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Background The overall anatomy of the genus Syllis (Annelida: Syllidae) has been largely studied; however, an integrative approach considering different anatomical techniques has never been considered. Here, we use micro-computed X-ray tomography (micro-CT) to examine the internal anatomy of Syllis gracilis Grube, 1840, along with other widely available techniques. Methods We studied the anatomy of the marine annelid S. gracilis through an integrative approach, including micro-CT along with stereo and light compound microscopy (STM, LCM), scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM) and histological sectioning (HIS). In this manner, we evaluated the applicability of micro-CT for the examination of annelid anatomy by testing whether the images obtained make it possible to visualize the main body structures, in comparison with other current techniques, of the various elements of its internal anatomy. Results Overall external and internal body elements are clearly shown by the integrative use of all techniques, thus overcoming the limitations of each when studied separately.Any given method shows disparate results, depending on the body part considered. For instance, micro-CT provided good images of the external anatomy, including relevant characters such as the shape, length and number of articles of dorsal parapodial cirri. However, it is especially useful for the examination of internal anatomy, thus allowing for 3D visualization of the natural spatial arrangement of the different organs. The features best visualized are those of higher tissue density (i.e., body musculature, anterior parts of the digestive tract), particularly in 3D images of unstained specimens, whereas less electrodense tissues (i.e., the peritoneal lining of septa and nervous system) are less clearly visualized. The use of iodine stain with micro-CT has shown advantages against non-staining for the adequate observation of delicate elements of low density, such as the segmental organs, the connective between the ganglia, the ventral nerve cord and segmental nerves. Discussion Main external anatomical elements of S. gracilis are well shown with micro-CT, but images show lesser optical resolution and contrast when compared to micrographs provided by SEM and CLSM, especially for fine structural features of chaetae. Comparison of micro-CT and HIS images revealed the utility and reliability of the former to show the presence, shape and spatial disposition of most internal body organs; the resolution of micro-CT images at a cellular level is, however, much lower than that of HIS, which makes both techniques complementary.

SUMMARY: Knowledge on taxonomy and ecology of leptostracan crustaceans is still scarce in many parts of the world. Sampling in subtidal sediments in the Ria of Ferrol (NW Spain) between 2006 and 2007 yielded several leptostracan specimens belonging to six species. This is, so far, the largest number of leptostracan species reported from a single area. Some specimens belong to an undescribed species of Nebalia Leach, 1814, which is described herein as N. reboredae n. sp. The new species has a rostrum about 2.2 times as long as wide, the antennular scale is slightly more than twice as long as wide, the fourth article of the antennule has one short thick distal spine, the first article of the endopod of the second maxilla is 1.3 times as long as the second one, the exopod of the second maxilla is longer than the first article of the endopod, the posterior dorsal borders of pleonites 5-7 are provided with distally rounded to truncated denticles, and the uropods are as long as pleonite 7 and the anal somite combined. All the species collected are reported, including the number of specimens, sexual condition and substrate type. A key to all known neritic species of the Iberian Peninsula is provided.Keywords: Crustacea, Leptostraca, Nebalia, Sarsinebalia, subtidal, sediment, Ría de Ferrol, Atlantic.RESUMEN: Leptostráceos (Crustacea: Phyllocarida) de la Ría de Ferrol (Galicia, NO península Ibérica) con la descripción de una nueva especie de Nebalia Leach, 1814. -El conocimiento sobre la taxonomía y ecología del orden Leptostraca en muchas partes del mundo es todavía fragmentario. El examen de muestras infralitorales recolectadas en la Ría de Ferrol (NO península Ibérica) entre 2006 y 2007 ha revelado la presencia de seis especies de leptostráceos. Hasta la fecha, este es el mayor número de especies encontradas en una única área. Varios de los ejemplares encontrados pertenecen a una especie no descrita del género Nebalia Leach, 1814, que es descrita en el presente trabajo como N. reboredae n. sp. La nueva especie se caracteriza por presentar un rostro 2.2 veces más largo que ancho, una escama antenular algo más de dos veces más larga que ancha, el cuarto segmento de la anténula porta una única espina corta gruesa distal, el primer segmento del endopodio de la segunda maxila es 1.4 veces más largo que el segundo segmento, el exopodio de la segunda maxila es más largo que el primer segmento del endopodio, los dentículos del borde posterior dorsal de los pleonitos 5-7 son distalmente de redondeados a truncados, y los urópodos son tan largos como el pleonito 7 y el somita anal combinados. Se indica para todas las especies encontradas tanto el número de ejemplares como estado sexual y tipo de sustrato. Se incluye una clave para todas las especies de leptostráceos neríticos encontrados en la península Ibérica hasta la fecha.

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To identify the putative amygdalar complex in cartilaginous fishes, our first step was to obtain evidence that supports the existence of a pallial amygdala in the catshark <i>Scyliorhinus canicula</i>, at present the prevailing chondrichthyan model in comparative neurobiology and developmental biology. To this end, we analyzed the organization of the lateral walls of the telencephalic hemispheres of adults, juveniles, and early prehatching embryos by immunohistochemistry against tyrosine hydroxylase (TH), somatostatin (SOM), Pax6, serotonin (5HT), substance P (SP), and Met-enkephalin (MetEnk), calbindin-28k (CB), and calretinin (CR), and by in situ hybridization against regulatory genes such as <i>Tbr1</i>, <i>Lhx9</i>, <i>Emx1</i>, and <i>Dlx2</i>. Our data were integrated with those available from the literature related to the secondary olfactory projections in this shark species. We have characterized two possible amygdalar territories. One, which may represent a ventropallial component, was identified by its chemical signature (moderate density of Pax6-ir cells, scarce TH-ir and SOM-ir cells, and absence of CR-ir and CB-ir cells) and gene expressions (<i>Tbr1</i> and <i>Lhx9</i> expressions in an <i>Emx1</i> negative domain, as the ventral pallium of amniotes). It is perhaps comparable to the lateral amygdala of amphibians and the pallial amygdala of teleosts. The second was a territory related to the pallial-subpallial boundary with abundant Pax6-ir and CR-ir cells, and 5HT-ir, SP-ir, and MetEnk-ir fibers capping dorsally the area superficialis basalis. This olfactory-related region at the neighborhood of the pallial-subpallial boundary may represent a subpallial amygdala subdivision that possibly contains migrated cells of ventropallial origin.

Solenogastres are vermiform marine molluscs characterised by an aculiferous mantle, a longitudinal ventral pedal groove and a terminal or subterminal pallial cavity. Their classification is based in part on the type of mantle sclerites, but identification to even the family level generally requires the study of internal anatomical characters. Taxonomically important internal characters include those related to radular structure, the type of ventrolateral glandular organs of the pharynx and the reproductive system, among others. In order to study their internal anatomical organisation, according to the classical reconstruction method, serial histological sections of specimens are made, from which the 2D internal anatomy of the specimen can be reconstructed manually. However, this is a time-consuming technique that results in destruction of the specimen. Computed microtomography or micro-CT is a non-destructive technique based on the measurement of the attenuation of X-rays as they pass through a specimen. Micro-CT is faster than histology for studying internal anatomy and it is non-destructive, meaning that specimens may be used for e.g., DNA extraction or retained as intact vouchers. In this paper, the utility of micro-CT for studying taxonomically important internal anatomical structures was assessed. Results of the 3D anatomical study of the soft parts of four specimens of three species using micro-CT are presented: Proneomenia sluiteriHubrecht, 1880, Dorymenia menchuescribanaeGarcía-Álvarez et al., 2000 and Anamenia gorgonophilaKowalevsky, 1880. Micro-CT enabled detailed study of most taxonomically important anatomical characters, precise measurements of structures, and observation of the relative position of organs from a variety of angles. However, it was not possible to observe the radula and some details of the ventral foregut organs could not be discerned. Despite these limitations, results of this study highlight micro-CT as a valuable tool to compliment histology in the study of solenogaster anatomy and in non-destructively identifying animals to the family and even genus-level.

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Polyophthalmus zhadanae sp. nov. (Annelida, Opheliidae), is described from the coast of Kuwait and Saudi Arabia (Arabian Gulf) after specimens collected in the intertidal and shallow subtidal. This new species is characterised by the body pigmentation pattern, distribution of lateral eyes, presence of small dorsal and ventral parapodial cirri and pygidial features. External and internal anatomy was described after examination with SEM and micro-CT. The presence of several body structures in the genus such as a cephalic palpode-like papilla is discussed. Furthermore, the diversity of genus Polyophthalmus and the presence of Polyophthalmus pictus (Dujardin, 1839) in the Indo-Pacific is reviewed and a key to species is provided.