(Volume 11, March 1999)
RECENT TRENDS IN WATER CLARITY OF LAKE PONTCHARTRAIN
J. C. Francis and M. A. Poirrier
Department of Biological Sciences, University of New Orleans, New Orleans, Louisiana 70148, USA
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-take 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.
EFFECTS OF DIFLUBENZURON ON THE ONTOGENY OF PHOTOTAXIS BY PALAEMONETES PUGIO
J.E.H. Wilson1, R.B. Forward, Jr.2 and J.D. Costlow3
1Department of Biology, Morgan State University, Baltimore, Maryland 21251, USA
2135 Duke Marine Lab Rd., Beaufort, North Carolina 28516, USA
3201 Ann Street, Beaufort, North Carolina 28516, USA
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.
PARASITIZATION OF CALLINECTES RATHBUNAE AND CALLINECTES SAPIDUS BY THE RHIZOCEPHALAN BARNACLE LOXOTHYLACUS TEXANUS IN ALVARADO LAGOON, VERACRUZ, MEXICO
Fernando Alvarez1, Adolfo Gracia2, Rafael Robles1 and Jorge Calderón1
1Colección Nacional de Crustáceos, lnstituto de Biología, Universidad Nacional Autónoma de México, Apartado Postal 70-153, México 04510 D.F., México
2Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, Apartado Postal 70-305, México 04510 D. F., México
Callinectes rathbunae and Callinectes sapidus in Alvarado Lagoon, Mexico, were sampled monthly for one year to determine the extent of parasitization by the rhizocephalan cirripede Loxothylacus texanus. Prevalence levels, host sex ratio, carapace width-weight variation, and distribution of the number of parasites among hosts were analyzed. Loxothylacus texanus was present almost exclusively in C. rathbunae with a mean prevalence of 7.58%, while less than 1% of all C. sapidus were parasitized. Callinectes rathbunae 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 males being parasitized more often, and the comparison of carapace width-weight relationships revealed weights of parasitized crabs.
A SURVEY OF THE REEF-RELATED MEDUSA (CNIDARIA) COMMUNITY IN THE WESTERN CARIBBEAN SEA
E. Suárez-Morales1, L. Segura-Puertas2 and R. Gasca1
1El Colegio de la Frontera Sur-Unidad Chetumal, P.0. Box 424, Chetumal, Quintana Roo 77000, Mexico
2Universidad Nacional Autónoma de México, Instituto de Ciencias del Mar y Limnología, Estación Puerto Morelos, P. 0. Box 1152, Cancún, Quintana Roo 77501, Mexico
The species composition, distribution, and abundance of medusae collected during a 4-day plankton survey in a reef system of the Mexican Caribbean were studied. Highest mean medusae abundance was observed over the fore-reef zone and in daytime samples. Lowest abundances occurred in the reef lagoon and at dusk. Seventeen species were identified, with Liriope tetraphylla, Aglaura hemistoma, Cubaia aphrodite, and Sarsia prolifera being the most abundant. They belong to a group of medusae dominant along the world's second largest barrier reef. Cluster analysis revealed primary (fore-reef) and secondary (reef lagoon, channel) oceanic groups, showing the strong oceanic influence along and across the reef system. Day-to-day variation in the reef medusan community seemed relatively unimportant. The community structure of the reef medusa fauna appeared to be quite uniform despite the expected migratory behavior of these predators, tidal exchange across the reef, introduction of oceanic species, and time of day. The species composition was most closely related to that of the Campeche Bank and oceanic Caribbean waters. Dominance of oceanic medusae within the reef lagoon was attributed to the narrowness of the continental shelf and the mesoscale hydrological features of the zone.
AN ANNOTATED CHECKLIST AND KEY TO HERMIT CRABS OF TAMPA BAY, FLORIDA, AND SURROUNDING WATERS
Karen M. Strasser1 and W. Wayne Price2
1Department of Biology, University of Southwestern Louisiana, Post Office Box 42451, Lafayette, Louisiana 70504-2451, USA, Phone: 318-482-5403, email: firstname.lastname@example.org
2Department of Biology, University of Tampa, Tampa, Florida 33606, USA, Phone: 813-253-3333, email: email@example.com
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.
THE PLANKTONIC COPEPODS OF COASTAL SALINE PONDS OF THE CAYMAN ISLANDS WITH SPECIAL REFERENCE TO THE OCCURRENCE OF MESOCYCLOPS OGUNNUS ONABAMIRO, AN APPARENTLY INTRODUCED AFRO-ASIAN CYCLOPOID
Eduardo Suárez-Morales1, Jerry McLelland2 and Janet Reid3
1El Colegio del a Frontera Sur (ECOSUR).A.P. 424. Chetumal, Quintana Roo 77000, Mexico
2Gulf Coast Research Laboratory, Institute of Marine Sciences, The University of Southern Mississippi, 703 East Beach Drive, Ocean Springs, Mississippi 39564, USA
3National Museum of Natural History, Smithsonian Institution, Department of Invertebrate Zoology, Washington, DC 20560-0163, USA
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.
VARIATIONS IN THE VENTRAL CILIATURE OF THE CRUSTACEAN SYMBIONT HYALOPHYSA (CILIOPHORA, APOSTOMATIDA) FROM MOBILE BAY AND DAUPHIN ISLAND, ALABAMA
Stephen C. Landers, Michael A. Zimlich and Tom Coate
Department of Biological Sciences, Troy State University, Troy, Alabama 36082, USA
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.
GORDON PENNINGTON GUNTER
W. David Burke
Gulf Coast Research Laboratory, Institute of Marine Sciences, The University of Southern Mississippi, 703 East Beach Drive, Ocean Springs, Mississippi 39564, USA
... if you are interested in marine science or any other science, you run along as fast as you can go. Other things
are just an interference, they just take up your time. (Gordon Pennington Gunter)