Larval development of mandi-pintado Pimelodus britskii (Siluriformes: Pimelodidae)

This study investigated the morphology, morphometric and meristic characters of 117 larval Pimelodus britskii showing early development of head, eye, barbel and snout. Body and mouth pigmentation increased throughout development; the mouth was ventrally situated in the yolk-sac stage, becoming subterminal afterwards, and an embryonic fin was visible in all four stages observed. Post-flexion larval P. bristskii are distinguished from larval P. ortmanni by having 47–50 myomeres (v. 36).     

眼斑双锯鱼仔稚鱼发育异速生长

运用生态学和传统理论生物学的研究方法, 对孵化后眼斑双锯(Amphiprion ocellaris)仔、稚鱼在早期生存和环境适应上的异速生长及器官优先发育生态学意义进行了研究, 以期为眼斑双锯鱼人工繁殖和育苗提供参考资料。以11日龄为眼斑双锯鱼仔、稚鱼的区分时期, 结果表明, 眼斑双锯鱼仔、稚鱼的感觉、摄食和游泳等器官快速分化, 均存在异速生长现象。在头部器官中, 吻长、眼间距、口宽和头高在仔鱼期均为正异速生长, 吻至鳃裂前缘长和眼径为负异速生长。在身体各部位中, 仔鱼期体高、躯干长、尾长、尾柄长、尾柄高和体厚均为正异速生长, 仅头长为负异速生长; 在游泳器官中, 仔鱼期眼斑双锯鱼尾鳍、背鳍、胸鳍、腹鳍和臀鳍均为正异速生长。稚鱼期眼斑双锯鱼头部、躯干及游泳等各器官均为负异速生长。眼斑双锯鱼这些关键器官的异速发育, 对适应环境因子变化具有重要的生态学意义。     

External Morphology of Lophiosilurus alexandri Steindachner, 1876 during Early Stages of Development,and Its Implications for the Evolution of Pseudopimelodidae (Siluriformes)

Pseudopimelodidae are Neotropical catfishes characterized by having slightly to strongly depressed body in fully developed specimens. The largest species of the family with 500 mm SL, Lophiosilurus alexandri, experiences impressive changes in body shape during development, becoming extremely depressed when fully developed. Accordingly, Lophiosilurus alexandri is an ideal species to observe the morphological changes during ontogeny, and to seek solid interpretations on the polarity of characters. Specimens of distinct larval periods (yolk sac, flexion and postflexion; n = 186 specimens) and juvenile stages (n = 20) were analyzed. Changes in body shape, position of mouth and eye, morphology of fins and pigmentation were observed during the development of Lophiosilurus. Larvae (5.7–11.2 mm standard length) had pigmentation concentrated on the head and parts of body, eyes small and pigmented, short barbels, and well-developed finfold. Juveniles (15.9–28.1 mm standard length) had body shape similar to adult, with head depressed and bearing bony ridges, large mouth, dorsally-oriented eyes, small barbels and well-developed shoulder bulges (cleithral width). The greatest morphological changes in the development of L. alexandri occurred during the postflexion larval stage. Relative to standard length, measurements of snout length, head depth and body depth are smaller in juveniles than in larvae, but body width is larger. New interpretations on the phylogenetic characters related to these changes are provided in view of the two alternative hypotheses of the evolution of Pseudopimelodidae.     

Early development and allometric shifts during the ontogeny of a marine catfish (Cathorops spixii‐Ariidae)

This study assessed whether the developmental series of the ariid Cathorops spixii (Agassiz, 1829) is related to growth patterns during its early ontogeny. The main morphological events of C. spixii were studied from the newly neurula embryo (6.99±0.69 mm TL) to juveniles (53.38±14.43 mm TL) in order to characterize and corroborate patterns of ontogenetic allometries. Prior to hatching, embryos were well‐developed, with an ossified axial and appendicular skeleton. Embryos grew slowly, but positive allometric growth was observed in head width (β₁ = 1.65) and eye diameter (β₁ = 1.59). This seems to be related to the fast development of sensory organs such as otoliths, Weberian apparatus, lenses, nostrils and barbels during the embryonic period when eggs are under the care of adult males. After hatching, mouth‐brooding free‐embryos grew horizontally isometric, except for the snout length that presented quick growth related to the end of endogenous feeding (β₁ = 1.73). Slow growth was observed in head width (β₁ = 0.44) and eye diameter (β₁ = 0.26), taking into account that sensory organs are formed in free‐embryos. The end of the yolk‐sac period was characterized by a direct change from free‐embryo to juvenile, without a true larval period. Juveniles are characterized by growth patterns nearly isometric in all body regions, suggesting that they already bear most of characteristics of adult fish. The quick growth of morphometric variables that are related to sensorial organs before hatching and the increase in horizontal growth after the first 6 weeks (hatched free‐embryos) reflect developmental priorities during the earliest stages where important sensorial organs are being developed for juvenile survival strategies.     

Scale formation in selected fundulid and cyprinodontid fishes

Patterns of scale formation (onset, points of origin, completion, and spatial pattern) were examined for six species of killifishes in two families (Cyprinodontidae: Cyprinodon variegatus, and Fundulidae: Fundulus confluentus, F. heteroclitus, F. luciae, F. majalis, and Lucania parva) to determine if the patterns are another useful indicator for the transition from the larval to juvenile periods. In some species, the patterns were very similar, with scale formation originating on/near the caudal peduncle, then the dorsal surface of the head (in fundulids only), and later on the lateral surfaces of the head, and on the ventral surface of the trunk at the level of the pectoral fin. The timing of scale formation, relative to fish size, was later than or overlapped with other morphological characters (e.g., fin ray formation, juvenile/adult body shape) often used to mark the larval/juvenile transition. The onset of scale formation, across all species, occurred between 8 and 13 mm TL. Completion of scale formation occurred between 18 and 23 mm TL. At completion, scales covered 86–99% of the trunk and head. Completion of scale formation in these fishes is one of the last external morphological changes to occur during the larval to juvenile transition. For these species, and other flatfishes we have examined in detail, it appears that scale formation may be useful in helping to define the end of the larval period and the beginning of the juvenile period. Further studies, of divergent groups of teleosts, are necessary to determine if this length-based approach has broad validity.     

Morphological variation in head shape of pipefishes and seahorses in relation to snout length and developmental growth

The feeding apparatus of Syngnathidae, with its elongate tubular snout and tiny, toothless jaws, is highly specialized for performing fast and powerful pivot feeding. In addition, the prolonged syngnathid parental care probably enables the juveniles to be provided with a feeding apparatus that resembles the one in adults, both in morphology and function. In this study, a landmark‐based geometric morphometric analysis was carried out on the head of syngnathid representatives in order to (1) examine to what degree pipefish shape variation is different from that of seahorses; (2) determine whether the high level of specialization reduces the amount of intraspecific morphological variation found within the family; and (3) elucidate whether or not important shape changes occur in the seahorse head during postrelease ontogeny. We found that (1) there is a significant shape difference between head shape of pipefish and seahorse: the main differences concern snout length and height, position and orientation of the pectoral fin base, and height of the head and opercular bone. We hypothesize that this might be related to different prey capture kinematics (long snout with little head rotation versus short snout with large head rotation) and to different body postures (in line with the head versus vertical with a tilted head) in pipefishes and seahorses; (2) both pipefishes and seahorses showed an inverse relation between relative snout length and intraspecific variation and although pipefishes show a large diversity in relative snout elongation, they are more constrained in terms of head shape; and (3) the head of juvenile Hippocampus reidi specimens still undergoes gradual shape changes after being expelled from the brood pouch. Ontogenetic changes include lowering of the snout and head but also differences in orientation of the preopercular bone and lowering of the snout tip. J. Morphol. 2011. © 2011 Wiley‐Liss, Inc.     

Peculiarities of early ontogenesis of the tubenose poacher, <Emphasis Type="Italic">Pallasina barbata</Emphasis> steindachner, 1876 (Pisces,Agonidae) from Peter the Great Bay (Sea of Japan)

Based on the analysis of original material (52 specimens of Pallasina barbata larvae and juveniles), sampled in the Peter the Great Bay (Sea of Japan) from 1992 to 2006, the ontogenetic stages of this species were described for the first time. It is shown that P. barbata has a planktonic larval stage in its development. The major morphologic features that are typical for larvae and juveniles during their development were revealed. It was shown that snout length, head length and pectoral fin size are increased with growth; at the same time body height and eye diameter are decreased, and the nature of larval pigmentation is changed. The main differences between P. barbata and close species are shown. Original illustrations of larvae and juvenile are provided.     

The survival of <Emphasis Type="Italic">Sicyopterus stimpsoni</Emphasis>, an endemic amphidromous Hawaiian gobiid fish,relies on the hydrological cycles of streams: evidence from changes in algal composition of diet through growth stages fish

Gut contents of larval, juvenile, and adult specimens of the Hawaiian gobiid fish Sicyopterus stimpsoni were examined to catalog the algal flora ingested by this species. The developmental stages of S. stimpsoni examined represented hallmark points in the fish’s life cycle corresponding with major migratory and metamorphic transitions. The algal flora was dominated by diatom species and shifted from taxa representative of a marine, planktonic community in larval fish to a freshwater, benthic community in juvenile and adult fish. This change in diet corresponds with the migration of larval fish to freshwater streams just prior to juvenile development in which rapid modification in mouth anatomy makes ingestion of planktonic algal species difficult. Benthic diatoms from juvenile and adult fish assemblages represented multiple genera that live in a narrow set of environmental conditions. These algae grow during a specific period in the development of the benthic algal community in Hawaiian streams. This suggests a highly specialized dietary behavior that depends heavily on continually restarting the benthic algal successional pattern, which appears to be regulated by the hydrological cycles of streams on the island.     

A new sparid, Acanthopagrus akazakii, from New Caledonia with notes on nominal species of Acanthopagrus

A new sparid species, Acanthopagrus akazakii, is described on the basis of 12 types collected from Noumèa, New Caledonia. Acanthopagrus akazakii is most similar to Acanthopagrus berda in overall appearance but differs from the latter in having 4¹/₂ scale rows between the 5th dorsal fin spine base and lateral line, anteriormost head scales broadly rounded without small scales anteriorly, upward- and downward-oriented portions present on anteriormost part of upper lip, a downward-oriented portion on anteriormost part of lower lip in specimens over ca. 160 mm in standard length, and upper head profile gently convex from snout tip to above eye throughout growth (vs. 3¹/₂ scale rows between 5th dorsal fin spine base and lateral line, anteriormost head scales rounded with small scales anteriorly, no upward and downward portions in anteriormost upper and lower lips, and upper head profile becoming concave from snout tip to above eye with growth). Furthermore, A. berda develops a strong concavity of the ventral edge of the first two infraorbitals above the posterior part of upper jaw with growth, whereas A. akazakii has a generally straight series throughout growth. Nominal species in A. berda are reviewed, with notes on nominal species of Acanthopagrus.     

Head‐shape polymorphism in Japanese eels Anguilla japonica in relation to differences of somatic growth in freshwater and brackish habitats

The age, total length (L_T), head shape and skull shape were investigated for 379 Japanese eels Anguilla japonica sampled in freshwater and brackish areas of the Kojima Bay–Asahi River system, Okayama, Japan, to learn about the differentiation process of head‐shape polymorphism. The relative mouth width (ratio of mouth width to L_T) of A. japonica > 400 mm L_T collected in fresh water was significantly greater than that of fish collected in brackish water. Growth rates of mouth width and the distance from the snout to the midpoint of the eyes (the ratio of width and distance to age, respectively) were not significantly different between freshwater and brackish‐water samples, whereas the somatic growth rate (the ratio of L_T to age) of freshwater samples was significantly lower than that of brackish‐water eel samples. These results suggest that the factors affecting head and somatic growth of A. japonica are not identical. According to these results and feeding patterns in each habitat reported by another study, it is suggested that somatic growth appears to play a significant role in the differentiation process of the head‐shape polymorphism in A. japonica, with the slow‐growing fish in fresh water becoming broad‐headed and the fast‐growing fish in brackish water becoming narrow‐headed.     

Growth and morphological development of laboratory-reared larval and juvenile snakeskin gourami Trichogaster pectoralis

Morphological development, including that of fins, labyrinth organ, body proportions, and pigmentation, in laboratory-hatched larval and juvenile snakeskin gourami Trichogaster pectoralis is described. Body lengths (BL; mean ± SD) of larvae and juveniles were 2.3 ± 0.1 mm just after hatching (day 0) and 8.2 ± 0.6 mm on day 22, reaching 14.1 ± 2.3 mm on day 48. Aggregate fin ray numbers attained their full complements in juveniles >11.8 mm BL. Preflexion larvae started feeding on day 2 following upper and lower jaw formation, the yolk being completely absorbed by day 12. Subsequently, oblong conical teeth appeared in postflexion larvae >8.2 mm BL (day 16). Melanophores on the body increased with growth, with a large dark spot developing on the lateral midline at the caudal margin of the body in flexion larvae >6.1 mm BL. Subsequently, a broad vertical dark band from the eye to the caudal peduncle developed in postflexion larvae >8.9 mm BL. Proportions of head and pre-anal lengths became constant in postflexion larvae greater than ca. 9–10 mm BL, whereas those of maximum body depth, eye diameter, and snout length failed to stabilize in fish of the size examined in this study. First soft fin ray of the pelvic fin elongated, reaching over 40% BL. The labyrinth organ differentiated in postflexion larvae >7.4 mm BL (day 22). Comparisons of larval and juvenile morphology with another anabantoid species Anabas testudineus were also made, revealing several distinct differences, particularly in the numbers of myomeres and fin rays in the dorsal/anal fins, mouth location and body shape.     

Developmental morphology of the cyprinid fish, Candidia barbatus

 Embryonic, larval, and juvenile development of a Taiwanese cyprinid fish, Candidia barbatus, is described from laboratory-reared specimens. The eggs, measuring 1.8–2.1 mm in diameter, were demersal, almost spherical in shape, transparent and unpigmented, with a pale yellow yolk and no oil globule. Hatching occurred 56–69 h after fertilization, the newly hatched larvae measuring 4.9–5.3 mm in body length (BL) with 25–26 + 13–14 = 39–40 myomeres. The yolk was completely absorbed at 7.6 mm BL. Notochord flexion was initiated at 6.8 mm BL and finished at 7.6 mm BL. Aggregate numbers of all fin rays were completed at 12 mm BL. Barbels on the upper jaw appeared near the corner of the mouth at 17 mm BL. Eggs of the species closely resembled those of its related cyprinid genera, Opsariichthys and Zacco. Larvae and juveniles of C. barbatus were similar to those of O. uncirostris subspp., Z. platypus, and Z. pachycephalus, but differed from the latter in the process of disappearance of the adipose finfold (postflexion larval stage), barbels on upper jaw (juvenile stage), and pigmentation on the lateral body surface (postflexion larval and juvenile stages). Although C. barbatus also differed from the Z. temminckii species' group [Z. temminckii and Zacco sp. (sensu Hosoya, 2002)] in having barbels, larvae and juveniles of the former showed more similarity to the latter species group than to O. uncirostris subspp., Z. platypus, and Z. pachycephalus, from the aspect of head and body pigmentation.     

Leptonotus vincentae,a new pipefish species (Syngnathidae: Syngnathinae) from the south-west Atlantic Ocean near northern Patagonia

A new species of pipefish Leptonotus vincentae sp. nov. (Syngnathidae) is described on the basis of 12 specimens found in shallow waters (<2 m depth) of San Antonio Bay, Patagonia, Argentina, in the south-west Atlantic Ocean. The species is distinguished from congeners by the combination of: dorsal-fin rays 30–33, pectoral-fin rays 12–13, trunk rings 18–19, tail rings 43–46, subdorsal rings (2–4) + (5.5–8) = (8.5–10), head length 13–14% standard length, snout length 35–55% head length and snout depth 21–30% in snout length. Although this species has often been mistaken for Leptonotus blainvilleanus, most diagnostic characters of the two species differ. Both species are clearly distinguished by their snout length. L. blainvilleanus has a relatively longer snout than L. vincentae sp. nov. The new species is similar to a south-west Pacific species, Leptonotus elevatus. However, L. vincentae sp. nov. differs from this species in that it exhibits a lower number of dorsal-fin rays and a relatively longer head.     

<Emphasis Type="Italic">Metzia longinasus</Emphasis>, a new cyprinid species (Teleostei: Cypriniformes) from the Pearl River drainage in Guangxi Province,South China

Metzia longinasus, a new cultrine cyprinid species from the Hongshui-He River of the Pearl River drainage in Guangxi Province, southern China, is described here. It can be distinguished from all other congeners by having a combination of the following characters: a superior mouth, 43 or 44 lateral-line scales, a long head (length 27.2–30.8% of standard length), a long snout (length 31.7–37.0% of head length), 10 or 11 branched anal-fin rays, and no longitudinal black band extending along each side of body from the extremity of the gill opening to caudal-fin base.     

<Emphasis Type="Italic">Paraliparis adustus</Emphasis> and <Emphasis Type="Italic">Paraliparis bullacephalus</Emphasis>: two new snailfish species (Teleostei: Liparidae) from Alaska

Paraliparis adustus sp. nov., a snailfish species from the Bering Sea near the Aleutian Island Archipelago, Alaska, is described based on a single mesopelagic specimen. This new species is clearly distinguished by a combination of several morphological features and meristic counts, including long pointed gill rakers with 0–3 spinules at or near the tip, anus positioned forward near the pectoral symphysis, and color uniform brown. Paraliparis bullacephalus sp. nov. from Shelikof Strait, Gulf of Alaska, is also described. This new species is very similar in meristic characters and general body shape and size to P. holomelas Gilbert, but differs primarily in morphological features of the head, particularly in the shape of the dorsal contour of the head, snout, and opercular flap, mouth size, and eye position.     

Early development of the Neotropical fish known as long sardine Triportheus auritus (Valenciennes 1850) (Characiformes,Triportheidae)

Larvae and juveniles of long sardine, Triportheus auritus, from the lower Amazon river was described, evaluating ontogenetic changes in their external mor­phology, pigmentation, fin development, morphometry, and meristics. A total of 93 individuals, 83 larvae and 10 juveniles were analyzed, they were captured monthly between 2014 and 2019 in the Amazon river channel and in macrophytes aquatic stands in the alluvial plains located in the lower Amazon River. From each specimen, morphometric and meristic data were measured and then the growth pattern between morphometric variables was analyzed. The larvae have an elongated body in a fusiform shape, superior mouth, simple nostril, pigmented spherical eyes and long intestine, surpassing the median region of the body. Initial pigmentation is scarce, but intensifies through development forming a pattern composed of three longitudinal bands concentrated in the ventral, cephalo-dorsal and lateral line regions. There are also pigments in the mandible, surrounding the mouth, under the swim bladder, intestine and fins. The sequence of complete fin formation is: caudal, anal, dorsal, pectoral and pelvic. The total number of myomeres ranged from 45 to 48 (25–29 preanal and 17–22 postanal). Morphometric relationships indicated differential growth for measurable morphometric parameters, with abrupt growth of snout length, head length and body height in the transition from flexion to postflexion stages. The pre-dorsal distance showed a decrease in the growth rate at the threshold from the larval to the juvenile period. The pre-pectoral and pre-anal distances showed negative allometric growth. In conclusion, the combination of body shape pigmentation pattern and, the formation sequence of fins allow the identification of the genus and coupled with the number of myomeres, morphometric relationships, and ray numbers of the anal fin ensure the differentiation of T. auritus from the other congeneric species. The metamorphosis occurred mainly at the end of the larval period and it is related to changes in the physiological and ecomorphological characteristics of the species.     

Morphological studies on the mouth cavity of Urodela IX. Teeth of the palate and the splenials in Siren and Pseudobranchus (Sirenidae: Amphibia)

1. Dentition, tooth structure and course of dental laminae of adult and subadult Sirenidae (Siren intermedia, S. lacertina, Pseudobranchus striatus) have been studied by light microscopy and scanning electron microscopy. 2. Splenials, vomers und palatines bear monocuspid unbladed teeth, arranged in a polystichous pattern, whereas praemaxillaries and maxillaries (so far as present) are edentate. Teeth in S. intermedia show a rough basis, which is more prominent in S. lacertina and which has break-throughs in P. striatus. This zone perhaps is homologous to a developing dividing zone typical for teeth in many “Lissamphibia”. 3. With respect to structure and organisation of dentigerous bones and teeth Sirenidae obviously possess a mosaicism of differently developed larval characters in their mouth cavity. 4. The dentition in the recent forms investigated is compared to that of other paedomorphic Urodela und the ancient Habrosaurus dilatus (Sirenidae).     

Ultrastructure aspects of Brycon gouldingi (Teleostei,Characidae) related to swimming ability and feeding during larval development

The larval ultrastructure of Brycon gouldingi related to swimming and feeding from hatching to total yolk absorption is described from scanning electron micrographs. Newly hatched larvae (time zero) had no mouth opening, undefined optic vesicles, an olfactory plate visible as a shallow depression, rudimentary gill arches, neural groove, embryonic fin and a primary neuromast in the dorsal region of the head. At the time of yolk absorption, 55 h post hatching, the larvae presented an optic vesicle comprising an optic cup and crystalline lens; a mouth with tongue, tapered teeth and taste buds; a ciliated olfactory cavity; branched gill arches; filled neural groove signalling central nervous system development; caudal, pectoral, dorsal and anal fins; and neuromasts distributed throughout the head and body. These characters are related to prey capture and swimming ability, key aspects of survival during the larval stage. The results of this study provide important information for exploitation and aquaculture of B. gouldingi.     

Morphogenetic and physiological effects of a juvenile hormone analogue on the light brown apple moth,Epiphyas postvittana (Lepidoptera: Tortricidae)

Abstract

The juvenile hormone analogue ZR-619—ethyl 11-methoxy-3,7,11-trimethyl-(2E,4E-dodecadienethiolate) —produced morphological and physiological effects when fed via artificial diet to larvae of Epiphyas postvittana (Walker). Morphological effects included changes in larval head and antennal structures after instar V (supernumerary instars); deformation of pupal and adult structures, particularly in genitalia and wings; and development of individuals with varying mixtures of larval and pupal structures. Physiological effects included prolongation of larval life, increase in larval weight, increase in larval instars, and decrease in fecundity. Effects were directly related to dosage concentrations.