Harpacticoid Species Research Articles

Effects of spatial versus seasonal sources of environmental variability in springs: a case study of microcrustaceans (Ostracoda, Harpacticoida) in a calcareous helocrene

The cold temperate helocrenes are usually attributed to high biodiversity because of environmental heterogeneity. Their temporal stability of environmental conditions reduces seasonal changes in assemblage composition. However, the within-site patterns and processes have been only rarely studied in springs, thus our knowledge remains limited. In this study, we investigated a microcrustacean assemblage of a helocrenic calcareous spring at a high spatial resolution. We tested differences among visually distinct mesohabitats, and related the assemblage composition variation to environmental variables and seasonal changes by a repeated sampling in spring, summer and autumn. At this single site, we recorded 26 species of ostracods and harpacticoids, accounting for almost 50% of the whole known regional species pool. Species richness and composition varied significantly between the mesohabitats, the latter mainly due to differences in environmental variables (mainly water depth and temperature). The occurrence of cold-adapted species was restricted to the spring source, but species inhabiting other mesohabitats had clearly broader ecological niches. Despite significant temporal changes in water temperature, microcrustaceans showed almost negligible seasonal changes in species composition, suggesting that their microdistribution remains stable throughout the year. Our findings have important implications for sampling design of large-scale ecological studies and spring conservation.

REDESCRIPTION OF <i>MORARIA</i> (<i>BAIKALOMORARIA</i>) <i>WERESTSCHAGINI</i> BORUTZKY 1949 (COPEPODA, HARPACTICOIDA, CANTHOCAMPTIDAE) FROM LAKE BAIKAL

This report is the second of a series devoted to redescriptions of members of Baikalomoraria based on modern research methods. An illustrated redescription of the female and male of Moraria (Baikalomoraria) werestschagini Borutzky 1949, a rare endemic harpacticoid species from the littoral zone of Lake Baikal, is presented. Since the type material of the species was lost, it became necessary to select a neotype. For the first time, the morphology of this species was studied in detail using scanning electron microscopy, and a description of the mouthparts and antennules was given. The description of the swimming legs was significantly supplemented and the structure of the genital field was shown, including data on the morphological variability of limbs. In addition, we briefly describe the fifth copepodite stages of the male and female. The fifth copepodite stage of the female was found to bear long apical setae on the caudal rami, vs adult females characterized by short setae more similar to spines.

REDESCRIPTION OF <i>MORARIA</i> (<i>BAIKALOMORARIA</i>) <i>LONGICAUDA</i> BORUTZKY 1952 (COPEPODA, HARPACTICOIDA, CANTHOCAMPTIDAE) FROM LAKE BAIKAL

An illustrated redescription of the female and male of Moraria (Baikalomoraria) longicauda Borutzky 1952 is presented, a harpacticoid species endemic to the littoral zone of Lake Baikal, Siberia. A neotype is designated, because the type material is lost. The morphology of this species was studied in detail using scanning electron microscopy for the first time. An illustrated description of the mouthparts and antennules is given; that of the swimming legs being expanded. The structure of the genital field is shown and data on morphological variability are presented.

A new species of Eupelte (Copepoda: Harpacticoida: Peltidiidae) from Anchialine caves in Bermuda

A new anchialine species of Eupelte (Copepoda: Harpacticoida: Peltidiidae) is described from tidal pools and submerged passages in Bermuda caves. It is the sixth anchialine harpacticoid species known from Bermuda and the first anchialine member worldwide of the family Peltidiidae. The genus Eupelte currently contains 16 valid species, of which five have been found in the Atlantic Ocean, four in the Pacific Ocean, three in the Indian Ocean, two in the Mediterranean Sea, one in arctic waters and the last one in antarctic waters.

Integrative redescription of Canthocamptus (Baicalocamptus) longifurcatus (Harpacticoida: Canthocamptidae), an endemic species from Lake Baikal

A redescription of the Lake Baikal endemic species, Canthocamptus (Baicalocamptus) longifurcatus Borutzky, 1947 (Harpacticoida: Canthocamptidae), is provided. The illustrated redescription of morphology of the female and male is supplemented by a genetic barcoding based on sequences of the mitochondrial COI marker. Canthocamptus (B.) longifurcatus is morphologically very similar to another representative of the subgenus, C. (B.) verestschagini (Borutzky, 1931), but can be well distinguished from the latter by the armature of the female furca and the structure of the last pair of swimming legs in the female and male. An analysis of the obtained COI sequences and their comparison with those of other harpacticoid species confirmed that C. (B.) longifurcatus belongs to the genus Canthocamptus Westwood, 1836: the smallest genetic differences (on average, 29.5%) were observed between the studied Baikal species and C. staphylinus Jurine, 1820 from Europe (Lake Geneva, Switzerland).

New records of Harpacticoids (Crustacea, Copepoda) from a coastal system of northern Colombia

Three species of harpacticoids are herein recorded from the zooplankton of Rodadero beach, Santa Marta, Magdalena, Colombia. Samples were collected from the littoral zone, mainly at inshore areas covered by mangrove vegetation and in an adjacent oyster bank. One of them, Laophonte cornuta Philippi, 1840 is new to the Colombian harpacticoid fauna, the other two species: Distioculus minor (Scott T., 1894) and Microsetella norvegica (Boeck, 1865) are new reports to the Magdalena department. This is the first illustrated record confirming their presence in Colombia and Magdalena, northern Colombia. Comparative morphological comments and illustrations of these species are also provided to document this report.

A new species of sublittoral marine copepod, Normanella parvisetosa sp. nov. (Harpacticoida, Normanellidae), from the Southern Sea of South Korea

Abstract A new harpacticoid species, Normanella parvisetosa sp. nov., belonging to the family Normanellidae Lang, 1944, is described from subtidal habitats in the Southern Sea of South Korea. This new species is assigned to the minuta-lineage, based on the rostrum with a pointed apical tip, the five-segmented female antennule, the female P5 exopod without a distinct notch on the outer margin, and well-developed caudal setae IV and V each bearing an internal fracture plane. Normanella parvisetosa sp. nov. is morphologically close to N. incerta Lang, 1934, N. porosa Noodt, 1964, and N. obscura Lee & Huys, 1999, whereas the new species is distinguished from females of these species in the shape of the rostrum with a pointed tip, the relative length to width ratio of the caudal rami, the second endopodal segment of the second to fourth legs, the exopod of the fifth leg, and the relative length of setae on both rami of the fifth leg. Herein, we provide a detailed description and illustrations of Normanella parvisetosa sp. nov., which is the second Normanella species identified in Korean waters.

Importance of nonindigenous harpacticoids (Crustacea: Copepoda) decrease with depth in Lake Ontario

Harpacticoid copepods can be a substantial component of the meiobenthic community in lakes and serve an ecological role as detritivores. Here we present the first species-level lake-wide quantitative assessment of the harpacticoid assemblage of Lake Ontario with emphasis on the status of nonindigenous species. Additionally, we provide COI-5P sequences of harpacticoid taxa through Barcode of Life Data System (BOLD). Harpacticoids were collected at depths from 0.1 to 184 m and from a range of substrates from August to September 2018 as part of the Cooperative Science and Monitoring Initiative (CSMI) offshore benthic survey. Twenty-six meiobenthic samples were analyzed using microscopy for community composition analysis of harpacticoids. We found thirteen indigenous and three nonindigenous species of harpacticoid, with the introduced species dominating at shallow depths. The community transitioned from nonindigenous to indigenous species dominance as depth increased. Nonindigenous species accounted for 79% of the community (by abundance) at depths <20 m, 55% from 20 to 40 m, and only 24% at depths >40 m. The nonindigenous species encountered included the first detections of Schizopera borutzkyi (Monchenko, 1967) and Heteropsyllus nunni (Coull, 1975) from Lake Ontario. S. borutzkyi was the most abundant harpacticoid species in the lake, approaching a maximum density of 50,000/m2 and a lake-wide average density of 7,900/m2. Numerically important indigenous species included Bryocamptus nivalis (Willey, 1925), Canthocamptus robertcokeri (Wilson, 1958), Canthocamptus staphylinoides (Pearse, 1905), and Moraria cristata (Chappuis, 1929). The prevalence of nonindigenous harpacticoids in the meiobenthos of Lake Ontario suggests further investigations of Great Lakes meiofauna communities are warranted.

Comparative characteristics of harpacticoids species diversity in contact zones of the northwestern part of the Black sea

In the article there are research results of comparative analysis of the species structure of crustaceans Harpacticoida (Copepoda) in the meiobenthos of different contact zones in the north-western part of the Black Sea. The fauna of harpacticoid copepods of contour biotopes in NWBS during the study period numbered 76 species belonging to 46 genera from 23 families. The largest number of species of harpacticoid copepods (44 species) was registered on the pelocontour. The lithocontour and psamocontour had 39 and 34 species of harpacticoids, respectively. The smallest number of species (19 species) of harpacticoid copepods was registered on the potamo contour. Cluster analysis of the harpacticoid species number in contour biotopes showed that the fauna of the potamocontour is similar to other contours by only 20.07 %. The similarity in the species composition of the peloton and lithocontour is 52.27 %, and the species diversity of the potamocontour harpacticoids is similar to them by 42.85 %. Common to all contour habitats are 6 species: Ameira parvula parvula, Dactylopusia tisboides, Ectinosoma melaniceps, Harpacticus flexus, Harpacticus littoralis, Laophonte elongata elongata. Vegetation of the OMR lithocontour had the largest number of species (35 species, which is 46 % of the total number of species), and near 24 species of snakes were noted. Almost the same number of species was observed at the stations remote from the shore and near the shore. The smallest number of species was noted on the interstitial supralittoral of the psamocontour, and their number was almost three times greater in the upper sublittoral. The Pelocontour of Yagorlytska and Tendrivska counted 34 species of harpacticoid copepods, and in the OMR – 21 species. The coastal part of the potamocontour is characterized by the greatest species diversity (Margalef index – 1.3±0.1, Shannon index – 1.7±0.3; Simpson index – 0.8±0.05).

Faunistic and ecological assessment of interstitial Harpacticoida (Crustacea, Copepoda) on a sandy beach in Balıkesir (Turkey)

Interstitial harpacticoids along the mediolittoral zones of Sarımsaklı Beach, Turkey, were sampled monthly between April 2016 and March 2017 in order to reveal the effects of pH, water temperature, salinity, electrical conductivity, dissolved oxygen, and grain size on the occurrence and composition of the harpacticoids. Examination of the samples from nine stations revealed a total of 66 species. In terms of harpacticoid species abundance, Ectinosoma soyeri Apostolov, 1975 was ranked first followed by Sarsamphiascus angustipes (Gurney, 1927) and Leptomesochra eulitoralis Noodt, 1952. The variations in harpacticoid community were estimated by using some ecological indices (Species richness, Shannon’s diversity and Pielou’s evenness). Principal component analysis (PCA) based on the abiotic factors was applied for ordination of the stations. Relationships between environmental and temporal parameters as well as harpacticoid community structure were analyzed using distance-based Linear Models (DistLM). Relationships between environmental variables and most abundant species were determined with the Redundancy analysis (RDA). The abundance of S. angustipes and Klieonychocamptus ponticus (Serban and Plesa, 1957) were positively correlated with all tested variables except water temperature. The abundance of Klieonychocamptus kliei (Monard, 1935) was positively correlated with water temperature, grain size and salinity, while it was negatively correlated with dissolved oxygen and pH. The abundance of Ameira sp. and Microsetella norvegica (Boeck, 1865) were negatively correlated with all tested variables except water temperature. The abundance of E. soyeri and Ameira parvula (Claus, 1866) were negatively correlated with all tested variables except pH. The abundance of Leptomesochra eulitoralis was positively correlated with water temperature and salinity, while it was negatively correlated with grain size, dissolved oxygen and pH.

Benthic Meiofaunal Diversity in Four Zones of Pichavaram Mangrove Forest, India

ABSTRACTThe community structure of meiofauna was assessed relative to environmental parameters in four zones (non-mangrove, Avicennia zone, mixed zone, and Rhizophora zone) of Pichavaram Mangrove Forest, which is located along the southeast coast of India. Field sampling was carried out from June 2016–May 2017. The meiofaunal data were evaluated using univariate and multivariate statistics. The highest abundance of meiofauna (434 ind/10 cm−2) was recorded in the Rhizophora zone and the lowest (270 ind/10 cm−2) in the non-mangrove zone. A total of 62 species representing four meiofaunal groups were recorded, including 38 species of foraminifera, 12 species of nematodes, seven species of ostracods, and five species of harpacticoids. Diversity (Shannon H′) mostly ranged from 3–4, and was highest (3.86±0.26) in the Avicennia zone and averaged ∼3.3 in the other three zones. The Margalef richness index was ∼6 in the Avicennia and Rhizophora zones and ∼5 in the non-mangrove and mixed zones. The BIO-ENV and CCA analyses identified sediment texture and organic matter as key variables influencing the distribution of meiofauna, while % calcium carbonate, salinity, and sediment pH were also important. Monitoring studies of meiofaunal taxa may help elucidate their roles in coastal blue-carbon cycling and will also contribute to understanding how mangrove-associated habitats influence meiofaunal distributions.

On some deep-sea Stenheliinae from the Gulf of California and the west coast of the Baja California Peninsula (Mexico): Pseudostenhelia bathyalis sp. nov., and Beatricella calidafornax sp. nov. (Copepoda: Harpacticoida: Miraciidae).

At present, only a handful of harpacticoid species of the families Ameiridae Boeck, Ancorabolidae Sars, Argestidae Por, and Rhizothrichidae Por have been described from the deep sea of the Gulf of California and west coast of the Baja California Peninsula. Recent efforts resulted in the description of a new genus, Wellstenvalia Gmez Cruz-Barraza, 2021, closely related to Muohuysia zdikmen, 2009 and Wellstenhelia Karanovic Kim, 2014 and some new deep-sea species of Delavalia Brady, 1869. Other new stenheliin genera from the Gulf of California and the west coast of the Baja California Peninsula are the subjects of another contribution in this volume. The present contribution deals with the description of the first deep-sea representatives of Pseudostenhelia Wells, 1967 and Beatricella Scott, 1905, two typically shallow brackish water and marine genera. Some comments on their relationships are given.

Harpacticoid assemblages (Copepoda: Harpacticoida) in the hyporheic zone of four streams in central Slovenia

Harpacticoids are an important component of meiofaunal assemblages in hyporheic zone. The goal of this study was to investigate distribution patterns of interstitial harpacticoid assemblages from four pre-Alpine streams originating in the Dinaric Karst and flowing into the Ljubljanica River. The sampling was conducted in 2002 at 12 locations distributed at a distance of approximately 1 km along each stream including tributaries, at a depth of 30–60 cm in the wetted channel (three sites per location) and depths from 65 to 160 cm on the stream banks (one site per location) using a Bou-Rouch pump. Concurrently, the interstitial water’s physical and chemical parameters were measured at two sites within each location (streambed, streambank). A total of 24 harpacticoid species were found, 12 of which were stygobionts (i.e., species living exclusively in groundwaters). Among them, two previously unknown species for science were found. Harpacticoid assemblage composition, with the exception of those from the Iška stream, did not differ significantly between the streams, indicating interconnectivity of the interstitial milieu. Sediment structure, amounts of particulate organic matter, conductivity and redox conditions seemed to have certain impacts, indicating the importance of hydrological and geological settings for harpacticoid assemblages.

Integrative Description of Cryptic Tigriopus Species From Korea Using MALDI-TOF MS and DNA Barcoding

MALDI Time-of-Flight Mass Spectrometry (MALDI-TOF MS) provides a fast and reliable alternative method for species-level identification of pathogens and various metazoans. Compared to the commonly used mitochondrial cytochrome c oxidase subunit I (mtCOI) barcoding, advantages of MALDI-TOF MS are rapid species identifications and low costs. In this study, we used MALDI-TOF MS to determine whether spectra patterns of different species can be used for species identification. We obtained a total of 138 spectra from individual specimens of Tigriopus, which were subsequently used for various cluster analyses. Our findings revealed these spectra form three clear clusters with high AU value support. This study validates the viability of MALDI-TOF MS as a methodology for higher-resolution species identification, allowing detection of cryptic species of harpacticoida. In addition, we propose a new species, Tigriopus koreanus sp. nov. by utilizing integrative methods such as morphological comparison, mtCOI barcoding, and MALDI-TOF MS.

Spatial distribution of stygobitic crustacean harpacticoids at the boundaries of groundwater habitat types in Europe

The distribution patterns of stygobitic crustacean harpacticoids at the boundaries of three different groundwater habitat types in Europe were analysed through a GIS proximity analysis and fitted to exponential models. The results showed that the highest frequency of occurrences was recorded in aquifers in consolidated rocks, followed by the aquifers in unconsolidated sediments and, finally, by the practically non-aquiferous rocks. The majority of the stygobitic harpacticoid species were not able to disperse across the boundaries between two adjacent habitats, with 66% of the species occurring in a single habitat type. The species were not evenly distributed, and 35–69% of them occurred from 2 to 6 km to the boundaries, depending on the adjacent habitat types. The distribution patterns were shaped by features extrinsic to the species, such as the hydrogeological properties of the aquifers, and by species’ intrinsic characteristics such as the preference for a given habitat type and dispersal abilities. Most boundaries between adjacent habitat types resulted to be “breaches”, that is transmissive borders for stygobitic harpacticoids, while others were “impermeable walls”, that is absorptive borders. Our results suggest that conservation measures of groundwater harpacticoids should consider how species are distributed within the different groundwater habitat types and at their boundaries to ensure the preservation of species metapopulations within habitat patches and beyond them.

Integrative description of Diosaccus koreanus sp. nov. (Hexanauplia, Harpacticoida, Miraciidae) and integrative information on further Korean species.

A new species of Diosaccus Boeck, 1873 (Arthropoda, Hexanauplia, Harpacticoida) was recently discovered in Korean waters. The species was previously recognized as D. ezoensis Itô, 1974 in Korea but, here, is described as a new species, D. koreanussp. nov., based on the following features: 1) second inner seta on exopod of fifth thoracopod apparently longest in female, 2) outer margin of distal endopodal segment of second thoracopod ornamented with long setules in male, 3) caudal seta VII located halfway from base of rami (vs. on anterior extremity in D. ezoensis), and 4) sixth thoracopod with three setae in female (vs. 2 setae in D. ezoensis). In addition, there is also a mitochondrial COI sequence difference of more than 19.93% with D. ezoensis registered in NCBI. A key to Diosaccus species of the world is also provided, and new morphological features and DNA sequences are presented for two other harpacticoid species, Parathalestris verrucosa Itô, 1970 and Peltidium quinquesetosum Song & Yun, 1999. In order to clearly identify harpacticoids at the species level, both morphological and DNA sequence characteristics should be considered.

Influences of microtidal regime and eutrophication on estuarine zooplankton

This study describes the ecology of mesozooplankton in the shallows of the large central basin area of the Swan-Canning Estuary on the microtidal lower west coast of Australia during the mid-1980s when, as in most other south-western Australian estuaries, it was mesotrophic. As the vast majority of species reproduce within the estuary and there is a lack of a net upstream flow of bottom water during each tidal cycle to facilitate selective tidal transport, the populations of those species are considered autochthonous. Species restricted to the estuary accounted for 63% of the total number of species and 83% of abundance. Contributions by tychoplankton to total number of species (68%) and individuals (59%) exceeded the corresponding values of 18 and 39% for holoplankton and 14 and 2% for meroplankton. Low meroplankton values result from a paucity of benthic macroinvertebrate species with planktotrophic development. Comparisons with data for the shallow basin areas of the nearby highly eutrophic Peel-Harvey Estuary were used to indicate how mesozooplankton in the microtidal estuaries respond to excessive nutrient enrichment. The mean number of species in the Swan-Canning was essentially the same as in the Peel-Harvey, whereas concentrations were only half, reflecting the lower productivity of the former estuary. However, concentrations of the four most abundant species in the Swan-Canning, the amphipod Grandidierella propendatata, the calanoids Gladioferens imparipes and Acartia cf. clausi and a harpacticoid species, exceeded those of these species in the Peel-Harvey by between 1.6 and 11.7 times. Greater concentrations in the Swan-Canning were attributable to this mesotrophic system not undergoing the reduction in oxygen concentrations and/or environmental degradation, to which these species are susceptible. In contrast, concentrations of the amphipods Corophium minor and Tethygenia elanora and large nematodes, which are tolerant of degraded environmental conditions, were greater in the Peel-Harvey. Holoplankton made a far greater contribution in the Swan-Canning than Peel-Harvey, due to substantial numbers of copepods that benefit from good environmental conditions. Mesozooplankton composition in both estuaries underwent cyclical changes during the year due to time-staggered differences in seasonal concentrations of various species. Cyclical changes and variations in composition were more closely related to measured environmental variables in the Swan-Canning than Peel-Harvey estuaries. The concentrations of many species were greater at night than during the day presumably reflecting a nycthemeral response and/or low nocturnal oxygen concentrations at the bottom of the water column.

Abundance and reproduction variables of two species of harpacticoid copepods along an increasing salinity gradient

Spatial and temporal complexities of reproductive behaviour and sex ratios of two harpacticoid species Canuella perplexa Scott T. & Scott A., 1893 and Bryocamptus sp. were evaluated monthly from September 2007 to August 2008. Collections were made from four ponds at different salinities in the solar saltern of Sfax, Tunisia, considering other environmental features as well. The salinities ranged from 38.0 to 86.1 psu. With rising salinity, the abundance of C. perplexa adults declined from 4550 ± 4160 ind m−3 (pond A1, salinity = 41.5 ± 2.3 psu) to 880 ± 780 ind m−3 (pond C31, salinity = 71.0 ± 4.3 psu). The abundance of Bryocamptus sp. adults increased from 3560 ± 2810 ind m−3 (A1) to 10,080 ± 6890 ind m−3 (C31). The abundance of total adults of C. perplexa was negatively correlated with both salinity (r = − 0.441, n = 18, p < 0.05) and abundance of dinoflagellates (r = − 0.291, n = 18, p < 0.05) and positively correlated with suspended matter (r = 0.389, n = 18, p < 0.05), temperature (r = 0.354, n = 18, p < 0.05), and abundance of diatoms (r = 0.410, n = 18, p < 0.05). The abundance of adults of Bryocamptus sp. displayed only a positive correlation with salinity (r = 0.452, n = 18, p < 0.05). In both species, the sex ratio (males/females) was driven by the variability of female abundance but never exceeded 1.0. For C. perplexa, the egg number per female ranged between 28 and 31; the ovisac length was between 0.39 ± 0.002 and 0.45 ± 0.018 mm. The egg diameter ranged from 0.062 ± 0.001 to 0.065 ± 0.002 mm, and the total length of ovigerous females ranged between 1.2 and 1.35 mm. For Bryocamptus sp., the egg number per female ranged between 19 and 22, the ovisac length between 0.28 ± 0.008 and 0.31 ± 0.003 mm, the egg diameter between 0.041 ± 0.001 and 0.044 ± 0.001 mm, and the total length of ovigerous females between 0.6 and 0.74 mm. The outcome of this study demonstrated that under extreme environmental conditions and increasing salinity the percentage of diatoms and dinoflagellates was found to be an essential factor in controlling the abundance and reproduction traits of both harpacticoids in this study. Furthermore, the sex ratios in these harpacticoid populations are complex as many factors can influence and alter the sex ratios in natural populations.

Benthic Harpacticoida of the Cara sea: species composition and bathymetric distribution

Data on benthic harpacticoid copepods from the Voronin Trench (central part of the Kara Sea) are reported for the first time. Harpacticoids accounted for 1–25% of total meiofauna, their abundance varied from 6 to 102 ind/10 cm2 and decreased with depth. Totally, 42 nominal species have been found, 15 species are new for the Kara Sea, and at least eight species are new for science. Several species are first records for the Arctic waters (Cylindronannopus bispinosus, Haloschizopera clotensis, H. bathyalis, Metauntemannia pseudomagniceps, Mesocletdemus duosetosus, M. parabodini, Proameira echinipes, Cletodes tuberculatus). Ameiridae, Argestidae, Pseudotachidiidae, Miraciidae and Ectinosomatidae are the most species-rich families. Joint analysis with data on shallow-water stations (Yenisei Gulf, southern Kara Sea) revealed three assemblages occupying different habitats. The assemblage inhabiting shallow silts (20–62 m in depth) was the poorest one, the shallow sands were more species-rich, while the deepest stations (92–698 m) was the richest one. The latter assemblage had the composition of families typical for the deep-sea areas. The known fauna of the Kara Sea includes 82 harpacticoid species, most of which have been also reported from north Atlantic and/or western Arctic waters.

Changes in Copepod Community Between Two Contrasting Samplings in a Highly Polluted Mediterranean Coastal Zone (Sfax Bay, Tunisia)

Changes of taxonomic composition, morphology (total length) and reproductive mode of copepod assemblages between the cold and warm periods were studied in the Southern coast of Sfax, in relation with environmental factors and pollution degree (heavy metal concentration). Salinity, temperature and heavy metal concentration seem to be the most important factors influencing the total length during both sampling periods. A total of 23 different copepod species were identified during the survey period. The copepod abundance was higher in cold (74%; 9.78 ± 10.04 A— 103 ind m-3) than in warm (67%; 7.11 ± 8.81 A— 103 ind m-3) periods. This result could be attributed to an increase of temperature and salinity in August, which favors the development of smaller copepod species. During the cold season, larger adult broadcaster of calanoids species (total length between 0.98 and 1.22 mm) such as Acartia (Acartia) danae (Giesbrecht) (Tl = 1.22 mm), Paracartia grani (Sars) (Tl = 1.12 mm) and Paracartia latisetosa (Krichagin) (Tl = 1.06 mm) were associated to low temperature and salinity. During the warm period, smaller egg-carrying species of harpacticoids (total length between 0.18 and 0.3 mm) such as Harpacticus littoralis (Sars), Tisbe furcata (Baird) and Tigriopus sp. (Norman) were associated with high temperature and heavy metal pollution. H. littoralis displayed a very high abundance of ovigerous females (Nfo = 12.8 A— 103 ind m-3, representing 87.2% of total number of females) with high number of eggs per sac (E = 26 ± 2 egg sac-1).