Natural History of Two Beach Hoppers of the Genus Orchestoidea (Crustacea: Amphipoda) with Reference to their Complemental Distribution

Abstract

Beach hoppers of the genus Orchestoidea, abundant amphipods of the sandy beaches of central California, all live in similar ecological positions on these shores. In this study, differences mainly between the two large species 0. californiana and 0. corniculata are examined.Competition for burrows between hoppers of the same species is commonly observed. In the early morning hours, large males may be seen fighting for possession of holes left open the night before. Fighting is presumably less energy-consuming than digging a burrow, but since most pugnacity is shown by mature males, possession of a burrow already occupied by a female is also of prime importance. Skirmishes for food items are likewise to be seen.Beach hoppers are eaten by an array of avian predators, mostly diurnal birds, and there is evidence that raccoons, moles, humans, beetles, and other animals take a toll of the hopper populations.Several species of Orchestoidea occur on each of many beaches, but interspecific strife has not been seen often. 0. corniculata sometimes occurs at the ends of beaches otherwise dominated by 0. californian-a, but the reverse situation has never been found. 0. californian-a is a hopper of long, exposed, flat beaches which are made up of quite fine, well-sorted sands. These shores are commonly backed by dunes or possess wide berms into which the animals can retreat. 0. corniculata, on the other hand, is a hopper of short, protected, steep beaches which are made up of fine to coarse, commonly poorly sorted sands. These shores are backed by cliffs or boulder piles preventing escape to the backshore. In the laboratory, individuals of the two species tested for sand size preferences showed 0. californian-a on the average burrowing in finer sand than did the average 0. corniculata. 0. californiana has relatively longer appendages than 0. corniculata. An analysis, however, indicates no appreciable difference between the two species in the relation of weight and length of the main body mass. Measurements of gill volumes indicate that 0. californian-a possesses relatively larger gills.Large 0. californian-a are commonly found in burrows high up on the beach in dry zones relatively far from the reach of the surf, and there they dig holes elliptical in cross section with the entire burrow an open shaft. The sand is actively kicked out onto the surface in two directions. This open burrow, plugged at the top, is used by 0. californian-a perhaps because oxygen does not percolate so well in the fine sand in which these burrows are constructed, and because these hoppers may need a rapid escape to the surface to avoid cutting surf on their exposed beaches. 0. corniculata is never found in the high and dry beach zones; its holes are more nearly circular in cross section; the burrow consists only of an air chamber immediately surrounding the hopper ; and the sand is merely pushed onto the surface in a rounded heap. This type of burrow can be dug in fine or coarse sands.In the laboratory, 0. corniculata dug faster than 0. californian-a i...

Population biology and secondary production of the sandhopper Pseudorchestoidea brasiliensis (Amphipoda:Talitridae) at Prainha Beach, Brazil

“…Aggregation at Stratum 2 could be related to sediment moisture (Williams 1983), although this was not experimentally tested. Bowers (1964) and Behbehani & Croker (1982) related clumped distribution of Orchestoidea corniculata and Orchestja platensis to algae location on the debris line.…”

“…The genus Orchestoidea has been studied by only a few authors: Bowers (1964) described the clumped pattern, nocturnal activity period and reproductive cycle of 0. californiana and 0. corniculata. Craig (1971Craig ( , 1973a observed the behavioral activity, spatlal distribution along shore and lunar orientation of 0. corniculata, while Duarte (1974) investigated the feeding behavior of 0. tuberculata on the Chilean coast.…”

Zonation by size in the Armandia sp. (Polychaeta: Opheliidae) population on an intertidal sand flat

“…In the case of the diffusion of mobile benthos, such a trial-and-error diffusion process may be common (e.g. Wieser 1956, Bowers 1964, Meadows 1964, Gray 1971, Ravenel &Thistle 1981, Wilson 1983. Tamaki (1984a) found through a laboratory experiment that the activity of C. japonica can also be beneficial to Armandia individuals by conditioning the properties of sediment (e.g.…”

“…However, most of the investigations were either for crustaceans (e.g. Bowers 1964, Trevallion et al 1970, Glynn et al 1975, Wooldridge 1981, Haley 1982, Wada 1983 or for molluscs (e.g. Edwards 1969, Ansell & Legard&re 1980, Leber 1982, Berry & Othman 1983, Nishino et al 1983, Price 1984; studies relating to polychaetes, the other constituent of the 3 major taxonomic groups of macrofauna, are few (e.g.…”

Das Schwimmen der Talitridae (Crustacea, Amphipoda): Funktionsmorphologie, Phänomenologie und Energetik

“…Allgemein gelten die Talitridae, verglichen mit ancteren Amphipoden wie z.B. Gammarus, als schlechte Schwimmer (Gerstaecker & Ortmann, 1901;Smallwood, 1903Smallwood, , 1905Mortensen, 1921;Schlienz, 1922;Dudich, 1927;Dahl, 1946;Bowers, 1964). Talitrus eastwoodae kann sich unter Wasser nicht einmal mehr vom Untergrund abheben (Lawrence, 1953), und Talitrus saltator soll sich nur durch gemeinsame Anstrengung der Pleopoden und des ganzen Abdomens gerade noch "... schwebend erhalten..." k6nnen (Schellenberg, 1929(Schellenberg, , 1942; dagegen gibt Verwey (1927) ffir T. saltator (K6rperl~inge ca.…”