Triplefin fishes from the Malpelo Fauna and Flora Sanctuary, Colombian Pacific

The fishes of the family Tripterygidae are commonly known as triplefins because its dorsal fin is divided into three segments. Of the 183 species recognized as valid only 16 are distributed in the eastern Pacific. Two endemic species and only members of the family are found in the FFS Malpelo Island: Axoclinus rubinoffi y Lepidonectes bimaculatus. In this work, additional data are provided on the adults and larvae of the triplefins of the sanctuary. The mean abundances of the larvae were 1,88 individuals/m2 for A. rubinoffi and 0.25 individuals/m2 for L. bimaculatus at the night stations where they were collected, 0.8 and 1.61 km to the west of the island and very close specifically on El Arrecife and La Nevera. The adults were collected around the island between 0-30 m depth and the abundance was 0.22 individuals/m2 for L. bimaculatus and 0.19 individuals/m2 for A. rubinoffi. The natural variability of the morphological traits of both species is extended and differences between the population densities with previous studies are found. To really understand the population dynamics of these species, it is necessary to evaluate long time series and include other methods such as genetic information.

Euphausiids (Euphausiacea) off Malpelo Island, Colombian Eastern Tropical Pacific

Euphausiids migrate vertically in the water column as part of their diel cycle. These migrations make them a key element in the biological pump of the pelagic environment. We took stratified zooplankton samples (0-50, 50-100, and 100-150 m) during the Pacífico-ERFEN campaign in September 2012 to evaluate the vertical distribution of euphausiids around Malpelo Island (3.8 - 4.2 N, 81.4 - 81.8 W). A total of 10 species belonging to four genera were identified. Euphausia diomedeae was the most abundant species in the 0-50 and 100-150 m layers, whereas E. distinguenda was the most abundant species in the 50-100 m layer. Based on quasi-Poisson generalized linear distribution models we found that abundance in the 50-100 m layer was significantly higher than in the 100-150 m layer (t = 3.05, p < 0.05). There were no significant differences associated with sampling hour (diurnal/nocturnal) (t = 0.07, p = 0.94). We calculated a vertical distribution index (VDI) based on abundance, which showed that euphausiid species were concentrated in the 50-100 m layer during day and night. Calyptopis larvae dominated in abundance at all depth layers, followed by furcilia larvae, juveniles and adults. The abundance of the latter increased gradually from the most superficial layer to the deepest layer, whereas juveniles showed the opposite pattern. This is the first study to describe the taxonomic composition, and vertical and spatial distribution of euphausiids associated with Malpelo Island, Colombian Pacific.

Primer registro, distribución y ecología de Diplophos proximus (Gonostomatidae, Teleostei) en el Pacífico colombiano

The first findings and distribution of larvae of the species Diplophos proximus, family Gonostomatidae, in the Pacific of Colombia are presented. The analyzes show larvae between Bahía Málaga and Tumaco (limits with Ecuador), with low abundances during the seasons of September 2003 and 2005, July and December 2010, December 2013, February-March 2014, June 2016 and June and September 2017, always collected at stations located more than 113 km away from the coast and around Malpelo island. The larvae are elongated and have noticeable changes during development, initially oval eyes, poorly pigmented body without photophores and finallyrounded eyes, dorsal pigments and photophores during transformation. The present work contributes with information about distribution and ecology of larvae of D. proximus becoming the first records of catches for the Colombian Pacific, including the description of the larval stages found.

PRIMER REGISTRO DEL TAMBORIL NARIGÓN (SPHOEROIDES LOBATUS: TETRAODONTIDAE) EN ISLA MALPELO, PACÍFICO COLOMBIANO

Among the eight species of the genus Sphoeroides (family Tetraodontidae) that inhabit the Tropical Eastern Pacific only Sphoeroides lobatus has been reported in more than onegroup of oceanic islands: Galápagos, Revillagigedo and Isla del Coco. This work presents the first documented record of the longnose puffer (S. lobatus) at Malpelo Island, Colombian Pacific.

The masquerade game: marine mimicry adaptation between egg-cowries and octocorals

Background.Background matching, as a camouflage strategy, is one of the most outstanding examples of adaptation, where little error or mismatch means high vulnerability to predation. It is assumed that the interplay of natural selection and adaptation are the main evolutionary forces shaping the great diversity of phenotypes observed in mimicry; however, there may be other significant processes that intervene in the development of mimicry such as phenotypic plasticity. Based on observations of background mismatching during reproduction events of egg-cowries, sea snails of the family Ovulidae that mimic the octocoral where they inhabit, we wondered if they match the host species diversity. Using observations in the field and molecular systematics, we set out to establish whether the different egg-cowrie color/shape polymorphisms correspond to distinct lineages restricted to specific octocoral species.Methods.Collection and observations of egg-cowries and their octocoral hosts were done using SCUBA diving between 2009 and 2012 at two localities in the Tropical Eastern Pacific (TEP), Malpelo Island and Cabo Corrientes (Colombia). Detailed host preference observations were done bi-annually at Malpelo Island. We analyzed the DNA sequence of the mitochondrial genesCOIand16S rDNA, extensively used in phylogenetic and DNA barcoding studies, to assess the evolutionary relationship among different egg-cowrie colorations and morphologies.Results.No genetic divergence among egg-cowries associated to different species of the same octocoral genus was observed based on the two mitochondrial genes analyzed. For instance, all egg-cowrie individuals from the two sampled localities observed on 8 differentPacifigorgia-Eugorgiaspecies showed negligible mitochondrial divergence yet large morphologic divergence, which suggests that morphologies belonging to at least two sea snail species,Simnia avena(=S. aequalis) andSimnialena rufa, can cross-fertilize.Discussion.Our study system comprised background-matching mimicry, of the masquerade type, between egg-cowries (Simnia/Simnialena) and octocorals (Pacifigorgia/Eugorgia/Leptogorgia). We observed mimicry mismatches related to fitness trade-offs, such as reproductive aggregations vs. vulnerability against predators. Despite the general assumption that coevolution of mimicry involves speciation, egg-cowries with different hosts and colorations comprise the same lineages. Consequently, we infer that there would be significant tradeoffs between mimicry and the pursuit of reproductive aggregations in egg-cowries. The findings of this study not only contribute to the understanding of the evolution of mimicry in egg-cowries, a poorly studied group of marine gastropods, but also to the development of a new biologically meaningful board game that could be implemented as a learning tool.

The Masquerade Game: marine mimicry adaptation between egg-cowries and octocorals

Background. Background matching, as a camouflage strategy, is one of the most outstanding examples of adaptation, where little error or mismatch means high vulnerability to predation. It is assumed that the interplay of natural selection and adaptation are the main evolutionary forces shaping the great diversity of phenotypes observed in mimicry, however there may be other significant processes that intervene in the development of mimicry such as phenotypic plasticity. Based on observations of background mismatching during reproduction events of egg-cowries, sea snails of the family Ovulidae that mimic the octocoral where they inhabit, we wondered if they match the host species diversity. Using observations in the field and molecular systematics, we set out to establish whether the different egg-cowrie color/shape polymorphisms correspond to distinct lineages restricted to specific octocoral species. Methods. Collection and observations of egg-cowries and their octocoral hosts were done using SCUBA diving between 2009-2012 at two localities in the Tropical Eastern Pacific (TEP), Malpelo Island and Cabo Corrientes (Colombia). Detailed host preference observations were done bi-annually at Malpelo Island. We analyzed the DNA sequence of the mitochondrial genes COI and 16S rDNA, extensively used in phylogenetic and DNA barcoding studies, to assess the evolutionary relationship among different egg-cowrie colorations and morphologies. Results. No genetic divergence among egg-cowries associated to different species of the same octocoral genus was observed based on the two mitochondrial genes analyzed. For instance, all egg-cowrie individuals from the two sampled localities observed on 8 different Pacifigorgia-Eugorgia species showed negligible mitochondrial divergence yet large morphologic divergence, which suggests that morphologies belonging to at least two sea snail species, Simnia avena (=S. aequalis) and Simnialena rufa, can cross-fertilize. Discussion. Our study system comprised background-matching mimicry, of the masquerade type, between egg-cowries (Simnia/Simnialena) and octocorals (Pacifigorgia/Eugorgia/Leptogorgia). We observed mimicry mismatches related to fitness trade-offs, such as reproductive aggregations vs. vulnerability against predators. Despite the general assumption that coevolution of mimicry involves speciation, egg-cowries with different hosts and colorations comprise the same lineages. Consequently, we infer that there would be significant tradeoffs between mimicry and the pursuit of reproductive aggregations in egg-cowries. The findings of this study not only contribute to the understanding of the evolution of mimicry in egg-cowries, a poorly studied group of marine gastropods, but also to the development of a new biologically meaningful board game that could be implemented as a learning tool.