Metriocnemus, Van der Wulp, 1874

Namayandeh, Armin, Hudson, Patrick L., Bogan, Daniel L. & Hudson, John P., 2024, Chironomidae (Diptera: Insecta) of Alaska, USA, with descriptions of new species and a checklist, Zootaxa 5511 (1), pp. 1-95 : 63-64

Metriocnemus v. d. Wulp, 1874

Here, we provide records of seven species of Metriocnemus occurring in Alaska. Metriocnemus eurynotus (Holmgren, 1883) was reported from Western Alaska as M. obscuripes by Saether (1995) and by Watson et al. (1966). Larvae identified in the Metriocnemus eurynotus group have been collected in streams and lakes along the Arctic Coastal Plain (AWQMS 2005) and on St. Matthew Island ( Sikes et al. 2016).

We collected a male Metriocnemus edwardsi Jones, 1916 in the Juneau area at the outlet of Eagle River, the Jensen-Olsen Arboretum, and the outlet of Peterson Creek on the mainland in mid-August. We have also collected male specimens from a tributary of Margaret Creek on Revillagigedo Island in early May. This is a new faunistic record for Alaska .

Metriocnemus fuscipes (Meigen, 1818) is a new record for Alaska. We collected adult males of M. fuscipes from a forested bog on Douglas Island in mid-July and from floodplain pools near the mouth of Eagle River in mid-August near Juneau. We also collected a single adult male of M. fuscipes in a drift sample from a Margaret Creek tributary on Revillagigedo Island. We collected larvae of M. fuscipes in the Chilkat River in Southeast Alaska and a small tributary to Six Mile Lake near Nondalton. The larvae of this species are found in damp soil adjacent to and in springs and small streams and inhabit hygropetric habitats ( Oliver & Dillon 1997). M. fuscipes is a common circumpolar species.

A larva of Metriocnemus intergerivus Saether, 1995 was found in the stomach of an Alaskan blackfish, Dallia pectoralis Bean, 1880 collected from a pond in a minnow trap baited with eggs on the Kenai Peninsula ( Arctos 2023). The identification of Metriocnemus was based on molecular data.

The record of Metriocnemus longipennis (Holmgren, 1883) in Alaska comes from a collection from Point Barrow found in the British Museum of Natural History and identified by P. Freeman as Dolichoprymna longipennis ( Saether 1989) . Saether (1989) noted several morphological characteristics unique to this species as adaptations for copulating on the ground rather than in the air. We collected four adult males of Metriocnemus shouclarus Sasa, 1989 in mid-June near Hanus Bay on Catherine Island. This is a new faunistic record for the Nearctic ( Fig. 10 O- P).

The collection of Metriocnemus yaquina Cranston & Judd, 1987 is a new record for Alaska. The species has a peculiar life history. All three life stages of this species were described by Cranston & Judd (1987) from material collected in rock pools along the Oregon coast. These pools were at or slightly above the high tide level but within the splash zone. We found our material in similar habitats along the shoreline and on islands along Favorite Channel in the Juneau area, and in tide pools in Anderson Bay on Unalaska Island and near Lena Point in Juneau ( Fig. 9S ). A rock pool containing M. yaquina near Lena Point fills with freshwater runoff during low tides and is covered with saltwater during many high tides each month. Cranston and Judd (1987) found both the larvae and pupae free-living in pools that contained abundant algae and periphyton, as we did. They also noted that these pools were subject to drying out. Nothing is known about the relative contribution of rainwater, freshwater runoff, and saltwater intrusions associated with storms and tides to these intertidal pools. It would be informative to know how the salinity of these pools changes over time.

Watson et al. (1966) reported on two undescribed species of Metriocnemus from Northwest Alaska. There are also several specimens of undetermined Metriocnemus from the Kenai Peninsula that have been DNA barcoded, and their sequences are available in Bold ( Bowser et al. 2020). Additional records of Metriocnemus includes at least two species of larvae collected from ponds in the Point Barrow area by Butler et al. (1980) and Lougheed et al. (2011). These specimens were collected in emergence traps at the edge of the ponds in Carex beds suggesting a semi-terrestrial habitat. Lesage et al. (2005) found Metriocnemus larvae in woody debris along the shoreline of several streams in the Maybeso Experimental Forest on Prince of Wale Island.

The above observations support the conclusion of Cranston & Judd (1987) that species in the genus Metriocnemus exhibit one of the broadest scopes of larval habitats, ranging from the margins of running and standing freshwater, and possibly some saline conditions in rock pools along marine shorelines. They have also been found in plant-held water, films of thin water, and apparently fully terrestrial habitats.

Figures

FIGURE 9. Some of the study’s collection sites and habitats of Chironomidae in Alaska. A. Turner Lake, near Juneau. B. Bartlett River in Glacier Bay National Park and Preserve. C. Alaska, USA and Yukon Territory, Canada international boundary. D. Auke Lake outlet in Juneau. E. Rachael Lake near Bettles. F. Spike Creek on Revillagigedo Island. G. Auke Lake in Juneau. H. Hebert River near Juneau. I. Nugget Falls, in Juneau. J. Forested bog near Eagle crest Ski Area, Douglas Isand. K. Creek outlet at Margaret Bay on Revillagigedo Island. L. Mount Roberts (foreground) in Juneau. M. A snow-melt stream (arrows) on Thunder Mountain, Juneau. N. Tangle River near Paxon. O. Kanuti Lake outlet in Kanuti National Wildlife Refuge. P. Fish Creek on Douglas Island. Q. Antler River near Juneau. R. Harbor Mountain, Sitka. S. Observing Thalassosmittia marina (Saunders, 1928) larvae in intertidal rock pools near Lena Point, Juneau. T. Larvae of T. marina (arrows) inhabiting a rock pool in the upper tidal zone and feeding on periphytic algae near Lena Point, Juneau. U.A tundra lake east of King Salmon. V. Swarm of Corynocera oliveri group adults on a tundra lake east of King Salmon.

FIGURE 10. The new Nearctic faunistic records of Alaskan Chironomidae I. Lappodiamesa vidua (Kieffer, 1922) larva (A– C); Acamptocladius submontanus (Edwards, 1932) male (D); Cricotopus (Paratrichocladius) scaturigineus (Makarchenko & Makarchenko, 2014) male, pupa, larva (E–F); Eukiefferiella clypeata Kieffer, 1922 male, pupa (H–J); Eukiefferiella gracei (Edwards, 1929) male, pupa (K–M); Heleniella ornaticollis (Edwards, 1929) male (N); Metriocnemus shoulcarus Sasa, 1989 male (O–P). Paracladius omolonus Makarchenko & Makarchenko, 2006 (Q). Parakiefferiella rara Makarchenko & Makarchenko, 2007 male, pupa (R–S). A. Mentum. B. premandible. C. procercus. D. hypopygium. E. hypopygium. F. tergites II–V. G. mandibles, mentum, labrum. H. hypopygium. I. tergites II–V. J. thoracic horn. K. hypopygium. L. tergites II–V. M. thoracic horn. N. hypopygium. O. antenna. P. hypopygium. Q. hypopygium. R. hypopygium. S. tergites VI–IX. Scale bars are 50 µm.