Caprellid Amphipods Research Articles

Resource limitation and fish predation: their importance to mobile epifauna associated with JapaneseSargassum.

The possibility that resource limits constrain the growth of mobile epifaunal populations associated withSargassum patens plants was investigated by placing plants and associated animals into field microcosms which excluded fish predators, and then comparing faunal abundance and size-structure changes in different microcosm treatments with field populations. Four different micrososm treatments were set up: two treatments containing defaunated plants inoculated with caprellid amphipods, and two control treatments with natural faunas. The estimated secondary production of faunas enclosed in all microcosm treatments rapidly settled on a constant value (5 mg/day) which was similar to that determined in experiments conducted in Western Australia using the same microcosms but for faunas associated with a seagrass rather than a macroalga. These results support the hypothesis that the secondary production of epifaunal communities associated with macrophytes is constrained by quantifiable food resource ceilings. Predation by the most common fish species in the area, the wrasseHalichoeres tenuispinis, did not appear to alter macrofaunal production in theS. patens bed; however, it did greatly affect the faunal size-structure by eliminating most of the larger animals. The majority of epifaunal animals ≥ 2.0 mm sieve-size were consumed byH. tenuispinis, while negligible numbers of 0.5-mm sieve-size animals were captured. We postulate that food resource ceilings and predatory size-selectivity are widespread phenomena, affecting epifaunal populations at a variety of locations. Predation is predicted to generally increase rather than decrease faunal abundance because the consumption of each large invertebrate by a predator frees sufficient resources to feed several smaller individuals.

Duration and size of embryos in epifaunal amphipods Caprella danilevskii Czerniavski and C. okadai Arimoto (Crustacea:Amphipoda:Caprellidea)

Embryonic duration in two species of epifaunal caprellid amphipods, Caprella danilevskii Czerniavski and Caprella okadai Arimoto, was investigated. The duration decreased from 13 days at 10°C to 3.5 days at 24°C in C. danilevskii and 8.2 days at 12°C to 3.4 days at 24°C in C. okadai. The embryonic duration can be expressed using Belehrádek's equation which indicates “biological zero”, α, at 5.5°C in C. danilevskii and 6°C in C. okadai. The generation period of both species was estimated based on Belehrádek's equation of embryonic development and the generation period at 20°C obtained in our previous studies; 53.2 days at 12°C to 20.8 days at 24°C in C. danilevskii, 54.9 days at 12°C to 20.4 days at 24°C in C. okadai. Embryo size was also noted during field collections; C. danilevskii embryos increased from 0.40 × 0.33 mm in the early stage to 0.46 × 0.37 mm in the late stage and C. okadai from 0.34 × 0.28 mm to 0.37 × 0.30 mm.

Causes and Consequences of Dietary Specialization in Surfperches: Patch Choice and Intraspecific Competition

The existence, causes, and consequences of dietary specialization were explored for a temperate reef fish, striped surfperch (Embiotoca lateralis). Analyses of diets of adults from Santa Cruz Island, California, revealed three dietary regimes within the same population: specialization on caprellid amphipods, specialization on gammarid amphipods, or a mixed (generalized) diet composed of both caprellids and gammarids. Individuals that had specialized on caprellids at the time of capture had obtained a greater intake of prey than did generalists or specialists on gammarids. Different diets were associated with marked differences on body size within most adult year classes; specialists on caprellids were the largest and specialists on gammarids were the smallest for a given age. Generalists were intermediate in size. Females in the different dietary categories were projected to experience different expected lifetime reproductive outputs. Fitness was calculated to be °10% lower for generalists and °20% lower for specialists on gammarids compared with caprellid specialists. The different diets did not arise from active choice of prey taxa, but from selective use of available foraging patches (i.e., types of benthic algae from which prey are harvested). The degree to which an individual fed from the red alga Gelidium robustum was an excellent indicator of the taxonomic composition of its diet. Gelidium was the only alga harboring substantial members of caprellid amphipods; more importantly, it was the most profitable foraging microhabitat. Access to Gelidium was unequal among striped surfperch due to strong interference, and only competitively dominant individuals appeared able to consistently harvest crustaceans from this microhabitat. The least aggressive individual fed from other, less profitable patches that contained mostly gammarid amphipods. "Dietary" specialization was a passive consequence of patch selection dictated by a strong competitive hierarchy, and was not the result of active choice among available types of prey items.

Caprellid amphipods: fast food for the reproductively active

Caprellid amphipod abundance within seagrass meadows of Padilla Bay, Washington, USA, reaches >93 specimens · 625 cm −2 during winter. When shiner perch Cymatogaster aggregata Gibbon invade the seagrass on reproductive migrations, caprellid abundances drop to <2 specimens · 625 cm −2. Although caprellids normally do not constitute a major item in fish diets, shiner perch preferentially preyed upon the caprellids immediately following immigration into the grassbeds. This “critical window” of predation previously has not been reported.

Reproductive Behavior and Sexual Dimorphism of a Caprellid Amphipod

The reproductive sequence of Caprella laeviuscula Mayer consisted of pair formation, female molting, copulation, pair disengagement, and egg laying. The male held the female with the fifth pereiopods during precopula and removed the exoskeleton of the female prior to copulation. The number of eggs carried by the female was a function of female size, and the number of juveniles carried was significantly lower than the number of eggs carried by similarly sized females. Some of the eggs may have functioned as nurse eggs. Cephalon length was determined to be the best character for analysis of sexual dimorphism in this species. Among sexually mature specimens, males had more rapid differential growth of pereionites 1 and 2, while female pereionites 3-7 grew more rapidly. In addition to exhibited growth rates, sexual dimorphism was evident in the brood pouch of females, and in the point of insertion of gnathopod 2. The differences could not be related to male-female reproduction, and sexual dimorphism of males probably is a response to the male-male aggressive interactions during precopulation.

ガラモ葉上ワレカラ類の採集・野外飼育の新手法

ガラモ葉上ワレカラ類の採集・野外飼育の新手法

Aciconula acanthosoma, New Species, a Caprellid Amphipod from Southern California, with Notes on Its Ecology

Aciconula acanthosoma, New Species, a Caprellid Amphipod from Southern California, with Notes on Its Ecology

Relationship between Wave Activity and Robustness of Caprellid Amphipods

Relationship between Wave Activity and Robustness of Caprellid Amphipods

Caprellid amphipod behavior and predatory strikes by fish

Fish predation upon two species of caprellid amphipods was measured in the laboratory with the aid of microcomputer analysis of video-images. This technique allowed determination of prey preferences when the predator was exposed to multiple prey specimens exhibiting multiple prey behaviors. Shiner perch Cymatogaster aggregata (Gibbons) were used as visual predators, Caprella laeviuscula Mayer represented caprellid prey which frequently move, and Deutella californica Mayer represented caprellid prey which seldom move. Time intervals between the release of fish into the test aquarium and predatory strikes were measured during four caprellid behaviors: free in the water column, crawling on hydroids, filter-feeding by pulling the antennae through the water, and remaining stationary. There are three levels of fish selectivity in decreasing importance: 1. (1)fish selected active species over the sedentary species, 2. (2) fish selected caprellids that were overtly moving: swimming > crawling or filtering > stationary, and 3. (3) fish preferentially selected caprellids by size (larger body length).

ACICONULA ACANTHOSOMA, NEW SPECIES, A CAPRELLID AMPHIPOD FROM SOUTHERN CALIFORNIA, WITH NOTES ON ITS ECOLOGY

A caprellid amphipod, Aciconula acanthosoma, new species, is described from nearshore waters of Santa Catalina Island, California. Previously the genus Aciconula was monotypic, known only from the western Pacific species A. miranda. The new species was common and persistent during 15 years of sampling, and was found on 12 types of substrata and in the gut contents of eight species of fishes. It is distinguished from A. miranda primarily by the spination of the head and pereionites. During studies of nearshore marine communities at Santa Catalina Island in southern California, I collected specimens of a caprellid amphipod referable to the genus Aciconula. It was common and persistent from 1973-1988 in samples from a variety of substrata, and in the gut contents of fishes. Subsequent study showed that these specimens differ from the unique type species A. miranda Mayer, 1903, known from six specimens from widely separated localities in the western Pacific Ocean (Arimoto, 1971). The new species is described herein.

Factors affecting Population fluctuations of caprellid amphipods inhabiting &lt;I&gt;Sargassum patens&lt;/I&gt; bed (Preliminary report)

Factors affecting Population fluctuations of caprellid amphipods inhabiting &lt;I&gt;Sargassum patens&lt;/I&gt; bed (Preliminary report)

Feeding Ecology of the Northern Pipefish, Syngnathus fuscus, in a Seagrass Community of the Lower Chesapeake Bay

Examination of gut contents of the northern pipefish,Syngnathus fuscus, revealed that gammarid amphipods, caprellid amphipods, isopods, and calanoid copepods were the dominant food items during the sevenmonth study period.Gammarus mucronatus, calanoid copepods, andErichsonella attenuata were the seasonally dominant prey items in the spring, summer, and fall, respectively.G. mucronatus and calanoid copepods were consumed in approximate proportion to their numerical abundance in the environment, whileE. attenuata, present in rather uniform densities throughout the study period, was extensively consumed only in the late summer and fall. An ontogenetic pattern of prey consumption was evident, in addition to the seasonal pattern. Comparison ofG. mucronatus andE. attenuata size ranges from the field and in pipefish guts revealed thatS. fuscus preyed upon the smaller size classes of each species, and that mean size of prey consumed was positively related to fish size.

STUDIES OF MESOHERBIVORY IN AQUARIA AND IN AN UNBARRICADED MARICULTURE FARM ON THE CHINESE COAST1

ABSTRACTThe effects upon macrophytic and epiphytic algae of caprellid amphipods, including Caprella irregularis Mayer, and of gammarid amphipods, including Ampithoe lacertosa Bate, Jassa falcata (Montagu) and Pontogeneia rostrata Gurjanova, were studied in aquaria and in a coastal mariculture farm near Qingdao, People's Republic of China. The macrophytic species studied included Enteromorpha linza (L.) J. Agardh, Gracilaria asiatica Zhang &amp; Xia, Gracilaria lemaneiformis (Bory) Weber‐van Bosse and Scytosiphon lomentaria (Lyngbye) C. Agardh. These algae and amphipods were selected for study because of their local abundances. Aquarium experiments demonstrated that C. irregularis, J. falcata and P. rostrata feed on ephemeral/epiphytic algae. A. lacertosa (adults and juveniles) ate Gracilaria but preferred E. linza. The different species of amphipods had substantially different patterns of daily activity.Caprellids prevented epiphytic overgrowth of G. asiatica when added to plants in an experimental, openocean, mariculture farm, despite the presence of numerous amphipod predators (e.g. the fishes Hexagrammos otakii Jordan &amp; Starks and Sebastes thompsoni Jordan &amp; Hubbs). Periodic removals of all (naturally colonizing) amphipods from another group of plants in the farm resulted in heavy epiphytic overgrowth. Since these results were obtained in an unbarricaded mariculture farm, we conclude that mesoherbivores may have large effects upon algal community structure in temperate intertidal and subtidal habitats.

Sediment “whips”: Amphipod artefacts from the rocky sublittoral in Britain

Sediment whips are reported attached to hydroids from circalittoral boulder grounds off St. Abbs, Scotland which are thought to be artefacts constructed by the amphipod Dyopedos porrectus Bate. Whips have been photographed in situ supporting primarily Dyopedos, but additionally caprellid amphipods and the arcturid isopod Astacilla longicomis (Sowerby). Under the scanning electron microscope the surface of the whip is seen to be criss-crossed with a meshwork of microfibrils thought to be derived from dactylar secretions of peraeopods 3 and 4 of Dyopedos. These impart significant strength and flexibility to whips underwater. The function of a whip is thought to be that of a vantage point for suspension-feeding.

COMMUNITY INTERACTIONS OF CAPRELLA PENANTIS LEACH (CRUSTACEA: AMPHIPODA) ON SEA WHIPS

Sea whips, Leptogorgia virgulata L., occurring in Thalassia testudinum (Konig) meadows in northwestern Florida support an epifaunal community which is dominated by the caprellid amphipod Caprella penantis Leach. Caprella penantis densities were 23 times greater when T. testudinum died back during the winter than when T. testudinum was more dense. Observations made during seasonal collections indicate that most fish predators of C. penantis are absent during the winter. Caprella penantis densities may have been decreased by fish predation, but the density increases were due to reproductive output. When C. penantis densities on sea whips decreased, postlarval and juvenile decapod crustaceans colonized the sea whip. The reptantians remained on the sea whips through several molts and then dropped from the sea whips to join the benthic macrofaunal community. Epibiotic communities, therefore, have been demonstrated to be involved in at least three important marine ecosystems processes: (1) they serve as a concentrated and recognizable food source for nekton, (2) epibionts graze periphyton and detritus from the biotic substratum, thereby preventing smothering, and (3) some benthic invertebrates temporarily join the epibiotic community during their transition from planktonic to epibenthic life styles. Sessile and sedentary marine macroscopic organisms are common features of marine and estuarine environments, and these organisms act as a substratum for numerous epibiotic organisms (Coe, 1937; Colman, 1939; Dahl, 1948). Dean (1981) correlates species diversity of these epibiotic communities with the structural complexity of the sessile community. He attributes the positive relationship to specific habitat preferences by the epibionts. Logic supports Dean's (1981) suggestion because habitat selectivity by the epibionts is generally attributed to food availability and camouflage (Nagle, 1968; Keith, 1971; Hughes, 1978; Caine, 1979a, 1980). When confined to consideration of fouling organisms that have similar morphology, Dean's (1981) hypothesis also suggests the possible presence of parallel epibiotic communities. Comparison of epibiotic communities of sea grasses indicates that the epibiotic communities are parallel, regardless of the sea grass species (Kikuchi, 1966; Ledoyer, 1966, 1969; Nagle, 1968; Kikuchi and Peres, 1977). Thorson (1955) postulated that parallel communities should function similarly, with analogous species conducting similar activities. The global presence of analogous communities may also indicate similar interactions of the epibiotic communities with their biotic substrata and within their ecosystem. Caprellid amphipods are ubiquitous epibionts which frequently are numerically dominant within epibiotic communities. Studies conducted in Puget Sound, Washington (U.S.A.), which concentrated on activities of caprellid amphipods of the genus Caprella, showed that: (1) sea grass epibionts serve as a food source for surrounding benthic and pelagic communities, especially for juvenile fish, i.e., as nursery grounds (Caine, 1979a), and (2) some epibionts (e.g., Caprella laeviuscula), may remove fouling organisms and detritus from the biotic substratum, thereby preventing smothering of the substratum (Caine, 1980). In this paper I report on activities and community interactions of Caprella penantis Leach from the gorgonian Leptogorgia virgulata L. in northwestern Florida (Gulf of Mexico). My focus was to determine the applicability of the Puget Sound generalities to distant communities.

Three Species of Caprellid Amphipods from Ogasawara Islands, with a Description of a New Species

Three Species of Caprellid Amphipods from Ogasawara Islands, with a Description of a New Species

Observations on the life history of the belted sandfish, Serranus subligarius (Serranidae)

The biology of Serranus subligarius, a typical inhabitant of low limestone reef outcroppings and artificial reefs from North Carolina to Florida and in the northern Gulf of Mexico, was studied on inshore jetties in the northeastern Gulf of Mexico from February 1974 to April 1975. The length-weight relationship was expressed by the equation W = 0.000006L3.431. Growth was greatest in the first year (43.5 mm SL) and declined in the remaining three years of life (17.3, 10.5, and 7.1, respectively). In individuals larger than 40 mm SL, gammaridean and caprellid amphipods were the most numerous food items but crabs, shrimp, and fishes were the most important food items by weight. In individuals less than 40 mm SL, copepods were the most numerous food item, but gammaridean amphipods and shrimp were the most important items by weight. Two incidents of cannibalism were recorded. The ovotestis of the belted sandfish is composed of two lobes which are broadly united posteriorly, with the testicular tissue restricted to a broad band encircling the posterior region of the gonad. Age-group 1 fish are functional synchronous hermaphrodites. Testicular tissue matures in the fall or winter of a fish's first year (all specimens examined histologically, including those from the nonspawning season, contained flagellated spermatozoa) while ovarian tissue matures in the following spring. Spawning season in 1974 extended from late April or early May to September. Crossfertilization is the usual reproductive mode, although individuals are capable of selffertilization.

小田和湾の藻場におけるウミタナゴ類3種の摂餌生態

1) The diet and feeding ecology of embiotocid fishes around Odawa Bay, Kanagawa Prefecture, are examined on the basis of qualitative and quantative analyses of the gut contents. 2) The main food items of the 0+age group is gammarid amphipods in D. viridis, gammarids and caprellid amphipods in D. temmincki and copepods in N. ransonneti. 3) The amount of food intake per body weight is shown to be 2-3% in D. viridis, 2-5% in D. temmincki and 1-4% in N. ransonneti. 4) The seasonal change of the food items utilized by the 0+age group of D. viridis and D. temmincki correspond fairly well to that of relative abundance of phytal animals in the Zostera belt. 5) The 1+age group of D. viridis and D. temmincki utilize a wider variety of types and larger sized food items which are not always predominant in the Zostera belt. 6) The food items of N. ransonneti show no seasonality and N. ransonneti does not seem to depend on phytal animals in the Zostera belt as food resources.

Ecology of two littoral species of caprellid amphipods (Crustacea) from Washington, USA

Ecology of 2 littoral species of caprellid amphipods is compared. Populations of Caprella laeviuscula, a periphyton scraper/filter-feeder, are most dense on eelgrass Zostera marina L. In the absence of C. laeviuscula, periphyton biomass increases 411% in protected Z. marina beds. The light absorption spectra of periphyton and Z. marina are similar, and C. laeviuscula, by its periphyton removal, may allow Z. marina to grow in areas where it would otherwise be excluded. C. laeviuscula is aggressively dominant over sympatric caprellids, and seasonal predators of C. laeviuscula are absent during winter, the period when periphyton would be most limiting to Z. marina. Populations of Deutella californica, a predator, are most dense on the hydroid Obelia dichotoma (L.). In the O. dichotoma epibiotic community, D. californica is the primary predator, but removal did not change the composition of the community structure. In the absence of other macropredators, the structure of the O. dichotoma epibiotic community depends more on the seasonality of O. dichotoma occurrence than on organismal interactions.

Population structures of two species of Caprellid amphipods (Crustacea)

Population structures of Caprella laeviuscula Mayer and Deutella californica Mayer are compared and factors structuring the populations are discussed. Instars were determined by the number of articles in the antennules. The number of D. californica per instar continuously decreased after emergence from the brood pouch. Populations of Caprella laeviuscula had 1. 1) an initial decrease in numbers, 2. 2) an increase in cohort size at middle instars, and 3. 3) decreasing population size. For both species population declines were caused by molting-related deaths. Population structures of C. laeviuscula were also caused by selective predation, intraspecific conflict during amplexus, and by rapidly molting juveniles becoming slow molting as adults. Deviations from a 1 : 1 sex ratio in C. laeviuscula were attributed to selective predation on females. Differences in the age of becoming sexually mature reduce the probability that a chance predator would remove all mature females.