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1.
Approximately 1–2% of the tropical abalone Haliotis asinina inhabiting Heron Island Reef are infected with opecoelid digeneans. These largely inhabit the haemocoel surrounding the cerebral ganglia and digestive gland–gonad complex, and infected abalone typically have significantly reduced or ablated gonads. Observations of infected abalone reveal two distinct cercarial emergence patterns, one which correlates tightly with the abalone’s highly regular and synchronous fortnightly spawning cycle, and the other which occurs in a circadian pattern. The former appears to be a novel emergence strategy not previously observed in digeneans. While the cercariae in all abalone are morphologically indistinguishable, comparison of sequences from the internal transcribed spacer 2 (ITS 2) region of the ribosomal DNA reveals a 5.7% difference between cercariae displaying different emergence patterns, indicating these are two distinct species that probably belong to the same genus. The ITS 2 sequences of the species with the daily emergence pattern are identical to that of an undescribed adult opecoelid from the gut of the barramundi cod, Cromileptes altivelis. Combined molecular, morphological and emergence data suggest that while these opecoelid cercariae use the same first intermediate host and are closely related species—members of the genus Allopodocotyle—they fill different ecological niches that are likely to include different definitive hosts. 相似文献
2.
Greg W. Rouse Nerida G. Wilson Shana K. Goffredi Shannon B. Johnson Tracey Smart Chad Widmer Craig M. Young Robert C. Vrijenhoek 《Marine Biology》2009,156(3):395-405
We report observations on spawning and early development in bone-eating worms of the genus Osedax. Individual females of Osedax rubiplumus were observed at 1820 m depth freely spawning hundreds of oocytes, and females of an undescribed species, Osedax “orange collar”, were observed spawning in laboratory aquaria. Cytological and molecular analysis of the spawned oocytes
of two Osedax species revealed no evidence for the bacterial endosymbionts that the female worms require for their nutrition, suggesting
that the bacteria must be acquired later from the environment, as they are in other siboglinids. Individual O. “orange collar” females released an average of 335 (±130) eggs per day, but the number of oocytes spawned per day varied
greatly, suggesting that not all the females spawned daily. Fertilization rates of the spawned oocytes varied from 0 to 100%,
though most females showed nearly 100% fertilization rates. Oocytes spawned in the laboratory at 4–6°C were negatively buoyant.
If fertilized, these oocytes extruded polar bodies and then after at least four hours cleaved unequally. Subsequent cleavages
occurred in a spiral pattern at roughly 2-h intervals, resulting in free-swimming trochophore larvae after 24 h. These lecithotrophic
trochophores swam for 9–16 days before settling with several hooked chaetae, similar to those of dwarf Osedax males. The larval life span of the Osedax species studied in the laboratory appears to be shorter than in closely related Vestimentifera. Osedax rubiplumus, on the other hand, has much larger oocytes and so may have greater dispersal potential than these other Osedax species. The high fecundity and apparently continuous reproduction of Osedax boneworms permits the opportunistic exploitation of sunken vertebrate bones.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
3.
Most species of benthic marine invertebrates have a single mode of larval development. Poecilogonous species are those that produce more than one type of larval offspring. Reports of variable development within one species, especially in combination with widely differing ecological habitat, are frequently attributed to cryptic species. The spionid polychaete Boccardia proboscidea Hartman, 1940 exhibits development that varies both within a single brood and among broods produced by different females. Some females have planktotrophic development and produce many small larvae with a 2 week planktonic period before metamorphosis. Other females produce broods containing both planktotrophic larvae as well as nurse-egg-ingesting (adelphophagic) offspring that hatch as juveniles. Molecular analysis (RAPD-PCR) showed that a significant proportion of genetic variance is attributable to geographic origin, and not to developmental type. Adults of both developmental types showed no consistent differences in taxonomically important features (e.g. type and arrangement of chaetae, modified fifth setiger, caruncle, branchiae, pygidium) when examined with SEM. These data support the hypothesis that developmental variability in this species is a case of poecilogony, and is not attributable to cryptic species. Received: 21 April 1998 / Accepted: 20 April 1999 相似文献
4.
Nuclear ITS region of the alga Heterosigma akashiwo (Chromophyta: Raphidophyceae) is identical in isolates from Atlantic and Pacific basins 总被引:1,自引:0,他引:1
L. B. Connell 《Marine Biology》2000,136(6):953-960
The internal transcribed spacer (ITS) region from 19 isolates of the algal genus Heterosigma (Chromophyta: Raphidophyceae) was amplified by polymerase chain-reaction (PCR) and sequenced. Isolates were obtained from
both the Atlantic and Pacific basins, including Europe, eastern North America, western North America, Japan and New Zealand.
This study presents evidence that all Heterosigma isolates in this study are representatives of one species (H. akashiwo). All 19 isolates, except one (LB 2005) had identical ITS sequence (98.31% similar by pairwise comparison); Isolate LB 2005
may represent a separate subspecies. Such high degree of ITS sequence identity implies that the organism has spread between
oceanic regions in geologically recent times, possibly by human means. In addition to those from Heterosigma spp., the ITS regions from other marine Raphidophyceae (Chattonella antiqua, C. marina, C. subsalsa, Fibrocapsa japonica, and Olisthodiscus luteus) were amplified and sequenced using PCR. Total ITS lengths differed among the Raphidophyceae (C. antiqua, 577 base pairs (bp); C. marina, 577 bp;. C. subsalsa, 579 bp; F. japonica, 830 bp; H. akashiwo, 561 and 563 bp; O. luteus, 829 bp), but 5.8S rDNA sequences were similar in size (13 to 142 bp). The high ITS sequence identity between C. antiqua and C. marina (>99.9% by pairwise comparison) suggests the need for a taxonomic review of these species encompassing all morphological,
genetic, physiological and biochemical information. Additionally, a number of cultures of Raphidophyceae were positively identified.
In general, ITS comparisons among the Raphidophyceae may be most useful at the level of species determination rather than
at the population level.
Received: 12 July 1999 / Accepted: 16 March 2000 相似文献
5.
The Chilean gastropods Crepipatella dilatata and C. fecunda have different development modes: brooding and direct development in C. dilatata and brooding and planktotrophic development in C. fecunda. Unlike many other congeneric invertebrate species pairs, recent genetic evidence suggests that C. fecunda may have evolved from C. dilatata. To explore the changes involved in this unusual evolutionary path, this study examined the biochemical, energetic, and morphological
characters during early development of both species. Mean egg size was slightly smaller for the direct-developing species
C. dilatata, and initial energy content was lower—by about 27%—for eggs of that species. In both species, protein content in the eggs
was the principal biochemical component. Although females of C. fecunda produce 180 times more eggs than C. dilatata, females of C. dilatata invest 20 times more energy in each of their offspring, through nurse eggs; their embryos have approximately eight times
more energy at hatching and about 5 times more energy when they enter the benthos, despite a long planktonic feeding period
in the larvae of C. fecunda. Evolutionary switching between modes of development in these species is reflected in shifts in maternal energy investment. 相似文献
6.
Early development was examined, under various salinities, for two sympatric nereidid polychaetes, Hediste japonica and H. diadroma, which participated in a simultaneous reproductive swarming in an estuary of the Omuta-gawa River in Ariake Sea, Japan. The
eggs of both species were isotonic to the medium of 27.5–30 psu salinity. The egg diameter in the isotonic salinity was 180–205 μm
in H. japonica, and 130–160 μm in H. diadroma. Successful development of most embryos was observed in a salinity range of 22.5–30 psu in both species, while successful
fertilization occurred in wider ranges of salinity, i.e., 10–34 psu in H. japonica and 10 to 30 psu in H. diadroma. In both species, free-swimming larval life started from the indistinct hatching of trochophores out of a jelly layer capsule.
The lecithotrophic development appeared to run to the 4-setiger nectochaetes in H. japonica, while to 3-setiger nectochaetes in H. diadroma, resulting in a shorter pelagic larval life in H. japonica. In a comparison of larval morphology among Hediste species, we found a definite negative correlation between the prostomium width, which represents the larval size and depends
on egg size, and relative length of chaetae to the prostomium width: the relative length of chaetae was the longest in H. diadroma (with the smallest egg size and long pelagic life), intermediate in H. japonica (intermediate egg size, short pelagic life), and the shortest in H. atoka (largest egg size, no true pelagic life). We also examined the possibility of hybridization between H. japonica and H. diadroma through cross-insemination experiments. The gametes of the two species were reciprocally compatible, and viable hybrid offspring
were produced by the laboratory crosses. The hybrid larvae expressed intermediate phenotypes, but with a greater maternal
influence in characteristics such as the relative length of chaetae and the lecithotrophic larval duration. 相似文献
7.
The pelagic copepod Calanus pacificus ranges nearly continuously across temperate-boreal regions of the North Pacific Ocean and is currently divided into three
subspecies—C. pacificus oceanicus, C. pacificus californicus, C. pacificus pacificus—based on subtle morphological differences and geographic location. The relation between geography and genetic differentiation
was examined for 398 C. pacificus individuals sampled from six widely distributed locations across the North Pacific, including an open ocean site and coastal
sites on both sides of the North Pacific basin. For each individual copepod, the DNA sequence was determined for a 421-bp
region of the mitochondrial coxI gene (mtCOI). A total of sixty-three different mtCOI sequences, or haplotypes, were detected,
with a sequence divergence between haplotypes of 0.2–3.1%. The number and distribution of haplotypes varied with sampling
location; 12 haplotypes were distributed across multiple sampling locations, and 51 occurred at only one location. Five genetically
distinct populations were detected based on F
ST values. Haplotype minimum spanning networks, nucleotide divergence and F
ST values indicated that individuals from coastal sites in the North Pacific Ocean were more closely related to each other than
to individuals from the open ocean site at Station P. These results provide genetic support for the designation of two subspecies—a
coastal subspecies that consists of what is currently referred to as C. p. pacificus and C. p. californicus and an open ocean subspecies C. p. oceanicus. This work also indicates that planktonic copepods with potentially high dispersal capacity can develop genetically structured
populations in the absence of obvious geographic barriers between proximate locales within an ocean basin. 相似文献
8.
This study provides information about differences in composition of ingested zooplankton amongst bivalve species coexisting
in the same area in a period from May 2009 to December 2010. The study was conducted at the Mali Ston Bay (42°51′ N, 17°40′
E)—the most important bivalve aquaculture area in the eastern Adriatic Sea. Stomach content analysis was performed on cultured
species—Ostrea edulis and Mytilus galloprovincialis, and commercially important bivalve species from their natural environment—Modiolus barbatus and Arca noae. Results confirmed carnivory in bivalves, both from natural and cultured populations, but cultured species had higher numbers
of zooplankters than those living on the seabed. The most abundant taxa were bivalve larvae, followed by tintinnids, copepods,
unidentified eggs and gastropod larvae. Recorded numbers of bivalve larvae in M. galloprovincialis stomach were the highest so far reported and show that mussels impact the availability of natural spat. 相似文献
9.
The molecular diversity of symbiotic dinoflagellates associated with the widespread western Pacific coral Plesiastrea versipora was explored in order to examine if associations between reef-building corals and symbiotic dinoflagellates change with environment. Several ribosomal DNA genes with different evolutionary rates were used, including the large subunit (28S), the 5.8S region and the internal transcribed spacers (ITS). The phylogenetic analysis of the 28S and 5.8S rDNA regions indicated that a single endosymbiont species, highly related to one of the species of Symbiodinium in clade C (= Symbiodinium goreaui, Trench et Blank), associates with P. versipora along the Ryukyu Archipelago. The persistence of the same endosymbiont within P. versipora across this wide array of latitudes may be a result of such features as the Kuroshio Current, which brings tropical temperatures as far north as Honshu, Japan. Analysis of the faster evolving ITS rDNA region revealed significant genetic variability within endosymbionts from different populations. This variation was due to a high degree of interpopulation variability, based on the proportion of pairwise variation detected among the populations (0.95% approximately). By comparison with other studies, the results also indicate that some ITS1 haplotypes from P. versipora endosymbionts seem to be widely distributed within the western Pacific Ocean, ranging from the Great Barrier Reef to the northeast of the China Sea. 相似文献
10.
Summary. The ontogeny of pyrrolizidine alkaloid (PA) synthesis
and constraints on defence level during the seedling stage were examined
in the annual Senecio vulgaris and the monocarpic perennial
Senecio jacobaea. In both species, PAs were actively
synthesized from the onset of seedling growth so that juvenile stages
did not go through an undefended stage. Roots are known to be the
exclusive sites where PAs are produced. Root biomass was the single most
important biomass parameter explaining variation in total PAs per
seedling. All correlation coefficients between—relative growth
rate and PA concentration were negative, but none was significant.
However, a significant negative—correlation was found between
shoot to root ratio and PA concentration in S. jacobaeaseedlings, suggesting a dilution effect of the PAs. Earlier studies have
shown that the shoot to root ratio is positively correlated with
relative growth—rate of established S. jacobaea plants.
It is therefore suggested that young S. jacobaea plants
with a high shoot to root ratio and hence a high growth capacity
necessarily have lower PA defence levels than plants with a low
shoot to root ratio.
Received 10 July 2002; accepted 16 November 2002. 相似文献
11.
For a facultative kleptoparasite, the decision to allocate time and energy to search for a prey or for a kleptoparasite opportunity could be influenced by its prior experience. In this study, we investigated the influence of experience on the proportion of the facultative kleptoparasitoid Eupelmus vuilleti females choosing an unparasitized host or a host parasitized by Dinarmus basalis. When exploiting hosts previously parasitized by D. basalis, a large proportion of E. vuilleti females reused the hole drilled by the D. basalis female, which led to a reduction in the time needed to reach the host. When submitted to successive choice tests between an unparasitized host and a host parasitized by D. basalis in a natural host-plant system, the proportion of E. vuilleti females which choose the parasitized host increased with the female experience. The same experiment carried out with an artificial host-plant system allowing an easy access to the host did not show a variation of the females’ choice with experience. A reward—here a faster access to the host through the hole drilled by the D. basalis female—seems necessary to mediate the associative learning expressed by the preferential choice of the parasitized host. 相似文献
12.
The zoanthid genus Isaurus (Anthozoa: Hexacorallia) is known from both the Indo-Pacific and Atlantic Oceans, but phylogenetic studies examining Isaurus using molecular markers have not yet been conducted. Here, two genes of markers [mitochondrial cytochrome oxidase subunit
I (COI) and mitochondrial 16S ribosomal DNA (mt 16S rDNA)] from Isaurus specimens collected from southern Japan (n = 19) and western Australia (n = 3) were sequenced in order to investigate the molecular phylogenetic position of Isaurus within the order Zoantharia and the family Zoanthidae. Additionally, obtained sequences and morphological data (polyp size,
mesentery numbers, mesogleal thickness) were utilized to examine Isaurus species diversity and morphological variation. By comparing our obtained sequences with the few previously acquired sequences
of genera Isaurus as well as with Zoanthus, Acrozoanthus (both family Zoanthidae), and Palythoa spp. (family Spenophidae) sequences, the phylogenetic position of Isaurus as sister to Zoanthus within the Family Zoanthidae was suggested. Based on genetic data, Isaurus is most closely related to the genus Zoanthus. Despite considerable morphological variation (in particular, polyp length, mesentery numbers, external coloration) between
collected Isaurus specimens, all specimens examined are apparently conspecific or very closely related based on molecular data and observed
morphological variation within colonies. Additionally, obtained internal transcribed spacer of ribosomal DNA (ITS-rDNA) sequences
from symbiotic zooxanthellae (Symbiodinium spp.) from all Isaurus specimens were shown to be subclade C1-related Symbiodinium.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
13.
Previous studies have shown that the three-spot damselfish species complex [ Dascyllus albisella Gill, D. auripinnis Randall and Randall, D. strasburgi Klausewitz, D. trimaculatus (Ruppell)] is an assemblage of five geographically distinct clades. The one exception was a single D. trimaculatus from French Polynesia, which grouped with "Pacific Rim" individuals. In the present study, an additional 252 individuals from French Polynesia collected between June 1996 and January 2002 were analyzed using PCR amplifications, restriction fragment length polymorphisms, and DNA sequencing of the mitochondrial control region. The French Polynesian D. trimaculatus belong to two distinct clades. One clade comprising 96% of the individuals includes haplotypes found only in French Polynesia. The other clade (4% of the individuals) is comprised of haplotypes that cluster with "Pacific Rim" individuals, a clade with widespread distribution from Japan to the Line Islands and from Wallis to Palau. Present data suggest that a small number of larvae from northwestern reefs (possibly Line Islands) may have occasionally reached and colonized French Polynesian reefs. 相似文献
14.
Dispersal in coral reef fishes occurs predominantly during the larval planktonic stage of their life cycle. With relatively
brief larval stages, damselfishes (Pomacentridae) are likely to exhibit limited dispersal. This study evaluates gene flow
at three spatial scales in one species of coral reef damselfish, Dascyllus trimaculatus. Samples were collected at seven locations at Moorea, Society Islands, French Polynesia. Phylogenetic relationships and gene
flow based on mitochondrial control region DNA sequences between these locations were evaluated (first spatial scale). Although
spatial structure was not found, molecular markers showed clear temporal structure, which may be because pulses of settling
larvae have distinct genetic composition. Moorea samples were then compared with individuals from a distant island (750 km),
Rangiroa, Tuamotu Archipelago, French Polynesia (second spatial scale). Post-recruitment events (selection) and gene flow
were probably responsible for the lack of structure observed between populations from Moorea and Rangiroa. Finally, samples
from six Indo-West Pacific locations, Zanzibar, Indonesia, Japan, Christmas Island, Hawaii, and French Polynesia were compared
(third spatial scale). Strong population structure was observed between Indo-West Pacific populations.
Received: 26 May 2000 / Accepted: 10 October 2000 相似文献
15.
Heterogeneity in the photoprotective capacity of three Antarctic diatoms during short-term changes in salinity and temperature 总被引:1,自引:0,他引:1
The Antarctic marine ecosystem changes seasonally, forming a temporal continuum of specialised niche habitats including open
ocean, sea ice and meltwater environments. The ability for phytoplankton to acclimate rapidly to the changed conditions of
these environments depends on the species’ physiology and photosynthetic plasticity and may ultimately determine their long-term
ecological niche adaptation. This study investigated the photophysiological plasticity and rapid acclimation response of three
Antarctic diatoms—Fragilariopsis cylindrus, Pseudo-nitzschia subcurvata and Chaetoceros sp.—to a selected range of temperatures and salinities representative of the sea ice, meltwater and pelagic habitats in the
Antarctic. Fragilariopsis cylindrus displayed physiological traits typical of adaptation to the sea ice environment. Equally, this species showed photosynthetic
plasticity, acclimating to the range of environmental conditions, explaining the prevalence of this species in all Antarctic
habitats. Pseudo-nitzschia subcurvata displayed a preference for the meltwater environment, but unlike F. cylindrus, photoprotective capacity was low and regulated via changes in PSII antenna size. Chaetoceros sp. had high plasticity in non-photochemical quenching, suggesting adaptation to variable light conditions experienced in
the wind-mixed pelagic environment. While only capturing short-term responses, this study highlights the diversity in photoprotective
capacity that exists amongst three dominant Antarctic diatom species and provides insight into links between ecological niche
adaptation and species’ distribution. 相似文献
16.
Gustavo Muniz Dias Luiz Francisco Lembo Duarte Vera Nisaka Solferini 《Marine Biology》2006,148(4):807-815
Pelagic larvae are highly important for maintaining the gene flow among populations of sessile marine invertebrates. Colonial
ascidians consist, exclusively, of brooding species, with lecithotrophic larvae that have a limited dispersal. As a result,
there is a marked differentiation among populations. In this work, we used allozyme electrophoresis to access the genetic
variation in four populations of Symplegma rubra, a colonial ascidian frequently found in the intertidal zone of Southeastern Brazilian coast. High variability was found
at three of the four sites sampled, the exception being Praia Grande in the State of Rio de Janeiro. At this site, there was
a great preponderance of clones, which possibly reflected the enclosed nature of the location and its low water circulation
that reduce the dispersal capabilities of these animals. S. rubra did not conform to expectations for random mating (Hardy–Weinberg equilibrium): there was a deficit of heterozygotes that
was more related to the small population size than to inbreeding processes, since F
is analysis per locus revealed a deficiency of heterozygotes at only one locus—MDH*. The greatest variation in allele frequency was found for GPI-2*. Analyses of genetic variability revealed moderate differentiation among the populations (F
ST=0.051), which was unexpected for a species with a low dispersal capability. Rafting, a frequently underestimated means of
dispersal, may be the main mode of gene flow in this species over large areas, since colonies of S. rubra are frequently seen growing on drift material and there is no evidence that the larva survive for a long time in the plankton. 相似文献
17.
Assuming that a male’s genetic characteristics affect those of his offspring, extra-pair copulation has been hypothesized
to increase heterozygosity of the progeny—the “genetic compatibility” hypothesis—and the genetic diversity within litters—the
“genetic diversity” hypothesis. We tested these two hypotheses in the alpine marmot (Marmota marmota), a socially monogamous mammal showing a high rate of extra-pair paternity (EPP). In a first step, we tested the assumption
that a male’s genetic characteristics (heterozygosity and genetic similarity to the female) affect those of his offspring.
Genetic similarity between parents influenced offspring heterozygosity, offspring genetic similarity to their mother, and
litter genetic diversity. The father’s heterozygosity also influenced litter genetic diversity but did not affect offspring
heterozygosity. Hence, heterozygosity seems not to be heritable in the alpine marmot. In a second step, we compared genetic
characteristics of extra-pair young (EPY) and within-pair young (WPY). EPY were less genetically similar to their mother but
not more heterozygous than WPY. EPY siblings were also less genetically similar than their WPY half siblings. Finally, the
presence of EPY promoted genetic diversity within the litter. Thus, our data support both the “genetic compatibility” and
the “genetic diversity” hypotheses. We discuss further investigations needed to determine the primary causes of EPP in this
species. 相似文献
18.
This paper explores the implications of ribosomal ITS1-sequence analysis for evolutionary relationships between four species of corallimorphs which are morphologically very similar but have distinct distributions. The analyses highlight the unreliability of morphological criteria in establishing systematic relationships amongst tropical corallimorphs. Both parsimony and distance methods of phylogenetic analysis strongly support a deep divergence between the Caribbean species Rhodactics sanctithoma and the three morphologically-related species R. howesii and R. indosinensis from the Indo-Pacific and R. rhodostoma from the Red Sea. The analyses also strongly support a closer relationship between the Red Sea species, R. rhodostoma, and one of the Indo-Pacific species, R. howesii, than between these two and the second Indo-Pacific species, R. indosinensis. The first of these results is presumably a consequence of the closure of the Central American Seaway, the event which led to the separate development of Atlantic and Indo-Pacific coral faunas. However, the lack of detailed distribution data represents a major barrier to reconstructing the evolutionary history of the genus. 相似文献
19.
The reproductive cycle of Geodia cydonium in a semi-enclosed Mediterranean bay (Porto Cesareo, SW Apulia) was studied with monthly frequency over a 3-year period.
The investigation was carried out by utilizing a technique consisting of tagging ten individuals with a PVC stick and cutting
off, by means of a metal cork borer, small samples (cylinders about 5 cm3 in volume) from each of them for histological analysis. Sexual reproductive elements were detected in all individuals, but
in the third year some specimens showed reduced reproductive activity or complete infertility. Spermatogenesis occurred in
a short period (from June to August) whereas oogenesis lasted longer (from spring to late summer). Spermatic cysts occurred
when the frequency of specimens with oocytes reached its maximum values. A relationship between water temperature and the
onset of gamete differentiation was observed. G. cydonium is here confirmed oviparous and gonochoric with a sex ratio in favour of the females. However, in contrast with current literature
on Porifera—which suggests that only a limited number of sponges, all belonging to the same species are sexually active—the
sexual reproduction of this species involves all the examined individuals. This finding can be explained by the methodological
approach used in this research, which differs from the traditional way of assessing the sponge reproductive cycle by analysing
randomly collected specimens within a population. The study of a series of individuals over time represents a better “model
technique” for investigating sponge sexual reproduction and the effect of environmental parameters on gamete differentiation. 相似文献
20.
Christopher L. Owen Charles G. Messing Greg W. Rouse Mahmood S. Shivji 《Marine Biology》2009,156(8):1517-1529
Phanogenia gracilis sensu lato is a shallow-water crinoid distributed throughout the Indo-western Pacific. The taxonomy of P. gracilis s.l. is clouded by the presence of two distinct morphotypes, each differing in morphology and ecology. The goal was to determine
the taxonomic status of P. gracilis s.l. using partial gene sequences of two mitochondrial DNA genes, cytochrome oxidase c subunit I and NADH dehydrogenase subunit
II, in conjunction with morphological and ecological data. The molecular phylogenies revealed three lineages separated by
5.0–6.6% corrected genetic distance, which is consistent with the genetic distances among other echinoderm species. Neither
morphotype was monophyletic, nor was any examined morphological character exclusive to any one lineage. Discriminant function
analysis (DFA) of the morphological and ecological data yielded significant results when grouping P. gracilis by morphotype and by clades recovered in the phylogenetic analyses, but grouping by sample locality was rejected. Although
DFA results of grouping by clade were significant, jackknife support was weak, while only correctly grouping specimens by
their respective clades 65% of the time. The results suggest the possibility of cryptic species, but additional molecular
and morphological data are needed to confirm this. This study demonstrates the need to reevaluate the taxonomy of crinoid
species and their respective diagnostic characters. 相似文献