Myotis lavali Moratelli, Peracchi, Dias, and Oliveira, 2011

Novaes, Roberto Leonan M, Hintze, Frederico & Moratelli, Ricardo, 2022, Myotis lavali (Chiroptera: Vespertilionidae), Mammalian Species 54 (1018), pp. 1-8 : 1-5

Myotis lavali Moratelli, Peracchi, Dias, and Oliveira, 2011

LaVal’s Myotis

Myotis nigricans : Mares et al. 1981:83. Not Myotis nigricans

(Schinz, 1821); see “Nomenclatural Notes.”

Myotis nigricans : Willig 1983:16. Not Myotis nigricans

(Schinz, 1821).

Myotis nigricans : Willig 1985a:18. Not Myotis nigricans

(Schinz, 1821).

Myotis nigricans : Willig 1985b:671. Not Myotis nigricans

(Schinz, 1821).

Myotis nigricans : Willig 1986:158. Not Myotis nigricans

(Schinz, 1821).

Myotis nigricans : Willig et al. 1986:197. Not Myotis nigricans

(Schinz, 1821).

Myotis riparius : Willig and Moulton 1989:325. Not Myotis riparius Handley, 1960 .

Myotis riparius : Willig and Hollander 1995:986. Not Myotis riparius Handley, 1960 .

Myotis nigricans : Ruedi and Mayer 2001:438. Not Myotis nigricans (Schinz, 1821) .

Myotis nigricans : Stadelmann et al. 2007:34. Not Myotis nigricans (Schinz, 1821) .

Myotis nigricans : Gregorin et al. 2011:302. Not Myotis nigricans (Schinz, 1821) .

Myotis lavali Moratelli, Peracchi, Dias, and Oliveira, 2011:602 . Type locality “ 6 km S of Exu (7°30’S, 39°43’W), Pernambuco State, Brazil, 523 m above sea level.”

Myotis nigricans : Antonio 2015:26. Not Myotis nigricans (Schinz, 1821) .

CONTEXT AND CONTENT. Order Chiroptera , suborder Yangochiroptera , family Vespertilionidae , subfamily Myotinae , genus Myotis , subgenus Pizonyx , and species-group albescens ( Moratelli et al. 2019) . Myotis lavali is monotypic ( Moratelli et al. 2011; Novaes 2019). Specimens from Brazilian Caatinga and Cerrado reported as either M. nigricans (e.g., Mares et al. 1981; Willig 1983, 1985a, 1985b, 1986; Willig et al. 1986; Ruedi and Mayer 2001; Stadelmann et al. 2007; Gregorin et al. 2011; Antonio 2015) or M. riparius ( Willig and Moulton 1989; Willig and Hollander 1995) are misidentifications of M. lavali . Myotis lavali was described based on morphological characters and can be distinguished from its congeners by the texture, length, and color of the fur and by skull features ( Moratelli et al. 2011).

DIAGNOSIS

The following characters are the most useful for identifying Myotis lavali : dorsal fur strongly bicolored, with medium-brown bases (2/3 of the hair length) and light-brown tips (1/3); fringe of hairs along the trailing edge of uropatagium absent; skull with forehead steeply sloping relative to the braincase ( Moratelli et al. 2011).

Myotis lavali is in sympatry only with M. riparius (riparian myotis), M. ruber (red myotis), and M. albescens (silver-tipped myotis). It can be distinguished from the first two by its silky, long fur, with a strong contrast between bases and tips. In the absence of a skin specimen, M. lavali can be distinguished by the forehead steeply sloping with regard to the braincase. Myotis lavali can also be distinguished from M. albescens by the absence of fringe of hairs along the trailing edge of uropatagium and strong bicolored dorsal fur ( Moratelli et al. 2011; Novaes 2019). It is in potential sympatry with M. simus (velvety myotis) and M. dinellii (Dinelli’s myotis) at its southernmost distributional boundary. Myotis lavali can be easily distinguished from M. simus by its silky, long fur, with a strong contrast between bases and tips, and its plagiopatagium attached to the toes by a broad band of membrane; and can be distinguished from M. dinellii by its shorter ears (<15 mm in M. lavali ;> 15 mm in M. dinellii ), absence of fringe of hairs along the trailing edge of uropatagium, presence of sagittal and lambdoidal crests, and postorbital constriction generally greater than 4 mm ( Moratelli et al. 2011; Novaes 2019).

GENERAL CHARACTERS

Myotis lavali ( Fig. 1 ) is a small- to medium-sized species relative to other South American Myotis (measurements provided below), and morphologically similar to its Neotropical congeners. Ears are comparatively medium-sized (13–15 mm; Fig. 2 ), extending forward halfway from eye to nostril. The antitragal notch is barely evident. The tragus is pointed, slightly curving outward above and convex below, with a small triangular lobule at the outer base. Membranes are Mummy Brown (following Ridgway 1912). The plagiopatagium is attached to the toes by a broad band of the membrane. The fringe of hairs along the trailing edge of the uropatagium is absent, although some hairs may be present in a few specimens; and the upper and lower surfaces of the uropatagium are barely covered with hairs.

Myotis lavali has long and silky fur (length of dorsal fur 6.5–7.5 mm). Dorsal fur strongly bicolored, with medium-brown bases (2/3 of total length) and light-brown tips, and ventral fur strongly bicolored with dark-brown hair bases (2/3 of total length) and cinnamon-buff tips ( Moratelli et al. 2011; Novaes 2019). Individuals from the Atlantic Forest may show darker dorsal fur coloration and less contrast between base and tip, which seems to be in accordance with Gloger’s rule ( Moratelli and Wilson 2013).

The skull ( Fig. 3 ) is small to moderate in size, with a longer and upwardly oriented rostrum; postorbital constriction is narrow; forehead is steeply sloping with regard to the skull; supraoccipital region is rounded; occipital projects beyond the posterior limit of the occipital condyles; sagittal and lambdoid crests are generally present and low; and the second upper premolar (P3) is generally aligned with the other premolars and is visible in lateral view.

Ranges of external and skull measurements (mm or g, parenthetical n) for adult males and females combined were (data collected by RLMN, RM, Moratelli et al. 2011): head–body length 72.0–92.5 (56); tail length 31.0–42.0 (56); length of hind foot 5.0–8.0 (56); ear length 11.0–14.0 (56); tragus length 7.0–9.0 (56); forearm length 31.5–37.0 (89); length of 3rd metacarpal 30.6–35.4 (89); length of dorsal fur 7.0–8.0 (44); length of ventral fur 5.0–7.0 (44); body mass 3.0–7.0 (44); greatest length of skull 13.2–14.6 (89); condylocanine length 11.6–12.7 (89); condylobasal length 12.1–13.5 (89); condyloincisive length 12.3–13.7 (89); basal length 10.9–12.2 (89); zygomatic breadth 7.9–8.8 (20); mastoid breadth 6.6–7.2 (89); braincase breadth 6.0–6.7 (89); interorbital breadth 4.0–4.8 (89); postorbital breadth 3.1–3.6 (89); breadth across canines 2.9–3.7 (89); breadth across molars 4.7–5.7 (89); length of maxillary toothrow 4.8–5.4 (89); length of molariform toothrow 2.7–3.1 (89); mandibular length 9.3–10.2 (89); and length of mandibular toothrow 5.1–5.7 (89). There is no secondary sexual dimorphism ( Willig and Hollander 1995; Moratelli et al. 2011).

DISTRIBUTION

Myotis lavali is endemic to South America, occurring from Northeastern Brazil to Paraguay and northern Argentina ( Fig. 4). Its distribution is associated with the South American diagonal of dry formations, with records in Brazilian Caatinga, Cerrado, and Pantanal biomes, Paraguayan Alto Chaco, and Argentinean Yungas ( Moratelli and Wilson 2013; Barquez et al. 2017; Weber et al. 2019). There are peripheral records in the adjacent Brazilian Atlantic Forest ( Moratelli and Wilson 2013; Novaes 2019). Myotis lavali seems to have a strong association with dry open habitats, with marked seasonality and savannah shrub vegetation. Elevational records range from 15 to 900 m, but it appears to be more frequent between approximately 350 and 550 m ( Moratelli and Wilson 2013; Novaes 2019).

FORM AND FUNCTION

Like other Myotis species, the dental formula of Myotis lavali is i 2/3, c 1/1, p 3/3, m 3/3, total 38 ( Miller and Allen 1928; Moratelli et al. 2011). The deciduous dental formula is di 2/3, dc 1/1, dp 2/2, total 22, which is identical to that of most Myotis ( Webster 1981) . Myotis lavali has myotodont molar morphology, similar to its congeners.

A histomorphometry study carried out by Antonio (2015) with specimens from Pernambuco, Brazil (originally identified as M. nigricans ), indicated that M. lavali has small eyes with morphology adapted to a nocturnal environment and a low visual acuity. The cornea occupies approximately 45% of the ocular globe, the choroid is highly pigmented, the ciliary body is developed due to the large lens, which occupies 60% of the volume of the eye; the iris follows the extension of the cornea; the anterior and posterior chambers are large; there is a small vitreous body; retina presents 10 layers, where it has 2,368 ganglion cells/mm 2.

Myotis lavali uses low duty-cycle echolocation ( Fig. 5 ), with broadband calls composed of a downward frequency modulation (FM) followed by a downward quasi-constant frequency (qCF) termination ( Arias-Aguilar et al. 2018). The frequency of maximum energy (FME) is at the fundamental harmonic ( Arias-Aguilar et al. 2018). In the oscillogram, the calls have the maximum amplitude in the middle or near the end, displaying an oval or triangular shape. The frequency of maximum energy averages 51.1 kHz (48–54 kHz), lowest frequency (LF) averages 48 kHz (45–52 kHz), highest frequency (HF) averages 78.3 kHz (67–77 kHz), bandwidth (BW) averages 30.2 kHz (6–67 kHz), call duration (CD) averages 4.8 ms (2–8 ms), interpulse interval averages 77.6 ms (33–201 ms), and the duty-cycle averages 6% (2–11%— Arias-Aguilar et al. 2018; Hintze et al. 2019). There are subtle differences in the frequency of echolocation calls between the populations of the Caatinga and the Atlantic Forest from Northeastern Brazil (1–2 kHz greater in Atlantic Forest).

Myotis lavali is classified into the “Selysius” ecomorph group due to the wing morphology typical of an aerial insectivore, with wings proportionally elongated, narrow, rounded braincase, and short rostrum ( Ghazali et al. 2017). Considering the echolocation calls and wing morphology, M. lavali fits into the guild of aerial insectivores of edge spaces ( Denzinger and Schnitzler 2013).

ONTOGENY AND REPRODUCTION

In the Caatinga of Pernambuco, Northeastern Brazil, Willig (1985a) captured pregnant and lactating females year-round, without evidence of concentration of reproductive activity at any specific time. This pattern suggests that Myotis lavali reproduces year-round, which is in accordance with a reproductive strategy of continuous and unseasonal multimodal polyestry (following Happold and Happold 1990). On the other hand, during the rainy season in Pernambuco, Arandas (2018) found that males of M. lavali showed an increase in number of elongated spermatids, Sertoli cells, Leydig cells, and in plasma testosterone levels, as well as in the tubular, luminal, and epithelial areas of the head and tail of the epididymis.Although males of M. lavali had a continuous spermatogenic cycle throughout the year, the results indicate that there is a greater reproductive investment in the rainy season ( Arandas 2018).

In a more recent study, lactating females were recorded only at the end of the rainy season in the Caatinga of Ceará, Northeastern Brazil ( Feijó and Rocha 2017). Therefore, M. lavali from Brazilian Caatinga may have continuous breeding year-round, but with more concentration of pregnancy or lactation in the rainy season.

Figures

Fig. 1.—Adult male Myotis lavali from Ouricuri, Pernambuco, Brazil. Photograph by RLMN.

Fig. 2.—Head of an adult male of Myotis lavali from Ouricuri, Pernambuco, Brazil, showing the medium-sized ears. Photograph by RLMN.

Fig. 3.—Dorsal, ventral, and lateral views of skull and lateral view of mandible of the holotype of Myotis lavali. The holotype is an adult male (MZUSP [Museum of Zoology of the University of São Paulo] 18762) from near Exu, Pernambuco, Brazil.

Fig. 5.—Echolocation calls of Myotis lavali from the Brazilian Caatinga in the Serra das Confusões National Park, Piauí state. Plots include three pulses printed in oscillogram (A) and spectrogram (B). The gradation of color in the spectrogram pulses indicates the energy of the frequencies, being greater in warm colors.