What came first, the shark or the egg? Discovery of a new species of deepwater shark by investigation of egg case morphology

Apristurus ovicorrugatus, a new species of deepwater catshark, is described from northwestern Australia. Unique egg cases belonging to an unknown species of Apristurus prompted a more detailed investigation of Apristurus specimens off northwestern Australia. One specimen previously identified as A. sinensis collected off Dampier Archipelago was found gravid with a single egg case. Removal of this egg case confirmed that this species was responsible for producing the unique egg cases previously recorded. The egg cases of this species have strong T-shaped longitudinal ridges on the dorsal and ventral surfaces which are unique in the genus Apristurus. The ridges most closely resemble those present in Bythaelurus canescens from South America, but are larger and always T-shaped. The holotype is closest morphologically to A. sinensis but differs in having a medium brown buccal cavity (vs. jet black), ridged egg cases (vs. smooth egg cases), fewer intestinal spiral valve turns and larger pectoral fins. The holotype is also similar, and closest on a molecular level, to A. nakayai with which it shares a unique synapomorphic character, the white shiny iris (apomorphic within the genus). A late-term embryo removed from an egg case superficially resembled the holotype except in having two parallel rows of enlarged dermal denticles on the dorsolateral predorsal surface. Recent nomenclatural changes to the genera Apristurus and Pentanchus are discussed and challenged. This study highlights the important contribution that egg case morphology has on oviparous elasmobranch taxonomy.

Reproductive biology of the swell shark Cephaloscyllium ventriosum (Carcharhiniformes: Scyliorhinidae)

The Cephaloscyllium ventriosum shark is present in the artisanal fisheries of elasmobranchs on the western coast of Baja California Sur, Mexico. The main characteristics of the sexual maturation of this species based on individuals captured from off north-west Mexico in 2013-2016 are described. The size at maturity of this species was determined for the first time (total length 82 cm for females and 76 cm for males). Most females had one egg case per one uterus, and two per one uterus was an isolated event of low incidence. From the histological analysis of females, it was possible to show sperm storage in the oviducal gland. Fully developed sperm in immature organisms were identified in the testes. The main indicator of the maturity stage of males and their mating activity is the clasper. The present study provides evidence for a reliable estimation of the sexual maturity of these organisms, demonstrating the need for the combination of macroscopic and microscopic methods.

Reproductive biology of the Rasptail skate Rostroraja velezi (Rajiformes: Rajidae)

The Rasptail skate Rostroraja velezi is commercially exploited in artisanal elasmobranch fisheries along the west coast of Baja California Sur, Mexico, but information on its life history is limited. This study aimed to investigate the reproductive biology of R. velezi. A total of 105 specimens were caught from April 2008 to May 2012, including the largest reported specimen with 121 cm total length, 96 cm disc width (D_W ). Females attained larger sizes than males. Males and females presented functional gonads. There was an asymmetry in the testes of males, with the left testis being larger. Histological analysis of the reproductive biology of R. velezi was performed here for the first time. The presence of sperm storage in females and spermatogenic development beginning at the first stages of maturity in males was recorded. It was possible to identify the development of secretions in the club, baffle and terminal zone of the oviducal gland. D_W at maturity, defined as the D_W at which 50% of the population is mature, was estimated at 68-72 cm for females and 65.1 cm for males. Egg-bearing females caught in April and May presented one egg capsule per uterus. Furthermore, a description of the egg capsule of R. velezi is provided. Elucidating the reproductive cycle, the type of reproductive strategies, and the fecundity of R. velezi will allow us to understand the impact of fisheries on this species.

Description of the egg cases and juvenile colouration in two catsharks of the genus Atelomycterus (Carcharhiniformes: Scyliorhinidae)

Descriptions of egg cases and hatchlings of the Bali catshark Atelomycterus baliensis and the Australian marbled catshark Atelomycterus macleayi are provided. Comparisons are made with two of their congeners, banded sand catshark Atelomycterus fasciatus and coral catshark Atelomycterus marmoratus. The Atelomycterus egg cases have the same general morphology, i.e., elongate with anterior and posterior waists, a depressed and truncate anterior end sometimes with attachment fibres, a medially tapered posterior end with two horns sometimes terminating in short, tightly curled tendrils and four respiratory fissures (one at each left corner on opposing sides). Morphometric measurements taken of the egg cases of the four species differed significantly when subjected to multivariate analysis, with unique characters enabling distinction between them. The morphological characters that best distinguished the Atelomycterus species from each other were anterior border width, posterior waist width and posterior case width. Thus, egg case morphology could be used to distinguish the egg cases of the four Atelomycterus species examined, consistent with other studies on scyliorhinid and pentanchid egg cases. Colouration of A. baliensis and A. macleayi juveniles was similar to that of other Atelomycterus juveniles in being pale with a series of dark-brown distinct dorsal saddles along the body, blotches and sometimes with a low number of small dark spots.

First observations on captive hatching and incubation period of the yellow-nose skate Dipturus chilensis (Rajiformes: Rajidae), from the South-Eastern Pacific Ocean

Twelve egg capsules laid in captivity by three females of Dipturus chilensis were incubated in the laboratory. After 252 ± 9.4 days, 10 skates successfully hatched, with a mean total length, disc length, and disc width of 17.2, 7.4, and 11.4 cm, respectively. This is the first report of captive hatching of D. chilensis and its corresponding incubation period.

Egg cases of the graytail skate Bathyraja griseocauda and the cuphead skate Bathyraja scaphiops from the south-west Atlantic Ocean

Egg cases of Bathyraja griseocauda were larger (140-142 mm in length) than those of Bathyraja scaphiops (88-90 mm in length) and their surface was relatively smooth, without denticles, prickles or any ornamentation. Egg cases of B. scaphiops had a relative coarse surface, covered with prickles of similar size. An identification key for the all described egg cases from Bathyraja occurring in the south-west Atlantic Ocean is provided.