C. 'tyleri' Immatures

  formerly Chironomus oppositus f. tyleri - Martin & Lee 1984

Larva:  medium sized larvae (female 13.8 - 16.2; male 11.2 - 16.5 mm), generally of bathophilus-type, but showing some degree of development of the lateral projections (less than 200 µm).   Anterior ventral tubules with an ‘elbow bend’, sometimes slightly longer than the slightly curved posterior pair, but in general about the same length (ant. 0.56 - 2.97; post. 0.58 - 2.97 mm).
Anal tubules about equal in length, from 230-480 µm long and generally 2-3.5 times longer than wide.  Longer hooks of anterior parapods without hooks.
Gular region slightly dark or dark over posterior half, some degree of darkening of the frontoclypeus.
Mentum (Fig. d) with 4th laterals slightly reduced (type I-II), c2 teeth usually well developed, c1 relatively narrow (type (IIA-III).
Ventromental plates (Fig. e) with smooth anterior edge, inner edges separated by about 0.28 (0.27 - 0.28) of the width of the mentum; 36 - 46 striae on each plate; VMR about 0.32-0.33.  Pecten epipharyngis (Fig. a) with 11-17 teeth, which are sharp (type B) when not worn down and appear as type C.
Premandible (Fig. b) with teeth about equal in length, inner tooth at least 1.5 (up to 2.3) times as wide as the outer tooth.Basal segment of antenna (Fig. c) about 3.0 - 3.7 times as long as wide, RO from about a quarter to half way up the segment; AR about 1.92-2.55; A2/A1 about 0.18-0.23; relative length of the segments (µm) 148 : 34 : 10 : 13 : 7.
Distance between the antennal bases greater than that between the S4 setae, which are just before the widest part of the frontoclypeus.
Mandible (Fig. f) 251-280 µm in length (tip to heel), with third inner tooth only partly separated and coloured (type IIB).  About 12-17 furrows near the base; about 13 bristles in Pecten mandibularis.

Cytology:  4 polytene chromosomes with the pseudothummi arm combination AE, BF, CD, G.
Arm G with subterminal nucleolus and closely applied sequences of BR4, further BR about 15 bands away, and generally unpaired at the distal end.  Nucleolus in arm F at about group 19.
Basic sequences similar to those seen in other members of the C. oppositus-group, but has some unique sequences polymorphic in some arms, particularly in Tasmania and the Bass Strait island populations.  Polymorphic in all arms; that in arm G often sex-linked. The most common sequences were: A1 and A2; B1; C3 and C1; D4; E1; F1 and F2; G1 and G2 (Martin 2011a).  The most characteristic sequences are D4 and E1.
Rare sequences, particularly E2, probably resulting from hybridization with forms of C. oppositus.  Similarly, low frequencies of E1, D4 and G1 carrying the MD gene in other forms also result from hydbridization.
Rates of natural hybridization between forms ranges from 0.3% to 1.6%.  The latter value is between C. tyleri and form connori, and is possibly due to most of the egg masses being from Bellerive, Tasmania, the only locality where the two forms were found togther and both were present in high frequency.
tylA1:    1a-e, 7 - 4, 12a-c, 3i-f, 9 - 8, 11 - 10, 2c - 1f, 3e - 2d, 13 - 19                                                                  as oppA1
tylA2:    1a-e, 7 - 4, 12a-c, 3i-f, 9 - 8, 2d - 3e, 1f - 2c, 10 - 11, 13 - 19                                                                  as oppA2
tylB1:    Puff with proximal dark bands (groups 7 and 8) near middle of arm                                              as oppB1 (common)
tylB2:    Puff with distal dark bands (groups 8 and 7) towards distal end of the arm                                            as oppB2, less common
tylC1:    Typical groups, 3-4, about one third from distal end                                                                                as oppC1
tylC2:    Inversion of most of the arm, taking groups 3-4 to a proximal location                                                      as oppC2, occasional
tylC3:    A small distal inversion of C1, with one break in groups 3-4                                                      as oppC3 (most common)
tylD1:    1 - 2, 16 - 13, 9a-e, 3d-a, 10d - 12, 18 - 17,10c-a, 3e - 8, 19 - 24                                                          as oppD1, (occasional)
tylD2:    1 - 2, 16 - 14h, 19c-a, 8 - 3e, 10a-c, 17 - 18, 12 - 10d, 3a-d, 9e-a, 13 - 14g, 19d - 24                        as oppD4 (common)
tylD3:    1 - 2, 18e - 17, 10c-a, 3e - 8, 19a-c, 14h - 16, 18fg, 12 - 10d, 3a-d, 9e-a, 13 - 14g, 19d - 24    (was oppD5 but not known in oppositus forms), occasional
    OR    1 - 2f, 17f-a, 10c-a, 3e - 8, 19a-c, 14h - 16, 2i-g, 18a-g, 12 - 10d, 3a-d, 9e-a, 13 - 14g, 19d - 24          (i.e. intermediate to tepD1)
tylE1:    1 - 3e, 10b - 3f, 10c - 13                                                                                                                        as halophilus, oppE1, etc.
tylE2:    1 - 2d, 7g - 10b, 3e -2e, 7f - 3f, 10c - 13                                                                                                  as oppE2 (occasional)
tylF1:    1 - 2a, 10 - 2b, 11 - 23                                                                                                                              as oppF1
tylF2:    1 - 2a, 10 - 6c, 15g-11, 2b - 6b, 15d - 23                                                                                                  as oppF2
tylG1:    subterminal nucleolus and nearby BR (possibly BR2), small BR near distal end.                                   as oppG1
tylG2:    inversion of about middle half of the arm, i.e. between the two BRs (often sex-linked)                          as oppG2

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Modified: 19 April 2020
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