Aspidytes
| Aspidytes | ||||||||||||
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Aspidytes wrasei |
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| Systematics | ||||||||||||
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| Scientific name of the family | ||||||||||||
| Aspidytidae | ||||||||||||
| Ribera , Beutel , Balke & Vogler , 2002 | ||||||||||||
| Scientific name of the genus | ||||||||||||
| Aspidytes | ||||||||||||
| Ribera , Beutel , Balke & Vogler , 2002 |
Aspidytes is the only genus of the Aspidytidae familywithin the beetle suborder Adephaga . The group was first described in 2002. It includes only two species , Aspidytes niobe , which was discovered in 2001 in the South African province of Western Cape and was first described in 2002, and Aspidytes wrasei, which was discovered in 1995 in the Chinese province of Shaanxi and was first described in 2003.
features
Beetle
The beetles are 4.8 to 7.0 millimeters long and have a dorsally convex, streamlined body. There is no angle between the pronotum and the wings , so the transition is even. Both the shiny body and the body appendages are colored red-brown to black. The mouthparts on the head are directed forward. They are significantly shortened and, viewed from the side, wedge-shaped. The back of the head is clearly retracted into the prothorax but does not have a tapered neck area. The frontal plate ( clypeus ) is clearly narrowed towards the labrum . The frontoclypeal suture is interrupted in the middle (median). The clypeolabral suture is almost straight. The labrum is inclined and has a wide median cavity. The antennae show neither pubescence nor longer setae . You turn in to the side in front of the compound eyes . The deflections are not visible from above. The scapus has a spherical base and a similar distal area, the two areas being separated by a distinct incision. The rear (distal) part of the scapus largely encloses the small pedicellus . The maxillae are turned into a maxillary pit between the submentum and mentum and the compound eyes. The two-part galea is palpus-shaped . The maxillary palps are five-limbed, fairly short and barely overlap the labial palps .
The pronotum is evenly rounded on the sides. The curved edge widens significantly at the front. At the back of the pronotum there is a row of dense hairs. The prosternal process is well developed and is rounded in Aspidytes wrasei , in Aspidytes niobe it is truncated and has rounded edges on the front. The indentations of the front hips ( coxes ) are open, their inner bridge is sclerotized and reddish. The front legs are quite short. Your hips are spherical, with a short ventral condyle, the thighs ( femora ) have a series of short stiff hairs on the front edge, which are used for grooming. The splints ( tibia ) have a truncated front end (apex) and two strong end spurs; the outer one is a little stronger. The first four tarsal links are short, the fifth is about 2.5 times longer than the remaining links. In the males, the first two tarsi members of the fore and middle legs are slightly enlarged on the sides and covered with innumerable adhesive hairs on the underside, which have tiny discs at their tips. The mesothorax is slightly shorter than the prothorax . The label ( scutellum ) is exposed. The cover wings (elytres) have a ledge on the side that extends to the tip. The indentations on the hips of the middle legs are laterally bordered by the inner (mesal) edge of the epimeron and the narrow, front (apical) part of the anepisternum (a sclerotized shield on the ventral side) of the metathorax. The middle legs are similar to the front ones, only the thighs have no hairs or spurs and the rails and tarsi are slightly longer. The rails are only slightly extended at the front. The metathorax is slightly longer than the prothorax. The hips of the hind legs are moderately elongated and slightly longer than the ventrit . The lateral margin is broadly adjacent to the epipleural margin (the folded side edge of the elytra). The thigh rings ( trochanters ) of the rear legs are longer than those of the rest. The rails and tarsi are longer than those of the middle legs and appear thin and elongated.
Six abdominal shields (sternites or ventrites) are visible on the abdomen, their length decreases from the third to the sixth. The second sternite can only be seen on the side of the rear hips. The third and fourth sternite are partially fused, but have a very clear seam between them. A bar runs along the sides of each sternite, which is most noticeable on the edge of the seventh sternite. This sternite is approximately semicircular, evenly rounded at the back and has no changes on the surface or on the rear edge.
Larvae
So far only the larvae of Aspidytes niobe are known. When fully grown, they reach a length of about seven millimeters without Urogomphi . Its body is very broad and flattened at the front, but the abdomen is almost cylindrical in cross-section towards the ninth, last segment. The body surface is smooth, with the sclerites having short, medium-length bristles (setae). The head and also the body are strongly pigmented dorsally.
The mouthparts on the head are directed forward, the head is very slightly angled. It is moderately flattened, slightly wider than it is long and significantly narrower than the prothorax. It has the greatest width in the rear third, where it is about a millimeter wide. The back of the head is retracted into the prothorax but does not form a tapered neck area. Six larvae eyes ( stemmata ) are arranged almost in a circle behind the antennae deflections. The labrum is fused with the frontoclypeus. The antennae are four-part. The mandibles are moderately long and have a fairly basal part and a notch in the middle, adjoined by two cutting edges, one of which is serrated. The maxillae are articulated at the anterior, lower (anteroventral) edge of the head capsule. The two-part galea is palpus-shaped, the lacinia is absent. The maxillary palps are tripartite, the labial palps bipartite.
The prothorax is the largest segment of the body and has a shiny and smooth surface with numerous short setae growing from small pores and longer setae growing along the lateral and anterior edges of the anterior collar. The pronotum is shield-shaped and rounded in the front and on the sides. It has a clear bar on the side edge. The first abdominal segment is about half the length of the metathorax. The small spiracles are on the sides of the tergites . There are two clear oblique grooves on the sterna. The tergites of the second to eighth abdominal segments are laterally fused with the sternites and thus form a ring-shaped structure. The second to fifth abdominal segments are significantly longer than the first and about the same width. The sixth and seventh segments are shorter. The sixth is narrower than the fifth, the seventh narrower than the sixth. The seventh is about the same length as the fifth and tapers at the back. The urogomphi, which are turned in on the back of the eighth abdominal segment on the underside (ventrolateral), are strongly developed. They enclose the small, but clearly developed, ninth segment of the abdomen, which therefore cannot be seen from the side. The basal segment of the urogomphi is about one and a half times longer than the eighth abdominal segment. The Urogomphi each have wide bases that almost border each other in the lower middle. They taper evenly towards the tip and carry several long setae. The posterior (distal) segment is very slender and cylindrical in cross section. It is just over half the length of the basal segment. There are long setae at the top.
Both the pupa and the eggs are unknown.
Way of life and habitat
The adults of both species and the larvae of Aspidytes niobe live in hygropetric habitats and are very likely to be predatory, although no evidence has yet been found. Aspidytes niobe is known from two neighboring sites in the western Cape Province ( South Africa ), where seepage water continuously runs over open, almost bare and almost vertical rock. The areas around the seepage water are densely and species-richly overgrown. The animals were found from spring to late summer, i.e. from September to March. The larvae could not be found in late summer (March) but were common in September. The adults were found resting on the stone surfaces. They ran very quickly when there was a fault. The larvae of this species actively crawled on the open but heavily shaded rock. Aspidytes wrasei is only known from a single site (in Shaanxi , China) that lies at the base of a vertical hygropetric surface. The animals were found there between stones and various plants. The animals were found in late summer (August).
Taxonomy and systematics
Both morphological and molecular genetic studies suggest that the group belongs to a clade that also includes the damp beetles (Hygrobiidae), trout brook beetles (Amphizoidae) and swimming beetles (Dytiscidae). Typical features of this are the extensive amalgamation of the middle walls of the rear hips, the loss of two of the three furcocoxal muscles on the metathorax, and the loss of the tenth abdomen segment in the larvae. A less strongly derived characteristic compared to the related groups is the incomplete regression of the ninth abdominal segment of the larvae. The phylogenetic relationship within the clade described above has practically not yet been researched. The most extensive analysis to date based on morphological and molecular genetic features by Balke et al. from 2005 assumes that the group has a sister relationship to the trout brook beetles, although the data support this only slightly.
supporting documents
Individual evidence
- ↑ a b c d e f g h i j k Richard AB Leschen, Rolf G. Beutel, John F. Lawrence: Handbuch der Zoologie - Coleoptera, Beetles, Volume 2: Morphology and Systematics (Elateroidea, Bostrichiformia, Cucujiformia partim) . de Gruyter, 2010, ISBN 978-3-11-019075-5 , p. 21st ff . (English).
- ↑ a b c Aspidytes. Tree of Life webproject, accessed February 3, 2013 .
- ↑ M. Balke, I.Ribera, RG bag (2005): The systematic position of Aspidytidae, the diversification of Dytiscoidea (Coleoptera, Adephaga) and the phylogenetic signal of third codon positions. Journal of Zoological Systematics and Evolutionary Research Volume 43, Issue 3: 223-242. doi : 10.1111 / j.1439-0469.2005.00318.x
literature
- Richard AB Leschen, Rolf G. Beutel, John F. Lawrence: Handbuch der Zoologie - Coleoptera, Beetles, Volume 2: Morphology and Systematics (Elateroidea, Bostrichiformia, Cucujiformia partim) . de Gruyter, 2010, ISBN 978-3-11-019075-5 (English).
- I. Ribera, RG Beutel, M. Balke, AP Vogler: Discovery of Aspidytidae, a new family of aquatic Coleoptera . In: Proceedings of the Royal Society of London Series B-Biological Sciences. Vol. 269, 2002, pp. 2351-2356. doi : 10.1098 / rspb.2002.2157