Sclerite Size Research Articles

Morphological identification of the soft coral, Clavularia inflata, reveals different sclerite characters across Indonesian coral reefs

Soft corals of the genus Clavularia (Blainville 1830) have complex and difficult to distinguish morphological characteristics, making them rather difficult to identify. A paucity of information exists for Indonesian coral reefs, a complex biogeographic region at the confluence of the Pacific and Indian Ocean that covers an extensive geographic area and several marine ecoregions, is subject to several ocean current systems, and includes a high diversity of habitats. Specimens of Clavularia inflata were collected from eleven study sites across the Indonesian archipelago, morphologically described based on their sclerite characteristics, and compared among sites. Sclerite observations were divided into four parts for each colony, namely pinnules, crowns, calyces, and stolons. The sclerites found in C. inflata comprised various forms such as rods, fingers, sticks, and brackets. Morphometric measurements of C. inflata showed specimens from Kepulauan Seribu had the largest pinnule, calyx, and stolon sclerites compared to other locations. The maximum mean size of crown sclerites was observed for specimens from Maluku Tenggara Barat. Similarities in the shape of sclerites resulted in specimens from Kangean, Morotai, Tanjung Lesung, Bontang, Lombok and Natuna forming a cluster, while those from Maluku Tenggara Barat and Arborek were dissimilar to other sites. Smaller sclerite sizes in specimens from Arborek are likely related to strong currents at that site. In conclusion, there were variations in the size of sclerites across the eleven study sites, with several sites forming a cluster of similar sclerite dimensions. Further studies using molecular markers are suggested to further explore the possibility of cryptic species.

Morphology of male and female terminalia and taxonomic revision of the burrower bugs genus Canthophorus (Heteroptera: Cydnidae)

SummaryThe Palaearctic burrower bug genus Canthophorus Mulsant & Rey, 1866 (Heteroptera: Cydnidae) is revised. New data on the morphology and distribution are given. Structures of the female internal ectodermal terminalia and the completely inflated aedeagi in all species of the genus are described and illustrated for the first time. An extended differential diagnosis as a comparison with representatives of all Palearctic genera of the tribe Sehirini is given for the genus. Based on characters of the external morphology and terminalia of both sexes, new taxa are described: C. dubius sanigarum n. ssp., C. melanopterus mariae n. ssp., C. impressus hajastanicus n. ssp., and C. wagneri hyrcanicus n. ssp.; C. hissaricus Asanova, 1964 is downgraded to a subspecies level and included in C. mixtus Asanova, 1964. C. melanopterus niger (Vidal, 1950) is placed in synonymy with C. melanopterus melanopterus (Herrich-Schaeffer, 1835). A wide variability of the terminalia, especially in females, was found in C. melanopterus melanopterus; in the latter, six forms are described differing in the shape and size of sclerites in posterior pouches of the gynatrial sac and distributed mainly in the Mediterranean region. A key allowing identification of the species not only by males, but also by females, was compiled for the first time. It is shown that C. aeneus (Walker, 1867) [= Sehirus fuscipennis Horváth, 1899] and C. maculipes (Mulsant & Rey, 1852) have very significant differences from other species of Canthophorus in the male and female terminalia, and at the same time share some characters with the genus Adomerus Mulsant & Rey, 1866, including unique characters shared with several species of this group; therefore, the mentioned two species are transferred to the genus Adomerus.

Morphological features of the gorgonian Paramuricea macrospina on the continental shelf and shelf edge (Menorca Channel, Western Mediterranean Sea)

ABSTRACTMorphological variability in gorgonians is frequent and commonly associated with habitat variability, often resulting in segregated morphotypes. Paramuricea macrospina is an endemic Mediterranean gorgonian species found on rocky bottoms between 40 and 160 m depth and has recently been reported as one of the most abundant species in continental shelf and shelf edge environments. Three different chromatic forms of P. macrospina were observed in the Menorca Channel: a yellow form and a light purple form occurring on maërl beds of the continental shelf, and a dark purple form occurring on rocky substrates of the shelf edge. The objective of the present work is to verify if these P. macrospina forms may represent distinct taxonomic units by analysing differences in colony morphology and sclerite size and shape of the three chromatic forms. No significant differences were found in colony shape, suggesting that environmental variability between the continental shelf and the shelf edge is not influential enough to significantly alter colony morphology. Significant differences in sclerite size and shape were found amongst all forms, suggesting that sclerites may be influenced by environmental conditions. However, the co-occurrence of the yellow and light purple forms side by side on the continental shelf may indicate a certain degree of genetic differentiation.

Cambrian palaeoscolecids (Cycloneuralia) of southern Scandinavia

AbstractA previously undocumented diversity of Cambrian palaeoscolecids is described from localities in Sweden, Norway and Denmark. The material described here includes isolated sclerites as well as the first macroscopic specimens reported from the palaeocontinent Baltica. The sclerites are all of early middle Cambrian age (Ptychagnostus gibbus Biozone) and are assigned to at least four new species of Hadimopanella, two of which are formally introduced: H. incubo sp. nov. and H. oelandiana sp. nov. The two macroscopic specimens are of late early Cambrian (Ellipsocephalus lunatus Biozone) and early middle Cambrian age (Acadoparadoxides oelandicus Biozone), respectively. The early Cambrian specimen is described as Maotianshania? sp. and comprises an incomplete annulated trunk fragment which is uniformly covered with circular sclerites, indicative of the palaeoscolecid family Maotianshaniidae. This is the first record of this family outside China. The middle Cambrian specimen is almost complete and introduced as Wronascolex? johanssoni sp. nov. It is characterized by a previously undocumented distribution of its Hadimopanella‐like sclerites which increase in size and change ornamentation from the anterior to the posterior end of the distinctly annulated trunk. The observed distribution pattern can explain the high variability of species of the sclerite‐based genus Hadimopanella as well as the occurrence of rare morphotypes of Hadimopanella in otherwise rich samples. Available data on the ontogeny of palaeoscolecids regarding the relationship between body and sclerite size of a taxon are evaluated. It is concluded that sclerite size might be species specific and should be considered when comparing taxa with morphological similar sclerites.

Limited Genetic Connectivity between Gorgonian Morphotypes along a Depth Gradient.

Gorgonian species show a high morphological variability in relation to the environment in which they live. In coastal areas, parameters such as temperature, light, currents, and food availability vary significantly with depth, potentially affecting morphology of the colonies and the structure of the populations, as well as their connectivity patterns. In tropical seas, the existence of connectivity between shallow and deep populations supported the hypothesis that the deep coral reefs could potentially act as (reproductive) refugia fostering re-colonization of shallow areas after mortality events. Moreover, this hypothesis is not so clear accepted in temperate seas. Eunicella singularis is one of the most common gorgonian species in Northwestern Mediterranean Sea, playing an important role as ecosystem engineer by providing biomass and complexity to the coralligenous habitats. It has a wide bathymetric distribution ranging from about 10 m to 100 m. Two depth-related morphotypes have been identified, differing in colony morphology, sclerite size and shape, and occurrence of symbiotic algae, but not in mitochondrial DNA haplotypes. In the present study the genetic structure of E. singularis populations along a horizontal and bathymetric gradient was assessed using microsatellites and ITS1 sequences. Restricted gene flow was found at 30–40 m depth between the two Eunicella morphotypes. Conversely, no genetic structuring has been found among shallow water populations within a spatial scale of ten kilometers. The break in gene flow between shallow and deep populations contributes to explain the morphological variability observed at different depths. Moreover, the limited vertical connectivity hinted that the refugia hypothesis does not apply to E. singularis. Re-colonization of shallow water populations, occasionally affected by mass mortality events, should then be mainly fueled by larvae from other shallow water populations.

A new species of Ovabunda (Octocorallia, Xeniidae) from the Andaman Sea, Thailand with notes on the biogeography of this genus.

A survey of xeniid octocorals was carried out in the waters off Southwestern Thailand in September, 2007. Microscopic investigation of the colonies revealed that three specimens belonged to the genus Ovabunda. Gross morphological examination is presented here accompanied by scanning electron micrographs of the sclerites. Molecular phylogenetic analysis showed identical genotypes at mtMutS, COI, and 28S rDNA for all three specimens and supports their generic assignment. Colony size and shape, sclerite size, and pinnule arrangement differ from nominal species of Ovabunda and thus a new species, O. andamanensis is introduced here. This work also presents a new eastern geographical record for the genus Ovabunda.

Quantifying Complex Shapes: Elliptical Fourier Analysis of Octocoral Sclerites

Species descriptions of most alcyonacean octocorals rely heavily on the morphology of sclerites, the calcium carbonate spicules embedded in the soft tissue. Sclerites provide taxonomic characters for species delineation but require qualitative descriptions, which introduce ambiguities in recognizing morphological features. Elliptical Fourier analysis of the outline of sclerites was used to quantify the morphology of eight species of gorgoniid octocoral in the genus Pseudopterogorgia. Sclerites from one to seven colonies of each species were compared. Scaphoids and spindles were examined separately; rods and octoradiates were excluded from the analyses because of their morphologic similarity across all species. Discriminant analysis of elliptical Fourier descriptors (EFDs) was used to determine whether the elliptical Fourier analysis could be used to identify the specimens. Sclerites were highly variable even within a single colony. Correct species assignments of individual sclerites were greater than 50% for both scaphoids and spindles. Species assignments based on averages of the EFDs for each colony approached 90%. Elliptical Fourier analysis quantifies morphological differences between species and measures colony variance in sclerite size and shape among colonies and species. Phylogenetic analysis based on EFDs did not capture monophyletic groups. The quantification of complex shapes such as sclerites provides an important tool in alpha taxonomy but may be less useful in phylogenetic analyses.

The use of geometric morphometrics in understanding shape variability of sclerotized haptoral structures of monogeneans (Platyhelminthes ) with insights into biogeographic variability

The sclerotized attachment organ of monogeneans has been widely used to address fundamental questions in ecology and evolution. However, traditional morphometric techniques appear to be partially inadequate and non-optimal. Traditional linear measurements mainly provide information on the size of sclerites but provide very little information, if any, on their shape. The shape of sclerites is indeed virtually unexplored and its implication for ecological and evolutionary processes remains to be analyzed. This study aims to both introduce and illustrate the use of geometric morphometrics in order to study sclerites of monogeneans in a biogeographic context. To do this, we investigated morphological variation patterns among four populations from the Pacific Ocean and six monogenean species through traditional and geometric morphometric techniques. Unlike the traditional method, the geometric morphometric method yielded a high percentage of individuals correctly classified to the four populations, providing strong evidence for phenotypic variability, divergence and local adaptation among islands without evolutionary constraint. Moreover, the traditional method also resulted in inconsistent interpretations of shape variations. This study highlighted the limitations that may arise when using traditional morphometric techniques and emphasizes that considerable information about the shape of sclerotized haptoral parts is added by using geometric morphometrics. Given the prominent taxonomic, ecological and evolutionary role of the haptor for characterizing monogeneans, we ultimately discuss the potential broad use of geometric morphometrics in a wide variety of ecological and evolutionary contexts. This powerful approach might allow a more robust estimation of the extent to which traditional evolutionary theories based on size of sclerites are congruent with their shape.

Light-Enhanced Calcification and Dark Decalcification in Isolates of the Soft CoralCladiellasp. During Tissue Recovery

Light-enhanced calcification is a general characteristic of zooxanthellate corals, suggesting a link between calcification by the coral and photosynthesis by the zooxanthellae, but the relationship between zooxanthellae and coral hosts during this process has not been elucidated. We hypothesized that the effects of tissue injury on the coral fragments used in experiments studying calcification might obscure that link. To detect the effects of tissue injury on light-enhanced calcification, we measured calcification rates (sclerite formation) in the soft coral Cladiella sp. by the alkalinity anomaly method during a 36-day experiment following injury associated with coral fragmentation. In the 2 weeks after colony fragmentation, the calcification response did not show a relation with light intensity. The typical light-enhanced calcification pattern was not noticed until day 15 of tissue recovery. The calcification rate of this soft coral increased with light intensity and time of tissue recovery and was comparable to that of hard corals exposed to similar experimental conditions. However, Cladiella sp. decalcified in the dark. The diurnal calcification-decalcification cycles probably control sclerite size and shape.

A new genus of viviparous gyrodactylid (Monogenea) from the Great Barrier Reef, Australia with descriptions of seven new species

Acanthoplacatus gen. nov., a new genus of viviparous gyrodactylid, is described from the fins and skin of siganid fishes from the Great Barrier Reef, Australia. The genus is characterized by a muscular, tube-like haptor with 16 marginal hooks on the posterior margin. The ventral lobe of the haptor is located anteriorly relative to the dorsal lobe and contains a pair of hamuli and a ventral bar with posteriorly-projecting ventral bar membrane. A dorsal bar is absent. Five pairs of posterior gland cells surround the posterior terminations of the gut. The male copulatory organ is a muscular, non-eversible bulb with several spines around the distal opening. Species of Acanthoplacatus have a bilateral excretory system consisting of six pairs of flame cells and a pair of excretory bladders. Seven new species are described: Acanthoplacatus adlardi sp. nov. and A. amplihamus sp. nov. from Siganus punctatus (Forster, 1801), A. brauni sp. nov. from S. corallinus (Valenciennes, 1835), A. parvihamus sp. nov. from S. vulpinus (Schlegel and Mueller, 1845), A. puelli sp. nov. from S. puellus Schlegel, 1852, A. shieldsi sp. nov. from S. lineatus (Valenciennes, 1835) and A. sigani sp. nov. from S. fuscescens (Houttuyn, 1782). Species can be discriminated by shape and size of the hamuli, marginal hooks and ventral bar and by male copulatory organ sclerite morphology. Three species (A. brauni sp. nov., A. shieldsi sp. nov. and A. sigani sp. nov.) were assessed for seasonal variation of sclerite size. Ten of thirteen morphological characters showed seasonal variation in size for at least one of the species. The characters were longer in winter except dorsal root tissue cap width. Only one character, marginal hook length, showed significant seasonal variation for all three species. Species of Acanthoplacatus were observed to attach using only the marginal hooks and the role of hamuli in attachment is unclear. The dorsal fin of the host is the preferred site for most species but the anal fin, caudal fin and body surfaces are preferred by some species. Prevalences for species range from 57 to 100%.

Different populations of Scomber australasicus in New Zealand and south‐eastern Australia, demonstrated by a simple method using monogenean sclerites

A simple method for distinguishing fish populations using monogenean sclerites is described. Monogeneans are left in a drop of 45% acetic acid on a microscope slide for a few minutes, and squashed under a cover slip to spread the hamuli and genital hooks in one plane. Hamuli and hooks are then measured with the aid of measuring eyepieces. Measurements of sclerites of Kuhnia and Pseudokuhnia fixed directly in 10% formalin or fixed in 10% formalin after freezing for several days gave the same results. Prerequisites for the use of the method are that monogeneans occur in sufficient numbers and show distinct geographical variation. The method is easiest to use if the size of sclerites does not change with body growth. Kuhnia scombri (Monogenea: Polyopisthocotylea) from the mackerel, Scomber australasicus, in New Zealand and New South Wales differ significantly in the length of the hamuli; it is concluded that there may be different populations of mackerel at the two localities. There also are different populations of Scomber japonicus in Japan and Ecuador, and sympatric populations of S. japonicus and S. australasicus in Japan harbour identical populations of the monogeneans Pseudokuhnia minor and Kuhnia sprostonae.