From genomes to morphology: a view from amphioxus

Holland, P.W.H. 2010. From genomes to morphology: a view from amphioxus. —Acta Zoologica (Stockholm) 91 : 81–86 As complete genome sequences are determined from an ever‐increasing number of animal species, new opportunities are arising for comparative biology. For zoologists interested in the evolution of shape and form, however, there is a problem. The link between genome sequence and morphology is not direct and is obfuscated by complex and evolving genetic pathways, even when conserved regulatory genes are considered. Nonetheless, a large‐scale comparison of genome sequences between extant chordates reveals an intriguing parallel between genotypic and phenotypic evolution. Tunicates have highly altered genomes, with loss of ancestral genes and shuffled genetic arrangements, while vertebrate genomes are also derived through gene loss and genome duplication. The recently sequenced amphioxus genome, in contrast, reveals much greater stasis on the cephalochordate lineage, in parallel to a less derived body plan. The opportunities and challenges for relating genome evolution to morphological evolution are discussed.     

The comparative morphology of the larynx in snakes

Young, B.A. 2000. The comparative morphology of the larynx in snakes. —Acta Zoologica (Stockholm) 81 : 177–193 The larynx and glottal tube were examined in 10 specimens each of 22 snake species. Qualitative analysis through dissection and clearing and staining revealed distinct morphological variation in the cartilage and intrinsic musculature of the larynx. Quantitative analysis of nine morphometric characters revealed laryngeal sexual dimorphism in three species, significant interspecific differences in the coefficients for every morphometric feature regressed on body size, no significant intraspecific differences in the log transformed means, and poor discrimination of species using principal component analysis. The observed variations in laryngeal morphology did not correlate with the phylogeny of the species, or with habitat preferences.     

A new dimension in combining data? The use of morphology and phylogenomic data in metazoan systematics

Giribet, G. 2010. A new dimension in combining data? The use of morphology and phylogenomic data in metazoan systematics. —Acta Zoologica (Stockholm) 91 : 11–19 Animal phylogenies have been traditionally inferred by using the character state information derived from the observation of a diverse array of morphological and anatomical features, but the incorporation of molecular data into the toolkit of phylogenetic characters has shifted drastically the way researchers infer phylogenies. A main reason for this is the ease at which molecular data can be obtained, compared to, e.g., traditional histological and microscopical techniques. Researchers now routinely use genomic data for reconstructing relationships among animal phyla (using whole genomes or Expressed Sequence Tags) but the amount of morphological data available to study the same phylogenetic patterns has not grown accordingly. Given the disparity between the amounts of molecular and morphological data, some authors have questioned entire morphological programs. In this review I discuss issues related to the combinability of genomic and morphological data, the informativeness of each set of characters, and conclude with a discussion of how morphology could be made scalable by utilizing new techniques that allow for non‐intrusive examination of large amounts of preserved museum specimens. Morphology should therefore remains a strong field in evolutionary and comparative biology, as it continues to provide information for inferring phylogenetic patterns, is an important complement for the patterns derived from the molecular data, and it is the common nexus that allows studying fossil taxa with large data sets of molecular data.     

Deconstructing morphology

Scholtz, G. 2010. Deconstructing morphology. —Acta Zoologica (Stockholm) 91 : 44–63 Morphology as the science of form is, in particular, related to the overwhelming diversity of animal forms. Due to its long pre‐Darwinian tradition, organismic morphology is partly burdened by ahistorical typological views. On the other hand, the study of organismic form has always implied concepts of transformation, which helped to pave the way for evolutionary theories. This contradictory history and the fact that we need words to describe organismic form lead in many cases to morphological concepts implying a mixture of structural, functional, developmental, ecological, typological, and evolutionary aspects in current morphological approaches. Because these mixed views lead to contradictory and misleading interpretations of animal form, I stress the need to deconstruct morphological concepts at all levels. I propose a morphology that analyses transformation of animal forms strictly at the structural level in combination with genealogical thinking. Function and other biological aspects of form should be considered in an independent second analytical step. A comparative pattern approach, including developmental patterns, of animal structure in an evolutionary framework allows for the analysis of morphological change, in particular, phylogenetic reconstructions, homology assessment, and the recognition of evolutionary independent morphological units.     

The musculature of Squatinella rostrum (Milne, 1886) (Rotifera: Lepadellidae) as revealed by confocal laser scanning microscopy with additional new data on its trophi and overall morphology

Wilts, E.F., Wulfken, D., Ahlrichs, W.H. and Martínez Arbizu, P. 2012. The musculature of Squatinella rostrum (Milne, 1886) (Rotifera: Lepadellidae) as revealed by confocal laser scanning microscopy with additional new data on its trophi and overall morphology.—Acta Zoologica (Stockholm) 93 : 14–27. The monogonont rotifer Squatinella rostrum was investigated with light, scanning electron and confocal laser scanning microscopy to reveal new morphological data on its inner and outer anatomy. In total, the visualized somatic musculature displays five paired longitudinal muscles (musculi longitudinales I–V) and nine circular muscles (musculi circulares I–IX). Compared to other species, S. rostrum is characterized by the absence of several longitudinal and circular muscles (e.g. musculus longitudinalis capitis, corona sphincter and pars coronalis). A reconstruction of the mastax musculature revealed a total number of seven paired and two unpaired mastax muscles. Possibly homologous somatic and mastax muscles in other, thus far investigated rotifers are discussed. Moreover, we provide a phylogenetic evaluation of the revealed morphological characters and suggest possible autapomorphic characters supporting Squatinella and Lepadellidae. Finally, we refer to some striking similarities in the morphology, ecology and way of movement of Squatinella and Bryceella that may indicate a closer relationship of both taxa.     

Surface morphology of eggs of Euproctis chrysorrhoea (Linnaeus, 1758)

Candan, S., Suludere, Z. and Bayrakdar, F. 2007. Surface morphology of eggs of Euproctis chrysorrhoea (Linnaeus, 1758). —Acta Zoologica (Stockholm) 88 : 000–000. Filaments covering the egg batches and chorion structure were studied both by light and scanning electron microscopy in the brown‐tailed moth Euproctis chrysorrhoea (Linnaeus, 1758). Females lay eggs in masses on the underside of apple leaves. The egg batches are covered with brown hairs derived from the bodies of the female. Each female lays about 200–400 eggs. The spherical eggs are about 0.84 mm long and 0.47 mm wide. Newly deposited eggs are golden‐yellow and darken after the onset of embryonic development. The micropylar area appears somewhat depressed and has a circular outline. The region is surrounded by a rosette of 10–12 petal‐shaped primary cells, which are completely surrounded by a series of secondary and tertiary cells. The remainder of the egg is largely smooth, but shows aeropyles. These are located in the corners of ill‐defined polygons.     

The organisation of invertebrate brains: cells,synapses and circuits

Meinertzhagen, I.A. 2010. The organisation of invertebrate brains: cells, synapses and circuits. —Acta Zoologica (Stockholm) 91 : 64–71 Invertebrate brains are structurally diverse. Neuron numbers range from ～10² to 10⁸ in different groups, compared with larger numbers in vertebrate brains, ～10⁷ to 10¹⁴. The underpopulated brains of invertebrates are noted in their extreme cases for having few cells, and neurons that can be identified from animal to animal, many known in great detail. Although few in number, invertebrate neurons nevertheless comprise many classes. Correlated with the paucity of their number they are sparsely connected, many having ～50 synapses or fewer. Synaptic densities, roughly 1 per μm³ of neuropile, differ little from those for much larger vertebrate neurons. Invertebrate neurons differ from their vertebrate counterparts in the position of their soma, generally in a cortex surrounding the neuropile that consequently occupies a relatively small volume. Their axons typically lack myelin and, supporting a range of conduction velocities, have diameters that differ over a wide range, from 10³ to 10^?1μm. Nerves with thousands of axons differ from neuropile fascicles, which typically have 20 or less. Unlike most vertebrate synapses, but like those of the vertebrate retina, synapses in many invertebrate groups – probably all ecdysozoans and possibly some lophotrochozoans – have synaptic contacts with multiple postsynaptic elements, dyads, triads and so on.     

Leaf morphology and anatomy of Camellia section Camellia (Theaceae)

The delimitations of species in Camellia section Camellia have been disputed for many years, resulting from uncertain relationships among species. Leaf morphological and anatomical characters for 54 species and three varieties in this section were investigated to reveal the relationships. Principal component analysis and cluster analysis were conducted using the transformed data for quantitative and qualitative characters from leaf morphology and anatomy. Combining the results of statistical analysis with comparative leaf characters of morphology and anatomy, we discussed the taxonomic treatment of section Camellia by Chang compared with that of Ming and we conclude that section Camellia consists of c. 50 species. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 159 , 456–476.     

Some developmental aspects of the head skeleton of the 35-37 mm Squalus acanthias foetus

Two specimens of a group of five foetuses, 35–37 mm in total length, of Squalus acanthias were serially sectioned and stained. These specimens were studied for the purpose of testing statements made in the literature, especially by Holmgren ('40), regarding cell sources and skeletal development. Many of Holmgren's results were confirmed with some important differences in detail. Limited blastemas of dermal bones were not evident although a diffuse subepidermal blastema was present in certain areas. There is evidence of delamination addition to the jaws and many parts of the endocranium. Although the trabecula is in part of visceral origin, the visceral material does not represent an infrapharyngohyal since it always has been an integral part of the endocranium, never a formed element of the arch. The same applies to the pharyngo region of the hyoid arch. The pharyngohyal tissue forms the area of articulation of the hyomandibula and the lamina hypotica. Thus a typical lateral commissure is not formed and the resulting otic capsule-basicranial association is unique to the elasmobranchs. The hyomandibula is the epihyal and there is no evidence of a symplectic in this group. The jaws appear to incorporate delamination tissue, associated in teleostomes with dermal bone, in addition to the neural crest proper.     

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.     

A plea for ‘genealogical thinking’ in comparative biology – a rebuttal to the reply of Szucsich,Wirkner, and Pass to my article ‘Deconstructing Morphology’

Scholtz G. in press. A plea for ‘genealogical thinking’ in comparative biology – a rebuttal to the reply of Szucsich, Wirkner, and Pass to my article ‘Deconstructing Morphology’. —Acta Zoologica (Stockholm) 00 : 1–4. Szucsich et al. (in press) claim that – in contrast to my statement – morphological thinking has to be ‘cladistic.’ Based on this premise, they stress the difference between the relationships among states of characters versus those among structures assigned to the same character state as implemented in numerical cladistic reasoning. SEA claim that my approach to the homology concept only deals with the problem of the integration of various character states into the same character, whereas the necessary relationships among structures assigned to the same state are not covered. Based on this distinction, SEA also criticise the application of similarity in my definition of homology. Furthermore, they address the issue of evolutionarily independent units.     

Links between the discovery of primates and anatomical comparisons with humans,the chain of being,our place in nature,and racism

I focus on the crucial links between the discovery of nonhuman primates by Westerners, discussions on our place in nature, the chain of being, racism, and the history of primate comparative anatomy and of so‐called “anatomical human racial studies.” Strikingly, for more than a millennium humans knew more about the internal anatomy of a single monkey species than about that of their own bodies. This is because Galen used monkeys to infer human anatomy, in line with the human‐animal continuity implied by the Greek notion of scala naturae. With the rise of Christianity, nonhuman primates were increasingly seen in a negative way. A more positive view emerged in the 14th century when nonhuman primates were directly studied/seen by Europeans, culminating in Tyson's 1699 work showing that chimps share more gross anatomical similarities with humans than with monkeys. However, the discomfort caused by this human‐chimp similarity then led to a new idea of animal‐human discontinuity, now related not to anatomy but to “civilization”: between Europeans vs. non‐Europeans + other primates. Moreover, Linnaeus' Systema Naturae and the emergence of “anatomical racial studies” influenced by Camper's craniology then led to even more extreme ideas, such as the notion that Europeans were both mentally and morphologically “ideal.” Unfortunately the biased and often incorrect “results” of such studies, combined with ideas based on Darwin's “struggle for survival”, became crucial in propaganda that lead to the rise of eugenics in the end of the 19th/first half of 20th centuries and that culminated in Nazism. Since the 1950s there has been an emphasis on the continuity/unity between all human groups and other primates, in great part influenced by what happened during World War 2. Reviews such as this one are, therefore, particularly necessary to illuminate and guard against attitudes against “the Other” and racist ideologies that are re‐emerging in modern political discourse across the globe.     

Functional morphology of the postpharyngeal gland of queens and workers of the ant Monomorium pharaonis (L.)

Eelen D., Børgesen L.W. and Billen J. 2006. Functional morphology of the postpharyngeal gland of queens and workers of the ant Monomorium pharaonis (L.). —Acta Zoologica (Stockholm) 87 : 101–111 The postpharyngeal gland (PPG) is unique to ants and is the largest exocrine gland in their head. In queens of the pharaoh's ant, Monomorium pharaonis, the gland contains approximately 15 finger‐like epithelial extensions on each side and opens dorsolaterally in the posterior pharynx. In these ants the PPG morphology varies considerably according to age and mating status. The epithelial thickness increases with age and reaches a maximum at 3 weeks in both virgin and mated queens. A considerable expansion of the lumen diameter occurs in both groups between 4 and 7 days. Virgin queens release their secretion into the gland lumen from an age of 7 days, whereas mated queens accumulate large amounts of secretion in their epithelium. The increasing epithelial thickness, together with the increasing lumen diameter, the presence of numerous inclusions in the epithelium and the release of secretion, are indicative for increasing gland activity. The gland ultrastructure indicates involvement in lipid metabolism and de novo synthesis of lipids. The PPG of workers consists of 12 finger‐like tubes at each side. There is a significant difference in epithelial thickness between nurses and repletes and between nurses and foragers. We suggest the PPG serves different purposes in pharaoh's ants: it is likely that the PPG of workers and virgin queens is used to feed larvae. In mated queens the gland probably plays a role in providing the queen with nutritious oils for egg production. The PPG may also function in signalling species nestmate and caste identity, as well as in the reproductive capacity of the queens.     

Bystrow’s Paradox – gills,fossils, and the fish‐to‐tetrapod transition

Schoch, R.R. and Witzmann, F. 2011. Bystrow’s Paradox – gills, fossils, and the fish‐to‐tetrapod transition. —Acta Zoologica (Stockholm) 92 : 251–265. The issue of which breathing mechanism was used by the earliest tetrapods is still unsolved. Recent discoveries of stem tetrapods suggest the presence of internal gills and fish‐like underwater breathing. The same osteological features were used by Bystrow to infer a salamander‐like breathing through external gills in temnospondyl amphibians. This apparent contradiction – here called Bystrow’s Paradox – is resolved by reviewing the primary fossil evidence and the anatomy of the two gill types in extant taxa. Rather unexpectedly, we find that internal gills were present in a range of early crown tetrapods (temnospondyls), based on the anatomy of gill lamellae and location of branchial arteries on the ventral side of gill arch elements (ceratobranchials). Although it remains to be clarified which components are homologous in external and internal gills, both gill types are likely to have been present in Palaeozoic tetrapods – internal gills in aquatic adults of some taxa, and external gills in the larvae of these taxa and in larvae of numerous forms with terrestrial adults, which resorbed the external gills after the larval phase. Future developmental studies will hopefully clarify which mechanistic pathways are involved in gill formation and how these might have evolved.     

The ventral skin glands, new additional cloacal glands in Proteus anguinus (Caudata, Proteidae). I. Female

Guillaume, O. 2000. The ventral skin glands, new additional cloacal glands in Proteus anguinus (Caudata, Proteidae). I. Female. —Acta Zoologica (Stockholm) 81 : 213–221 Cloacae of female Proteus anguinus were examined by light and electron microscopy. Females possess spermathecae and anterior ventral glands such as Necturus females. However, female P. anguinus possess new additional cloacal glands of unknown homology. These tubular glands secrete on the ventral epidermis of the cloacal area. Considering these characteristics, it is proposed that they will be called the ventral skin glands.     

On the head morphology of Phyllium and the phylogenetic relationships of Phasmatodea (Insecta)

Friedemann K., Wipfler B., Bradler S. and Beutel R.G. 2011 . On the head morphology of Phyllium and the phylogenetic relationships of Phasmatodea (Insecta). —Acta Zoologica (Stockholm) 00 : 1–16. External and internal head structures of Phyllium siccifolium are described in detail. The findings are compared with conditions found in other phasmatodeans and members of other neopteran lineages. The compiled 125 characters were analysed cladistically. A clade Eukinolabia (Phasmatodea + Embioptera) was confirmed. Synapomorphies of these two taxa are the shift of the origin of M. tentorioparaglossalis to the hind margin of the prementum, the presence of M. tentorioscapalis medialis, and antennal muscles that originate exclusively on the anterior tentorial arms. Within Eukinolabia, the position of Timema remains somewhat ambiguous because of missing anatomical data. However, it was confirmed as sister group of Euphasmatodea in a monophyletic Phasmatodea. Apomorphic groundplan features of Euphasmatodea are salivary ducts with separate external openings, apically rounded glossae, the presence of the galealobulus, and the reduction of the antennifer. The monophyly of Neophasmatidae was confirmed. Autapomorphies are the loss of M. frontobuccalis posterior, the anteriorly or dorsally directed maxillary palps, and the reduction of the mandibular incisivi. The analysis of characters of the head yielded three new autapomorphies of Phylliinae, the presence of a protuberance on the attachment site of the dorsal tentorial arms, dorsoventrally flattened maxillary‐ and labial palps, and possibly the narrow and U‐shaped field of trichomes on the apical part of the galea.     

The cranial morphology of Kayentachelys,an Early Jurassic cryptodire,and the early history of turtles

Gaffney, E.S. and Jenkins, F.A., Jr. 2010. The cranial morphology of Kayentachelys, an Early Jurassic cryptodire, and the early history of turtles. — Acta Zoologica (Stockholm) 91 : 335–368 The skull morphology of Kayentachelys aprix Gaffney et al., 1987 , a turtle from the Early Jurassic Kayenta Fm of northern Arizona, demonstrates the presence of cryptodiran synapomorphies in agreement with Gaffney et al. (1987, 1991, 2007) , and contrary to the conclusions of Sterli and Joyce (2007) , Joyce (2007) , Sterli (2008) , and Anquetin et al. (2008) . Specific characters found in Kayentachelys and diagnostic of cryptodires include the processus trochlearis oticum, the curved processus pterygoideus externus with a vertical plate, and the prefrontal–vomer contact, which are confirmed as absent in the outgroups, specifically the Late Triassic Proganochelys. The Joyce (2007) analysis suffers from the reduction of the signal from skull characters, with a consequently greater reliance on shell characters, resulting in pleurodires being resolved at various positions within the cryptodires. Kayentachelys reveals what a primitive cryptodire would be expected to look like: a combination of primitive and derived characters, with the fewer derived characters providing the best test of its relationships to other turtles. Although incompletely known, the Mid‐Late Jurassic Condorchelys, Heckeremys, and Eileanchelys may be early cryptodires close to Kayentachelys. We confirm the Late Triassic Proterochersis as a pleurodire, dating the pleurodire–cryptodire split as Late Triassic or earlier.     

The ventral skin glands, new additional cloacal glands in Proteus anguinus (Caudata, Proteidae). II. Male

Guillaume, O. 2000. The ventral skin glands, new additional cloacal glands in Proteus anguinus (Caudata, Proteidae). II. Male. —Acta Zoologica (Stockholm) 81 : 223–234 Cloacae from male Proteus anguinus were examined for the first time by light and electron microscopy. Male P. anguinus possess anterior and posterior ventral glands, dorsal and lateral pelvic glands, vent glands and Kingsbury’s glands as do Necturus males. However, male P. anguinus also possess the new additional cloacal glands found in females and which the author has called the ventral skin glands. Furthermore, the number, the length and the diameter of these tubular glands are higher in males. Therefore the inference is that these glands are sexually dimorphic glands.