Contributions to the taxonomy of Sabellidae (Polychaeta)

The genus Potamilla Malmgren is particularly characterized by dorsal lips which lack any radiolar midrib; Pseudopotamilla Bush by compound radiolar eyes, dorsal collar lappets and flanges alongside the bases of the most dorsal radioles; Demonax Kinberg by a wide dorsal collar gap and companion setae with big heads and narrow blades; and Potamethus Chamberlin by an elongated first segment, enlarged ventral sacs, very long shafts to the thoracic uncini, and inferior abdominal setae much shorter than the superior ones. Perkinsiana gen. nov . lacks most of these characters, but the type species 'Potamilla' rubra Langerhans is remarkable in having red blood. It bores into limestone abundantly off S Wales and is here redescribed. Oriopsis hynensis sp. nov . from SW Ireland has a smooth collar set low on the first segment, with its ventral margin entire and free from the apex of the peristome. The new name Demonax langerhansi is proposed for Sabella (Potamilla) incerta Langerhans non Demonax incertus Kinberg.     

The genera <Emphasis Type="Italic">Bispira</Emphasis> Krøyer, 1856 and <Emphasis Type="Italic">Stylomma</Emphasis> Knight-Jones, 1997 (Polychaeta,Sabellidae): systematic revision,relationships with close related taxa and new species from Australia

A cladistic analysis undertaken to test monophyly of Bispira and Stylomma (including new species of both genera) and to ascertain relationships with related taxa reveals that Bispira is paraphyletic without the inclusion of Pseudobranchiomma and Branchiomma, and that Stylomma is monophyletic due to the presence of a structure on the dorsal basal flanges which has never been described before. New species of Bispira and Stylomma from Australia are described. Bispira serrata n. sp., differs from the other species of the genus in having serrated radiolar flanges whereas all other Bispira species have smooth flanges or lack them, and also by the shape of the thoracic and abdominal uncini, which are short-handled and have 2–3 rows of big teeth above the main fang, instead of having medium-sized handles and small, numerous rows of teeth over the main fang. Stylomma juani n. sp., is characterized by the presence of serrated radiolar flanges and unpaired compound eyes along the branchial radioles, whereas other species in the genus have smooth radiolar flanges and subterminal compound radiolar eyes. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Handling editor: K. Martens     

Ontogenetic variations in characters of Euchone analis (Krøyer, 1856) (Polychaeta, Sabellidae, Sabellinae) from Spitsbergen, and new assignments of Oriopsis ingelorae Plate, 1995 and O. liefdefjordensis Plate, 1995

Euchone analis, the type species of its genus, was collected in high densities and in different size classes from Kongsfjorden, west Spitsbergen. This material has provided the basis for an investigation of the size dependence of characters. Almost all characters used in diagnoses were highly variable, especially the number of abdominal chaetigers forming the anal depression and the shape of the depression. The only relatively constant features are the number of chaetigers anterior to the anal depression and the branchial crown‐to‐body length ratio. A branchial skeleton extension of the radiolar appendages of the dorsal lips was found for the first time within Euchone, and this character has been added to the diagnosis of Euchone. Oriopsis liefdefjordensis and small specimens of E. analis agree in all characters, and O. liefdefjordensis is proposed to be a junior synonym of E. analis. Characters found in O. ingelorae are in accordance with those described for Chone, and we propose assigning O. ingelorae to this genus. The significance of ontogenetic character variations in the Sabellidae is discussed.     

Homology of prostomial and pharyngeal structures in eunicida (Annelida) based on innervation and morphological similarities

Eunicidan bristle worm families are commonly identified by the shape of their prostomia and pharyngeal structures. However, current hypotheses of homology among these structures are conflicting, making it difficult to assess morphological evolution, reconstruct phylogeny, and produce a stable classification. To generate more consistent hypotheses of homology among eunicidan anterior structures, the author examined the anterior morphology and the nervous system stained with anti‐α‐tubulin and serotonin antibodies in representative species of Eunicidae, Onuphidae, Oenonidae, Dorvilleidae and Lumbrineridae. The shape of the brain varied conspicuously among families; however, it has mostly the same commissures (usually two of the dorsal and five of the ventral roots of the circumoesophageal connective). The stomatogastric system is also conservative in composition, having two main pairs of stomatogastric nerves which vary in their relative position among the different families. Innervation similarities combined with correspondence and topological morphological similarities made it possible to present explicit hypotheses of primary homology of features, such as buccal lips, pharyngeal fold, and dorsolateral fold anterior extension. Buccal lips are present in all families; however, ventral pads on the prostomium of the Dorvillea line of Dorvilleidae are anterior prolongations of the pharyngeal fold and not buccal lips. All examined taxa, except dorvilleid species, have conspicuous dorsolateral fold anterior extension. In Eunicidae, this anterior extension is a transverse band, while in other families it is a pair of folds. Observed similarities also gave insights on the homology of maxillary elements of Dorvilleidae, providing background knowledge for future studies. J. Morphol., 2010. © 2010 Wiley‐Liss, Inc.     

Discrimination of extant Pan species and subspecies using the enamel–dentine junction morphology of lower molars

Previous research has demonstrated that species and subspecies of extant chimpanzees and bonobos can be distinguished on the basis of the shape of their molar crowns. Thus, there is potential for fossil taxa, particularly fossil hominins, to be distinguished at similar taxonomic levels using molar crown morphology. Unfortunately, due to occlusal attrition, the original crown morphology is often absent in fossil teeth, and this has limited the amount of shape information used to discriminate hominin molars. The enamel–dentine junction (EDJ) of molar teeth preserves considerable shape information, particularly in regard to the original shape of the crown, and remains present through the early stages of attrition. In this study, we investigate whether the shape of the EDJ of lower first and second molars can distinguish species and subspecies of extant Pan. Micro‐computed tomography was employed to non‐destructively image the EDJ, and geometric morphometric analytical methods were used to compare EDJ shape among samples of Pan paniscus (N = 17), Pan troglodytes troglodytes (N = 13), and Pan troglodytes verus (N = 18). Discriminant analysis indicates that EDJ morphology distinguishes among extant Pan species and subspecies with a high degree of reliability. The morphological differences in EDJ shape among the taxa are subtle and relate to the relative height and position of the dentine horns, the height of the dentine crown, and the shape of the crown base, but their existence supports the inclusion of EDJ shape (particularly those aspects of shape in the vertical dimension) in the systematic analysis of fossil hominin lower molars. Am J Phys Anthropol, 2009. © 2009 Wiley‐Liss, Inc.     

In vitro organogenesis of pancreas in Xenopus laevis dorsal lips treated with retinoic acid

Dorsal lips of Xenopus laevis may differentiate into pancreas after treatment with retinoic acid in vitro. The dorsal lip region is fated to be dorsal mesoderm and anterior endoderm. Dorsal lip cells isolated from stage 10 early gastrula differentiate into tissues such as notochord, muscle and pharynx. However, in the present study, dorsal lips treated with 10(-4) M retinoic acid for 3 h differentiated into pancreas-like structures accompanied by notochord and thick endodermal epithelium. Sections of the explants showed that some cells gathered and formed an acinus-like structure as observed under microscopes. In addition to the morphological changes, expressions of the pancreas-specific molecular markers, XIHbox8 and insulin, were induced in retinoic acid-treated dorsal lip explants. Therefore, it is suggested that retinoic acid may induce the dorsal lip cells to differentiate into a functional pancreas. However, continuous treatment with retinoic acid did not induce pancreas differentiation at any concentration. Dorsal lips treated with retinoic acid within 5 h after isolation differentiated into pancreas-like cells, while those treated after 15 h or more did not. The present study provided a suitable test system for analyzing pancreas differentiation in early vertebrate development.     

Snowflakes and feather-dusters – some challenges for soft-bottom fanworm systematics

The present study highlights paraphyly within traditional soft-bottom sabellin fanworm taxa. Two forms of the sabellid radiolar crown are recognised. The `snowflake' crown style comprises three pairs of radioles only, with few pinnules alternating along the length of the radioles and longest mid-radiole. The `feather-duster' crown style comprises few to many pairs of radioles, with numerous paired pinnules of relatively even length. Cladistic analyses revealed two new groups, whose respective members were assigned previously to Euchone and Jasmineira. These are pending revision and naming. Phylogenetic nomenclature is proposed as a more informative alternative to traditional Linnean nomenclature.     

Ultrastructure of the Spermathecae of Parafabricia ventricingulata and Three Species of Oriopsis (Polychaeta: Sabellidae)

Parafabricia ventricingulata females have a pair of spermathecae located in the radiolar crown anterio-dorsal to the buccal opening. The spermathecae have three regions; an entrance, 7 μm across, leading into a ciliated ‘atrium’ that is approximately 50 μm long; a connecting piece, 2–5 μm across and 25 μm long, leading from the ‘atrium’ to the sperm receptacle. The sperm receptacle is heavily pigmented and spherical. The sperm lie in a large mass in the receptacle with no particular orientation. Oriopsis bicoloris females have a pair of unpigmented spermathecae in the collar behind the radiolar crown. Each spermatheca is a simple blind duct 100 μm long, with a lumen 8 μm in diameter. Between 30 and 40 sperm lie in the lumen of each spermatheca. Oriopsis brevicollaris females have a pair of spermathecae located in the radiolar crown above the buccal opening. From the opening, 10 μm across, a blind duct runs for 90 μm. Sperm are stored in the distal region of the duct. Sperm lie along the margins of the duct in close contact with microvilli. Up to 10 sperm were found in each spermatheca. Oriopsis mobilis females have a pair of spermathecae located in the radiolar crown above the buccal opening. The opening, 3 μm across, leads into a blind duct that runs for 30 μm. Sperm are stored in the distal region of the spermathecae where they are embedded in spermathecal cells. Between 10 and 20 sperm were found in each spermatheca. Oriopsis dentata was found not to have spermathecae. The homologies of the spermathecae found within the Sabellinae and Fabriciinae (Sabellidae) and the Spirorbinae (Serpulidae) are discussed, but cannot be resolved on present evidence.     

Interspecific variation in the microanatomy of cosmetid harvestmen (Arachnida,Opiliones, Laniatores)

Scanning electron microscopy (SEM) is a useful tool for identifying interspecific variation in often overlooked structures that may represent useful sources for informative phylogenetic characters. In this study, we used SEM to compare the morphology of 12 cosmetid species from Central America, the Caribbean, and North America including multiple species for the genera Cynorta, Erginulus, and Paecilaema. To determine if microanatomical structures were unique to the cosmetid taxa under examination, we investigated the microanatomical structures of six additional species of gonyleptoidean harvestmen representing the families Agoristenidae, Cranaidae, Gonyleptidae, Manaosbiidae, and Stygnidae. Our results indicate that the shape of the ocularium (narrow, intermediate, or broad) did not vary within cosmetid genera, whereas the morphology of the rough pit glands on the eye mound varied considerably between species. Each cosmetid species had 10–20 rough pit glands on the ocularium whereas only the eye mounds of Avima intermedia (Agoristenidae) and Glysterus sp. (Gonyleptidae) had similar structures. With regards to the surface texture of the dorsal scutum, cosmetid harvestmen exhibited a rivulose‐microgranulate morphology (6 species), a microtuberculate‐rivulose‐microrgranulate morphology (4 species), or a microgranulate morphology (2 species). In contrast, each of the gonyleptoidean species exhibited a microgranulate pattern, with the exception of Stygnoplus clavotibialis, which had a rivulose‐microgranulate surface texture. For cosmetid harvestmen, we observed considerable interspecific variation in the shape and number of teeth on the fixed and moveable fingers of the male chelicerae. Similarly, we also observed interspecific variation in the distribution and shape of tubercles on the ventral and dorsal surfaces of the femur of the pedipalp. Overall, our results indicate that there are several microanatomical structures associated with the ocularium, dorsal scutum, male chelicera, and pedipalp that could represent informative phylogenetic characters in future taxonomic studies of cosmetid harvestmen. J. Morphol. 275:1386–1405, 2014. © 2014 Wiley Periodicals, Inc.     

Reconstructing pectoral appendicular muscle anatomy in fossil fish and tetrapods over the fins‐to‐limbs transition

The question of how tetrapod limbs evolved from fins is one of the great puzzles of evolutionary biology. While palaeontologists, developmental biologists, and geneticists have made great strides in explaining the origin and early evolution of limb skeletal structures, that of the muscles remains largely unknown. The main reason is the lack of consensus about appendicular muscle homology between the closest living relatives of early tetrapods: lobe‐finned fish and crown tetrapods. In the light of a recent study of these homologies, we re‐examined osteological correlates of muscle attachment in the pectoral girdle, humerus, radius, and ulna of early tetrapods and their close relatives. Twenty‐nine extinct and six extant sarcopterygians were included in a meta‐analysis using information from the literature and from original specimens, when possible. We analysed these osteological correlates using parsimony‐based character optimization in order to reconstruct muscle anatomy in ancestral lobe‐finned fish, tetrapodomorph fish, stem tetrapods, and crown tetrapods. Our synthesis revealed that many tetrapod shoulder muscles probably were already present in tetrapodomorph fish, while most of the more‐distal appendicular muscles either arose later from largely undifferentiated dorsal and ventral muscle masses or did not leave clear correlates of attachment in these taxa. Based on this review and meta‐analysis, we postulate a stepwise sequence of specific appendicular muscle acquisitions, splits, and fusions that led from the ancestral sarcopterygian pectoral fin to the ancestral tetrapod forelimb. This sequence largely agrees with previous hypotheses based on palaeontological and comparative work, but it is much more comprehensive in terms of both muscles and taxa. Combined with existing information about the skeletal system, our new synthesis helps to illuminate the genetic, developmental, morphological, functional, and ecological changes that were key components of the fins‐to‐limbs transition.     

Brief communication: Contributions of enamel‐dentine junction shape and enamel deposition to primate molar crown complexity

Molar crown morphology varies among primates from relatively simple in some taxa to more complex in others, with such variability having both functional and taxonomic significance. In addition to the primary cusps, crown surface complexity derives from the presence of crests, cuspules, and crenulations. Developmentally, this complexity results from the deposition of an enamel cap over a basement membrane (the morphology of which is preserved as the enamel‐dentine junction, or EDJ, in fully formed teeth). However, the relative contribution of the enamel cap and the EDJ to molar crown complexity is poorly characterized. In this study we examine the complexity of the EDJ and enamel surface of a broad sample of primate (including fossil hominin) lower molars through the application of micro‐computed tomography and dental topographic analysis. Surface complexity of the EDJ and outer enamel surface (OES) is quantified by first mapping, and then summing, the total number of discrete surface orientation patches. We investigate the relative contribution of the EDJ and enamel cap to crown complexity by assessing the correlation in patch counts between the EDJ and OES within taxa and within individual teeth. We identify three patterns of EDJ/OES complexity which demonstrate that both crown patterning early in development and the subsequent deposition of the enamel cap contribute to overall crown complexity in primates. Am J Phys Anthropol, 2010. © 2010 Wiley‐Liss, Inc.     

Histological and ultrastructural aspects of the nasal complex in the harbour porpoise,Phocoena phocoena

During the evolution of odontocetes, the nasal complex was modified into a complicated system of passages and diverticulae. It is generally accepted that these are essential structures for nasal sound production. However, the mechanism of sound generation and the functional significance of the epicranial nasal complex are not fully understood. We have studied the epicranial structures of harbor porpoises (Phocoena phocoena) using light and electron microscopy with special consideration of the nasal diverticulae, the phonic lips and dorsal bursae, the proposed center of nasal sound generation. The lining of the epicranial respiratory tract with associated diverticulae is consistently composed of a stratified squamous epithelium with incomplete keratinization and irregular pigmentation. It consists of a stratum basale and a stratum spinosum that transforms apically into a stratum externum. The epithelium of the phonic lips comprises 70–80 layers of extremely flattened cells, i.e., four times more layers than in the remaining epicranial air spaces. This alignment and the increased number of desmosomes surrounding each cell indicate a conspicuous rigid quality of the epithelium. The area surrounding the phonic lips and adjacent fat bodies exhibits a high density of mechanoreceptors, possibly perceiving pressure differentials and vibrations. Mechanoreceptors with few layers and with perineural capsules directly subepithelial of the phonic lips can be distinguished from larger, multi‐layered mechanoreceptors without perineural capsules in the periphery of the dorsal bursae. A blade‐like elastin body at the caudal wall of the epicranial respiratory tract may act as antagonist of the musculature that moves the blowhole ligament. Bursal cartilages exist in the developmental stages from fetus through juvenile and could not be verified in adults. These histological results support the hypothesis of nasal sound generation for the harbor porpoise and display specific adaptations of the echolocating system in this species. J. Morphol. 2009. © 2009 Wiley‐Liss, Inc.     

Development,morphology and ultrastructure of the branchial crown of Fabricia stellaris (Müller, 1774) (Polychaeta: Sabellida: Fabriciinae)

Randel, N. and Bick, A. 2011. Development, morphology and ultrastructure of the branchial crown of Fabricia stellaris (Müller, 1774) (Polychaeta: Sabellida: Fabriciinae). —Acta Zoologica (Stockholm) 93 : 409–421. Sabellidae and Serpulidae are well‐known tube‐building polychaetes with a distinctive and often spectacularly colourful branchial crown. Morphological investigations suggest that these taxa form the monophyletic clade Sabellida, with the adelphotaxa Sabellidae and Serpulidae, but the relationship between these taxa remains ambiguous. Molecular investigations have indicated that the Fabriciinae, major taxon of Sabellidae, belongs to Serpulidae, thereby making Sabellidae paraphyletic; however, morphological characters are absent to support this result. We investigate the development, anatomy and ultrastructure of the branchial crown of Fabricia stellaris (Müller, 1774), describing morphological characteristics useful not only for constructing morphological phylogenies but also for understanding the evolution of the branchial crown. The morphology of the radioles and pinnules does not differ from each other. The supporting tissue of the branchial crown consists of myoepithelial cells and a solid extracellular matrix (ECM). Both ciliated and non‐ciliated cells form the epidermal layer; ciliated cells shape the food groove. Most important is the result that radioles and pinnules within Sabellida may not be homologous, because the morphology and the branching of radioles and pinnules are completely different between Sabellinae, Fabriciinae and Serpulidae. The terms ‘primary branch’ for radioles and ‘secondary branch’ for pinnules are proposed for Fabriciinae. The phylogeny of the Sabellida is discussed.     

Evolutionary morphology of the hemolymph vascular system in hermit and king crabs (Crustacea: Decapoda: Anomala)

The morphological transformation of hermit crabs into crab‐like king crabs in the evolution of decapod crustaceans represents a remarkable case of carcinization or evolutionary shaping into a crab‐like form. In this study, we focus on internal organs such as the hemolymph vascular system and adjacent anatomical structures of several Recent hermit crab (Paguridae) and king crab (Lithodidae) species. There are various correspondences in the morphology of the arterial systems in the dorsal cephalothorax of the two taxa, especially with regard to the anterior aorta, anterior lateral arteries, and hepatic arteries. In the pleon, the posterior aorta in both taxa displays a proximal bifurcation and follows an asymmetrical course. The ventral vessel system, on the other hand, which mainly supplies the limbs, differs significantly between the taxa, with pagurids displaying the plesiomorphic condition. The pattern of the ventral vessel system in Lithodidae is influenced by morphological transformations of integumental structures during carcinization. One of these transformations was the broadening of the sternites, which resulted in a widening of the space between the endosternites. In addition, changes in the morphology of the endophragmal skeleton in Lithodidae led to an increase in the potential for intraspecific variability and interspecific variation in the arterial branching pattern. J. Morphol., 2013. © 2013 Wiley Periodicals, Inc.     

Enamel-dentine junction (EDJ) morphology distinguishes the lower molars of Australopithecus africanus and Paranthropus robustus

Tooth crown morphology plays a central role in hominin systematics, but the removal of the original outer enamel surface by dental attrition often eliminates from consideration the type of detailed crown morphology that has been shown to discriminate among hominin taxa. This reduces the size of samples available for study. The enamel-dentine junction (EDJ) is the developmental precursor and primary contributor to the morphology of the unworn outer enamel surface, and its morphology is only affected after considerable attrition. In this paper, we explore whether the form of the EDJ can be used to distinguish between the mandibular molars of two southern African fossil hominins: Paranthropus (or Australopithecus) robustus and Australopithecus africanus. After micro-computed tomographic scanning the molar sample, we made high-resolution images of the EDJ and used geometric morphometrics to compare EDJ shape differences between species, in addition to documenting metameric variation along the molar row within each species. Landmarks were collected along the marginal ridge that runs between adjacent dentine horns and around the circumference of the cervix. Our results suggest that the morphology of the EDJ can distinguish lower molars of these southern African hominins, and it can discriminate first, second, and third molars within each taxon. These results confirm previous findings that the EDJ preserves taxonomically valuable shape information in worn teeth. Mean differences in EDJ shape, in particular dentine horn height, crown height, and cervix shape, are more marked between adjacent molars within each taxon than for the same molar between the two taxa.     

Phylogeny of extant and fossil Juglandaceae inferred from the integration of molecular and morphological data sets

It is widely acknowledged that integrating fossils into data sets of extant taxa is imperative for proper placement of fossils, resolution of relationships, and a better understanding of character evolution. The importance of this process has been further magnified because of the crucial role of fossils in dating divergence times. Outstanding issues remain, including appropriate methods to place fossils in phylogenetic trees, the importance of molecules versus morphology in these analyses, as well as the impact of potentially large amounts of missing data for fossil taxa. In this study we used the angiosperm clade Juglandaceae as a model for investigating methods of integrating fossils into a phylogenetic framework of extant taxa. The clade has a rich fossil record relative to low extant diversity, as well as a robust molecular phylogeny and morphological database for extant taxa. After combining fossil organ genera into composite and terminal taxa, our objectives were to (1) compare multiple methods for the integration of the fossils and extant taxa (including total evidence, molecular scaffolds, and molecular matrix representation with parsimony [MRP]); (2) explore the impact of missing data (incomplete taxa and characters) and the evidence for placing fossils on the topology; (3) simulate the phylogenetic effect of missing data by creating "artificial fossils"; and (4) place fossils and compare the impact of single and multiple fossil constraints in estimating the age of clades. Despite large and variable amounts of missing data, each of the methods provided reasonable placement of both fossils and simulated "artificial fossils" in the phylogeny previously inferred only from extant taxa. Our results clearly show that the amount of missing data in any given taxon is not by itself an operational guideline for excluding fossils from analysis. Three fossil taxa (Cruciptera simsonii, Paleoplatycarya wingii, and Platycarya americana) were placed within crown clades containing living taxa for which relationships previously had been suggested based on morphology, whereas Polyptera manningii, a mosaic taxon with equivocal affinities, was placed firmly as sister to two modern crown clades. The position of Paleooreomunnea stoneana was ambiguous with total evidence but conclusive with DNA scaffolds and MRP. There was less disturbance of relationships among extant taxa using a total evidence approach, and the DNA scaffold approach did not provide improved resolution or internal support for clades compared to total evidence, whereas weighted MRP retained comparable levels of support but lost crown clade resolution. Multiple internal minimum age constraints generally provided reasonable age estimates, but the use of single constraints provided by extinct genera tended to underestimate clade ages.     

Three‐dimensional reconstruction of the odontophoral cartilages of Caenogastropoda (Mollusca: Gastropoda) using micro‐CT: Morphology and phylogenetic significance

Odontophoral cartilages are located in the molluscan buccal mass and support the movement of the radula during feeding. The structural diversity of odontophoral cartilages is currently known only from limited taxa, but this information is important for interpreting phylogeny and for understanding the biomechanical operation of the buccal mass. Caenogastropods exhibit a wide variety of feeding strategies, but there is little comparative information on cartilage morphology within this group. The morphology of caenogastropod odontophoral cartilages is currently known only from dissection and histology, although preliminary results suggest that they may be structurally diverse. A comparative morphological survey of 18 caenogastropods and three noncaenogastropods has been conducted, sampling most major caenogastropod superfamilies. Three‐dimensional models of the odontophoral cartilages were generated using X‐ray microscopy (micro‐CT) and reconstruction by image segmentation. Considerable morphological diversity of the odontophoral cartilages was found within Caenogastropoda, including the presence of thin cartilaginous appendages, asymmetrically overlapping cartilages, and reflexed cartilage margins. Many basal caenogastropod taxa possess previously unidentified cartilaginous support structures below the radula (subradular cartilages), which may be homologous to the dorsal cartilages of other gastropods. As subradular cartilages were absent in carnivorous caenogastropods, adaptation to trophic specialization is likely. However, incongruence with specific feeding strategies or body size suggests that the morphology of odontophoral cartilages is constrained by phylogeny, representing a new source of morphological characters to improve the phylogenetic resolution of this group. J. Morphol. 2009. © 2008 Wiley‐Liss, Inc.     

Modifications in call characteristics and sonic apparatus morphology during puberty in Ophidion rochei (actinopterygii: Ophidiidae)

Juveniles, females, and males of Ophidion rochei share similar external morphology, probably because they are mainly active in the dark, which reduces the role of visual cues. Their internal sonic apparatuses, however, are complex: three pairs of sonic muscles, and highly modified vertebrae and ribs are involved in sound production. The sonic apparatus of males differs from juveniles and females in having larger swimbladder plates (modified ribs associate with the swimbladder wall) and sonic muscles, a modified swimbladder shape and a mineralized structure called the “rocker bone” in front of the swimbladder. All of these male traits appear at the onset of sexual maturation. This article investigates the relationship between morphology and sounds in male O. rochei of different sizes. Despite their small size range total length (133–170 mm TL), the five specimens showed pronounced differences in sound‐production apparatus morphology, especially in terms of swimbladder shape and rocker bone development. This observation was reinforced by the positive allometry measured for the rocker bone and the internal tube of the swimbladder. The differences in morphology were related to marked differences in sound characteristics (especially frequency and pulse duration). These results suggest that male calls carry information about the degree of maturity. Deprived of most visual cues, ophidiids probably have invested in other mechanisms to recognize and distinguish among individual conspecifics and between ophidiid species. As a result, their phenotypes are externally similar but internally very different. In these taxa, the great variability of the sound production apparatus means this complex system is a main target of environmental constraints. J. Morphol. 275:650–660, 2014. © 2014 Wiley Periodicals, Inc.