Search

The mechanoreceptors of land-dwelling juveniles of the family Coenobitidae were studied using scanning electron microscopy to determine how their morphology varied from the mechanoreceptors of the marine dwelling zoea stage. Archived specimens of Birgus latro Leach, 1816 and Coenobita clypeatus Latreille, 1829 from the collections maintained in the National Museum of Natural History, Smithsonian Institution were examined. The mechanoreceptors on the antennules of the planktonic marine larval stage, zoea, are potentially capable of detecting near field sound energy at frequencies two orders of magnitude lower than those of the antennules of the land-dwelling juveniles in both genera. This sensitivity to lower frequencies potentially enables the larval stages to detect sound energy sources at much greater distances.

The effects of illuminance and the location of substrate relative to the water and bottom surfaces on the settlement process in red king crab glaucothoe was studied for the first time. Studies were conducted in the laboratory under natural illumination conditions; propylene fibers were used as a substrate. During the first half of the stage, glaucothoe swam in the water column mostly in the daytime. No daily dynamics in the distribution of glaucothoe were observed. Glaucothoe preferred well-lit substrates near the water surface. When individuals metamorphosed to the first juvenile stage, they migrated from the substrates to the bottom of the tank. [ABSTRACT FROM AUTHOR]

The larval and post-larval behaviour, growth, colour, and morphology of the brown box crab (Lopholithodes foraminatus) are described for the first time based on laboratory reared animals. A detailed morphological description is provided for 4 zoeal stages, the glaucothoe, and the first crab instar. Selected morphological changes over the remainder of the first year of development are also described. Data are presented on larval growth at 11°C and on zoeal stage durations at approximately 8°C, 12°C and 16°C. While the 4 zoeal stages are planktotrophic, the glaucothoe does not feed; a life history character that has been termed ‘secondary lecithotrophy’. Growth of L. foraminatus larvae and post-larvae is generally similar to that of other North Pacific lithodids with planktotrophic zoeae. Zoeal stage durations decrease with increasing temperature. This relationship levels off at approximately 16°C, a higher temperature than in lithodid species from colder regions. Carapace morphology is suggested as a diagnostic character of larval and post-larval stages of Lopholithodes foraminatus. Secondary lecithotrophy may be widespread or even universal among lithodids and also occurs in pagurid hermit crabs. If the family Lithodidae is indeed nested within the Paguridae, as suggested by recent phylogenetic hypotheses based on molecular evidence, secondary lecithotrophy may be plesiomorphic in lithodids. [ABSTRACT FROM PUBLISHER]

Phototactic responses of light-adapted zoeae IV, glaucothoe, and first stage juveniles of the red king crab to three intensities of white light were quantitatively measured under laboratory conditions. All stages observed were photopositive to all light intensities tested, except for late glaucothoe (10 days since moulting) which did not respond to light stimuli. Phototactic response changed in the early life history of the red king crab. The extent of photopositive movement decreased after each metamorphosis. Peak phototactic response in zoea IV were observed at a light intensity of 1.9 × 1013 q cm-2 s-1, in early glaucothoe at 1.1 × 1010 q cm-2 s-1 and in juveniles at 1.3 × 109 q cm-2 s-1. The data on behavioural responses to light may provide a better understanding of the early life history, survival and recruitment of the red king crab and assist the development of feasible methods and techniques for aquaculture of this species. [ABSTRACT FROM AUTHOR]

The development of the larvae of the marine hermit crab Clihanarius clibanarius (Herbst) reared in the laboratory (salinity 34‰±1‰ and temperature 28°C ±1°C) is reported. Four zoeal stages and a glaucothoe were observed during development. Characteristics of the larval stages are described and compared with other known species of this genus. The time taken for development from hatching to glaucothoe is given. [ABSTRACT FROM AUTHOR]

The article presents a study on effect of salinity on the survival of red king crabs at early stage of embryo development and molting. It mentions several stages of development including larvae zoeae, postlarvae glaucothoe and first-stage juvenile crabs. Graphs on the survival rates of early ontogenetic stages, after different level of salinity exposure and long term exposure, are presented.