Development of the muscular and nervous systems during the larval ontogeny of the stalked barnacle, Octolasmis angulata Aurivillius 1894 (Cirripedia: Thoracicalcerea: Poecilasmatidae).

The advancements in microscopic techniques have stimulated great interest in the muscular and neural architectures of invertebrates, specifically using muscle and neural structures to infer phylogenetic relationships. Here, we provide the data on the development of the muscular and nervous systems during the larval development of stalked barnacle, Octolasmis angulata using the phalloidin F-actin and immunohistochemical labelling (e.g. acetylated α-tubulin and serotonin) and confocal laser scanning microscopy analysis. All naupliar stages shared the same muscle and neural architectures with only the discrepancy in size. The nauplii have a complex muscle arrangement in their feeding apparatus and naupliar appendages. Most naupliar muscles undergo histolyse during the cyprid metamorphosis. The cyprid muscles form beneath the head shield at the end of nauplius VI. The naupliar and cyprid central nervous systems exhibit the typical tripartite brain comprising the protocerebrum, deutocerebrum and tritocerebrum. The serotonin-like immunoreactivity is mainly found in the naupliar brain, mandibular ganglia, cyprid brain and posterior ganglia. Our study revealed that numerous muscle and neural architectures in the naupliar and cyprids have phylogenetic significance, but future studies on the myoanatomy and neuroanatomy of other barnacle species are necessary to determine the homology of these structures.

First evidence for temporary and permanent adhesive systems in the stalked barnacle cyprid, Octolasmis angulata.

Although there have been extensive studies on the larval adhesion of acorn barnacles over the past few decades, little is known about stalked barnacles. For the first time, we describe the larval adhesive systems in the stalked barnacle, Octolasmis angulata and the findings differ from previous reports of the temporary (antennulary) and cement glands in thoracican barnacles. We have found that the temporary adhesives of cyprid are produced by the clustered temporary adhesive glands located within the mantle, instead of the specialised hypodermal glands in the second antennular segment as reported in the acorn barnacles. The temporary adhesive secretory vesicles (TASV) are released from the gland cells into the antennule via the neck extensions of the glands, and surrounded with microtubules in the attachment disc. Cement glands undergo a morphological transition as the cyprid grows. Synthesis of the permanent adhesives only occurs during the early cyprid stage, and is terminated once the cement glands reach maximum size. Evidence of the epithelial invaginations on the cement glands supports the involvement of exocytosis in the secretion of the permanent adhesives. This study provides new insight into the larval adhesives system of thoracican barnacles.

Monogenean anchor morphometry: systematic value, phylogenetic signal, and evolution.

Background. Anchors are one of the important attachment appendages for monogenean parasites. Common descent and evolutionary processes have left their mark on anchor morphometry, in the form of patterns of shape and size variation useful for systematic and evolutionary studies. When combined with morphological and molecular data, analysis of anchor morphometry can potentially answer a wide range of biological questions. Materials and Methods. We used data from anchor morphometry, body size and morphology of 13 Ligophorus (Monogenea: Ancyrocephalidae) species infecting two marine mugilid (Teleostei: Mugilidae) fish hosts: Moolgarda buchanani (Bleeker) and Liza subviridis (Valenciennes) from Malaysia. Anchor shape and size data (n = 530) were generated using methods of geometric morphometrics. We used 28S rRNA, 18S rRNA, and ITS1 sequence data to infer a maximum likelihood phylogeny. We discriminated species using principal component and cluster analysis of shape data. Adams's K mult was used to detect phylogenetic signal in anchor shape. Phylogeny-correlated size and shape changes were investigated using continuous character mapping and directional statistics, respectively. We assessed morphological constraints in anchor morphometry using phylogenetic regression of anchor shape against body size and anchor size. Anchor morphological integration was studied using partial least squares method. The association between copulatory organ morphology and anchor shape and size in phylomorphospace was used to test the Rohde-Hobbs hypothesis. We created monogeneaGM, a new R package that integrates analyses of monogenean anchor geometric morphometric data with morphological and phylogenetic data. Results. We discriminated 12 of the 13 Ligophorus species using anchor shape data. Significant phylogenetic signal was detected in anchor shape. Thus, we discovered new morphological characters based on anchor shaft shape, the length between the inner root point and the outer root point, and the length between the inner root point and the dent point. The species on M. buchanani evolved larger, more robust anchors; those on L. subviridis evolved smaller, more delicate anchors. Anchor shape and size were significantly correlated, suggesting constraints in anchor evolution. Tight integration between the root and the point compartments within anchors confirms the anchor as a single, fully integrated module. The correlation between male copulatory organ morphology and size with anchor shape was consistent with predictions from the Rohde-Hobbs hypothesis. Conclusions. Monogenean anchors are tightly integrated structures, and their shape variation correlates strongly with phylogeny, thus underscoring their value for systematic and evolutionary biology studies. Our MonogeneaGM R package provides tools for researchers to mine biological insights from geometric morphometric data of speciose monogenean genera.

Ultrastructure of head organs (anterior adhesive apparatus) and posterior secretory systems of Caballeria liewi Lim, 1995 (Monogenea, Ancyrocephalidae).

Caballeria liewi Lim, 1995, uses adhesive secretions from the head organs and posterior secretory systems to assist in locomotion and attachment. Ultrastructural investigations show that the head organs of C. liewi consist of three pairs of antero-lateral pit-like openings bearing microvilli and ducts leading from two types of uninucleated gland cells (located lateral to the pharynx), one type producing rod-like (S1) bodies with an electron-dense matrix containing less electron-dense vesicles and the second type producing oval (S2) bodies with a homogeneous electron-dense matrix. Interlinking band-like structures are observed between S1 bodies and between S2 bodies. S1 body is synthesised in the granular endoplasmic reticulum, transported to a Golgi complex to be packaged into vesicles and routed into ducts for exudation. The synthesis of the S2 body is unresolved. Haptoral secretions manifested externally as net-like structures are derived from dual electron-dense (DED) secretory body produced in the peduncular gland cells. The DED body consists of a less electron-dense oval core in a homogeneous electron-dense matrix. On exocytosis into the pyriform haptoral reservoir, DED bodies are transformed into a secretion with two types of inclusions (less electron-dense oval and electron-dense spherical inclusions) in an electron-dense matrix. The secretions are further transformed (as small, oval, electron-dense bodies) when transported to the superficial anchor grooves, and on exudation into the gill tissues, the secretions become an electron-dense matrix. Secretory bodies associated with uniciliated structures, anchor sleeves and marginal hooks are also observed.

A deformable generic 3D model of haptoral anchor of Monogenean.

In this paper, a digital 3D model which allows for visualisation in three dimensions and interactive manipulation is explored as a tool to help us understand the structural morphology and elucidate the functions of morphological structures of fragile microorganisms which defy live studies. We developed a deformable generic 3D model of haptoral anchor of dactylogyridean monogeneans that can subsequently be deformed into different desired anchor shapes by using direct manipulation deformation technique. We used point primitives to construct the rectangular building blocks to develop our deformable 3D model. Point primitives are manually marked on a 2D illustration of an anchor on a Cartesian graph paper and a set of Cartesian coordinates for each point primitive is manually extracted from the graph paper. A Python script is then written in Blender to construct 3D rectangular building blocks based on the Cartesian coordinates. The rectangular building blocks are stacked on top or by the side of each other following their respective Cartesian coordinates of point primitive. More point primitives are added at the sites in the 3D model where more structural variations are likely to occur, in order to generate complex anchor structures. We used Catmull-Clark subdivision surface modifier to smoothen the surface and edge of the generic 3D model to obtain a smoother and more natural 3D shape and antialiasing option to reduce the jagged edges of the 3D model. This deformable generic 3D model can be deformed into different desired 3D anchor shapes through direct manipulation deformation technique by aligning the vertices (pilot points) of the newly developed deformable generic 3D model onto the 2D illustrations of the desired shapes and moving the vertices until the desire 3D shapes are formed. In this generic 3D model all the vertices present are deployed for displacement during deformation.