Wednesday, February 7, 2018

[Crustacea • 2018] Mayaweckelia troglomorpha • A New Subterranean Amphipod Species (Amphipoda, Hadziidae) from Yucatán State, México


Mayaweckelia troglomorpha Angyal

in Angyal, Solís, Magaña, Balázs & Simoes, 2018

Abstract
A detailed description of a new stygobiont species of the amphipod family Hadziidae, Mayaweckelia troglomorpha Angyal, sp. n. is given, based on material collected in four cenotes of Yucatán federal state, México. Morphology was studied under light microscopy and with scanning electron microscopy. Morphological description is complemented with mitochondrial cytochrome c oxidase subunit I (COI) sequences as barcodes, with affinities to the related taxa and with notes on the species’ ecology. Using COI Bayesian inference and genetic distance analyses, we show that the closest relative of the new species is M. cenoticola, forming a monophyletic group referring to the genus Mayaweckelia. Based on the available sequences, we also revealed that Mayaweckelia and Tuluweckelia are sister genera, standing close to the third Yucatán subterranean genus, Bahadzia. The data gathered on the habitat, distribution, abundance, and ecology will contribute to the conservation planning for M. troglomorpha Angyal, sp. n.

Keywords: cenote, description, endemic, Hadziidae, mitochondrial marker, morphology, SEM, sinkhole, subterranean


Figure 2. Mayaweckelia troglomorpha sp. n., living specimens.
Above: allotype ♀ collected in Cenote Kankirixché;
below: individual photographed in its natural habitat during research dive in Cenote Kanún (not collected).
Taxonomy
Order Amphipoda Latreille, 1816
Suborder Senticaudata Lowry & Myers, 2013

Family Hadziidae S. Karaman, 1943
Genus Mayaweckelia Holsinger, 1977

Mayaweckelia troglomorpha Angyal, sp. n.

Diagnosis: Medium-sized, eyeless hadziid with conspicuous troglomorphic traits. The first antenna almost twice as long as body and three times as long as the second antenna; gnathopod I propodus palm armed with distally notched spine teeth, carpus more than 1.5 times as long as corresponding propodus, merus as broad as but shorter than carpus, ventrally produced lobe with three long sensory setae; gnathopod II propodus twice as long as propodus I, palm armed with unnotched spine teeth, carpus slightly shorter than propodus on males. Dactylus, propodus. and carpus of pereopods VI-VII extremely long; therefore, pereopods VI and VII are 1.3 times as long as body length; epimeral plates I-III ventro-posterior corner tiny but distinct, ventral margin without robust setae, posterior margins concave; surfaces of uropods I-III pubescent; telson lobes each possess five-six robust setae and one-three slender setae on outer margin and six-seven robust setae on inner margin. Largest males and females both measured 10 mm.

Etymology: The name troglomorpha refers to the highly adaptive troglomorphic features of the new species, particularly the elongation of appendages, the increased number of sensory setae and papillae, and general appearance of fragility. Gender feminine.

Distribution and remarks on ecology: The new species is known from four cenotes in the state of Yucatán, covering a distribution distance of 52 km (distance between the farthest cenotes Dzonbakal and Xaan). All the individuals were found in fresh water habitat, in most cases far from the cenote entrances, deeper in the associated cave passages, where sunlight does not penetrate. Water temperature was between 26 and 27 °C. Specimens were collected between 20 and 33 meters depth; in cenote Kankirixché some individuals were observed below 45 meters depth. The new species was represented in all four localities with low abundance, though it proved to be more common and more abundant than M. cenoticola, of which a single specimen was found in only one (Ayun-Nah) of the 14 visited cenotes, during an underwater waste collecting activity, hidden in a plastic soft drink bottle. In the type locality and in cenotes Xaan and Kankirixché the new species co-occurred with the hadziid amphipod Tuluweckelia cernua. Other co-occurring stygobiont macro-crustaceans (in the four cenotes) were the mysid Antromysis cenotensis Creaser, 1936, the stygiomysid Stygiomysis cf. holthuisi (Gordon, 1958), the isopods Creaseriella anops (Creaser, 1936) and Yucatalana robustispina Botosaneanu & Iliffe, 1999, and the decapods Typhlatya mitchelli Hobbs & Hobbs, 1976, Typhlatya pearsei Creaser, 1936, and Creaseria morleyi (Creaser, 1936).

....

Conclusions: 
To date, only a small proportion of the cenotes and other aquatic hypogean ecosystems have been studied in Yucatán state in zoological aspect. Our expedition has led to the discovery of a new species of subterranean hadziids, which confirms that exploration and further studies of the region’s groundwater Crustacea diversity is necessary. Description of the new species was completed with comparative scanning electron microscopy, which was used for first time on Mayaweckelia. It proved to be a rather useful method for discovering, analysing, and illustrating barely visible diagnostic characters. As contributions to the future molecular genetic studies on Yucatán subterranean hadziids, COI sequences as barcodes of M. troglomorpha sp. n., M. cenoticola, and T. cernua are now publicly available in GenBank. The phylogenetic studies have shown that based on the available sequences, the closest relative of the new species is M. cenoticola. In accordance with the previous cladistic studies, Mayaweckelia and Tuluweckelia prove to be sister genera, closely related to Bahadzia, the third Yucatán subterranean Hadziidae genus. This knowledge may contribute to the species’ future conservation planning.

 Dorottya Angyal, Efraín Chávez Solís, Benjamín Magaña, Gergely Balázs and Nuno Simoes. 2018. Mayaweckelia troglomorpha, A New Subterranean Amphipod Species from Yucatán State, México (Amphipoda, Hadziidae). ZooKeys. 735; 1-25.  DOI: 10.3897/zookeys.735.21164

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