Date of Award

Fall 1981

Project Type

Dissertation

Program or Major

Zoology

Degree Name

Doctor of Philosophy

Abstract

The life history, algal preferences and temperature-salinity tolerances of the talitroidean amphipod crustacean, Hyale nilssoni were studied at open coastal and estuarine rocky intertidal shores of New Hampshire. Microhabitat distribution and mouthpart morphology of the sympatric H. nilssoni and H. plumulosa were also compared at Nobska Point, Massachusetts.

Hyale nilssoni was the most abundant algal-inhabiting amphipod at New Hampshire study sites where algal morphology in turn was important for algal species preference. The filamentous alga, Polysiphonia lanosa, was readily consumed and most preferred by H. nilssoni in laboratory and field studies. Laboratory studies showed that in the absence of P. lanosa, H. nilssoni chooses ephemerals over the robust, perennials Fucus spiralis and Ascophyllum nodosum for shelter. Scanning electron microscope examination showed that P. lanosa supported the greatest abundance of epimicrobiota among examined algae. It was suggested that P. lanosa, with its densely and finely branched fronds, offered greater protection from predictors and desiccation.

At Nobska Point, although some microhabitat overlap occurred between H. nilssoni and H. plumulosa, the former was most abundant among fronds of F. spiralis, while the latter was most abundant in sand-gravel. Coloration and substratum preference may be correlated. In the laboratory, little intermingling of the two species occurred and no interspecific pairing of the sexes was observed.

Ultrastructure of the mouthparts indicated that both species are equipped to macerate food material, with the assistance of coarse tooth setae. Hyale plumulosa has had fine tooth setae, and plumose antennae. These antennae could be bent towards the mouth and brushed past the fine tooth setae allowing the ingestion of smaller particles commonly found in the sand-gravel substratum.

Body size of H. nilssoni in New Hampshire habitats differed. Body sizes tended to be inversely related to water temperatures. The smaller estuarine adult size did not deter reproduction between open coastal and estuarine adults. Smaller ovigerous female body size was associated with reduced fecundity. At both New Hampshire locations, spring ovigerous females were larger in size and nurtured larger broods than summer-fall ovigerous females.

Similar body size and fecundity variation were noted at Nobska Point; however, brooding behavior differed between species. In the laboratory, only one brood per female resulted in juveniles for H. nilssoni, while H. plumulosa had up to four broods per female. Timing of juvenile recruitment corresponded with increased water temperature. Hyale nilssoni reproduced in April, while H. plumulosa began reproduction in May. Juveniles of both species occupied algal fronds. Differences in the timing of reproduction might be important in successful co-existence of the species.

Juveniles from open coastal and estuarine habitats did not differ in temperature-salinity tolerance. Survival of juveniles from both habitats at various temperature-salinity combinations was not significantly different as shown by 5-way ANOVA. Survival increased with salinity from 0 to 30('o)/oo, but decreased slightly at 40('o)/oo, and was lower at higher temperatures. Broad environmental tolerance of juveniles would facilitate survival in a variety of habitats.

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