Alternative life histories of the genusLucania: 3. An ecomorphological explanation of altricial (L. parva) and precocial (L. goodei) species

Synopsis Important differences were observed in the early ontogenies ofLucania parva andLucania goodei. These differences can be explained in terms of the altricial-precocial model of speciation.Lucania parva can be recognized as an altricial form that produces many eggs with relatively little yolk investment, compared to the more precocialL. goodei. Many of the differences observed in embryo, larva and juvenile specimens appear to be related to these differences in gamete investment. Accelerated developmental rates in the precocial form suggest that paedomorphosis is an important proximate mechanism in the bifurcation of alternative life-history styles in this genus. Some morphological characteristics, such as vitelline circulation and body shape, may be transformations associated with the particular environmental conditions in which the animals must develop and survive. Our observations suggest that these two species in the genusLucania have followed different ontogenic trajectories in response to prevailing environmental conditions.     

A Mathematical Technique for Estimating Blastodisc:Yolk Volume Ratios instead of Egg Sizes

Egg size alone is a poor and misleading variable in life-history studies. A mathematical technique for estimating yolk and blastodisc volume ratios in fishes, a much more meaningful character, is generated from first principles. The technique is demonstrated with an example of early ontogeny in fishes of the genus Lucania (Pisces: Cyprinodontidae). Wild, adult rainwater killifish, Lucania parva, and bluefin killifish, L. goodei, were collected in Florida and transported to the laboratory, where offspring were reared under controlled conditions. Offspring were sampled at the onset of cleavage, for simple measurements of yolk and blastodisc morphology. Application of mathematical equations allowed estimates of yolk and blastodisc volumes in the two species. No significant differences were found in clutch size, blastodisc volume, or egg density; however, significant differences existed in the absolute yolk investments, and blastodisc:yolk volume ratios. These differences in reproductive investment within the genus Lucania are interpreted by the altricial-precocial life-history model as a possible causal mechanism in the evolution of species within this genus. The mathematical equations presented in this study enabled us to partition reproductive investment into components that are more biologically meaningful than simple egg size.     

Ontogeny of the eodiscoid trilobite Tsunyidiscus acutus from the Lower Cambrian of South China

Abstract: The morphology and ontogeny of the eodiscid trilobite Tsunyidiscus acutus Sun is described on the basis of numerous calcified specimens collected from the Lower Cambrian Shuijingtuo Formation in Yichang and Changyang, Hubei Province, South China. An ontogenetic series is established based on the articulated material including the previously unknown protaspides and meraspides (degrees 0 and 1). The material, revealing some prominent morphological changes such as the number of pygidial axial rings, genal spines retained throughout ontogeny and pygidial pleurae from furrowed to unfurrowed, enables a discussion on the trunk segmentation schedule, indicating that somitogenesis and tagmosis occurred independently during the ontogenetic development of T. acutus.     

Ontogenetic pattern,morphological sexual and side dimorphism in the saccular otolith of a scaleless killifish Aphanius furcatus (Teleostei: Aphaniidae)

The relationships between ontogenetic and sexual factors with otolith morphology are poorly studied in killifish genus Aphanius Nardo, 1827. We studied the ontogeny, morphological sexual and side dimorphism in the saccular otolith of a scaleless killifish Aphanius furcatus inhabiting a high‐salinity environment in Southern Iran. The results highlighted growth‐dependent variability in the otolith of A. furcatus, which might be useful to define its certain developmental stages. We underlined those characters that were consistent during fish development, which could be valuable to identify the species. Considering the ontogenetic pattern of otolith in A. furcatus, it was found that the otoliths of young individuals have largely been influenced by sexes and that it was reduced during the fish development. Morphological side dimorphism in the otolith of A. furcatus tends to be increased during fish development. The outcomes of this study are essential since they have provided new information on ontogenetic changes and the sexual and side dimorphism of Aphanius otolith.     

New polymorphic microsatellite loci in two fish species: bluefin killifish (Lucania goodei) and yellow bullhead (Ameiurus natalis)

We identified four new polymorphic microsatellite loci in bluefin killifish (Lucania goodei) and five loci in yellow bullheads (Ameiurus natalis). We screened 400 killifish from 20 populations and 180 bullheads from nine populations, finding a high degree of polymorphism (nine to 54 alleles per locus; average expected heterozygosity 0.678–0.976). We found no evidence for linkage disequilibrium. Three of the loci found in bluefin killifish show heterozygote deficiency; the other loci do not deviate from Hardy–Weinberg expectations.     

Features of Transition from Larva to Juvenile in Fishes with Different Types of Early Ontogeny

The transition from the larva state to the juvenile state (i.e. morphological condition characterised by mainly adult characters) was examined in three marine fish species: herring Clupea pallasi marisalbi, wolffish Anarhichas lupus, and eelpout Zoarces viviparus, based on external morphology and skeletal development. In spite of the different reproductive styles (oviparity, facultative viviparity, and obligate viviparity, respectively) and different types of early ontogeny (indirect, transitory, and direct, respectively), the beginning of the juvenile state occurred at similar total lengths (TL), which were approximated as 35 mm TL in herring and eelpout, and 32 mm TL in wolffish. Features of ontogeny were compared, assuming that the beginning of the juvenile state represented an uniform characteristic of morphological development for these species. It was proposed that the beginning of the larva or juvenile periods (sensu Balon) could not coincide with the beginning of the larva and juvenile states in the ontogeny of some species.     

Enrolment and trunk segmentation of a Cambrian eodiscoid trilobite

Completely enrolled, phosphatized, 3‐D specimens of the eodiscinid trilobite Tsunyidiscus yanjiazhaiensis from Cambrian Stage 3 of South China exhibit much morphological detail and show variation in delicate coaptative structures associated with their trunk segmentation. The relationship between enrolment mechanism and trunk segmentation during ontogeny confirms a unique developmental pattern among the early Cambrian eodiscoid trilobites, revealing how these animals controlled the rate of segment increase and release during post‐embryonic development in their life cycles.     

Ontogeny of the Upper Cambrian (Furongian) Olenid trilobite Protopeltura aciculate (Angelin, 1854) from Skåne and Västergötland,Sweden

Abstract: The ontogeny of the trilobite Protopeltura aciculata (Angelin, 1854) is described on the basis of material from the upper Cambrian (Furongian) of Andrarum (Skåne) and Hjelmsäter (Västergötland), Sweden. P. aciculata is present in the Parabolina brevispina and Parabolina spinulosa zones. Protopeltura aciculata is represented by all stages of growth, from early protaspides to holaspides, although most of the specimens are disarticulated and precise degrees are unknown. The cranidia have therefore been allocated to five morphological groups. Cuticular sculpture of the cranidia changes throughout ontogeny. Large tubercles are present in earlier stages, disappear gradually in middle meraspid stages and are replaced with a very faint granulation. The transitory pygidium, relatively large and shield‐shaped with upwardly and backwardly directed marginal spines in early meraspides, later becomes very small, triangular‐shaped and lacking spines as a late meraspid and holaspid. The development of hypostomes and librigenae is also described. Protopeltura aciculata shows major intraspecific variations throughout development, especially regarding the pygidium where variation is much less constrained than in many other olenids. This high developmental plasticity may be a survival strategy for a trilobite living in a stressed environment. Protopeltura inhabited a dysoxic environment, possibly unusually prone to localised spreading of anoxic or toxic water. Some morphs may have been less vulnerable than others to such stresses, surviving by chance and thus enabling the species to continue.     

Early development and allometric growth in the armoured catfish <Emphasis Type="Italic">Corydoras aeneus</Emphasis> (Gill, 1858)

An ontogenetic series of in-captivity bred Corydoras aeneus was used, in order to study the developmental changes in the external morphology. Allometric growth of several body parts was studied, attempting to reveal important steps in the species’ early life history. Based on the external morphology, the different stages during early development of C. aeneus were identified, according to Balon (Journal of the Fisheries Research Board of Canada 32:1663–1670, 1975). After hatching, at a SL of 3.5 mm, the developmental state corresponded to an eleutherembryonic phase, followed by the protopterygiolarval phase (4.4–5.7 mm SL), the pterygiolarval phase (5.7–14.0 mm SL) and the juvenile period. In addition, an overall growth curve and inflexion points were determined. As such, ontogenetic changes in growth coefficients k (in SL = b age ^k ) were determined. Log transformed data were used for a piecewise linear regression method, as per regression spline smoothing procedures. This way, the growth curve could be divided into six different intervals of growth rate. Initially, the slope was 0.05 until 0.7 dph, then increasing to 0.18 until 4 dph, and 0.36 until 10 dph. After this, growth rate reached a maximum of 0.76 until 24 dph, slowed down to 0.47 until 37 dph and then finally again slowed down to 0.36. A similar growth analysis was also done on the different body parts and these results were compared to both morphological and data from literature. This led to the conclusion that the inflexion points found during the early development of C. aeneus matched the different key-events known in teleost early life history and development. The transition from endo- to exogenous feeding, at the moment a functional branchial respiratory system becomes increasingly important, was the first point at which allometries changed together with functional demands. A second, similar congruence occurred at the transition to the pterygiolarval phase, when priorities shift towards locomotory needs. Finally, our results also indicated a transition to a carangiform swimming mode at approximately 8 mm SL. Handling editor: K. Martens     

Reproductive biology,growth and age composition of the introducedOreochromis mossambicus (Cichlidae) in two reservoirs,Brisbane, Australia

Synopsis The reproductive biology, growth and age composition ofOreochromis mossambicus (Peters) were studied in two Brisbane reservoirs during 1981–1983. The life history was assessed in terms of altricial and precocial tendencies after Noakes & Balon (1982). Fish from both reservoirs had a precocial life history style, showing delayed maturation at 12–15 months, at minimum sizes of 152 mm standard length in males and 174 mm standard length in females. The minimum size of fish at maturity was 0.51–0.73 of maximum size. Mean fecundity was 1360 (± 117.2 standard error) in North Pine Dam and 2107 (220.4 standard error) in Tingalpa Reservoir. This difference was significant (p<0.01). Oöcyte diameter ranged from 1.7–2.6 mm. Overall sex ratio was 1:1 but males predominated amongst fish larger than 200 mm standard length. Stocks consisted mainly of three age groups and the oldest fish caught were 3+ years old. Growth rates were high in both populations. Length-weight relationships conformed to the allometric formula W = aLⁿ and were consistent with data on growth rates. High growth rates are attributed to the high productivity of both reservoirs and the small size of the populations relative to food resources, which are not utilized directly by other fishes. These factors probably also account for the precocial life history style exhibited, compared to the altricial life history style ofO. mossambicus in Lake Sibaya, South Africa, a food-restricted environment.     

Comparative post-hatching ontogeny of Pseudoplatystoma reticulatum (Eigenmann & Eigenmann 1889) and Leiarius marmoratus (Gill, 1870) and their hybrid

Ontogenetic studies of the eggs and larvae of fish can provide information on the initial life history and biology of a species, are important for taxonomic and evolutionary studies, and for cultivation in captivity. The aim of this study was to analyze and describe the main morphological differences in the larval ontogeny of Pseudoplatystoma reticulatum, Leiarius marmoratus, and its hybrid (♀ P. reticulatum × ♂ L. marmoratus), as well as to identify characteristics that can identify the species and their hybrid at the larvae and juvenile stages. 205 L. marmoratus, 210 P. reticulatum, and 205 hybrid specimens were analyzed, all of which were obtained through induced reproduction. Analyses were performed from hatching to 30 days post-hatching. 19 morphometric and 5 meristic characteristics were evaluated, in addition to chromatophore shape and distribution. The specimens were classified into two life periods: Larval (stages: yolk sac, pre-flexion, flexion, and post-flexion) and Juvenile. Newly hatched larvae were transparent, poorly developed, and had a scarcity of chromatophores. During the early stages of larval development, the three groups showed similarities in appearance and proportional dimensions. However, at both the end of the post-flexion stage and at the juvenile period when individuals were approximately 2 cm long, it was possible to differentiate between hybrids and their parental species by their morphometric, meristic, and pigment characteristics. The hybrid, despite occupying an intermediate position in relationship to its parents, exhibited a shape and size more similar to P. reticulatum, its maternal parent.     

Morphogenesis, Dictyostelium, and the search for shared developmental processes

In the 1930s John Tyler Bonner began studying the slime mold, Dictyostelium discoideum, as a way to investigate how organisms develop. With a life cycle that includes periods of unicellularity and multicellularity, Dictyostelium raises questions fundamental to development and evolution. In Morphogenesis: An Essay on Development (1952), Bonner built on his work with Dictyostelium to inform developmental theory and practice. By exploring how Bonner’s early work with Dictyostelium motivated his synthetic approach in Morphogenesis, this paper presents an example of how those who studied development sought ways to gain traction in the rapidly changing life sciences. While a biochemical viewpoint of development became dominant, morphogenesis provided a way to reintroduce and emphasize biological organization at the organismal level. Bonner’s early work offers a window to mid-twentieth century studies of development, an understudied area in the history of science, and shows that it was a time when growing experimental evidence enabled new ways of thinking about the relationship between ontogeny and evolution, and more broadly, about how the parts of nature might fit together.     

Ontogeny of the Massospondylus labyrinth: implications for locomotory shifts in a basal sauropodomorph dinosaur

Ontogeny is a vital aspect of life history sometimes overlooked in palaeontological studies. However, the changing geometry of anatomical structures during growth can be informative regarding ecological and functional reconstructions. The inner ear, or labyrinth, is an ideal ontogenetic study system because it has a strong functional signal in its morphology that is linked to locomotor mode. Yet almost nothing is known about labyrinth development in dinosaurs. We quantified labyrinth scale and geometry through ontogeny in the Early Jurassic dinosaur Massospondylus carinatus, which has an exceptional fossil record and is hypothesized to have undergone a gait change, from quadrupedal juvenile to bipedal adult. To test whether this putative locomotor shift is reflected in labyrinth morphology, computed microtomography (μCT) and propagation phase‐contrast synchrotron radiation microtomography (PPC‐SRμCT) were used to obtain labyrinths from eight specimens, ranging from near‐hatchling to adult. Labyrinths grow substantially but scale with slight negative allometry compared to skull length throughout ontogeny, the first time this has been documented in dinosaurs. Geometric morphometric analysis of the labyrinth using a sliding semilandmark approach shows some morphological change through ontogeny, but little evidence supporting a locomotor shift. These results have implications for our understanding of sauropodomorph development and provide a better understanding of dinosaur locomotory evolution.     

Effects of temperature and diet on oviposition rate and development time of the New Zealand flower thrips, Thrips obscuratus

The life history of New Zealand flower thrips (Thrips obscuratus (Crawford), Thysanoptera: Thripidae) was studied using a simple laboratory rearing method. The effects of temperature and diet on oviposition rate and development time were examined. Oviposition rate increased with increasing temperature between 10°C and 25°C. Development time for individual instars and for total development decreased with increasing temperature between 10°C and 27°C. Total development time ranged from 50 days at 10°C (female) to 10 days at 27°C (male). The relationship between temperature and development rate was expressed as a straight line such that lower thresholds of development of between 4.2°C and 6.3°C were established for life stages. Adult lifespan increased with decreasing temperature between 10°C and 25°C and females lived longer than males. At 10°C and 25°C females lived for an average of 34 and 3 weeks respectively. Thrips supplied with pollen exhibited highest and sustained levels of egg production in comparison to other diets. Larval mortality was lowest and development time fastest on diets of pollen and sucrose or fruit juice in comparison to other plant tissues. Larval development time was similar on four species of pollen.     

中国兰科独蒜兰属植物增补

报道了中国兰科独蒜兰属2个未详知种:藏南独蒜兰(Pleione arunachalensis Hareesh, P.Kumar M.Sabu)和矮小独蒜兰[P.humilis (Sm.) D.Don],并提供了详细的形态描述和照片。凭证标本保存于云南省林业和草原科学院植物标本馆(YAF)。     

亚沉茶渍亚洲亚种Lecanora subimmersa subsp.asiatica Zahlbr.的订正研究北大核心CSCD

亚沉茶渍亚洲亚种Lecanora subimmersa subsp.asiatica Zahlbr.曾被基于文献研究转隶至平茶渍属(Aspicilia)或处理为亚沉茶渍原亚种L.subimmersa(Fée)Vain.subsp.subimmersa的异名,但模式标本的研究缺乏仍使该变种的概念不清。利用形态学、解剖学和化学等方法对L.subimmersa subsp.asiatica Zahlbr.的模式标本进行了综合研究,发现L.subimmersa subsp.asiatica与滇茶渍[L.oreinoides(Körb.)Hertel&Rambold]的形态特征及次生代谢产物一致,故将L.subimmersa subsp.asiatica作为L.oreinoides的异名处理。依据研究标本,对滇茶渍进行了形态学描述,同时提供了相关形态学图片,澄清了亚沉茶渍亚洲亚种的概念。     

Mesoptychia chinensis Bakalin,Vilnet & Xiong sp. nov. (Jungermanniaceae,Marchantiophyta) and comments on the distribution of Mesoptychia south of the boreal zone in Asia

Abstract

Morphologically unique specimens of Mesoptychia (Lindb.) A.Evans recently collected in Guizhou Province, China were sequenced and analysed using a combined trnL-F+trnG-intron cpDNA dataset from 10 known taxa of Mesoptychia. Using a combination of morphological and molecular data, Mesoptychia chinensis Bakalin, Vilnet & Xiong sp. nov. is described as new to science. Mesoptychia polymorpha subsp. pakistanica Bakalin & Vilnet subsp. nov. is established based on morphological data only. Mesoptychia ussuriensis is newly recorded for China. New molecular data for species delimitation within Mesoptychia distributed in southern and south-east Asia are provided.