Peracarida Research Articles

Walrus feeding disturbance: Scavenging habits and recolonization of the Bering Sea benthos

Walruses ( Odobenus rosmarus Illiger) influenced the structure of macrobenthic assemblages in a variety of ways as they excavated their major bivalve prey from soft sediments. Benthic animals were attracted to discarded bivalve shells and they colonized pits and furrows made during prey excavation. Discarded shells contained soft tissues that were eaten by several invertebrate scavengers. The most abundant and widespread scavenger was the sea star, Asterias amurensis Lutken. Sea stars out-competed brittle stars ( Amphiodia craterodmeta Clark) for fresh scavenging events. They also attacked brittle stars under shells in the laboratory, and thus may have obtained two meals from discarded shells by eating remnant tissue and by consuming animals that used the shell as a habitat. In nature, brittle stars were abundant under discarded shells. In experiments, brittle stars invaded shells with soft tissue in the absence of sea stars, but not in their presence. In other experiments, brittle stars were most abundant under shells with soft tissue, but were also attracted to shells without organic matter. Large brittle stars were more abundant under shells than in the surrounding bottom, and the reverse was true of small individuals. Bottom communities recovered gradually inside experimental feeding excavations, which were not invaded by large numbers of opportunistic infaunal or epifaunal invertebrates. This is in contrast to gray whale feeding excavations, which are colonized by a large number of opportunistic peracarid crustaceans.

Mictocaris halope, a new unusual peracaridan crustacean from marine caves on Bermuda

ABSTRACT A new family, Mictocarididae, is proposed for Mictocaris halope, a new genus and species of peracarid crustacean from 4 marine caves on Bermuda. The Mictocarididae do not fit into any known peracaridan order, and a new order, Mictacea, is erected for it and for the Hirsutiidae of Sanders, Hessler, and Garner, 1985 (preceding paper in this journal) by Bowman et al., 1985 (immediately following paper). Mictocaris differs from Hirsutia in possessing eyestalks and a rostrum, an anteriorly rounded labium, marginal setae on the mandibular palp, nonsetose oostegites arising medially, and a pereiopod 2 that is not enlarged.

The endogenous locomotor activity rhythm of four supralittoral peracarid crustace

The ‘strength’ of the endogenous locomotor activity rhythm of four peracarid crustacean species, denned by the precision and persistence of the rhythm, was examined with particular reference to a ‘burrowing’ versus epifaunal supralittoral life-style. The ‘strength’ of the endogenous component of the activity rhythm was also illustrated using a modified periodogram analysis. In all species, the talitrid amphipodsTalitrus saltator, Talorchestia deshayesi, Orchestra gammarellaand the oniscoid isopodLigia oceanica, the laboratory-monitored rhythm and the field emergence pattern displayed a nocturnal, circadian pattern with no clear evidence of any circa-tidal influence. The precision and particularly the persistence of the rhythm of the sand-shore burrowing speciesT. saltatorandT. deshayesiare especially well developed, although a ‘strong’ endogenous component is present in the rhythm of all four species. The significance of the endogenous locomotor rhythms is considered with respect to the supralittoral ecology of the species.

LARVAL ECOLOGY OF MARINE BENTHIC INVERTEBRATES: PALEOBIOLOGICAL IMPLICATIONS

Summary1. Modes of larval development play important roles in the ecology, biogeography, and evolution of marine benthic organisms. Studies of the larval ecology of fossil organisms can contribute greatly to our understanding of such roles by allowing us to race effects on evolutionary time scales.2. Modes of development can be inferred for well preserved molluscan fossils because the size of the initial larval shell (Protoconch I in gastropods, Prodissoconch I in bivalves) reflects egg size. Other morphological criteria are also available, and a comparative approach based on related taxa with known development may be the most reliable method. By combining larval and adult traits, it is possible to recognize modes of larval development in at least some fossil bryozoans, brachiopods, and echinoderms as well. (a) Planktotrophic larvae arise from small eggs, are released in enormous numbers with little parental investment per offspring, and suffer tremendous mortality during and shortly after a planktic existence. These larvae feed on the plankton during development, and are commonly capable of a prolonged free‐swimming existence, and thus wide dispersal. (b) Nonplanktotrophic larvae (which include both planktic lecithotrophic forms and ‘direct developers’) generally arise from large eggs, with relatively few young produced per parent. Relative to planktotrophic larvae, nonplanktotrophic larvae generally receive greater parental investment per larva, and larval mortality is generally lower. These larvae rely on yolk for nutrition during development, and planktic durations are generally much briefer than for species with planktotrophic larvae, so that dispersal capability is considerably less. Energetic investment per egg is generally higher than in planktotrophs, but as there are lower fecundities as well it is difficult to generalize about the total energetic cost of one mode of reproduction against the other.3. Owing to the high dispersal capability of planktotrophic larvae, it has been suggested that species with such larvae will be geographically widespread, geologically long‐ranging, and exhibit low speciation and extinction rates. Species with nonplanktotrophic larvae will tend to be geographically more restricted, geologically short‐ranging, and exhibit high speciation and extinction rates (again, as a consequence of their characteristically low larval dispersal capabilities).4. Recognition of differential dispersal capabilities can play a role in paleobiogeo‐graphic analyses. Concurrent study of the distribution of groups with contrasting modes of development will permit testing of hypotheses concerning timing, magnitudes and frequencies of migration and vicariance events.5. Larval types are not randomly distributed in the oceans, but relationships with other aspects of the organisms' biology and habitats are very complex. Mode of development varies with: (a) Ecology. A simple r–––K model of adaptive strategies is clearly insufficient to explain the observed relationships: while many ‘equilibrium’ species have nonplanktotrophic larvae, and organisms living in less prdictable environments often have planktotrophic larvae, some of the most opportunistic marine species have nonplanktotrophic larvae. Nonetheless, planktotrophic development seems most suited for exploitation of patchy but widespread habitats. (b) Latitude. At shelf depths, planktotrophy is predominant in the tropics, and decreases sharply at high latitudes. (c) Depth. Incidence of planktotrophy decreases with depth across the continental shelf, at least in some taxa. Beyond the shelf, many deep‐sea organisms are nonplanktotrophic (e.g. most bivalves, peracarid crustaceans), but planktotrophic development appears to be present in other groups (prosobranch gastropods, ophiuroids, and bivalves inhabiting transient habitats such as sunken wood and hydrothermal vents).These trends in developmental types will be accompanied by trends in evolutionary rates and patterns as outlined above. The study of larval ecology by paleobiologists will yield insights into the processes that gave rise to ancient evolutionary and biogeographic patterns, and will permit the development and testing of hypotheses on the origins of the patterns observed in modern seas.

DISTRIBUTIONAL ECOLOGY OF AMPHIPODS AND TANAIDACEANS ASSOCIATED WITH THREE SEA GRASS SPECIES

A one-year survey of amphipods and tanaidaceans associated with monospecific sea grass meadows and a bare sand substratum, under similar physical-chemical conditions, showed that the magnozosterid Thalassia testudinum supported higher numbers of peracarids per square meter than the parvozosterid Halodule wrightii and the bare sand substratum as predicted by Kikuchi and Peres (1977). However, when examined in terms of numbers of individuals per unit sea grass biomass or surface area, Thalassia and Halodule supported nearly equal numbers ofepifauna. Syringodiumfiliforme, a syringodiid, consistently supported highest surface area-standardized abundances of epifauna. The previously reported significance of sea grass biomass in structuring crustacean assemblages held within, but not across, sea grass species. Although the amphipods and tanaids showed no species-specific association with sea grasses, the relative abundance of crustaceans was a function of both sea grass species and biomass. Relative abundance of infaunal types decreased from bare sand to Halodule to Syringodium to Thalassia sites and from low to high biomass sites. The abundance of peracarid crustaceans on sea grass meadows is a complex function of sea grass growth form and biomass which appear to mediate the distribution and foraging behavior of important predators. Despite evidence for strong parallelism among the animal communities of sea grass beds in different geographic regions (Ledoyer, 1964, 1969; Kikuchi, 1966, 1974; Nagle, 1968), Kikuchi and Peres (1977) pointed out that different sea grass species take distinct growth forms which affect the quality and nature of the habitat for small animals. Using the classification system of den Hartog (1967), the abundant sea grasses of the eastern United States are divided into magnozosterids (Zostera marina and Thalassia testudinum) with long, wide blades, parvozosterids (Halodule wrightil) with narrow blades, and syringodiids (Syringodium filiforme) with subulate blades. Because of high microhabitat diversity created by the wide blades, Kikuchi and Peres hypothesized that magnozosterids would support animal communities with higher biomass and species diversity than parvozosterids. Few studies have been designed to test for the role of sea grass species in the organization of associated fauna. Such a study requires closely spaced sites in monotypic beds of different sea grass species, all of which are characterized by similar physical-chemical conditions. In cases where conditions of station similarity have been met, significant differences were found in abundance, species composition, and species richness ofpolychaetes (Santos and Simon, 1974), crustaceans (Lewis, 1982), and fishes (Young, 1981; Stoner, in press) associated with different sea grass species. To test the hypothesis that various sea grass growth forms support different abundance and diversity of resident epifaunal organisms, peracaridan crustaceans were collected at seven closely spaced stations in Indian River lagoon, Florida. Three species of sea grass, Thalassia testudinum, Syringodiumfiliforme, and Halodule wrightii, represent the primary growth forms and are abundant in large beds in the lagoon. With care, it was possible to sample monospecific beds and bare sand substrata with similar depth and water conditions. Seasonal collections at the sites allowed an analysis of differences in species composition, faunal abun

Reproductive behavior of three tube-building peracarid crustaceans: the amphipods Jassa falcata and Ampithoe valida and the tanaid Tanais cavolinii

Laboratory observations indicate that Jassa falcata, Ampithoe valida, and Tanais cavolinii have quite similar patterns of behavior: males attend females until ovulation and copulation occur, then the male and female separate. Females tend to remain inside their own tubes, and males tend to move between the tubes of receptive females. This pattern of behavior (called “cruising males”) may be common in crustaceans that exhibit some fidelity to a specific site, especially if the females produce several broods in succession, do not store sperm, and reproduce asynchronously relative to each other. Male J. falcata have a terminal molt which is marked by the presence of a specific sexually dimorphic characteristic, the “thumb” on the second gnathopod. Alternating ovulatory and anovulatory molts occur in T. cavolinii.

Abyssal benthos of the central Indian Ocean

Quantitative studies of the abyssal benthos (3600 to 5300 m) of the central Indian Ocean show a rich fauna and high standing crops. Density of 3 meiofaunal and 12 macrofaunal taxa are large (2175 to 15233; x = 6441 m −2) Polychaetes (41.6%), peracarid crustaceans (31.7%), ophiuroids (12.2%), echiuroid-bryozoa (9.7%), molluscs (4.8%), and agglutinating rhizopod protozoans form the macrofauna. Meiofaunal taxa are nematodes (69.4%), harpacticoid copepods (26.6%), and ostracods (4%). Meiofauna abundances are positively correlated with distance from shore, whereas the distribution and abundance of macrofauna are independent of variations in depth and distance from the shore. Ratio of macro to meiofauna in the total population is 1 to 31. The benthic standing crop is uniformly high (0.54 to 13.73 g m −2; x = 2.70 g m −2) and many times larger than previously reported for comparable depths in other oceans and from the same region. Biomass values are significantly related to distance from shore and the type of substratum. Contribution of macro and meiofauna to the total standing crop was in the ratio of 31 to 1. High benthic biomass and rich fauna are consequences of high organic production in the euphotic zone. The correlation between biomass of the total oxidizable organic matter in the water column and the benthic standing crop is statistically significant ( r = −0.64) at the P < 0.05 level. Rich fauna and high standing crop were associated with the occurrence of polymetallic nodules.

The long-term effects of the Amoco Cadiz oil spill

The supertanker Amoco Cadiz wrecked on the coast of northern Brittany in April 1978. The resulting spill of 223000 t of crude oil polluted some 360 km of rocky or sandy shores, salt marshes and estuaries. An immediate mortality impact was observed. Populations of bivalves, periwinkles, limpets, peracarid crustaceans, heart urchins and sea birds were the most severely affected. Populations of polychaete worms, large crustaceans and coastal fishes were less affected. Three to six generations (5—10 years for bivalves but up to 60 years for birds) may be necessary before populations retrieve their stable age distribution. Delayed effects on mortality, growth and recruitment were still observed up to 3 years after the spill. Estuarine flat fishes and mullets had reduced growth, fecundity and recruitment; they were affected by fin rot disease. Populations of clams and nematodes in the meiofauna declined one year after the spill. Weathered oil is still present in low-energy areas. Species with short life cycles tend to replace long-lived species. A fauna of cirratulid and capitellid polychaete worms now prevails in sandy to m uddy areas. For several clam populations, recruitment remains unstable. Three years after the spill it is still premature to decide how long it will take before populations and ecosystems reach their former or new equilibria.

Two New Leuconids (Peracarida, Cumacea) of Widespread Occurrence in the Deep Atlantic

[Deux especes de Leuconidae (Cumaces), Leucon homorhynchus n. sp. et Paraleucon? hiscens n. sp., provenant des eaux profondes de l'Atlantique est et ouest, sont decrites., Deux especes de Leuconidae (Cumaces), Leucon homorhynchus n. sp. et Paraleucon? hiscens n. sp., provenant des eaux profondes de l'Atlantique est et ouest, sont decrites.]

Patterns of reproduction in the deep-sea benthic crustaceans: a re-evaluation

The reproductive condition of three species of deep-sea peracarid crustaceans, two isopods ( Eurycope californiensis and Ilyarachna profunda), and one amphipod ( Harpiniopsis excavata), was ascertained from a series of sequential seasonal samples obtained at 13-week intervals at 1240m from the same station off San Diego, California, U.S.A. In all three species some females of the population sampled were in brooding condition throughout the year and the data give no reason to suspect seasonal peaks of reproduction. Conclusions from the data are in contrast to previous ones in the literature that seemingly supported cyclic reproduction in deep-sea isopod crustaceans.

Diversity and faunal composition of the deep-sea benthos

Improved techniques have demonstrated a remarkably high species diversity in the deep sea. Long-term environmental stability has resulted in establishment of diverse communities whose species have become biologically accommodated to each other. The deep-sea meiofauna (about 60–500 μm) mainly consists of foraminiferans and nematodes. The macrofauna is dominated by polychaetes, peracarid crustaceans, and bivalves. The major components of the megafauna are brittle stars bathyally, large scavenging fish and amphipods abyssally, and amphipods hadally. Biomass and numerical density decrease rapidly with distance from land. Biomass seems to be of the same order of magnitude for the three size groups, while meiofaunal density in the upper bathyal zone may be up to 1,400 individuals per 10cm2 and macrofaunal density 20,000 individuals per m2.

Durées de la mue, de l'intermue des adultes, et longévité de Stenasellus virei Dollfus (Crustacé Asellote troglobie)

The author’s observations of numerous cases of molting in the hypogean asellid Stenasellus virei Dollfus, 1897 appear to show that the phenomenon occurs in two steps. The loss of the anterior exuvium is separated from that of the posterior exuvium by a period of 8 to 16 days in adults from cavernicolous populations of Stenasellus virei in the Pyrenees and Cantabrian Alps. The intermolts last from 9 to 18 months for the same individuals. One must allow, for this species, a minimun life span of 10 years. Values of the same order of magnitude are anticipated for the two other Pyrenees species, Stenasellus breuili Racovitza, 1924 and Stenasellus buili Remy, 1949. These observations agree with those previously made on other cavernicolous peracarid crustaceans, such as Caecosphaeroma burgundum Dollfus and Niphargus virei Chevreux, by Daum (1954), Husson (1959) and Ginet (1960).

On the diurnal activity of some littoral peracarid crustaceans in the Baltic Sea

A diurnal periodicity in the activity of some peracarids inhabiting seaweeds has been investigated at the Askö Laboratory, the northern Baltic Sea during June–September 1965. The animals were caught semi-quantitatively by sweeping a net over a known distance at the water surface above the algal belts every 3 h. Neomysis vulgaris, Praunus spp., and Idothea spp. were all taken almost exclusively in the catches between 21.00 h and 03.00 h. Of the chief environmental parameters only illumination showed a corresponding variation. Field and laboratory experiments on the influence of light were carried out with Gammarus oceanicus, Idothea baltica and Idothea chelipes. A single specimen per dish was put in Petri dishes containing habitat water and a piece of Fucus and the activity was noted every other hour. In experiments under natural light conditions the activity of Gammarus oceanicus increased significantly when light intensity dropped to a few lux and fell again when values of a few thousand lux were attained. Idothea baltica and Idothea chelipes showed a distinct increase in swimming activity when light intensities fell below one lux and the period of inactivity began at 400–800 lux. In experiments with successive periods of constant dark or constant light all three species were inactive in light, active in dark. The close correlation between field and laboratory responses was further confirmed by light-alternative experiments with Gammarus oceanicus and Idothea baltica: of the two alternatives offered namely 2500–3000 lux and dark, nearly all the 10 individuals of both species chose the dark. This relationship between the activity of the animals and illumination may be of survival value in the presence of a large number of predators, especially fish. Night is very important as being most favourable to large scale dispersal.

A propos de Troglobies vivant dans les eaux d'une mine de fer de Lorraine

Two explorations of the galleries of the Orne-Pauline iron mine at Moyeuvre-Grande (Moselle), made one year apart, resulted in the collection on each occasion of varied and abundant material (5 spp. of peracarid crustaceans and a worm) of aquatic troglobites: 3 spp. of Niphargus, one of which is new to Lorraine (N. kochianus kochianus), 2 spp. of isopods, Asellus cavaticus and Caecosphaeroma burgundum (for which this is the northernmost locality), and finally a local form of Dendrocoelides collini.