Subtle Morphological Differences Research Articles

APPLICATION OF PHYLOGENETIC PRINCIPLES TO TESTING EVOLUTIONARY SCENARIOS: A COMMENT ON KACZMARSKA ETAL. "MOLECULAR PHYLOGENY OF SELECTED MEMBERS OF THE ORDER THALASSIOSIRALES (BACILLARIOPHYTA) AND EVOLUTION OF THE FULTOPORTULA"(1).

While rigorous techniques have usually been used to generate phylogenetic trees from molecular data, morphological analysis has sometimes been more informal. A recent example was a study of the evolution of the fultoportula in the diatom order Thalassiosirales (Kaczmarska etal. 2006). Phylogeny was inferred using modern phylogenetic principles applied to nuclear SSU rDNA sequences, but inferences about morphological character evolution were made using noncanonical reasoning and evolutionary scenario building. The preferred hypothesis posited that marginal fultoportulae evolved from the marginal ridge of Lithodesmiales. A related hypothesis suggested that fultoportulae in the valve center were not homologous with those near the valve margin. Shared symplesiomorphies, shared homoplasies, gaps in the fossil record, and subtle morphological differences between central- and marginal-area fultoportulae were offered as the primary evidence for these scenarios. The literature has demonstrated such arguments to be either irrelevant or logically weaker than inferences made under the tests of similarity, conjunction, and congruence. Five prior hypotheses about the origin and evolution of the fultoportula were examined in this study using these tests. The hypothesis that the areola evolved into the multistrutted process, which evolved into the fultoportula, was best supported.

Mitochondrial DNA Variation and Systematics of the Guanaco (Lama guanicoe, Artiodactyla: Camelidae)

Guanacos (Lama guanicoe) are the most important native herbivorous species in the South American steppes and the dominant ungulate in a fauna rich in rodents but poor in large mammal species. Between 2 and 4 subspecies are usually recognized within Lama guanicoe, based on subtle morphological differences and geographic distribution. To evaluate whether molecular variation is consistent with the latter hypotheses, we analyzed the complete cytochrome-b and partial control region mitochondrial DNA sequences of L. guanicoe from 22 localities in Peru, Bolivia, Argentina, and Chile. Sequence analyses of both genes support the monophyly of the species but failed to distinguish the occurrence of subspecies along the geographic range. Despite that, the northernmost populations (Peru and northern Chile) showed some degree of genetic differentiation with respect to southern representatives from Argentina, Bolivia, and rest of Chile. Analysis of genetic diversity also showed a strong signal of past low population size and a recent population expansion.

Effects of 1‐MCP applied postharvest on epicuticular wax of apples (Malus domestica Borkh.) during storage

AbstractBACKGROUND: Certain apple cultivars develop a greasy feel when overripe. Treating fruits with the ripening inhibitor 1‐methylcyclopropene (1‐MCP, SmartFresh™) reduces fruit greasiness. This study examines the nature of this phenomenon. ‘Royal Gala’ apples were treated with 1‐MCP at 1.0 µl L−1 following harvest. Periodically, during storage at − 1 °C for up to 6 months, fruits were evaluated for internal ethylene concentration, fruit epicuticular wax morphology (using scanning electron microscopy) and non‐polar organic solvent‐extractable (NPOSE) wax constituents of the cuticle (using gas chromatography/mass spectrometry).RESULTS: In 2004, 1‐MCP strongly inhibited internal ethylene production; however, total weight of NPOSE wax during storage was unaffected by treatment. In 2005, several wax constituents present in both ‘Autumn Gold’ and ‘Royal Gala’ showed differences during storage. In 2006, cuticular wax constituents comprising 80% of the total from ‘Royal Gala’ showed no treatment differences. Although several minor constituents did exhibit differences within treatment and sampling date, these did not appear sufficient to cause the subtle differences in surface wax morphology.CONCLUSION: 1‐MCP strongly inhibited ethylene production and delayed development of certain wax constituents thought responsible for fruit greasiness during cold storage. Subtle differences in surface wax morphology appeared unrelated to wax production. Published in 2008 by John Wiley & Sons, Ltd.

Pseudanthessius tortuosus Stock, 1967 (Copepoda: Cyclopoida) from the amphinomid polychaete Hermodice carunculata (Pallas) in the western Caribbean

The copepod order Cyclopoida contains mainly forms that have been found as symbionts of different vertebrate and invertebrate hosts. One of these groups is the family Pseudanthessiidae, found mainly on echinoderms but very rarely on polychaetes. In this contribution, we report and confirm the occurrence of the pseudanthessiid copepod Pseudanthessius tortuosus Stock, 1967 as a symbiont of the benthic amphinomid polychaete Hermodice carunculata (Pallas) in the western Caribbean. These specimens showed subtle morphological but important size differences with respect to the specimens from the type-locality in the eastern Caribbean. Data are provided on the sex-ratio, the distribution of the copepods on the polychaete body and the finding of pairs in amplexus. The position of the copepods on the body, mainly on the dorsal branchiae, rather than on the lateral ones, allows them to avoid the friction related to the displacement mechanism of the polychaete, involving the lateral branchiae. This is the first record of the species and the symbiotic association in the western Caribbean and in Mexican waters. It is also recorded herein for the first time in the US Virgin Islands, near the type-locality. Hitherto, P. tortuosus has not been recorded since its original description forty years ago. This finding supports the hypothesis that this copepod is associated to H. carunculata throughout the entire Caribbean Basin, but its relation with other amphinomids remains unconfirmed.

Species recognition and phylogeny of Thelotrema species in Australia (Ostropales, Ascomycota)

Species circumscriptions based on morphological data are difficult in crustose lichens with limited characters as they often show remarkable variability. An example is the genus Thelotrema s.str., a speciose genus of mostly tropical lichens. Morphological studies on Australian Thelotrema spp. were accompanied by a phylogenetic analysis of mt SSU rDNA sequence data of 19 species, including 25 newly obtained sequences. We performed maximum parsimony and Bayesian phylogenetic analyses of 50 samples, representing 25 species. Our results indicate that more species need to be accepted in Thelotrema than previously thought. Subtle morphological differences were found to be associated with independent lineages in the phylogenetic trees. Furthermore, monophyly of Thelotrema s.str. is strongly supported. On the basis of the corroboration of morphological evidence by molecular data, the new species Thelotrema capetribulense Mangold, T. crespoae Mangold, Lumbsch & Elix, T. oleosum Mangold, and T. pseudosubtile Mangold are described. The new combinations Chapsa phlyctidioides (Müll.Arg.) Mangold and Thelotrema defossum (Müll.Arg.) Mangold are proposed.

Sublimation behavior of SiO2 from low- and high-index silicon surfaces

The authors have used atomic force microscopy to investigate the sublimation behavior of 100-nm-thick oxide layers from the low-index Si(001) and Si(111) surfaces, as well as the stable, high-index Si(113) and Si(5 5 12) surfaces. Similar to previous thin-film (<50nm) sublimation studies, high vacuum annealing results in the formation of circular voids that grow laterally with annealing time (1–6min, 1150–1350°C). The depth of these voids is ∼200nm, or twice the thickness of the original oxide film, which is consistent with the thermal decomposition of SiO2 to form volatile SiO. There are subtle morphological differences, however, between the voids formed on the different surface orientations. Line profiles of the bottom Si surfaces inside the voids indicate flat terraces for the (111) and (113) orientations and sloped conic sections for the (001) and (5 5 12) orientations, indicating that the latter surfaces are less stable with respect to step formation during oxide sublimation. At the centers of voids, features such as deep pits (5μm diameter, 200–700nm depth) or vertical structures (1μm diameter, up to 700nm height) are present. Deep depressions are also observed at vertical sidewalls that occur during sequential anneals or on a patterned surface. After the thick oxide is completely desorbed, an undulating surface morphology occurs on all surface orientations due to the coalescence of the void sidewalls.

A review of the Tripterygion tripteronotus (Risso, 1810) complex, with a description of a new species from the Mediterranean Sea (Teleostei: Tripterygiidae)

We compared specimens of Tripterygion tripteronotus from 52 localities of the Mediterranean Sea and adjacent waters, using four gene sequences (12S rRNA, tRNA-valine, 16S rRNA and COI) and morphological characters. Two well-differentiated clades with a mean genetic divergence of 6.89±0.73% were found with molecular data, indicating the existence of two different species. These two species have disjunctive geographic distribution areas without any molecular hybrid populations. Subtle but diagnostic morphological differences were also present between the two species. T. tripteronotus is restricted to the northern Mediterranean basin, from the NE coast of Spain to Greece and Turkey, including the islands of Malta and Cyprus. T. tartessicum n. sp. is geographically distributed along the southern coast of Spain, from Cape of La Nao to the Gulf of Cadiz, the Balearic Islands and northern Africa, from Morocco to Tunisia. According to molecular data, these two species could have diverged during the Pliocene glaciations 2.7-3.6 Mya.

How Neanderthal molar teeth grew

Growth and development are both fundamental components of demographic structure and life history strategy. Together with information about developmental timing they ultimately contribute to a better understanding of Neanderthal extinction. Primate molar tooth development tracks the pace of life history evolution most closely, and tooth histology reveals a record of birth as well as the timing of crown and root growth. High-resolution micro-computed tomography now allows us to image complex structures and uncover subtle differences in adult tooth morphology that are determined early in embryonic development. Here we show that the timing of molar crown and root completion in Neanderthals matches those known for modern humans but that a more complex enamel-dentine junction morphology and a late peak in root extension rate sets them apart. Previous predictions about Neanderthal growth, based only on anterior tooth surfaces, were necessarily speculative. These data are the first on internal molar microstructure; they firmly place key Neanderthal life history variables within those known for modern humans.

Phylogeography of Calanus helgolandicus and the Black Sea copepod Calanus euxinus, with notes on Pseudocalanus elongatus (Copepoda, Calanoida)

Abstract Calanus helgolandicus is a widespread epipelagic copepod species whose geographical range extends from the temperate Atlantic Ocean to the northern Mediterranean Sea. Calanus euxinus, recently designated as a distinct species though closely related to C. helgolandicus, occurs in the Black Sea. Very subtle morphological differences distinguish the two species. Pseudocalanus elongatus has a similar geographic range including North Atlantic Ocean, Mediterranean Sea and the Black Sea. In this study, population genetic variation of C. helgolandicus, C. euxinus and P. elongatus was investigated using DNA sequence variation of 540 base pair (Calanus spp.) and 575 base pair (P. elongatus) regions of mitochondrial cytochrome oxidase I (mtCOI) gene. C. helgolandicus was collected from the English Channel, the Adriatic Sea, and C. euxinus was collected from various regions of the Black Sea. P. elongatus was collected from the English Channel and the Black Sea. Intraspecific differentiation in mtCOI was χ 2 = 3.94 , P 0.0001 ). The haplotype diversity was high for all species: C. euxinus ( h = 0.92 ), C. helgolandicus ( h ⩽ 0.80 ), P. elongatus ( h ⩽ 0.60 ). No haplotype sharing was reported for different locations of P. elongatus, whereas the presence of haplotype sharing between C. helgolandicus and C. euxinus was remarkable. The size distribution in terms of prosome length measurements was found to be region-specific. The lack of phylogenetic differentiation between the Calanus species pair may suggest ancestral polymorphisms. The morphological and genetic similarities between C. euxinus and C. helgolandicus raise new questions about the status of C. euxinus as a different species.

Monomethylarsonous acid induces transformation of human bladder cells

Arsenic is a human bladder carcinogen. Arsenic is methylated to both monomethyl and dimethyl metabolites which have been detected in human urine. The trivalent methylated arsenicals are more toxic than inorganic arsenic. It is unknown if these trivalent methylated metabolites can directly cause malignant transformation in human cells. The goal of this study is determine if monomethylarsonous acid (MMA(III)) can induce malignant transformation in a human bladder urothelial cell line. To address this goal, a non-tumorigenic human urothelial cell line (UROtsa) was continuously exposed to 0.05 muM MMA(III) for 52 weeks. Hyperproliferation was the first phenotypic change observed in exposed UROtsa (URO-MSC). After 12 weeks of exposure, doubling time had decreased from 42 h in unexposed control cells to 27 h in URO-MSC. Hyperproliferation continued to be a quality possessed by the URO-MSC cells after both 24 and 52 weeks of exposure to MMA(III), which had a 40-50% reduction in doubling time. Throughout the 52-week exposure, URO-MSC cells retained an epithelial morphology with subtle morphological differences from control cells. 24 weeks of MMA(III) exposure was required to induce anchorage-independent growth as detected by colony formation in soft agar, a characteristic not found in UROtsa cells. To further substantiate that malignant transformation had occurred, URO-MSC cells were tested after 24 and 52 weeks of exposure to MMA(III) for the ability to form tumors in SCID mice. Enhanced tumorigenicity in SCID mouse xenografts was observed after 52 weeks of treatment with MMA(III). These observations are the first demonstration of MMA(III)-induced malignant transformation in a human bladder urothelial cell line and provide important evidence that MMA(III) may be carcinogenic in human tissues.

ALK expression in pseudosarcomatous myofibroblastic proliferations of the genitourinary tract

Pseudosarcomatous myofibroblastic proliferation of the genitourinary tract is rare and may develop after trauma or spontaneously. The aim of this study was to characterize further the clinicopathological features of these lesions and to examine their relationship to inflammatory myofibroblastic tumour (IMT). Twenty-seven cases of pseudosarcomatous myofibroblastic proliferation were analysed. There were seven males and 20 females; median age was 37 years (range 16-88). Most lesions were from the bladder (n = 21), while others were in the urethra, vulva, vagina, rectum and retrovesical space. Median tumour size was 30 mm (range 6-120 mm). Seven cases (25%) had a history of prior trauma or surgery. Three cases recurred locally but not destructively. The tumours had fasciitis-like features including bland spindle cells with evenly distributed chromatin, admixed inflammatory cells (mainly lymphocytes) and often a myxoid stroma. Immunohistochemistry showed positivity for smooth muscle actin in 14/20 cases, keratin in 8/19, desmin in 7/20 and anaplastic lymphoma kinase (ALK) in 10/21 cases. Fluorescent in situ hybridization was performed in six ALK+ cases; all were negative for ALK gene rearrangement. Pseudosarcomatous myofibroblastic proliferations of the genitourinary tract may show ALK immunopositivity but do not show consistent ALK rearrangement. Given subtle morphological differences and more consistently benign behaviour, their relationship to inflammatory myofibroblastic tumour at other sites remains uncertain.

Australia's wasp-pollinated flying duck orchids revised (Paracaleana: Orchidaceae)

We uphold the generic rank of Paracaleana on the basis of its divergent pollination syndrome (sexual deception of male thynnid wasps compared with pollination of Caleana by male sawflies), recent DNA sequence data demonstrating monophyly, and nomenclatural stability. Ten of the 13 species recognised herein are new, all endemic to the South-west Australian Floristic Region: Paracaleana alcockii, P. brockmanii, P. dixonii, P. gracilicordata, P. granitica, P. hortiorum, P. lyonsii, P. parvula, P. terminalis and P. triens. Although some of these taxa have subtle morphological differences, primarily of labellum morphology, evidence from other Australian orchid genera whose flowers sexually deceive wasp pollinators indicates that reproductive isolation is probable among close sister taxa in Paracaleana. Moreover, phenological, ecological and geographical differences help separate morphologically close sister taxa. P. disjuncta D.L. Jones is considered to extend from Victoria and South Australia west into the South-west Australian Floristic Region, where James Drummond first collected the species, probably in 1838. Additional research is needed on pollinators, molecular phylogeny, possibly undescribed taxa within P. nigrita and on the few putative hybrids identified in the genus.

Parallel Evolution, not Always so Parallel: Comparison of Small Benthic Charr, Salvelinus alpinus, from Grímsnes and Thingvallavatn, Iceland

Iceland is unique in terms of geologically young freshwater systems and rapid adaptations of fresh water fishes to diverse habitats, e.g. lava with ground water flow. Iceland has six species of freshwater fishes, including Arctic charr, Salvelinus alpinus. Previous research has shown great diversity within this species. Four different morphs of Arctic charr are found in one lake, Thingvallavatn, including a small benthivorous charr. Similar populations of small benthic charr are known from several other Icelandic freshwater locations, including Nautavakir in Grimsnes. Our comparison of the small benthic charr morphs in Thingvallavatn and in Grimsnes showed that they are similar in morphology but distinguishable in several characteristics. Small benthic charr in Grimsnes and Thingvallavatn demonstrate similar adaptations and are an example of parallel evolution. However, subtle morphological differences between them indicate further specialized adaptations at each location.

Shape of the Lateral Mandibular Outline in Lemuridae: A Quantitative Analysis of Variability Using Elliptical Fourier Analysis

While several morphometric analyses in lemurids have focused on the craniofacial complex, the characterization of their mandibular morphology has received less attention. The mandibular outline, in lateral perspective, was quantified using elliptical Fourier analysis, in an osteological sample encompassing 189 lemurid mandibles (66 Eulemur, 51 Hapalemur, 22 Lemur and 50 Varecia), and compared using multivariate statistical techniques. The taxonomic value of this outline in Lemuridae was demonstrated by the existence of significant separations between the four genera studied. In particular, the mandibular morphology of Hapalemur was markedly different from that in the group Eulemur-Lemur-Varecia. Excluding Hapalemur from analysis, the distinctions between Eulemur, Lemur and Varecia were enhanced suggesting the existence of more subtle intergeneric differences in mandibular morphology. Variation in mandibular form was greatest in Hapalemur and smallest in Eulemur and Varecia (as demonstrated by the mean values of interindividual distances); variation was higher in Lemur than in Eulemur and Varecia, but not higher than in Hapalemur. This morphological diversity may be related to functional adaptation in response to particular dietary habits. The patterns of intergeneric and intrageneric shape variations of the mandible in Lemuridae presented here provide a valuable resource for the analysis of variation among living and fossil lemurids.

A description of the song of Isophya modesta modesta (Frivaldszky 1867) with notes on its relationship to I. modesta rossica Bey-Bienko, 1954

Abstract Acoustic signals used during the pair-forming behavior of Isophya modesta modesta are described for the first time. Specimens from Hungary, Rumania and the Ukraine have been studied. The male calling song of I. m. modesta is composed of single syllables. Each syllable consists of a shorter main impulse-series (120 to 240 ms) and a longer terminal impulse-series (200 to 2500 ms), separated from each other by a silent interval of 4 to 9 s. Uniquely in I. m. modesta, females can produce 2 response songs during 1 syllable of the male: after the male's main impulse-series, and most frequently, after the terminal impulse-series. Playback experiments revealed that the second female response song is related to the end of the male's terminal impulse-series. I. m. modesta and I. m. rossica were formerly regarded as two different species only subtle morphological differences being known between the 2 taxa. But as the male calling songs are apparently identical, and with the present state of our knowledge, i...

Epithelial Lesions Associated with Invasive Penile Squamous Cell Carcinoma: A Pathologic Study of 288 Cases

A heterogeneous spectrum of epithelial alterations and atypical lesions affect the squamous epithelium of penile mucosal anatomical compartments. Analogous to other genital sites, the terminology utilized to define the lesions is variable. The few pathologic studies of penile precancerous lesions are mostly related to carcinoma in situ and human papilloma virus (HPV), and the information on low-grade atypical lesions is limited. The objective of this study was to comprehensively describe the morphologic features of all epithelial alterations, benign and atypical, low grade and high grade, associated with invasive squamous cell carcinoma of the penis and to investigate their relation with each other and with subtypes of invasive carcinoma. We also propose herein a simple and reproducible nomenclature for penile precancerous abnormalities until more biological, molecular, or epidemiologic information on the lesions is available. Two hundred and eighty-eight penectomy and circumcision specimens with invasive squamous cell carcinoma were pathologically evaluated. Carcinomas were classified as usual, verrucous, papillary not otherwise specified, warty (condylomatous), basaloid, and mixed. Associated lesions were classified as squamous hyperplasia and squamous intraepithelial lesions of low and high grade (LGSIL and HGSIL). In LGSIL, atypia was confined to the lower third, and in HGSIL, atypical cells affected at least two thirds of the squamous epithelium. Subtypes of SIL were squamous, warty, basaloid, warty-basaloid, and papillary. Squamous hyperplasia, the most common lesion, was found in 83% of the cases, followed by LGSIL (59%) and HGSIL (44%). In 62% of the cases more than 1 associated lesion was present per specimen. A sequence from squamous hyperplasia to low-grade to high-grade SIL was seen frequently. Squamous hyperplasia was more commonly associated with usual squamous, papillary, and verrucous than with warty and basaloid invasive carcinomas. LGSIL was associated with all types of squamous cell carcinoma but was rarely present adjacent to basaloid or verrucous tumors. HGSIL was present in two thirds of invasive warty, basaloid, and mixed warty-basaloid tumors, in about half of usual squamous cell carcinomas, and was absent in papillary and verrucous carcinomas. Correlation of special types of invasive carcinomas with subtypes of SIL revealed morphologic correspondence of invasive tumor and the associated intraepithelial lesion. Squamous LGSIL was preferentially associated with verrucous, papillary, and usual squamous cell carcinomas; warty LGSIL, with invasive warty and mixed warty-basaloid carcinomas. High-grade SIL of the squamous type was frequently found in squamous cell carcinoma of usual type but was rarely present with warty or basaloid carcinomas. Basaloid HGSIL was associated with basaloid carcinoma, and HGSIL of warty type, with either warty or mixed warty-basaloid carcinomas. The high frequency of squamous hyperplasia and LGSIL and preferential association with usual, verrucous, and papillary carcinomas plus the subtle morphologic differences of the 2 lesions suggest that, despite its benign appearance, squamous hyperplasia is a precursor of the aforementioned carcinomas. The association and histologic similarities between high-grade SIL of the basaloid, warty, or mixed forms with their invasive counterparts indicate these lesions are their likely precursors.

Analysis of Intracranial Volume in Apert Syndrome Genotypes

Objective: Apert syndrome is caused by a mutation of the fibroblastic growth factor type 2 gene and in nearly all of the cases where the mutation has been identified it occurs in one of two adjacent sites of the gene, either position 252 or position 253. There is currently uncertainty whether a worse neurosurgical outcome occurs in association with a particular genotype. We investigated whether there were clinically subtle (but relevant) morphological differences in the craniofacial skeleton, which would result in differences in the intracranial volume, which might account for apparent differences in surgical outcome. Method: Three-dimensional CT scans of pre-operative Apert syndrome whose genotype had been identified had the intracranial volume measured using the Cavalieri estimator with correction for partial voluming effects. The values were compared to age and sex normals and then the two genotypes compared. Results: Intracranial volumes were measured for 22 cases, 16 with the 252 mutation and 6 with the 253 mutation. Conclusions: All cases except two had greater than their sex- and age-adjusted mean normal intracranial volumes. For the 252 and 253 genotypes there were no discernible differences in intracranial volumes between the two genotypes.

Species identity of geographically distinct populations of the glassy-winged sharpshooter parasitoid Gonatocerus ashmeadi: morphology, DNA sequences, and reproductive compatibility

Abstract Gonatocerus ashmeadi is a common and seemingly widespread egg parasitoid of Homalodisca coagulata , the glassy-winged sharpshooter (GWSS). Location records for G. ashmeadi indicate its natural range to be the southeastern USA and northeastern Mexico (which coincides with the presumed native range of GWSS), and possibly southern and central California (CA) (the adventive range of GWSS). The purpose of our work was to determine whether G. ashmeadi in the USA and northeastern Mexico is one species or a complex of reproductively incompatible sibling species. We used three approaches to determine the species identity of different G. ashmeadi populations: (1) reassessment of key morphological features using scanning electron microscopy (SEM) to determine if subtle morphological differences exist between G. ashmeadi populations which could indicate species differences; (2) to determine if molecular differences exist between G. ashmeadi populations collected from different regions by comparing mitochondrial and ribosomal DNA sequences; (3) mating compatibility studies to determine if different populations of G. ashmeadi are reproductively isolated, or if mating occurs, whether offspring are viable thereby defining species groups on the basis of successful interbreeding. Results from these three areas (morphology, DNA sequences, and reproductive compatibility) have been evaluated collectively; leading us to the conclusion that G. ashmeadi as it is currently viewed is a valid species and not an aggregate of morphologically indistinguishable cryptic species.

Serrated colorectal polyps: emerging evidence suggests the need for a reappraisal.

A set of polyps that superficially resemble ordinary hyperplastic polyps of the left colon but with divergent morphology and probably divergent biology has become apparent. Such polyps differ from typical small left-sided hyperplasic polyps by the large sizes they may attain, their tendency to be right-sided, and subtle morphologic differences. It is important to separate these polyps, which some have called "sessile serrated polyps" from hyperplastic polyps as they are associated with progression to carcinoma probably through mismatch repair defects.

Two New Species of <i>Monstrillopsis</i> Sars (Crustacea: Copepoda: Monstrilloida) from the White Sea and Norway, with Comments on <i>M. dubia</i> Scott

A new species of monstrilloid copepod, Monstrillopsis ferrarii n. sp., based on four adult female specimens collected in the White Sea, northern Russia, is described and illustrated. The new species is most closely related to M. dubia Scott from Scotland and the Mediterranean and M. dubia (sensu Sars, 1921) from Norwegian fjords. The latter is considered to represent a distinct species, described herein as M. dubioides n. sp. It differs from M. dubia in characters related to antennule length compared to body length, but mainly to the shape and relative size of the genital double somite and other urosomal somites. Records of M. dubia in Norway and off Lisbon are referable to M. dubioides n. sp. On the other hand, M. ferrarii n. sp. differs from M. dubia, M. dubioides, and the other species of the genus by a combination of characters, including 1) two rounded protuberances in the cephalic area, flanking the ocelli; 2) a wide zone of transverse cuticular striations encircling the cephalic area; 3) very long exopodal setae on the fifth legs, with no distal elongation of the exopodal lobe beyond the setal bases; 4) a relatively long genital double somite with the margins of the anterior half produced laterally; and 5) the nearly equal sizes of the anal somite and the preceding somite. It is considered that M. dubia and related forms represent a species complex with subtle morphological differences and a wide distribution. This is the first record of a species of Monstrillopsis in Russia and the sixth species of this order to be recorded in polar environments.