Abstract

We investigated sound production and the sonic motor system in the Pineconefish, Monocentris japonica. The hand-held Pineconefish produced one type of sound (main frequencies: 100–600 Hz) in both water and air. The sonic organ consists of the swimbladder and a pair of extrinsic sonic muscles originating from exoccipital of the cranium and supracleithrum and inserting on the anterodorsal surface of the swimbladder and partly on vertebrae. The sonic muscle is innervated by occipital nerve branches, not the spinal nerves. Injections of wheat germ agglutinin-conjugated horseradish peroxidase into the sonic muscle resulted in labeled sonic motor neurons ipsilateral to the injections. The labeled neurons were located in the ventral zone of the caudal medulla oblongata, forming a column of sonic motor neurons (or the sonic motor nucleus) from the level of the vagal nerve root to the rostral part of the third ventral root of the occipital nerve. The total number of motor nerve fibers contained in the right and left sonic nerve branches (standard length = 96 mm) were 363 and 369, respectively. We conclude that the sonic muscles of Monocentris japonica are innervated by approximately 700 sonic motor neurons located only in the caudal medulla oblongata.

Abstract

Eurycea sosorum and E. nana are plethodontid salamanders endemic to several karst springs in central Texas. Landscapes around these habitats are increasingly urbanized. At the Barton Springs complex, where E. sosorum occurs, average dissolved oxygen (DO) in the main flow is approximately 6.5 mg L⁻¹. However, DO is quite variable, ranging between 2.4 and 10 mg O₂ L⁻¹, and recent data suggest a positive relationship between DO and spring discharge in Barton Springs Pool, though this relationship may not be as strong under extreme low-flow conditions. Here we examine sensitivity of a surrogate species, E. nana, to experimental variation in oxygen availability (DO); due to limited availability of E. sosorum, they were examined in only a subset of experiments. A suite of traits was measured on adults: spontaneous activity, metabolic rate, and mortality during 28 days of exposure. A separate experiment examined growth of juveniles across levels of DO during 60 days of exposure. Levels of DO below 3.4 mg O₂ L⁻¹ appeared to pose a grave threat to salamander survival over a 28-day study, whereas DO above 4.5 mg O₂ L⁻¹ gave no observable effects in any experiment. Between these values is a critical range in which salamanders became progressively compromised. An ambient water quality criterion for DO in lentic systems (5 mg O₂ L⁻¹, 24 hour minimum) appears adequate to protect Eurycea.

Abstract

In this study, we use restriction fragment length polymorphisms (RFLP) of the mtDNA ND2 gene to identify to species cyprinid eggs collected from a spawning aggregation substrate in the Pascagoula River system. A library was generated with inter- and intra-specific RFLP patterns for nine cyprinids: Notropis baileyi, N. texanus, N. longirostris, N. amplamala, Nocomis leptocephalus, Luxilus chrysocephalus, Lythrurus roseipinnis, and Cyprinella venusta. Eggs of three species were identified from a single nest, while only one species was observed spawning at the site. These results confirm that RFLP is an effective method for identifying unknown eggs of nest associates, and North American cyprinids in general.

NEW NAMES

Acanthopagrus omanensis 123–136

Anarchias

exulatus 421–430

schultzi 421–430

Atractus hoogmoedi 397–402

Bedotia alveyi 284–291

Brachycephalus toby 411–418

Brachymeles lukbani 115–120

Contia longicaudae 254–267

Craugastor evanesco 405–409

Cruriraja hulleyi 364–372

Cyphocharax pinnilepis 382–387

Doumea

reidi 705–715

stilicauda 705–715

Etheostoma

autumnale 716–734

mihileze 716–734

Ischnocnema surda 630–633

Lepidocephalichthys

alkaia 137–159

kranos 137–159

Leptodoras marki 293–298

Loricaria birindellii 274–283

Oryzias woworae 268–273

Otocinclus mangaba 635–638