Development of the ear, hearing capabilities and laterophysic connection in the spotfin butterflyfish (Chaetodon ocellatus)

The ontogeny of the ear, swim bladder and laterophysic connection was investigated in the spotfin butterflyfish, Chaetodon ocellatus in order to determine how the development of the laterophysic connection (a Chaetodon synapomorphy) is correlated with ontogenetic changes in the hearing capabilities in these abundant and ecologically important coral reef fishes. Histological and cleared and stained material revealed that the medial opening in the lateral line canal in the supracleithrum (which defines the laterophysic connection), an inflated physoclistous swim bladder, and the three otolithic organs are already present in the smallest individuals examined (7?C15?mm SL). The medial opening in the supracleithrum increases in size and the cylindrical swim bladder horns form after the loss of the head plates characteristic of the tholichthys stage, in individuals ??29?mm SL. The three sensory maculae of the ear increase in size, and the shape of the sacculus changes most dramatically with fish growth; hair cell density is highest in the utriculus. Physiological analysis of the reponse to sound pressure showed that larval and juvenile C. ocellatus had a hearing sensitivity peak at 100?C200?Hz, which was ~30?C40?dB more sensitive than that measured in larval coral reef fishes (e.g., damselfishes) that lack swim bladder horns. C. ocellatus did not show any ontogenetic changes in sensitivity to sound pressure, which may be explained by the fact that the growth of the swim bladder horns maintains the small distance between the swim bladder and ear that was established earlier during the larval stage. The timing of the development of the swim bladder horns suggests that if the laterophysic connection has a sensory acoustic function, its presence in individuals >29?mm SL suggests that its role is limited to post-settlement, reef-based behaviors.     

The laterophysic connection in chaetodontid butterflyfish: morphological variation and speculations on sensory function

The laterophysic connection is a novel specialization in chaetodontid butterflyfish, in which paired diverticula of the swim-bladder ('horns') extend anteriorly and approach or directly contact a medial fossa in the lateral line canal contained within the supracleithrum. This study examined the morphology of the laterophysic connection in eight ecologically diverse species belonging to five subgenera within Chaetodon. Two types of laterophysic connections, indirect and direct, were found among Chaetodon species. Intraspecific variation (including sexual dimorphism) in the morphology of the laterophysic connection was not found. The type of laterophysic connection is not correlated with ecological characteristics among Chaetodon species, but appears to be correlated with subgeneric affinities of Chaetodon species. The presence of swim-bladder horns probably increases pressure sensitivity to the inner ear. It is suggested that the presence of a direct laterophysic connection, and possibly an indirect laterophysic connection, imparts pressure sensitivity to the lateral line canal system as well.     

The evolution of the laterophysic connection with a revised phylogeny and taxonomy of butterflyfishes (Teleostei: Chaetodontidae)

The higher‐level relationships of butterflyfishes were examined using 37 morphological characters. This analysis combines characters derived from a histological study describing variation in the morphology of the laterophysic connection (an association between the swim bladder and the lateral‐line canals) with previously described morphological characters. The phylogenetic analysis resulted in four equally parsimonious trees that only differed in the placement of two of the 11 chaetodontid genera (Amphichaetodon and Forcipiger). We compare our analysis with previous hypotheses, present a new taxonomy consistent with the proposed cladistic relationships, and diagnose Chaetodon with five unreversed synapomorphies, including the evolution of characters composing the laterophysic connection. A new character‐based diagnosis of Chaetodon is provided and species are allocated accordingly; Chaetodon now includes the former Parachaetodon ocellatus and excludes the former subgenera Prognathodes and Roa. The evolution of the laterophysic connection is examined by optimizing character‐state transformations on the new hypothesis of relationships.     

Swim bladder and posterior lateral line nerve of the nurseryfish, Kurtus gulliveri (Perciformes: Kurtidae)

The morphology of the swim bladder and inner ear of the nurseryfish, Kurtus gulliveri, appear adapted for enhanced pressure wave reception. The saccule is enlarged and surrounded by very thin bone and two large fontanelles that would present reduced resistance to pressure waves. The swim bladder is elaborate, with six dorsolaterally projecting pairs of lobes that are tightly encased in ribs and an additional caudally projecting pair of lobes encased in the first hemal spine. The ribs and musculature surrounding the swim bladder laterally are very thin, so that four or five "rib windows" are readily apparent on back-lit specimens. This swim bladder-rib configuration would also present reduced resistance to pressure waves to enhance function as a peripheral auditory structure. However, high-resolution X-ray computed tomography and dissection reveal no anterior projections of the swim bladder that could serve as a mechanical coupling to the inner ear. The posterior lateral line nerve is well developed and lies directly over the tips of the ribs encasing the swim bladder lobes. This nerve is not, however, associated with a lateral line canal and a lateral line canal is absent on most of the body. We hypothesize that the posterior lateral line nerve transmits mechanosensory information from the swim bladder.     

Post‐embryonic development of canal and superficial neuromasts and the generation of two cranial lateral line phenotypes

The relatively simple structural organization of the cranial lateral line system of bony fishes provides a valuable context in which to explore the ways in which variation in post‐embryonic development results in functionally distinct phenotypes, thus providing a link between development, evolution, and behavior. Vital fluorescent staining, histology, and scanning electron microscopy were used to describe the distribution, morphology, and ontogeny of the canal and superficial neuromasts on the head of two Lake Malawi cichlids with contrasting lateral line canal phenotypes (Tramitichromis sp. [narrow‐simple, well‐ossified canals with small pores] and Aulonocara stuartgranti [widened, more weakly ossified canals with large pores]). This work showed that: 1) the patterning (number, distribution) of canal neuromasts, and the process of canal morphogenesis typical of bony fishes was the same in the two species, 2) two sub‐populations of neuromasts (presumptive canal neuromasts and superficial neuromasts) are already distinguishable in small larvae and demonstrate distinctive ontogenetic trajectories in both species, 3) canal neuromasts differ with respect to ontogenetic trends in size and proportions between canals and between species, 4) the size, shape, configuration, physiological orientation, and overall rate of proliferation varies among the nine series of superficial neuromasts, which are found in both species, and 5) in Aulonocara, in particular, a consistent number of canal neuromasts accompanied by variability in the formation of canal pores during canal morphogenesis demonstrates independence of early and late phases of lateral line development. This work provides a new perspective on the contributions of post‐embryonic phases of lateral line development and to the generation of distinct phenotypes in the lateral line system of bony fishes. J. Morphol. 277:1273–1291, 2016. © 2016 Wiley Periodicals, Inc.     

Swim bladder gas gland cells produce surfactant: in vivo and in culture

Electron microscopical examination of gas gland cells of the physostome European eel (Anguilla anguilla) and of the physoclist perch (Perca fluviatilis) revealed the presence of significant numbers of lamellar bodies, which are known to be involved in surfactant secretion. In the perch, in which the gas gland is a compact structure and gas gland cells are connected to the swim bladder lumen via small canals, lamellar bodies were also found in flattened cells forming the swim bladder epithelium. Flat epithelial cells are absent in the eel swim bladder, in which the whole epithelium consists of cuboidal gas gland cells. In both species, Western blot analysis using specific antibodies to human surfactant protein A (SP-A) showed a cross-reaction with swim bladder tissue homogenate proteins of approximately 65 kDa and in the eel occasionally of approximately 120 kDa, probably representing SP-A-like proteins in a dimeric and a tetrameric state. An additional band was observed at approximately 45 kDa. Western blots using antibodies to rat SP-D again resulted in a single band at approximately 45 kDa in both species, suggesting that there might be a cross-reaction of the antibody to human SP-A with an SP-D-like protein of the swim bladder tissue. To localize the surfactant protein, eel gas gland cells were cultured on permeable supports. Under these conditions, the gas gland cells regain their characteristic polarity. Electron microscopy confirmed the presence of lamellar bodies in cultured cells, and occasionally, exocytotic events were observed. Immunohistochemical staining using an antibody to human SP-A demonstrated the presence of surfactant protein only in luminal membranes and in adjacent lateral membranes. Only occasionally, evidence was found for the presence of surfactant protein in lamellar bodies.     

Morphology and development of the multiple lateral line canals on the trunk in two species of Hexagrammos (Scorpaeniformes,Hexagrammidae)

The morphology and development of the multiple lateral line canals (canals 1–5 in dorsal to ventral sequence) on the trunk of two representative hexagrammids, Hexagrammos decagrammus and H. stelleri, were studied using histological and cleared and stained material. The morphology of the lateral line scales of which the lateral line canals are composed and the distribution of canal neuromasts within them were described quantitatively. We hypothesized that 1) one neuromast is contained in each lateral line scale and all five canals contain neuromasts, 2) all five canals develop similarly, and 3) the multiple trunk canals are an adaptation for the alteration of lateral line function. Lateral line scale morphology was found to be similar among the five canals in Hexagrammos decagrammus and H. stelleri. However, canal 3 is significantly wider than the other four canals. It is the only one of the five canals connected to the canals on the head, and more significantly, it is the only one of the five canals that contains neuromasts. The lateral line scales that comprise all five lateral line canals show the same pattern of development whether or not they contain neuromasts. The five canals develop asynchronously, and each of the canals develops either rostro-caudally or caudo-rostrally. Canal 3 is the homologue of a single trunk canal in other teleosts; canals 1, 2, 4, and 5 are apomorphic features of the two species of Hexagrammos. Canals 1, 2, 4, and 5 cannot be functional components of the lateral line system because they do not contain neuromasts and thus cannot be adaptations for the alteration of lateral line function. The occurrence of lateral line canals lacking neuromasts demands a direct assessment of neuromast distributions in the lateral line canals among fishes. Finally, our data suggest that the putative role of neuromasts in the morphogenesis of lateral line canals and the nature of neuromast-bone relationships need to be critically reevaluated. J. Morphol. 233:195–214, 1997. © 1997 Wiley-Liss, Inc.     

Morphological development of the swim bladder in hatchery-reared striped trumpeter Latris lineata

This study examined swim bladder morphogenesis in three cohorts of striped trumpeter (Latris lineata), a euphysoclist species with physostomous larvae. The swim bladder was first discernible 1–2 days after hatching as an evagination on the dorsal surface of the incipient digestive tract. It comprised a cluster of mesenchymal cells surrounding an inner primordium of epithelial cells. At mouth opening in larvae of 5.3 mm standard length (SL), the swim bladder was noticeably enlarged. Histologically, the swim bladder lumen was dilated and liquid filled. The pneumatic duct was first seen during the dilation stage and the rete mirabile began forming among the connective tissue surrounding the swim bladder. Initial swim bladder inflation occurred on day 11 post‐hatching in Cohort 1, at 14°C, and day 9 post‐hatching, in Cohorts 2 and 3, at 16°C. Histologically, the lumens of inflated swim bladders were ellipsoid and the epithelium was squamous, except for cuboidal gas gland cells at the anterio‐ventral and anterio‐lateral regions of the swim bladder. During the initial inflation interval the pneumatic duct was dilated in larvae both with and without swim bladder inflation. The pneumatic duct began to regress in some larvae over 7.5 mm SL. The swim bladder of striped trumpeter was similar to larvae of other altricial perciform marine fish in respect to organ derivation, tissue differentiation, luminal dilation and initial gaseous inflation. However, variations, particularly the delay in initial swim bladder inflation until after the start of feeding, were observed that could be fundamental to problems encountered during larval rearing.     

A novel hearing specialization in the New Zealand bigeye,Pempheris adspersa

The New Zealand bigeye, Pempheris adspersa, is a nocturnal planktivore and has recently been found to be an active sound producer. The rostral end of the swim bladder lies adjacent to Baudelot''s ligament which spans between the bulla and the cleithrum bone of the pectoral girdle. The aim of this study was to use the auditory evoked potential technique to physiologically test the possibility that this structure provides an enhanced sensitivity to sound pressure in the bigeye. At 100 Hz, bigeye had hearing sensitivity similar to that of goldfish (species with a mechanical connection between the swim bladder and the inner ear mediated by the Weberian ossicles) and were much more sensitive than other teleosts without ancillary hearing structures. Severing Baudelot''s ligament bilaterally resulted in a marked decrease in hearing sensitivity, as did swim bladder puncture or lateral line blockage. These results show that bigeye have an enhanced sensitivity to sound pressure and provide experimental evidence that the functional basis of this sensitivity represents a novel hearing specialization in fish involving the swim bladder, Baudelot''s ligament and the lateral line.     

皖北志留纪盔甲鱼类的新发现

本文记述了盔甲鱼类的一新属种——珍奇秀甲鱼(Geraspis rara gen. et sp. nov.),它代表—新科(Geraspididae fam. nov)。头甲及其后覆盖鳞片部分呈正常连接。主要特征为:间带短,角呈狭长的三角形,伸向后方。侧背沟靠近头甲中背线。鳞为小而密集的菱形。     

华西雨蛙寄生多盘虫科单殖吸虫一新种

在云南省新平县(24°N,101°32’E)采集的华西雨蛙Hyla a.annectans膀胱内检获多盘虫属1新种,新平多盘虫Polystoma xinpingensis sp.nov.。124只华西雨蛙中18只华西雨蛙感染,自然感染率为14.5%。新种与多盘虫属记录种最显著的区别在于:虫体体型小,其体长仅为2967μm。内侧肠管于虫体后1/3处仅形成2条横跨虫体的联合肠管,其它记录种肠管分支多数或形成较复杂的网状。睾丸巨大,呈滤泡状,分散分布直达虫体中部。新种的正、副模式标本保存在云南师范大学生命科学学院。     

Morphology and ontogeny of multiple lateral‐line canals in the rock prickleback,Xiphister mucosus (Cottiformes: Zoarcoidei: Stichaeidae)

The structure and ontogeny of lateral‐line canals in the Rock Prickleback, Xiphister mucosus, were studied using cleared‐and‐stained specimens, and the distribution and morphology of neuromasts within lateral‐line canals were examined using histology. X. mucosus has seven cephalic canals in a pattern that, aside from four branches of the infraorbital canals, is similar to that of most teleostean fishes. Unlike most other teleosts, however, X. mucosus features multiple trunk lateral‐line canals. These include a short median posterior extension of the supratemporal canal and three paired, branching canals located on the dorsolateral, mediolateral, and ventrolateral surfaces. The ventrolateral canal (VLC) includes a loop across the ventral surface of the abdomen. All trunk canals, as well as the branches of the infraorbitals, are supported by small, dermal, ring‐like ossifications that develop independently from scales. Trunk canals develop asynchronously with the mediodorsal and dorsolateral canals (DLC) developing earliest, followed by the VLC, and, finally, by the mediolateral canal (MLC). Only the mediodorsal and DLC connect to the cephalic sensory canals. Fractal analysis shows that the complexity of the trunk lateral‐line canals stabilizes when all trunk canals develop and begin to branch. Histological sections show that neuromasts are present in all cephalic canals and in the DLC and MLC of the trunk. However, no neuromasts were identified in the VLC or its abdominal loop. The VLC cannot, therefore, directly function as a part of the mechanosensory system in X. mucosus. The evolution and functional role of multiple lateral‐line canals are discussed. J. Morphol. 276:1218–1229, 2015. © 2015 Wiley Periodicals, Inc.     

Morphogenesis of sense organs and behavioural changes in larvae of the brown-marbled grouper Epinephelus fuscoguttatus (Forsskål)

The morphogenesis of sense organs and related behavioural changes in the hatchery-reared brown-marbled grouper Epinephelus fuscoguttatus larvae were examined to gain better understanding of its early life history because ecological field observations for grouper species is difficult. The newly hatched larvae (2.1 mm total length) had developing eyes and otic vesicles, a pair of free neuromast on the head and ciliated olfactory epithelium. At 3 days post hatching (dph), the eyes became fully pigmented with pure-cone retinae, the semicircular canals formed in the inner ear, and the larvae (2.8 mm) were able to swim horizontally, preying on rotifers. Retinal rods and the intra-oral taste buds at pharyngeal appeared next. The olfactory lamellae and the head lateral line system then formed, and the inner ears developed completely in the larvae during the metamorphosis period (15–40 dph; 5.1–18.1 mm). At settlement (50 dph; 32.8 mm), the fish possessed taste buds in the mouth entrance region, and the lateral line system developed completely. The sensory development correlates well with the known aspects of its life history at sea whereby the larvae can feed early and avoid predators during the passive drift, are able to swim shoreward to search nursery ground along the metamorphosis stage and survive in seagrass beds at settlement.     

Does the Hearing Sensitivity in Thorny Catfishes Depend on Swim Bladder Morphology?

Background

Thorny catfishes exhibit large variations in swim bladder morphology. These organs are of different sizes, forms and may have simple or branched diverticula. The swim bladder plays an important role in otophysans because it enhances their hearing sensitivity by transmitting sound pressure fluctuations via ossicles to the inner ear.

Methodology/Principal Findings

To investigate if a form-function relationship exists, the swim bladder morphology and hearing ability were analyzed in six species. The morphology was quantified by measuring the length, width and height and calculating a standardized swim bladder length (sSBL), which was then used to calculate the relative swim bladder length (rSBL). Hearing was measured using the auditory evoked potential (AEP) recording technique. Two species had simple apple-shaped and four species heart-shaped (cordiform) bladders. One of the latter species had short unbranched diverticula on the terminal margin, two had a secondary bladder and two had many long, branched diverticula. The rSBL differed significantly between most of the species. All species were able to detect frequencies between 70 Hz and 6 kHz, with lowest thresholds found between 0.5 and 1 kHz (60 dB re 1 µPa). Hearing curves were U-shaped except in Hemidoras morrisi in which it was ramp-like. Mean hearing thresholds of species possessing smaller rSBLs were slightly lower (maximum 8.5 dB) than those of species having larger rSBLs.

Conclusions/Significance

The current findings reveal a relationship between swim bladder form and its function among thorny catfishes. Relatively smaller swim bladders resulted in relatively better hearing. This is in contrast to a prior inter-familial study on catfishes in which species with large unpaired bladders possessed higher sensitivity at higher frequencies than species having tiny paired and encapsulated bladders.     

Characterization of the primary sonic muscles in Carapus acus (Carapidae): a multidisciplinary approach

Sound production in carapid fishes results from the action of extrinsic muscles that insert into the swim bladder. Biochemical, histochemical and morphological techniques were used to examine the sonic muscles and compare them with epaxial muscles in Carapus acus. Sonic fibres are thicker than red and thinner than white epaxial fibres, and sonic fibres and myofibrils exhibit an unusual helicoidal organization: the myofibrils of the centre are in a straight line whereas they are more and more twisted towards the periphery. Sonic muscles have both features of red (numerous mitochondria, high glycogen content) and white (alkali-stable ATPase) fibres. They differ also in the isoforms of the light chain (LC3) and heavy chain (HC), in having T tubules at both the Z-line and the A-I junction and in a unique parvalbumin isoform (PAI) that may aid relaxation. All these features lead to the expression of two assumptions about sound generation: the sonic muscle should be able to perform fast and powerful contractions that provoke the forward movement of the forepart of the swim bladder and the stretching and "flapping" of the swim bladder fenestra; the helicoidal organization allows progressive drawing of the swim bladder fenestra which emits a sound when rapidly released in a spring-like manner.     

The membranous labyrinth and its innervation inChaetodon trifasciatus (Pisces,Teleostei, Chaetodontidae)

Synopsis In the butterflyfishChaetodon trifasciatus, the labyrinth is characterized by its elevated form and especially the size of the vertical canals, the almost circular form of the horizontal canal and its posterior opening not directly in the utriculus but in the common pillar of the two vertical canals. There is an almost complete separation between utriculus and sacculus which are only linked by a virtual pore. The lagena, which is medially situated to the posterior part of the sacculus, is separated from it by an incomplete vertical wall. There are two maculae neglectae, the anterior macula being situated in the pore separating utriculus from sacculus and filling this pore, the posterior in a gutter of the floor of the utriculus. A long and narrow endolymphatic canal, originating from the sacculus close to the communication with the utriculus, follows the common pillar of the two vertical canals and widens into an endolymphatic sac at the top of the membranous labyrinth. The innervation of the labyrinth is made by the acoustic ganglion, which is connected to the brain by two roots and elongated into three parts: the anterior part innervates the anterior and horizontal cristae and the utricular and saccular maculae; the middle part innervates the macula sacculae and the macula neglecta 1; the posterior part innervates the macula neglecta II, the macula lagenae and the posterior crista. The important size of the vertical canals and the almost circular form of the horizontal canal may reflect very precise locomotory aptitudes.     

Morphology of the mechanosensory lateral line system in the Atlantic Stingray,Dasyatissabina: The mechanotactile hypothesis

The biological function of anatomical specializations in the mechanosensory lateral line of elasmobranch fishes is essentially unknown. The gross and histological features of the lateral line in the Atlantic stingray, Dasyatis sabina, were examined with special reference to its role in the localization and capture of natural invertebrate prey. Superficial neuromasts are arranged in bilateral rows near the dorsal midline from the spiracle to the posterior body disk and in a lateral position along the entire length of the tail. All dorsal lateral line canals are pored, contain sensory neuromasts, and have accessory lateral tubules that most likely function to increase their receptive field. The pored ventral canal system consists of the lateral hyomandibular canal along the disk margin and the short, separate mandibular canal on the lower jaw. The extensive nonpored and relatively compliant ventral infraorbital, supraorbital, and medial hyomandibular canals form a continuous complex on the snout, around the mouth, and along the abdomen. Vesicles of Savi are small mechanosensory subdermal pouches that occur in bilateral rows only along the ventral midline of the rostrum. Superficial neuromasts are best positioned to detect water movements along the transverse body axis such as those produced by tidal currents, conspecifics, or predators. The pored dorsal canal system is positioned to detect water movements created by conspecifics, predators, or possibly distortions in the flow field during swimming. Based upon the stingray lateral line morphology and feeding behavior, we propose the Mechanotactile Hypothesis, which states that the ventral nonpored canals and vesicles of Savi function as specialized tactile mechanoreceptors that facilitate the detection and capture of small benthic invertebrate prey. J. Morphol. 238:1–22, 1998. © 1998 Wiley-Liss, Inc.     

Development of the supraorbital and mandibular lateral line canals in the cichlid,Archocentrus nigrofasciatus

The development of two of the cranial lateral line canals is described in the cichlid, Archocentrus nigrofasciatus. Four stages of canal morphogenesis are defined based on histological analysis of the supraorbital and mandibular canals. "Canal enclosure" and "canal ossification" are defined as two discrete stages in lateral line canal development, which differ in duration, an observation that has interesting implications for the ontogeny of lateral line function. Canal diameter in the vicinity of individual neuromasts begins to increase before ossification of the canal roof in each canal segment; this increase in canal diameter is accompanied by an increase in canal neuromast size. The mandibular canal generally develops later than the supraorbital canal in this species, but in both of these canals development of the different canal segments contained within a single dermal bone is asynchronous. These observations suggest that a dynamic process requiring integration and interaction among different tissues, in both space and time, underlies the development of the cranial lateral line canal system. The supraorbital and mandibular canals appear to demonstrate a "one-component" pattern of development in Archocentrus nigrofasciatus, where the walls of each canal segment grow up from the underlying dermal bone and then fuse to form the bony canal roof. This is contrary to numerous published reports that describe a "two-component" pattern of development in teleosts where the bony canal ossifies separately and then fuses with an underlying dermal bone. A survey of the literature in which lateral line canal development is described using histological analysis suggests that the occurrence of two different patterns of canal morphogenesis ("one-component" and "two-component") may be due to phylogenetic variation in the pattern of the development of the lateral line canals.     

Mechanosensory system of the lateral line in the subantarctic Patagonian blenny Eleginops maclovinus

This study describes the cephalic and trunk lateral line systems in Patagonian blenny Eleginops maclovinus juveniles, providing morphological details for pores, canals and neuromasts. Eleginops maclovinus juveniles possess a complete laterodorsal lateral line that extends from the upper apex of the gill opening along the trunk as far as the caudal fin. The lateral line was ramified through pores and canals. The following pores were recorded: four supraorbital pores, with two along the eye border and two on the snout; seven infraorbital pores, with three on the lacrimal bone and four being infraorbital; five postorbital pores, with three along the preopercular border (upper preoperculum branch) and two on the bone curvature (inferior preoperculum branch); and four mandibular pores aligned along the jaw. Furthermore, five narrow-simple and interconnected canals were found (i.e. preopercular, mandibular, supraorbital and infraorbital canals). Histologically, the dorsal lateral line presented thin neuromasts (350 μm) with short hair cells. By contrast, the cranial region presented long, thick neuromasts. Infraorbital and mandibular neuromasts had a major axis length of 260 μm and respective average diameters of 200 and 185 μm. Sensory system variations would be due to a greater concentration of neuromasts in the cranial region, allowing for a greater perception of changes in water pressure. Scarce morphological information is available for the lateral sensory system in Eleginopsidae, particularly compared to Channichthyidae, Bovichthydae, Artedidraconidae and Bathydraconidae. Therefore, the presented results form a fundamental foundation of knowledge for the lateral-line system in juvenile E. maclovinus and provide a basis for future related research in this taxon as well as within the Notothenioidei suborder.