Charles Messing's Crinoid Pages: Resources

Citations and abstracts for literature on aquatic science resources including aquatic science, aquatic organisms, fisheries, and oceanography. Covers serials, books, reports, conference proceedings, and limited distribution literature. Includes 5 subfiles which can be searched individually or in combination.

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Seasonal variations were examined in the biochemical and energetic composition of two bathyal stalked crinoids, Neocrinus decorus and Endoxocrinus parrae (Isocrinidae). Three individuals of each species were collected in May, August and November, 1993, and April, 1994 (SW of Little Bahama Bank in 400-430 m), then frozen, lyophilized, and separated into crown, stalk and cirri. Three subsamples of each body part were burned at 500°C for 4h to determine % ash. Soluble protein and carbohydrate were determined colorimetrically. Lipid was measured gravimetrically. Insoluble protein was calculated by subtraction. All biochemical data are given in % dry weights. Ash constitutes the greatest percent of all body parts and comprises similar proportions of stalks and cirri of both species (87-91 %). However, the N. decorus crown contains significantly less ash (68-73%) than that of E. parrae (80-82%). Protein is the major organic component in all body parts. Soluble protein ranges are 9-1S% in crowns, 1-3% stalks, and 0.5-2% in cirri of both species. While insoluble protein content is also similar in the stalk and cirri of both species, the N. decorus crown always contains a greater proportion (7-16%) than that of E. parrae (3-7%). Lipids and carbohydrates show similar trends at lower levels. Changes observed in organic constituents for both species suggest: 1) short-term nutrient storage, 2) reproductive activity, although no ripe individuals were observed, and/or 3) seasonally higher food quality.

Total protein contributes the most to the energetic content of both species. Lipids contribute about the same energetic content to stalks and cirri of both species, but higher amounts to the crown of N. decorus. Mean total energetic content excluding ash of E. parrae is 1.7x that of N. decorus (21.7 vs. 12.9kJ) due to the former's larger crown. Both species invest >80% of their energy in the crown, reflecting its importance to reproduction, feeding and nutrient storage. Stalk and cirri are support structures that apparently require relatively small amounts of energy. Both species occur in locally high densities and may provide a substantial amount of energy to the biotic community. It remains unknown, however, what biota utilize this energy.

Gut contents were sampled from five specimens of each species in February, August, and October, 1991 and April, 1992 and the type and size of food items determined. Gut contents were quantified by determining area occupied by food items in a Neubauer counting chamber. Food composition is similar within and between species and does not vary with sampling month. Detritus is the major component (50-60%) by gut content area. Copepods, other crustacean parts and radiolarians together contribute 10-30%. Foraminifera, tintinnid ciliates, sponge spicules, ostracods, fecal pellets, diatoms, pollen grains and dinoflagellates each contribute 2% at most. Copepods are the main identifiable food item by area (40-60%) excluding detritus. Radiolarians are the most abundant food items (50-60%) by particle count (excluding detritus).

Mean size of ingested particles is ≤200μm (excluding detritus) with no significant differences between crinoid species. Ostracods are the largest identifiable particles and measure up to about 800J.lm wide, considerably larger than the ambulacral groove width of either species. The lack of significant differences in either size or composition of gut contents between species suggests that they do not partition food resources.

Several genera in the comatulid family Mariametridae are currently ambiguously distinguished on the basis of variations in length and robustness of oral pinnules. Previous descriptions have suggested that at least the genera Stephanometra and Lamprometra are imperfectly distinguishable. A detailed re-examination of morphology coupled with principal component analyses of morphometric data and cladistic analyses provide support for a monophyletic Stephanometra distinct from Lamprometra. A preliminary morphological analysis suggests that Dichrometra and Liparometra should be synonymized with Lamprometra. The six currently recognized species of Stephanometra uniquely share at least one pair of oral pinnules characterized by enlarged size, reduced ambulacral groove and flat, almost featureless articular facets that together produce a large, stiff, spinelike pinnule. Additional features distinguishing Lamprometra from Stephanometra include oral pinnular proportions, distribution of cirri and the nature of the adambulacral margin along the brachitaxes and arm bases.

Within Stephanometra, two groups of species are currently recognized. Those of the first group, S. echinus and S. tenuipinna, have long sharp aboral spines on distal cirrals and a spinelike fIrst pinnule. Those in the second group, S. spinipinna, S. indica, S. spicata and S. oxyacantha, lack aboral cirral spines and are differentiated by oral pinnule features. The latter three have a slender, flexible first pinnule and are distinguished by the number of enlarged spinelike pinnules that follow. In S. spinipinna, the first pinnule is also spinelike. Twenty percent of the specimens examined in the indica-spicata-oxyacantha series are intermediates that cannot be satisfactorily assigned to species based on current diagnoses. Cladistic analyses suggest that these three form a continuum and should be synonymized (under S. indica), that S. spinipinna should be assigued to S. indica, and that S. echinus and S. tenuipinna are synonymous (with S. tenuipinna the senior name). Likewise principal component analysis illustrates distinct groupings for these two species.

The crinoid family Comasteridae has undergone several revisions based on morphological characters. None, however, have employed DNA sequence data to generate a phylogenetic hypothesis for the group. To elucidate both monophyletic clades and generic interrelationships, DNA was obtained from 32 taxa, and 655 aligned base positions from near the 3' terminus of the mitochondrial 16S rDNA gene were sequenced. The results of analyses by maximum parsimony, neighbor-joining, and maximum likelihood methods support the majority of the current morphologically defined generic designations, though one genus emerges as paraphyletic and another as polyphyletic. Intergeneric relationships are less clear though strong support of several sister-clade relationships is evident including Comatella/Alloeocomatelia and Comanthus (in part)/Clarkcomanthus. Subfamilial designations are moderately to strongly supported in the Comanthinae but weakly supported elsewhere.

This initial assessment of phylogenetic relationships within the family poses a number of additional questions and directions for future research. It will serve as the launching point for future systematic research both within the family Comasteridae and for comatulid crinoids in general.

Crinoid taxonomy has been plagued with morphological variability as a result of intraspecific phenotypic plasticity. In an effort to test the validity of these overlapping morphological characters, we compared new mtDNA phylogenies and morphological matrices of two separate comatulid species complexes to the current alpha taxonomy. In the genus Comaster Agassiz, 1836 we examined partial mitochondrial (mtDNA) gene sequences (COI and ND2) of Comaster audax (Rowe et al., 1986), Comaster nobilis (Carpenter, 1884), and Comaster schlegelii (Carpenter, 1881), while in the genus Phanogenia Loven, 1866 we examined the two morphotypes of Phanogenia gracilis (Hartlaub, 1893). The morphological data analysis of overlapping characters revealed no trends in both species complexes, thus conflicting with current morphological species designation. Although, Comaster audax can be distinguished by its tuberculate brachitaxes and arm bases, spinous swollen axillaries and proximal brachial ossicles. The mtDNA phylogenies also conflict with current morphological species designation. Comaster nobilis and Comaster schlegelii are conspecific, while Comaster audax is paraphyletic with respect to the C. nobilis/schlegelii clade, which may explain the partitioning of some limited morphological variation to particular ocean basins. The P. gracilis morphotypes are conspecific with no geographic partitioning. However, population genetic analyses reveal genetic breaks between the Pacific Ocean and the Indian Ocean in the C. nobilis/schlegelii clade, which may explain the partitioning of morphotypes to particular ocean basins. The conflicting morphological and molecular data sets confirm that the morphological characters need to be reevaluated.

The morphology of members of the isocrinid genus, Endoxocrinus, found by A.H. Clark, 1908, in the Bahamas was examined to see if current classification schemes are valid. Individuals included in this survey belonged to the current species Endoxocrinus prionodes, Endoxocrinus carolinae, and Endoxocrinus parrae. Additionally, individuals of two depth-related morphotypes of E. parrae were examined. Evidence is presented that suggests that E. carolinae should be included in E. parrae, while the validity of E. prionodes is maintained. No evidence was found to warrant the recognition of the two depth-related morphotypes as distinct. Rather, these forms, as well as traditional E. parrae and E. carolinae, encompassed a high degree of variability along a morphological continuum. The study concludes that a revision of the genus should be considered and that isocrinid species can be much more variable in morphology than was previously recognized.

Superfamily Himerometroidea AH Clark, 1908 (Echinodermata: Crinoidea) (formerly Mariametroidea) is the second most speciose superfamily in order Comatulida. Although it includes some of the most common species on tropical western Pacific reefs, its phylogeny is poorly understood. Genus- to species-level taxa are currently distinguished by plastic morphological characters. We revised the superfamily from species- to family-levels using a combined morphological and molecular approach. A phylogeny using two nuclear and three mitochondrial markers recovered Colobometridae and Himerometridae as paraphyletic and Mariametridae and Zygometridae as polyphyletic. Within genus Himerometra (Himerometridae), sequence data and detailed morphological examinations of multiple specimens of H. magnipinna, H. martensi and H. robustipinna indicated that these three taxa are conspecific. A similar examination of specimens attributed on morphological grounds to the genera Dichrometra, Liparometra and Lamprometra (Mariametridae) revealed a lack of substantial enough sequence and morphological differences to maintain them as distinct genera. We have synonymized all three genera and redescribed four species under the senior name Dichrometra. Additional work is needed to more clearly establish characters that will diagnose clades across the superfamily. This study illustrates the importance of reevaluating classifications that incorporate ecophenotypically and ontogenetically variable characters.

Feather star (Echinodermata: Crinoidea: Comatulida) family Charitometridae has not been revised since 1950. Molecular analysis, new specimens of existing species, and the discovery of a new species has revealed the need for a generic-level revision of those genera that exhibit abruptly expanded genital pinnules. A morphological study was conducted using 57 specimens representing 10 species of the Charitometridae. The genus Poecilometra is redescribed, and two species formerly placed in Strotometra have been moved to the genus based primarily on possession of pedunculate genital pinnules and a wide flange on the first pinnular of the proximal pinnules. A new species was described: Poecilometra tibicinem n. sp. The genus Strotometra is redescribed based on its cirri and laterally expanded genital pinnulars and its extant two species synonymized under Strotometra parvipinna. An undescribed stereomic structure was discovered on the proximal brachial articulations in the medial angles of the muscular fossae in some specimens, but its taxonomic significance remains unresolved.

Antedonidae (Crinoidea: Comatulida) is the largest of extant crinoid families; it currently includes ~155 accepted species in 50 genera and accounts for ~23% of extant crinoid species (~29% of feather stars) and 27% of genera. Molecular phylogenies have returned the family as polyphyletic, with several clades scattered among non-antedonid sister groups (Hemery 2011, Hemery et al. 2013, Rouse et al. in prep.). Traditional morphological characteristics are thus inadequate for reconstructing relationships among taxa. SEM imaging was used in an effort to discover new diagnostic features that will support the molecular data, focusing on skeletal ossicles within the calyx, specifically the radial ossicles, as they are least likely to be affected by their hydrodynamic environment. Geometric morphometric analysis and landmark software were used to systematically compare equivalent skeletal parts among antedonid and non-antedonid sister taxa to identify likely homologies and homoplasies. Principal Component Analysis (PCA/BGPCA) and Procrustes ANOVAs were used for visualizing and testing variances within and between taxonomic and molecular groups. Linear Discriminant Analysis (LDA) was used with leave-one-out cross validation (LOOCV) to identify any misclassifications based on morphological similarities. UPGMA Hierarchical clustering models using both Procrustes and Mahalanobis distances were produced for comparison, and inter-landmark measurements were compared between species in search for possible intra-radial character states. Results yielded significant variation of radial morphology within the family Antedonidae with significant effects by depth range, taxonomic classification, and phylogenetic forces. All species with a radial height to width (H:W) ratio <1.0 were restricted to the shallower depths (0-200m) and notable morphological similarities were seen within both molecular clades and taxonomic subfamilies (Antedoninae and Thysanometrinae excepted). Regional affects were seen within the subfamily Antedoninae, as the Atlantic antedonines differed significantly from the Pacific antedonines, both in overall radial appearance and in H:W ratio. These results, with limited variation within molecular clades, give at least rudimentary support to recent molecular phylogenetics and promote further morphological studies of this nature that will strengthen our understanding of extant crinoid phylogeny (Bull et al. 1993, Littlewood et al. 1997, Hemery 2011, Rouse et al. 2013, Roux et al. 2013).

Adults of Comatilia iridometriformis, A. H. Clark, 1909, a deep-water feather star, retain the following attributes limited chiefly to juveniles of other species in its family, the Comasteridae: small size (maximum arm length about 30 mm), large radial ossicles, incomplete pinnulation, slender cirral ossicles and coarse stereom. This is the only known instance of paedomorphosis (retention of juvenile characters in the adult) among extant crinoids. Observations from the submersible “Alvin” in about 580 m indicate that C. iridometriformis lives associated with ahermatypic, bankforming corals (Lophelia prolifera and Enallopsammia profunda). The crinoids cling to dead coral and other solid substrates, but not to living coral. The crinoids appear to prefer slow, locally variable and multidirectional water movements. Although some other crinoids brood early developmental stages externally or within brood pouches, C. iridometriformis is the only crinoid that appears to brood giant embryos and larvae within the ovarian lumen (although poor histological fixation left some doubt about the exact location). Larvae approaching the cystidean stage were the most advanced brooded forms observed; release from the ovary probably occurs at about this stage. Stalked pentacrinoid larvae are sometimes found on the cirri of the adult crinoids. C. iridometriformis is also peculiar in being the only brooding member of the family Comasteridae and the only internally brooding feather star not found in middle or high southern latitudes. It is suggested that: paedomorphosis in this feather star results from accelerated sexual maturation (progenesis), the potentially unstable habitat may contribute to selection for rapid growth; and neither food nor space may be limiting. Moreover, brooding may be both a design constraint (due to small size) and a way to prevent loss of progeny from a discontinuous habitat where current flow tends to be unidirectional.

This study was carried out in 1979 on material collected chiefly in the northern Straits of Florida.

Methanol/dichloromethane extracts of (1) the arms and pinnules, and (2) the stalk and cirri of the deep water stalked crinoids Endoxocrinus parrae (Gervais) and Neocrinus decorus (Carpenter) were imbedded at ecologically relevant volumetric concentrations in alginate food pellets containing 2% krill as a feeding stimulant and presented in situ to an assemblage of shallow-water reef fish. Experimental pellets were highly palatable to reef fish; no significant differences in pellet consumption occurred between experimental pellets containing extracts from either species of stalked crinoid or control pellets. Small pieces of cirri, stalks, calyx, arms and pinnules of both species were also tested in in situ feeding assays. While immediate consumption by fish was not apparent, Blue Headed Wrasse (Thalassoma bifasciatum (Block)) and Dusky Damselfish (Stegastes fuscus (Cuvier)) bit at pieces of each body component. Similar fish biting behaviors were also observed when two living Endoxocrinus parrae were deployed on the shallow reef. Observations indicate that neither species of stalked crinoid is chemically defended from predation by a natural assemblage of reef fish. This supports the predation hypothesis that restriction of stalked crinoids in deep-water habitats may have resulted from the Mesozoic radiation of durophagous fishes in shallow seas, resulting in a reduction of stalked crinoids from shallow water.

A recent preliminary survey revealed that 12 species of unstalked crinoids occur on a gentle sandy slope (12–18 m depth) at Lizard Island, Great Barrier Reef, Australia; five of which are also found on coral reefs. The other seven appear to constitute a unique assemblage restricted to unconsolidated substrates, where most cling to algae or hide beneath rubble or sponges. Members of this assemblage exhibit all of the basic feeding postures found among reef-dwelling species. However,Comatula rotalaria, which lacks anchoring cirri and bears uniquely differentiated short and long arms, exhibits a posture different from other living crinoids. Quantitative transects reveal apparent depth-related differences in species composition: C. rotalaria dominated the 12 transects in 12–13 m (84% of 82 specimens), while Comatella nigra, Comatula cf. purpurea, Amphimetra cf. tessellata and Zygometra microdiscus accounted for 96% of 54 specimens observed along 12 transects in 16–17 m.

Deep-sea submersible observations made in the Bahamas revealed interactions between the stalked crinoid Endoxocrinus parrae and the cidaroid sea urchin Calocidaris micans. The in situ observations include occurrence of cidaroids within “meadows” of sea lilies, close proximity of cidaroids to several upended isocrinids, a cidaroid perched over the distal end of the stalk of an upended isocrinid, and disarticulated crinoid cirri and columnals directly underneath a specimen of C. micans. Guts of two C. micans collected from the crinoid meadow contain up to 70% crinoid material. Two of three large museum specimens of another cidaroid species, Histocidaris nuttingi, contain 14–99% crinoid material.

A comparison of cidaroid gut contents with local sediment revealed significant differences: sediment-derived material consists of single crinoid ossicles often abraded and lacking soft tissue, whereas crinoid columnals, cirrals, brachials, and pinnulars found in the cidaroids are often articulated, linked by soft tissue, and unabraded. Furthermore, articulated, multi-element fragments often show a mode of fracture characteristic of fresh crinoid material. Taken together, these data suggest that cidaroids prey on live isocrinids.

We argue that isocrinid stalk-shedding, whose purpose has remained a puzzle, and the recently documented rapid crawling of isocrinids are used in escaping benthic predators: isocrinids sacrifice and shed the distal stalk portion when attacked by cidaroids and crawl away, reducing the chance of a subsequent encounter. If such predation occurred throughout the Mesozoic and Cenozoic (possibly since the mid-Paleozoic), several evolutionary trends among crinoids might represent strategies to escape predation by slow-moving benthic predators.

It has been argued that increases in predation over geological time should result in increases in defensive adaptations in prey taxa. Recent in situ and laboratory observations indicate that cidaroid sea urchins feed on live stalked crinoids, leaving distinct bite marks on their skeletal elements. Similar bite marks on fossil crinoids from Poland strongly suggest that these animals have been subject to echinoid predation since the Triassic. Following their near-demise during the end-Permian extinction, crinoids underwent a major evolutionary radiation during the Middle–Late Triassic that produced distinct morphological and behavioral novelties, particularly motile taxa that contrasted strongly with the predominantly sessile Paleozoic crinoid faunas. We suggest that the appearance and subsequent evolutionary success of motile crinoids were related to benthic predation by post-Paleozoic echinoids with their stronger and more active feeding apparatus and that, in the case of crinoids, the predation-driven Mesozoic marine revolution started earlier than in other groups, perhaps soon after the end-Permian extinction.