and S^2-) was examined in laboratory experiments. Survival time of the bivalve ex-posed to anoxia even with low levels of hydrogen sulfide (mean conc.: 12-15μM; maximum conc.: 40-43μM) tended to become shorter than when exposed to anoxia alone. The lethal time (LT₅₀) was 23 hours in 12μM H₂S at 24.2°C. Survival time decreased further when exposed to moderate or high levels of hydrogen sulfide (mean conc.: 46-778μM; maximum conc.: 84-876μM). LT₅₀ values in these cases were 15.5-40.5 hours at 15.1°C and 15-21 hours at 24.2°C. The results of this study indicate that T. fragilis has a low tolerance to hydrogen sulfide, and suggest that field populations of this bivalve can barely survive under anoxic condition with hydrogen sulfide.

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The habitat, period of occurrence and behavior of Eriocheir japonicus in the sea was described. E. japonicus was collected from various types of sea bottom. The period when E. japonicus appeared in the sea (early September to early July) overlapped with that of small-size brachyurans but for a shorter period with larger migratory brachyurans. E. japonicus was observed not to dig burrows, but to bury itself in the sand or hide under rocks. Many males were collected while wandering, whereas many females were collected while hiding under rocks. Attached organisms (mainly green algae) on the exoskeleton were found more frequently on males than on females, suggesting that males are more active on the bottom than females.

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In coastal and estuarine areas, infauna is known to affect physical, chemical and bio-logical properties of sediment by 'bioturbation', namely its feeding, burrowing, tube building, defecation and ventilation activities. In this paper we briefly review studies of the effects of bioturbation on sediment properties in following aspects, 1) particle size distribution, 2) water content, 3) sediment stability (erodability, resuspension), 4) Eh profile, 5) transportation of solutes and particles, 6) microbial density and activity, 7) biogeochemical activity, and 8) interactions among benthic animals. It has become increasingly clear that physical parameters of sediment are strongly influenced by the lifestyles of resident organisms. Bioturbation has been implicated in both the stabilization and destabilization of sediments. Although biogeochemical activities in the sediments are stimulated by the bioturbation of benthic animals irrespective of their life styles, the mechanism of stimulation differs between construction of macrof aunal semipermanent burrows and mixing of sediment. We suggest the importance of lifestyle of infauna in understanding the effects of bioturbation.

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