Reproductive strategies and early development of three freshwater gobies

Three species of gobiid fish inhabit the freshwater Lake Trichonis of western Greece. Two of these species, Economidichthys pygmaeus and E. trichonis are endemic, and the third is the widespread Knipowitschia caucasica . There are habitat separations between the three species, E. pygmaeus and E. trichonis prefer vegetated areas, the first being fully demersal at all stages of development and the second being semi-demersal. Knipowitschia caucasica prefers sandy bottoms and is distributed in shallower waters. Female E. pygmaeus and E. trichonis spawn in nests prepared by the males in the cavities of broken reeds. The males subsequently guard the eggs until they hatch, with females playing no role in parental care. Economidichthys trichonis is probably the smallest freshwater European species. Its eggs are ovoid, measuring about 0.64 × 0.58 mm, from which tiny, unpigmented and incompletely developed pelagic larvae hatch out after an incubation period lasting less than 1 day at a water temperature of 19.5° C. The eggs of E. pygmaeus are cylindrical and larger, measuring about 2.38 × 0.89 mm, from which relatively large, strongly pigmented and ontogenetically more advanced larvae hatch out after a longer incubation period. Both species reproduce only once in their lifetime, at the age of 1 year, and die shortly after spawning, but the breeding season involves several spawnings by each individual fish. These biological, developmental and reproductive characteristics are discussed in relation to current theories on evolution of life-historics.     

The endurance of endemism: the Mediterranean freshwater gobies and their prospects for survival

Gobies (Teleostei: Gobiidae), spawning in fresh waters of the Mediterranean catchment area, are listed, and their diagnostic features and relationships summarized. The species, by zoogeographic category, include (i) Mediterranean: Padogobius martensii (Günther, 1861) and P. nigricans (Canestrini, 1867) from the northern Adriatic and west-central Italy, (ii) West Balkanian: Economidichthys pygmaeus (Holly, 1929) and E. trichonis Economidis & Miller, 1990, and (iii) Ponto-Caspian: Prorerorhinus marmoratus (Pallas, 1811) and Knipowitschia caucasica (Kawrajsky, in Berg, 1916), from the northern Aegean area but otherwise widespread in the Ponto-Caspian region, and the endemic Mediterranean K. punctatissima (Canestrini, 1864) (north-eastern Italy) and K. thessala (Vinciguerra, 1921) (Thessaly). Scenarios for differentiation following the late Miocene Messinian salinity crisis are outlined. The vulnerability of these species is discussed, and their present status reviewed. Populations no longer exist at the precise type localities of E. pygmaeus (Lefkas) and K. thessala (Hasabali spring, Pinios river system). Special features of scientific and cultural interest are noted, and the biological capability for species recovery is assessed.     

Phylogenetics and biogeography of the Balkan ‘sand gobies’ (Teleostei: Gobiidae): vulnerable species in need of taxonomic revision

Within the Atlantic–Mediterranean region, the ‘sand gobies’ are abundant and widespread, and play an important role in marine, brackish, and freshwater ecosystems. They include the smallest European freshwater fish, Economidichthys trichonis, which is threatened by habitat loss and pollution, as are several other sand gobies. Key to good conservation management is an accurate account of the number of evolutionary significant units. Nevertheless, many taxonomic and evolutionary questions remain unresolved within the clade, and molecular studies are lacking, especially in the Balkans. Using partial 12S and 16S mitochondrial ribosomal DNA sequences of 96 specimens of at least eight nominal species (both freshwater and marine populations), we assess species relationships and compare molecular and morphological data. The results obtained do not support the monophyly of Economidichthys, suggesting the perianal organ to be a shared adaptation to hole‐brooding rather than a synapomorphy, and urge for a taxonomic revision of Knipowitschia. The recently described Knipowitschia montenegrina seems to belong to a separate South‐East Adriatic lineage. Knipowitschia milleri, an alleged endemic of the Acheron River, and Knipowitschia cf. panizzae, are shown to be very closely related to other western Greek Knipowitschia populations, and appear conspecific. A distinct Macedonian–Thessalian lineage is formed by Knipowitschia thessala, whereas Knipowitschia caucasica appears as an eastern lineage, with populations in Thrace and the Aegean. The present study combines the phylogeny of a goby radiation with insights on the historical biogeography of the eastern Mediterranean, and identifies evolutionary units meriting conservation attention. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 73–91.     

A unique teleost dermal organ in a new European genus of fishes (Teleostei: Gobioidei)

The freshwater fish fauna of Greece is a diverse assemblage of mediterranean, Ponto-Caspian, and endemic western Greek elements. In the last category, a gobiid from Epirus has been found to possess a dermal perianal organ unique among teleosts, as well as systematic features warranting recognition of a new genus, Economidichthys gen. nov. ( type-species Gobius pygmaeus Holly, 1929). The perianal organ is a sharply-demarcated, pitted area on the rear abdomen. Light-and electron-microscopy has revealed numerous specialized microvillous cells lining the pits and evidently secretory in function. Presence of the organ in both sexes, its ventral position and the secretory activity originally suggested an attachment role rather than involvement in reproduction, but obvious correlation with habitat is lacking and alternative functions are discussed.     

Length-weight relationships of 6 fish species caught in a Mediterranean lake (Trichonis-NW Greece)

In the present study the length–weight relationships (LWRs) of 6 fish species which are endemic to Western Greece, caught in the natural Lake Trichonis by experimental gillnets and electrofishing were estimated. Benthic (mesh size 5–55 mm; height 1.5 m; length 30 m) and pelagic (mesh size 6.25–55 mm; height 6 m; length 27.5 m) Nordic type multimesh gillnets were used seasonally, between February 2019 and November 2019, at different depth zones (0-57m). Electrofishing (80 Hz) conducted in the littoral zone of the lake during four samplings (2018, 2019). All the estimated LWRs were highly significant (p < .05) with high correlation coefficient (r² ≥ 0.962). The estimated b values ranged from 3.058 to 3.344. For five of the studied species (Trichonis spined loach (Cobitis trichonica Stephanidis 1974), Trichonis blenny (Salaria economidisi Kottelat 2004), Trichonis rudd (Scardinius acarnanicus Economidis 1991), Acheloos roach (Leucos panosi (Bogutskaya & Iliadou 2006)) , Hellenic minnowroach (Tropidophoxinellus hellenicus (Stephanidis 1971)) new maximum total body lengths (TL) were recorded, while for two species (T. hellenicus and L. panosi) LWRs are presented for the first time.     

Phylogeography and systematics of zebra mussels and related species

The genus Dreissena includes two widespread and aggressive aquatic invaders, the zebra mussel, Dreissena polymorpha, and the quagga mussel, Dreissena bugensis. This genus evolved in the Ponto-Caspian Sea basin, characterized by dynamic instability over multiple timescales and a unique evolutionary environment that may predispose to invasiveness. The objectives of this study were to gain insights into the demographic history of Dreissena species in their endemic range, to reconstruct intraspecific phylogeographic relationships among populations, and to clarify systematics of the genus, using DNA sequences from the mitochondrial cytochrome oxidase I (COI) gene. We found four deeply diverged clades within this genus, with a basal split that approximately coincided with the Cretaceous-Tertiary boundary. Divergence events within the four base clades were much more recent, corresponding to geographically disjunct sets of populations, which might represent species complexes. Across all taxa, populations of Dreissena shared a common pattern of genetic signatures indicating historical population bottlenecks and expansions. Haplotype diversity was relatively low in Ponto-Caspian drainages relative to more stable tectonic lakes in Greece, Macedonia, and Turkey. The phylogeographic and demographic patterns in the endemic range of Dreissena might have resulted from vicariance events, habitat instability, and the high fecundity and passive dispersal of these organisms.     

Genetic divergence in Greek populations of the genus Leuciscus and its evolutionary and biogeographical implications

In 23 populations of Greek Leuciscus ( Squalius ), the percentage of polymorphic allozyme loci ranged between 0·034 and 0·379 (P=0·19) and expected heterozygosity was 0·011–0·166 (H_e=0·067). Current taxonomy is confusing and does not correspond to genetic data that support the presence in Greece of at least seven different species: L. cephalus , L. peloponnensis , L. prespensis , L. moreoticus , L. borysthenicus , L. keadicus and Leuciscus sp. from Euboea Island. The maximum Nei modified genetic distance was found among L. keadicus and the rest of subgenus Squalius populations D * Nei=0·446–0·705). Accepting the molecular clock hypothesis, speciation for the genus Leuciscus in Greece must have occurred during the Cenozoic period (between the Middle Miocene and the Later Pliocene). The two main biogeographical events causing speciation on mainland Greece were the Uplift of the Pindic cordillera and the isolation of the southern part of Peloponnesus. The faunistic composition of the lakes studied, in which new taxa are reconsidered, suggests the same faunistic origin in the Early Pliocene for Lakes Prespa and Stymphalia and a younger one in the Late Pliocene for Lake Trichonis. Euboea Island was not a zoogeographical unit during the Cenozoic. The isolation of all the freshwater fish fauna of Euboea has occurred since the Pliocene. The biogeographical model proposed here differs from classical hypotheses in considering of lesser importance the dispersion of L. cephalus on the Greek mainland during the Neogene and Quaternary.     

Freshwater larval fish from Lake Trichonis (Greece)

The larvae of 15 freshwater fish species from Lake Trichonis (western Greece) are described from field samples and laboratory-raised fish. Larval morphologies are compared to identify distinguishing characters. The potential utility of these data sets for assessing phylogenetic relationships is discussed.     

Life history traits of Scardinius acarnanicus (Economidis, 1991) (Pisces: Cyprinidae) in two Greek lakes (Lysimachia and Trichonis)

Age, growth, reproduction and mortality of Scardinius acarnanicus, an endemic cyprinid fish from central and western Greece, were investigated in two contrasting environments, the eutrophic Lake Lysimachia and the oligotrophic to mesotrophic Lake Trichonis. Maximum ages observed were 7+ for males and 10+ for females in Lake Lysimachia and 8+ for males and females in Lake Trichonis. Scardinius acarnanicus grew allometrically (slope of fork length–somatic weight regressions >3) and relatively rapidly until age 2 or 3 years, then slowed at a time coincident with maturation. Total instantaneous mortality rates of fish from Lake Trichonis were higher than in Lake Lysimachia. Scardinius acarnanicus is a multiple spawner; monthly values of the gonadosomatic index (GSI) indicated that spawning occurred mainly in April. Mean egg diameter in Lake Lysimachia was 1.54 ± 0.2 and 1.28 ± 0.16 mm in Lake Thrichonis. In Lake Lysimachia, the population sex ratio departed markedly from 1 : 1; females were more abundant at ages >3 and the overall male : female ratio was 1 : 1.47. In Lake Trichonis, females were more abundant at ages >6; the overall male : female ratio was 1 : 1.16, not significantly different from a 1 : 1 ratio.     

Shrimps of an ancient Balkan lake: Bionomy and conservation

In order to have a comprehensive evaluation and classification of the natural biota of Lake Pamvotis, the present study aims at investigating shrimps’ bionomic traits. Information on shrimps’ habitat preferences, abundances, and syntopic species in relation to the physicochemical profile of the lake’s water are investigated for the first time. The study was carried out on a bi-monthly base, at six littoral sites of the lake. Samples’ study from different habitats and seasons revealed that the freshwater shrimp Atyaephyra thyamisensis was the most abundant species, accounting for 44.76% of the total taxa catch, while the grass shrimp Palaemonetes antennarius was less abundant (7.54%). Syntopic fish species in the littoral zone of Lake Pamvotis such as Economidichthys pygmaeus, Gambusia holbrooki, Knipowitschia caucasica and Rutillus panosi showed interannual differences with abundances of 24.12%, 19.13%, 4.26% and 0.20%, respectively. Correspondence analysis revealed clear patterns between species and stations. A. thyamisensis was predominant in shallow, well oxygenated water bodies rich with aquatic vegetation, but it was absent from deeper habitats. P. antennarius was found mainly in lentic water bodies, rocky substratum and deeper habitats. Taking into account the high ecological importance of the freshwater shrimps in ecosystems’ energy flow, ecological and biological data of lake’s shrimps are discussed and presented thoroughly. Threats and conservation measures for both shrimp species are debated also in detail.     

Global diversity of amphipods (Amphipoda; Crustacea) in freshwater

Amphipods are brooding peracaridan crustaceans whose young undergo direct development, with no independent larval dispersal stage. Most species are epibenthic, benthic, or subterranean. There are some 1,870 amphipod species and subspecies recognized from fresh or inland waters worldwide at the end of 2005. This accounts for 20% of the total known amphipod diversity. The actual diversity may still be several-fold. Amphipods are most abundant in cool and temperate environments; they are particularly diversified in subterranean environments and in running waters (fragmented habitats), and in temperate ancient lakes, but are notably rare in the tropics. Of the described freshwater taxa 70% are Palearctic, 13% Nearctic, 7% Neotropical, 6% Australasian and 3% Afrotropical. Approximately 45% of the taxa are subterranean; subterranean diversity is highest in the karst landscapes of Central and Southern Europe (e.g., Niphargidae), North America (Crangonyctidae), and Australia (Paramelitidae). The majority of Palearctic epigean amphipods are in the superfamily Gammaroidea, whereas talitroid amphipods (Hyalella) account for all Neotropic and much of the Nearctic epigean fauna. Major concentrations of endemic species diversity occur in Southern Europe, Lake Baikal, the Ponto-Caspian basin, Southern Australia (including Tasmania), and the south-eastern USA. Endemic family diversity is similarly centered in the Western Palearctic and Lake Baikal. Freshwater amphipods are greatly polyphyletic, continental invasions have taken place repeatedly in different time frames and regions of the world. In the recent decades, human mediated invasions of Ponto-Caspian amphipods have had great impacts on European fluvial ecosystems. Guest editors: E. V. Balian, C. Lévêque, H. Segers and K. Martens Freshwater Animal Diversity Assessment     

Differentiation patterns in the Scutellaria albida group (Lamiaceae) in the Aegean area

An experimental investigation of the mainly white-flowered Scutellaria albida group in the Aegean area was carried out. Eight populations representing maximum morphological variation as well as geographic separation were chosen for crosses between populations. Strong sterility barriers were observed in the Cretean endemic species, S. sieberi Benth., which also deviated morphologically and is probably an ancient relic. Strong crossing barriers were also found in plants from Euboea, and, in spite of little morphological differentiation from S. albida L. s. str., they are treated as a separate species, S. goulimyi Rech. fil. Crossing barriers of intermediate strength were present in morphologically distinct material from N Sporades, which is also treated as a separate species, S. sporadum Bothmer sp. nov. All other populations showed high compatibility in crosses among themselves, viz. populations from Bulgaria, Thrace, Andros, Naxos, and Rodhos. These were treated as the same species, S. albida , having large local as well as clinal variation. Three subspecies are retained: ssp. albida in the north; ssp. perhispida (Bornm.) Bothmer in E Macedonia, Thrace and on the islands; and the mainly purple-flowered, ssp. vacillans (Rech. fil.) Bothmer, endemic to the peninsula of Athos. Evolutionary pathways and phytogeographical patterns are discussed.
S. sporadum is mainly inbreeding and, in S. sieberi , indications of a self-incompatibility system were found. The other taxa have a more versatile system.     

Tanganyikacypridopsis gen.n. (Crustacea, Ostracoda) from Lake Tanganyika

A new genus of freshwater ostracods, Tanganyikacypridopsis gen.n., is established to include the species Potamocypris depressa Kiss, 1959, Cypridopsis calcarata Rome, 1962 and Cypridopsis anomala Rome, 1962, all from Lake Tanganyika. The genus is related to Sarscypridopsis McKenzie, 1977 and Plesiocypridopsis (Rome, 1965), mainly because of its hemipenis anatomy, and is believed to be endemic to Lake Tanganyika.     

Molecular ecology of zebra mussel invasions

The invasion of the zebra mussel, Dreissena polymorpha, into North American waters has resulted in profound ecological disturbances and large monetary losses. This study examined the invasion history and patterns of genetic diversity among endemic and invading populations of zebra mussels using DNA sequences from the mitochondrial cytochrome oxidase I (COI) gene. Patterns of haplotype frequency indicate that all invasive populations of zebra mussels from North America and Europe originated from the Ponto-Caspian Sea region. The distribution of haplotypes was consistent with invasive populations arising from the Black Sea drainage, but could not exclude the possibility of an origin from the Caspian Sea drainage. Similar haplotype frequencies among North American populations of D. polymorpha suggest colonization by a single founding population. There was no evidence of invasive populations arising from tectonic lakes in Turkey, while lakes in Greece and Macedonia contained only Dreissena stankovici. Populations in Turkey might be members of a sibling species complex of D. polymorpha. Ponto-Caspian derived populations of D. polymorpha (theta = 0.0011) and Dreissena bugensis (one haplotype) exhibited low levels of genetic diversity at the COI gene, perhaps as a result of repeated population bottlenecks. In contrast, geographically isolated tectonic lake populations exhibited relatively high levels of genetic diversity (theta = 0.0032 to 0.0134). It is possible that the fluctuating environment of the Ponto-Caspian basin facilitated the colonizing habit of invasive populations of D. polymorpha and D. bugensis. Our findings were concordant with the general trend of destructive freshwater invaders in the Great Lakes arising from the Ponto-Caspian Sea basin.     

History of the genus <Emphasis Type="Italic">Didacna</Emphasis> (Bivalvia: Cardiidae)

The history of the Quaternary genus Didacna, which is endemic to the Ponto-Caspian Sea, is discussed. Quaternary stratigraphy of this region and Didacna assemblages recorded in the Neopleistocene sequence are characterized. The development of this genus against the background of the Ponto-Caspian history is reconstructed; the replacement of species and associations of Didacna, the character of speciation, and examples of homeomorphism are discussed. Seventy-seven species of this genus, which appeared over slightly more than 600 thousand years, are described; this indicates an extremely intense speciation in Pleistocene brackish-water basins, which were inhabited by only five bivalve genera belonging to two families.     

Paleoclimatic history and vicariant speciation in the "sand goby" group (Gobiidae, Teleostei)

Vicariant and climatic cycling speciation hypotheses of the 'sand gobies' belonging to the genera Pomatoschistus, Gobiusculus, Knipowitschia, and Economidichthys are tested using molecular phylogenies constructed of nuclear DNA (ITS1 locus) and mitochondrial DNA (12S and 16S fragments). These gobies are among the most abundant in the Eastern Atlantic-Mediterranean region, and play an important role in the ecosystem. Considerable ITS1 length differences, primarily due to the presence of several tandem repeats, were found between species and even within individuals. Therefore, phylogenetic analyses focused on fragments of the 12S and 16S mtDNA region that have been sequenced for 16 goby taxa. The 'sand gobies' clustered as a monophyletic group as proposed on morphological grounds. However, G. flavescens, E. pygmaeus, and K. punctatissima clustered within the Pomatoschistus species, pointing to a paraphyletic origin of these genera. Furthermore, the genetic divergence between P. minutus from the Adriatic Sea versus the Atlantic-Mediterranean region was as high as the divergence within the P. minutus complex, suggesting that P. minutus from the Adriatic Sea should be considered as a distinct species. The "star" phylogeny might suggest that these gobies evolved in a very short time period, possibly linked to the drastic alterations in the Mediterranean Sea during and immediately after the Messinian salinity crisis at the end of the Miocene. The freshwater life-style appeared monophyletic; equating its origin with the salinity crisis resulted in a molecular clock estimate of 1.4% divergence per million years. The last common ancestor probably occupied sandy bottoms and a coastal niche while several species subsequently adapted to new habitats (pelagic, freshwater or stenohaline). The origin of the shallowest clades dated back to the glacial cycling during the Pleistocene epoch.     

Echiuropus bekmanae n.sp. (Crustacea, Amphipoda, Carinogammaridae) from Lake Baikal, retrieved by a new deep-water sampling device

Lake Baikal is well known for its exceptional diversity of gammarid amphipods, with 95% of endemics from its 270 described species representing about 20% of the world freshwater fauna. Echiuropus (Asprogammarus) bekmanae n.sp. was collected by an `autonomous trap system', a sampling device thoroughly described here. Although not necrophagous itself, this new species was found in two baited trap samples (at 750 and more than 1600 m) from 1995 and 1996. This rather small (13 mm) deep water species is the eighth species of the subgenus Asprogammarus, of the Baikal endemic genus Echiuropus. Diagnoses of the subgenus and the closer species are given.     

Length–weight relationships of eight freshwater (Cypriniformes) fish species from Turkey

The length–weight relationships for eight freshwater fish species collected from Bey?ehir Lake, E?irdir Lake, Aksu River, Alara River, Göksu River and Menzelet Reservoir, were analysed. This paper represents the first LWR references for four of these species and also four of these species are endemic to Turkey.     

Global diversity of mysids (Crustacea-Mysida) in freshwater

In this article we present a biogeographical assessment of species diversity within the Mysida (Crustacea: Malacostraca: Peracarida) from inland waters. Inland species represent 6.7% (72 species) of mysid diversity. These species represent three of the four families within the Mysida (Lepidomysidae, Stygiomysidae, and Mysidae) and are concentrated in the Palaearctic and Neotropical regions. The inland mysid species distributional patterns can be explained by four main groups representing different freshwater invasion routes: (1) Subterranean Tethyan relicts (24 spp.); (2) Autochthonous Ponto-Caspian endemics (20 spp.); (3) Mysis spp. ‘Glacial Relicts’ (8 spp.); and (4) Euryhaline estuarine species (20 spp.). The center of inland mysid species diversity is the Ponto-Caspian region, containing 24 species, a large portion of which are the results of a radiation in the genus Paramysis. Electronic Supplementary Material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Guest editors: E. V. Balian, C. Lévêque, H. Segers and K. Martens Freshwater Animal Diversity Assessment     

Phylogeny of Paramysis (Crustacea: Mysida) and the origin of Ponto-Caspian endemic diversity: resolving power from nuclear protein-coding genes

The Ponto-Caspian (Black and Caspian seas) brackish-water fauna represents a special case of the endemic diversification in world's ancient lakes; it also involves a hotspot of continental diversity in the predominantly marine mysid crustaceans. We explored the origins and history of the mysid diversification in a phylogenetic analysis of some 20 endemic Ponto-Caspian species mainly of the genus Paramysis and their marine congeners, using sequences of two nuclear protein-coding genes, two nuclear rRNA genes, the mitochondrial COI gene and morphological data. A nearly completely resolved phylogeny was recovered, with no indication of rapid diversification bursts. Deep divergences were found among the main endemic clades, attesting to a long independent faunal history in the continental Paratethys waters. The current marine Paramysis species make a monophyletic cluster secondarily derived from the continental Paratethyan (Ponto-Caspian) Paramysis ancestors. The good phylogenetic resolution was mainly due to the two nuclear protein-coding genes, opsin and EPRS, here for the first time applied to peracarid systematics. In contrast, 'conventional' mtDNA and nuclear rRNA genes provided poor topological resolution and weak congruence of divergence rates. The two nuclear protein-coding genes had more congruent rates of evolution, and were about 10-15 times slower than the mitochondrial COI gene.