New Data on the Morphology and Distribution of Two Rare Species of Deep-Sea Anglerfish from the Families Linophrynidae a
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Data on the Morphology and Distribution of Two Rare Species of Deep-Sea Anglerfish from the Families Linophrynidae and Himantolophidae A. M. Prokofieva, b, * a
Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences (IEE RAS), Moscow, Russia b Shirshov Institute of Oceanology, Russian Academy of Sciences (IO RAS), Moscow, Russia *e-mail: [email protected] Received August 19, 2019; revised September 6, 2019; accepted September 18, 2019
Abstract—New information is given on the morphology and distribution of two little-known species of ceratioid anglerfish—Linophryne pennibarbata and Himantolophus appelii. The species L. pennibarbata was first found in the Indian Ocean. The new specimen differs from the fishes of the type series in the details of the structure of the escal appendages and the posterior branch of the hyoid barbel. Ontogenetic variability in the structure of the esca of L. pennibarbata is discussed; it has been shown that the length of the distal appendage of the esca and its lateral branches, as well as the number of appendages of the posterior (unpaired) branch of the hyoid barbel in this species are subject to significant individual variability, not related to growth. It was revealed that the previously noted differences in the size and pigmentation of the distal appendages of esca in H. appelii cannot be associated with ontogenetic variability, as was assumed, but indicate the combined nature of this species. The reasons are given for assigning the name H. appelii to a form with short, intensely pigmented (except for the tips) distal appendages. Keywords: Ceratioidei, Linophryne pennibarbata, Himantolophus appelii, Indian Ocean, diagnostic characters, ontogenetic variability DOI: 10.1134/S0032945220040177
INTRODUCTION Ceratioid anglerfish (suborder Ceratioidei) represents the most taxonomically diverse group of bathipelagic fish inhabiting depths over 1000 m. This suborder includes 11 families, 35 genera and about 170 species (Pietsch, 2009; Catalog of Fishes..., 2019), reliable species diagnostics of which in most cases is possible only for females that underwent metamorphosis, and only for one morphological structure— esca, which is a tissue distal thickening of illicium (a modified first dorsal-fin spine), usually enclosing the light organ inside and bearing a variety of appendages on its surface. Illicium is absent in the monotypic family Neoceratiidae, and the luminous organ inside the esca is absent in representatives of the family Caulophrynidae and in the genus Rhynchactis from Gigantactinidae. In some families (Caulophrynidae, Melanocetidae), esca has a rather simple and uniform structure, and other morphological structures are used in species diagnostics; finally, the species of the genus Linophryne has a peculiar hyoid barbel, the structure of which is also species-specific (Pietsch, 2009). In all other genera of Ceratioidei, species diagnostics is based solely on the structural characters of
the escal appendages, specific for each species and at the same time subje
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