Taxonomic analysis of the copepod specimens collected from 29 Cayman Island ponds revealed the presence of ten species including the nearly ubiquitous cyclopoid Apocyclops panamensis. This species was widespread throughout the islands, being collected at 27 of the sampling sites. Another common calanoid, Mastigodiaptomus nesus, occurred at nine sites on Grand Cayman and one on Cayman Brac. A cyclopoid of Afro-Asian origin, Mesocyclops ogunnus, was collected at two nearly fresh water sites on Grand Cayman and was considered to be a recent introduction. Because of its known adaptability to fluctuating environmental conditions, it is likely that M. ogunnus will successfully compete with and probably displace some of the native species and may become a dominant zooplankter on Grand Cayman.

Apostome ciliates are symbiotic organisms whose life cycles are complex and involve specific feeding, divisional, migratory, and phoretic stages. In this study we examined apostome trophonts (the diagnostic stage) from a variety of crustacean hosts in the Mobile Bay and Dauphin Island, Alabama, area. The hosts were grass shrimp (Palaemonetes pugio and P. paludosus), striped hermit crab (Clibanarius vittatus), blue crab (Callinectes sapidus), and pink shrimp (Farfantepenaeus (=Penaeus) duorarum). A number of similar but distinct morphotypes of apostomes were present, those corresponding to descriptions of species of Hyalophysa as well as variant forms. The morphotypes observed in this study had the following characteristics: variations in the formation of the anterior ventral field of kinetosomes from falciform field 9; variations in the degree to which ciliary row 1 (kinety 1) was separated into 2 segments; and variations in the development of kinety a. A record of the variant morphotypes that do not correspond exactly to an established species should prove useful to biologists attempting to identify apostomes from crustacean molts. We choose not to name the variant forms as new species because they exist as different morphotypes within a population of cells, because some of these types occur in low frequency, and because one of the variant forms changes from one morphotype to another.

The phototaxis by larvae of the grass shrimp Palaemonetes pugio that hatched from embryos which were exposed to a single pulse concentration of diflubenzuron (DFB; Dimilin®) was quantified. Stage IV embryos (6-day-old) were exposed to 0.5 µg/L of DFB for 4 days followed by transfer into clean seawater for the rest of the incubation period. The photoresponses of light-adapted larvae from untreated embryos and embryos treated with 0.5 µg/L DFB were monitored from 1 day through 8 day post hatch for phototactic responses to 500 nm light. Larvae from untreated embryos exhibited strong positive phototaxis at high light intensities (3 x 10-2 and 3 x 10-1 Wm-2) but became negatively phototactic at lower light intensities (3 x 10-5 to 3 x 10-3 Wm-2). This phototactic pattern continued during the monitoring period. On the other hand, larvae from DFB-treated embryos exhibited altered phototaxis for the first 3 days. Alterations were especially evident on Day 1, as larvae were only negatively phototactic. By Day 4, these larvae reverted to the normal pattern of photoresponses shown by untreated larvae. These results indicated that the alterations in photoresponses of larvae caused by embryonic exposure to DFB are only transitory and can be corrected within 4 days of hatching if the larvae are exposed to water lacking DFB.

Fourteen species of hermit crabs, belonging to 5 genera, were identified from 35 stations in Tampa Bay and adjacent continental shelf waters. Ninety-two samples were taken from the intertidal zone to 15 m with a variety of gear including dip nets, trawls, dredges, and hand collections using SCUBA. Pagurus maclaughlinae, Pagurus longicarpus, and Pagurus pollicaris were distributed throughout the bay. These species were often sympatric, and were commonly found in seagrass beds, sandy substrates, and sand/mud substrates, respectively. Clibanarius vittatus, Pagurus gymnodactylus, and Pagurus stimpsoni inhabited the higher salinity waters of the bay entrance. Paguristes sp., Paguristes hummi, Pagurus impressus and Petrochirus diogenes were collected from the lower bay to offshore on hard substrates and sand. Paguristes puncticeps, Paguristes sericeus and Pagurus carolinensis were collected only offshore on hard substrates. The latter species is reported from the Gulf of Mexico for the first time. Isocheles wurdemanni appears to be restricted to high energy beaches. An illustrated key as well as information on distribution, reproductive biology, taxonomic problems, symbionts, and coloration are presented.

Collinecles rathbunae and CalIinectessapEdus in Alvarado Lagoon, Mexico, were sampled monthly for one year to determine the extent of parasitization by the rhizocephalan cirripede Loxofhylucus lemnus. Prevalence levels. host sex ratio, carapace width-weight variation, and distribution of the number of parasites among hosts were analyzed. Loxotlrylocr~s fexanus was present almost exclusively in C. rathbrinoe with a mean prevalcnct of 7.58%. while Iess than 1% of all C. sapidus were parasitized. CalIintctes rofhbunae constitutes a new host record for this parasite. A study of infection revealed significant variation in prevalence and host size throughout the study period. The sex ratio of parasitized crabs differed from that of the total sample with mares being parasitized more often, and the comparison of carapace width-weight relationships revealed Lower weights OF parasitized crabs.

An analysis of Secchi disk transparency observations from 3 sites on the Lake Pontchartrain Causeway indicates that water clarity has increased at the north shore and mid-lake sites, but has not changed at the south shore site. Louisiana Department of Environmental Quality data from 1986 through 1995 were used in the analysis. Further analysis indicates that the increased transparency was not caused by changes in salinity or wind speed. The best explanation for the observed increase is the cessation of shell dredging in 1990.