Temporary Freshwater Research Articles

Effet de certains paramètres physico-chimiques sur les relations prédateurs–proies dans les populations de copépodes cyclopoïdes des mares temporaires d'eau douce

Copepod populations of three temporary freshwater pools (Alnus unit, Carex unit, and Molinia unit) were studied using a standard approach (species versus abiotic factors) and a holistic one (body size and feeding ecology). Multiple regression analyses of data indicate that the physical and chemical features of water (temperature, pH, dissolved oxygen, mineral content, and depth) explain 62 to 98% of the variability of carnivorous copepods, while the abundance of their prey accounts for much less. No size class of prey seems to be preferred. The abundance of decaying organic matter, typical of such pools, would result in an overabundance of prey. Predators would then be under the control of nonalimentary factors.

Feeding Structures of Two Atyid Shrimps, with Comments on Caridean Phylogeny

ABSTRACT Atyainnocous and Potimirim glabra (Atyidae) occur in permanent and temporary freshwater streams in the Atlantic and Pacific drainages of Panama. Their mouthparts, mandibles, and foreguts are compared to test the hypothesis that these structures are related to diet. Atya innocous occurs in moderate to fast-flowing streams, feeding on minute particles collected from the water column or bottom. Potimirim glabra inhabits quiet pools, scraping periphyton from leaf surfaces and decaying organic detritus. The feeding appendages of both species arc modified for handling fine particles of food. The mandibles have a strong incisor process but are not used for crushing large food items. The primitive nature of the mandible and foregut suggests the placement of the family Atyidae at the base of the caridean evolutionary tree. The use of the foregut in the construction of phylogenies within the Decapoda is discussed.

Hatching conditions for Eocyzicus spinifer (Conchostraca:Crustacea) from Iraq

Some ecological aspects of Eocyzicus spinifer collected from a temporary freshwater pond near Baghdad are described. Physical and chemical variables of the pond are given. The relationship between age and growth of both sexes under laboratory conditions are documented.

Population differences in the timing of diapause: adaptation in a spatially heterogeneous environment.

Populations of the planktonic copepod, Diaptomus sanguineus, live in permanent and temporary freshwater ponds in Rhode Island. All ponds in which they occur become uninhabitable at some time during the year, but the nature and timing of the harsh period varies both spatially and temporally. Females produce discrete clutches either of subitaneous eggs which hatch immediately or of diapausing eggs which hatch the following season. The two egg types show distinct chorion morphologies under transmission electron microscopy. In permanent ponds the copepods start making diapausing eggs in March, one month before rising water temperatures induce planktivorous sunfish to become active. In temporary ponds diapausing eggs are produced, in a complex pattern from May to July, before the water disappears in late summer or early fall.We investigated the spatial scale at which D. sanguineus is adapted to this complex environment. In a reciprocal transfer experiment between temporary and permanent bodies of water, female copepods placed in new ponds made subies of water, female copepods placed in new ponds made subitaneous and diapausing eggs in the same sequence as control females retained in their home ponds. The copepod populations enter diapause at times appropriate for the local habitat conditions they experience, but inappropriate for other, nearby ponds. Transplanted females were unable to sense a change in pond type or to adjust egg production accordingly. We conclude that D. sanguineus populations are adapted to the specific conditions of isolated ponds rather than to a broader geographical region containing several pond types.

Effect of Temperature and Body Size on Oxygen Consumption of Two Species of Eubranchipus (Crustacea: Anostraca)

Oxygen consumption of Eubranchzpus vernalis and E. holmani was measured between 4 C and 20 C on a Gilson Differential Respirometer. Qjo values and the relationship between weight-specific oxygen consumption and temperature indicated that individuals of E. holmani and juveniles of E. vernalis were more tolerant to temperature change than adults of E. vernalis. Oxygen consumption rates of E. holmani were proportional to surface area, while those of E. vernalis were a function of volume. Both species are metabolically well-adapted to the thermal conditions in their respective habitats. INTRODUCTION Information on oxygen consumption in the Anostraca, an order of crustaceans, is derived primarily from work on Artemia salina, a species adapted to salt water (Gilchrist, 1956, 1959) and provides little insight into the metabolism and respiration of freshwater anostracans. Data on oxygen consumption of freshwater groups are scarce. Daborn (1975) studied oxygen consumption in an arctic species. Limited oxygen consumption information on several other freshwater species is available in Knight et al. (1975) and Wycliffe (1979). Eubranchipus vernalis and E. holmani are common anostracans inhabiting temporary freshwater ponds in the temperate latitudes of North America. Their life cycles were described by Weaver (1943), Dexter and Kuehnle (1951), Moore (1959) and Modlin (1982). During the autumn-winter season of 1978-1979 these species were present in two temporary ponds in the same watershed in Madison Co., Alabama. Specimens of E. vernalis were collected in S & J Pond (RIW T3S Sect. 28), which is 0.4 km S of WEUP Pond (RIW T3S Sect. 21), the pond inhabited by E. holmani. This research emphasizes the influence of body size and the acute effects of temperature change on oxygen consumption by these freshwater anostracans. MATERIALS AND METHODS Specimens were collected with a D-ring dip net and transported to the laboratory in an ice chest partially filled with pond water to insure that they did not experience a drastic temperature change. In the laboratory anostracans were held in unfiltered habitat water maintained at 10 C which was near the ambient water temperature of the ponds at the time collections were made. Aquaria were illuminated with a light intensity comparable to that measured at the ponds when specimens were collected. Lights were timed to a winter photoperiod, 11 L 13D. The anostracans were assumed to be fed prior to oxygen consumption analysis because their guts were filled with Aufwuchs. The interval between specimen collection and use in oxygen consumption measurements never exceeded 48 hr. Oxygen consumption was measured at 4.0, 6.0, 8.0, 10.0, 12.0, 14.0, 16.0, 18.0 and 20.0 C on a 20-reaction-vessel Gilson Differential Respirometer. Ten to 18 reaction vessels were used as experimentals and two as controls. Each experimental vessel contained one anostracan in 5.0 ml filtered pond water and a CO2 trap. Control vessels contained 5.0 ml filtered pond water and the CO2 trap. Since the anostracans were acclimatized to their habitat temperature, no further acclimation was performed. The rationale was to maintain the organisms in as near ambient conditions as possible. Acclimation to a temperature higher or lower than ambient would mask any acute

Les peuplements de poissons de la Camargue

Fish communities in the Camargue wetlands, both temporary and permanent marshes as well as irrigation and drainage canals, were studied from 1977 to 1980. The main part of this work was carried out in wetlands isolated from direct contact with the sea by a dike, the Digue à la mer. Three major types of wetlands and their associated fish species are described in the Camargue : the freshwater (0-5 g/1 C1￣ ), the brackish (5-16 g/1 C1￣ ) , and the very brackish (16-35 g/1 C1￣ ) . A significant relationship (P< 0.01) was found between the species richness and the surface area. The slope of this regression (0.134) is lower than that found for other aquatic systems. Four associations of fish were determined and their meaning is discussed. The biomass of temporary freshwater marshes ranged between 13 to 76 kg/ha and was much lower than those found in the small freshwater canals : 112 to 2 544 kg/ha. Common carp, Cyprinus carpio L., is the dominant species in freshwater wetlands (70 to 85 % of total biomass). A space partitioning between the immature and the adult carp is described. In one waterbody studied south of the Digue à la mer, linked temporarily with the sea, the fish community composition underwent frequent and rapid changes according to the variations of environmental factors. The salinity appeared to be the most important factor affecting diversity and eveness of the fish community in this etang. A canonical analysis was used to determine which of the environmental factors had the greatest impact on the abundance of the different fish genus. Only 46.2 % of the fish species studied reproduce in the Camargue, while 35.9 % migrate to the sea for spawning. The importance of a link with the sea as well as that of a sound water management plan for the Camargue as a whole are pointed out.

The population biology of Cyprinotus carolinensis and Herpetocypris reptans (Crustacea, Ostracoda)

The population mechanics of two species of ostracod in a temporary freshwater puddle are considered in relation to their competitive interaction in a variable environment. Both species survive dry periods as eggs. When the puddle refills eggs hatch over a long period of time but in two main groups. Cyprinotus spreads hatching more evenly between the two groups, recruits more slowly, but requires less time to mature than Herpetocypris. Unhatched eggs decay at lower rates for Cyprinotus, which inhabits the shortest lived part of the puddle.Cyprinotus mortality is more affected by density than is Herpetocypris. In mixed culture, Cyprinotus mortality increases disproportionately with density while Herpetocypris mortality is simply related to joint density. This difference may be attributed to a lower resistance to food shortage by Cyprinotus which also becomes more crowded at high density. Increased density increases time required to mature. Both species lay eggs at similar rates which decline with increasing density and decreasing temperature.Natural selection has favoured competitive prowess and rapid recruitment in Herpetocypris, which is suited to a permanent environment. In Cyprinotus, which is suited to a temporary, variable environment, selection has favoured the production of durable eggs and conservative recruitment.

Comparative observations on the ecology of four species of ostracods living in a temporary freshwater puddle

The population biologies of Cyprinotus carolinensis, Herpetocypris reptans, Cypricercus reticulatus, and Candona decora in a spring-fed, temporary, winter puddle in Vancouver, Canada, were studied during 1967–1969. All species emerged at the same time in the fall, when the puddle filled, and competed to reach maturity. The order of maturation was Candona, Cyprinotus, Cypricercus, and Herpetocypris. Abundance was positively related to adult size of each species. Survivorship and fecundity patterns are given for Herpetocypris and Cyprinotus. Survivorship is closest to the type-I kind.All species have similar feeding appendages and ate grass detritus and its microinhabitants. They differed in their spatial distribution, each species being most abundant along a section of the rut. They also differed in their mobility and foraging patterns. The presence of grass was effective in restricting dispersal. Distribution and abundance of these species may be accounted for either in terms of competitive interactions or in terms of adaptation to physical differences in the environment.

Ecological Aspects of the Freshwater Decapod Crustaceans of the Perlas Archipelago, Panama

Fourteen species of decapod crustaceans occur in temporary and permanent freshwater streams in the Perlas Archipelago, Panama. Eight species of shrimps in the Atyidae and Palaemonidae and six species of crabs in the Grapsidae, Ocypodidae, and Pseudothelphusidae are represented. Island elevation, rather than area, is the best predictor of species numbers, probably because it is a better indicator of the potential for stream formation and persistence. Grapsid crabs have the widest distribution, occurring on the majority of the 11 islands sampled. Small islands are more likely to contain small rather than large species of shrimps. It is suggested that the decapods, except Potamocarcinus sp., disperse by marine planktonic larvae. Insular shrimps are significantly smaller and reproduce at a smaller size than mainland conspecifics. The adaptive significance of small body size may be related to improved chances for survival during the dry season. Reproduction occurs during the wet season, and fecundity is significantly and exponentially related to body size in shrimps. Unidentifiable detritus accounted for 48 to 88 percent of the stomach contents among the seven species of decapods examined. THE PERLAS ARCHIPELAGO Consists of approximately 50 islands in the Gulf of Panama, in the eastern Pacific Ocean. The largest 30 islands range in size from 0.35 to 261.57 km2 and in elevation up to 223 m. The smaller islets are little more than outcrops of rocks, less than two meters above mean sea level. The archipelago, a product of transgressions of the sea, has been extant since its Holocene formation about 14,000 years ago (Milliman and Emery 1968). The channel between the present mainland and the islands is about 37 m deep, and because of changes in sea level, the group was probably connected to the mainland less than 10,000 years ago. Freshwater streams are present, at least seasonally, on all but the smallest islands. The streams form during the wet season (late April through early December) and persist, to varying degrees, through the dry season (mid-December to late April). Perennial streams are present throughout the year on three of the islands (Pedro Gonzales, San Jose, and Rey), and those sampled on the remaining islands are completely dry, or by the beginning of March consist of a few isolated pools. The macrofauna of these streams is variable, but on the largest islands fishes, mollusks, and crustaceans are present. The freshwater macrofauna of the smaller islands is composed only of decapod crustaceans and a large adult coleopteran. This report deals with aspects of the ecology of the freshwater decapod fauna of both temporary and permanent streams in the Perlas Archipelago, and includes some comparisons with mainland fauna. METHODS AND MATERIALS Eleven islands, differing in area, elevation, and location within the archipelago, were sampled from 1971-1973 (table 1, fig. 1). Sampling was carried out with hand and seine nets and by hand. Rey, Sefiora, and Pedro Gonzales were sampled during both wet and dry seasons. Viveros, Mina, Cafias, and San Jose were sampled only during the wet season; Saboga, Pacheca, Contadora, and Pajaros were sampled only during the dry season. Comparisons were made with specimens collected from perennial mainland Panama streams, which were sampled monthly over a one-year period, 1972-1973. All samples were sorted and the specimens identified and measured to determine size at sexual maturity. Male shrimps were considered sexually mature with the appearance of the appendix masculina on the second pleopod, and female shrimps were considered mature if they were larger than the smallest mature male; male crabs were considered mature with the development of gonopods; and females were considered mature if the abdomen covered the sternum. The to,tal length of shrimps (tl) is from the tip of the telson to the apex of the rostrum; the carapace length (cl) was measured from the posterior margin BIOTROPICA 9(4): 239-252 1977 239 This content downloaded from 40.77.167.76 on Mon, 06 Feb 2017 18:11:09 UTC All use subject to http://about.jstor.org/terms

Studies on the ecology of some temporary freshwater pools in Victoria with special reference to microcrustaceans

Fifty-three temporary freshwater pools (mean depth 23 cm) located mainly in eastern Victoria were studied from February to September 1973. Chemical parameters determined were pH (range 5.7-8.2, mean 6.9), conductivity (K18, range 55-5500, mean 340 �S/cm), dissolved oxygen (range 23-170, mean 72% saturation) and turbidity (range 2-310, mean 50 Formazin turbidity units). A total of 60 microcrustacean species was recorded. The Australasian endemic cladoceran, Saycia cooki (King), was of common occurrence from June through to August. The fact that it tends to reach peak numbers early in the life of a pool is probably related to the production of large numbers of ephippial eggs. In contrast, cladocera which produce only one or two ephippial eggs, such as Chydorus, Moina and Simocephalus, tend to appear later in succession. Simocephalus expinosus (benthic) and Daphnia carinata, s.l. (planktonic) had mutually exclusive distributions and are apparently unable to coexist in shallow waters. Endemic cyclopoid copepods encountered included three new species of Microcyclops, M. arnaudi (Sars), Acanthocyclops australis Sars, and Acanthocyclops, sp. nov. Like Saycia, Microcyclops varicans and Acanthocyclops bisetosus exhibited maximal numbers early in succession. Several new combinations of coexisting calanoid copepod species belonging to the genera Boeckella and Hemiboeckella are reported. Computer analysis showed that the following four groups of species had a high probability of co-occurrence: (1) Cypretta sp., Attheyella australica, Ilyodromus sp., Saycia cooki; (2) Cyprinotus leanus, Acanthocyclops bisetosus, Moina tenuicornis; (3) Boeckella major, B. pseudochelae, Cypris sp., Daphnia carinata, s.l. ; (4) Simocephalus exspinosus, Microcyclops varicans.

EVOLUTION IN THE NOTOSTRACA

The Notostraca are phyllopod Crustacea in which the carapace is shield-shaped and covers the anterior part of the body; together with other phyllopods, they are considered to be relatively unevolved Crustacea-there is a high, but irregular, number of appendages (forty to sixty pairs are usual) and the segmentation of the body is anameristic. It is characteristic of phyllopods that they occur in temporary rain pools, generally in arid or steppe country where such pools are common, and are unable to maintain themselves in the face of competition from higher Crustacea or Insecta (Ard6, 1947). The survival of such primitive and vulnerable animals poses an interesting problem-the key to which may lie in their main adaptation to a temporary habitat, the drought-resistant egg. The possession of such an egg, from which hatching normally occurs only after desiccation, is an obvious prerequisite for the exploitation of a temporary freshwater habitat by a group of animals which do not have the capacities of aerial migration which the Insects possess. These drought-resistant eggs of phyllopods are the only possible means of dispersal for the group, for the pools in which the animals occur are isolated from one another, and are only rarely part of a stream system along which dispersal of adults would be possible. The eggs are small, light in weight because of their dry alveolar shells, and are sticky when laid in at least one genus (Triops, Notostraca); further, the eggs of some Anostraca are known to retain viability after passing through the guts of Amphibia (Mathias, 1937). These facts suggest several possible means of dispersal-in or upon larger animals, attached to dry pieces of wind-blown vegetation, or airborne singly in wind currents (a desert dust-devil will whirl particles much denser than the eggs of phyllopods high into the air). That 'these passive means of dispersal are effective is quite clearly shown by the ubiquitous occurrence of phyllopods in suitable pools wherever these occur. Notostraca occur on such isolated oceanic islands as the Hawaiian group, and in the few suitable pools that the rainy English climate permits. The phyllopods show another characteristic of passively distributed invertebrates-that of very widely spread, sometimes almost cosmopolitan species; in a recent study of the Notostraca for a systematic revision I found that Triops longicaudatus, which Linder (1952) showed was the only species of the genus in the Americas, extends from the West Indies through Central America and right across the Pacific to Japan by way of the Galapagoes, Oahu and New Caledonia. In all this area there is virtually no morphological change (Longhurst, 1955). These facts of dispersal and geographical distribution seem to me to explain the survival of the phyllopods. The initial arthropod invasion of temporary pools may well have been performed by the primitive fresh-water Crustacean fauna and has radiated into the forms of phyllopods we see today-the carnivorous Notostraca, the pelagic Anostraca, and the burrowing, detritus-feeding Conchostraca. This early fauna would have spread and occupied at least a high proportion of the suitable pools, and such a cosmopolitan occupation would have effectively prevented any geographically iso-