Scorn. 1975. Macroinfauna of northern New Eneland marine sand. 11. Amphi+-dominated intettidd communities. Can. J. h l . 53: 42-51.Tbi: is a 5.year study of macroinfaunal communities of moderately exposed to sheltered intert~dal sands OF New Hampshire nnd southwestern Mame. Habitats also differed in slope, width, predominant sand grain size, and carbon-nitrogen concentrations. Thirty-one species were recorded. Abundance and dry we~ght biomass at four intensively st~tdied habltats averaged 50M/rnz and 2.1 glmz. respect~vely, durlng 1971. The most exposed habitat yielded rwice thls prksence de six esptces d'amphipdes. la plupan der Hausroriidac. don1 la longivitt est relativernent courte. 1-8 variation dans I'ahondance et la biomasse des amphipodes err plus g m d e d'un habitat i I'autre que d'une saison i I'autre au sein du msme habitat. Leq espkces de folychete:. sont plus nombreuses dans les hahifats prorbg.5~ et les moltusques bivalves sont tmrtis aux zones abritees. Ln comrnunautk typique deq sables exposis moder6ment, dans le Maine, au sud de la baie de Penohscot, esr caractkrisie par un proupe recurrent de neuf espkces (cinq arnphipdes). La stabilire de la cornmunautk depend, en partie. des habitudes reproauctrices des arnphtpodcc dominant<. tn discussion pone sur la zonation, les rapports avec In zone suh-tidale, Its mouvemenrs saisonnlers. enfin, les modes de dominance des espkces d'amphi-W e s . Onttablir Cgalement certainescomparaisons struc~urales avec des carnrnuna~~tes boniales europeennes ainbi quc d'autres cornmunaues habatant les sables de la zone ~ntertidaie de la cbte Atlantique.[Traduil par le jo~~rnall

Amphiporeia virginiana occurs from Nova Scotia to South Carolina where it is a dominant inhabitant of high energy sand beaches. Maximum abundance occurs on the lower foreshore in fine sand particularly during summer months. Within-habitat segregation of sexes occurs, with females more abundant at higher beach levels; ovigerous females are confined to higher levels only. Annual population fluctuations of up to 14-fold on a geometric basis are related to life history events and sedimentary changes. Breeding occurs during most of the year with peak recruitment during June and late summer to early fall, yielding summer and overwintering generations. Precopulating animals are commonly seen swimming, with two males per female occasionally evident. Females produce a mean of 6–11 eggs during the year and have one brood per breeding period. The species is a detritivore and generally inhabits the upper 2.5 cm of sand. It is most tolerant of salinities in the range of 25–35‰; mortality increases rapidly in salinities less than 20‰, and in sediments containing less than 11% water by weight exposed to temperatures simulating hot summer days.

HAGER, R. P., and R. A. CROKER. 1980. The sand-burrowing amphipod Amphiporeia virginiana Shoemaker 1933 in the tidal plankton. Can. J. Zool. 58: 860-864. The abundance of Amphiporeia virginiana in the tidal plankton over a high energy sandy shore in southern Maine increased to maximum values 1 to 1.4 m above mean low water(MLW) with no clear evidence of a diurnal cycle affecting swimming activity. The species undergoes daily tidal migrations over the shore with swimming activity increasing just before high tide and generally peakingduringebbing tides. Results of experiments withlaboratory-held animals supported these conclusions, although swimming rhythms disappeared rapidly after 24h in the laboratory. The swimming behavior of the species assists reproductive contact of sexes that are segregated in the sand, contributes to short-term fluctuations in distribution and abundance, and assists the species in maintaining dominance on high energy sandy shores.HAGER, R. P., et R. A. CROKER. 1980. The sand-burrowing amphipod Amphiporeia virginiana Shoemaker 1933 in the tidal plankton. Can. J. Zool. 58: 860-864. L'abondance d'Amphiporeia virginiana dans le plancton de maree, sur une rive sablonneuse a grand budget energetique du sud du Maine, augmente pour atteindre des valeurs maximales a 1-1.4 m au-dessus du niveau moyen d'eau basse; aucun cycle diurne particulier ne semble &re responsable de I'activite de nage. L'espece fait des migrations de maree tous les jours sur la rive; I'activite de nage se met a augmenterjuste avant la maree haute pour generalement atteindre un sommet durant les marees descendantes. Les resultats en laboratoire sur des animaux experimentaux corroborent ces conclusions, bien que les cycles de nage disparaissent rapidement apres 24 h en laboratoire. Chez cette espece, le comportement de nage sert a rapprocher les sexes pour la reproduction, contribue aux fluctuations a court terme de distribution et d'abondance et permet a I'espece de rester dominante sur les rives sablonneuses a budget energetique elevt.[Traduit par le journal] IntroductionIn a recent paper, we described the infaunal ecology and life history of Amphiporeia virginiana, the dominant intertidal sand beach amphipod in northern New England (Hager and Croker 1979). This haustoriid displays considerably more swimming behavior and less affinity for the substratum than other related infaunal amphipod species in New England. Distributional patterns and population fluctuations are related to life history events, as well as to dispersal of the species correlated with sediment changes. These phenomena are pronounced on high energy sand beaches, a habitat where A. virginiana is frequently the only crustacean present. Our objective was to examine the behavior of A . virginiana in the tidal plankton, and to determine the effect that swimming behavior may have on infaunal distribution and abundance.