Morphological development and allometric growth patterns in hatchery-reared California halibut larvae

Morphological development, allometric growth and behaviour of hatchery-reared California halibut Paralichthys californicus were studied from hatching to metamorphosis (42 days post hatch, dph) at 187° C. Mean standard length ( L _S) of larvae and juveniles increased from 2.1 mm at hatching to 10.5 mm at metamorphosis with the increase in length being approximately linear. Stages of morphological development were described using the alphabetic staging (A–I) used for other flatfish species. Organogenesis and differentiation were more rapid and complex in yolk-sac (hatching, stage A–3 dph, stage B), preflexion (3–19 dph, stages B–C), and flexion larvae (from 20 to 23 dph, stages D–E), as larvae developed most of their sensory, feeding, respiratory and swimming systems. After notochord flexion at 24–25 dph (stage F), most morphological changes were related to the progressive transformation from a bilateral symmetrical larva to an asymmetrical benthic juvenile (42 dph, stages G–I).     

Les Corycaeidae (copepoda, cyclopoidea) des eaux libanaises: observations faunistiques et ecologiques

Based on WP2 plankton net samples collected monthly between1970 and 1982 at several inshore and offshore stations alongthe coast of Lebanon, a morphological and ecological study ofthe Corycaeidae was carried out. This family is representedby 11 species. These are as follows, in decreasing abundance:Farranula rostrata, Corycaeus brehmi, C. typicus, C. giesbrechti,C. ovalis, C. minimus, C. clausi, C. larus, C. flaccus, C. limbatusand C. furcifer. Corycaeus minimus indicus is recorded for thefirst time in the Mediterranean. The seasonal variations inabundance showed a maximum in spring (March-June), the timingof the peak being slightly different between the stations andaccording to the dominating species. Spatial distribution showedan eupelagic sub-superficial tendency for the majority of thespecies found. As far as the geographical distribution is concerned,the Corycaeidae of Lebanon belong, in general, to the Mediterraneanand temperate Atlantic planktonic fauna, with a certain subtropicalaffinity for some species, due to the effect of Indo-Pacificmigration through the Suez Canal to the Eastern MediterraneanBasin: C. minimus indicus is such a case.     

PCR-based methods for identification of species of the Anopheles minimus group: allele-specific amplification and single-strand conformation polymorphism

We report two polymerase chain reaction (PCR)-based methods for distinguishing morphologically similar species based on amplification of a variable region of the 28S gene of ribosomal DNA. The four species we investigated are mosquitoes of the Anopheles minimus group: An. aconitus, An. varuna and An. minimus species A and C. The formally named species are vectors of human malaria parasites in south-east Asia but are difficult to distinguish with certainty on the basis of morphology. Allele-specific amplification was used to differentiate An. minimus A from An. minimus C. This technique has been widely used for the diagnosis of species. Single-strand conformation polymorphisms (SSCPs) were used to separate all four species. This technique, which has seldom been used for species identification, has many advantages: it does not require sequence information beyond that needed for amplification; it is ideally suited for the detection of heterozygotes; it utilizes more of the information in the PCR product than allele-specific amplification; it distinguishes all four species considered here and could easily be extended to other species; previously unknown intraspecific variation and additional species are likely to be detected. Thus, SSCPs provide valuable population genetic information which allele-specific amplification does not.     

Trophic behavior and biting activity of the two sibling species of the Anopheles minimus complex in western Thailand.

The trophic behavior and host preference of two sibling species, Anopheles minimus s.s. (= An. minimus species A) and species C, were observed during a two-year period at Pu Teuy Village, Sai Yok District, Kanchanaburi Province, western Thailand. Anopheles minimus s.s. and species C were more prevalent during the hot and wet periods of the year. Both species demonstrated exophagic and zoophilic activities. Feeding activity of An. minimus C was unique compared to An. minimus sensu lato from other localities in Thailand. Outdoor blood feeding by An. minimus C occurred throughout the night with one distinct feeding peak immediately after sunset (1800 h), whereas indoor feeding showed two small peaks at 2000 and 2400 h. The small number of An. minimus s.s collected during this study precluded a determination of peak activity patterns. A better understanding of mosquito behavior related to host and patterns of feeding activity will facilitate and improve the efficiency of vector control operations.     

Pelagostrobilidium neptuni (Montagnes and Taylor, 1994) and Strombidium biarmatum nov. spec. (Ciliophora, Oligotrichea): phylogenetic position inferred from morphology, ontogenesis, and gene sequence data

Morphological data from life, protargol impregnation, and scanning electron microscopy were combined with genetic data not only to describe the marine plankton ciliates Pelagostrobilidium neptuni (Montagnes and Taylor, 1994) Petz, Song, and Wilbert, 1995 and Strombidium biarmatum nov. spec., but also to elucidate their phylogenetic relationships. Additionally, the ontogenesis of P. neptuni was studied and the diagnosis of the genus Pelagostrobilidium was improved due to further data from the newly affiliated species P. epacrum (Lynn and Montagnes, 1988) nov. comb. (basionym: Strobilidium epacrum Lynn and Montagnes, 1988). The phylogenetic analysis of the small subunit ribosomal RNA genes matched the morphologic and ontogenetic assigning of P. neptuni to the choreotrichid family Strobilidiidae. The considerable genetic distance of d = 0.074 between P. neptuni and Strobilidium caudatum corroborated the morphological differences and thus the maintenance of the genus Pelagostrobilidium. Strombidium biarmatum nov. spec. is a typical member of the genus, except for the two types of extrusomes ("trichites"): ~12 × 0.5 μm, needle-shaped ones attached anterior to the girdle kinety and ~6 × 0.5 μm, rod-shaped ones at the distal end of the intermembranellar ridges. Its flask-shaped resting cysts have several strong spines. In accordance with the morphologic data, S. biarmatum is placed within the order Oligotrichida by gene sequence analysis. The great genetic distances within the oligotrichids support the diversity found in morphologic and ontogenetic studies.     

Molecular phylogeny of elopomorph fishes inferred from mitochondrial 12S ribosomal RNA sequences

Wang, C. H., Kuo, C. H., Mok, H. K. & Lee, S. C. (2003). Molecular phylogeny of elopomorph fishes inferred from mitochondrial 12S ribosomal RNA sequences. — Zoologica Scripta , 32 , 231–241.
Fishes of the superorder Elopomorpha include tenpounders ( Elops ), tarpon ( Megalops ), bonefishes ( Albula ), spiny eels ( Notacanthus ), apodes, and gulper eels; despite highly diversified morphological features, all undergo a leptocephalus larval stage and are thus treated (although with some dissenting views) as monophyletic. Following analysis of 12S rRNA sequences we present results that confirm a monophyletic Elopomorpha clearly separated from Clupeomorpha. Elops and Megalops share a common ancestor and are clustered in a subclade at the bottom of Elopomorpha. Albula and Notacanthus share a common ancestor forming the sister group to Anguilliformes. Saccopharyngiformes is not a sister group of Anguilliformes, as the single species sequenced here is nested deeply within the latter. Neither the suborder Congroidei nor the superfamily Congroidea within Anguilliformes are monophyletic.     

Molecular phylogenetic perspective on the evolution of the deep-sea fish genusCyclothone (Stomiiformes: Gonostomatidae)

A portion of mitochondrially encoded 12S and 16S ribosomal RNA genes were sequenced from 13 currently recognized species of the midwater deep-sea fish genusCyclothone (Stomiiformes: Gonostomatidae) and three gonostomatid outgroup taxa. Phylogenetic analyses using maximum parsimony and maximum likelihood methods were performed on unambiguously aligned, combined sequences (803 bp) of the two genes. The resultant tree topologies from the two methods were congruent, being robust and supported by various tree statistics, enabling the evolutionary history ofCyclothone to be described in detail. The molecular phylogeny demonstrated striking inconsistencies with previously proposed “natural groups”, although the latter could be confidently refuted by the molecular data. The most significant characteristic of the evolutionary history ofCyclothone was the independent acquisition of an apomorphic depth habitat from the relatively ancestral, lower mesopelagic habitat, by each of three major distinct lineages that had diverged earlier in their evolution. Moreover, such macroevolutionary habitat shifts had been necessarily accompanied by morphological and ecological novelties, presumably originating from paedomorphosis. Repeated evolution of such changes strongly suggests ontogenetic plasticity inCyclothone which could enable these fishes to acquire larval-like, simple organization of body structure. Such a body plan could help them subsist in food-poor surroundings and regulate reproductive variables that take advantage of increasing larval survival toward shallower depths. Recent speciation events, on the contrary, have produced contemporary sister species of allopatric (or microallopatric) distributions, but few morphological and ecological differences. Even if remarkable miniaturization has occurred, such as in the Mediterranean endemicC. pygmaea, it had to have been a simple truncation of ancestral species' ontogeny without attendance of any discernible paedomorphic features. On the basis of the fossil record, geological history of the Mediterranean region, and ectotherm molecular divergence rate, it was estimated thatCyclothone radiation had already started in the early-middle Miocene (17–20 million years ago).     

Phylogeny of a paradigm lineage: the Drosophila melanogaster species group (Diptera: Drosophilidae)

Although Drosophila melanogaster is a paradigm eukaryote for biology, relationships of this species and the other 174 species in the melanogaster species group are poorly explored and ambiguous. Gene regions of Cytochrome oxidase II (mt:CoII ), Alcohol dehydrogenase ( Adh ) and hunchback ( hb ) were sequenced and analysed phylogenetically to test prior hypotheses of relationships for the group based on chromosomes, morphology, and 28S rRNA gene sequences. A simultaneous cladistic analysis of the three newly sequenced gene regions produced a single well-resolved phylogeny for 49 exemplar species representing eight subgroups. Monophyly of each of the ananassae , melanogaster , montium , and takahashii subgroups is supported; the suzukii subgroup is polyphyletic. This phylogeny is consistent with variation in significant morphological structures, such as the male sex comb on the fore tarsus. The broad range of morphological variation among these species is interpreted and the applicability to evolution and developmental investigations is discussed. This phylogeny facilitates comparative investigations, such as gene family evolution, transposable element transmission, and evolution of morphological structures. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 76 , 21–37.     

Variable sexual ornaments in scarlet-tufted malachite sunbirds (Nectarinia johnstoni) on Mount Kenya

In order to be elaborated by sexual selection, sexual ornaments must vary perceptibly and genetically among individuals in natural populations. Rather little is known about ornament variation in monogamous species, in which sexual selection should act more weakly than in polygynous species. We report phenotypic variation in feather ornament size (elongated tails and pectoral tufts) and body size in the scarlet-tufted malachite sunbird Nectarinia johnstoni , a monogamous, sexually dimorphic nectarivore of East African alpine zones. Fully-expressed male ornaments are highly significantly more variable (CVs = 12–29%) than are skeletal and wing measures primarily affected by natural selection (CVs = 2 4%). Female sunbirds have pectoral tufts which are significantly (22–25%) smaller than those of adult males, but more variable (CV_s= 21–22%, CV_s= 12–15%), and more variable than body size. Among males with fully-grown ornaments, those with longer tails tend to have longer wings and wider tufts. The high variation in fully-grown ornaments in malachite sunbirds is consistent with the view that the ornaments are condition-dependent sexual signals. Finally, we review studies of feather ornament variation to date, and show that ornaments are much more variable in monogamous than non-monogamous species, apparently due to the relatively weak pressure of sexual selection.     

Larval habitats impose trait-dependent limits on the direction and rate of adult evolution in dragonflies

Natural selection on juveniles is often invoked as a constraint on adult evolution, but it remains unclear when such restrictions will have their greatest impact. Selection on juveniles could, for example, mainly limit the evolution of adult traits that mostly develop prior to maturity. Alternatively, selection on juveniles might primarily constrain the evolution of adult traits that experience weak or context-dependent selection in the adult stage. Using a comparative study of dragonflies, I tested these hypotheses by examining how a species’ larval habitat was related to the evolution of two adult traits that differ in development and exposure to selection: adult size and male ornamentation. Whereas adult size is fixed at metamorphosis and experiences consistent positive selection in the adult stage, ornaments develop throughout adulthood and provide context-dependent fitness benefits. My results show that species that develop in less stable larval habitats have smaller adult sizes and slower rates of adult size evolution. However, these risky larval habitats do not limit ornament expression or rates of ornament evolution. Selection on juveniles may therefore primarily affect the evolution of adult traits that mostly develop prior to maturity.     

Timing of ornament growth, phenotypic variation, and size dimorphism in two promiscuous African whydahs (Ploceidae: Vidua)

Variation within populations is a prerequisite for the action of selection on morphological traits. Darwin assumed that there was much greater variation in sexual ornament size than in body size, but this may not be generally true of natural populations. I analyse field data on variation in body size and the length, area and mass of tail ornaments in paradise (Vidua paradisaea) and shaft-tailed whydahs (V. regia). Whydahs are promiscuous, brood parasitic African finches with elaborate tail ornaments in breeding males. The short, unadorned tails of male shaft-tailed whydahs, which carry a wire-like tail ornament, are non-significantly (1%) longer than female tails, but male paradise whydahs, which carry a large, broad ornament, have unadorned tails 10% longer than those of conspecific females. Fully grown ornament length, mass and area vary little more (CVs = 1.8-6.4%) than male or female body size traits (CVs = 1.7-6.1%). Instead, there is high variation in the timing of ornament development during prenuptial moult (CVs = 30.8–39.5% for paradise whydahs and 12.6–23.8% for shaft-tailed whydahs when corrected to a standard date). This temporal variation in development probably has greater significance for sexual selection in whydahs than maximum ornament size.     

Geographical distribution of Anopheles minimus species A and C in western Thailand.

Elucidating vector distribution based on an accurate species identification is important to understanding the nature of the species complex in order to achieve vector control. Morphologically, An. minimus s.l. is difficult to distinguish from both its species complex and its closely related species. A polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique and a single multiplex-allele specific PCR developed for species identification were applied in this study in comparison with morphological identification. Both methods were used, combining with geographical information systems to determine the distribution of An. minimus species A and C. The investigation on the breeding habitats was performed in the malarious area of western Thailand. Anopheles larvae were collected from 36 bodies of water among five districts (Sangkhaburi, Thong Pha Phum, Si Sawat, Muang, and Sai Yok) of Kanchanaburi Province, Thailand. In this study, An. minimus A larvae were present in all study districts but the association differed when focusing on study sites within each district. Although there were many reports of An. minimus A in Ban Phu Rat and Ban Phu Toei villages in Sai Yok District, we did not find the breeding sites of species A in those two areas. An. minimus A and C were found in Ban Phu Ong Ka village in Sai Yok District. The breeding habitats of An. minimus C were present covering 30-40 km of distance in northern part of Sai Yok and this species was also found in the central and southern parts of Si Sawat District.     

Deep genetic divergences among morphologically similar and parapatric Skistodiaptomus (Copepoda: Calanoida: Diaptomidae) challenge the hypothesis of Pleistocene speciation

We used mitochondrial [cytochrome c oxidase subunit I (CO I ), cytochrome b , and 16S] and nuclear [internal transcribed spacer (ITS) phylogenies of Skistodiaptomus copepods to test hypotheses of Pleistocene divergence and speciation within the genus. Mitochondrial (mt)DNA sequence divergences do not support hypotheses for Pleistocene speciation and instead suggest much more ancient speciation events in the genus. Skistodiaptomus oregonensis and Skistodiaptomus pygmaeus (i.e. two morphologically similar and parapatric species) exhibited uncorrected mtDNA sequence divergences exceeding 20%. Similarly, we identified three divergent clades of Skistodiaptomus pallidus that exhibited mtDNA sequence divergences exceeding 15%, suggesting that even intraspecific divergence within this morphospecies predates the Pleistocene. We found clear evidence of CO I pseudogenes in S. pygmaeus , but their presence did not lead to significant overestimates of sequence divergences for this gene. Substitution saturation and strong purifying selection have most likely led to underestimates of sequence divergences and divergence times among Skistodiaptomus . The widespread phenomenon of morphological stasis among genetically divergent copepod groups indicates that speciation often occurs with little or no morphological change. Instead, morphological evolution may occur idiosyncratically after speciation and create discordant patterns of morphological similarity, shared ancestry and divergence time. Cryptic species complexes are therefore common in copepods, and morphological species concepts underestimate their true species diversity.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 150–165.     

Imitating the initial evolutionary stage of a tail ornament

Abstract.— Costs of a sexual ornament in its early evolutionary form and the relationship between these costs and individual condition may be an important influence in the likelihood of possible evolutionary mechanisms involved in the evolution of this ornament. We reconstructed the tail shape in hypothetical ancestors of recent hirundines (Aves: Hirundinidae), from which the elongation of tail feathers under sexual selection might have begun. By elongating the tail in sand martins ( Riparia riparia , Hirundinidae), we simulated the early evolution of a long forked tail–the typical ornament of male hirundines. Birds with initial ornament captured smaller insects than controls, which suggests that this ornament imposed a cost in terms of impaired foraging. Furthermore, birds with naturally longer tails were better able to cope with initial ornament than naturally short-tailed birds. If length of tail in sand martins indicates the quality of individuals, our results suggest higher costs of this initial ornament for poorer than for higher quality individuals. We discuss the potential role of the handicap principle and other mechanisms in early evolution of a tail ornament.     

Taxonomy and molecular phylogeny of Lethenteron lampreys in eastern Eurasia

Allozyme analyses of lampreys (genus Lethenteron ) in eastern Eurasia showed that samples of L. reissneri from the upper Amur River, Russia, possessed the diagnostic alleles of L. kessleri ( MDH‐3 *‐ 93 ). These samples were closely related to L. kessleri samples in the Ob, Lena and middle Amur Rivers and on Sakhalin and Hokkaido Islands. On the other hand, they were distantly related to samples of the northern and southern forms of L. reissneri in the Japanese Archipelago and the southern Korean Peninsula. The number of trunk myomeres in L. reissneri from the upper Amur (63–76) strongly overlapped the number in L. kessleri (64–73), but were markedly displaced from those of the northern (51–66) and southern forms (49–62). These results suggest that L. reissneri in the upper Amur basin is likely to be the same taxonomic entity as L. kessleri reported from eastern Eurasia. The genetic and morphological divergences from L. reissneri in the type locality make it appropriate to regard the northern and southern forms as distinct species, L . sp. N and sp. S. Despite the close relationships found among L. japonicum , the L. reissneri complex and L . sp. N, L . sp. S was highly divergent from other species of Lethenteron , Lampetra and Entosphenus . In the monophyletic group comprising L. japonicum , the L. reissneri complex and L . sp. N, the direction of life‐history evolution presumed from the most parsimonious character reconstruction on the molecular tree was inconsistent with the previous hypothesis that nonparasitic species arise from parasitic species, indicating the necessity of detailed assessment of characteristics. On the other hand, L . sp. S may be a relict species of the coancestor of Lethenteron , Lampetra and Entosphenus .     

Phylogeny and biogeography of the alpine newt Mesotriton alpestris (Salamandridae, Caudata), inferred from mtDNA sequences

In this paper, we performed phylogenetic analyses of Mesotriton alpestris populations from the entire range of species distribution, using fragments of two mtDNA genes, cytochrome b (309bp) and 16S rRNA ( approximately 500bp). Sequence diversity patterns and phylogenetic analyses reveal the existence of a relict lineage (Clade A) of late Miocene origin, comprising populations from south-eastern Serbia. This lineage is proposed to be ancestor to a western and an eastern lineage, which diverged during the middle Pliocene. The western lineage is further divided in two clades (Clades B, C) of middle Pliocene origin that represent populations from Italy (B) and populations from central Europe and Iberia (C). Further subdivision, dated back to the middle-late Pliocene, was found within the eastern lineage, representing southern (Clade D) and central-northern (Clade E) Balkan populations, respectively. Extensive sequence divergence, implying greater isolation in multiple refugia, is found within eastern clades, while the western clades seem to have been involved in the colonization of central, western and north-eastern Europe from a hypothetical refugium in central Europe. The extent of divergence does not support the current taxonomy indicating cryptic speciation in the Balkans, while paedomorphic lineages were found to have been evolved during early-middle Pleistocene probably as a response to the ongoing dramatic climatic oscillations.     

Patterns of morphological variation in two sexually dimorphic bird species with different tail shapes

Many studies have focused on tail ornamentation in birds, but not all tail shapes have been studied in depth. Graduated and pin tails have received less attention than forked tails, despite being more likely, in terms of aerodynamic theory, to be honest signals. We report morphological variation in live specimens of two sexually dimorphic passerines from the same site with different tail shapes: graduated (Cape sugarbird Promerops cafer ) and pin (orange-breasted sunbird Antobaphes violacea ). Coefficients of variation (CVs) were calculated for all morphological traits, both non-ornamental (range 1.91–5.72) and ornamental (range 5.83–21.71). Males and females did not differ in CV for any non-ornamental trait. Ornamental traits in males of both species were significantly more variable than all non-ornamental traits. Cape sugarbird ornamental traits were significantly more variable than those of orange-breasted sunbirds. The high levels of variation in graduated tails relative to pintails suggest that these traits have been driven mainly by sexual selection. In contrast, both constraining natural and multiple ornament selection could be responsible for the relatively low levels of variation in pintails.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 437–443.     

Phylogenetic relationships, taxonomy, character evolution and biogeography of the lacertid lizards of the genus Takydromus (Reptilia: Squamata): a molecular perspective

Historical relationships were inferred for the oriental lizards of the genus Takydromus Daudin 1802 (Lacertidae) on the basis of DNA sequences. Of the 17 species currently recognized for the genus, 13 species represented by 42 specimens from 29 localities were examined. Maximum-likelihood and maximum-parsimony analyses of data for 829 aligned sites from parts of the mitochondrial 12S and 16S rRNA genes yielded relationships that, while showing no substantial discrepancy with each other, were strikingly different from a currently prevailing phylogenetic hypothesis from a parsimony analysis of morphological characters. Based on the results of these molecular analyses, supplemented by results of the morphological analysis that offered robust evidence for positions of two additional species ( T. khasiensis and T. sylvaticus ), the following interrelationships were hypothesized as the most preferred phylogeny: ( kuehnei ( sexlineatus khasiensis ))( tachydromoides (( smaragdinus ( sauteri ( dorsalis sylvaticus ))) ( amurensis ((( formosanus wolteri ) hsuehshanensis )( toyamai ( septentrionalis stejnegeri )))))). These interrelationships indicate: (1) invalidity of Platyplacopus Boulenger 1917 , which was recently resurrected as a subgenus of Takydromus on the basis of the morphological analysis; (2) homoplasy in states of some morphological characters, such as green dorsal coloration, that were considered as synapomorphs of certain nodes in the morphological analysis; and (3) involvement of the genus in a series of vicariances in both the continental and insular parts of eastern Eurasia. Due to the paucity of available samples, phylogenetic status of T. intermedius and T. haughtonianus remain to be examined in future studies.  © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 76 , 493–509.     

The nonsynonymous/synonymous substitution rate ratio versus the radical/conservative replacement rate ratio in the evolution of mammalian genes

There are 2 ways to infer selection pressures in the evolution of protein-coding genes, the nonsynonymous and synonymous substitution rate ratio (K(A)/K(S)) and the radical and conservative amino acid replacement rate ratio (K(R)/K(C)). Because the K(R)/K(C) ratio depends on the definition of radical and conservative changes in the classification of amino acids, we develop an amino acid classification that maximizes the correlation between K(A)/K(S) and K(R)/K(C). An analysis of 3,375 orthologous gene groups among 5 mammalian species shows that our classification gives a significantly higher correlation coefficient between the 2 ratios than those of existing classifications. However, there are many orthologous gene groups with a low K(A)/K(S) but a high K(R)/K(C) ratio. Examining the functions of these genes, we found an overrepresentation of functional categories related to development. To determine if the overrepresentation is stage specific, we examined the expression patterns of these genes at different developmental stages of the mouse. Interestingly, these genes are highly expressed in the early middle stage of development (blastocyst to amnion). It is commonly thought that developmental genes tend to be conservative in evolution, but some molecular changes in developmental stages should have contributed to morphological divergence in adult mammals. Therefore, we propose that the relaxed pressures indicated by the K(R)/K(C) ratio but not by K(A)/K(S) in the early middle stage of development may be important for the morphological divergence of mammals at the adult stage, whereas purifying selection detected by K(A)/K(S) occurs in the early middle developmental stage.