Alcolyra, a new genus of leucosiid crab (Crustacea: Decapoda: Brachyura) from India

The identity of Philyra alcocki Kemp, 1915 (Leucosiidae), a species described from Chilika Lake, India is clarified. The redescription of lectotype male and examination of fresh material collected from Chilika Lake, Odisha state of India revealed that P. alcocki is significantly different morphologically from members of Philyra senso stricto and other allied genera in possessing two tuberculated rows on the branchial region of carapace, and a well-developed tubercle on male thoracic sternite 5 on either side of the sternopleonal cavity. Therefore, a new genus Alcolyra n. gen. is established herewith for the species.

A Paleozoic stem hagfish Myxinikela siroka — revised anatomy and implications for evolution of the living jawless vertebrate lineages

Hagfishes and lampreys comprise cyclostomes, the earliest branching and sole surviving clade of the once diverse assemblage of jawless crown-group vertebrates. Lacking mineralized skeletons, both of the crown cyclostome lineages have notoriously poor fossil record. Particularly in the hagfish total group, †Myxinikela siroka Bardack, 1991 from the Late Carboniferous estuarine system of Illinois (USA) represents the only definitive stem taxon. Previously known from a single specimen, Myxinikela has been reconstructed as a short-bodied form with pigmented eyes but otherwise difficult to distinguish from the living counterpart. With a new, second specimen of Myxinikela reported here, I reevaluate the soft tissue anatomy and formulate diagnosis for the taxon. Myxinikela has a number of general features of cyclostomes, including cartilaginous branchial baskets, separation between the esophageal and the branchial passages, and a well-differentiated midline finfold. In effect, these features give more lamprey-like appearance to this stem hagfish than previously assumed. Myxinikela still has many traits that set modern hagfishes apart from other vertebrates (e.g., nasohypophyseal aperture, large velar cavity, and cardinal heart) and some intermediate conditions of modern hagfishes (e.g., incipient posterior displacement of branchial region). Thus, Myxinikela provides an important calibration point with which to date origins of these characters.

The diversity of the genus Aricidea (Polychaeta: Paraonidae) from the Sea of Marmara, with descriptions of two new species and two new records for the Mediterranean fauna

This paper reports 13 Aricidea species from the Sea of Marmara. The Aricidea specimens were collected at 98 stations in the region in 2012 and 2013 from soft and hard substrata at depths ranging from 0 to 1200 m. Among the material, two new species, namely Aricidea (Acmira) katzmanni n. sp. and Aricidea (Acmira) pseudoassimilis n. sp., and 11 known species were discovered. Aricidea mirunekoa and A. bulbosa are new records for the Mediterranean fauna; A. (Acmira) annae and A. (Aricidea) wassi are new records for the Sea of Marmara. Aricidea (Acmira) katzmanni n. sp. is characterized by having a long, digitiform antenna; no notopodial papillae on the posterior part of the branchial region; and hook shaped modified neurochaetae with a strong hood and fragile arista. Aricidea (Acmira) pseudoassimilis n. sp. is characterized by having a short, digitiform antenna; interramal lobes between notopodia and neuropodia; hook-shaped modified neurochaeta that gets subterminally thinner with a rounded tip. As A. (Strelzovia) bulbosa has been only previously reported from the Gulf of Suez (Red Sea), it could be a new alien species for the Sea of Marmara and Mediterranean Sea. Based on the characters that have been overlooked so far, the subspecies A. suecica meridionalis and A. capensis bansei were raised to species level, A. meridionalis n. stat. and A. bansei n. stat. The present paper reports the usage of ciliary bands and slits on the prostomium and body, swellings/ridges in the branchial region, and the shape and distribution of sense organs in the taxonomy of Aricidea. All species were described and figured.

Description of a new species of deep-sea spider crab from the genus Crocydocinus Lee, Richer de Forges & Ng, 2019, from the south-eastern Arabian Sea (Crustacea: Decapoda: Majoidea: Epialtidae)

A new species of spider crab is described from two male specimens collected from the southeastern Arabian Sea. This species differs from its congeners in the absence of uograstric granule on carapace, the presence of two granules along lateral margin of carapace at branchial region, the presence of granules on P2–P4 dactyli and the constricted distal tip of the male first gonopod.

Respiratory faculties of aquatic craniotes

This chapter introduces the ‘who has what’ in terms of water-breathing respiratory faculties for craniotes. A branchial basket and a ventral heart or hearts that perfuse the branchial region with deoxygenated internal fluid is part of the bauplan of all chordates, including craniotes. Cilia ventilate the branchial region of extant non-craniote chordates, which are also predominantly sessile or planktonic filter feeders. In craniotes, the gills are the main gas exchange organs. They are ventilated by muscular activity and perfused with blood that contains haemoglobin in erythrocytes and flows in the opposite direction to the ventilated water (counter-current model). In spite of major differences in the structure of gills and the ventilatory apparatus among jawless craniotes, cartilaginous fish, and bony fish, the basic push–pull, constant, unidirectional flow respiratory mechanism remains unchanged (of course, with a few notable exceptions). In addition, both the blood and the structure of the gills may reflect adaptations of the respiratory faculty to habitual living conditions.

nkx3.2 mutant zebrafish accommodate jaw joint loss through a phenocopy of the head shapes of Paleozoic jawless fish

The vertebrate jaw is a versatile feeding apparatus that facilitated explosive diversification. To function, it requires a joint between the upper and lower jaws, so jaw joint defects - such as osteoarthritis or even ankylosis - are often highly disruptive and difficult to study. To describe consequences of jaw-joint dysfunction, we engineered two independent null alleles of a single jaw-joint marker gene, nkx3.2, in zebrafish. These mutations caused zebrafish to become functionally jawless via fusion of the upper and lower jaw cartilages (ankylosis). Despite lacking jaw joints, nkx3.2 mutants survive to adulthood and accommodate this defect by: a) remodeling their skulls; and b) altering their behavior from suction feeding to ram feeding. As a result of remodeling, nkx3.2 mutants developed superficial similarities to the skull shapes observed in two lineages of ancient jawless vertebrates (anaspids and furcacaudiid thelodonts), including: a fixed open gape, reduced snout, and enlarged branchial region. However, no homology exists in individual skull elements between these taxa, and most of the modified elements in the mutant zebrafish occur outside known expression domains of nkx3.2. Therefore, we interpret the adult nkx3.2 phenotype not as a reversal to an ancestral state, but as convergence due to similar functional requirement of feeding without moveable jaws. This remarkable convergence strongly suggests that jaw movements themselves dramatically influence the development of jawed vertebrate skulls, which implies that functionally viable skull morphologies are finite, with or without functional jaws. Because nkx3.2 null zebrafish display prominent joint ankylosis, drastically modified skull shape, and altered feeding behaviors, these mutants provide a unique model with which to investigate mechanisms of skeletal remodeling and joint diseases.

Morphological revision of the Subgroup 1 Fauchald, 1970 of Marphysa de Quatrefages, 1865 (Eunicidae: Polychaeta)

Fifteen species of Marphysa classified in the Subgroup 1 Fauchald (1970) were reviewed and evaluated in a morphological analysis of the subgroup. It was found that 13 of these have a characteristic morphological pattern distinct from that of Marphysa sensu stricto; as a consequence, a new genus is proposed, Paucibranchia n. gen. This new genus includes the species that have branchiae restricted to a few chaetigers in the anterior region, maxillae I with a rounded falcal arch and outer edge with a straight base plus a curvature in the basal inner edge, dorsal cirri longer in the branchial region and in media-posterior region as long or longer than pre-branchial chaetigers, and the postchaetal lobe in the branchial region well developed, elongated. Paucibranchia n. gen. includes six new species (P. andresi n. sp., P. carrerai n. sp., P. gathofi n. sp., P. gilberti n. sp., P. miroi n. sp. and P. patriciae n. sp.), two species not formally named, and other 13 species previously included in Marphysa (P. adenensis (Gravier, 1900) n. comb., P. bellii (Audouin & Milne-Edwards, 1833) n. comb., P. cinari (Kurt-Sahin, 2014) n. comb., P. conferta (Moore, 1911) n. comb., P. disjuncta (Hartman, 1961) n. comb., P. fallax (Marion & Bobretzky, 1875) n. comb., P. gemmata (Mohammad, 1973) n. comb., P. kinbergi (McIntosh, 1910) n. comb., P. oculata (Treadwell, 1921) n. comb., P. purcellana (Willey, 1904) n. comb., P. sinensis (Monro, 1934) n. comb., P. stragula (Grube, 1878) n. comb., P. totospinata (Lu & Fauchald, 1998) n. comb.). One species previously classified in the subgroup, Marphysa striata (Kinberg, 1865), was considered indeterminate. Finally, some statistical analyses on size dependent features and an identification key for species of the new genus were included.

Cirrophorus species (Annelida: Polychaeta: Paraonidae) in the Sea of Marmara, with description of a new species

This paper deals with specimens of Cirrophorus collected from the depths ranging from 3 to 500 m in 2012 and 2013 in the Sea of Marmara, Turkey. Among the material, one new species and two already known species were found. The new species is mainly characterized by having long and clavate notopodial postchaetal lobes in the branchial region; red speckles near nuchal organs; and a very long branch of lyrate chaetae (4 times longer than the shorter one). A recently described species, Cirrophorus nikebianchii, was found at the majority of soft-bottom stations. All species found in the area were described and discussed.

Ciderius cooperi gen. nov., sp. nov., the earliest known euphaneropid from the Lower Silurian of Scotland

A new genus and species of euphaneropid, Ciderius cooperi, is recorded from the Lower Silurian Fish Bed Formation of the Midland Valley of Scotland on the basis of articulated material. Euphaneropids constitute an enigmatic group which is known from Devonian deposits in Scotland and Canada. The new find adds to our understanding of this group, in particular with regard to the morphology of some common anatomical elements. The paired head stains are here shown to contain clefts which can be interpreted as optic fissures, indicating that these are the remains of eyes. The anterior head stain is reconstructed and demonstrated to be a barrel-shaped object of an uncertain nature. Paired mineralisations situated in the posterior part of the cranial region appear to represent remains of the parachordals, while fossilised blood vessels might be preserved in the form of black lines which mark a greatly elongated branchial region, similar to euphaneropids. Serially repetitive rows of short horizontal stripes on the posterior half of the body are unique for the new taxo, but their interpretation is problematic.

The Indonesian species of Macrophthalmus Desmarest, 1823, with the description of a new species (Crustacea: Decapoda: Brachyura: Macrophthalmidae)

Fourteen species of Macrophthalmus Desmarest, 1823, are reported from Indonesia, of which two species, Macrophthal-mus (Macrophthalmus) abbreviatus Manning & Holthuis, 1981, and M. (Macrophthalmus) sulcatus malaccensis Tweedie,1937, are recorded for the first time from the region, and one new species M. (Mareotis) fusculatus n. sp. is described. Thenew species resembles M. (Mareotis) definitus Adams & White, 1849, in the relatively narrow male abdomen and mod-erately long, curved tip of the male G1. However, the differences are noticeable in the morphology of the carapace of thenew species which is divergent posterolateraly, the presence of tubercles on the gastric, cardiac and intestinal regions, and the absence of a longitudinal row of granules or setae on the branchial region.