Lophiosilurus alexandri: MZUEL , 3, to mm SL, Estação de Piscicultura de Três Marias, CODEVASF, on the upper São Francisco. The “pacamã”, Lophiosilurus alexandri, is a particularly interesting case for addressing this problem. Lophiosilurus alexandri is the largest.
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Conceived and designed the experiments: Pseudopimelodidae are Neotropical catfishes characterized by having slightly to strongly depressed body in fully developed specimens.
The largest species of the family with mm SL, Lophiosilurus alexandriexperiences impressive changes in body shape during development, becoming extremely depressed when fully developed. Accordingly, Lophiosilurus alexandri is an alexaandri species to observe the slexandri changes during ontogeny, and to seek solid interpretations on the polarity of characters.
Changes in body shape, position of mouth and eye, morphology of fins and pigmentation were observed during the development of Lophiosilurus. The greatest morphological changes in the alexaneri of L. 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. The search for the morphological changes that gave rise to the present diversity of forms and taxa continues to be one of the main goals of Evolutionary Biology. Many of these changes can in fact be interpreted as series of transformations of character states with genetic basis and functional expression.
Nevertheless, the phylogenetic significance of these transformation series is unknown for most species of Neotropical fishes. One way to trace a transformation series is to study the ontogeny of a particular species [ 1 ].
The Biogenetic law, proposed by Haeckel [ 2 ] and reformulated by Nelson [ 1 ], says that the steps of an ontogenetic series can be directly translated into an ordered series of character states. That concept, however, has not been accepted among systematists [ 3 ]. Besides these restrictions, Wayne [ 5 ] noted that the morphological diversity of adult forms of dogs and other domesticated animals depends on expressions during ontogeny. According to Lovejoy et al.
Lophiosilurus alexandri is the largest species of the family Pseudopimelodidae, reaching mm standard length [ 7 ] and 4 kg body mass [ 8 ]. This monotypic genus also exhibits the most highly modified morphology for the family.
Its head is extremely depressed, wider than long, the eyes are dorsal, and the mouth is wide and prognathous [ 7 ]. In the phylogeny of Pseudopimelodidae proposed by Shibatta [ 9 ], L. Therefore, given its large size, unique shape, and controversial phylogenetic position, L. Spawning is parceled and the female lays large adhesive eggs 3. Upon hatching, the larvae remain at the bottom of the nest and do not move vertically into the water column.
Due to its excellent flavor and the consistency of its flesh [ 8 ], the species has good potential for intensive aquaculture.
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Previous studies regarding the anatomy of Lophiosilurus alexandri included Nakatani et al. The present study contributes with details on the early development of the external morphology in L.
Individuals were reared from natural spawning of wild adults in flowing water. Juveniles were determined by the complete development of fins and segmentation of fins rays [ 14 ]. A total of specimens were analyzed, including larvae from hatching to 42 days of development 24 yolk sac, 3 flexion and postflexion larvae and 20 juveniles 49 to 60 days Table 1. For each stage of development, specimen illustrations were made with the aid of a camera lucida coupled to a stereomicroscope.
Multiple illustrations were made for stages that exhibited sudden changes in morphology. Twenty-three measurements were obtained on juveniles using a digital caliper accurate to 0. Morphometric variables were expressed as percentages of standard length, except for subunits of the head, expressed as percentages of head length. Measurements of width and depth of body and head were taken on juveniles and adults of other species of Pseudopimelodidae see list of comparative material for comparison.
Meristic data included the number of rays of the pectoral, pelvic, dorsal and anal fins, and total preanal and postanal myomeres. Correlation analyses were carried out using Microsoft Excel, and box plot analysis using Past v. MZUEL3, 7. USNMholotype, AMNH4, AMNH1, ANSP2, IMCN1, Lophiosiulrus1, ANSP1, MCP2, AMNH5, Lophiosilutus1, USNMparatype, 1, MNRJ5, INPA3, From hatching to day 2 of development.
Total number of visible myomeres 38 to 43 14 to 17 preanal and 23 to 26 postanal. Body elongate, transparent, without dark pigmentation. Yolk sac very large immediately after hatching Fig 1adecreasing in volume in specimens one or two days post-hatching Fig 1b. Notochord straight, visible as transparency for entire length.
Eyes small, not pigmented in newly hatched specimens, but pigmented in lophioislurus day old specimens. Alexandti gill opening present within the first day.
Mouth not formed soon after hatching; visible in subterminal position after the first day of development. Buds of maxillary and mentonian barbels present only lkphiosilurus the 1 st day of development. From the second day of development, barbels present. Otic capsule with one semicircular canal visible, and two otholits. Intestine short, anus closed. Primordial fin finfold well developed, hyaline, circling the body from the post-cephalic region to the post yolk sac region.
Stage absent in L.
Stage observed on day 3 of development; standard length 8. Total number of myomeres 40 15 preanal and 25 postanal. Head deep, longer than wide, rounded shape in lateral view. Mouth opened lopjiosilurus incompletely developed. Maxillary and mentonian barbels distinct and short. Nostril, gill opening and axillary gland not formed.
Intestine small, not reaching the middle region of body; anus closed. Notochord visible by transparency with flexion in caudal region.
Primordial dorsal, pectoral, anal and caudal fins with incipient rays. Primordial dorsal fin anterior to middle of body, confluent with dorsal finfold; pectoral-fin bud small, rounded, when adpressed, slightly surpassing vertical through dorsal-fin origin.
Primordial anal fin broadly rounded, visible as thick membrane included within in ventral finfold. Incipient caudal fin wing shaped, visible within confluent portions of dorsal and ventral finfolds; hypurals forming as cartilage. Head and body slightly pigmented with dendritic chromatophores containing dark pigment.
Large yolk sac persistent, unpigmented. Stage observed four to 42 days after hatching. Total myomeres 38 to 41 14 to 15 preanal and 24 to 26 postanal.
Longest stage of larval development with a variety of morphological changes. Large yolk sac persistent on day 4 Fig 2a and 2bmuch reduced at day 9, and completely consumed within the 13 th day of development. In the early stage of postflexion, head deep, with rounded shape in lateral view; depression of head and body starting on day Dorsal region of skull with several ridges on day Mentonian and maxillary barbels larger than in flexion-stage specimens.
Outer mentonian barbels and maxillary barbels do not exceed the gill opening.
Inner mentonian barbel exceeds posterior margin of eye in early stage of postflexion. Gill opening and nostrils formed. Exogenous feeding is possible after day 3 when the mouth opens. Primordial fin well developed in early stage of postflexion, surrounding the entire perimeter of trunk and tail; restricted to posterior regions of adipose and anal fins after day Primordial fin further reduced by day 42, but still confluent with caudal fin. Adipose fin defined after 42 days. Dorsal fin distinct in the early stage of postflexion, and fully developed after day Anal fin well developed on day 8, but still associated with primordial fin; final development of anal fin on day Pectoral fin formation starting on day 7 with emergence of rays; completely developed after day First ray of pectoral fin begins to differentiate on day 6, with small hooks evident along posterior margin; after day 9, hooks visible on both sides with posterior hooks larger than anterior ones Fig 4c.
At 42 days, hooks on anterior and posterior margins of pectoral-fin spine similar in size Fig 5c. Cleithral bulge and posterior cleithral process weakly developed on day 6, and well developed by the end of postflexion stage.
Spurious ray [ 20 ] present at the end of pectoral-fin spine since early in larval development 9 daysand persist in adults.