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Rivulus tecminae, a new killifish from Amazonas Territory Venezuela (Cyprinodontiformes: Rivulidae)
... Laimosemion ubim is a member of the Owiyeye clade, which is readily recognized by a unique frontal squamation consisting of scales transversely arranged, including a small scale just posterior to the snout with all borders free (e. g., Huber, 1992;Thomerson et al., 1992: fig. 4a; Costa, 2003: fig. ...
... Species of the Owiyeye clade exhibit a great diversity in fin morphology and colour patterns, sometimes uncommon among non-annual rivulines. For example, a truncate caudal fin is present in L. amanapira, L. rectocaudatus, L. sape, L. staecki, and L. tecminae (Thomerson et al., 1992: figs (Costa, 2003: fig. 1;Suijker & Collier, 2006: fig. ...
Laimosemion ubim, new species, is described from a small stream tributary of Lago Amanã system, Central Amazon, northern Brazil, based on external and internal anatomical morphological characters. It is considered closely related to other species of Laimosemion, subgenus Owiyeye, from the same region. It is distinguished from all other rivulids by having double-branched epipleural ribs, a condition never found among cyprinodontiforms, and from all its congeners by having hypertrophied teeth on the anterior portion of the outer row of the premax- illa and dentary in males. It reaches a maximum adult size of about 18 mm SL and exhibits several reductive characters, as expected for a miniature species, including a notable reductive character state - four branchiostegal rays.
... Caudal peduncle relatively deep (mean = 0.13 SL). Head squamation pattern similar to F-scale pattern of Hoedeman (1958) and Thomerson et al. (1992) and further described by Huber (1992) as S-pattern. Two or three scales extending into caudal fin after termination of lateral scale series. ...
... The truncate caudal fin shape of males, an important character in this group, is also seen in other Guyana Shield Rivulus species, including Rivulus tecminae Thomerson, Nico and Taphorn, 1992, which was described from the Sipapo River of the upper Orinoco basin, and Rivulus torrenticola Vermeulen and Isbrücker, 2000, described from the ZOOTAXA Kamarang River system of the Mazaruni-Essequibo drainage in Guyana. Rivulus sape can be differentiated from those species by: the absence of an imbricate head scale pattern (which is characteristic of R. tecminae); presence of short pelvic fins, in which the tips of the rays do not reach the anal-fin insertion; and by the presence of six pelvic-fin rays (seven in R. torrenticola). ...
A new species, Rivulus sape, is described from two tributaries of the upper Paragua River, Caroní River drainage, of the Guyana Shield in Venezuela. It is a small (all specimens examined less than 50 mm SL), apparently non-annual species that is distinguished from congeners in having the dorsal, anal, and pelvic fins short; adult males with a truncate caudal fin with the upper and lower borders black; and an iridescent blue, ovate spot on sides of the body above the pectoral fins. Neither adults nor juveniles have an ocellus at the dorsal junction of the caudal peduncle and caudal fin. Only one contact organ per scale on some scales along the sides of the body was observed.
... Tobogán (now Rivulus (Laimosemion) tomasi) and Rivulus (Laimosemion) sp. Maroa (Thomerson, Nico & Taphorn, 1992;Hrbek & Taphorn, 2010;Vermeulen, 2011;Vermeulen, Valdesalici & Garcia-Gil, 2013). The nature of these apparent instances of diapause have not been the subject of detailed study, and it is not known whether they occur, in all cases, at the same stages of development as has been reported in other annual South American killifish. ...
... Tobogán (now Rivulus (Laimosemion) tomasi) and Rivulus (Laimosemion) sp. Maroa (Thomerson, Nico & Taphorn, 1992;Hrbek & Taphorn, 2010;Vermeulen, 2011;Vermeulen, Valdesalici & Garcia-Gil, 2013). The nature of these apparent instances of diapause have not been the subject of detailed study, and it is not known whether they occur, in all cases, at the same stages of development as has been reported in other annual South American killifish. ...
Annual killifish that are adapted to life in aquatic habitat that dries seasonally have evolved desiccation-resistant eggs capable of undergoing diapause, i.e. developmental arrest, at specific stages during embryology. Although noted for their remarkable ability to live at the land-water interface, species in the genus Rivulus are considered to be non-annual killifish that exhibit typical teleost developmental patterns and no embryonic diapause. Here, we combine a molecular phylogeny with an embryological study in order to demonstrate an independent origin of mid-embryonic diapause within a clade of Rivulus (subgenus Laimosemion) that inhabits small streams or savannah pools. We also observed that some of these species exhibit a short dispersed cell phase separating epiboly and the formation of the embryo axis, which is a feature of development observed only in annual killifish. Lastly, we incubated embryos of Laimosemion species and outgroup taxa in both water and peat moss and observed that on peat moss the embryos of all species are capable of delaying hatching for > 10 days, but when water incubated there are significant differences among species in the duration of this delay before hatching. We hypothesize that the preferred microhabitat of this clade of killifish exposes their embryos to periodic desiccation, creating selection in favour of embryonic diapause.
... Measurements and counts follow HUBER (1992). He and the majority of authors (e. g. THOMERSON & TAPHORN, 1992;LASSO-ALCALÁ et al., 2006) use the snout tip as the most anterior point of reference. COSTA (1988), however, used the middle of the posterior limit of the depression between upper jaw and the neurocranium, and his morphometric data are compatible only to a certain extent with those published here. ...
Abstract: Based on specimens collected during several field trips in Paraguay the morphological variation, habitat requirements, and distribution of the rivulide killifish Rivulus punctatus from río Paraguay drainage are described (including specimens from the vicinity of the type locality). Males differ from females in differences of the colour pattern in the unpaired fins and in morphometrics (including longer pelvic fins and shorter preanal-fin length). The conspicuous variation in the caudal fin pat-tern of males is significantly correlated with the standard length (p<0.01). There is no correlation between morphometric data or caudal-fin pattern and geographic localities (in both cases p>0.05). The habitats are characterized by a low depth (usually less than 30 cm) of water, slow or no current and usually plenty of water and marsh plants or flooded bushes and grass.
... Among his systematic/taxonomic contributions are descriptions of two new genera, Terranatos Taphorn and Thomerson, 1978 andRenova Thomerson andTaphorn, 1995, and18 new fish species, 16 of which are Neotropical killifishes. The following is a list of new species described (in chronological order): 1) Hysteronotus myersi Weitzman and Thomerson, 1970 (now in Chrysobrycon); 2) Rivulus stellifer Thomerson and Turner, 1973 (now in Llanolebias); 3) Pterolebias hoignei Thomerson, 1974 (recognized by some as being in Gnatholebias); 4) Anchoviella belizensis Thomerson and Greenfield, 1975 (now in Anchoa); 5) Rachovia pyropunctata Taphorn and Thomerson, 1978; 6) Aphyocharax colifax Taphorn and Thomerson, 1991; 7) Rivulus immaculatus Thomerson, Nico, and Taphorn, 1991 (now in Anablepsoides); 8) Rivulus lyricauda Thomerson, Berkenkamp, and Taphorn, 1991 (now in Laimosemion); 9) Pterolebias xiphophorus Thomerson and Taphorn, 1992 (now in Micromoema); 10) Rivulus nicoi Thomerson and Taphorn, 1992 (now in Laimosemion); 11) Rivulus tecminae Thomerson, Nico, and Taphorn, 1992 (now in Laimosemion); 12) Rivulus gransabanae Lasso, Taphorn, and Thomerson, 1992 (now in Laimosemion); 13) Rivulus corpulentus Thomerson and Taphorn, 1993 (now in Laimosemion); 14) Renova oscari Thomerson and Taphorn, 1995;15) Austrofundulus guajira Hrbek, Taphorn, and Thomerson, 2005; 16) Austrofundulus leohoignei Hrbek, Taphorn, and Thomerson, 2005; 17) Austrofundulus leohoignei Hrbek, Taphorn, and Thomerson, 2005; and 18) Austrofundulus rupununi Hrbek, Taphorn, and Thomerson, 2005. As an ichthyologist, he maintained his connection with the aquarium hobby and published a number of articles on tropical fish, especially South American killifish, in The Aquarium, Aquarium Illustrated, Freshwater and Marine Aquarium magazine, and Tropical Fish Hobbyist magazine. ...
... hyaline, sometimes pale pink in Atlantirivulus). (Hoedeman, 1954), L. altivelis (Huber, 1992 (Suijker & Collier, 2006), L. manaensis (Hoedeman, 1961), L. nicoi , L. rectocaudatus (Fels & de Rham, 1981), L. romeri (Costa, 2003), L. sape (Lasso-Alcalá, Taphorn, Lasso & León-Mata, 2006), L. strigatus (Regan, 1912), L. tecminae (Thomerson, Nico & Taphorn, 1992), L. torrenticola (Vermeulen & Isbrücker, 2000), L. uakti (Costa, 2004), L. uatuman (Costa, 2004), L. xiphidius (Huber, 1979). Melanorivulus also differs from Rivulus by having the caudal-fin squamation not surpassing the basal portion of the fin (vs. ...
A maximum parsimony analysis of a combined set of mitochondrial and morphological data available in the literature for 33 rivuline taxa and three outgroups confirms Rivulus as a paraphyletic assemblage. In order to adjust a generic classification to our present phylogenetic knowledge on rivuline relationships, the following taxonomic changes are proposed: Rivulus, restricted to two species endemic to Cuba, is hypothesized to be the most basal rivuline lineage, distinguished from all other non-annual rivulines by having all hypurals fused into a single plate, neural prezygapophysis of caudal vertebrae rudimentary, fourth ceratobranchial teeth absent, about 50 % of the anterior portion of the caudal fin covered by scales, four neuromasts on the anterior supraorbital series, and a black round spot with white margin on the dorsoposterior portion of the caudal peduncle in females; Anablepsoides, Atlantirivulus, Laimosemion, Melanorivulus and Cynodonichthys, previously classified as subgenera of Rivulus, are considered as valid genera; Laimosemion, including 24 species from northern South America, con-stitutes the sister group to a clade comprising Melanorivulus, Cynodonichthys, Anablepsoides, Atlantirivulus, and all annual rivuline genera, which is supported by a well-developed dorsal process of the urohyal and an expanded lateral articular facet of the first hypobranchial; Melanorivulus, comprising 34 species from central and northeast-ern South America, Cynodonichthys with 27 species from Central America and Trans-Andean South America, Anablepsoides with 42 species from northern and northeastern South America and Smaller Antilles, and Atlanti-rivulus, with 11 species endemic to the eastern Brazilian coastal plains are diagnosed by combinations of mor-phological characters, including osteology, cephalic laterosensory system and colour patterns.
... Rivulus tecminae were taken from isolated shal low pools located about 20 m from the stream (see Thomerson et al., 1992). Myers &Weitzman (1966)observed that rock pools in the rio Negro, where Pygidianops and Typhlobelus were collected, probably had sand deposits on their bottom. ...
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